CDKN1A and lung cancer: In contrast, the Skp2, located at chromosome 5p13, which is commonly overrepresented in lung cancer, is amplified in 7 (44%) of 16 primary SCLCs and 106 (65%) of 163 NSCLCs, consequently overexpressed.53,54 The amplification of Skp2, encoding Skp2 that is putatively involved in regulating cell cycle progression by controlling the degradation of p27kip1, p21cip1, p57kip2, p130-Rb2, and cyclin E, may play a crucial role in carcinogenesis and development of lung cancer.