Background: Mutations in p53 gene are found in a majority of human malignancies and usually occur in the exons 5, 6, 7 and 8. Mutated p53 protein is more stable and gets accumulated in the cells that induce the host to develop anti-p53 antibodies in sera of cancer patients.
Aim: This study is aimed to observe the frequency and nature of mutations in exons 5-8 of p53 gene and to evaluate its correlation with prevalence of serum p53 antibodies in Indian patients with gallbladder cancer (GBC).
Methods: Mutation studies were done in cancer tissues obtained from 62 patients with proven GBC (40 cytologically proven cases and 22 resected gallbladder cancer tissues) by polymerase chain reaction (PCR), restriction fragment length analysis (RFLP) and single strand conformation polymorphism (SSCP). Presence of serum p53 antibodies was determined using highly specific enzyme linked immunosorbent assay (ELISA) kit in 50 patients with GBC and 30 patients of cholelithiasis. Clinicopathologic characteristics of these patients were given attention.
Results: Antibodies to p53 protein was present in the serum in 34% (17/50) of GBC patients and in 3.3% (1/30) patients with cholelithiasis (p<0.018). RFLP failed to detect common mutations in the exons 5- 8 of the p53 gene in 62 samples. Using SSCP analysis we could detect frameshift mutation in p53 gene in 2 of 22 (9.1%) GBC cases. Mutated samples were sequenced and found to have insertion of adenine at codon 271 (GAG) in exon 8 region.
Conclusion: Our results show that 1/3rd of the north Indian patients with GBC have antibodies to p53 protein. The commonest identifiable alteration in the p53 gene was a frameshift mutation at codon 271.