e17613 Background: Several societies have advocated for universal Lynch syndrome screening in endometrial cancer (EC). Mismatch repair proteins (MMR) are examined using immunohistochemistry (IHC) including MLH1, PMS2, MSH2, MSH6 with reflex MLH1 methylation testing in cases with loss of MLH1/PMS2. Typically, these genes form a heterodimer complex; if MLH1 is absent, then PMS2 is absent and if MSH2 is absent, MSH6 is absent. However, PMS2 and MSH6 can be absent independent of their co-proteins. Therefore, by detecting the presence or absence of PMS2 and MSH6 one can in theory detect all cases of mismatch repair deficiency (MMRd), both as an independent loss and co-protein loss. With the expansion of additional molecular biomarkers in EC, there is a need to address cost-effectiveness of screening tools, while maintaining accuracy with the diagnosis. Methods: We conducted a retrospective chart review of all patients with newly diagnosed EC from 2014-2020 at a single institution. All tumors underwent MMR screening by IHC for MLH1, PMS2, MSH2, MSH6 with reflex MLH1 hypermethylation. At our institution, the cost of 1 immunostain was $130.00, 2 immunostains $235.00, 4 immunostains $445.00. The cost of MLH1 hypermethylation testing was $175.00. Results: We identified 1702 cases of newly diagnosed endometrial cancer who underwent surgical excision and MMR IHC staining. Of these cases, 408 (24.0%) were MMRd and 1,294 (76%) were MMRp. In the MMRd population for MLH1/PMS2: 311 (76.2%) had MLH1 promoter hypermethylation, 14 (3.4%) MLH1-/PMS2-/MLH1 non-methylated, 8 (2.0%) MLH1-/PMS2-/no methylation testing performed, 14 (3.4%) MLH1+/PMS2-, 1 (0.2%) MLH1-/PMS2+/MLH1 non-methylated. For MSH2/MSH6: 24 (5.9%) MSH2-/MSH6-, 31 (7.6%) MSH2+/MSH6-, 0 (0%) MSH2-/MSH6+. There were 3 (0.7%) MLH1-/PMS2-/MSH6-/MLH1 promoter hypermethylation, and 2 (0.5%) MLH1-/PMS2-/MSH6-/MLH1 non-methylated. The sensitivity of the two-protein testing strategy of PMS2 and MSH6 alone was 99.8%. The total cost of IHC for 1702 cases using 4 immunostains ($445.00) was $757,390.00. The additional cost of reflex methylation testing ($175.00 each) performed on 339 tumors was $59,325.00. Thus, the total cost for a complete MMR evaluation was $816,715.00 for the cohort. Performing a two-protein PMS2/MSH6 test ($235.00) with reflex MLH1 methylation testing when cases had loss of PMS2 alone ($175.00) would cost $461,570.00 for this cohort. This would result in a cost savings of $355,145.00. Conclusions: A two-protein MMR IHC screen for Lynch syndrome and biomarker assessment is highly sensitive. With expanding use of IHC testing in the management of EC, strategies to reduce health care and resource utilization will be critical.

BACKGROUND:Contemporary management of endometrial cancer includes molecular classification. The primary objective of this study was to assess the prognostic significance of copy number changes evidenced by loss of heterozygosity (LOH) or allelic imbalance (AI). METHODS:Sequencing including TP53, POLE and MSI testing was performed. AI/LOH at 5 polymorphic markers (D2S123, D5S2346, D17S250, D17S516 and D17S1818) was assessed. Micro-satellite stable (MSS) endometrial tumors were classified as having evidence of AI/LOH or no evidence of AI/LOH. RESULTS:482 MSS cases were evaluated for AI/LOH status. There were 226 (46.5 %) tumors with evidence of AI/LOH at ≥1 of the 5 markers and these were significantly associated with patients of older age and lower body mass index as well as tumors that were non-endometrioid histology, higher grade, demonstrated LVSI, and presented at more advanced stage. Most patients who developed recurrent disease had a tumor with AI/LOH (82.1 %). 3-year progression-free survivals (PFS) were 79.5 % in the AI/LOH group vs 95.6 % in the no AI/LOH group (p < 0.0001). TP53 mutation status was associated with PFS. 3-year PFS was significantly worse for the TP53 mutated group at 55 % vs 96 % in TP53 wild-type (p < 0.0001). Of the 373 cases classified as having no specific molecular profile there was a 6.2 % recurrence rate with AI/LOH and 3.3 % recurrence with no AI/LOH. CONCLUSIONS:AI/LOH assessment at a limited number of markers identifies endometrial cancers with higher risk features that are more likely to recur. Copy-number assessment utilizing clinically accessible testing strategies can provide an opportunity for improved risk stratification.

