CDK1-mediated phosphorylation of APE1 drives synthetic lethality, p53-dependent metastasis, and immune sensitization in NSCLC

Abstract

Cyclin-dependent kinase 1 (CDK1), a serine/threonine kinase essential for cell cycle progression, also plays critical roles in DNA damage response, gene expression regulation, and therapeutic resistance. In this study, we identify a previously unrecognized regulatory link between CDK1 and apurinic/apyrimidinic endonuclease 1 (APE1) in non-small cell lung cancer (NSCLC). Both CDK1 and APE1 are highly expressed in lung tumors and exhibit an inverse correlation in protein expression levels across multiple lung cancer cell lines. Mechanistically, CDK1 phosphorylates APE1 at Ser54 to promote its degradation, whereas inhibition of CDK1 stabilizes APE1 protein levels and reduces the efficacy of APE1-targeted therapy. Importantly, activation of CDK1 through WEE1 inhibition using MK1775 enhances APE1 degradation and markedly sensitizes NSCLC cells to APE1 inhibition, inducing synthetic lethality. CDK1-mediated APE1 degradation mimics APE1 loss, leading to genome instability, cell-cycle dysregulation, and altered metastatic behavior. Notably, the effect of CDK1-mediated APE1 phosphorylation on cell motility is p53-dependent: in p53-proficient cells, phosphorylated APE1 activates p53-dependent programs that suppress migration and invasion, whereas in p53-deficient cells the same modification enhances metastatic potential. Furthermore, further investigation revealed that APE1 deficiency activates the cGAS–STING pathway and induces PD-L1 expression through the MAPK–ERK axis, thereby reshaping the tumor immune microenvironment and enhancing sensitivity to immune checkpoint blockade. Given the dual roles of CDK1 in APE1 regulation and immune modulation, we propose that a sequential or combinatorial strategy in which WEE1 inhibition activates CDK1 to promote APE1 degradation, priming cancer cells for APE1 inhibition and inducing synthetic lethality, while minimizing toxicity to normal cells. This approach simultaneously disrupts APE1’s endonuclease and homologous recombination repair functions and exploits CDK1-driven immune reprogramming to potentiate anti–PD-L1 immunotherapy. Collectively, our findings establish CDK1-mediated APE1 phosphorylation as a key node linking DNA repair, immune evasion, and therapeutic response, and providing a mechanistic rationale for combined CDK1–APE1–PD-L1-targeted therapy in NSCLC.