Expression of HER2 and bradykinin B₁ receptors in precursor lesions of gallbladder carcinoma.

Aim: To determine the expression of HER2 and bradykinin B(1) receptors (B(1)R) in the two pathogenic models of gallbladder cancer: the metaplasia-dysplasia-carcinoma and the adenoma-carcinoma pathways.

Methods: Receptor proteins were visualized by immunohistochemistry on 5-μm sections of paraffin-embedded tissue. Expression of both receptors was studied in biopsy samples from 92 patients (6 males and 86 females; age ranging from 28 to 86 years, mean 56 years). High HER2 expression in specimens was additionally investigated by fluorescence in situ hybridization. Cell proliferation in each sample was assessed by using the Ki-67 proliferation marker.

Results: HER2 receptor protein was absent in adenomas and in normal gallbladder epithelium. On the contrary, there was intense staining for HER2 on the basolateral membrane of epithelial cells of intestinal metaplasia (22/24; 91.7%) and carcinoma in situ (9/10; 90%), the lesions that displayed a significantly high proliferation index. Protein up-regulation of HER2 in the epithelium with metaplasia or carcinoma in situ was not accompanied by HER2 gene amplification. A similar result was observed in invasive carcinomas (0/12). The B(1)R distribution pattern mirrored that of HER2 except that B(1)R was additionally observed in the adenomas. The B(1)R appeared either as cytoplasmic dots or labeling on the apical cell membrane of the cells composing the epithelia with intestinal metaplasia (24/24; 100%) and carcinoma in situ (10/10; 100%) and in the epithelial cells of adenomas. In contrast, both HER2 (4/12; 33%) and B(1)R (1/12; 8.3%) showed a low expression in invasive gallbladder carcinomas.

Conclusion: The up-regulation of HER2 and B(1)R in precursor lesions of gallbladder carcinoma suggests cross-talk between these two receptors that may be of importance in the modulation of cell proliferation in gallbladder carcinogenesis.