CDKN2A and squamous cell lung carcinoma: On the other hand, the oncogene nuclear factor erythroid-derived 2-like 2 (NFE2L2) (19%) and the tumor suppressor genes TP53 (90%) and cyclin-dependent kinase inhibitor 2A (CDKN2A) (70%) are reported to be the most frequently altered genes in lung squamous cell carcinoma patients [6].