MONCPT exerts anti-cancer activities via inducing G2/M arrest and apoptosis in human bladder cancer

Purpose: 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. Materials and Methods: 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. Results: 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 μM) 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 μM, 24 h) caused down-regulation of CDK7, pCdc2, and cyclinB1. Treatment with MONCPT (0.1 μM) 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. Conclusion: 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.