Endometrial cancer (EC) is the most common gynecologic cancer. Early detection is one of the most important predictors of survival. The cancer is curable if detected early but the five-year survival rate in advanced cases can be as low as 22%. Microsatellite instability (MSI) testing is used to screen populations for Lynch Syndrome (LS), the most common cause of inherited EC, and to classify EC into distinct groups with unique histological, prognostic, and molecular features. Accurate sample identification is crucial for successful MSI testing because instability is assessed by comparing amplification patterns in markers in the normal and tumor samples that must be taken from the same individual. Penta-C and Penta-D pentanucleotide markers are used widely for sample identification in not only MSI testing but also parentage verification, forensic science, and population genetics studies. The objective of this study was to test 324 pairs of tumor and matched normal DNAs from EC patients for instability in these markers using the Promega MSI Analysis SystemTM considered the “gold standard” in MSI testing. Both markers were unstable, and therefore not reliable for MSI testing, in 8.2% of the EC patients with MSI. Instability in both mono- and pentanucleotide markers suggest that the tumors with MSI likely suffer from a “generalized” form of instability also affecting other short tandem repeats. Results from many studies using these markers for various purposes may not be accurate if samples with MSI are involved.

BACKGROUND:Sentinel lymph node (SLN) mapping has become standard-of-care in endometrial cancer surgical staging. While removal of "enlarged" lymph nodes is recommended regardless of SLN mapping, there is no data to support definitive size criteria for intra-operative assessment. We sought to assess the size of negative and positive SLN in surgically-staged endometrial cancer patients. METHODS:Surgically-staged endometrial cancer patients undergoing SLN assessment of at least one hemipelvis at a single comprehensive cancer center were retrospectively reviewed from 2017 to 2020. SLN were categorized as negative (benign) or positive (metastatic). SLN size was defined as the largest diameter (cm) of the SLN as measured in the gross description of the surgical pathology report. Size of negative and positive SLN was compared using descriptive statistics. RESULTS:Of 597 patients, 575 had an evaluable negative SLN, and median size was 2.0 cm [0.4-4.5 cm]. 39 patients had an evaluable positive SLN, and median size was 2.1 cm [0.5-4.9 cm]. Lymph node size ≥2 cm was 67 % sensitive and 49 % specific for detecting metastatic disease. Age < 50 and BMI ≥30 were associated with larger lymph node size (p = 0.04 and p = 0.028, respectively). For evaluable positive SLN, mismatch repair (MMR) IHC (n = 39), and p53 IHC (n = 18) did not impact size (p = 0.71 and p = 0.83, respectively). CONCLUSIONS:Negative and positive SLN are similar in size, thus SLN size is a poor predictor of metastasis in patients undergoing surgical staging of endometrial cancer. Intra-operative assessment of size should not serve as sole indication for targeted lymph node removal.

We performed molecular analysis of a single-institution cohort of clinically diagnosed mixed-histology endometrial carcinoma (MEC). A gynecologic pathologist confirmed that 72 cases met diagnostic criteria for MEC based on WHO 2020 guidelines, and these were molecularly classified using both a DNA-based and histologic approach. Tumors were classified as: POLE-mutated (13.9%), microsatellite instability (MSI)-high/mismatch repair deficient (MMRd) (26.4%), TP53/p53 abnormal (p53abnl) (48.6%), no specific molecular profile (NSMP) (11.1%). Recurrence risk significantly differed based upon molecular class, but not histology. 44% of MEC cases had a HER2 IHC score of 2-3+, and this was not limited to p53abnl tumors. Transcriptional analysis demonstrated 93 differentially expressed genes between p53abnl and NSMP tumors, including many associated with the innate immune response and DNA damage repair. While p53abnl and NSMP tumors have similarly poor outcomes, transcriptome analysis revealed biologic differences that could impact targeted therapeutics in this high-risk group.

