Analysis of the mutations of the APC gene in 79 Chinese patients with colorectal cancer

Abstract

Objective To investigate the mutations of adenomatous polyposis coli (APC) gene in Chinese patients with colorectal cancer (CRC). Methods APC gene mutations in the mutation cluster region (MCR) were examined in 79 colorectal tumors by PCR and DNA sequencing. Results Twenty-five (31.6%) somatic mutations were detected in the APC gene as a whole. Among them sixteen (20.3%) were point mutations, which includes, 12 nonsense mutations and 4 missense mutations. The other 9(11%) tumors had frameshift mutations due to a deletion or an insertion. Overall, twenty-one (27%) mutations resulted in the truncation of the APC protein, which accounted for 84% of the total mutations. The mutations in the APC gene were clustered within two small regions of the MCR, that is, codon 1281-1352 and 1411-1465. The frequencies of these two regions were 16.5%(13/79) and 15.2%(12/79), respectively. The mutation rate of codon 1286、1306、1421 and 1450 was relative higher in our cohort. Furthermore, statistical analysis revealed that mutations of the APC gene were not correlated with the age, sex, tumor location, tumor type, histology differentiated degree, depth of invasion, lymph node metastasis, or clinical stage. Conclusion APC gene mutations are frequent in Chinese patients with CRC, and truncating mutation is the predominant type. In addition, there are two small regions with higher mutation rate and four potential mutation hot spots of the APC gene in this cohort. Key words: Colorectal cancer; Adenomatous polyposis coli; Gene mutation