Current evidence and emerging approaches in immunotherapy for gynecological cancers.

The tumour microenvironment (TME), also called the tumour immune microenvironment (TIME), plays a central role in the progression or remission of cancer as it has the potential to shift the immune system from an anti-tumour state to a pro-tumour one [ 132 ]. The heterogeneity of the TME also determines the response rates of gynecological cancers (ovarian, cervical, vulvar, vaginal, and endometrial) to different immunotherapies [ 253 ]. The TME is composed of endothelial cells, chemokines, extracellular matrix (ECM), metalloproteinases (MMP), cytokines, cancer-associated fibroblasts (CAF), antibodies, tumour-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), different growth factors, and so on [ 161 ]. Therapeutic strategies targeting various components of the TME form the foundation of immunotherapy and have shown positive results in experimental studies and clinical trials [ 205 , 238 ]. In cervical cancer, which is usually HPV-driven, there is a relatively higher T-cell infiltration in the TME and expression of PD-L1 due to viral neoantigens [ 117 ]. Compared to CxCa, ovarian cancer has lower T-cell infiltration and is dominated by immunosuppressive cells and ascites in advanced stages [ 253 ], while endometrial cancer TME ranges from microsatellite instability (MSI-H) “hot” tumours–responsive to ICIs–to microsatellite-stable “cold” tumours [ 132 ]. A key characteristic in all gynecological cancers is hypoxia-driven angiogenesis via the secretion of VEGF [ 88 ]. There is little research on the TME of vulvar cancer, as well as vaginal cancer. These cancer types are relatively rare gynecologic cancers, with an annual incidence of 1–2 per 100,000 women [ 1 ]. Progression of vulvar and vaginal cancers is characterised by an increase in activated M2 macrophages (CD14 + CD33- CD163+), Tregs, and a decrease in CD8 T cells in the TME. DCs and Langerhans cells (LCs), which present antigens on their cell surface, also show decreased infiltration [ 218 ]. Mutation of TP53 is the leading cause of about 80% of vulvar squamous cell carcinoma (VSCC) and arises from vulvar intraepithelium, usually influenced by lichen sclerosus [ 132 ]. Unlike vulvar and vaginal cancers, ovarian cancers have been well-studied. Macrophages in the tumour cells, called tumour-associated macrophages (TAM), can have two phenotypic expressions. The M1 phenotype stimulates the release of cytokines, such as CXCL12, IL-1, IL-12, and TNFα. M1 TAMs also have cytotoxic activity, can suppress tumour growth, and stimulate the immune system [ 196 ]. The M2 TAM produces IL-4, IL-10, and IL-13, all of which can suppress the immune system and promote tumour growth [ 217 ]. Therefore, higher M1/M2 ratios are important markers that can help predict overall survival (OS) [ 242 ]. TAMs can be targeted via their receptor, CSF-1R (colony-stimulating factor-1 receptor). Inhibition of CSF-1R can reduce the proliferation of ovarian cancer by modulating M2 macrophage infiltration, as shown in mouse studies [ 241 ]. Furthermore, the study by Lu and Meng [ 121 ] showed that CSF-1R inhibition depletes ascites accumulation, as well as M2 macrophage infiltration. Neutrophils in the TME can also express phenotypes with different functions. The N1 phenotypic expression has anti-tumour activities, while the N2 type is pro-tumour in nature [ 69 ]. The N2 expression might facilitate immune suppression via the upregulation of PD-L1 and T-cell downregulation [ 6 , 168 ]. Although immunotherapy based on neutrophils is yet to be extensively researched, research by Chen et al. [ 33 ] showed that a lower neutrophil to lymphocyte ratio can improve overall survival ( p = 0.005; hazard ratio (HR) 1.4; 95% confidence interval (CI) 1.11–1.79). Other cells in the TME, such as DCs and NK cells, contribute to treatment outcomes in ovarian cancer. The DCs present antigens to T-cells and stimulate their proliferation and anti-tumour activity. Dendritic cells are associated with improved overall survival as seen in two cohort studies [ 211 ]. NK cells are also associated with longer OS (29–45 months) in a study involving patients with high-grade serous ovarian cancer (HGSOC) [ 80 ]. Furthermore, in the ovarian TME, TGF-β released by lymphatic endothelial cells, mesothelial cells, and fibroblasts was associated with positive outcomes, whereas plasma cells were associated with negative outcomes [ 157 ]. The challenge of immunotherapy’s efficacy in ovarian cancer is due to its complex pathway and metabolism [ 132 ]. As with ovarian cancer, the TME of endometrial cancer features the innate and adaptive immune system contributing to tumourigenesis. The density of TAMs in the TME is associated with the progression of solid tumours; however, this is not well understood in endometrial cancer [ 56 ]. Studies note that as much as 75% of endometrial cancer cases overexpress PD1, while 25%−100% of cases overexpress PD-L1 [ 82 , 220 ]. Owing to this, the PD1/PD-L1 inhibitors can halt the progression of tumourigenesis. Pembrolizumab, in a phase Ib multi-cohort trial, KEYNOTE-028 ( NCT02054806 ), was administered as monotherapy, and of the 24 endometrial cancer patients, four patients achieved PR (95% CI, 2.8–33.6%). Although ORR was 13%, median OS was not reached [ 159 ]. In another clinical trial (phase II; KEYNOTE-158; NCT02628067 ) using pembrolizumab, ORR was 48% and median PFS was 13.1 months (95% CI, 4.3–34.4 months), although median OS was also not reached [ 154 ]. In contrast, pembrolizumab in combination with lenvatinib, a tyrosine kinase inhibitor, was able to reach a median OS in 16.4 months in MSI-S patients (95% CI, 13.5–25.9 months), with 36.2% ORR (95% CI, 26.5–46.7%) and disease control rate of 84% (95% CI, 75–90.8%). Although median OS was not reached in MSI-H patients [ 130 ]. As earlier noted, a large percentage of cervical cancer is a result of infection with high-risk strains of HPV, HPV 16 and 18. These high-risk strains release the oncoproteins E5, E6, and E7, which mediate immune evasion and confer immortality to the cell by inhibiting the actions of p53 and Rb [ 117 ]. While cytotoxic T cells (CD8+) are necessary to facilitate direct killing of intracellular pathogens, a variety of immune cell types are needed for a sustained therapeutic response [ 132 ]. Targeting the PD-L1/PD-1 pathway seems reasonable for cervical cancers since the oncogenes released by HPV activate pathways that lead to the expression of PD-L1 and PD-1, which will, in turn, suppress the adaptive immune response. DCs, TILs, and tumour cells all express PD-L1, making this cancer type easily targetable by PD-L1/PD-1 inhibitors such as pembrolizumab [ 141 , 173 ]. The T-cell surface receptor, CTLA-4, is also being researched as an immune checkpoint. CTLA-4 inhibitors block the binding of CD80 and CD86 to CTLA-4 on Tregs to activate the immune system [ 22 ]. Currently, ipilimumab, which is a CTLA-4 inhibitor, has been used as monotherapy and in combination with PD-1/PD-L1 blockers (such as nivolumab) in the treatment of recurrent cervical cancer (CheckMate 358 trial; NCT02488759 ) [ 153 ]. In the TIME, TGF-β contributes to immune evasion and promotes tumourigenesis [ 10 , 95 , 204 , 229 ]. TGF-β is produced by CAFs, myeloid-derived suppressor cells (MDSC), and type-2 TAMs. It can suppress the function of CTL, promote the recruitment of M2 TAMs, block M1 TAMs activation, and suppress the activation and proliferation of immune cells [ 248 ]. Disruption of TGF-β, however, promotes T-cell- and NK cell-mediated anti-tumour response [ 225 ]. Inhibition of TGF-β can therefore potentially potentiate the activity of other immunotherapeutics. In a phase II study to evaluate the combined effects of galunisertib, a TGF-β1 receptor type I Inhibitor, and sorafenib. The combination showed a prolonged OS outcome with a median OS of 18.8 months in patients with advanced hepatocellular carcinoma [ 97 ] (Fig. 5 ). Fig. 5 Tumor microenvironment in gynecological cancer Tumor microenvironment in gynecological cancer

