STROMAL EXPRESSION OF PLATELET-DERIVED GROWTH-FACTOR BETA-RECEPTOR AND PLATELET-DERIVED GROWTH-FACTOR B-CHAIN IN COLORECTAL-CANCER

BACKGROUND: The importance of growth factors, such as platelet-derived growth factor (PDGF), for stromal activation in colorectal cancer is unclear. EXPERIMENTAL DESIGN: The expression of beta-receptors for PDG F, and PDGF B-chain (PDGF AB and PDGF BB) was investigated by immunohi stologic techniques in full-thickness biopsies from 210 colorectal can cers. These antigens were detected by the monoclonal antibodies PDGFR- B2 and PDGF 007, respectively. RESULTS: All tumors contained granular clusters of PDGF beta-receptor expressing stromal cells, whereas tumor epithelium was invariably negative. The staining was most prominent i n vascular cells. There were several cells in the tumor stroma that ex pressed PDGF AB/BB. Double immunofluorescence stainings in specimens f rom four patients performed in order to characterize PDGF beta-recepto r- and PDGF AB/BB expressing cells showed that cells expressing PDGF b eta-receptors did not express PDGF AB/BB. About 20% of cells in the st roma expressing PDGF AB/BB were macrophages (CD68-positive cells), whe reas the nature of the remaining stromal cells expressing PDGF AB/BB c ould not be disclosed. Furthermore, about 30% of CD68-positive macroph ages expressed PDGF AB/BB, but not PDGF beta-receptors. The extent of clusters of PDGF beta-receptor expressing cells varied considerably be tween tumors, and its prognostic value was considered in the entire tu mor material. The number of clusters did, however, not correlate to tu mor differentiation, tumor stage according to Dukes', or outcome. CONC LUSIONS: The presence of cells expressing PDGF beta-receptor and PDGF AB/BB respectively, i.e., expression of the receptor and its ligand, f ulfills two of the prerequisites for a role of PDGF in the activation of stromal cells in colorectal cancers. The data suggest that stromal activation, characterized by clusters of PDGF B-receptor expressing ce lls, is of importance for the formation of tumor stroma per se. Howeve r, the expression of the PDGF beta-receptor has no potential as a prog nostic marker.