Abstract 5695: Examining the tumor suppressor function of FBXW7 in endometrial cancer

Abstract Endometrial cancer (EC) is the sixth most commonly occurring cancer in women, with incidence rates steadily increasing in recent years. The American Cancer Society estimates 67, 880 new cases and 13, 250 deaths in 2024. A racial disparity is observed in EC as Black patients often have higher grade disease, worse outcome and the more serve subtype of EC, uterine serous carcinoma (USC). The National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) program estimates that per 100, 000 cases of EC, Non-Hispanic Black (NHB) patients have a death rate of 9.5 while Non-Hispanic White (NHW) patients have a death rate of 4.7. Disparity is most evident in metastatic USC, since NHW patients have a 5-year survival of 20% while NHB patients only have 5-year survival of 10%. In metastatic disease, FBXW7 mutation rates are higher in NHB patients compared to NHW patients. Using the TCGA database, we found FBXW7 is a tumor suppressor that is frequently mutated in endometrial cancer and has a higher mutation rate in USC compared to endometroid carcinoma. FBXW7 functions as a tumor suppressor through its ubiquitinase activity, in which it targets many oncoproteins for degradation including c-Myc, Notch1, Cyclin E, and mTOR. Previously our lab worked to purify FBXW7 via immunoprecipitation and found that FBXW7 may interact with MLH1, a DNA mismatch repair enzyme. To characterize potential-protein interactions between FBXW7 and MLH1, we transfected endometroid carcinoma cells with FBXW7 or MLH1 plasmids to elevate expression of these proteins and found that overexpression of FBXW7 results in a decrease in MLH1 expression. This may indicate MLH1 is a substrate for FBXW7 and is regulated via FBXW7 mediated ubiquitination. We then generated a FBXW7 knockout model in 12Z cells using a CRISPRCas9 system. With our successful FBXW7 knockout clone, we examined alterations of protein expression via Western Blot analysis. We see an increased expression of mTOR following knockdown of FBXW7, as this is a canonical substrate of FBXW7 ubiquitination. To investigate potential effects on invasion, we examined EMT markers Vimentin and E-Cadherin, where we see a decreased expression of Vimentin but unaltered expression of E-Cadherin following FBXW7 knockout. Due to the mutational frequency of FBXW7 in NHB metastatic UCS, we also examined changes in HER2 expression. Herceptin, which targets HER2, was previously clinically used as a therapy for UCS and had variable success in patients. Here we see a decrease of HER2 following FBXW7 knockout. Using the CRISPR-mediated knockout cells, ongoing studies will investigate cell growth rates and invasion FBXW7 mutant 12Z. Citation Format: Sophia E. Agrusa, Swornalata Pukhrambam, Areebah Qazi, Madelyn Maurer, Sneha Aradhya, Jessica Back, Mike R. Wilson. Examining the tumor suppressor function of FBXW7 in endometrial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5695.