Histone Methyltransferase SETD2 Inhibits Tumor Growth <i>via</i> Suppressing CXCL1-Mediated Activation of Cell Cycle in Lung Adenocarcinoma

Abstract

Background: The histone H3 lysine 36 methyltransferase SET-domain-containing 2 (SETD2) has been reported to be frequently mutated or deleted in many types of human cancer. However, the role of SETD2 in lung adenocarcinoma (LUAD) has not been well documented. Method: Real-time qPCR, western blotting analysis and immunohistochemistry (IHC) assays were utilized to analyze the expression pattern of SETD2 in LUAD tissues and cell lines. Cell viability analysis, colony formation and flow cytometry was used for cell growth analysis. RNA sequencing (RNA-seq) was used to analyze the downstream target gene of SETD2. Bioinformatics method was applied to analyze the regulatory network in which SETD2 and CXCL1 involved. Luciferase reporter and chromatin immunoprecipitation (ChIP) assays were utilized to test the interaction between SETD2 and CXCL1. Xenograft experiments were used to analyze tumor growth in vivo. Finding: In the present study, we found that SETD2 was significantly down-regulated both in LUAD tissues and cell lines. Functionally, the increased expression of SETD2 significantly attenuated the proliferation of cancer cells by affecting the cell cycle, whereas SETD2 deficiency dramatically improved these proliferative abilities of cancer cells. Through conjoint analysis of RNA-seq and ChIP data, we identified a functional target gene of SETD2, CXCL1, and its expression was negatively correlated with that of SETD2. Moreover, SETD2 deletion stimulated cell cycle-related proteins to promote LUAD. Further mechanistic studies demonstrated that histone H3 lysine 36 trimethylation (H3K36me3) catalyzed by SETD2 interacted with the promoter of CXCL1 to regulate its transcription and downstream signaling pathways, contributing to tumorigenesis in vitro and in vivo. Interpretation: Our findings suggested that SETD2 inhibited tumor growth via suppressing CXCL1-mediated activation of cell cycle, indicating that the regulation of H3K36me3 level by targeting SETD2 and/or the administration of downstream CXCL1 might represent a potential therapeutic way for new treatment in LUAD. Funding Statement: This study was supported by grants from the National Natural Science Foundation of China (31701111, 81902386), the National Key R&D Plan (2018YFC1313400), the National Key Technology R&D Program (2015BAI12B12), Postdoctoral Research Foundation of China (2018M642305), Natural Science Foundation of Jiangsu Province (BK20170295), Postdoctoral Science Foundation of Jiangsu Province (2018K029A) and Applied Basic Research Project of Changzhou (CJ20179024, CJ20190094). Declaration of Interests: The authors state that they have nothing to disclose. Ethics Approval Statement: All human tissue-related experiments were approved by the Ethical Committee of the Third Affiliated Hospital of Soochow University. Written informed consents were obtained from all patients before surgery. The animal-related experiments were approved by the Institutional Animal Care and Use Committee of the Third Affiliated Hospital of Soochow University.