Enhanced expression of vascular endothelial growth factor (VEGF) plays a critical role in the tumor progression potential induced by simian virus 40 large T antigen.
Vascular endothelial growth factor (VEGF), an important angiogenic factor, regulates cell proliferation, differentiation, and apoptosis through activation of its tyrosine-kinase receptors, such as Flt-1 and Flk-1/Kdr. Human malignant mesothelioma cells (HMC), which have wild-type p53, express VEGF and exhibit cell growth increased by VEGF. Here, we demonstrate that early transforming proteins of simian virus (SV) 40, large tumor antigen (Tag) and small tumor antigen (tag), which have been associated with mesotheliomas, enhanced HMC proliferation by inducing VEGF expression. SV40-Tag expression potently increased VEGF protein and mRNA levels in several HMC lines. This effect was suppressed by the protein synthesis inhibitor, cycloheximide. Inactivation of the VEGF signal transduction pathway by expression of soluble form of Flt-1 inhibited Flk-1/Kdr activation and HMC proliferation induced by SV40 early genes. Experiments with SV40 mutants revealed that SV40-Tag, but not -tag, is involved in the VEGF promoter activation. However, concomitant expression of SV40-tag enhanced Tag function. In addition, SV40-Tag expression sustained VEGF induction in colon carcinoma cell line (CCL)-233, which have wild-type p53, but not in CCL-238, which lack functional p53. These data indicate that VEGF regulation by SV40 transforming proteins can represent a key event in SV40 signaling relevant for tumor progression.
Catalano
Alfonso
A
Institute of Experimental Pathology, University of Ancona, Faculty of Medicine, Via Ranieri, 60131 Ancona, Italy.
Romano
Mario
M
Martinotti
Stefano
S
Procopio
Antonio
A
D043925:Angiogenesis Inducing Agents / Q000235:genetics* / Q000378:metabolism; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics*; D008654:Mesothelioma; D010766:Phosphorylation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D017978:Receptors, Growth Factor / Q000378:metabolism; D040262:Receptors, Vascular Endothelial Growth Factor; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1; D042442:Vascular Endothelial Growth Factors
D043925:Angiogenesis Inducing Agents; D000952:Antigens, Polyomavirus Transforming; D016228:Endothelial Growth Factors; D008222:Lymphokines; D011500:Protein Synthesis Inhibitors; D011518:Proto-Oncogene Proteins; D017978:Receptors, Growth Factor; D016159:Tumor Suppressor Protein p53; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D003513:Cycloheximide; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1