{"paper_id":"b0782eb2-614a-4e93-81eb-8e6d533d6555","body_text":"Endometriosis, the presence of endometrial tissue outside of the uterine\ncavity, is a prominent estrogen-dependent gynecological disease that incites chronic\npain in women of reproductive age. This tissue is generally morphologically normal\nbut abnormally located, with common ectopic sites including the fallopian tubes,\novaries, and the rectouterine pouch. More far-reaching, endometrial implants have\nalso been visualized along several different sites in the peritoneal cavity as well\nas within the lungs [ 1 ]. Over 6% of women in\nthe United States are estimated to have endometriosis [ 2 ], with approximately 176 million women across the world\nbeing affected by this gynecological disease [ 3 ]. Risk factors for endometriosis include, but are not limited to,\nfamily history, nulliparity, early age of onset for menstruation, heavy\nmenstruation, and outflow tract obstruction. As the mean average age of first\npregnancy increases, in the United States, the incidence of endometriosis has also\nincreased [ 4 ]. The incidence of diagnosis\npeaks in the early 30s [ 5 ] with the surgical\ndiagnosis occurring approximately 4.6 years after the first reported symptoms [ 6 ].\nIn 1927, Sampson described endometriosis-associated ovarian cancers, marking\nthe first association between endometriosis and neoplastic tissue [ 7 ]. The endometriosis-mediated molecular pathways have\nbeen difficult to elucidate. However, over the past several years, mounting evidence\nsuggests an endometriosis molecular fingerprint that can be linked to certain benign\nand malignant neoplasia. This review will focus on reviewing the putative molecular\nfingerprint that drives endometriosis-associated malignant neoplasia.\n\nThe specific molecular mechanism(s) mediating the generation of di novo\nendometriotic lesions and tumorigenesis arising within those lesions has not been\nclearly elucidated. One of the earliest etiologic hypotheses was described as the\nretrograde transport theory, suggesting that endometrial tissue is transported via\nthe fallopian tubes into the abdominopelvic cavity during shedding of menstruation\n[ 8 ], thereby leading to the ectopic foci\nof the endometrial lesions. Evidence of retrograde menstruation is seen in 76%-90%\nof women. Although not all women experience retrograde menstruation, women who do\nare more likely to develop endometriosis, and this likelihood increases further with\nthe concurrent presence of tubal obstruction [ 9 ,  10 ].\nMolecular pathways offer further support for the retrograde transport theory\nof endometriosis. When endometrial epithelial cells reflux into the abdominopelvic\ncavity, cytokines (e.g. IL-1b, TNFa, and IL-6) released from invading macrophages in\nturn trigger a Th1 lymphocyte-mediated acute inflammatory response [ 11 – 14 ], and\nIL-18, released in the peritoneum of women with endometriosis, triggers a Th2\nlymphocyte response. The aforementioned pro-inflammatory pathways induce COX2 gene\nexpression via the MAPK pathway, thereby releasing prostaglandins which results in\npain [ 15 ]. The ectopic endometriotic foci are\nsignificantly more responsive than endometrial stroma, suggesting why patients with\nendometriosis may experience severe pain out of proportion to the size of the\nendometriotic implants [ 15 ]. Other data have\ndemonstrated that in women with endometriosis, there is decreased IL-19 and IL-22,\nwith levels of the cytokines inversely associated to experienced pain [ 16 ]. This indicates the key role of these\ninterleukins in the clinical symptoms of endometriosis. Separately, ERK1 and ERK2\nwere both found to be activated and have increased levels of phosphorylation in\nwomen compared to women without endometriosis [ 17 ,  18 ]. Given these enzymes are\ninvolved in cellular proliferation, this finding may indicate a potential link\nbetween ectopic endometrial tissue and malignancy.