CDK4 and CDK6 upregulation promotes DNA replication stress, genomic instability and resistance to EGFR targeted therapy in lung cancer

Genetic interactions impact both normal human physiology and human diseases, such as cancer. Here, we study genetic interactions through the lens of human lung cancers driven by oncogenic forms of the epidermal growth factor receptor (EGFR), which we and others previously showed harbor a rich landscape of genetic co-alterations and potential genetic interactions. Among the most common genetic co-alterations with oncogenic EGFR are genomic amplifications of cell cycle regulators CDK4 or CDK6 , which have been implicated in EGFR inhibitor clinical resistance, although the mechanism underlying this effect is not well characterized. We show that CDK4/6 upregulation overcomes EGFR inhibitor-induced G1/S cell cycle arrest in association with increased replication stress, DNA damage and genomic instability. These biological effects arising in CDK4/6 upregulated tumors help to enable resistance to EGFR targeted therapies through established genetic resistance mechanisms. Combinatorial EGFR and CDK4/6 inhibitor treatment alleviated genomic instability and EGFR inhibitor resistance in patient-derived preclinical models. This study reveals mechanistic and clinical impacts of the genetic interaction between oncogenic EGFR and CDK4/6 co-alterations in human lung cancer.