Purpose: The retinoblastoma tumor suppressor (RB), a key regulator of cell-cycle progression and proliferation, is functionally suppressed in up to 50% of non-small cell lung cancer (NSCLC). RB function is exquisitely controlled by a series of proteins, including the CyclinD-CDK4/6 complex. In this study, we interrogated the capacity of a CDK4/6 inhibitor, palbociclib, to activate RB function.
Experimental Design and Results: We employed multiple isogenic RB-proficient and -deficient NSCLC lines to interrogate the cytostatic and cytotoxic capacity of CDK 4/6 inhibition in vitro and in vivo We demonstrate that while short-term exposure to palbociclib induces cellular senescence, prolonged exposure results in inhibition of tumor growth. Mechanistically, CDK 4/6 inhibition induces a proapoptotic transcriptional program through suppression of IAPs FOXM1 and Survivin, while simultaneously augmenting expression of SMAC and caspase-3 in an RB-dependent manner.
Conclusions: This study uncovers a novel function of RB activation to induce cellular apoptosis through therapeutic administration of a palbociclib and provides a rationale for the clinical evaluation of CDK 4/6 inhibitors in the treatment of patients with NSCLC.
Recommended CitationChellappagounder, Thangavel; Ettickan, Boopathi; Liu, Yi; McNair, Christopher; Haber, Alex; Perepelyuk, Maryna; Bhardwaj, Anshul; Addya, Sankar; Ertel, Adam; Shoyele, Sunday; Birbe, Ruth; Salvino, Joseph M.; Dicker, Adam P.; Knudsen, Karen E.; and Den, Robert B., "Therapeutic Challenge with a CDK 4/6 Inhibitor Induces an RB-Dependent SMAC-Mediated Apoptotic Response in Non-Small Cell Lung Cancer." (2018). Department of Radiation Oncology Faculty Papers. Paper 119.