Céline Sabatel

MicroRNA-21 Exhibits Antiangiogenic Function by Targeting RhoB Expression in Endothelial Cells

Background MicroRNAs (miRNAs) are endogenously expressed small non-coding RNAs that regulate gene expression at post-transcriptional level. The recent discovery of the involvement of these RNAs in the control of angiogenesis renders them very attractive in the development of new approaches for restoring the angiogenic balance. Whereas miRNA-21 has been demonstrated to be highly expressed in endothelial cells, the potential function of this miRNA in angiogenesis has never been investigated. Methodology/Principal Findings We first observed in endothelial cells a negative regulation of miR-21 expression by serum and bFGF, two pro-angiogenic factors. Then using in vitro angiogenic assays, we observed that miR-21 acts as a negative modulator of angiogenesis. miR-21 overexpression reduced endothelial cell proliferation, migration and the ability of these cells to form tubes whereas miR-21 inhibition using a LNA-anti-miR led to opposite effects. Expression of miR-21 in endothelial cells also led to a reduction in the organization of actin into stress fibers, which may explain the decrease in cell migration. Further mechanistic studies showed that miR-21 targets RhoB, as revealed by a decrease in RhoB expression and activity in miR-21 overexpressing cells. RhoB silencing impairs endothelial cell migration and tubulogenesis, thus providing a possible mechanism for miR-21 to inhibit angiogenesis. Finally, the therapeutic potential of miR-21 as an angiogenesis inhibitor was demonstrated in vivo in a mouse model of choroidal neovascularization. Conclusions/Significance Our results identify miR-21 as a new angiogenesis inhibitor and suggest that inhibition of cell migration and tubulogenesis is mediated through repression of RhoB.

Sprouty1, a new target of the angiostatic agent 16K prolactin, negatively regulates angiogenesis

BackgroundDisorganized angiogenesis is associated with several pathologies, including cancer. The identification of new genes that control tumor neovascularization can provide novel insights for future anti-cancer therapies. Sprouty1 (SPRY1), an inhibitor of the MAPK pathway, might be one of these new genes. We identified SPRY1 by comparing the transcriptomes of untreated endothelial cells with those of endothelial cells treated by the angiostatic agent 16 K prolactin (16 K hPRL). In the present study, we aimed to explore the potential function of SPRY1 in angiogenesis.ResultsWe confirmed 16 K hPRL induced up-regulation of SPRY1 in primary endothelial cells. In addition, we demonstrated the positive SPRY1 regulation in a chimeric mouse model of human colon carcinoma in which 16 K hPRL treatment was shown to delay tumor growth. Expression profiling by qRT-PCR with species-specific primers revealed that induction of SPRY1 expression by 16 K hPRL occurs only in the (murine) endothelial compartment and not in the (human) tumor compartment. The regulation of SPRY1 expression was NF-κB dependent. Partial SPRY1 knockdown by RNA interference protected endothelial cells from apoptosis as well as increased endothelial cell proliferation, migration, capillary network formation, and adhesion to extracellular matrix proteins. SPRY1 knockdown was also shown to affect the expression of cyclinD1 and p21 both involved in cell-cycle regulation. These findings are discussed in relation to the role of SPRY1 as an inhibitor of ERK/MAPK signaling and to a possible explanation of its effect on cell proliferation.ConclusionsTaken together, these results suggest that SPRY1 is an endogenous angiogenesis inhibitor.

Antiangiogenic liposomal gene therapy with 16K human prolactin efficiently reduces tumor growth

Human 16K PRL (16K hPRL) is a potent inhibitor of angiogenesis both in vitro and in vivo. It has been shown to prevent tumor growth in three xenograft mouse models. Here we have used a gene transfer method based on cationic liposomes to produce 16K hPRL and demonstrate that 16K hPRL inhibits tumor growth in a subcutaneous B16F10 mouse melanoma model. Computer-assisted image analysis shows that 16K hPRL treatment results in the reduction of tumor vessel length and width, leading to a 57% reduction in average vessel size. We thus show, for the first time, that administration of the 16K hPRL gene complexed to cationic liposomes is effective to maintain antiangiogenic activities of 16K hPRL level.