Immune checkpoints are modulatory pathways that regulate innate and adaptive immune responses. They are important in health and diseases, as they maintain homeostasis [ 139 ]. In addition to the tumor cells, immune cells are recruited to the tumor microenvironment, immune response to the tumor, as well as resolution of perturbation and homeostasis, are sheer results of the competition between these stimulator and inhibitory immune signals; stimulatory signals favor T cell activation and responses, while inhibitory effectors do otherwise [ 119 ]. Cancer and tumors, however, remain a challenge as malignant cells interfere with anti-tumour immune responses via the expression of immune checkpoint proteins, thereby aiding the growth of tumor cells. Programmed Death-1 (PD-1) and Programmed Death-Ligand 1 (PD-L1) are immune checkpoints that tumor cells exploit to prevent immune recognition. Moreso is Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4), which targets antigen presentation, thereby reducing T cell activation [ 77 ]. CTLA-4 is a key immunological checkpoint expressed on activated T cells and also on T regulatory cells (Tregs); it regulates T-cell proliferation and inhibits excessive activation. CTL4 and CD28 are homologous and are located close to each other on chromosome 2q33. They have an affinity for the identical ligands, but CTLA-4 has a higher affinity than CD28. Thus, CTLA-4 binds to CD80/CD86 and prevents CD28 binding, thus suppressing T cell activation. In the absence of CTLA-4, excessive T-cell proliferation was reported; this aroused interest in checking if CTLA-4 inhibition could aid immune responses to tumor growth [ 7 ]. PD-1 is a transmembrane protein of 288 amino acids that belongs to the CD28/CTLA-4 family of T cell regulators. Its ligand binding domains (PD-L1 (B7-H1) and PD-L2 (B7-DC) are expressed on antigen-presenting cells and other immune cells identified in the tumor microenvironment. PD-1 binding to the ligand activates a signaling cascade leading to TCR signaling inhibition that results in T cell and cytokine suppression. PD-1 blockers, including Pembrolizumab (Keytruda), cemiplimab (Libtayo), Toripalimab (Tuoyi), Nivolumab (Opdivo), and Tislelizumab (BGB-A317), target PD-1-ligand interaction, enhancing T cell activities against tumor cells [ 7 , 158 ]. Another immune regulatory protein is Lymphocyte-activation gene 3 (LAG-3). It is expressed in several immune cells, such as T cells, natural killer (NK) cells, regulatory T cells, dendritic cells, and activated B cells. By binding to its receptor, LAG-3 helps maintain homeostasis and prevents excessive immune responses that may cause autoimmune diseases. Although the exact signaling pathway that is activated by LAG-3 is not fully understood, this protein shares a structural resemblance with CD4, thus competing with CD4/MHC-II interactions, suppressing the proliferation, activation, cytotoxicity, and cytokine production of CD4 + and CD8 + T lymphocytes [ 7 , 35 ]. Immune checkpoint proteins include B7 homolog three protein (B7-H3), also called CD276, hepatitis A virus cellular receptor 2 (HAVCR2), TIGIT, also referred to as V-set and Immunoglobulin Domain Containing 3 (Vstm3), Wilms’ Tumor 1 Upregulated on T Cells (WUCAM), and V-set and Immunoglobulin Domain Containing 9 (VSIG9), CD47-SIRPα axis, CD47-SIRPα axis, and Adenosine A2A receptor (ADORA2A). CD96, also known as TACTILE, is a member of the immunoglobulin superfamily (IgSF), while SIGLEC-15 is an immunological checkpoint protein from the sialic acid-binding immunoglobulin-like lectin (SIGLEC) family. In cancer, tumor cells frequently use LAG-3 to avoid immune detection, making it an appealing target for therapeutic intervention [ 7 , 109 ]. Although traditional methods like radiotherapy and chemotherapy are the core of cancer management, immune-based therapies have reportedly revolutionized cancer treatment. Immune checkpoint inhibitors (ICIs) are approved immunotherapy drugs used for cancer treatment; they enhance the tumor-targeting ability of the immune system. The discovery of immune checkpoint molecules in the 1980 s led to the discovery of their T cell-inhibitory functions, which enhance the anti-tumor functions of the immune system. This led to the development of the first Cytotoxic T-lymphocyte Antigen-4 CTLA-4)- blocking drug, ipilimumab, for the management of melanoma, which recorded some success. Following this, Programmed Death-Ligand 1 PD-1 was discovered, and thereafter its inhibitor, nivolumab. Subsequently, other ICIs like pembrolizumab, durvalumab, atezolizumab, and avelumab have been adopted for various cancer treatments [ 167 , 197 ]. ICIs have recorded a 20–40% success rate over the years [ 84 ]. Table 1 shows ongoing immunotherapy trials in gynecologic malignancies, while Table 2 shows the effect of major immunotherapy approaches on various gynecological cancers. Table 1 Ongoing immunotherapy trials in gynecologic malignancies Trial Study population Phase Intervention Primary outcome Status Ovary NCT02580058  JAVELIN  Ovarian 200 Platinum-resistant/refractory EOC III Arm 1: Avelumab Arm 2: avelumab + Doxil Arm 3: Doxil OS; PFS Recruiting NCT02839707 Platinum-resistant EOC II/III Arm 1: Doxil + atezolizumab Arm 2: Doxil + atezolizumab + bevacizumab Arm 3: Doxil + bevacizumab DLTs, PFS Recruiting NCT02440425 Platinum-resistant EOC II Weekly paclitaxel + pembrolizumab PFS; AEs Recruiting NCT02608684  PemCiGem Platinum-resistant EOC II Gemcitabine + cisplatin + pembrolizumab ORR Recruiting NCT02891824  ATALANTE Recurrent platinum-sensitive EOC III Arm 1: placebo + bevacizumab + platinum chemo Arm 2: atezolizumab + bevacizumab + platinum chemo PFS Recruiting NCT01928394  CheckMate  032 Advanced or metastatic solid tumors I/II Arm 1: nivolumab Arm 2: nivolumab + ipilimumab Arm 3: nivolumab + ipilimumab + cobimetinib ORR Recruiting NCT02498600 Recurrent or persistent EOC II Arm 1: nivolumab + nivolumab maintenance Arm 2: nivolumab + ipilimumab + nivolumab maintenance ORR Recruiting NCT03026062 Platinum-resistant and platinum refractory EOC II Arm 1: sequential tremelimumabfollowedby durvalumab Arm 2: combination tremelimumab + durvalumab irPFS Recruiting NCT02726997 Advanced EOC with no prior treatment I/II Carboplatin + paclitaxel + durvalumab Pharmacodynamics changes Recruiting NCT02520154 Advanced EOC with no prior treatment II Neoadjuvant carboplatin + paclitaxel followed by interval TRS and adjuvant carboplatin + paclitaxel + pembrolizumab PFS Recruiting NCT02834975 Advanced EOC with no prior treatment II Neoadjuvant pembrolizumab + carboplatin + paclitaxel following by interval TRS and adjuvant pembrolizumab + carboplatin + paclitaxel ORR Recruiting NCT03038100  IMagyn050 EOC with no prior treatment III Arm 1: carboplatin + paclitaxel + bevacizumab + atezolizumab Arm 2: carboplatin + paclitaxel + bevacizumab + placebo PFS; OS Recruiting NCT02718417  JAVELIN  OVARIAN  100 Advanced EOC with no prior treatment III Arm 1: carboplatin + paclitaxel Arm 2: carboplatin + paclitaxel + avelumab maintenance Arm 3: carboplatin + paclitaxel + avelumab + avelumab maintanence PFS Recruiting Cervix NCT02628067  KEYNOTE  158 Advanced solid tumors II Pembrolizumab ORR Recruiting NCT02488759  CheckMate  358 Squamous cell carcinomas of the cervix, vulva, and vagina plus other virus-associated malignancies I/II Arm 1: neoadjuvant/metastatic nivolumab Arm 2: nivolumab + ipililumab Arm 3: nivolumab + BMS-986,016 Arm 4: nivolumab + daratumumab Safety and tolerability; ORR; rate of surgery delay Recruiting NCT01711515 Advanced cervical cancer stage IB-IIB with positive PA nodes only and stage IIB/IIIB/IVA with positive nodes I Primary chemoradiation followed by ipilumumab DLTs Active, not recruiting NCT02635360 Locally advanced cervical cancer Arm 1: chemoradiation followed by pembrolizumab Arm 2: chemoradiation with concurrent pembrolizumab Immune markers; DTLs Recruiting NCT02866006 Metastatic, progressive, or recurrent HPV 16/18 cervical cancer after failed standard therapy I BVAC-C vaccine DTLs, AEs Recruiting NCT02128126 Advanced, metastatic, or recurrent cervical cancer and HPV16positive I/II ISA101/ISA101b vaccine HPV-specific immune response Recruiting Uterus NCT02549209 Stage III/IV or recurrent endometrial cancer II Carboplatin + paclitaxel + pembrolizumab ORR Not yet recruiting NCT02899793 Recurrent endometrial cancer II Pembrolizumab ORR; AEs Recruiting NCT02982486 Non-resectable/metastatic sarcoma or high-grade endometrial cancer with MSI II Nivolumab + ipilimumab ORR Not yet recruiting EOC epithelial ovarian cancer, OS overall survival, PFS progression-free survival, AEs adverse events, ORR overall response rate, irPFS immune-related progression-free survival, TRS tumor reductive surgery, PA para-aortic, DLTs dose-limiting toxicities, MSI microsatellite instability Ongoing immunotherapy trials in gynecologic malignancies NCT02580058 JAVELIN Ovarian 200 Arm 1: Avelumab Arm 2: avelumab + Doxil Arm 3: Doxil Arm 1: Doxil + atezolizumab Arm 2: Doxil + atezolizumab + bevacizumab Arm 3: Doxil + bevacizumab NCT02608684 PemCiGem NCT02891824 ATALANTE Arm 1: placebo + bevacizumab + platinum chemo Arm 2: atezolizumab + bevacizumab + platinum chemo NCT01928394 CheckMate 032 Arm 1: nivolumab Arm 2: nivolumab + ipilimumab Arm 3: nivolumab + ipilimumab + cobimetinib Arm 1: nivolumab + nivolumab maintenance Arm 2: nivolumab + ipilimumab + nivolumab maintenance Arm 1: sequential tremelimumabfollowedby durvalumab Arm 2: combination tremelimumab + durvalumab NCT03038100 IMagyn050 Arm 1: carboplatin + paclitaxel + bevacizumab + atezolizumab Arm 2: carboplatin + paclitaxel + bevacizumab + placebo NCT02718417 JAVELIN OVARIAN 100 Arm 1: carboplatin + paclitaxel Arm 2: carboplatin + paclitaxel + avelumab maintenance Arm 3: carboplatin + paclitaxel + avelumab + avelumab maintanence NCT02628067 KEYNOTE 158 NCT02488759 CheckMate 358 Arm 1: neoadjuvant/metastatic nivolumab Arm 2: nivolumab + ipililumab Arm 3: nivolumab + BMS-986,016 Arm 4: nivolumab + daratumumab Arm 1: chemoradiation followed by pembrolizumab Arm 2: chemoradiation with concurrent pembrolizumab EOC epithelial ovarian cancer, OS overall survival, PFS progression-free survival, AEs adverse events, ORR overall response rate, irPFS immune-related progression-free survival, TRS tumor reductive surgery, PA para-aortic, DLTs dose-limiting toxicities, MSI microsatellite instability Table 2 Impacts of major immunotherapy approaches on various gynecological cancers Immunotherapy approach Targeted cancer type Impact/outcome References (Harvard Style) Immune checkpoint inhibitors (PD-1/PD-L1, CTLA-4) Ovarian, Cervical, Endometrial Demonstrated promise with improved response rates; some patients achieve durable remission, though resistance and side effects remain challenges Scherf, M., Bauerschlag, D.O., Muallem, M., Maass, N. & Alkatout, I., 2022. Mismatch repair deficiency and microsatellite instability. Encyclopedia , 2(3), pp.1559–1576. Schiffman, M., Castle, P.E., Jeronimo, J., Rodriguez, A.C. & Wacholder, S., 2007. Human papillomavirus and cervical cancer. The lancet , 370(9590), pp.890–907. Cancer vaccines (e.g., personalized vaccines) Ovarian, Cervical Effectively mobilize antitumor T cell immunity; some clinical trials show increased T-cell responses and potential for tumor regression Tanyi, J.L., Bobisse, S., Ophir, E., et al., 2018. Personalized cancer vaccine effectively mobilizes antitumor T cell immunity in ovarian cancer. Science translational medicine , 10(436), p.eaao5931. Adoptive T cell therapies (e.g., CAR-T) Endometrial, Ovarian Emerging evidence of efficacy; limited clinical data but promising in preclinical models B. (2019). Adoptive cellular therapies: the current landscape. Virchows Archiv , 474(4), pp.449–461. Cytokine therapies (e.g., IL-2) Cervical, Ovarian Used to enhance immune activation; benefit limited by toxicity, with ongoing research to improve safety Rousset-Rouviere et al., 2021. Endometrial carcinoma: Immune microenvironment and emerging treatments in immuno-oncology. Biomedicines , 9(6), p.632. Combination therapies (e.g., checkpoint inhibitors + chemotherapy/radiotherapy) Cervical, Ovarian Show enhanced efficacy over monotherapy; ongoing trials aim to optimize protocols Lynam, S., Lugade, A. A., & Odunsi, K., 2019. Immunotherapy for gynecologic cancer: current applications and future directions. Clinical Obstetrics & Gynecology , 63(1), pp.48–63. Microbiome modulation Endometrial, Ovarian Under investigation; potential to improve immunotherapy responses Rundle-Thiele et al., 2021. Prevention of endometrial cancer through lifestyle interventions: A systematic review and synthesis. Gynecologic Oncology Reports , 39, p.100,900. Impacts of major immunotherapy approaches on various gynecological cancers

The incessant increase in worldwide cancer cases has raised the need for more efficacious cancer therapy, given that traditional therapies are limited by their toxicity and restricted use [ 115 ]. Vaccines are historically used to prevent infectious diseases; however, there have been advancements in cancer vaccines and other non-infectious diseases over the decades. Their compositions and techniques suggest that therapeutic cancer vaccines could be microbial vector-based, cell-based, nucleic acid peptide-based, or in situ [ 92 , 223 ]. Cancer vaccines are immune-based therapies designed to stimulate immune cells to recognize and fight off cancer cells; they could be prophylactic or therapeutic/curative. Evidence suggests that the host immune system is capable of identifying and destroying oncogenes and, on the other hand, can suppress immune responses within the tumor microenvironment, thus fostering tumor growth; this implies that the immune system determines the fate of cancer progression and/or attenuation [ 75 , 85 , 192 ]. These are administered to healthy individuals to induce immune memory, which prevents morbidity caused by cancer. Human papillomavirus (HPV) and hepatitis B virus (HBV) vaccines, such as Gardasil and Cervarix, have been used to prevent viral infections that cause cancers, including liver and cervical cancers. For those who already have cancer, they can only benefit from therapeutic vaccines [ 42 ]. Therapeutic cancer vaccines are used for cancer management by re-stimulating immune responses to the cancer cells; this is achieved by activating antigen-presenting cells like dendritic cells, which present cancerous cells to T cells [ 42 ]. Sipuleucel-T (Provenge) is one of the personalized prostate cancer vaccines, which is formulated from the patients’ dendritic cells and infused back into the patients; this vaccine