Thymidine Kinase 1 Mediates the Synergistic Antitumor Activity of Ubenimex and Celecoxib via Regulation of Cell Cycle in Colorectal Cancer.

Colorectal cancer (CRC) is a common clinical malignant tumor of the digestive system that seriously affects the health and life of patients. Because it is difficult to cure CRC, the strategy of drug combination is often used in clinical therapy. This study mainly revealed that ubenimex and/or celecoxib exerted anti-colon cancer effects in vitro and in vivo, and the efficacy was significantly enhanced when the two drugs were combined. The combination of the two drugs induced significantly stronger cell-cycle arrest than did the single drug, and also enhanced the antitumor efficacy of 5-fluorouracil and its derivatives. At the same time, the expression of thymidine kinase 1 (TK1) protein was decreased through regulating the level of TK1 mRNA treated with celecoxib and/or ubenimex, but the combination drugs exhibited much more reduction of TK1 mRNA and protein as compared with the single agent alone. TK1 may be the molecular target of the combination of two drugs to exert the anti-colorectal cancer effect. In summary, this research demonstrates that celecoxib combined with ubenimex inhibits the development of colorectal cancer in vitro and in vivo, making them a viable combination regimen. SIGNIFICANCE STATEMENT: In this study, our data reveal the great potential of celecoxib combined with ubenimex in the treatment of colorectal cancer, providing new ideas for clinical antitumor drug regimens and theoretical reference for drug development.