Anti-Müllerian hormone: biology and role in endocrinology and cancers.

The presence of AMHR2 in the tissue is a crucial aspect of the modern approach to targeted oncological therapy using the anti-cancer properties of AMH. A promising direction for the use of AMHR2 in diagnostics and therapy is the application of conjugated anti-AMHR2 antibodies with the radioactive isotope zirconium ( 89 Zr) in the detection of intraperitoneal EC metastases and in radioimmunotherapy of EC with the radioactive isotopes lutetium ( 177 Lu) and bismuth ( 213 Bi) ( 136 ) ( Figure 6 ). In the tumor microenvironment, a low fucosylated antibody against AMHR2, murlentamab (GM102), switches the pro-cancer nature of tumor-associated macrophages (TAMs) towards the anti-cancer action by activating immunological mechanisms leading to the destruction of tumor cells ( 186 – 189 ) ( Figure 6 ). Initially, TAMs contribute to the tumor progression by producing anti-inflammatory chemokines. However, reprogrammed by GM102, they acquire the features of M1-type anti-cancer macrophages by stimulating cytotoxic T cells (CD8 + ), antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) ( 189 – 191 ). The promising effect of GM102 on AMHR2-expressing tumors was already reported in a preclinical study in cynomolgus monkeys using a xenograft of human ovarian cancer ( 192 ). GM102 used in phase I clinical trial in a group of women with ovarian cancer had an impact on the proportion of subsets of monocytes in peripheral blood ( 193 ). Then, in the first-in-class trial among 27 women with gynecological cancers expressing AMHR2, it was shown that GM102 is well tolerated at all doses and decreases the tumor growth rate in 47% of patients ( 194 ). This effect was achieved through the activation of monocytes, neutrophils and lymphocytes ( 194 ). The next first-in-class trial of GM102 with cisplatin and paclitaxel was conducted on the group of patients with ovarian, cervical and endometrial cancers. However, better response was noted for treatment combined with cisplatin and paclitaxel when compared with GM102 alone ( 195 ). No dose-related toxicity and only weak side effects related to applications of GM102 were observed. The activation of classical monocytes, T cells and neutrophils in blood was detected together with changes in TAMs ( 195 ). Phase II trial of GM102 alone or in combination with trifluridine/tipiracil (FTD/TPI) was conducted on patients with colorectal adenocarcinomas ( 196 ). Better response to treatment increased and was associated with a higher number of cancer cells with AMHR2 expression ( 196 ). Paired biopsies revealed the activation of tumor immune microenvironment (CD16 macrophage) and phagocytosis. GM102 together with FTD/TPI activated antigen-presenting cells (CD86) and CD8 + T cells ( 196 ). In peripheral blood, GM102 stimulated monocytes (CD69 + ) and neutrophils (CD64 + ) as a single factor or with FTD/TPI ( 126 ). Taking into account phase I and phase II clinical trials of patients with colorectal and ovarian cancer treated with GM102, it was shown that in the case of colorectal cancer the number of blood monocytes CD69 + increases, while the number of CD69 + activated-regulatory T cells decreases ( 189 ). Also, the blood concentration of two substances presented as critical immune modulators and survival predictors, such as the interferon-inducible chemokines CXCL (C-X-C motif chemokine ligand) 9 and 10, increases ( 189 , 197 ). Paired biopsies revealed that GM102 changes the proportion of macrophages in favor of cells engaged in the ADCC/ADCP process with activation of natural killer (NK) cells and CD8 + cells ( 189 ). In the case of ovarian cancer, the number of CD8 + T cells expressing inducible co-stimulator molecule increases ( 189 ). An experiment conducted in vitro with the culture of human ovarian cells with the presence of AMHR2 and microenvironment with TAMs showed that GM102 polarizes the CD4 + T cells towards T H (T helper) 1 cells and CD8 + T cells profile ( 189 ). Interestingly, in vitro GM102 positively cooperates with pembrolizumab, an anti-PDCD1 (programmed cell death 1) antibody, which is useful in cancers with microsatellite instability (Lynch syndrome) with profiling lymphocytes towards T H 1 cells ( 189 , 198 ). In the animal model, GM102 together with pembrolizumab promote changes observed in the ADCC/ADCP process. Thus, it may be advisable to combine the treatment of specific cancers (expressing AMHR2 and microsatellite instability) with these two agents ( 189 , 198 ) ( Figure 6 ). Apart from the development of tissues and organs as well as wound healing, cancers are the major cause of EMT ( 39 , 199 ). Theoretically, during EMT AMHR2 could be present on non-gynecological solid tumor cells. It was confirmed that AMHR2 is expressed in hepato-carcinomas (HCC), colorectal (CRC), non-small-cell lung (NSCLC) and renal cancer cells (RCC) ( 29 ). AMHR2 expression was also detected in melanoma and head and neck cancer cells. Interestingly, in NSCLC AMHR2 expression was more common in women (67%) than in men (30%) ( 29 ). The studies conducted in animal models comparing the efficacy of GM102 and standard treatment of HCC and CRC, sorafenib and irinotecan, respectively, revealed that GM102 has similar efficacy to sorafenib and irinotecan, but treatment with GM102 shows better tolerability ( 29 ) ( Figure 6 ). Not only the targeting of specific antibodies against AMHR2 in tumor tissue should be considered in future oncotherapy, as the anti-proliferative activity of AMH manifests in two aspects the influence on the cell cycle and the regulation of apoptosis. Thus, AMH plays a regulatory role in endometriosis cells and other gynecological neoplasms ( 25 – 27 , 30 – 32 ). AMHR2 is expressed in nearly 70% of human ovarian endometriomas cells ( 30 ). Other benign ovarian tumors express AMHR2 in approximately 45% of all cells ( 200 ). Following the addition of AMH to the culture of endometrial cells, the survival of those cells is significantly reduced to 68%, compared to the control samples ( 30 ). An increase in the percentage of cellular DNA from the G 0 G 1 and sub-G 0 G 1 phases indicates that AMH has an inhibitory effect on the cell cycle by suppressing cells in the G 1 phase of the cell cycle ( 30 ). Interestingly, AMH increases the level of the cyclin-dependent kinase (CDK) inhibitor p21, the Rb family factors p107 and p130 as well as the transcription factor E2F2 ( 30 ). On the other hand, the level of E2F1 decreases after AMH administration ( 30 ). Short peptides of cyclin binding domains of the proteins p21, p107 and p130 compete in binding to CDK2, causing its inhibition ( 30 , 201 , 202 ). E2F1 and E2F2 are transcription factors with a dual nature, since they promote the cell cycle progression but also regulate apoptosis and DNA repair ( 203 – 205 ). An increased level of the apoptosis-inducing factor (AIF), the active form of caspase 9, cleaved PARP (poly ADP-ribose polymerase) and a decreased level of caspase 3 after AMH addition to endometriosis cells may prove the apoptotic activity of AMH ( 30 ). However, it seems that the mechanism of the pro-apoptotic action of AMH is different in endometriosis and gynecological malignancies. In the ovarian cancer cell line OVCAR-8, AMH acts mainly through a mechanism that depends on the CDK inhibitor p16 ( 31 ). Increased expression of p16, p21 and E2F1 proteins as well as decreased levels of p130 have been demonstrated ( 31 ). One of the most convincing evidence of the anti-tumor activity of AMH is its additive effect on ovarian serous cancer with paclitaxel and cisplatin and its synergistic effect with rapamycin and doxorubicin ( 28 ) ( Figure 6 ). Also, exogenous AMH concentrations beyond the physiological values reduce the cell survival of the high-grade serous adenocarcinoma of the ovary ( 206 ) ( Figure 7 ) Taken together, recombinant human AMH inhibits cell colony growth in most advanced ovarian cancer cell lines ( 207 ) ( Figure 7 ). Effect of different AMH concentrations on ovarian cancer cells. The opposite effect of physiological and supraphysiological AMH concentration on the survival of the ovarian cancer cells. In physiological concentration, AMH works through ALK2 recruitment thus increasing the survival rate of the cell colonies of the high serous ovarian adenocarcinoma. Meanwhile, supraphysiological concentration of AMH activates ALK3 resulting in apoptosis of ovarian cancer cells. Physiological concentrations of endogenous AMH play a surprising