The Study of TAAAA Polymorphism in p53 Gene and Its Association with Breast Cancer

Genetic alternation in p53 gene is associated with tumorgenesis, especially in breast, colon and lung tumors. Somatic mutation of the p53 gene is the most common genetic alteration seen in human cancers. To our knowledge, before this research, there was no study on the relationship of TAAAA repeat in the first intron of p53 gene and cancer risk. The purpose of this study was to investigate the polymorphism of TAAAA in the first intron of p53 gene among patients with breast cancer and healthy individuals and its relation to risk of breast cancer.

Peripheral blood samples were collected from 200 women with breast cancer and 200 healthy women. After DNA extraction from peripheral blood samples via salting out method and amplification of desired sequence via polymerase chain reaction (PCR), the number of TAAAA repeats was determined using polyacrylamide gel electrophoresis and direct sequencing.

Five different length of TAAAA repeat in the range of 6-10 and 11 allele combinations (genotypes) were observed among patients and controls. The most frequent allele in both patients and controls was the 8-TAAAA repeat. Women who were homozygous for (TAAAA)7 or heterozygous for (TAAAA)6 were at higher risk of developing breast cancer. The allelic length of p53 polymorphisms had no significant effect on the metastasis, the expression of estrogen receptors, progesterone receptors and ErbB2 (HER2) and age of the onset.

Our study shows strong association between the TAAAA repeat polymorphism in p53 gene and risk of breast cancer.