Background and aims: Genetic alternation in p53 gene is associated with tumorgenesis, specially breast, colon and lung tumors. To our knowledge, there has been no study on the relationship between TAAAA repeat in the first intron of p53 gene and cancer risk. The aim of this study was to investigate polymorphism of TAAAA in the first intron of p53 gene among colorectal cancer patients and healthy individuals and its relation to risk of colorectal cancer.

Methods: In this research, 151 blood samples of patients with colorectal cancer and 180 healthy samples were studied. After DNA extraction from peripheral blood samples by salting out method and amplification of desired sequence, the number of TAAAA repeats was determined by Polyacrylamide gel electrophoresis and direct sequencing.

Results: In this study, five different length of TAAAA repeat in the range of 6-10 and 13 allele combinations (genotypes) were observed among patients and controls. The most frequent allele in both patients and controls was the 8-TAAAA repeat. Results of homozygous genotypes equal or below 8 are higher among the controlled than the case subjects. In the contrary, number of genotypes equal or higher than 9 (9.10, 9.9) was higher among the patients. Due to the insufficient number of samples, the statistical analysis didnot not show a meaningful relationship. There is no meaningful relationship between genotype, metastasis and age.

Conclusion: Our study did not show a strong association between the TAAAA repeat polymorphism in p53 gene and the risk of colorectal cancer.