中文摘要：

目的：PIK3CA基因编码IA型磷脂酰肌醇-3-激酶（P13Ks）的p110催化亚基，致癌性的PIK3CA突变可通过激活P13K通路参与结直肠癌的发生发展。PIK3CA在西方结直肠癌患者中有较高的突变频率，但其在中国人结直肠癌中的突变情况尚不明确。本研究旨在探讨中国人结直肠癌中PIK3CA基因的突变频率、分布特点及其与结直肠癌的关系。方法：采用PCR产物直接测序法，对79例中国结直肠癌患者肿瘤标本中PIK3CA基因外显子9和外显子20中的突变进行检测分析。结果：在79例肿瘤标本中检出PIK3CA基因突变率为8．9％（7／79），其中外显子9突变率为6．3％（5／79），外显子20突变率为2．5％（2／79），其突变热点分布与既往文献报道基本相符。结论：中国人结直肠癌中存在一个PⅨ3翻基因突变的亚群，其E542K、E545K和H1047R突变，与以往报道的该基因的致癌性突变相一致，可能是这部分结直肠癌中P13K信号通路激活的原因。

英文摘要：

OBJECTIVE： PIK3CA gene encodes the p110 α catalytic subunit of PI3K, and its oncogenic mutation is involved in tumorigenesis of colorectal cancer （CRC） through activating of PI3K pathway. Frequent mutation of the PIK3CA gene in Western CRC has been reported; however, the mutations status of the gene in Chinese CRC is unclear. The aim of the study was to evaluate the mutation status of PIK3CA gene in Chinese patients with CRC. METHODS ： PIK3CA gene mutations were analyzed in 79 colorectal tumors by PCR and DNA sequencing. RESULTS： PIK3CA gene mutations were detected in 8.9% （7/79） of tumor samples 6.3% （5/79） and 2.5% （2/79） of point mutations were found in exon 9 and exon 20, respectively. The distribution pattern of PIK3CA gene mutations was consistent with previous studies. CONCLUSION： A subset of Chinese CRC with PIK3CA gene mutations was identified in the study. Oncogenic mutation of PIK3CA gene may contribute to PI3K pathway activation in the corresponding tumors.