Polymorphic GT Dinucleotide Repeat in the PIK3CA Gene and its Association with Colorectal Cancer Risk

The PIK3CA oncogene, which encodes p110α, is one of the most mutated genes in human cancers such as colorectal. A polymorphic GT dinucleotide repeat exists in intron 1 of the PIK3CA gene. Till this research, there were no study on polymorphism of PIK3CA gene microsatellites and their relationship with cancer risk. In the present study, we investigated GT repeat polymorphism in the intron 1 of this gene among patients with colorectal cancer and healthy individuals and evaluated the association between this polymorphism and the potential genetic susceptibility to the development of colorectal cancer.

Peripheral blood samples were collected from 103 patients with colorectal cancer and 100 healthy blood donors. After DNA extraction, GT dinucleotide region was amplified using polymerase chain reaction (PCR) technique and the number of GT repeats was determined via polyacrylamide gel electrophoresis.

Eight distinct alleles were identified in these subjects, ranging in size from 13 to 20 GT repeats. People with two alleles shorter than 17 GT repeat had a significantly higher risk of developing colorectal cancer (OR = 3.65, P = 9 × 10-6); in contrast, people with two alleles longer than 16 GT repeat were at a significantly lower risk of colorectal cancer (OR = 0.18, P = 3.5 × 10-6).

Our findings indicate significant relationship between the numbers of repetitive sequences in intron 1 of PIK3CA gene and the risk of colorectal cancer.