BASEMENT MEMBRANE PROTEINS-LAMININ AND FIBRONECTIN IN GENITO-URINARY TUMORS

Abstract

The localization patterns of fibronectin and laminin were studied in genito-urinary tumors and corresponding normal tissues by indirect immunofluorescent technique. In total, three testes, ten kidneys, ten bladders, four testicular tumors, six renal adenocarcinomas and fourteen bladder carcinomas were tested.
Fibronectin, a major component of non-collagenous glycoproteins in extracellular matrix, was detected on basement membrane and extracellular matrix of stromal tissues but not on epithelial cells both in malignant tumors and normal tissues. Therefore, the localization of fibronectin could be a useful histological marker for stromal reaction of epithelial tumor or differential diagnosis for epithelial malignancies from non-epithelial tumors, since fibroenctin was known to be positive in cytoplasm of non-epithelial tumor cells.
Laminin, a non-collagenous glycoprotein in basement membranes, was detected on only epithelial and vascular basement membranes in normal tissues. In genito-urinary tumors, however, the localization of laminin was different from tumor to tumor. Testicular yolk sac tumor seemed to be a laminin synthetic tumor because of a pattern of laminin localization which was found in extracellular matrix and cytoplasm of this tumor cells. In bladder transitional cell carcinoma, laminin was solely detected on basement membranes underneath lining epithelial tumor cells and endothelial cells of vessels, but not in cytoplasm and extracellular matrix. The basement membranes were definitely stained by histochemical staining for laminin, segregating tumor cells from stromal tissue in all tested bladder transitional cell carcinomas including four invasive bladder tumors obtained by cystectomy. As laminin was known as a protein localizing in lamina lucida of basement membranes, it was suggested that bladder tumors might invade deeply with coverage of a layer of lamina lucida, a component of basement membranes. Intermediate laminin synthesis was found in renal adencarcinomas, in which laminin was detected on pericellular matrix but not on cytoplasm of tumor cell. Taken together, different localization of laminin in genitourinary tumors possibly depends on laminin synthetic ability by tumor cells. Histochemical detection for laminin may be quite useful for the study on histological property of basement membrane or basement membrane material elaborated by tumor cells.