miR-622 Increases miR-30a Expression through Inhibition of Hypoxia-Inducible Factor 1α to Improve Metastasis and Chemoresistance in Human Invasive Breast Cancer Cells.

Hypoxia-inducible factor 1α (HIF-1α) plays a pivotal role in the survival, metastasis, and response to treatment of solid tumors. Autophagy serves as a mechanism for tumor cells to eliminate misfolded proteins and damaged organelles, thus promoting invasiveness, metastasis, and resistance to treatment under hypoxic conditions. MicroRNA (miRNA) research underscores the significance of these non-coding molecules in regulating cancer-related protein synthesis across diverse contexts. However, there is limited reporting on miRNA-mediated gene expression studies, especially with respect to epithelial-mesenchymal transition (EMT) and autophagy in the context of hypoxic breast cancer. Our study reveals decreased levels of miRNA-622 (miR-622) and miRNA-30a (miR-30a) in invasive breast cancer cells compared to their non-invasive counterparts. Inducing miR-622 suppresses HIF-1α protein expression, subsequently activating miR-30a transcription. This cascade results in reduced invasiveness and migration of breast cancer cells by inhibiting EMT markers, such as Snail, Slug, and vimentin. Furthermore, miR-30a negatively regulates beclin 1, ATG5, and LC3-II and inhibits Akt protein phosphorylation. Consequently, this improves the sensitivity of invasive MDA-MB-231 cells to docetaxel treatment. In conclusion, our study highlights the therapeutic potential of inducing miR-622 to promote miR-30a expression and thus disrupt HIF-1α-associated EMT and autophagy pathways. This innovative strategy presents a promising approach to the treatment of aggressive breast cancer.