Role of E-cadherin gene in gall bladder cancer and its precursor lesions

The aim was to investigate the genomic instability in the E-cadherin (CDH1) gene and to correlate it with its protein expression in gall bladder cancer (GBC) and in other gall bladder (GB) diseases viz. chronic cholecystitis (CC), xantho-granulomatous cholecystitis (XGC), and normal GB to explicate its role in GBC tumorigenesis. Microsatellite instability (MSI) and loss of heterozygosity (LOH) in CDH1 were studied using D16S421, D16S496, D16S503, D16S512, D16S2624, and D16S3021 microsatellite markers and D2S123 (2p16), D2S382 (2q24), D6S292 (6q21-23), D7S480 (7q31), and D17S796 (17p13.1-3) were used to investigate genomic instability at 2p, 2q, 6q, 7q, and 17p loci in 40 GBC, 50 CC, 34 XGC, and 15 normal GB cases. Immunohistochemistry was carried out to analyze the E-cadherin and p53 protein expression. Overall LOH in CDH1 and other markers was high in GBC and XGC as compared to CC; however, it did not correlate with its protein expression in GBC cases. Loss of E-cadherin expression was high in GBC (67%), while majority of the CC (94%) and XGC (91%) cases retained positive E-cadherin expression. Overexpression of p53 was high in GBC (43%) whereas CC, XGC, normal GB cases were negative for p53 overexpression. None of the normal GB cases showed genomic instability at any of the markers. High LOH in CDH1 and other chromosomal loci in GBC indicated that the genomic instability followed a GBC>XGC>CC trend during the process of neoplastic transformation in GB, highlighting the fact that CC might act as a precursor lesion of GBC.