High incidence of EMMPRIN expression in human tumors

Extracellular matrix metalloproteinase inducer expressed by tumor cells stimulates peritumoral fibroblasts to produce matrix metalloproteinases, thus contributing to tumor invasion and metastasis. To assess its suitability as potential therapeutic target, the overall incidence of EMMPRIN expression in normal and neoplastic tissues was analyzed. EMMPRIN expression was detected immunohistochemically using monoclonal antibodies MEM-M6/1 and HIM6 and tissue microarrays with 2,348 and 608 tissue samples from 129 distinct tumor types and 76 different normal tissues, respectively. Expression and glycosylation state of EMMPRIN in human breast cancer cells were analyzed by Western blot analysis with monoclonal antibodies recognizing distinct carbohydrate structures and biochemical methods. EMMPRIN expression was found in 112 of 129 tumor entities analyzed with malignant tumors being EMMPRIN positive more frequently than benign tumors. A remarkable heterogeneity in EMMPRIN expression between tumor entities was observed. Among others, squamous-cell carcinomas (60-100%), pancreatic (87%), chromophobic kidney (83%), hepatocellular (83%) or medullary breast (83%) adenocarcinomas as well as glioblastoma multiforme (79%) presented with a particular high incidence of EMMPRIN expression. There were a limited number of EMMPRIN-positive normal cell types including proliferatively active and differentiating epithelial cells, germ cells, myocardial cells in the left heart ventricle or vascular endothelial cells of the brain. We could further demonstrate that breast cancer cells expressed EMMPRIN isoforms differing in the presence or absence of Lewis X glycan structures. Our results may assist in defining the suitability of EMMPRIN as therapeutic target and predicting negative side effects.