Immunohistochemical analysis of hepatocyte growth factor and c-Met in plasma cell disease

Interaction with the bone marrow microenvironment is important for homing and survival of myeloma cells. One cytokine involved in this process is hepatocyte growth factor (HGF). HGF, by binding to the receptor tyrosine kinase c-Met, mediates a broad range of tumour progression activities. Our aims were to investigate whether HGF and c-Met are present in bone marrow and extramedullary tumours from patients with monoclonal plasma cell disease, and whether c-Met is activated.

Expression of HGF, c-Met and phospho-c-Met was studied by immunohistochemistry in biopsies from 80 patients with monoclonal plasma cell disease. Cytoplasmic staining for HGF in plasma cells was demonstrated in 58 of 68 biopsies from multiple myeloma patients (85%), but also in biopsies from nine of 10 healthy individuals. Membranous staining for c-Met was found in 25 of 63 multiple myeloma patients (40%) and in none of 10 healthy individuals. Membranous staining for phospho-c-Met was found in biopsies from 15 of 21 c-Met-positive myeloma patients (71%).

Our data point to c-Met expression as one of the factors that distinguishes normal from malignant plasma cells, and indicate that the HGF/c-Met system is activated in multiple myeloma patients.