CDK4/6 and BET inhibitors synergistically suppress pancreatic tumor growth and epithelial-to-mesenchymal transition by regulating the GSK3β-mediated Wnt/β-catenin pathway.

Cyclin-dependent kinases 4 and 6 (CDK4/6) are frequently upregulated in pancreatic ductal adenocarcinoma (PDAC) and are associated with poor overall survival. Although CDK4/6 inhibition suppresses tumor cell proliferation, it paradoxically promotes metastasis and invasion, and the mechanisms underlying this effect remain unclear. We evaluated the effects of the CDK4/6 inhibitor palbociclib (PD-0332991) and the bromodomain and extra-terminal (BET) inhibitor JQ1, administered individually and in combination, on human PDAC cell lines and on tumor growth in an orthotopic mouse model. Palbociclib modestly inhibited pancreatic tumor growth but significantly enhanced tumor cell migration, invasion, and epithelial-to-mesenchymal transition (EMT). In contrast, co-treatment with JQ1 potentiated palbociclib's anti-proliferative effects and reversed EMT. Mechanistically, CDK4/6 inhibition activated the canonical Wnt/β-catenin pathway via Ser9 phosphorylation of GSK3β, whereas BET inhibition disrupted the cross-talk between Wnt/β-catenin and TGF-β/Smad signaling. Combined inhibition of CDK4/6 and BET produced a synergistic antitumor effect and . Our findings support a combined therapeutic strategy targeting CDK4/6 and BET proteins to achieve synergistic inhibition of PDAC progression.