TRIM58 downregulation maintains stemness via MYH9-GRK3-Hippo/YAP axis activation in triple-negative breast cancer stem cells

Abstract

Abstract Background TRIM58 is, a member of the TRIM protein family, which possess with E3 ubiquitin ligase activities. Studies have revealed that weak expression of TRIM58 plays key roles, has been implicated in the tumor progression of tumor formation due to its reduced expression. However, its role in regulating the stemness of breast cancer stem cells (CSCs) remains unexplored. Methods The expression of TRIM58 was examined in breast cancer cells and triple-negative breast cancer (TNBC) patient specimens. Human TNBC CSCs were enriched from TNBC patient cancer tissues using serum-free medium. Stemness functions of TRIM58 in CSCs were assessed using western blot, cell viability analysis, tumorsphere formation assay, and subcutaneous tumorigenesis assays. Mechanistic investigations of TRIM58 on stemness and differentiation were conducted using co-immunoprecipitation, mass spectrometry, q-PCR, ubiquitination detection, label-free quantitative proteomics, and dual luciferase reporter assays. Results TRIM58 was underexpressed in TNBC tissues and cells compared to adjacent mucosa tissue, and its downregulation was significantly associated with shorter survival. Overexpression of TRIM58 reduced the proportion of CD44+/CD24- cells, upregulated differentiation genes, and inhibited stemness-related gene expression in TNBC CSCs. In vitro and in vivo experiments revealed that TRIM58 overexpression in CSCs suppressed tumor sphere formation and tumorigenic capacity. Co-IP results indicated direct interaction between TRIM58 and MYH9, with TRIM58 inducing MYH9 degradation via ubiquitination in differentiated cells. Label-free quantitative proteomics identified GRK3 and Hippo-YAP as downstream targets and signaling pathways of MYH9. TIMER database analysis, immunohistochemistry, western blotting, DNA-protein pulldown experiments, and dual luciferase reporter assays demonstrated that MYH9 regulated GRK3 transcriptional activation in CSCs. Conclusions This study highlights the negative impact of TRIM58 on the stemness of triple-negative breast CSCs. Elevated TRIM58 expression in CSCs downregulates MYH9 protein levels by promoting ubiquitin-mediated degradation, thereby inhibiting downstream GRK3 transcription, inactivating the Hippo-YAP stemness pathway, and ultimately promoting CSC differentiation.