Photodynamic therapy for gynecological diseases and breast cancer.

Approximately 5% to 19% of breast cancer patients suffer from chest wall recurrences after mastectomy [ 72 ] . Breast cancer frequently recurs in the skin and soft tissues of the chest wall. These tumors usually involve relatively large areas that form large tumors, numerous small nodules or infiltrating sheets of cells, which cause pain, ulceration, necrosis, and serious skin infection. Surgical removal, site-specific radiotherapy, or both, are the common treatment procedures for chest wall metastasis [ 73 , 74 ] . About half of the patients do not experience adequate tumor control with these therapies. Meanwhile, PDT has been experimentally used to treat recurrent breast cancers in the chest wall. A few clinical trials on PDT have been performed to treat chest wall metastasis. A phase I clinical study of PDT using mono-L-aspartyl chlorin e6 (Npe6) as a photosensitizing agent was performed over an 18-month period in the US [ 75 ] . The design of this study consists of a single escalating dose of Npe6 on 11 patients with a variety of solid tumors, including 4 patients with recurrent breast adenocarcinoma. Complete tumor response was observed in 2 out of 4 patients with breast adenocarcinoma. The common adverse effects were pain, erythema, and edema within and adjacent to the treated areas. The use of low-dose Photofrin-induced PDT was suggested to treat chest wall progression of breast carcinoma [ 76 , 77 ] . Fourteen patients with more than 500 truncal metastasis were treated with Photofrin-PDT. All patients demonstrated tumor necrosis, with 9 out of 14 complete responses [ 76 ] . Moreover, PDT with m-THPC resulted in a complete response in all 7 patients with breast cancer recurrences [ 78 ] .

Vulvar intraepithelial neoplasia (VIN) is a precancerous skin lesion of the vulva, and is described as the dysplasia of squamous epithelium of the vulva. VIN is not an invasive cancer, but may eventually become an invasive squamous cell cancer if left untreated. Before 2004, VIN was classified from VIN 1 (mild atypia) to VIN 3 (severe atypia). However, the International Society for the Vulvovaginal Diseases has reclassified VIN. The term VIN now refers only to high-grade abnormal squamous lesions (previously known as VIN 2 and VIN 3). VIN is most commonly seen in immunocompromised and postmenopausal women [ 35 ] . The current incidence of VIN 3 is increasing, whereas the mean age of affected women is decreasing. About 28% to 52% of patients with VIN 3 are aged 40 years or younger [ 36 ] . The risk factors are similar to those with CIN. Race, parity, and comorbid medical conditions seem to have no role in VIN development, whereas cigarette smoking is believed associated with VIN development [ 37 ] . Moreover, an etiological relationship exists between VIN development and 80% to 90% of HPV type 16 infection cases [ 37 ] . The symptoms include itching or burning associated with vulvar irritation, dyspareunia, and labial erythema or swelling. Asymptomatic lesions are less common, and spontaneous regression occurs in less than 1.5% cases [ 38 ] . The traditional treatment options of surgical excision and CO 2 laser ablation are both associated with high rates of disease recurrence, particularly with multifocal disease [ 39 ] .