Endometrial cancer (EC) is the leading gynecologic malignancy in the United States with obesity implicated in 57% of cases. This research delves into the molecular complexities of extracellular vesicle (EV) secretion as carriers of oncogenic protein expression and their involvement in obesity-mediated EC. An understanding of these mechanisms is pivotal for unraveling pathways relevant to obesity-associated EC, thereby guiding the development of innovative prevention and treatment strategies. Our investigation revealed a significant increase in EV secretion carrying oncogenic proteins (TMEM205, STAT5, and FAS) in adipose and uterine tissues/serum samples from obese EC patients compared to their non-obese counterparts. We identified alterations in EV-regulating proteins (Rab7, Rab11, and Rab27a) in obesity-mediated EC patient adipose and uterine samples. Through a 24-week analysis of the effects of a 45% kcal high-fat diet (HFD) on mice, we observed heightened body weight, increased adipose tissue, enlarged uterine horns, and heightened inflammation in the HFD group. This correlated with elevated levels of EV secretion and increased expression of oncogenic proteins TMEM205, FAS, and STAT5, while the tumor suppressor gene PIAS3 was downregulated in adipose and uterine tissues in HFD treated mice. Furthermore, our study confirmed that adipocyte derived EVs increased EC cell proliferation and migration. Additionally, we identified that the small molecule inhibitors (HO-3867) or Metformin inhibited EV secretion in vitro and in vivo, demonstrating significant inhibition of high glucose or adipocyte-mediated EC cell proliferation and a reduction in body weight and adipose tissue accumulation when administered to HFD mice. Moreover, HO-3867 or Metformin treatment inhibits HFD induced hyperplasia by altered the expression of EV-regulated proteins (Rab7, Rab11, and Rab27a) and decreased oncogenic protein expression (TMEM205, FAS and STAT5) levels. This study provides critical insights into the mechanisms supporting obesity-mediated EV secretion with oncogenic protein expression, shedding light on their role in EC pathogenesis. Additionally, it offers pre-clinical evidence supporting the initiation of novel studies for EV-targeted therapies aimed at preventing obesity-mediated EC.

OBJECTIVES:The American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) recommend cold ischemia time (cIT) be <60 min, and formalin fixation time (FFT) 6-72 h, to optimize immunohistochemistry (IHC) based on breast cancer data. We assessed whether cIT and FFT impact IHC in endometrial cancer (EC), and determined which factors affect cIT and FFT. METHODS:Surgical EC cases from 2019 to 2023 were reviewed. cIT was calculated by subtracting time of tissue devascularization intra-operatively from time the specimen was placed in formalin. Demographics, clinicopathologic and peri-operative factors, and IHC for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and mismatch repair (MMR) proteins were compared between patients with cIT <60 min versus ≥60 min (prolonged), and compliant FFT (6-72 h) versus non-compliant FFT (<6 or > 72 h). Categorical variables were compared using χ2 tests. RESULTS:941 patients were included in the analysis. Median cIT was 33 min. Prolonged cIT occurred in 95 (10 %) cases. African American/Black race (p < 0.001), advanced stage (p < 0.001), mini-laparotomy (p < 0.001), performance of surgical procedures beyond standard EC staging (p < 0.001), longer surgical length (p < 0.001), and increased uterine weight (p < 0.001) were independently associated with prolonged cIT. There were no significant differences in ER, PR, HER2, or MMR protein expression based on cIT or FFT. CONCLUSION:Prolonged cIT was not associated with differences in biomarker expression via IHC at time of surgical staging for EC. Despite variability in cIT, which is largely due to non-modifiable factors, tumor molecular features remain consistent and can reliably be utilized for prognostic and therapeutic decision-making.