thus primes the immune system to attack prostate cancer cells. Another vaccine group, cancer peptide vaccines made up of peptides of tumor antigens, has been used for many cancers, like lung and breast cancers [ 31 , 202 ]. Nucleic acid vaccines are currently explored in cancer immunotherapy; these vaccines carry and deliver cancer-specific antigens that are genetically encoded into the body [ 114 ]. These are modified to infect and destroy specific cancer cells and to excite anti-tumour immune responses. In contrast, tumor cell-based vaccines are inactivated tumor cells that train the immune system against specific tumor antigens. Oncolytic viruses are engineered to infect and lyse tumor cells while selectively stimulating antitumor immunity. Talimogene laherparepvec (T-VEC) is an oncolytic virus vaccine that is used to treat melanoma. The contribution of vaccine immunotherapy is undisputably remarkable, but not without drawbacks. Cancer immunotherapy has some limitations, including the heterogeneity of tumor antigens, the ability of cancer cells to evade immune recognition, and their high cost. Recent approaches focus on target-specific cancer vaccines, including GVAX, which uses genetically modified tumor cells to modulate the immune system, which is used in pancreatic cancer [ 52 ]. This includes the collection, engineering, or expansion and infusion of modified T lymphocytes into patients to detect and eliminate malignancies. Autologous T cells are obtained from patients and then modified and amplified before administration to patients. Chimeric Antigen Receptor T-cell therapy (CAR-T) is an adoptive T-cell therapy that includes genetic modification of a patient’s autologous T cells. This modification causes T cells to express chimeric antigen receptors (CAR), which direct T cells to specifically bind to cancer cells with the targeted antigens on their surfaces. This targeted binding activates signaling pathways, which aid in the elimination of cancer cells. CAR-T therapy recognizes tumor-specific antigens, while TCR therapy enhances antigen specificity. On the other hand, TCR-T (T-cell Receptor T-cell) Therapy uses natural TCRs to attach to tumor antigens, which are presented by TCR-T (T-cell Receptor T-cell) Therapy, modifying T cell expression of T cell receptors [ 252 ]. TCR, which recognizes tumor-associated antigens on cancer cells ' surfaces. Moreover, tumor-infiltrating lymphocyte therapy adopted the use of engineered T cells, which are extracted from tumor tissues to enhance immune responses to cancer cells [ 28 , 93 ]. These are molecules that mimic the immune system’s responses to cancer cells. They bind specific tumor antigens on cell surfaces and are designed to target tumor-associated antigens. Trastuzumab (HER2-targeting mAb) targets HER2-positive cancers, including breast and gynecological cancers. Bevacizumab (VEGF inhibitor) inhibits angiogenesis and is used in ovarian cancer. Monoclonal Antibodies (mAbs) cancer treatment [ 89 , 243 ]. Cytokines are small signaling proteins produced by many immune-competent cells. Cytokines modulate immune responses; their high immune competence is exploited in cancer immunotherapy. Interleukin-2 (IL-2) is a potent activator of T cells and natural killer cells; thus, it boosts immune responses and stimulates IFN-gamma production. Interferons are a superfamily of structurally related cytokines; they are known for their anti-viral and immune-modulatory effects [ 32 ]. They enhance antigen presentation and immune activation. They have been used in various cancers, including melanoma, sarcoma, and multiple sclerosis [ 171 , 214 ].

Evolving progress in cancer immunology has shown a strong network between immune cells and cancer cells, cancer microenvironment, and the function of the immune system in cancer progression. Compared to the conventional approach of killing cancer cells, immunotherapy strives to stimulate the role of the immune defense against the destruction of cancer cells. Lampert et al., [ 105 ]. Immunotherapies portray a new approach to the treatment of gynecological cancers and provide possibilities for prolonged benefits even in full-blown diseases. These advances have helped improve the diagnosis of patients receiving conventional treatments, with better anticancer activities and less cellular toxicity [ 133 ]. Also, Innovations in Next-generation immunotherapeutic strategies, such as vaccines, monoclonal antibodies (mAbs), neoantigens, checkpoint inhibitors, adoptive cell transfer therapy (ACT), and chimeric antigen receptor (CAR)-T cell transplantation, have emerged as new ways of detecting molecules and pathways in cancer research [ 240 ]. Antibodies with two binding sites that target two different antigens or epitopes on the same antigen are known as bispecific antibodies (BsAbs). BsABs are designed to strictly target and reactivate immune cells, control the activation of immune cells, adjust the outcome and role of immune cells, enhance the tolerance of immune cells, and facilitate a return to immune homeostasis. Ma et al. [ 126 ]. However, once bound to antigens, bispecific antibodies can stimulate a certain activation of effector cells before target cells, such as T cells and cancer cells [ 251 ]. Bispecific T-cell engager antibodies (BiTE) and trispecific antibodies (TrAbs or TrioMabs) are the most well-known BsABs. Blinatumomab, a BiTE approved for relapsed or refractory B-cell precursor acute lymphoblastic leukemia in adults and children, and Catumaxomab, a TrAB used for the treatment of EpCAM-positive ovarian and gastric cancer, are the two BsAbs that have been authorized for use in patients over the years [ 103 ]. Oncolytic virus therapy is a cancer therapy that uses a virus as an active drug reagent. According to Fukuhara et al., [ 71 ], oncolytic viruses are either naturally occurring or genetically modified viruses that selectively reproduce in and eradicate cancer cells without endangering healthy tissues. Oncolytic viruses proffer the benefits of selective replication in cancer cells, release of different eukaryotic transgene payloads, induction of immunogenic cell death, improvement of antitumour immunity, and a bearable safety profile that does not coincide with other cancer therapeutics. Examples include GM-CSF-expressing adenovirus CG0070 for bladder cancer, vaccinia virus JX-594 for hepatocellular carcinoma, T-Vec (talimogene laherparepvec) for metastatic tumors, and Reolysin for head and neck cancer [ 193 ]. Equally, using gene editing technology, engineered peripheral T cells with fixed antigen-binding receptors like tumor-specific T cell receptors or chimeric antigen receptors could aid adoptive T cell therapy when compared with tumor-infiltrating lymphocytes. Some examples of T-Cell engineered therapies are Tisagenlecleucel for B-cell acute lymphocytic leukaemia and non-Hodgkin lymphoma, and Axicabtagene ciloleucel for Large B cell lymphoma [ 111 ]. Vaccine-mediated immunotherapy entails the use of a distinct antigenic vaccine of the tumor to subdue tumor growth or cancer recurrence by inducing an immune response [ 240 ]. Cancer vaccines are vaccines that stimulate an immune response specifically directed against malignant cells and can be applied prophylactically and therapeutically. The goal of prophylactic vaccination is to induce an immune response that will recognize, eliminate, and stop malignant progression, while Therapeutic cancer vaccines function as a booster for pre-existing antitumor immune responses or activating antitumor immunotherapies that have been actively administered