IMMUNOHISTOCHEMICAL EXPRESSION OF THE C-KIT PROTOONCOGENE PRODUCT IN HUMAN-MALIGNANT AND NONMALIGNANT BREAST TISSUES

The immunohistochemical expression of c-kit proto-oncogene product in 57 breast cancer tissues was studied using anti-c-kit proto-oncogene p roduct antibody in comparison with 20 normal breast tissues and 58 ben ign breast tumours. In normal breast tissues, the c-kit proto-oncogene product was strongly expressed on cell membrane and/or cytoplasm of a lveolar and ductal cells. The immunoreactive score (IRS) of c-kit prot ooncogene product in normal mammary epithelia was 6.22+/-2.11 (mean+/- s.d.). In benign breast diseases, the c-kit proto-oncogene product was detected heterogeneously with a reduced IRS (3.33+/-2.44). In breast cancer tissues, the expression of the immunoreactive c-kit proto-oncog ene product was often deleted and the average IRS was significantly re duced compared to those of normal breast tissues or benign breast dise ase tissues. Among benign diseases, the average IRS of intraductal pap illoma was significantly reduced (1.34+/-1.70) and the staining intens ity and pattern were found to be similar to those seen in breast cance r. The results in this study suggested that the c-kit proto-oncogene p roduct is correlated with the growth control or the differentiation of normal breast epithelium. Also, the loss of the expression of this pr otein may indicate the change of the signal transduction in relation t o malignant transformation in human mammary epithelium.