role in the context of oncology as they increase the survival rate of the cell colonies of the high serous adenocarcinoma of the ovary tumor, sex cord-stromal tumor and the granulosa cell tumor ( 206 ) ( Figures 6 , 7 ). This mechanism involves inducing phosphorylation of the PI3K/AKT/mTOR pathway through ALK2 recruitment ( 207 ) ( Figure 7 ). Even partial AMH depletion or inhibition by specific antibodies reduces the viability of cells of ovarian cancers, decreasing phosphorylation of the PI3K/AKT/mTOR cascade and increasing PARP and caspase 3 cleavage ( 207 ). However, a supraphysiological concentration of exogenous AMH engages the ALK3 pathway and decreases the survival of ovarian cancer cells ( 208 ) ( Figure 7 ). Similarly, to the phenomenon described above, the physiological and supraphysiological AMH concentrations affect the survival of Sertoli cells ( 209 ). The use of bispecific antibodies against ALK2 and AMHR2 appears to be more potent in the context of anti-cancer activity than bispecific antibodies ALK3 and AMHR2 ( 208 ) ( Figure 6 ). Apart from ovarian cancer, EC, the most common neoplasm of the female reproductive organs, also appears to be a suitable target for the use of AMH ( 25 , 45 ). In the cell line AN3CA of EC, the inhibitory effect of AMH on proliferation is confirmed by increased levels of p130 and p107 ( 25 ) ( Figure 8 ). Incubation of EC cells with AMH results in a reduced levels of the transcription factor E2F1, yet it does not affect the level of E2F2, E2F3 or E2F4 ( 25 ). Moreover, AMHR2 is present in all types of histopathological EC ( 33 ). AMHR2 is also found in all EC stages according to FIGO classification ( 33 ). The expression of AMHR2 in EC is not influenced by BMI, the patient’s age, their parity, the mass of newborns, breastfeeding time, number of miscarriages, number of menstrual years, hormonal status, use of hormonal replacement therapy or the presence of arterial hypertension. The only factor reducing AMHR2 gene expression in EC is type 2 diabetes ( 33 ). Interestingly, women with type 1 diabetes also have decreased AMH levels compared to non-diabetic women ( 210 ). Crosstalk between AMH and endometrial cancer. The putative interaction between local endometrial expression of AMH and ovarian source of AMH on the development of EC. AMH from two sources acting simultaneously: the endometrium (auto/paracrine activity) and the ovaries (endocrine activity) protects against EC. When endometrial origin AMH is not produced even in the presence of ovarian origin AMH, the disease may develop. When there is a lack of ovarian source AMH, but the endometrium still produces AMH, the EC is limited to a maximal ½ thickness of the myometrium. All figures were created with BioRender.com . Another issue is the unclear role of intracellular AMH expression in EC. Among the different types of EC, the presence of AMH in EC tissue was confirmed in approximately 10% of cases, diagnosed only after the menopause and never before this moment in female life ( 22 ). This applies to EC with a good prognosis well (G1) and moderately (G2) differentiated endometroid adenocarcinoma and clear cell cancer that is characterized by poor prognosis ( 22 ). In the latter type of EC, in every case with AMH presence, the neoplastic process is always limited to a maximal ½ thickness of the myometrium ( 22 ) ( Figure 8 ) A long mean period of lactation (more than 10 months) and a period of sex-hormone activity (time from the first to the last menstruation) longer than 40 years, have a positive effect on the expression of AMH in EC ( 22 ). Neither age nor BMI, parity, the mass of the newborn, total breastfeeding time, tumor stage or comorbidities like chronic hypertension or type 2 diabetes affects the expression of AMH in EC ( 22 ). Perhaps the intracellular presence of AMH limits the expansion of EC with a poor prognosis ( Figure 8 ). In the C33A cell line of cervical cancer, the pro-apoptotic effect of AMH is manifested by an increase in the levels of p16, p130, p107 and E2F1 proteins ( 32 ) ( Figure 6 ). AMH also inhibits the growth of the cell line A431 of human vulvar epidermoid carcinoma ( 211 ) ( Figure 6 ). AMH reducing effect on lung metastases of the human eyeball malignant melanoma cell line OM431 