to the patient. Examples of prophylactic vaccination against Human Papillomavirus infection are Gardasil, Cervarix, and Gardasil 9 [ 254 ]. Neoantigens, which originate from somatic DNA changes in cancer cells, are tumor-specific antigens that are not present in healthy tissue. Mechanisms, including viral open reading frames (ORFs), aberrant transcriptome variations, post-translational modifications, and genomic mutations, can all contribute to the formation of these malignancies [ 235 ]. Because they can increase the immune response to cancer cells, neoantigen vaccines are being researched as cancer immunotherapies [ 111 ]. CAR-T cell therapy uses genetically engineered T cells with a synthetic receptor to target cancer-specific antigens [ 44 ]. Chemotherapy, when incorporated with immunotherapy advances, has been proven to be more beneficial. A major advantage is prompt cytoreduction, which leads to a decrease in the tumour load and tumour-mediated immunosuppression. Chemotherapy and radiation therapy, when combined with immune checkpoint inhibitors, may enhance neoantigen presentation while lowering immune evasion. Butterfield and Najjar, [ 24 ]. Oncolytic viruses paired with CAR-T treatment have the potential to improve the overall anti-tumor immune response. For example, Benencia et al. [ 14 ] showed that the administration of oncolytic herpes simplex virus type 1 (HSV-1) in patients with recurrent gynecologic malignancy caused tumor shrinkage and extended relapse-free life. Similarly, immune checkpoint inhibitors can be used in combination with targeted therapies such as angiogenic inhibitors and PARP inhibitors. Durvalumab, when used with Olaparib, upregulates CXCL9/CXCL10, IFN-γ, TILs, and IFNγ/TNFα expression in patients with relapsed ovarian cancer [ 105 ]. Personalized medicine in cancer treatment comprises using genetic, immunological, and proteomic profiling to provide therapeutic choices and prognostic information [ 181 ]. Healthcare providers can employ genetic testing and molecular profiling to identify relevant practical mutations and adjust appropriate medications, resulting in effective illness management. One important area of interest in pancreatic cancer treatment is the effect of genetic alterations in the DNA Damage Response (DDR) pathway. Examples include the utilization of the NCI-MATCH/MATCH (Molecular Analysis for Therapy Choice) experiment, a precision medicine cancer treatment clinical trial that assigns patients to targeted therapy based on the precise mutations found rather than their disease type. The TAPUR (Targeted Agent and Profiling Utilization Registry) study, which assess the safety and effectiveness of FDA-approved targeted therapies in patients with advanced cancer harboring specific genetic alterations, and finally, the IMPaCT (Integrative Molecular Profiling of Pancreatic Cancer Therapy) trial, which focuses on matching patients with targeted therapies based on the molecular characteristics of their tumors, allowing for more personalized treatment regimens [ 40 ]. The use of AI and machine learning (ML) in precision oncology may allow for the study of large amounts of “omics data” in conjunction with clinical, pathology, therapy, and outcome data, giving sophisticated and powerful tools for optimizing biomarker creation and patient treatment. AI/ML techniques can assess disease measurements that are becoming increasingly complicated and high-dimensional, providing a better knowledge of tumor biology, including the interaction of the tumor microenvironment with the tumor. For instance, DeepProg is a novel ensemble framework of deep-learning and machine-learning approaches that robustly predicts patient survival subtypes using multi-omics data. It identifies two optimal survival subtypes in most cancers and yields significantly better risk-stratification than other multi-omics integration methods [ 166 ]. DeepProg is a distinct ensemble framework that combines deep and machine-learning algorithms that utilize multi-omics data to predict the survival subgroups of patients. Usually, it yields two optimal survival subgroups and produces a better risk stratification than other multi-omics integration methods [ 166 ].

Various cancers, including gynecological cancers, Tumor Mutational Burden (TMB), Microsatellite Instability (MSI), and PD-L1 expression, have emerged as critical predictive biomarkers for assessing the likelihood of success with immunotherapy. Tumor Mutational Burden (TMB) indicates the number of somatic mutations in the genome of a tumor; high TMB signifies increased neoantigens. Tumors with high neoantigens are more immune-responsive; otherwise, they are vulnerable to immune checkpoint inhibitors. High TMB is characteristic of MSI and dMMR: Such tumors are more likely to respond to PD-1 inhibitors like pembrolizumab [ 109 ]. For example, the FDA has approved pembrolizumab for treating MSI or dMMR cancers, including endometrial cancer [ 154 ]. Ovarian cancers, in lieu, have lower mutation rates, but some ovarian cancers exhibit errors in DNA repair and other mutations; these subtypes may have high TMB and respond to immunotherapy. Contrarily, HPV-positive cervical cancers are characterized by moderate to high TMB due to HPV mutations, making them vulnerable to PD-1 inhibitors and other immunotherapies. Vulvar cancers are similarly responsive; however, HPV-negative vulvar cancers have a relatively low mutational burden and may not be as responsive. High TMB is associated with improved outcomes for immunotherapy in several cancers, and it helps predict which group of patients is likely to benefit from immune checkpoint inhibitors [ 3 ]. Tumors with high Microsatellite instability (MSI) also exhibit large amounts of mutation and produce highly immunogenic neoantigens, making them immune-responsive [ 235 ]. MSI is typical of Endometrial and HPV-positive cervical cancers, making them susceptible to immune response. Only a subset of ovarian cancer has MMR defects. Vulvar cancers are not typical of MSI and dMMR, but HPV-positive vulvar cancers can benefit from their high immune response due to the immune response against the viral antigens produced by HPV [ 191 ]. The protein known as PD-L1 (Programmed Death-Ligand 1) is expressed on the surface of immune cells and tumor cells in the tumor microenvironment. The expression of the protein causes binding to the receptor on T cells, thus inhibiting T cell activation. Inhibitors of these proteins prevent the binding, enabling T cell activation and the attack of tumor cells. The expression of PD-ligand in endometrial cancer varies in HPV-positive cervical and vulvar cancers. PD-ligand expression is high, while only specific subtypes of ovarian cancers have elevated expression [ 77 ]. Genetic and epigenetic signatures have proven valuable in predicting the response to immunotherapy and targeted therapies. BRCA1/2 mutations, Homologous Recombination Deficiency (HRD), and other key signatures are explored for their treatment-guiding ability. BRCA1/2 are tumor-suppressing genes that are associated with the repair of dsDNA via the homologous recombination repair pathway. Mutation in BRCA genes impairs the DNA repair process, leading to instability of the entire genome; tumors with altered BRCA genes have deficient homologous recombination, which makes them susceptible to therapies that induce DNA damage [ 102 ]. BRCA 1/2 mutation is a predictive biomarker in gynecological cancers: ovarian cancers are often characterized by alterations of these genes, especially in exceptionally high-grade