Down-regulation of Vascular Endothelial Growth Factor in a Human Colon Carcinoma Cell Line Transfected with an Antisense Expression Vector Specific for c-src

Abstract

Vascular endothelial growth factor (VEGF) is implicated in the angiogenesis of human colon cancer. Recent evidence suggests that factors that regulate VEGF expression may partially depend on c-src-mediated signal transduction pathways. The tyrosine kinase activity of Src is activated in most colon tumors and cell lines. We established stable subclones of the human colon adenocarcinoma cell line HT29 in which Src expression and activity are decreased specifically as a result of a transfected antisense expression vector. This study determined whether VEGF expression is decreased in these cell lines and whether the smaller size and reduced growth rate of antisense vector-transfected cell lines in vivo might result, in part, from reduced vascularization of tumors. Northern blot analysis of these cell lines revealed that VEGF mRNA expression was decreased in proportion to the decrease in Src kinase activity. Under hypoxic conditions, cells with decreased Src activity had a <2-fold increase in VEGF expression, whereas parental cells had a >50-fold increase. VEGF protein in the supernatants of cells was also reduced in antisense transfectants compared with that from parental cells. In nude mice, subcutaneous tumors from antisense transfectants showed a significant reduction in vascularity. These results suggest that Src activity regulates the expression of VEGF in colon tumor cells.

Tissue-specific gene therapy directed to tumor angiogenesis

“…Anti-CD31 (rat anti-mouse CD31 monoclonal Ab, Pharmingen, NJ, USA) were used for analyses of neovascularization in the tumor models according to the procedures previously described. 42 Statistical analysis Data are shown as mean ± s.e. Analysis between groups for statistically significant differences was performed with the use of t-test ANOVA, or the Mann-Whitney rank test.…”

Combined EGFR and c-Src Antisense Oligodeoxynucleotides Encapsulated with PAMAM Denderimers Inhibit HT-29 Colon Cancer Cell Proliferation

“…c-Src is arguably the oldest known oncogene and most important proto-oncogen in the development and progression of colon cancer. It is often over-expressed and activated in the number of human cancers such as colon, prostate, brain, lung, breast, ovarian, liver and pancreas carcinoma (Talamonti et al, 1993;Summy, 2005;Finn, 2008;Lieu and Kopetz, 2010).Src proto oncogen, has a key role in cellular pathways, such as migration, survival, motility, adhesion, angiogenesis, invasion, immune function and regulation of proliferation (Ellis, 1998;Summy and Gallick, 2003) Furthermore, c-Src has high kinase activity and protein level in the progression stage of colorectal cancer to hepatic metastases (Talamonti et al, 1993). Multiple signaling pathways are correlated with c-Src family kinases activity and human cancers (Mukhopadhyay, 1995;Yamaguchi, 1997).…”

Oncogenes and tumor angiogenesis: the HPV-16 E6 oncoprotein activates the vascular endothelial growth factor (VEGF) gene promoter in a p53 independent manner

“…This relationship may be necessary, but not su cient, for the angiogenic and tumorigenic phenotype Chin et al, 1999). Other oncogenes which appear to have a similar e ect on VEGF expression include receptor tyrosine kinases such as the ErbB family including the EGF receptor and ErbB2/Her2 (Viloria-Petit et al, 1997), non-receptor kinases such as src (Mukhopadhyay et al, 1995a;Rak et al, 1995a,b;Ellis et al, 1998) and transcription factor encoding proto-oncogenes such as myc, c-fos, and c-jun (Saez et al, 1995;Kraemer et al, 1999;Pelengaris et al, 1999). In this regard one important type of oncogene, which has not yet been examined well for its impact on VEGF expression, and hence tumor angiogenesis, are those encoded by the human papilloma virus (HPV).…”