HAb18G/CD147 Enhances The Secretion Of MMP Via CGMP/NO-sensitive Capacitative Calcium Entry (CCE) And Accordingly Attenuates Adhesion Ability Of Fibroblasts

HAb18G is a hepatoma-associated antigen cloned by hepatoma monoclonal antibody HAb18 screening from human hepatocellular carcinoma cDNA library. HAb18G is abundantly expressed in human hepatoma HHCC cell which has a highly metastasis poteintial. HAbl8G is a highly glycosylated transmembrane protein of 60 kDa with an ectodomain consisting of two regions exhibiting the characteristics of the immunoglobulin superfamily . The amino acid sequence of HAb18G is identical to that of CD 147. A role for CD 147 as an adhesion molecule has been proposed, which involving in cell-cell and cell-extracellular matrix(ECM) interactions and tumor metastatic processes, and it has been reported to bind to a variety of cell types including endothelial cells and fibroblasts .Our previous studies have demonstrated that HAb18G-expressing hepatoma 7721 cell could stimulate co-cultural fibroblast cells to produce elevated levels of several matrix metalloproteinases (MMP), includingMMP-1, MMP-2, andMMP-9, which are well known for prompting invasion of hepatoma cells. Lim et al. found that CD 147 up-regulated MMP-1 mRNA expression, which was dependent on tyrosine kinase activity. However, substrates or ligands for CD 147 or enzymes that modify CD 147 remain unknown, and it is still obscure whether CD147 (or HAb18G, basigin, EMMPRIN, M6, etc.) is directly involved in the MMP secretion mechanism or the cell adhesion process.Members of MMP enzyme family have been broadly implicated in both physiological and pathophysiological tissue remodeling, and especially play key roles in tumor invasion and the metastasis process. Degradation of extracellular matrix (ECM) components by MMP is critical for tumor cell invasion and metastasis.Studies have proved that stramol cells mainly release MMP around tumor cells, and that calcium is an intracellular second messenger which mediates a wide range of cellular responses. NO is also known to inhibit Ca2+ entry through L-type Ca2+ channels (LTCC) in SMCs via cGMP-dependent mechanisms or via membrane hyperpolarization due to cGMP-dependent activation of Ca2+- dependent K+ channels.Although many reports have described the regulating mechanisms on the calcium icons channels, they all focused on the end result- increasing in [Ca2+]. Thus further investigation is certainly required to clarify the role of NO/cGMP in CCE and in MMP secretion.The aim of the present study is to demonstrate the existence of NO/cGMP-regulated CCE in stramol cell fibroblast NIH/3T3, to further explore the involvement of hepatoma-associated antigen HAb18G/CD147 in secretion of MMP via CCE and adhesion potential by stably transfecting HAb18G into NIH/3T3 cell.HAb18G/CD147 cDNA was transfected into fibroblast 3T3 cells to obtain a cell line stably expressing HAbl8G/CD147, t3T3, as demonstrated by immunofluorescence staining and flow cytometry assays. 8-Bromo-cGMP...