was demonstrated in the mouse model ( Figure 6 ). On the other hand, AMH does not inhibit the growth of cell lines of human bladder transitional cell papilloma (RT-4) and human hepatocellular carcinoma (Hep 3B) ( 211 ). AMHR2 expression has been also confirmed in cells originating from healthy breast and prostate tissue, breast fibroadenomas and various breast and prostate cancers as well as their cell lines ( 26 , 27 , 212 ). During pregnancy, epithelial cells of rat mammary ducts proliferate intensively and undergo apoptosis once lactation has finished ( 26 ). This process depends, among other factors, on AMH ( Figure 4 ). The Amhr2 gene expression in the rat mammary gland decreases during pregnancy, is at its lowest during the lactation period and increases once again shortly after weaning ( 26 ). The growth of the proximal part of the murine prostate gland occurs in the early stages of development and is dependent on androgens to a limited extent ( 213 , 214 ). Expansion of the distal part of the prostate takes place after the 15 th day of embryonic development, when the AMH level declines ( 213 , 214 ). This appears to be an androgen-dependent process. AMH inhibits testosterone synthesis in vitro and in vivo by reducing the expression of the CYP17A1 (cytochrome P450 family 17 subfamily A member 1) gene, which encodes for a 17α-hydroxylase that converts progesterone to androstenedione ( 34 , 58 , 63 , 215 ). In AMHR2 signal transduction in BC and PC, three distinct subtypes of type I receptors for AMH are involved ALK2, ALK3 and ALK6 ( 26 , 27 ) AMH inhibits the growth of BC cells that express ESRs ( e.g. , T47D) and those that do not ( e.g. , MDA-MB-231) ( 26 ) ( Figure 6 ). Flow cytometry revealed an increase in the number of cells in the G 1 phase by 10-16%, compared to cells that were not incubated with AMH or treated with biologically inactive AMH ( 26 , 27 ). In addition to disrupting the cell cycle, AMH induces apoptosis in T47D cells ( 26 ) ( Figure 8 ). There was a 3-fold increase in the concentration of caspase 3 and a 3-fold increase in the early apoptosis marker annexin V, compared to the cells there were not treated with AMH ( 26 , 27 ). In AMH-treated BC (T47D) and PC- LNCaP (cells of androgen-sensitive human prostate adenocarcinoma) cells, the NFκB signal transduction pathway is activated ( 27 , 216 ). In addition to AMH, this pathway is also activated also by free radicals, UV radiation, antigens and pro-inflammatory cytokines like TNF (tumor necrosis factor) and IL1β (interleukin 1β) ( 217 ). In both BC and PC, p50/p65 heterodimers are induced. However, p65/p65 homodimers are activated only in the BC line, and p50/p50 are present only in the PC cell line. In contrast, the biologically inactive, non-cleaved form of AMH does not activate the NFκB pathway ( 26 , 40 ). T47D and LNCaP cell lines treated with AMH show induction of the RGS1 (regulator of G protein signaling 1) gene expression ( 26 , 27 ). As the promoter of the RGS1 gene has binding sites for both NFκB and p53, it plays a regulatory role in the context of the cell cycle, differentiation and stress response ( 218 ). Additionally, selective expression of RGS1 splice variants were found in T47D cells after incubation with AMH ( 26 ). There was no expression of variant RGSL (responsible for the survival of the cell) and anti-apoptotic NFκB-induced factors, such as A20 and c-IAP2 ( 26 ). Cells of the ESR-negative BC cell line MDA-MB-231 react similarly to incubation with AMH. The NFκB pathway is activated, with the presence of the p50 and p65 subunits and the RGS1 gene. Transcripts of both splice variants: RGS1S and RGS1L have been reported, but biologically relevant levels are reached only by RGS1S , resulting in cell cycle inhibition in approximately 50% ( 26 ). Interestingly, only proper regulation of NFκB with an optimal degree of inflammation or apoptosis, including apoptosis induced by anti-cancer drugs, leads to the desired effect from the point of view of the organism’s interests ( 219 , 220 ). Dysregulation of NFκB signaling leads to cancer, metastasis, chronic inflammation or autoimmune diseases ( 219 ). Upregulation of NFκB, which happens in various cancers, is related to the presence of cytokines in the tumor microenvironment