serous ovarian carcinoma (HGSOC). BRCA mutant ovarian cancers are highly genomically unstable and sensitive to immunotherapy. Ovarian cancers are susceptible to PARP inhibitors (e.g., olaparib, niraparib) and chemotherapy. A combination of these therapies increases the efficacy substantially. In endometrial cancers, these mutations are not as common; some subtypes, however, exhibit HRD and are highly ICI-responsive. BRCA mutations are rare in cervical and vulvar cancers- HRD can occur through HPV-positive cervical cancers, making them responsive to PARP inhibitors and DNA-damaging therapies [ 99 ]. Liquid biopsy and circulating tumor DNA (ctDNA) are powerful tools for treatment response in various cancers. Added to the less invasive nature, the tools give insight into tumor dynamics, genetic mutation, and resistance mechanisms. Liquid biopsy analyses bodily fluid to detect tumor molecules such as extracellular vesicles and circulating tumor cells. Circulating DNA is widely used in monitoring cancers, likely because it gives insight into tumor genetic alterations. ctDNA are small DNA fragments shed into the bloodstream from the tumor sites; these fragments represent the mutations at the tumor site and, thus, are exploited to track genetic changes caused by a response to the tumor and treatment. Clinicians can gain valuable insights into tumor responses by assessing ctDNA over a treatment course. This can be used to monitor residual disease progression, predicting response to chemotherapy and mutational burden as well as resulting resistance [ 57 ]. Liquid biopsy and ctDNA are obtained in a non-invasive procedure, thus allowing for repeated sampling. This allows for real-time monitoring of tumor progression, treatment efficacy, and mutation. Additionally, these tools allow for early detection of relapse. Personalized biomarker has greatly advanced cancer treatments, including gynecological cancers. Although biomarkers hold great potential, their clinical application has inherent limitations. Intra-tumour and intratumor variations are common in gynecological cancers; this implies varied areas within the same tumor, and tumors from different patients can have distinct genetic mutations. This makes extrapolation of biopsy or biomarker test difficult, as this may not accurately represent the entire tumor molecular print. Tumor heterogeneity can result in false results; caution must thus be exercised in extrapolating findings. Another limitation is the lack of standardization - many gynecological biomarkers are not consistently validated across clinical settings- and controversies over the most effective test for BRCA 1/2 mutation. However, BRCA testing is widely established in ovarian cancer. It is expensive as a high-end therapeutic tool, and not all healthcare systems or patients can access or afford the diagnostic tool. Moreover, there are variations in testing methodologies between laboratories and testing centres. As an emerging tool, technical challenges during sample collection, DNA extraction, or sequencing may lead to varied results. Data interpretation is subject to a risk of subjectivity. Finally, an overreliance on biomarker data may cause potential negligence due to other important factors, such as TME. Genetic testing, especially in gynecological cancers, may affect family planning; this may give rise to anxiety. Thus, biomarkers should be a part of diagnostic tools, not used in isolation.

In conclusion, although immunotherapy provides promising potential in the management of gynecological cancers, its full potential remains largely unrealized due to significant challenges. The major challenges are tumor heterogeneity, immune resistance mechanisms (such as immune evasion, suppressive tumor microenvironments, and genetic alterations), and the lack of reliable predictive biomarkers, especially in less common cancers like vulvar cancer. Despite advances in understanding the tumor immune microenvironment, many questions persist regarding the mechanisms underpinning immune resistance, adverse immune-related side effects, and patient heterogeneity. Existing gaps in knowledge involve limited efficacy of existing immunotherapies, insufficient characterization of tumor-immune interactions, and a lack of standardized, non-invasive biomarkers for patient selection and treatment monitoring. Future research should focus on elucidating the complex interactions within the tumor microenvironment, identifying robust biomarkers for predicting response and toxicity, and developing combination strategies that enhance immune activation while reducing adverse effects. In addition, expanding clinical trials exploring novel regimens, optimizing treatment durations, and improving targeted delivery are essential to improve patient outcomes. Finally, addressing these challenges through comprehensive, multidisciplinary research will be pivotal in harnessing the full therapeutic potential of immunotherapy for gynecological malignancies.

Immune-based therapies have revolutionised the treatment of many cancers since their first description by W. Colley in 1890 and have seen an increase in the amount of clinical testing of these therapies on various cancer types [ 46 ]. Immunological techniques in recent times have focused on immune checkpoint inhibitors (ICIs), adoptive cell transfer (ACT), and cancer vaccines [ 41 , 96 ]. The principle of ACT revolves around introducing autologous or modified T-cells (tumour-infiltrating lymphocytes (TILs). It also involves the use of engineered T-cell receptors (TCR), which bind to specific tumour antigens or chimeric antigen receptors (CAR) that help T-cells better recognise antigens [ 54 , 178 , 200 ]. Tumours usually modulate immune checkpoints to facilitate immune evasion, hence Inhibiting ICs associated with T-cells is particularly promising [ 25 ]. The cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and PD-1/PD-L1 are the main focus of this technique [ 122 ]. Cancer vaccines stimulate antigen-presenting cells to improve the function of T-cells by introducing tumour antigens with adjuvants [ 66 ]. However, despite their clinical significance, some patients are unable to respond to ICIs (primary resistance), while those that do respond develop resistance to immunotherapies later on (acquired resistance) [ 209 ]. An abnormality in any of the stages of the anti-tumour immune response–from tumour antigen detection to death of tumour cells by immune cells–will result in primary resistance to immune therapy [ 250 ]. As T-cells mature, autoantigen-sensitive T-cells are cleared, and mature T-cells can respond to tumour antigens released by cancer-transformed cells [ 107 , 250 ]. The tumour mutation burden (TMB) of the tumour cells, therefore, can determine the response of T-cells, as tumours having higher TMB are likely to be detected by the immune system, and are hence responsive to immune checkpoint blockade therapy [ 216 ]. Consequently, cancers that possess fewer TMB will have a reduced responsivity to immunotherapy, resulting in primary resistance. Enhancing tumour immunogenicity might help improve immunotherapy outcomes in patients with primary resistance [ 138 ]. Resistance is also conferred by the unsuccessful infiltration of CD8 + T-cells, which have anti-tumour activity. The apoptosis-inducing Fas ligand (FasL) is expressed in the tumour vasculature, and this ligand negatively inhibits the infiltration of CD8 + T-cells while encouraging the presence of Tregs in the TME, not affected by the FasL-mediated apoptosis [ 151 ]. Tregs also express TGF-β