EXPRESSION OF C-ERBB(2) ONCOGENE PRODUCT IN DIFFERENT TUMORS AND ITS STANDARDIZED EVALUATION

In order to evaluate the reliability and reproducibility of the immuno histochemical demonstration of the c-erbB(2) oncoprotein and define cr iteria for positivity assessment in paraffin-embedded material from di fferent tumours, we examined immunohistochemically 79 gastric, 100 col orectal and 20 bladder carcinomas using 5 different c-erbB(2) antibodi es. To determine criteria for the evaluation of c-erbB(2) positivity, the observed immunohistochemical staining was compared with the actual protein prevalence, determined by Western blot analysis of each tumou r, The comparison of protein levels obtained from Western blot with co rresponding immunohistochemistry revealed that positive staining can o nly be considered to be specific for c-erbB(2) oncoprotein if: (i) the re is a definite staining along the tumour cell membrane with no predo minant immunoreactivity inside the tumour cell cytoplasm, (ii) the int ensity of immunoreactivity is comparable with a positive standard (e.g , in this study breast carcinoma) and (iii) the surrounding normal, no n-neoplastic tissue shows no immunoreactivity. The graduation of stain ing intensities did not correlate to the actual amount of protein dete cted in Western blots, This study stresses the importance of defined a nd controlled criteria for evaluation of c-erbB(2) oncoprotein positiv ity in immunohistochemistry.