Abstract
Cyclin-dependent kinase 2 (CDK2) has been reported to be overexpressed in human colorectal cancer; it is responsible for the G1‑to‑S‑phase transition in the cell cycle and its deregulation is a hallmark of cancer. The present study was the first to use idock, a free and open‑source protein‑ligand docking software developed by our group, to identify potential CDK2 inhibitors from 4,311 US Food and Drug Administration‑approved small molecular drugs with a re‑purposing strategy. Among the top compounds identified by idock score, nine were selected for further study. Among them, adapalene (ADA; CD271,6‑[3‑(1‑adamantyl)‑4‑methoxyphenyl]‑2‑naphtoic acid) exhibited the highest anti‑proliferative effects in LOVO and DLD1 human colon cancer cell lines. Consistent with the expected properties of CDK2 inhibitors, the present study demonstrated that ADA significantly increased the G1‑phase population and decreased the expression of CDK2, cyclin E and retinoblastoma protein (Rb), as well as the phosphorylation of CDK2 (on Thr‑160) and Rb (on Ser‑795). Furthermore, the anti‑cancer effects of ADA were examined in vivo on xenograft tumors derived from DLD1 human colorectal cancer cells subcutaneously inoculated in BALB/C nude mice. ADA (20 mg/kg orally) exhibited marked anti‑tumor activity, comparable to that of oxaliplatin (40 mg/kg), and dose‑dependently inhibited tumor growth (P<0.05), while combined administration of ADA and oxaliplatin produced the highest therapeutic effect. To the best of our knowledge, the present study was the first to indicate that ADA inhibits CDK2 and is a potential candidate drug for the treatment of human colorectal cancer.