Etude des plaques de Peyer de l'intestin du souriceau nouveau-né comme voie possible de pénétration du virus du cancer mammaire de la souris (MMTV)

Peer reviewe

Down-Regulation of Vascular Endothelial Growth Factor by Tissue Inhibitor of Metalloproteinase-2: Effect on in Vivo Mammary Tumor Growth and Angiogenesis

The tissue inhibitor of metalloproteinases-2 (TIMP-2) has at least two independent functions, i.e., regulation of matrix metalloproteinases and growth promoting activity. We investigated the effects of TIMP-2 overexpression, induced by retroviral mediated gene transfer, on the in vivo development of mammary tumors in syngeneic mice inoculated with EF43.fgf-4 cells. The EF43.fgf-4 cells established by stably infecting the normal mouse mammary EF43 cells with a retroviral expression vector for the fgf-4 oncogene, are highly tumorigenic and overproduce vascular endothelial growth factor (VEGF). Despite a promotion of the in vitro growth rate of EF43.fgf-4 cells overexpressing timp-2, the in vivo tumor growth was delayed. At day 17 post-cell injection, the volume of tumor derived from TIMP-2-overexpressing cells was reduced by 80% as compared with that obtained with control cells. Overexpression of TIMP-2 was associated with a down-regulation of VEGF expression in vitro and in vivo, a reduction of vessel size, density, and blood supply in the induced tumors. In addition, TIMP-2 completely inhibited the angiogenic activity of EF43.fgf-4 cell-conditioned medium in vitro using a rat aortic ring model. Our findings suggest that overexpression of TIMP-2 delays growth and angiogenesis of mammary carcinoma in vivo and that down-regulation of VEGF expression may play an important role in this TIMP-2-mediated antitumoral and antiangiogenic effects. Finally the in vivo delivery of TIMP-2, as assessed by i.v. injection of recombinant adenoviruses vectors, significantly reduced the growth of the EF43.fgf-4-induced tumors. This effect of TIMP-2 was shown to be equally comparable with that of angiostatin, a known potent inhibitor of angiogenesis

Progression in MCF-7 Breast Cancer Cell Tumorigenicity: Compared Effect of FGF-3 and FGF-4.

The transforming properties of fibroblast growth factor 3 (FGF-3) were investigated in MCF7 breast cancer cells and compared to those of FGF-4, a known oncogenic product. The short form of fgf-3 and the fgf-4 sequences were each introduced with retroviral vectors and the proteins were only detected in the cytoplasm of the infected cells, as expected. In vitro, cells producing FGF-3 (MCF7.fgf-3) and FGF-4 (MCF7.fgf-4) displayed an amount of estrogen receptors decreased to around 45% of the control value. However, MCF7.fgf-3 cell proliferation remained responsive to estradiol supply. The sensitivity of the MCF7.fgf-4 cells, if existant, was masked by the important mitogenic action exerted by FGF-4. In vivo, the MCF7.fgf-3 and MCF7.fgf-4 cells gave rise to tumors under conditions in which the control cells were not tumorigenic. Supplementing the mice with estrogen had the paradoxical effect of totally suppressing the start of the FGF-3 as well as the FGF-4 tumors. Tumorigenicity in the presence of matrigel was similar for MCF7.fgf-3 and control cells and was increased by estrogen supplementation. Once started, the MCF7.fgf-4 tumors grew with a characteristic high rate. Remarkably, FGF-4 but not FGF-3, stimulated the secretion of vascular endothelial growth factor (VEGF165) without altering the steady-state level of its mRNA, suggesting a possible regulation of VEGF synthesis at the translational level in MCF7 cells. The increased VEGF secretion is probably involved in the more aggressive phenotype of the MCF7.fgf-4 cells while a decreased dependence upon micro-environmental factors might be part of the increased tumorigenic potential of the MCF7.fgf-3 cells.Peer reviewe

Angiogenesis by Fibroblast Growth Factor 4 Is Mediated through an Autocrine Up-regulation of Vascular Endothelial Growth Factor Expression

The infection of normal mouse mammary EF43 cells by a retroviral vector carrying either Fgf-3 (EF43.Fgf-3) or Fgf-4 (EF43.Fgf-4) cDNA resulted in the transformation of cells displaying different tumorigenic potentials in nude mice (A. Hajitou and C-M. Calberg-Bacq, Int. J. Cancer, 63: 702-709, 1995). EF43.Fgf-4 produced rapidly developing tumors at all sites of inoculation, whereas EF43.Fgf-3 produced slowly growing tumors only in the mammary fat pad. Cells infected with the vector carrying the selection gene alone (EF43.C) were not tumorigenic. The angiogenic properties of these cells were tested in an in vitro angiogenesis model using human umbilical vein endothelial cells (HUVECs) cultured at the surface of a type I collagen gel and their capacity to form tube-like structures on invasion of the gel. Only the conditioned medium (CM) of EF43.Fgf-4 induced an angiogenic morphotype in HUVECs. In parallel, the mRNA expression of matrix metalloproteinase 1 and c-ETS-1 was increased in the HUVECs displaying a differentiated phenotype, whereas the tissue inhibitor of matrix metalloproteinase 1 mRNA level was decreased. Recombinant human fibroblast growth factor 4 (FGF-4) did not induce an angiogenic phenotype in HUVECs by itself. By Western blot analysis, a high expression of vascular endothelial growth factor (VEGF) was detected in the EF43.Fgf-4 CM. This result was confirmed by Northern blot analysis of total RNA extracted from the three cell types; the steady-state level of VEGF mRNA was low and equivalent in EF43.C and EF43.Fgf-3, whereas it was strongly increased in EF43.Fgf-4. Culturing EF43 cells carrying only the selection gene with increasing concentrations of recombinant human FGF-4 resulted in a dose-dependent stimulation of VEGF. The induction of the angiogenic morphotype and the parallel modulations of the biosynthetic phenotype in HUVECs were completely suppressed by adding a neutralizing antibody directed against VEGF to EF43.Fgf-4 CM. Furthermore, inhibition of protein kinase C by bisindoylmaleimide suppressed the angiogenic phenotype induced by the CM of EF43.Fgf-4. Our results point to an indirect angiogenic activity of FGF-4 through the autocrine induction of VEGF secretion by EF43.Fgf-4 cells, an original signaling pathway that might be significant in tumor progression and metastasis