\nA recent large systemic study comparing differentially expressed genes\nassociated with endometriosis successfully identified 39 overlapping genes\ncorrelated with tumor progression in women with endometriosis. Of those genes, two\nwere related to endometriosis: PGR and EGR1 [ 17 ]. PGR, a progesterone receptor gene expressed in uterine lining cell\nproliferation [ 19 ], and EGR1, an estrogen\nreceptor gene, were found in all four of the female cancers, ovarian, endometrial,\ncervical, and breast, with a mutation rate of 4%. It is reasonable to suggest that\nmutations in these receptors are gain of function, potentially allowing for these\nreceptors to become hypersensitive to estrogen and progesterone. Given that these\nwere the only two endometriosis-related genes to be found mutated in all four types\nof cancers which exclusively affect women (with the exception of breast cancer), we\nbelieve this information can be utilized to find a therapy to limit\nendometriosis-related malignancies.\nC3aR1 is a linker gene found in both endometriosis-related literature and\none of the gene expression profiles. However, there is no previous evidence or\nassociation of this linker gene with endometriosis. C3aR1 is a g-protein coupled\nreceptor for the chemotaxis C3a of the complement system, which ultimately plays a\nrole in the inflammatory response. Previously, C3aR1 was potentially thought to be a\nproto-oncogene as this specific receptor is downregulated in melanoma and testicular\ngerm cell tumor cells, leading to a decreased neutrophil and CD4 T-cell response\n[ 20 ,  21 ] and allowing for unchecked tumor growth. In analysis, C3aR1 was\nmutated in 3% of samples, with the most common mutations occurring in breast cancer,\nfollowed by ovarian cancer [ 17 ] suggesting\nthat mutations in this gene may lead to malignant transformation of endometriosis.\nAlthough not previously thought to be associated with endometriosis or gynecological\nmalignancy, C3aR1 may be a critical link in regard to determining the molecular\npathway of endometriosis and its relation to malignancy, and thus should be studied\nin the future.\nSOX-17, a transcription factor, has been recently implicated in the\nconnection between endometriosis and women’s cancer. SOX-17 normally inhibits\nb-catenin and MALM3 [ 22 ], acting as a tumor\nsuppressor to antagonize the WNT signaling pathway on cellular growth. Therefore,\nmutations in SOX-17 allow for genetic transcription and translation leading to\ncellular growth. In the aforementioned large study, SOX-17 had the highest\nalteration rate (5%) of all the endometriosis genes related to endometrial cancer\n[ 17 ]. Non-mutated SOX-17 was decreased in\nseveral tumors, further suggesting its role as a tumor suppressor [ 23 – 26 ]. Low\nexpression of SOX-17 was also associated with poorer outcomes as tumors with\ndecreased levels of SOX-17 were higher grade and advanced stage [ 27 ]. More analysis is needed to determine SOX-17’s\nspecific relationship to endometriosis-related neoplasia, but early studies show\nthat abnormalities with this transcription factor strongly correlate with\nmalignancy.\nPTEN, a tumor suppressor gene involved with cell cycle regulation, can be\nmapped to locus 10q23-26 [ 28 ]. In a recent\nstudy, PCR analysis showed 34% of women with endometriosis had a frameshift mutation\nin the PTEN gene, compared to 0% in controls [ 29 ]. Immunohistochemistry also indicated decreased expression of PTEN in\nwomen with endometriosis compared to controls [ 29 ]. In mice models, knockout PTEN in the surface epithelium of ovaries\ninduced the production of endometriotic lesions, further suggesting the importance\nof PTEN [ 30 ]. Other experiments exemplified\nthat increasing the amount of PTEN in endometrial cells using vectors leads to\nincreased apoptosis of these cells by preventing angiogenesis through VEGF. This\nreplicated the normal endometrial environment and prevented the ectopic distribution\nof endometrial tissue [ 31 ].\nARID1a is a tumor suppressor gene that encodes for BAF250a, a gene in the\nSWI-SNF chromatin remodeling complex [ 32 ].