miR ‐640 Enhances Abemaciclib Sensitivity by Suppressing CDK Inhibitor Resistance‐Associated Genes in Breast Cancer Cells

ABSTRACT

We investigated the potential of miR‐640 to downregulate CDK4/6 inhibitor resistance‐associated genes and evaluated its apoptotic, anti‐metastatic and anti‐proliferative effects, both alone and in combination with abemaciclib in breast cancer cells. miR‐640 was identified via GSE126125 dataset analysis. Targets were predicted using miRDB, TargetScan and TargetMiner, filtering for resistance‐associated genes. MTT assays determined IC50 values for abemaciclib and combinations. Functional effects were evaluated in MCF7 and MDA‐MB‐231 cells through Annexin V, cell cycle and wound healing assays. Target gene expression was quantified by RT‐qPCR. Successful transfection significantly upregulated miR‐640 (~50‐fold). The miR‐640/abemaciclib combination strongly inhibited migration, induced apoptosis and triggered cell line‐specific phase arrests (S and G2/M in MCF7; G0/G1 in MDA‐MB‐231). Gene expression analysis showed significant downregulation of a comprehensive resistance network (including CDK4/6 , CDKN2B , WNT7B , MAP3K1 and AURKA ) in MCF7 cells. In MDA‐MB‐231 cells, PDK1 , CDK6 , CDKN2B , SMAD2 , ZFP91 , MAP3K1 and AURKA were significantly suppressed. This study identifies miR‐640 as a potent tumour suppressor that resensitises breast cancer cells to CDK4/6 inhibition. By post‐transcriptionally downregulating key resistance genes, miR‐640—alone or additively with abemaciclib—suppresses proliferation and migration while inducing apoptosis, emerging as a promising combinatorial therapeutic strategy.