Synergistic apoptotic effect of miR-183-5p and Polo-Like kinase 1 inhibitor NMS-P937 in breast cancer cells.

MicroRNAs (miRNAs) are small noncoding RNAs that act as endogenous regulatory molecules targeting specific mRNAs for translational repression. Studies of breast cancer genomics indicate that breast cancer subtypes are distinguished and regulated by specific sets of miRNAs which affect activities such as tumor initiation, progression, and even drug response. Polo-like Kinase 1 (PLK1) is widely considered to be a proto-oncogene due to its increased expression in multiple tumor types, as well as its crucial role in regulating mitosis. Pharmacological inhibition of PLK1 can reduce tumor volume and induce tumor cell death in solid and hematologic malignancies. This prompted us to investigate how PLK1 inhibition with the target-specific inhibitor NMS-P937 would impact breast cancer cells, and how miRNAs may influence the overall response of these cells to this inhibition. We found that miR-183-5p targets PLK1 gene, effectively reducing its protein expression. Such miRNA-driven regulation of PLK1 expression sensitizes breast cancer cells to NMS-P937, resulting in synergistically increased apoptosis. We also show that the miRNA-regulated reduction of PLK1 influences the expression of apoptosis-related key proteins and possibly inducing further indirect PLK1 downmodulation through a DNMT1-p53 axis. These results suggest a potential biologically significant link between the expression of miR-183-5p and the efficacy of PLK1-specific inhibitors in breast cancer cells. Our work further elucidates how miR-183-5p regulates PLK1 gene while also enhancing NMS-P937 effect in breast cancer. Future studies assessing the role of miR-183-5p as a novel biomarker for anti-PLK1 chemotherapy agents are warranted.