\nBAF250a is heavily involved with gene regulation regarding transcription activation\nand repression. In one study, mutations and deletions of ARID1a were found to be in\n46% of ovarian clear cell carcinoma (OCCC) and 30% of endometrioid adenocarcinoma\n(EAOC), both of which are associated with endometriosis. Interestingly, ARID1a\nmutations were not found in high grade serous ovarian cancer [ 32 ], a neoplasia not related to endometriosis. A separate\nstudy found that endometrial implants and OCCC shared common ARID1a mutations [ 33 ]. Chene et al discovered that in EAOC or\ncontiguous endometriosis patients with decreased expression of BAF250a, there were\nincreased levels of certain markers such as pAKT and BAX and decreased levels of\nBCL2, compared to patients with benign endometriosis [ 34 ]. Ultimately, even with the potential connections\nbetween ARID1a and BAF250a to endometriosis and malignancy, other studies have\nindicated that mutations in these genes and proteins alone do not cause cancer and\ncan be found in typical endometriosis implants that do not progress to cancer [ 35 ,  36 ].\nTherefore, it is important to continue to study ARID1a’s impact on this\nmolecular fingerprint to further elucidate and clarify its involvement.\n\nEndometriosis features several clinical stigmata that may be associated with\nsevere pain in a subset of women of reproductive age. These clinical symptoms\ninclude but are not limited to dysmenorrhea, dyspareunia, and dyschezia. Patients\noften describe cyclical pelvic pain that intensifies prior to the onset of menses.\nDysmenorrhea is the most common self-reported symptom in women with both\nlaparoscopically diagnosed and histologically diagnosed endometriosis [ 37 – 39 ]. The peri-menstrual shedding of the ectopic lining results in\nlocalized inflammation and pain. Many women will also experience chronic pain as a\nresult of ectopic adhesions in the abdominopelvic cavity. In addition, a significant\npercentage of women will report infertility. The American College of Obstetricians\nand Gynecologists has suggested that endometriosis is detected unexpectedly in\n20-50% of all women undergoing fertility treatment who do not have complaints of\nmenstrual pain [ 40 ]. Infertility due to\nendometriosis may be due to the result of chronic inflammation, distortion of the\npelvic cavity, obstruction of the fallopian tubes with ectopic implants, and\nanovulation.\n\nThe mainstay of diagnosis is direct visualization and biopsy of ectopic\nlesions (e.g. laparoscopy) [ 41 ,  42 ]. However, there are drawbacks associated\nwith this type of diagnosis. Surgical procedures are invasive and associated with\nboth cost burden to the patient and the potential for adhesion formation. Up to 25%\nof lesions elude the surgeon due to the heterogenous phenotypical presentation of\nendometrioid lesions in the peritoneal cavity [ 43 ]. Thus often it is the medical history and physical exam that are\nused for diagnosis in the outpatient setting. However, the variability of clinical\npresentation has made the accuracy of diagnosing endometriosis through physical exam\ndifficult [ 42 ]. The identification of\nspecific biomarkers will improve the accuracy of the diagnosis of endometriosis.\nUnfortunately, no current biomarkers exist [ 44 ]. Given that CA-125 is not specific, its utility as a screening tool\nhas been questioned, but recent reports have proposed that the combination of CA-125\nand HE-4 (human epidydimal protein) may be of use in the future [ 45 ].\n\nCancer Antigen-125 (CA-125) is a traditional biomarker that originates from\nthe coelomic epithelia of the uterus, fallopian tubes, and ovaries in the pelvic\ncavity [ 46 ]. This biomarker has been\nassociated with ovarian epithelial cancers [ 47 ] and found to be elevated in greater than 80% of ovarian epithelial\ntumors [ 48 ]. Recently, increased levels of\nCA-125 have been linked with endometriosis, with a study showing women diagnosed\nwith biopsy-proven endometriosis had higher levels of CA-125 during menstruation\ncompared to a control group of women without endometriosis [ 49 ,  50 ].\nFurthermore, a positive association between advanced stages of endometriosis\nand elevated CA-125 in the peritoneal fluid has been reported [ 49 ,  50 ]. CA-125\nlevels > 30u/mL can be used as rule-in criteria for diagnosis [ 51 ]. It is uncommon for Ca-125 to reach above\n100u/mL in women with endometriosis [ 52 ], but\ncan be elevated as high as 10,000u/mL in cases of endometrioma rupture [ 48 ] or when the omentum is involved [ 53 ,  45 ].