AimsMesonephric‐like adenocarcinoma (MLA) of the endometrium or ovary is a rare but distinct endometrial carcinoma which has a combination of characteristic morphological, immunohistochemical (IHC) and molecular features. SOX17 has been recently identified as a highly sensitive and specific marker for endometrial and ovarian carcinomas. In this study, we aimed to investigate SOX17 expression in MLA together with other IHCs to differentiate MLAs from other endometrial carcinomas.MethodsSeventeen previously diagnosed endometrial/ovarian MLAs were collected, and multiple IHCs were performed. Additionally, we performed SOX17, PAX8 and ER on tissue microarrays (TMAs) composed of 652 endometrial carcinomas from 2012 to 2015 when MLA diagnostic criteria were not established.ResultsAll 17 MLAs showed diffuse strong positive PAX8, negative ER and variable TTF1/GATA3 staining. Notably, all MLAs showed negative (n = 10) or focal weak/moderate (n = 7) staining for SOX17, which is more diffuse and stronger than PAX8 in other endometrial carcinoma subtypes. This finding prompted us to screen TMAs with 652 endometrial carcinomas diagnosed before MLA by an approach of combined SOX17 and PAX8 IHCs, and 14 cases with positive PAX8 but negative/focal weak SOX17 were identified. We further studied the 14 cases by examining morphology and performing additional IHCs (TTF1, GATA3, ER and CD10) and would classify seven (50%) of them as MLAs based on morphological features and positive CD10, TTF1 and/or GATA3 staining.ConclusionOur results suggest that a combination of SOX17 and PAX8 IHCs would aid in diagnosing MLA if the results show strong positive PAX8, but negative SOX17.

Abstract Introduction: Endometrial cancer (EC) is the leading gynecologic malignancy in the U.S., with obesity implicated in 57% of cases. This study explores the molecular workings of oncogenic protein expression (TMEM205, STAT5, and FAS) and their role in regulating exosome secretion. Understanding these mechanisms is crucial for unraveling pathways involved in obesity-related EC, informing the development of innovative strategies for prevention and treatment. Methods: The isolated exosomes were quantified using nanoparticle tracking analyzer (NTA) and their size measured by Transmission electron microscopy (TEM). TMEM205, STAT5, FAS and PIAS3 expression was confirmed by IHC, ELISA and RT-PCR in patient and high fat diet treated mouse tissue. Endometrial hyperplasia was developed in immunocompetent mice using high fat diet (HFD; 45 kcal% fat diet) for 16 weeks. Results: Our study investigates exosome secretion and the regulation of oncogenic proteins in adipose and uterine tissues from obese EC patients compared to non-obese EC samples. Analyzing the effects of a 45% kcal high-fat diet (HFD) on mice over 24 weeks, we observed higher body weight and increased adipose tissue in the HFD group, along with enlarged uterine horns and heightened inflammation. This correlated with elevated exosome secretion and increased expression of TMEM205, FAS and STAT5, while the tumor suppressor gene PIAS3 was downregulated. The identified small molecule inhibitor, DAP-5, selectively targeting TMEM205 and exosome secretion, demonstrated a significant reduction in body weight and adipose tissue accumulation when administered to HFD mice. Additionally, DAP-5 treatment restored normal uterine morphology and reduced the expression of exosome-related proteins. Conclusion: This study offers central insights into the mechanisms underlying obesity-mediated TMEM205 expression and exosome secretion, shedding light on their role in the pathogenesis of EC. Additionally, it provides pre-clinical evidence supporting the initiation of the first in-human studies for exosome-targeted therapies aimed at preventing obesity-mediated EC. Citation Format: Takahiko Sakaue, Kalpana Deepa Priya Dorayappan, Roman Zingarelli, Wafa Khadraoui, Muralidharan Anbalagan, John Wallbillich, Mark Wascovich, Pragyan Paramita, Adrian Suarez, Casey Cosgrove, Larry G. Maxwell, Hironori Koga, David O’Malley, David Cohn, Selvendiran Karuppaiyah. Exploring the role of obesity-induced exosome secretion and associated proteins in endometrial cancer pathogenesis: A roadmap for prevention through exosome inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3377.

