PubMed · 2865791
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T Banciu. [Current developments in hepatology].. https://pubmed.ncbi.nlm.nih.gov/2865791/
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Vascular endothelial growth factor-D (VEGF-D) stimulates growth of vascular and lymphatic endothelial cells by signaling through the tyrosine kinase receptors KDR (VEGFR-2) and Flt-4 (VEGFR-3). In the present study, we examined the effects of VEGF-D on apoptosis in human MCF-7 and MDA-MB-231 breast carcinoma cells. Because VEGF-D was not expressed constitutively in vitro, stable VEGF-D transfectants were produced. The VEGF-D-expressing MCF-7 and MDA-MB-231 lines displayed resistance to apoptosis induced by hypoxia, staurosporin and cycloheximide. Increased Bcl-2 expression, decreased homogenous caspase activities and inhibition of poly(ADP-ribose) polymerase cleavage were associated with inhibition of apoptosis in VEGF-D-expressing clones. Also, caspase-3 activation was suppressed in the VEGF-D expressing MDA-MB-231 clone. The antiapoptotic effect of VEGF-D in vitro was recapitulated in vivo using VEGF-D-expressing MDA-MB-231 xenografts. The lack of VEGFR-2 protein expression by Western blot and ineffectiveness of a neutralizing VEGFR-2 antibody in eliminating the antiapoptotic effects of VEGF-D suggest a different and yet unknown signaling mechanism. Our findings indicate that VEGF-D has a novel function as a survival factor of breast carcinoma cells in addition to its established functions as an angiogenic and lymphangiogenic factor.
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Plasma cells (PC) are B-lymphocytes terminally differentiated in a postmitotic state, with the unique purpose of manufacturing and exporting Igs. Despite the importance of this process in the survival of vertebrates, no studies have been made to understand the molecular events that regulate Ig exocytosis by PC. The present study explores the possible presence of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) system in human PC, and examines its functional role in Ig secretion. Syntaxin-2, Syntaxin-3, Syntaxin-4, vesicle-associated membrane protein (VAMP)-2, VAMP-3, and synaptosome-associated protein (SNAP)-23 could be readily detected in normal human PC obtained from intestinal lamina propria and blood, as well as in human PC lines. Because SNAP-23 plays a central role in SNAREs complex formation, it was chosen to examine possible functional implications of the SNARE system in PC Ig secretion. When recombinant SNAP-23 fusion protein was introduced into the cells, a complete abolishment of Ig production was observed in the culture supernatants of PC lines, as well as in those of normal PC. These results provide insights, for the first time, into the molecular machinery of constitutive vesicular trafficking in human PC Ig secretion and present evidence indicating that at least SNAP-23 is essential for Ab production.