Genetic mutational analysis of β-catenin gene affecting GSK-3β phosphorylation plays a role in gallbladder carcinogenesis: Results from a case control study

Abstract

This manuscript has reported different mutations of β-catenin gene in gallbladder cancer patients which affect GSK-3β phosphorylation site. Purpose: Gallbladder carcinoma (GBC) is a relatively rare and fatal cancer with poor prognosis. The molecular mechanism of gallbladder carcinogenesis is still not clear. Wnt signaling pathway is a highly conserved pathway that regulates proliferation, differentiation, migration, genetic stability, apoptosis, and stem cell renewal. β-catenin plays major role in Wnt signaling and aberrations in β-catenin has found to be involved in several cancers pathogenesis. This study was carried out to document the mutations of β-catenin gene in gallbladder cancer and to evaluate its possible role in gallbladder carcinogenesis. Methods: PCR-SSCP (Single Stranded Conformation Polymorphism) for ctnnb1 was performed in 50 patients each of gallbladder cancer, cholelithiasis and 50 healthy controls. Samples that showed variation in banding pattern were sequenced. Results: Variation in banding pattern was observed in 9 (18%) samples of GBC, 4 (8%) of cholelithiasis and 2 (4%) of control. Sequencing analysis showed 9 novel mutations of ctnnb1 in exon 3 in 18% of gallbladder cancer (χ2 = 5.778; p < 0.05). Six point mutations, 1 deletion and 1 insertion mutation were found in 9 cases of gallbladder cancer. All point mutations were mis-sense mutation that affected highly conserved serine or threonine region that is important for GSK-3β phosphorylation. Conclusion: Findings of the study suggests that high frequency of non synonymous mutations of β-catenin gene (ctnnb1) occurs in patients with gallbladder cancer. As these mutations mainly effect GSK 3β phosphorylation, it may be concluded that this might be an important step in gallbladder carcinogenesis. These β-catenin mutations lead to Wnt pathway activation and appear to have a role in progression from inflammation to cancer in gallbladder.

Keywords

• β-catenin
• Cholelithiasis
• Gallbladder cancer
• Single Stranded Conformation Polymorphism
• Wnt signalling pathway