as well as IL-10, which can also inhibit the activity of CD8 + T-cells and promote tumourigenesis [ 250 ]. In addition to TGF-β and IL-10, adenosine and IDO1 are immunosuppressive molecules secreted in the TME that contribute to poor prognosis and immune resistance [ 118 , 212 ]. In the TME, T-cell proliferation is further hampered by MDSCs through the generation of oxidative stress, depletion of available nutrients necessary for lymphocyte functioning, and enhancement of the activity of Tregs [ 72 ]. Since tumour cells exhibit a high rate of glycolysis and altered vasculature, the T-cells are faced with reduced nutrient perfusion in the TME, resulting in diminished effective activity [ 27 ]. The extracellular matrix secreted by cancer-associated fibroblasts also forms a mesh-like barrier that hinders T-cell migration [ 185 ]. In resistance to PD-1/PD-L1 therapy, the activity of cytotoxic T-cells leads to an immunosuppressive compensatory upregulation of B7-H1 expression [ 81 ]. It can also be due to T-cell exclusion in the TME, which is influenced by TMB and FasL, loss of interferon signalling, and lack of antigen presentation by antigen-presenting cells [ 224 ]. Interferon signalling can also be affected by mutations in the Janus kinase (JAK1/2) pathway [ 245 ]. The lack of phosphatase and tensin homolog (PTEN), which is a tumour suppressor that regulates PI3K/AKT signalling, also reduces T-cell infiltration into tumours, inhibits autophagy, and increases VEGF expression [ 163 ]. Hence, PTEN-deficient tumours do not respond properly to PD-1/PD-L1 inhibitors. Studies have also noted that the suppression of Microphthalmia-associated transcription factor (MITF) through AXL activation and eIF2B inhibition will lead to reduced ability of immune cells to present antigens [ 61 , 125 ]. To mitigate immunotherapy resistance and improve clinical outcomes, several strategies have been proposed, and some have even shown promising results in early-stage clinical trials. One method involves targeting antigen-presenting cells (APCs) to improve T-cell priming and consequently their activity [ 250 ]. Salmon et al. [ 186 ] showed that administration of FLT3L, a growth factor, improved the function of APCs and can potentially reverse anti-PD-L1 resistance. The use of DC vaccine has also shown promise in improving the activity of DCs and radiotherapy, which increases MHC I levels, and can also be used to upregulate MHC I/II, improving antigen presentation [ 66 , 213 ]. Radiation therapy usually leads to the release of tumour antigens, which can enhance antitumour activity [ 174 ]. Blocking the CAF-mediated CXCL12/CXCR4 axis can also improve T-cell infiltration into the TME. CXCL12 promotes T-cell exclusion from tumours, and by inhibiting this pathway, T-cell penetration is enhanced [ 63 ]. In contrast, the chemokines CXCL9 and CXCL10 attract cytotoxic T-cells to the TME, and doxorubicin has shown potential in increasing CXCL10 expression ( NCT02888665 ) [ 101 ]. Inhibiting focal adhesion kinase could also improve T-cell migration to the TME [ 87 ]. Targeting MDSCs is also a viable option in mitigating immunosuppression. An interesting strategy involves stimulating the maturation of MDSCs into APCs through the use of CD40 agonist antibodies, which will consequently improve tumouricidal activity (Luhesi et al., 2016). PI3K inhibitors can also suppress MDSCs, thereby reducing immune suppression and activating T-cells [ 101 ] (Fig. 6 ). Fig. 6 Resistance mechanisms in cancer immunotherapy Resistance mechanisms in cancer immunotherapy

A systematic literature search was performed across Scopus, PubMed, PubMed Central, and Google Scholar databases, targeting peer-reviewed articles published up to 2023. The search words were “gynecological cancers” OR “vulvar cancer” OR “cervical cancer” OR “endometrial cancer” OR “ovarian cancer” AND “immunotherapy” OR “immune checkpoint inhibitors” OR “PD-1” OR “PD-L1” OR “CTLA-4” OR “cancer vaccines” OR “adoptive T cell therapy”. Clinical trials, key translational studies, and mechanistic pre-clinical studies were included. The selection emphasized studies on immunotherapeutic strategies, such as immune checkpoint inhibitors, cytokine therapies, cancer vaccines, and adoptive T cell therapies in gynecological cancers, with a focus on clinical trials, preclinical research, and reviews addressing mechanisms, efficacy, and challenges.

Gynecological malignancies like vulvar, cervical, endometrial, and ovarian cancers are a global challenge and account for a significant percentage of cancer-related morbidity and mortality among women [ 255 ]. Globally, cervical cancer remains the fourth most common cancer among women, with about 210,000 children losing their mothers to it each year [ 18 ]. Although it is preventable through screening and vaccination for human papillomavirus (HPV), the main predisposing factor for cervical cancer, vaccination rates are uneven across regions, resulting in 10- to 13-fold disparities in incidence and mortality rates between regions [ 201 ]. Ovarian cancer is quite uncommon, yet it is the most lethal gynecological malignancy, usually diagnosed at advanced stages due to the subtle clinical manifestations [ 155 ]. Also, vulvar cancer is relatively rare, but it is characterized by management hurdles because of its high relapse rates and restricted treatment modalities [ 156 ]. Although endometrial cancer solely affects postmenopausal women, its incidence is increasing due to high hormonal influence and obesity rates [ 50 ]. Conventional therapies, such as chemotherapy, surgery, and radiotherapy, are the mainstays in the management of these cancers; however, their effectiveness is often restricted by issues such as resistance development, significant adverse effects, and recurrence. For instance, platinum-based chemotherapy, while effective initially, frequently encounters resistance, diminishing its long-term efficacy [ 49 ]. Experimental and clinical studies have also reported the toxicity of chemotherapies [ 4 , 62 ] and radiotherapy [ 228 ] on non-target organs. Although surgical interventions are also potentially curative in early stages, they are often associated with morbidity and are less effective in advanced cases [ 9 ]. These limitations affect the quality of life of patients and highlight the necessity for a less toxic and effective modality of cancer management. On the other hand, immunotherapy is a treatment that activates innate immunity to target malignancies and relies on immune surveillance to detect and respond to cancer cells. Malignant cells evade this response by upregulating checkpoints like PD-L1 and CTLA-4, which inhibit T cell activation and promote tumor growth [ 20 , 246 ]. Immune checkpoint inhibitors counteract these pathways, enhancing anti-tumor immunity. This approach has proven effective in melanoma and lung cancer and shows promise for gynecological cancers, especially those linked to viral infections such as HPV-related cervical cancer. Current immunotherapy for gynecological cancers includes checkpoint inhibitors, cytokine therapies, cancer vaccines, and adoptive T cell therapies. Despite their efficacy, challenges remain due to immune-related side effects, resistance, and the lack of reliable prognostic biomarkers. Understanding the mechanisms behind these limitations is essential to optimizing treatments and patient selection. This review discusses the role of immunotherapy in gynecological cancers, highlighting current applications, challenges, and future directions to guide clinical practice and research.

