SarCNU-induced G2/M arrest in hepatoma cells is mediated by a p53-independent phosphorylation of cdc-2 at Tyr15

P53 and p38 MAPK pathways are involved in MONCPT-induced cell cycle G2/M arrest in human non-small cell lung cancer A549

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 flow 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 specifically 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 contrast 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.

Xenografts of human hepatocellular carcinoma: a useful model for testing drugs

PURPOSE

Our aims were to establish and characterize primary human hepatocellular carcinoma xenografts. They were used to screen new drugs and improve our current treatment regimens used in hepatocellular carcinoma.

EXPERIMENTAL DESIGN

Primary hepatocellular carcinomas were used to create the xenografts. Western blotting was used to determine the changes in proteins in these xenografts before and after therapies. Apoptotic and cell proliferation were analyzed by immunohistochemistry.

RESULTS

Seven lines of xenografts were established from primary human hepatocellular carcinomas. Lines 4-1318, 2-1318, 2006, and 26-1004 grew rapidly in severe combined immunodeficient (SCID) mice and doubled its volume every 48 to 72 hours. Series 5-1318 (5-1318, 30-1004, and 29-1104) grew relatively slowly in SCID mice and required approximately 6 to 10 days to double its tumor volume. Western blot analysis revealed that the growth rate of these xenografts was associated with abnormal expression of proteins associated with the cell cycle, signaling pathways, and tumor suppressor genes. Although hepatocellular carcinoma xenografts expressed the receptors for androgens, estrogens, and progesterone, their growth rate was not affected by either castration or sex steroid hormone supplementation. Cisplatin, oxaliplatin, vitamin D analogue EB1089, and Iressa had no effects on the growth rate in SCID mice. Although 5-fluorouracil exerted mild growth inhibition of these xenografts, i.p. delivery of 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) or doxorubicin resulted in a significant growth inhibition. Doxorubicin-induced growth suppression was associated with elevation of p53 and p21(Cip1/Waf1). In addition to up-regulation of p53 and p21(Cip1/Waf1), SarCNU also increased the levels of phosphorylated cdc-2 at Tyr15.

CONCLUSION

Hepatocellular carcinoma xenografts are powerful tools for screening drugs and SarCNU may be useful in the treatment of this fatal disease.