Carcinoma of the ovary is one of the most common gynecological malignancies, and is the fourth most frequent cause of fatality in women in the United States [ 47 ] . The most common type of ovarian cancer is epithelial carcinoma. The tumors with low malignant potential, which are also known as borderline tumors, are the most well-differentiated (Grade 0), and account for 15% of all epithelial carcinomas in the ovary. The other three grades are well-differentiated (Grade I), moderately-differentiated (Grade II), and poorly-differentiated (Grade III/IV). Well-differentiated tumors have a better prognosis than poorly-differentiated ones. Clear cell carcinoma, especially undifferentiated carcinoma, has a poorer prognosis than the other cell types. Ovarian cancer spreads early by shedding malignant cells into the abdominal cavity and pelvic, aortic, groin, and neck lymph nodes. Many women with early stages of ovarian carcinoma do not suffer from any symptoms. Unfortunately, two-thirds of all women with ovarian carcinoma have advanced disease at the time of diagnosis. Many women are only diagnosed when they have developed abdominal distention because of ascites, although some cases are diagnosed during a routine gynecologic examination. The primary treatment modalities are maximal cytoreductive surgical procedures such as adnectomy, hysterectomy, omentectomy, and pelvic limpadenectomy. In less than 20% of patients with stage III/IV malignancy, bowl resection is necessary to achieve optimal tumor reduction at the time of primary surgery. Peritoneal debulking is often necessary because of the local intraabdominal shedding of tumor cells and tumor growth on peritoneal surfaces [ 48 ] . However, most of these patients experience local progression or recurrence even after aggressive cytoreductive surgery and platinum-based chemotherapy. Moreover, less than 17% patients with stage IV disease and 30% patients with stage III ovarian carcinoma will survive for more than 5 years [ 49 ] . The reason for treatment failure is probably related with the difficulties inherent in surgery within the peritoneal cavity, problems related to cytotoxic agent administration to the tumor cells in cytotoxic concentrations, and the ability of ovarian cancer cells to develop resistance against standard chemotherapies. Patients having platinum-resistant ovarian carcinoma with poor prognosis might benefit from strategies that use a fluorescence staining procedure because of its high selectivity in detecting minimal tumor residuals.

Cervical cancer is the second most common malignancy in women worldwide, with about 500,000 new patients diagnosed every year. CIN is a precancerous condition localized in the squamo-columnar junction of the cervix uteri. The classification ranges from CIN 1 (mild dysplasia) to CIN 3 (severe dysplasia). Human papillomavirus (HPV) infection, mainly high-risk types 16 and 18, is directly related to the development of CIN and cancer [ 14 ] . CIN prevalence has increased during the last few decades particularly among younger women. Results of recently established screening programs showed that the incidence of cervical cancer has decreased by about 50% to 60%. The recent standard of care consists of excision, e.g., loop electrosurgical excision procedure (LEEP), cold knife excision of the transformation zone or local destruction by laser or cryotherapy [ 15 ] . These procedures are commonly painful during treatment and may cause post-operative bleeding. Thus, anesthesia is usually used as a necessary prerogative. The recurrence rates of CIN lesions for more than six months after the treatment are between 5% and 16% for LEEP, 4% and 24% for cryotherapy, and 3% and 30% for laser therapy [ 16 ] . The major drawback of these excision methods is the destruction of the cervical stroma, which may cause cervical insufficiency and/or cervical scar structure that may lead to premature delivery and increase the risk of infertility and the need for caesarean operation [ 17 – 19 ] .

A new approach for targeted PDT was suggested by Stuchinskaya et al. [ 79 ] . Gold nanoparticles conjugated with antibodies are effective in targeting and possibly destroying cancerous tissue through photothermal reaction [ 80 , 81 ] . A 4-component anti-HER2 antibodies-phthalocyanine-polyethylene glycol-gold nanoparticle conjugate is used as a potential drug for targeted PDT. Cellular experiments have demonstrated that nanoparticle conjugates selectively target breast cancer cells that overexpress the HER2 epidermal growth factor cell surface receptor and are also effective PDT agents. The results of a pilot clinical trial of late-stage breast cancer patients treated via laser immunotherapy (LIT) have been previously presented by Li et al. [ 82 ] The protocol consisted of three major components, namely, near-infrared laser for non-invasive irradiation, indocyanine green for selective thermal effect, and immunoadjuvant (glycated chitosan) for immunological stimulation. In 8 breast cancer patients with confirmed stage III or IV cancer available for evaluation, the objective response rate was 62.5% and the clinical beneficial response rate was 75%. This preliminary data suggests that LIT, as a new approach that uses the host immune system to fight cancer cells, has a high level of tolerance and is a promising treatment for metastatic breast cancer. Hu et al. [ 83 , 84 ] have recently developed a successful targeted PDT that can simultaneously target both tumor neovasculature and tumor cells. The preference of a target molecule as receptor tissue factor (TF) was based on a previous finding that TF was selectively expressed in cells and vascular endothelial cells in 80% to 100% of breast tumors, including multidrug resistant tumors [ 85 , 86 ] . TF is also over-expressed by ovarian cancer cells and many other types of cancer (lung, prostate, and colorectal) [ 87 ] . The conjugates of factor VII (fVII) as ligand for TF with Verteporfin or SnCe6 as photosensitizers were used for the targeted PDT. The study showed that TF-targeting PDT using fVII-conjugates enhanced the effect of non-targeted PDT in vitro , and was effective in treating human and murine breast tumor in mice, including chemoresistant breast tumor [ 83 , 86 ] .

