EXPRESSION OF PLATELET-DERIVED GROWTH-FACTOR B-CHAIN AND THE PLATELET-DERIVED GROWTH-FACTOR RECEPTOR-BETA SUBUNIT IN HUMAN BREAST-TISSUE AND BREAST-CARCINOMA

Breast carcinomas are known to express platelet-derived growth factor (PDGF), a known connective tissue mitogen. In order to further evaluat e the potential role of PDGF in these epithelial tumors, expression of the PDGF B chain (PDGF-B) and the PDGF receptor beta subunit (PDGFR) was analyzed by immunocytochemistry and in situ hybridization in 49 be nign and malignant breast tissues. PDGF-B expression was analyzed with respect to the expression of the proliferating cell nuclear antigen, as well as tumor grade, p53 overexpression, estrogen receptor, progest erone receptor, and c-erbB-2 expression. Expression of PDGF-B protein and mRNA was restricted to the breast epithelium and tumor cells excep t for scattered tissue macrophages. A. strong correlation was found be tween increasing proliferating cell nuclear antigen indices and PDGF-B expression in both nonmalignant (P = 0.01) and malignant (P = 0.02) b reast specimens. Decreased PDGF-B expression was found in postmenopaus al atrophic breast tissue compared with normal breast tissue (P = 0.04 ). Within the subgroup of malignant tumors, no correlations were found between PDGF-B expression and tumor grade or p53 overexpression. In 1 6 of the malignant tumors evaluated for estrogen/progesterone receptor status and c-erbB-2 overexpression, no correlations with PDGF-B expre ssion were found. Membranous PDGFR immunostaining was present within t he fibroblastic cell population in all of the tissues examined but not in the nonmalignant breast epithelium. Six malignant specimens had de tectable cytoplasmic expression of PDGFR. There was no correlation bet ween this PDGPR expression and proliferating cell nuclear antigen indi ces, but a correlation was noted between increasing estrogen receptor expression and PDGFR cytoplasmic expression (P = 0.04). The results su pport a paracrine role for PDGF-B in malignant and benign breast epith elial cell proliferation.