Endometrial cancer (EC) is the leading gynecologic malignancy in the United States with obesity implicated in 57% of cases. This research investigates the molecular complexities of extracellular vesicles (EV) secretion as carriers of oncogenic protein and their involvement in obesity-mediated EC. An understanding of these mechanisms is pivotal for unraveling pathways relevant to obesity-associated EC, thereby guiding the development of innovative prevention and treatment strategies. Our exploration revealed a significant increase in EV secretion carrying oncogenic proteins (TMEM205, STAT5, and FAS) in adipose and uterine tissues/serum samples from obese EC patients compared to control (without cancer). We identified alterations in EV-regulating proteins (Rab7, Rab11, and Rab27a) in obesity-mediated EC patients, adipose/uterine tissues, and serum samples. Through a 24-week analysis of the effects of a 45% kcal high-fat diet (HFD) on mice, we observed increased body weight, increased adipose tissue, enlarged uterine horns, and increased inflammation in the HFD group. This correlated with elevated levels of EV secretion and increased expression of oncogenic proteins TMEM205, FAS, and STAT5 and downregulation of the tumor suppressor gene PIAS3 in adipose and uterine tissues. Furthermore, our study confirmed that adipocyte derived EV increased EC cell proliferation, migration and xenograft tumor growth. Additionally, we identified that the small molecule inhibitors (HO-3867) or Metformin inhibited EV secretion in vitro and in vivo, demonstrating significant inhibition of high glucose or adipocyte-mediated EC cell proliferation and a reduction in body weight and adipose tissue accumulation when administered to HFD mice. Moreover, HO-3867 or Metformin treatment inhibited HFD induced hyperplasia (precursor of EC) by altering the expression of EV-regulated proteins and decreasing oncogenic protein expression levels. This study provides critical insights into the mechanisms underpinning obesity-mediated EV secretion with oncogenic protein expression, shedding light on their role in EC pathogenesis. Additionally, it offers pre-clinical evidence supporting the initiation of novel studies for EV-targeted therapies aimed at preventing obesity-mediated EC.

ObjectiveWe examined associations among changes in anthropometry, regional adiposity, and inflammatory markers in Black and White women participating in intentional weight loss.MethodsA total of 104 women with BMI >= 25 kg/m2 self-selected bariatric surgery (n = 66) or a diet and exercise program (n = 38). Anthropometric, dual-energy x-ray absorptiometry-quantified regional adiposity, and inflammatory markers (C-reactive protein [CRP], tumor necrosis factor alpha [TNF-alpha], soluble TNF receptor I [sTNFRI], sTNFRII, interleukin [IL]-6, and soluble IL-1 receptor antagonist) were measured at baseline and 6 months.ResultsWeight, BMI, visceral adipose tissue, and regional (android and gynoid) adiposity declined in the bariatric surgery group. Among bariatric surgery participants, Black women experienced declines of lesser magnitude in terms of weight and BMI than White women, but changes in regional adiposity and visceral adipose tissue did not differ. In the bariatric surgery group, decreases in weight and BMI were associated with decreases in CRP and IL-6 among White women, but not Black women. Decreases in weight, BMI, and android fat were associated with increases in TNF-alpha, sTNFRI, and sTNFRII among Black women, but not White women.ConclusionsDecreases in anthropometry and adiposity were observed among Black and White bariatric surgery participants; however, associations among changes in adiposity, anthropometry, and inflammation differed by race.