\nIt is believed that ectopic endometrial implantation in the peritoneal cavity\nreleases higher levels of CA-125, resulting in levels above 100u/mL [ 54 ]. A case study published serum CA-125 levels to be at\n6484 u/mL after palpation of an adnexal mass that was biopsy confirmed endometriosis\n[ 45 ]. Ectopic endometrial glands were\nfound in the, supporting the argument that peritoneal mesothelial cells can shed\nincreased levels of the glycoprotein. A separate case study that also included\nomental ectopic endometrial implants had markedly elevated levels of CA-125 [ 53 ], further suggesting that the increased\nsurface area of soft tissue in the peritoneal cavity may also be responsible for the\nseverely elevated CA-125 levels [ 45 ,  53 ]. The correlation between CA-125 and\nendometriosis demonstrates that CA-125 can be utilized when diagnosing endometriosis\nand must be considered in the differential diagnosis when an adnexal mass is\npalpated on rectal or vaginal exam. However, since CA-125 can be elevated in\nphysiologic states, its efficacy in diagnosing and monitoring malignant ovarian\nepithelial neoplasms is reduced. Due to the non-specific nature of CA-125, as it is\nalso found in other malignancies such as colon cancer or pancreatic cancer, its use\nwith endometriosis should be accompanied by the patient’s clinical history,\nphysical exam, and visual diagnosis.\nThe specificity of CA-125 levels is enhanced when evaluated in coordination\nwith HE-4 levels. Khodaverdi et al noted that elevated CA-125 and normal HE-4 can be\nindicative of endometrioma. [ 45 ]. Generally,\nHE-4 is elevated in malignancy [ 55 ] and has\nbeen shown to be normal in the case of an endometrioma [ 45 ]. Therefore, although CA-125 in itself may not be of\nuse to help identify endometriomas, the combined use of CA-125 and HE-4 may be key\nto effectively differentiating ovarian malignancies and endometriosis in the\nfuture.\n\nDeep infiltrating endometriosis (DIE), a type of endometriosis defined by\nectopic lesions penetrating >5mm into local peritoneal epithelium, is\nstrongly associated with pelvic pain and dysmenorrhea [ 56 ,  57 ]. These\nsymptoms are contingent upon the severity of adnexal adhesions and the presence of\ninfiltration into the vaginal or rectal canal [ 58 ]. This subtype of endometriosis differs from standard endometriosis\nas DIE invades the peritoneal cavity and can distort abdominopelvic structures,\nwhereas superficial endometriosis remains in the epithelia of the cavity. The most\ncommon form of DIE is associated with undifferentiated endometrial glandular pattern\n[ 59 ].\nDIE is associated with several somatic mutations: ARID1A, PIK3CA, KRAS, and\nPPP2R1A. These mutations have been correlated with other endometrial related cancer,\nbut current data indicates there is no association with malignancy or malignant\ntransduction. This suggests an intrinsic characteristic of the mutations of this\nbenign subtype of gynecological disease [ 60 ].\nInterestingly, due to its invasive habits and association with certain genetic\nmutations, many experts have called to characterize DIE itself as a neoplasm. More\nresearch is needed to better understand the molecular behavior of DIE [ 61 ].\n\nAtypical endometriosis, or endometriosis with dysplastic characteristics,\nwas first described in 1988 [ 62 ]. It is\nbelieved that repetitive damage and inflammation in ectopic endometrial foci result\nin the development of atypical endometriosis and eventually into endometriosis\nassociated ovarian neoplasms [ 63 ]. Atypical\nendometriosis was found in 36% of OCCC and in 23% of endometrial associated\nadenocarcinoma with direct progression into EAOC, suggesting the potential for\nimproved overall survival and mortality rates of EAOC with enhanced detection of\natypical endometriosis [ 64 ,  65 ]. The chronological progression of atypical\nendometriosis into EAOC is similar to that of atypical endometrial hyperplasia, thus\ndemonstrating its function as premalignant marker [ 66 ].\n\nAlthough risk of malignancy arising from ectopic endometrial tissue is\nrelatively low, there are known types of gynecological malignancies shown to arise\nfrom endometriosis precursors. OCCC and EAOC of the ovary are two of the most common\nmalignant neoplasia associated with endometriosis.