Photodynamic therapy provides an emerging alternative to the standard of care methods in anticancer therapy. PDT has been successfully evaluated in HPV-related genital dysplasia, such as CIN and VIN, in ovarian cancer and in chest wall recurrences of breast cancer ( Table 1 ). The preservation of fertility is very important in CIN. The major disadvantage common to all the current standard treatments is the destruction of the cervical stroma, which may cause cervical insufficiency. PDT can be a non-invasive treatment method that preserves cervical function and can easily be performed on an outpatient basis. Response means complete ablation or decrease of lesion site. Cure rate means no recurrence of the disease was noted at follow up of 6 months or longer. For patients with certain types of cancer, such as ovarian cancer, characterized by intraperitoneal dissemination or breast cancer metastasized into the chest wall, effective treatment options are extremely limited. Therefore, using 5-ALA or HAL as photosensitizers provides a platform technology that permits simultaneous detection, diagnosis, and treatment to enable effective administration in a single seamless process. One of the major side effects of PDT is cutaneous phototoxicity, which is dependent on the type of photosensitizer. Therefore, the search for a new photosensitizer with minimal side effects and high selectivity will lead to the development of new methods to diagnose and treat malignant diseases. Moreover, the enhancement of PDT efficacy can be achieved by a combination of immunotherapy or targeted therapy.

Photodynamic therapy (PDT) is a mode of therapy used in cancer treatment where drug activity is locally controlled by light ( Figure 1 ). The ground state non-toxic photosensitizer achieves a higher unstable energy state (singlet state) upon illumination with an appropriate light wavelength and in the presence of oxygen. In this unstable state, the activated photosensitizer releases energy either by emitting heat and light or by the conversion of the unstable state into an intermediate energy state (triplet state) before returning to the stable ground state. In the triplet state, the photosensitizer generates reactive oxygen species (ROS), such as superoxide and hydroxyl radicals or singlet oxygen. ROS rapidly reacts with biological substrates, which initiates an apoptotic or necrotic response. This process eventually leads to oxidative damage and cell death. The intracellular localization of the photosensitizer activity is of great importance because mitochondrial damage generally leads to apoptosis, whereas plasma membrane damage induces necrosis [ 1 - 3 ] . Photofrin, one of the most widely used photosensitizers, is localized in the mitochondria due to its hydrophobicity and its affinity to the binding site on the mitochondrial membrane [ 4 ] . A frequently used drug in PDT is 5-aminolaevulinic acid (ALA). However, 5-ALA is not a photosensitizer, but a precursor of the endogenous photosensitizer protoporphyrin IX, which is a member of the heme synthesis pathway that occurs in the mitochondria [ 5 ] . PDT affects the tumor vasculature, where illumination and ROS production cause vessel shutdown and lead to tumor hypoxia [ 6 ] . PDT also affects the immune system [ 7 , 8 ] . The tissue selectivity of different photosensitizers is currently under investigation. Moreover, the laser irradiation restricted within the lesion area combined with the short lifespan of the emerging cytotoxic species ensures that phototoxic damage is mainly localized in the lesion with minimal inclusion of the surrounding tissues. The application mode of photosensitizers may be topical or systemic (oral or intravenous). Indications for PDT include cancers where the entire lesion is visible through an endoscope to enable laser irradiation. PDT has been applied for the treatment of skin cancer, surperficial esophageal cancer, lung cancer, and gastric cancer [ 9 , 10 ] . In addition, bladder and prostate cancers have been treated with PDT [ 11 – 13 ] . In this review, PDT effectiveness in treating gynecological cancers, such as ovarian cancer, cervical intraepithelial neoplasia (CIN), and vulvar intraepithelial neoplasia (VIN) is discussed. The available data on targeted and non-targeted treatment modes for breast cancer is also summarized. Photodynamic therapy mechanism, as explained in detail in the text.