CircGSK3β mediates PD-L1 transcription through miR-338-3p/PRMT5/H3K4me3 to promote breast cancer cell immune evasion and tumor progression.

Circular RNA (circRNA) plays a pivotal role in breast cancer onset and progression. Understanding the biological functions and underlying molecular mechanisms of dysregulated circRNAs in breast cancer is crucial for elucidating its pathogenesis and identifying potential therapeutic targets. In this study, we investigated the role and molecular mechanism of circGSK3β in breast cancer. We found that circGSK3β is highly expressed in breast cancer cell lines, where it promotes cell proliferation, migration, and invasion, thereby driving breast cancer progression. Furthermore, we observed a close association between circGSK3β expression levels and immune evasion in breast cancer cells. Mechanistically, circGSK3β acts as a competing endogenous RNA (ceRNA) by interacting with miR-338-3p, thereby promoting breast cancer cell proliferation, migration, and invasion. Additionally, circGSK3β positively regulates the expression of the target gene PRMT5 through its interaction with miR-338-3p. This, in turn, enhances H3K4me3 recruitment to the promoter region of PD-L1, resulting in upregulation of PD-L1 expression and consequent immune evasion in breast cancer. In summary, our findings underscore the significance of the circGSK3β-miR-338-3p-PRMT5-H3K4me3 axis in promoting breast cancer progression and immune evasion. CircGSK3β emerges as a critical player in breast cancer pathogenesis, potentially serving as a diagnostic and prognostic marker, and offering novel insights into the role of circRNAs in breast cancer progression.