Evaluation of c-erbB-2 overexpression and Her-2/neu gene copy number heterogeneity in Barrett's adenocarcinoma

Amplifiction of the Her-2/neu gene is accompanied by overexpression of its cell surface receptor product, c-erbB-2 protein. To investigate the degree of intratumoural heterogeneity we applied immunohistochemistry in primary B arrett's adenocarcinoma (BCA) (n = 6) and dysplasia adjacent to the carcino ma (n = 4). In addition, fluorescence in situ hybridisation (FISH) was perf ormed in primary BCA (n=5) and dysplastic areas (n=4). For an objective eva luation digital image analysis and laser scanning microscopy were used. Fiv e of six BCA showed a marked intratumoural heterogeneous staining pattern r anging from areas in which the tumour cells were negative or faintly positi ve to tumour areas with a strong staining of the entire membrane. Among the two dysplastic areas also a heterogenous staining pattern was observed. FI SH analysis revealed marked heterogeneity of intratumoural gene copy number changes in all BCA showing populations with different fractions of cells w ith polysomy, low level amplification and high level amplification. One dys plasia showed a minor population with Her-2/neu signal clusters. In conclus ion, we observed marked intratumoural heterogeneity of c-erbB-2 protein ove rexpression and Her-2/neu gene copy number in the majority of the primary B CA analyzed. Digital image analysis and laser scanning microscopy were help ful in quantifying the variations in protein expression and DNA copy number in individual tumour cells. The observed heterogeneity could hamper the ex act diagnostic determination of the c-erbB-2 status in small biopsies and p ossibly influence the effectiveness of a potential c-erbB-2 targeting thera py. Figures on http://www.esacp.org/acp/2000/20-1/walch.htm.