that activate the NFκB pathway leading to an increase in anti-apoptotic molecules ( 221 , 222 ). Understanding the effects of NFκB in different circumstances makes it possible to properly interpret the results of activation and inhibition of the NFκB pathway in different types of BC. Mammogenesis and lactogenesis are regulated, among others, by sex hormones and modulators of their signals ( 223 ). One of them is RANKL (receptor activator of nuclear factor kappa beta ligand) ( 223 – 225 ). Excessive exposure of progesterone receptor (PGR) positive cells to gestagens causes overproduction of RANKL, which subsequently activates RANKL receptor in PGR negative cells ( 223 , 226 ). Ultimately, this leads to upregulation of NFκB, downregulation of the CDK inhibitor p21 and consequently to cancerous transformation of the breast tissue ( 227 – 230 ). The usefulness of the human monoclonal antibody denosumab in breast cancer, which blocks RANKL, has already been evaluated ( 231 ). The above-mentioned pro-apoptotic response of BC cells to AMH, activating NFκB and then the synthesis of RGS1 S, would be limited by excess estrogens, which reduce the density of AMHR2 preventing the beneficial activity of AMH ( 232 ). Taken together, there is an intensive crosstalk between sex hormones and BC. Despite anti-cancer activity of AMH and the fact that the anti-proliferative effect of AMH on the mammary gland is gradually reduced during physiological pregnancy to ensure proper lactation, there is no clear evidence that increased or decreased plasma AMH concentrations have a significant relationship with BC ( 161 , 162 , 216 , 232 ). The literature on the subject is inconsistent and links lower AMH concentration with a higher risk of BC as well as a positive correlation of AMH concentration with BC, and on the other hand, the lack of the relationship or the correspondence of BC only with the lowest and highest quartiles of AMH level ( 233 – 236 ). The relationship of AMH with BC caused by BRCA1 / BRCA2 (BRCA1/2 DNA repair associated) mutation is also described differently in various studies ( 237 , 238 ). In conclusion, it appears that plasma AMH concentrations in patients, even with PCOS, are significantly lower than those used in the studies describing the effect of AMH on the BC tissue in in vitro conditions ( 232 ). Thus, it is difficult to reach a final statement on the influence of AMH serum levels on BC ( 232 ). It is worth mentioning the significant potential utility of AMH level assessment in the context of ovarian function loss after chemotherapy for BC. Women with BC who are over 40 years of age and who have undergone anthracycline- and taxane-based chemotherapy and have undetectable AMH levels after 6 months of treatment have very likely irreversibly lost ovarian function ( 239 ). Analysis of AMH levels in this group of patients would allow avoiding therapy with a GnRH agonist aimed at inhibiting estradiol production, which is associated with serious side effects ( 239 ). There is also another connection between RANKL, NFκB and AMH. AMH inhibits RANKL-dependent osteoclast differentiation by preventing the degradation of the IκB (inhibitor of nuclear factor kappa B) protein ( 240 ). Under the influence of AMH, the expression of osteoclast differentiation markers ( FOS , NFATC1 , ACP5 ) is reduced ( 240 ) ( Figure 4 ). However, it does not affect osteoblast differentiation dependent on BMP2, which is another member of the TGFβ family ( 240 ). There is no expression of AMH in osteoclasts and osteoblasts ( 240 ). Taking into account the inhibition of osteoclast differentiation, the usefulness of AMH in premenopausal and perimenopausal age as a marker of low bone mineral density is considered ( 241 – 243 ). Therefore, there may be a functional crosstalk between vitamin D and AMH. The serum level of 25-hydroxyvitamin D 3 is inversely proportional to the concentration of AMH and positively correlated with SHBG. However, this applies mainly to women with PCOS ( 244 ) ( Figure 5 ). On the other hand, vitamin D 3 supplementation in normo-ovulatory women and women with reduced OR increases the AMH level, having a positive effect on the AMH gene expression, without affecting the number of antral follicles ( 245 , 246 ).

