Background: Aberrant methylation of tumor-suppressor genes is associated with a loss of gene function that can afford selective growth advantages to sporadic neoplastic cells arising during gallbladder inflammation.
Methods: Fifty-four gallbladder neoplasms were selected from tumor banks in the United States and Chile. Each of the neoplasms was subjected to methylation-specific polymerase chain reaction to detect promoter methylation associated with six candidate tumor-suppressor genes (p16, APC, methylguanine methyltransferase, hMLH1, retinoic acid receptor beta-2, and p73) implicated in multiple human cancer types.
Results: Aberrant methylation of any of the six candidate tumor-suppressor genes was detected in 72% of the gallbladder neoplasms, 28% of the cases of chronic cholecystitis, and in only 1 of the 15 normal gallbladder controls. The four most commonly methylated genes in the gallbladder cancers were p16 (56%), p73 (28%), APC (27%), and hMLH1 (14%). Significant differences in gene methylation were discovered between US gallbladder cancers and those from Chile, where gallbladder cancer is one of the leading causes of cancer-related deaths. APC methylation was present in 42% of the US cases but in only 14% of the Chilean tumors (P =.028). p73 methylation was common among the Chilean cancers (40%) compared with those from the United States (13%; P =.034).
Conclusions: The acquisition of hypermethylation at multiple tumor-suppressor gene-promoter sites may contribute to tumor formation and progression within the chronically inflamed gallbladder. The apparent differences in methylation patterns among the Chilean and US gallbladder cases may indicate a unique biology associated with this cancer in different parts of the world.