The potent anti−cancer capability of a novel CPT derivarate, 10−methoxy−9−nitrocamptothecin (MONCPT), has been demonstrated in our previous studies. The present study focuses on the in vitro and in vivo anti−cancer activities, the cell cycle arrest− and apoptosis−induction abilities of MONCPT on human bladder uroepithelial carcinoma 5637 cell line.

MTT assay and flow cytometric analyses were employed to evaluate the cell proliferation, cell cycle distribution and apoptosis of MONCPT−treated 5637 cells. Using 5637 xenografted nuce mice models, the in vivo anti−cancer capability of MONCPT were examined, as indicated by the decreased tumor volume and tumor weight. The effect of MONCPT on some of the key regulators of G2/M checkpoint and apoptosis, including CDKI−CDK−cyclin cascade, Kip1/p27 and Cip1/p21, PARP were examined using western blotting.

The more potent anti−tumor activities of MONCPT than SN−38 against 5637 cells were indicated by the IC50 value (48 h) of 226.7 +/− 0.5 nM and 2031.0 +/− 0.5 nM, respectively. MONCPT treatment (0.1 microM) for 24 h caused the increment of G2/M population from 7.94% to 75.52%, indicating that MONCPT significantly triggered G2/M arrest. Moreover, MONCPT exposure (0.1 microM, 24 h) caused down−regulation of CDK7, p−Cdc2, and cyclinB1. Treatment with MONCPT (0.1 microM) for 48 h obviously induced apoptosis of 5637 cells, which was revealed by the accumulation of Annexin V−positive cells. The superior anti−tumor capabilities of MONCPT were further demonstrated in the human 5637 xenograft−bearing mice model. The administration of MONCPT at the dosages of 5, 10, 20 mg/kg for 15 days significantly inhibited the tumor growth with the inhibition rates of 64.8%, 86.2% and 96.5%, respectively.

The present study displayed the significant in vitro anti−proliferative abilities of MONCPT on human ladder cancer 5637 cells, and in vivo tumor−inhibitory activities on xenograft models. In addition, MONCPT was demonstrated to induce G2/M arrest and apoptosis in 5637 cells. Our findings provide evidences for the anti−tumor activity of MONCPT in the ongoing preclinical assessment.

PMID: 20095141 [PubMed − in process] Source: National Library of Medicine.