Lack of association of intron 3 16 bp polymorphism of TP53 with breast cancer among Iranian-Azeri patients.

BACKGROUND: p53 gene is a well-known tumor suppressor gene that has several polymorphisms in both its exons and introns. It has been suggested that intron 3 16 bp duplication polymorphism may affect the gene function resulting in reduction or suppression of p53 anti tumor activity. In most case control studies a duplicated allele has been noticeably more frequent in cases rather than controls but there are also conflicting results. The aim of this study was to assess the association of intron 3 16 bp duplication polymorphism of p53 with breast cancer risk among Iranian-Azeri population. We also analyzed the clinicopathological information of patients as an epidemiological description of breast cancer in the north-west of Iran. MATERIALS AND METHODS: This case-control study was performed on 221 breast cancer patients and 170 controls. Genomic DNA was extracted from peripheral blood samples and tumor tissues. p53 PIN3 genotype was determined using electrophoresis of PCR products on 8% non-denaturing polyacrylamide gels and silver staining. RESULTS: In the control and case groups, respectively, 62.9% and 61.1% had no 16 bp insertion (A1A1 genotype), 7.1% and 7.7% had insertion in both p53 alleles (A2A2) and 30% and 31.2% were heterozygous (A1A2). There was no significant difference between genotype frequencies as well as allelic frequencies in two case and control groups. CONCLUSIONS: According to the result of the present study, the intron 3 16 bp duplication polymorphism of p53 could not be assessed as a marker of risk factor for predisposition to breast cancer in Azeri population. However, a high frequency of A2 allele (22.1%) in our population suggested that intron 3 16 bp duplication polymorphism may be a valuable marker for study in other cancers with well designed large groups.

Overlapping region of p53/wrap53 transcripts: mutational analysis and sequence similarity with microRNA-4732-5p.

BACKGROUND: Although the majority of investigations concerned with TP53 and its protein have focused on coding regions, recently a set of studies highlighted significant roles of regulatory elements located in p53 mRNA, especially 5 ? UTR. The wrap53α transcript is one of those that acts as a natural antisense agent, forming RNA-RNA hybrids with p53 mRNA and protecting it from degradation. MATERIALS AND METHODS: In this study, we focused on the mutation status of exon 1α of the WRAP53 gene (according to exon 1 of p53) in 160 breast tumor tissue samples and conducted a bioinformatics search for probable miRNA binding site in the p53/wrap53 overlapping region. Mutations were detected, using single stranded conformation polymorphism (SSCP) and sequencing. We applied the miRBase database for prediction of miRNAs which target overlapping region of p53/wrap53 transcripts. RESULTS: Our results showed all samples to have wild type alleles in exon 1 of TP53 gene. We could detect a novel and unreported intronic mutation (IVS1+ +56, G>C) outside overlapping regions of p53/wrap53 genes in breast cancer tissues and also predict the presence of a binding site for miR-4732-5p in the 5' UTR of Wrap53 mRNA. CONCLUSIONS: From our findings we propose designing further studies focused on overexpression of miRNA-4732-5p and introducing different mutations in the overlapping region of wrap53 and p53 genes in order to study their effects on p53 and its δN isoform (δ40p53) expression. The results may provide new pieces in the p53 targeting puzzle for cancer therapy.