Vulvar cancer is a relatively rare genital cancer with a low incidence rate compared to other gynecological cancers. The rarity of vulvar cancer makes it a risk, as it contributes to delayed diagnosis and a lack of targeted treatment regimens [ 26 ]. Of all gynecological cancers, vulvar cancer accounts for 4.5% and 0.6% of all cancers in women. It is more prevalent in women above 60 years, especially those with HPV infections, but it can occur in younger women. In the US, 2 of every 100,000 women have vulvar cancer annually. Other risk factors include age, smoking, and immunosuppression, among others. Squamous cell carcinoma makes up over 90% of all vulvar cancers. Other subtypes include melanoma, basal cell carcinoma, and adenocarcinoma. Although rare, they are clinically relevant [ 26 , 60 ]. Vulvar cancer is most often diagnosed at the advanced stage due to how rare the cancer is; the early symptoms are confused with infections and inflammatory disorders. Delayed diagnosis results in poor outcomes. The vulva is anatomically located at a sensitive and intimate site. Many women are uncomfortable with discussing intimate matters with healthcare providers, which makes proper diagnosis difficult. Additionally, there is no standardized routine screening for vulvar cancers; diagnosis is made from visual inspections [ 26 , 152 ]. To prevent or detect vulvar cancer early enough, it is pertinent to understand and identify risk factors. This is, however, rarely the case as the lack of routine screening contributes to late-stage diagnoses. Till now, the treatment regimen has combined surgery, radiotherapy, and chemotherapy. Given the aforementioned problems that give rise to late detection, there is almost always a need for a wide local removal of the tumor or the entire vulva and surrounding tissues. Surgical treatments cause permanent damage to the aesthetics of the genital area, and there may be a need for reconstructive surgery post-vulvar therapy [ 162 ]. Furthermore, there is the potential risk of toxicity, which could culminate in sexual dysfunction, urinary problems, and chronic pain. In cases where decisions affect other members of the family, ethical considerations become important [ 26 ]. Vulvar cancer has a high relapse rate, especially in distant metastasis. The prognosis depends on the stage of diagnosis. In cases of early detection, prognosis is relatively good, with a 5-year survival rate of approximately 85%; in advanced stages, only about 30–40% have a 5-year survival rate. This is quite understandable, as there is limited research on optimal diagnoses and treatment strategies [ 26 , 127 ]. Vulvar cancer (VC) resists immune surveillance and clearance via several mechanisms. One of these includes dysregulation of immune checkpoints- overexpression of PD-L1 (Programmed Death-Ligand 1) causes these ligands to bind PD-1 on T cells, thereby inhibiting T cell activation. Similarly, CTLA-4 (Cytotoxic T-Lymphocyte-Associated Protein 4) competes with CD28 for B7 ligands, reducing T-cell stimulation. T-cell inhibition limits immune responses, causing cancer progression (Hossain, 2024). Another method VC exploits is targeting antigen-presenting cells; VC downregulates MHC I molecules, resulting in dampened T cell recognition of cancer cells. Tregs, tumor-derived macrophages, and other myeloid suppressor cells can invade the tumor microenvironment. These macrophage subtypes polarize macrophages towards immune suppression and angiogenesis, thereby limiting immune responses [ 12 ]. Finally, the release of immunosuppressive cytokines TGF-β, IL-10, and dysregulated chemokine expression also inhibits T cell functions and infiltration of immune cells into the tumor microenvironment [ 2 ]. While the exact mechanism is not yet fully understood, these are the probable mechanisms of immune evasion exploited by VCs. Potential immunotherapy regimens include modulation of the TME; this could be achieved by targeting Tregs and myeloid-derived suppressor cells, using anti-CD25 antibodies, and Drugs targeting CSF1R or IDO pathway inhibitors. Current cancer vaccines, such as HPV-related vaccines, can stimulate anti-tumor responses, although very nonspecifically. Personalized neoantigen vaccines can be used to stimulate tumor-specific immune responses. Adoptive cell therapy, such as ex vivo expansion and infusion of tumor-reactive T cells and engineering targeted T cells, is a potential technique [ 45 ]. Modified viruses that lyse targeted tumor cells and stimulate immune reactivity are options; HDAC (histone deacetylase) inhibitors and DNA methyltransferase inhibitors can restore immune-related gene expression [ 194 ]. Cancer is a rare malignancy, and due to its infrequency, clinical trials exploring novel therapies like immune checkpoint inhibitors are still in the early stages. However, immune checkpoint inhibitors, particularly PD-1/PD-L1 inhibitors (such as pembrolizumab), have shown promising results in a variety of cancers, including those related to HPV infection, which is a common etiology of vulvar cancer [ 182 , 191 ]. Pembrolizumab (Keytruda) in Vulvar Cancer: Pembrolizumab is an anti-PD-1 monoclonal antibody; the antibody prevents PD-1 receptor from binding to PD-1 on T cells, thus ensuring T cell activities, which mainly attack cancer cells. Some clinical studies have reported remarkable success with the use of this monoclonal antibody in patients with advanced or metastatic vulvar squamous cell carcinoma (SCC)- In a tiny Phase II trial, pembrolizumab was used to treat patients with advanced vulvar SCC, particularly those whose disease had progressed after standard therapies (surgery, radiation, or chemotherapy) [ 38 , 195 ]. The authors reported tumor shrinkage and moderate response rates in patients. This is suggestive of the promising potential of checkpoint inhibition. Pembrolizumab has also been tested in combination with chemotherapy or radiotherapy. This has been used in patients with advanced solid tumors, including vulvar tumors. Pembrolizumab is combined with other inhibitors, including CTLA-4 inhibitors, Ipilimumab (Yervoy). Ipilimumab enhances T cell activation. In synergy with pembrolizumab, there should be increased efficacy. Early-phase clinical trials with this combination show effectiveness in cancers, including melanoma and non-small cell lung cancer. Thus, this is currently being tested in vulvar cancer [ 38 , 195 ]. Considering how uncommon vulvar cancer is, like other solid tumors that are genetically and phenotypically heterogeneous, there are no predictive biomarkers. Like other cancer types, VC can acquire resistance to therapies. HPV-positive VCs have a higher mutation rate and may likely respond better to immunotherapy than HPV-negative VCs, which are less responsive; this makes the development of biomarkers challenging [ 183 ]. The unique immunosuppressive TME in vulvar cancer also contributes to the challenges; immune checkpoints and the ratio of suppressive cells in the TME are critical to prediction and therapy development. Many cancers have reliable predictive biofluids, such as blood and urine, which detect circulating tumor DNA or extracellular vesicles. Unfortunately, these liquid biomarkers lack VC due to their rare nature and anatomical location. The management of VCs is faced with significant hurdles, including immune resistance. VC exhibits primary and acquired resistance to existing therapies, including immune checkpoints, chemotherapy, and radiation. Some cancer cells have self-renewal properties, as well as DNA repair mechanisms. Some sunsets of VC cells induce hypoxia as a resistance mechanism against chemotherapy. Restaino et al., [ 175 ], Woelber, [ 232 ]. Fibrosis, altered vascularization, and remodeling of the extracellular matrix components could block the transportation of drugs to targeted tissue sites. Standard management for vulvar cancer centers on surgery (wide local excision or vulvectomy ± inguinofemoral lymphadenectomy for early stages), radiotherapy ± chemosensitization (e.g., cisplatin) for locally advanced disease, and palliative chemotherapy (platinum-taxane) for metastatic cases, with early pembrolizumab showing modest activity in PD-L1 + advanced squamous cell carcinoma post-standard therapy. Key challenges include lack of routine screening leading to late diagnosis, absence of validated predictive biomarkers (e.g., beyond HPV status), limited data from small early-phase ICI trials amid high relapse rates, and mechanisms of primary/acquired resistance in the immunosuppressive TME, hindering personalized immunotherapy approaches for this rare malignancy (Fig. 4 ). Fig. 4 Mechanisms of immune evasion in vulvar cancer Mechanisms of immune evasion in vulvar cancer