BACKGROUNDMismatch-repair (MMR)/microsatellite instability (MSI) status has therapeutic implications in endometrial cancer (EC). The authors evaluated the concordance of testing and factors contributing to MMR expression heterogeneity.METHODSSix hundred sixty-six ECs were characterized using immunohistochemistry (IHC), MSI testing, and mut-L homolog 1 (MLH1) methylation. Select samples underwent whole-transcriptome analysis and next-generation sequencing. MMR expression of metastatic/recurrent sites was evaluated.RESULTSMSI testing identified 27.3% of cases as MSI-high (n = 182), MMR IHC identified 25.1% cases as MMR-deficient (n = 167), and 3.8% of cases (n = 25) demonstrated discordant results. A review of IHC staining explained discordant results in 18 cases, revealing subclonal loss of MLH1/Pms 1 homolog 2 (PMS2) (n = 10) and heterogeneous MMR IHC (mut-S homolog 6 [MSH6], n = 7; MLH1/PMS2, n = 1). MSH6-associated Lynch syndrome was diagnosed in three of six cases with heterogeneous expression. Subclonal or heterogeneous cases had a 38.9% recurrence rate (compared with 16.7% in complete MMR-deficient cases and 9% in MMR-proficient cases) and had abnormal MMR IHC results in all metastatic recurrent sites (n = 7). Tumors with subclonal MLH1/PMS2 demonstrated 74 differentially expressed genes (determined using digital spatial transcriptomics) when stratified by MLH1 expression, including many associated with epithelial-mesenchymal transition.CONCLUSIONSSubclonal/heterogeneous MMR IHC cases showed epigenetic loss in 66.7%, germline mutations in 16.7%, and somatic mutations in 16.7%. MMR IHC reported as intact/deficient missed 21% of cases of Lynch syndrome. EC with subclonal/heterogeneous MMR expression demonstrated a high recurrence rate, and metastatic/recurrent sites were MMR-deficient. Transcriptional analysis indicated an increased risk for migration/metastasis, suggesting that clonal MMR deficiency may be a driver for tumor aggressiveness. Reporting MMR IHC only as intact/deficient, without reporting subclonal and heterogeneous staining, misses opportunities for biomarker-directed therapy.PLAIN LANGUAGE SUMMARYEndometrial cancer is the most common gynecologic cancer, and 20%-40% of tumors have a defect in DNA proofreading known as mismatch-repair (MMR) deficiency. These results can be used to guide therapy. Tests for this defect can yield differing results, revealing heterogeneous (mixed) proofreading capabilities. Tumors with discordant testing results and mixed MMR findings can have germline or somatic defects in MMR genes. Cells with deficient DNA proofreading in tumors with mixed MMR findings have DNA expression profiles linked to more aggressive characteristics and cancer spread. These MMR-deficient cells may drive tumor behavior and the risk of spreading cancer.

Objectives. To describe stage, treatment patterns, and survival for glassy cell carcinoma of the cervix (GCCC), a poorly understood rare tumor. Methods. Clinical data and survival were compared between GCCC and more common histologic types using the National Cancer Database (NCDB) from 2004 to 2017. A retrospective review of GCCC cases at our institution from 2012 to 2020 was simultaneously performed with staging updated according to 2018 FIGO staging. Descriptive statistics and survival analyses were performed, and outcomes compared to historical references. Results. 143/89,001 (0.16%) NCDB cervical cancer cases were GCCC. Compared to other histologies, GCCC cases were younger, with 74.8% diagnosed before age 50. Stage distribution was similar. Stage I cases were less commonly treated with surgery alone (19/69, 27%). 79.4% of locally advanced (stage II-IVA) cases were treated with definitive chemoradiation. GCCC demonstrated worse OS for early-stage and locally-advanced disease. No survival differences were observed for patients with stage IVB disease. Our institutional review identified 14 GCCC cases. Median age at diagnosis was 34 years. All nine early-stage cases underwent radical hysterectomy. Adjuvant radiation was given for cases meeting Sedlis criteria (4/9, 44%). All five advanced stage cases were stage IIIC and received definitive chemoradiation. Recurrence rate was 0% (0/9) for early-stage and 60% (3/5) for advanced-stage cases. 3-year PFS was 100% for early-stage and 40% for advanced-stage. 3-year OS was 100% for early-stage and 60% for advanced-stage GCCC. Conclusions. GCCC presents at earlier ages than other cervical cancer histologic types. Although NCDB showed worse OS, our more contemporary institutional review, which incorporates updated staging and newer treatment modalities found outcomes more similar to historical references of more common histologic subtypes. (c) 2023 Published by Elsevier Inc.

