SKP2 and gastric cancer: However, in gastric cancer, in cells such as AGS, MKN7 and NUGC-3, CLDN6 silencing contributes to cell cycle arrest at the G1-S checkpoint through increasing p21WAF1/Cip1 and p27Kip1 and decreasing S-phase kinase-associated protein 2 (SKP2) protein levels, which are well-known cell cycle regulators [26].