SAT632 The Functional Role And Regulatory Mechanism Of FTO M(6)A RNA Demethylase In Human Uterine Leiomyosarcoma

Disclosure: Q. Yang: None. A. Al-Hendy: None. Introduction: Uterine leiomyosarcoma (uLMS) is the most frequent subtype of uterine sarcoma that presents a poor prognosis, high rates of recurrence, and metastasis. However, the origin and molecular mechanism underlying driving its clinical and biological behavior remain to be determined. Recently, we and others have revealed the role of microRNAs, DNA methylation, and histone modifications contributing to the pathogenesis of uLMS. However, the connectivity between reversible RNA m(6)A methylation and uLMS remains unclear. In this study, we assessed the role and mechanism of the m(6)A demethylase fat mass- and obesity-associated protein (FTO) in the pathogenesis of uLMS. Materials and Methods: We performed immunohistochemistry (IHC) and immunoblot analysis to measure the m6A erasers FTO and ALKBH5 protein levels in LMS and adjacent myometrium tissues (n=8) and cell lines. We performed LMS cell proliferation and cell cycle phase distribution analysis. RNA-seq was performed to determine the molecular mechanism underlying m(6)A eraser inhibition in LMS cells (n=4 for each group). The R package limma+voom was used for this analysis. Hallmark pathway analysis was used to identify enriched pathways in response to FTO inhibition. Real-time PCR was performed to validate the differentially expressed genes. Ingenuity pathway analysis (IPA) was performed to determine the upstream regulators targeting cell cycle-related genes. We used a cutoff −1.5 > fold-change > 1.5 and an adjusted p-value of 0.05. In addition, data were analyzed by a two-tailed unpaired Student’s t-test between any two groups. Results: IHC analysis revealed that m6A demethylases FTO and ALKBH5 are aberrantly upregulated in uLMS tissues compared to adjacent myometrium (p<0.01, H-score). Furthermore, inhibition of FTO with its small, potent inhibitor (Dac51) decreased the uLMS proliferation dose-dependently via cell cycle arrest at G1. Notably, RNA-seq analysis revealed that inhibition of FTO with Dac51 exhibited a significant decrease in the expression of multiple CDK members and a significant increase in the expression of CDKN1A. Furthermore, IPA analysis revealed that transcription factors, including SP1 and E2F members are the upstream regulators targeting CDK members in response to Dac51 treatment. Moreover, Dac51 treatment altered the expression of several epigenetic regulators, including Sirt1 and 2, HDAC10 and SUV39H1, and rewiring of several critical pathways, including inflammation response, G2M checkpoint, and C-Myc signaling, among others, leading to suppression of uLMS phenotype. Conclusion: Our findings uncover the anti-uLMS function of a potent FTO inhibitor via reprogramming the oncogenic epitranscriptome. Therefore, targeted inhibition of FTO may provide an additional regulatory layer for a promising and novel strategy for treating patients with this aggressive uterine cancer. Presentation: Saturday, June 17, 2023