.1. Chinese Population Ugt1a Gene Polymorphism And Irinotecan The Kang Toxicity Study. Bevacizumab The Sn-38 Inhibits Colorectal Cancer And Vascular Endothelial Cell Proliferation And Its Mechanism Study

Fluorouracil (5FU) was the only effective chemotherapeutic drug for colorectal cancer over the past 40 years. Much exciting progress has occurred since 1990's. Two new drugs, oxaliplatin and irinotecan, incombination with FU/LV, composed FOLFOX and FOLFIRI regimen have demonstrated impressive response and survival improvement,now have been widely accepted for treatment of colorectal cancer. Bevacizumab, a humanized antibody directed against the VEGF, in combination with chemotherapy led to an impressive, statistically significant increase in response rate and prolongation in median overall survival. The NCCN guideline recommended the use of bevacizumab in combination with any fluorouracil-containing regimen as initial therapy for patients with advanced colorectal cancer. However, Bevacizumab appears to be inactive as a single agent, it is unclear whether its activity is generated primarily by an antiangiogenic mechanism or by other mechanism when combined with cytotoxic drugs. How best to incorporate this new target agent into chemotherapy, and how to choose suitable treatment for individual patients remains to be determined.In the first part of this study, we assessed the polymorphisms of UGT1A gene in Chinese, and analyzed the correlation between UGT1A polymorphisms and CPT-11 toxicity in colorectal cancer patients. From Sep. 2005 to Feb.2007, 70 patients with advanced colorectal cancer were treated with FOLFIRI regimen. Polymorphisms analysis were performed in all these patients and 100 healthy subjects. Genomic DNA was extracted from peripheral blood and genotyped using PCR and direct sequencing. 14 patients exhibiting grade 3~4 neutropenia (20%), 16 patients experienced grade2~4 diarrhea (22.9%), including only 4 patients with grade 3~4 diarrhea (5.7%).Compared with TA6/7 and TA7/7, UGT1A1*28 wild genotype TA6/6 were significantly associated with reduced toxicity (42.1%vs15.7%, p=0.027). There was no significant difference on the distribution of UGT1A genotypes between colorectal cancer patients and healthy subjects. This finding suggest that Chinese patients with CRC exhibit low incidence of CPT-11-related diarrhea due to high frequency of UGT1A1*28 wild genotype TA6/6.In the second part of this study, we investigated the optimal combination schedule and possible mechanisms of Bevacizumab and irinotecan's active metabolite SN-38. Inhibition of cell proliferation was evaluated by MTT assay. The mRNA expression of HIF-1αand VEGF were assessed by RT-PCR. The protein expression of HIF-1α, ERK1/2 and AKT, VEGF were evaluated by Western blot analysis and ELISA assay. Among different combination schedules, Bevacizumab gave after SN-38 show most synergistic effect. Under hypoxic conditions, the expression levels of HIF-1αand VEGF increased as time accumulated, Bevacizumab combined with SN-38 almost completely inhibited the expression of HIF-1αand VEGF. Moreover, the MAP kinase pathway was involved in the drug modulation of HIF-1αand VEGF. These findings suggest the synergistic effect of Bevacizumab and SN-38 was related to drug modulation of the MAP kinase pathway. Sequential administration of SN-38 followed by Bevacizumab was the best combination schedule.In conclusion, our study suggests irinotecan containing regimen could be used more extensively in Chinese patients. Moreover, when Bevacizumab added into irinotecan containing regimen, synergistic effect can be obtained by Sequential administration of SN-38 followed by Bevacizumab, The probably mechanism is synergistic modulation of HIF-1αand MAP kinase pathway.