Open AccessINK4 Tumor Suppressor Proteins Mediate Resistance to CDK4/6 Kinase Inhibitors
Author(s) -
Qing Li,
Baishan Jiang,
Jiaye Guo,
Hong Shao,
Isabella Del Priore,
Qing Chang,
Rei Kudo,
Zhiqiang Li,
Pedram Razavi,
Bo Liu,
Andrew S. Boghossian,
Matthew G. Rees,
Melissa M. Ronan,
Jennifer A. Roth,
Katherine A. Donovan,
Marta Palafox,
Jorge S. ReisFilho,
Elisa de Stanchina,
Eric S. Fischer,
Neal Rosen,
Violeta Serra,
Andrew Koff,
John D. Chodera,
Nathanael S. Gray,
Sarat Chandarlapaty
Publication year - 2021
Publication title -
cancer discovery
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 6.795
H-Index - 163
eISSN - 2159-8290
pISSN - 2159-8274
DOI - 10.1158/2159-8290.cd-20-1726
Subject(s) - cyclin dependent kinase 6 , cyclin dependent kinase , cyclin dependent kinase 4 , palbociclib , kinase , cancer research , kinome , biology , retinoblastoma protein , cyclin dependent kinase 2 , microbiology and biotechnology , cell cycle , biochemistry , protein kinase a , cancer , cell , metastatic breast cancer , breast cancer , genetics
Cyclin-dependent kinases 4 and 6 (CDK4/6) represent a major therapeutic vulnerability for breast cancer. The kinases are clinically targeted via ATP competitive inhibitors (CDK4/6i); however, drug resistance commonly emerges over time. To understand CDK4/6i resistance, we surveyed over 1,300 breast cancers and identified several genetic alterations (e.g., FAT1 , PTEN , or ARID1A loss) converging on upregulation of CDK6. Mechanistically, we demonstrate CDK6 causes resistance by inducing and binding CDK inhibitor INK4 proteins (e.g., p18 INK4C ). In vitro binding and kinase assays together with physical modeling reveal that the p18 INK4C -cyclin D-CDK6 complex occludes CDK4/6i binding while only weakly suppressing ATP binding. Suppression of INK4 expression or its binding to CDK6 restores CDK4/6i sensitivity. To overcome this constraint, we developed bifunctional degraders conjugating palbociclib with E3 ligands. Two resulting lead compounds potently degraded CDK4/6, leading to substantial antitumor effects in vivo , demonstrating the promising therapeutic potential for retargeting CDK4/6 despite CDK4/6i resistance. SIGNIFICANCE: CDK4/6 kinase activation represents a common mechanism by which oncogenic signaling induces proliferation and is potentially targetable by ATP competitive inhibitors. We identify a CDK6-INK4 complex that is resilient to current-generation inhibitors and develop a new strategy for more effective inhibition of CDK4/6 kinases. This article is highlighted in the In This Issue feature, p. 275 .