Abstract 5273: The E3 ubiquitin ligase SIAH2 promotes clear cell renal cell carcinoma epithelial-mesenchymal transition via regulation of SETD2 stability
Authors: Yu Mengxue , Ju Lingao , Wang Gang 
Published: April 2023

Abstract
Introduction & Objective: SETD2, a major histone H3K36 trimethyltransferase, has been shown to play an important role in multiple biological processes. Mutations in SETD2 have been evidenced in several types of cancer, including clear cell renal cell carcinoma (ccRCC). Previous studies reported the potential involvement of SETD2 in driving ccRCC tumorigenesis. However, the mechanism by which SETD2 causes cell metastasis remains poorly understood.
Methods: Genome-wide CRISPR-Cas9-based screens and immunoprecipitation-mass spectrometry were used to identify candidates for regulating SETD2 stability. Immunohistochemistry staining of the ccRCC tissue array and bioinformatics analysis of TCGA database were used to investigate the clinical relevance of SETD2 in ccRCC. The gene expression was detected by qRT-PCR, and the protein level was detected by western blotting. Wound healing and transwell migration assay were used to explore the cell migration ability. SIAH2 was deleted from ccRCC cell lines using CRISPR/Cas9-mediated gene editing. Furthermore, we used BALB/c-nude mice to construct xenograft mouse models and pulmonary metastasis models. Moreover, RNA-seq, H3K36me3 CUT&Tag and RNA N6-methyladenosine-IP were performed to uncover the mechanism.
Results: SETD2 mutant or low expression was correlated with poor prognosis in patients with ccRCC based on TCGA data and tissue array. Through the CRISPR/Cas9 screening system and immunoprecipitation-mass spectrometry, we identified the E3 ubiquitin ligase SIAH2 that regulates the stability of SETD2. Then, we verified that the protein stability of SETD2 was downregulated by SIAH2 in a dose-dependent manner and further confirmed that the SIAH2 promotes SETD2 degradation in a proteasome-dependent pathway. In addition, we constructed a dominant negative mutant of SIAH2 and proved the degradation dependent on its enzymatic activity. Moreover, we showed that SIAH2 knockout increased the protein level of SETD2. In SETD2 stable knockdown ccRCC cell lines, loss of SETD2 enhanced the capability of cell migration, while knockdown of SIAH2 resulted in the rescue of SETD2 deficient effect. Moreover, SETD2 ablation significantly decreases H3K36me3 peaks of E-cadherin, further reducing the m6A signal and stability of E-cadherin mRNA.
Conclusion: In this study, we firstly revealed the mechanism that E3 ubiquitin ligase SIAH2 interacted with SETD2 and promoted the ubiquitination degradation of SETD2. Moreover, SETD2 ablation in ccRCC cells enhanced EMT through impaired epigenetic regulation of E-cadherin, suggesting SIAH2/SETD2/E-cadherin axis as a potential therapeutic target for ccRCC.
Citation Format: Mengxue Yu, Lingao Ju, Gang Wang. The E3 ubiquitin ligase SIAH2 promotes clear cell renal cell carcinoma epithelial-mesenchymal transition via regulation of SETD2 stability. [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 5273.