Two novel camptothecin derivatives inhibit colorectal cancer proliferation via induction of cell cycle arrest and apoptosis in vitro and in vivo.

At present, chemotherapy is still to be the preferred and most significant therapeutic strategy for cancer patients in clinical practice. Although Camptothecin (CPT) has been discovered for over half century, a series of CPT derivatives such as Topotecan (TPT) and irinotecan (CPT-11) have been approved and are still to be the first-line medicines for clinical application. Up to now, the topoisomerase 1 inhibitor continues to be a significant drug development research field. Based on previous study of the structure-activity relationship, we consider that the introduction of lipophilic group at C7 position can prolong the retention time and the hydroxyl esterification at C20 can eliminate the hydrogen bond interaction, stabilize the E-lactone form and promote the anti-cancer effect. In this study, we carried out an optimization at C7 and C20 positions to afford two CPT derivatives 3g and 3j. Firstly, we predicted the possibly binding sites of two compounds with topoisomerase 1 by molecular docking. Then we evaluated the anti-proliferation effect of the two novel derivatives and compared the IC50 with CPT-11. Furthermore, the induction of cell cycle arrest and apoptosis was explored through karyomorphology, flow cytometry (FCM) and Western blot analysis. At last, we evaluated the anti-cancer effect and detected the mechanism in colorectal cancer xenograft model. In brief, all the data showed that the novel CPT derivatives (3g and 3j) could inhibit colorectal cancer proliferation via induction of cell cycle arrest and apoptosis in vitro and in vivo. It suggested that the two agents may be a new potential therapeutic strategy in the future.