AMH, also known as a Müllerian inhibiting factor or Müllerian inhibiting substance, has a mani-fold and complex effect on the development and the function of a variety of human tissues. AMH is a glycoprotein belonging to the transforming growth factor beta (TGFβ) superfamily ( 1 ). This family of signaling proteins includes 32 other peptides, such as activins, inhibin A and B, bone morphogenic factors (BMPs) and growth differentiation factors (GDFs) like myostatin ( 2 , 3 ). The AMH protein composed of a N-terminal prodomain and a C-terminal growth factor (GF) domain ( Figure 1 ), which is encoded by a gene consisting of 5 exons and 4 introns, located on the short arm of human chromosome 19 ( 4 ). The regulatory regions of the AMH gene contain binding sites for multitude of transcription factors, such as SOX9 (SRY-box transcription factor 9) and NFκB (nuclear factor kappa B) ( 5 , 6 ). Principles of AMH signaling. Dimeric AMH peptides activate the receptor AMHR2, which then together with ALKs activate the regulatory SMAD proteins 1, 5 and 8. The latter translocate to the nucleus and act together with SMAD4 and other supporting transcription factors (TFs) as regulators of the expression of AMH target genes. There are seven type 1 and five type 2 receptors for all 33 members of TGFβ superfamily ( 5 , 7 ). AMH is binds exclusively to the type 2 receptor - AMHR2 ( 8 ). Therefore, only cells expressing AMHR2 are able to respond to direct AMH stimulation ( 9 ). The AMHR2 protein is encoded by a gene located on the long arm of human chromosome 12, comprising 11 exons and 10 introns. The first three exons encode the extracellular domain, the fourth exon the transmembrane domain, while the remaining seven exons encode the intracellular serine/threonine kinase domain ( 10 ). The AMHR2 gene responds to similar regulatory signals as the AMH gene ( 5 ). Due to the orientation of the N-terminus to the extracellular space, AMHR2 is classified as a type 1 membrane protein ( 11 ). After ligand binding, AMHR2 acts as a transmembrane serine-threonine kinase and activates AMH type 1 receptors ( 5 , 11 , 12 ) ( Figure 1 ). The latter are signal enhancement molecules, which also exhibit serine-threonine kinase activity. The AMH signaling pathway uses three types of activin receptor-like kinases (ALKs), ALK2, ALK3, ALK6, in different types of tissues, with ALK2 and ALK3 acting as positive regulators in signal transduction and ALK6 mainly as an inhibitor ( 5 , 12 – 14 ). The AMH-AMHR2-ALK complex phosphorylates regulatory members of the SMAD (SMA- and MAD-related protein) family, SMAD 1, 5 and 8, which after translocating to the nucleus, they regulate together with SMAD4 and other supporting transcription factors the expression of AMH target genes ( 3 , 5 , 12 , 15 , 16 ). Multiple studies indicated that AMH is expressed in Sertoli cells of the testes, granulosa cells (GCs) of the ovaries (preantral and small antral follicles), the endometrium of women in the reproductive age, motoneurons, gonadotropin-releasing hormone (GnRH) neurons and the hippocampus as well as in endometrial cancer (EC), sex cord-stromal tumors and granulosa cell tumors ( 17 – 24 ). In addition, traces of AMH are found in skeletal muscles, the sciatic nerve, the spinal cord and the mouse brain ( 23 ). In vitro studies and animal models revealed that AMH induces cell cycle inhibition and apoptosis in some cancer cell lines ( 25 – 27 ). Moreover, AMH also shows an additive or synergistic effect in combination with typical chemotherapeutic agents in serous ovarian cancer cells that express AMHR2 ( 28 ). A large number of reports found AMHR2 expression in cells of the Müllerian ducts, ovarian follicles (preantral and small antral), the pituitary gland, the hypothalamus, the endometrium, the adrenal glands, lactiferous ducts, Leydig cells, the prostate, motor neurons, the hippocampus and some of the human cancers that include endometrial, ovarian, prostate, breast, and cervix ( 21 , 23 , 25 – 27 , 29 – 36 ). Based on the epithelial-mesenchymal transition (EMT) process, AMHR2 could be expressed also in some solid tumors ( 29 , 37 – 39 ). So far, AMHR2 expression has been confirmed, among others, in non-small cell lung cancer and ocular melanoma ( 29 , 40 ). The publicly available dataset ( https://gtexportal.org ) of the GTEx (Genotype-Tissue Expression) project is the gold standard for comparing tissue-specific gene expression ( 41 ). Based on 54 tissues obtained from 948 post-mortem donors the expression of the AMH gene is highest in testis, pituitary gland and cerebellum, but most other investigated tissues also show some expression of the gene ( Figure 2A ). In contrast, the expression of the AMHR2 gene is far more