Dual targeting CDK4/6 and CDK7 augments tumor response and anti-tumor immunity in breast cancer

CDK4/6 inhibitors (CDK4/6i) have significantly improved the prognosis for hormone-positive (HR+) breast cancer patients. However, the emergence of drug resistance severely limits their long-term efficacy, and CDK4/6i monotherapy remains largely ineffective against triple-negative breast cancer (TNBC). Here, we demonstrate that combining CDK4/6i with CDK7 inhibitors (CDK7i) offers a promising therapeutic strategy to overcome resistance in both HR+ breast cancer and TNBC. Kinetic analyses reveal that CDK7i primarily targets RNA polymerase II-mediated transcription, a key driver of CDK4/6i resistance by amplifying E2F activity following the degradation of the retinoblastoma protein. Consequently, the combination of CDK4/6i and CDK7i synergistically suppresses E2F activity and inhibits the growth of drug-resistant tumors. Furthermore, this combination stimulates immune response pathways and cytokine production in cancer cells, enhancing anti-tumor immunity. These findings provide critical insights into evolving CDK inhibition strategies and highlight the therapeutic application of CDK7i in breast cancer management.