Quantitation of c-erbB-2 mRNA by competitive reverse transcriptase-polymerase chain reaction

The overexpression of the c-erbB-2 gene has been reported as an independent prognostic factor for the progressions of primary human adenocarcinomas such as breast cancer, although there are some controversies and overexpression rate are variable (10 similar to 50%). Both the controversies on the prognostic value and the varible overexpression rate may result from interpersonal variations in the immunohistochemical quantitation of the c-erbB-2 gene product or the heterogeneity of the etiology of breast cancers. To clarify this point, we designed an accurate quantitation method of c-erbB-2 mRNA with minimal interpersonal variations. We set up the competitive reverse transcriptase-polymerase chain reaction method for high sensitivity because the clinical samples are small biopsy specimens in many cases. With our method, the overall sensitivity was 50 times or more greater than that of the ribonuclease protection assay. We expect that our method is helpful in establishing the clinical meaning of c-erbB-2 overexpression in primary human adenocarcinomas, including breast cancers, and also enables-the levels of c-erbB-2 mRNA in small surgical samples such as biopsy specimens and lymph nodes to be assessed without interpersonal variation.