DNMT1 promotes bladder cancer progression and immune escape by inhibiting MYH11 expression by methylating its promoter.

Abstract

Background: Bladder cancer (BC) is a fatal malignancy of the urinary tract with limited effective biomarkers and therapeutic targets. This paper delved into the mechanism of MYH11 and DNMT1 in BC progression.

Methods: Differential genes obtained from the GSE3167 dataset were analyzed by the R language limma package. RT-qPCR, Western blot, and immunohistochemistry were carried out to assess MYH11 and DNMT1 expression in BC cell lines and BC tissues. Cell migration, invasion, proliferation, and apoptosis were detected by Transwell assay, CCK-8, and TUNEL after different lentiviral vector treatments. MB49 cells with different infections were administered into mice to monitor tumor growth and immune escape. Flow cytometry detected the rate of CD45⁺CD4⁺-positive cells in the tumor tissues and PD-1 and TIM-3 expression in CD4⁺ T cells. MYH11 methylation was analyzed using the qMSP assay. ChIP and dual-luciferase assay were used for regulatory assays.

Results: MYH11 was lowly expressed in BC. Overexpression of MYH11 inhibited the malignant progression of BC cells, promoted anti-tumor immune responses of CD4⁺ T cells, and inhibited immune escape and tumor development in mice. DNMT1 inhibited MYH11 expression by elevating MYH11 promoter methylation. DNMT1 inhibition impeded the immune escape of BC cells, which was reversed by silencing MYH11. DNMT1 silencing prevented immune escape via transcriptional activation of MYH11 and hindered tumor growth in mice.

Conclusion: DNMT1 promotes immune escape and malignant progression of BC by methylating the promoter of MYH11.