DOI: 10.25442/hku.26886733.v1
title: Supporting data for "Functional Roles and Therapeutic Implication of UAP1, PGM3, and SOAT1 in Ovarian Cancer and CD8+ T cell-mediated Immune Response"

description: Ovarian cancer is one of the most lethal gynecological malignancies in the world and is characterized by late diagnosis, frequent metastasis, chemotherapy resistance, and a high recurrence rate. The omentum is the most common metastatic site of ovarian cancer. Deregulated metabolism is a hallmark of cancer. Targeting aberrant metabolic pathways in tumor cells not only directly affects tumors but also modulates immune cells such as CD8+ T cells in the tumor microenvironment, thereby altering tumor progression and metastasis. The suppression of CD8+ T cell-mediated immune responses can be relieved by the blockade of programmed cell death protein ligand 1 (PD-L1) immune checkpoint. The hexosamine biosynthetic pathway (HBP) is a glycolysis-related pathway that produces UDP-GlcNAc, which is crucial for protein glycosylation. Key enzymes in this pathway, such as Phosphoglucomutase 3 (PGM3) and UDP–N-acetylglucosamine pyrophosphorylase 1 (UAP1), are essential for this process. Although previous studies have shown that inhibiting PGM3 or UAP1 suppresses tumor progression in multiple cancers, their roles in ovarian cancer have not been fully explored.
1 In this study, we investigated functional roles and therapeutic implications of PGM3 and UAP1 in ovarian cancer. We found that UAP1 expression was increased in metastatic lesions. Silencing of UAP1 by siRNA/shRNA in ovarian cancer cells reduced cell migration, invasion, proliferation, and stemness through EGFR/AKT signaling and regulation of metastasis-related FGF1 and EGR1, stemness-related SOX2/OCT4 and cell cycle-related p27 expression as assessed by RNA-sequencing analysis and Western blotting, whereas CRISPRa activation of UAP1 showed opposite effects. UAP1 and related signaling and downstream targets were upregulated upon treatment with conditioned medium from omental tissues. Moreover, UAP1 depletion downregulated PD-L1 expression and augmented the cytotoxic function of CD8! T cells. By in vivo imaging, UAP1 knockdown resulted in reduced tumor growth and metastatic dissemination. We found higher expression of PGM3 in ovarian cancers. Inhibition of PGM3 by siRNA/shRNA or its inhibitor FR054 blocked proliferation, metastasis and stemness of ovarian cancer cells, whereas overexpression showed opposite effects. Mechanically, RNA-Seq and Western blotting showed reduced EGFR/AKT/ERK1/2 signaling. PGM3 knockdown resulted in reduced tumor growth and metastatic dissemination in mice. Besides HBP, we examined Sterol-O acyltransferase 1 (SOAT1), the key enzyme of cholesterol metabolism, in ovarian cancer. SOAT1 functions by converting cholesterol and acyl-CoA into cholesterol ester and CoA-SH. Our study determined the effect of SOAT1 manipulation and drug inhibition in ovarian cancer cells on CD8+ T cell-mediated immune response. Inhibiting SOAT1 by siRNA or its inhibitor avasimibe in ovarian cancer cells impaired CD8+ T cell cytotoxicity, likely due to the upregulation of tumor-derived IL-6 and IL-8. In conclusion, UAP1 and PGM3 significantly promote ovarian tumor progression through the EGFR/AKT signaling pathway, in which UAP1 plays a particularly important role in omental metastasis Targeting UAP1 and PGM3 (such as FR054) may be a potential therapeutic approach for ovarian cancer. Targeting SOAT1 in ovarian cancer may adversely affect the cytotoxic function of CD8+ T cells, which is an important factor to consider when developing therapeutic strategies.<br>