J Cancer Res Clin Oncol (2010) 136:437–445 DOI 10.1007/s00432-009-0674-5 123 ORIGINAL PAPER P53 and p38 MAPK pathways are involved in MONCPT-induced cell cycle G2/M arrest in human non-small cell lung cancer A549 Chong Zhang · Hong Zhu · Xiaochun Yang · Jianshu Lou · Difeng Zhu · Wei lu · Qiaojun He · Bo Yang Received: 7 December 2008 / Accepted: 17 August 2009 / Published online: 2 September 2009  Springer-Verlag 2009 Abstract Purpose In previous research, we found that 10-methoxy- 9-nitrocamptothecin (MONCPT) possessed potent anti- tumor activity in A549 cells in vitro and in vivo. In this paper, our purpose is to investigate the mechanism of MONCPT-induced cell cycle arrest in A549 cells. Methods Cell cycle distribution was measured using Xow cytometry (FCM). Protein expression and RNA expression were analyzed by western blotting and real-time PCR, respectively. SiRNA technology was introduced to silence the expression of p53 and p38. Results FCM showed that MONCPT induced cell cycle G2/M arrest in time- and dose-dependent manner. The levels of feedback loop proteins PLK-1, Cdc25C, and cyclinB1 were obviously increased from 12 to 24 h, and then reduced from 36 to 48 h by MONCPT (100.0 nM). Moreover, down- regulation of p-AKT in A549 cells was seen after treated with 100.0 nM MONCPT for 12–48 h. Over-expression of p53 and p21 in A549 cells treated with MONCPT was observed in time-dependent manner. When wild type p53 expression was speciWcally inhibited by RNA-interference, A549 cells treated with MONCPT delayed the onset of G2/ M arrest; meanwhile p-ERK and Cdc2 were up-regulated while p21 and CDK7 were down-regulated in A549 cells treated with MONCPT and p53 SiRNA transfection in con- trast to cells treated with 100.0 nM MONCPT alone. In addition, our results exhibited that MONCPT obviously down-regulated p-ERK, JNK, p-JNK, and p-p38. Treatment with p38 mitogen-activated protein kinase (MAPK) SiRNA obviously inhibited p38 MAPK and delayed the G2/M arrest induced by 50.0 nM MONCPT after 48 h. Conclusion Cell cycle regulators, AKT, p53, and MAPK, as therapeutic targets for MONCPT to induce cell cycle G2/M arrest in the context of anticancer therapy. Keywords MONCPT · G2/M-arrest · p53 · p38 · AKT Introduction Lung cancer is the most common cancer and the leading cause of cancer death, with more than a million new cases and a million deaths every year. There are two major types: non-small cell lung cancer (NSCLC) and small cell lung cancer, so named because of how the cells look under a microscope. NSCLC comprises over approximately 75% of all lung cancers. Despite advances in chemotherapy, the average 5-year survival rate of the patients with advanced NSCLC remains extremely poor (Koshimune et al. 2007). Surgery is the treatment of choice, but only about 20% of tumors are suitable for potentially curative resection (Non- small Cell Lung Cancer Collaborative Group 1995). There- fore, it is critical to search for novel chemotherapeutic agents that can inhibit the growth of human NSCLC cells. Camptothecin (CPT), an alkaloid with antitumor eYcacy, was isolated from the Chinese tree Camptotheca acuminata and then evaluated clinically in the United States. However, it showed severe toxicity in animal experiments and in clinical C. Zhang · H. Zhu · X. Yang · J. Lou · D. Zhu · Q. He (&) · B. Yang (&) Institute of Pharmacology and Toxicology, College of Pharmaceutical Sciences, Zhejiang University, #388 Yuhangtang Road, Hangzhou, Zhejiang 310058, China e-mail: qiaojunhe@zju.edu.cn B. Yang e-mail: yang924@zju.edu.cn W. lu Institute of Medicinal Chemistry, Department of Chemistry, East China Normal University, Shanghai, China