CDK4/6 Inhibition Induces Senescence and Enhances Radiation Response by Disabling DNA Damage Repair in Oral Cavity Squamous Cell Carcinoma

• Published in: Cancers 2023-03, Vol.15 (7), p.2005
• Main Authors: Shrivastava, Nitisha, Chavez, Claudia Gutierrez, Li, Daniel, Mehta, Vikas, Thomas, Carlos, Fulcher, Cory D, Kawachi, Nicole, Bottalico, Danielle M, Prystowsky, Michael B, Basu, Indranil, Guha, Chandan, Ow, Thomas J
• Format: Article
• Language: English
• Subjects: Apoptosis; Cancer therapies; Care and treatment; CDKN2A gene; Cell cycle; Complications; Cyclin-dependent kinase 4; Cyclin-dependent kinases; Deoxyribonucleic acid; DNA; DNA damage; DNA repair; Fibroblasts; Head & neck cancer; Homologous recombination; Human papillomavirus; INK4a protein; Institutional repositories; Kinases; Methods; Mouth cancer; Non-homologous end joining; Oral carcinoma; Oral cavity; Organoids; p16 Protein; Proteins; Radiation; Radiotherapy; Senescence; siRNA; Software; Spheroids; Squamous cell carcinoma; Tumors
• ISSN: 2072-6694; 2072-6694
• DOI: 10.3390/cancers15072005

HPV(-) OCSCC resists radiation treatment. The gene, encoding p16INK4A, is commonly disrupted in OCSCC. p16 inhibits CDK4/CDK6, leading to cell cycle arrest, but the biological sequelae of CDK4/6 inhibition in OCSCC remains understudied. This study examines whether inhibition of CDK4/6 enhances radiation response in OCSCC. MTT assays were performed in OCSCC cell lines HN5 and CAL27 following treatment with palbociclib. Clonogenic survival and synergy were analyzed after radiation (RT-2 or 4Gy), palbociclib (P) (0.5 µM or 1 µM), or concurrent combination treatment (P+RT). DNA damage/repair and senescence were examined. CDK4/6 were targeted via siRNA to corroborate P+RT effects. Three-dimensional immortalized spheroids and organoids derived from patient tumors (conditionally reprogrammed OCSCC CR-06 and CR-18) were established to further examine and validate responses to P+RT. P+RT demonstrated reduced viability and synergy, increased β-gal expression (~95%), and ~two-fold higher γH2AX. Rad51 and Ku80 were reduced after P+RT, indicating impairment of HR and NHEJ. siCDK4/6 increased senescence with radiation. Spheroids showed reduced proliferation and size with P+RT. CR-06 and CR-18 further demonstrated three-fold reduced proliferation and organoids size with P+RT. Targeting CDK4/6 can lead to improved efficacy when combined with radiation in OCSCC by inducing senescence and inhibiting DNA damage repair.