\nOCCC is the second most common type of ovarian cancer in the world [ 67 ]. OCCC often presents as a unilateral pelvic\nmass that can cause abdominal distension and pain. Originally, it was believed that\nOCCC arose from either endometriosis lesions or fibroadenomas, and in 2015, it was\nsuggested that endometriosis was the root behind both of these mechanisms [ 68 ]. One hypothesized pathway details that\natypical epithelial cells arise from previous endometriotic lesions in the ovary\nprior to progressing into cancer. The second potential mechanism outlines that\nnon-cystic ectopic endometrial implants generate fibroadenomas, which develop\natypical cells that develop into OCCC [ 68 ].\nThe nuclear atypia is most commonly characterized by mutations in PTEN, ARID1a,\nPIK3CA, and p53 [ 69 ]. The worse prognosis is\nassociated with ovarian rupture prior to surgery [ 70 ]. Commonly, OCCC is treated with platinum-based chemotherapy.\nHowever, there is increasing evidence that localized OCCC arising in a focus of\nendometriosis may be treated with localized radiation therapy using systems like\nIMRT and SBRT [ 71 ].\nEAOC comprises 20% of all ovarian cancers [ 72 ] and is the most common form of malignancy related to endometriosis\n[ 73 ]. It most often presents with pelvic\npain, abdominal distention, pelvic bleeding, and a pelvic mass [ 74 ]. There is a close association between atypical\nendometriosis lesions and EAOC [ 64 ]. Multiple\nstudies have found endometriosis within the malignant tissue upon histological\nreview in 40% [ 75 ] and 43% [ 76 ] of EAOC cases. All of the endometriosis samples were\natypical [ 46 ], suggesting a link. Continued\nmolecular analysis of EAOC has shown that ARID1a, PTEN, TP53 and KRAS are the most\ncommon mutations found in ovarian EAOC [ 77 ].\nThe use of CA-125 as a potential biomarker for EAOC is limited as this subtype of\novarian cancer may not result in CA-125 elevations [ 78 ]. When diagnosed, these masses typically tend to be low grade (grade\n1 or 2) [ 79 ], but are often mistaken for high\ngrade serous carcinomas. Recent evidence has supported the use of WT1\nimmunohistochemistry staining to help differentiate the two, as serous carcinomas\nstain WT1 positive and EOCs stain negative [ 80 ]. Standard treatment for EOAC involves platinum-taxane combination\ntherapy due to the cancer’s high sensitivity to the chemotherapy. However,\nthe relapse rate is high [ 80 ,  81 ].\nA much less common malignancy potentially related to endometriosis is\nMullerian adenocarcinoma. Increasing amounts of case studies have unearthed a\npotential relationship to the development of this extrauterine adenocarcinoma from\nendometriosis. The locations of these tumors tend to be in common areas of\nendometriosis, such as the ovaries, fallopian tubes, and rectouterine pouch [ 82 ]. Mullerian adenocarcinoma arising from a\ndeep infiltrating endometriotic lesion, and in women with recurrent endometriosis\nhas been reported [ 83 ]. The exact mechanism\nof this malignancy is still unclear and a deeper molecular and pathological analysis\nis needed.\n\nElucidating endometriosis’ molecular fingerprint is to understand the\nmolecular mechanisms that drive the endometriosis-associated malignant phenotype.\nEndometriosis is complex, but identifying the novel biomarkers, inflammatory\nmolecules, and genetic links holds the key to the enhanced detection, prediction and\ntreatment of both endometriosis and endometriosis related malignant neoplasia. In\nfuture studies, an important focus may be the potential link between C3aR1, PGR,\nER1, SOX-17 and other relevant gene expression profiles and gynecologic\nmalignancies. Further studies should also focus on the combined use of CA-125 with\nHE-4 as well as the role for OVA1/MIA as clinically relevant diagnostic biomarkers\nin the prediction of endometriosis-driven tumorigenesis. A better understanding of\nthe predictive roles of these genes and the predictive value of the biomarker\nproteins will allow for the derivation of unique molecular treatment algorithms to\nbetter serve our patients.","source_license":"CC0","license_restricted":false}