Endometrial cancer (EC) is the most common gynecologic cancer. Early detection is the most important predictor of survival. The cancer is curable if detected early but the ve-year survival rate in advanced cases is only 20%. Microsatellite instability (MSI) testing is frequently used to screen populations for early detection of Lynch syndrome (LS), the most common cause of inherited EC, and to classify EC into distinct groups with unique histological, prognostic, and molecular features. Accurate sample identi�cation is crucial for successful MSI testing because instability is assessed by comparing ampli�cation patterns in markers in the normal and tumor samples that must be taken from the same individual. Penta-C and Penta-D pentanucleotide markers are used widely for sample identi�cation in not only MSI testing but also parentage veri�cation, forensic science, and population genetics studies. We tested 324 pairs of tumor and matched normal DNAs from EC patients for instability in these markers using the Promega MSI Analysis System ™ considered the "gold standard" in MSI testing. Both markers were unstable, and therefore not reliable for MSI testing, in 8.2% of the EC patients with MSI. Instability in both mono-and pentanucleotide markers suggest that the tumors with MSI likely suffer from a "generalized" form of instability affecting other short tandem repeats as well. Results from many studies using these markers for various purposes may not be accurate if samples with MSI are involved.

<p>Role of STAT3 in high-grade serous carcinoma</p>

Background & Objective: Endometrial cancer (EC) is the most common gynecologic malignancy in the US. EC is more strongly associated with obesity than any other cancer type, with 57% of cases linked to obesity. As rates of obesity increase, the incidence of EC is also rising with worsening prognosis. The objective of this study is to identify the molecular mechanisms of TMEM205 expression that regulate exosome secretion, and the oncogenic proteins that underlie this transformation. Our findings are critical to understanding the pathways of obesity mediated EC and essential for developing novel strategies for preventing and treating EC. Methods: The exosomes were then quantified using nanoparticle tracking analyzer (NTA) and their size measured by Transmission electron microscopy (TEM). TMEM205, STAT5, FAS and PIAS3 expression was confirmed by IHC, WB and RT-PCR in patient and high fat diet treated mouse tissue. Endometrial hyperplasia was developed in immunocompetent mice using high fat diet (HFD; 45 kcal% fat diet) for 16 weeks. Results: To examine the effect of a continuous HFD (45 kcal% fat diet) on adipose, uterine and endometrial tissue, we first investigated body weight and uterine morphology in mice after 24 weeks of treatment. As expected, mice fed a HFD had a significantly higher body weight and increased adipose tissue when compared to control. In addition, mice in the HFD group showed marked enlargement in uterine horn size (hyperplasia) and inflammation with increased cell proliferation in the endometrial layer. The HFD treated mice were associated with increased exosome secretion and expression of the oncogenic proteins TMEM205 and STAT5. Expression of the tumor suppressor gene PIAS3 wasdownregulated in adipose and uterine tissues. L-2265 is a small molecule inhibitor that selectively inhibits TMEM205 and exosome secretion in EC cancer cells. To examine the effect of L-2263 in the context of obesity, we fed mice a HFD and treatment with L-2263 (2mg/kg/) weekly for 3 doses. L-2263 treatment resulted in significantly decreased body weight (BW) and decreased accumulation of adipose tissue relative to control HFD treated mice. Mice in the HFD group showed marked enlargement in uterine horn size (hyperplasia), whereas mice that received L-2263 treatment had normal uterine morphology of mouse age. L-2263 treated mice also demonstrated a significant decrease in the expression of proteins involved in exosome secretion (e.g., TMEM205 and STAT5) and those found in exosomes. Conclusion: This study provides fundamental insight into the mechanism of obesity-mediated TMEM205 expression and exosome secretion and their contribution to the pathogenesis of EC. This study is also provides pre-clinical evidence for the development of the first in-human studies of exosome-targeted therapies to prevent obesity-mediated EC. Citation Format: Takahiko Sakaue, Roman Zingarelli, Wafa Khadraoui, Uksha Saini, John Wallbillich, Muralidharan Anbazhakan, Ross Warner, Kalpana Deepa Priya Dorayappan, Deepika Kalaiyarasan, Molly Morton, Casey Cosgrove, Adrian Suarez, Larry J. Maxwell, David O'Malley, David E. Cohn, Karuppaiyah Selvendiran. Obesity-associated endometrial cancer: Identifying the contributions of TMEM205 expression to the pathogenesis of disease. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4236.

<p>Role of STAT3 in high-grade serous carcinoma</p>