IMMUNOHISTOCHEMICAL EXAMINATION OF C-MET PROTEIN EXPRESSION IN ASTROCYTIC TUMORS

Hepatocyte growth factor/scatter factor (HGF/SF), which has various ph ysiological functions, and its receptor c-Met, the human c-met proto-o ncogene product, are thought to be determinant in the pathological pro cesses of various malignancies. To investigate the possible role of HG F/SF in the progression of development of astrocytic tumors, we examin ed the expression of c-Met in these tumors. Immunohistochemistry using the streptavidin-biotin peroxidase complex method and immunofluoresce nce double staining with anti-c-Met polyclonal and anti-glial fibrilla ry acidic protein monoclonal antibodies were performed. Positive c-Met expression was detected in 31 of the 42 astrocytic tumors and some of the control cases analyzed. c-Met-positive cells showed morphological characteristics of astrocytes. Especially in the cases of high-grade tumors, c-Met positivity was abundant in cells in both vascular-rich a nd peripheral regions of the tumors but not in the cells with distinct ly malignant features. Immunofluorescence double staining revealed tha t the c-Met-positive cells were in part of astrocytic origin. We sugge st that c-Met-positive cells are affected by some factors in the lesio ns where the pathological processes are in a state of development. Our studies indicated that c-Met expression might take part in glioma inv asion but not in the development of malignancy.