Kinin receptors are expressed in human astrocytic tumour cells

Tissue kallikrein (TK) is known to be present in several tumours in which i ncreased KLK1 (TK) gene expression has been demonstrated. By degrading comp onents of the extracellular matrix, TK may facilitate tumour proliferation and invasion. The vasodilatory effect of the bioactive kinin peptides cause s an increase in vascular permeability, thereby enhancing metastasis. Since kinins act by receptor-linked signal transduction mechanisms, the aim of t his study was to elucidate the localization and expression of kinin B1 and B2 receptors in surgical samples of human astrocytic tumours. Tumour tissue collected was processed for light, confocal and electron microscopy (EM) a nd RNA extraction. The mean high intensity of immunolabeling in tumour cell s was quantified in pixels per square micrometer using the Analysis 2.1 Pro system (Soft-Imaging Software, Germany, 1996). The ultrastructural localiza tion of B1 and B2 kinin receptors was performed on ultrathin sections of th e resin-embedded tissue, using immunogold-labeled probes. In the human brai n, immunoreactive B2 occurs in cortical neurones but not in glial cells, an d immunolabeling for B1 receptors is absent in cortical areas. In the prese nt study, in all of the tumours studied so far, immunolabeling for B2 (28.4 2 pixels/mu m(2), n = 12) and B1 (14.07 pixels/mu m(2), n = 10) was observe d on the astrocytic cells. Immunoreactive kinin receptors were also present in endothelial cells of the stromal blood vessels. At EM, the average numb er of immunogold particles was 14 for B2 receptors and eight for B1 recepto rs. The immunoreactive B2 receptors were located closer to the periphery of the tumour cells while B1 immunolabeling was observed throughout the cell. (C) 1999 Elsevier Science B.V. All rights reserved.