Frequent promoter hypermethylation and down regulation of BNIP3: An early event during gallbladder cancer progression.

Background: Epigenetic alterations have been reported as one of the risk factors of gallbladder cancer. Promoter hypermethylation is associated with high incidence and poor prognosis of GBC. Bcl-2/adenovirus E1B 19 kDa interacting protein 3 is a pro-apoptotic protein member of Bcl-2 family.

Aims: Present study was aimed to investigate expression profile and promoter methylation status of BNIP3 in GBC and its correlation with clinico-pathological parameters.

Methods: The expression analysis and methylation status of BNIP3 was performed by semi-quantitative reverse transcription polymerase chain reaction and Methylation-specific polymerase chain reaction respectively in 84 GBC patients and 29 gallstone tissues (used as normal controls).

Results: We demonstrate down regulation of BNIP3 in 56% of the GBC samples. BNIP3 promoter is also frequently hypermethylated (69%) in GBC samples. Interestingly, we found that 69% (40/58) of the BNIP3 promoter hypermethylated samples had also reduced expression of BNIP3. Our data demonstrate significant correlation of the mRNA expression and promoter hypermethylation with late stage and nodal metastasis. Hypermethylation of BNIP3 promoter is associated with low overall survival period.

Conclusion: Our results suggest that promoter hypermethylation is an early event and can be a frequent mechanism for downregulation of BNIP3 in GBC.