DETECTION OF C-ERBB-2 MESSENGER-RNAS USING DIG-LABELED OLIGONUCLEOTIDE PROBE WITH IN-SITU HYBRIDIZATION IN HUMAN BREAST-CARCINOMA - COMPARISON WITH IMMUNOHISTOCHEMICAL RESULTS

Amplification and overexpression of the c-erbB-2 oncogene are of progn ostic significance in human breast cancer. Overexpression of c-erbB-2 is the result of gene amplification. However, increased transcript lev els of c-erbB-2 are also detected in the absence of gene amplification . In this study for the detection of the overexpression mRNA in situ h ybridisation (ISH) and immunohistochemistry (IHC) were used. Our aim w as to develop the suitable mRNA ISH protocol for formalin-fixed paraff in-embedded material and to compare the localisation of transcripts an d protein products in 20 primary breast carcinomas. Sections were immu nostained with monoclonal c-erbB-2 antibody. In ISH method digoxigenin -labelled oligoprobe was used for the detection of c-erbB-2 mRNAs. We determined optimal condition for the ISH procedure (e.g., probe concen tration, digestion, post washing). c-erbB-2 protein overproduction was detected in 11/20 cases with HC. The mRNA signals were observed in ma lignant cell cytoplasm in 6/20 cases by ISH. ISH positive signals were found in only one case without detected overexpression of the protein . There were cell to cell variations in the hybridisation signals even within individual tumours. The ISH and IHC positive signals for c-erb B-2 was observed mostly in infiltrating ductal carcinomas that belong to aggressive lesions.