Anti-tumor effect of CDK inhibitors on CDKN2A-defective squamous cell lung cancer cells
Squamous cell lung cancer (SqCLC) is a distinct histologic subtype of non-small cell lung cancer (NSCLC). Although the discovery of driver mutations and their targeted drugs has remarkably improved the treatment outcomes for lung adenocarcinoma, currently no such molecular target is clinically available for SqCLC. The CDKN2A locus at 9p21 encodes two alternatively spliced proteins, p16INK4a (p16) and p14ARF (p14), which function as cell cycle inhibitors. The Cancer Genome Atlas (TCGA) project revealed that CDKN2A is inactivated in 72% of SqCLC cases. In addition, it was found that CDKN2A mutations are significantly more common in SqCLC than in adenocarcinoma. Down-regulation of p16 and p14 by CDKN2A gene inactivation leads to activation of cyclin-dependent kinases (CDKs), thereby permitting constitutive phosphorylation of Rb and subsequent cell cycle progression. Here, we hypothesized that CDK inhibition may serve as an attractive strategy for the treatment of CDKN2A-defective SqCLC.
We investigated whether the CDK inhibitors flavopiridol and dinaciclib may exhibit antitumor activity in CDKN2A-defective SqCLC cells compared to control cells. The cytotoxic effect of the CDK inhibitors was evaluated using cell viability assays, and the induction of apoptosis was assessed using TUNEL assays and Western blot analyses. Finally, anti-tumor effects of the CDK inhibitors on xenografted cells were investigated in vivo.
We found that flavopiridol and dinaciclib induced cytotoxicity by enhancing apoptosis in CDKN2A-defective SqCLC cells, and that epithelial to mesenchymal transition (EMT) decreased and autophagy increased during this process. In addition, we found that autophagy had a cytoprotective role.
Our data suggest a potential role of CDK inhibitors in managing CDKN2A-defective SqCLC.
KeywordsSquamous cell lung cancer CDKN2A CDK inhibitors Flavopiridol Dinaciclib
This study was supported by a grant from the Korea Institute of Radiological and Medical Sciences (KIRAMS), funded by Ministry of Science and ICT (MSIT), Republic of Korea (50474-2018).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 2.C.J. Langer, C. Obasaju, P. Bunn, P. Bonomi, D. Gandara, F.R. Hirsch, E.S. Kim, R.B. Natale, S. Novello, L. Paz-Ares, M. Perol, M. Reck, S.S. Ramalingam, C.H. Reynolds, M.A. Socinski, D.R. Spigel, H. Wakelee, C. Mayo, N. Thatcher, Incremental innovation and progress in advanced squamous cell lung cancer: Current status and future impact of treatment. J. Thorac. Oncol. 11, 2066–2081 (2016)CrossRefGoogle Scholar
- 3.M.A. Socinski, C. Obasaju, D. Gandara, F.R. Hirsch, P. Bonomi, P.A. Bunn Jr., E.S. Kim, C.J. Langer, R.B. Natale, S. Novello, L. Paz-Ares, M. Perol, M. Reck, S.S. Ramalingam, C.H. Reynolds, D.R. Spigel, H. Wakelee, N. Thatcher, Current and emergent therapy options for advanced squamous cell lung cancer. J. Thorac. Oncol. 13, 165–183 (2018)CrossRefGoogle Scholar
- 9.A. Pacifico, G. Leone, Role of p53 and CDKN2A inactivation in human squamous cell carcinomas. J. Biomed. Biotechnol. 2007, 43418 (2007)Google Scholar
- 11.F.J. Stott, S. Bates, M.C. James, B.B. McConnell, M. Starborg, S. Brookes, I. Palmero, K. Ryan, E. Hara, K.H. Vousden, G. Peters, The alternative product from the human CDKN2A locus, p14(ARF), participates in a regulatory feedback loop with p53 and MDM2. EMBO J. 17, 5001–5014 (1998)CrossRefGoogle Scholar
- 17.D. Parry, T. Guzi, F. Shanahan, N. Davis, D. Prabhavalkar, D. Wiswell, W. Seghezzi, K. Paruch, M.P. Dwyer, R. Doll, A. Nomeir, W. Windsor, T. Fischmann, Y. Wang, M. Oft, T. Chen, P. Kirschmeier, E.M. Lees, Dinaciclib (SCH 727965), a novel and potent cyclin-dependent kinase inhibitor. Mol. Cancer Ther. 9, 2344–2353 (2010)CrossRefGoogle Scholar
- 20.C. Umbreit, J. Flanjak, C. Weiss, P. Erben, C. Aderhold, A. Faber, J. Stern-Straeter, K. Hoermann, J.D. Schultz, Incomplete epithelial-mesenchymal transition in p16-positive squamous cell carcinoma cells correlates with beta-catenin expression. Anticancer Res. 34, 7061–7069 (2014)PubMedGoogle Scholar
- 28.C. Capparelli, B. Chiavarina, D. Whitaker-Menezes, T.G. Pestell, R.G. Pestell, J. Hulit, S. Ando, A. Howell, U.E. Martinez-Outschoorn, F. Sotgia, M.P. Lisanti, CDK inhibitors (p16/p19/p21) induce senescence and autophagy in cancer-associated fibroblasts, "fueling" tumor growth via paracrine interactions, without an increase in neo-angiogenesis. Cell Cycle 11, 3599–3610 (2012)CrossRefGoogle Scholar
- 39.J. Flynn, J. Jones, A.J. Johnson, L. Andritsos, K. Maddocks, S. Jaglowski, J. Hessler, M.R. Grever, E. Im, H. Zhou, Y. Zhu, D. Zhang, K. Small, R. Bannerji, J.C. Byrd, Dinaciclib is a novel cyclin-dependent kinase inhibitor with significant clinical activity in relapsed and refractory chronic lymphocytic leukemia. Leukemia 29, 1524–1529 (2015)CrossRefGoogle Scholar
- 41.C. Hu, T. Dadon, V. Chenna, S. Yabuuchi, R. Bannerji, R. Booher, P. Strack, N. Azad, B.D. Nelkin, A. Maitra, Combined inhibition of cyclin-dependent kinases (dinaciclib) and AKT (MK-2206) blocks pancreatic tumor growth and metastases in patient-derived xenograft models. Mol. Cancer Ther. 14, 1532–1539 (2015)CrossRefGoogle Scholar