restricted to adrenal gland, ovary, testes, spleen and pancreas ( Figure 2B ). Gene expression based on data of the GTEx project. Expression of the genes AMH (A) and AMHR2 (B) in 54 different human tissues. Normalized RNA sequencing data are shown in TPM (transcripts per million), where all isoforms were collapsed into a single gene. Box plots display the median as well as 25 th and 75 th percentiles. Points indicate outliers that are 1.5 times above or below interquartile range. Data are based on GTEx analysis release V8 (dbGaP Accession phs000424.v8.p2). The serum concentration of AMH in healthy women of the reproductive age is in the range of 1.5-4.0 ng/mL ( 42 ). Tumors originating from sex cord cells and ovarian GCs produce AMH and in those cases the serum concentration often exceeds the reference value up to 1000 times ( 17 , 43 ) ( Figure 3 ). For example, a AMH concentration of 3205 ng/mL was found in a patient diagnosed with metastatic sex cord tumor ( 17 ). It is worth emphasizing here that there are several commercial laboratory tests (kits) for assessing AMH concentration. They differ significantly in sensitivity, intra-assay and inter-assay variation coefficient ( 44 ). Hence, when interpreting AMH test results in different studies or meta-analyses, it is worth considering which ELISA (enzyme-linked immunosorbent assay) kit was used ( 44 ). This is also clinically important, for example when comparing AMH rate of change. It would be best to do this with the same laboratory test. Decreasing AMH levels are the evidence of the effectiveness of treatment in this type of cases ( Figure 3 ). Interestingly, increased levels of AMH do not cause any toxic effects ( 45 ). For this reason, it is postulated that AMH has a remarkably beneficial profile and may be useful in the treatment of tumors expressing AMHR2 ( 45 ). The aim of this narrative review is to systematize knowledge about the expression of AMH and AMHR2 in various tissues, in order to gather information on the mechanism of action of AMH in physiological and various medical conditions, especially concerning malignant tumors. The utility of the assessment of AMH concentration on the different fields of medicine. As the AMH concentration increases 2-12 times in the PCOS women group, its level should be taken into account while diagnosing PCOS. Based on mathematical modeling of the decreasing AMH levels with age, a concentration below 0.1 ng/mL means menopause. The AMH level enables a correct diagnosis between gonadal dysgenesis and androgen insensitivity syndrome in 46, XY individuals with incorrect appearance of their genitalia. AMH concentration facilitates diagnostics and helps evaluate the treatment of the cancers producing AMH. As AMH level is the best marker of ovarian reserve, it should be assessed before and after oncotherapy, before cryopreservation and after retransplantation of ovarian tissue. Moreover, in the infertility treatment clinic the AMH level is useful as the factor evaluating the chance of live birth and allowing the use of the appropriate dose of recombinant FSH.

A literature review on the discussed topic was conducted by searching for keywords/phrases in publicly available databases as: PubMed, Google Scholar, ScienceDirect. Those keywords included: “anti-Müllerian hormone receptor type 2,” “AMHRII” or “AMHR2,” “anti-Müllerian hormone receptor type 1, “anti-Müllerian hormone,” “AMH,” “MIS”, “anti-Müllerian hormone and cancer,” “anti-Müllerian hormone and PCOS,” “anti-Müllerian hormone and endometriosis,” “anti-Müllerian hormone and ovarian function,” “anti-Müllerian hormone and pituitary gland function” “anti-Müllerian hormone and hypothalamus”, “anti-Müllerian hormone and artificial reproductive technology”, “anti-Müllerian hormone and menopause”. Only articles in English and Polish were taken into account. Additionally, publications were searched for manually on the basis of references provided in the selected papers. The data analyzed came from published articles and a chapter of one book regarding the main theme and related topics.

In summary, the mechanism of action of AMH as well as involved the signal transduction pathways are tissue-specific. Despite numerous studies and the knowledge gained, further investigations concerning this glycoprotein are needed, since the full potential of AMH is still obscure. However, the modulating effect of AMH on the recruitment of ovarian follicles and the effect of its concentration on the result of IVF is of great interest to fertility specialists. Also, being aware of its important role in the process of the cell cycle inhibition and inducing apoptosis, AMH and its receptor AMHR2 raise great hopes for future applications in oncology.