Hypoxia is responsible for soluble vascular endothelial growth factor receptor-1 (VEGFR-1) but not for soluble endoglin induction in villous trophoblast.

BACKGROUND: Pre-eclampsia is a pregnancy disorder characterized by a maternal endothelial cell dysfunction associated with low levels of circulating placental growth factor (PlGF) and increased levels of total vascular endothelial growth factor (VEGF), soluble VEGF receptor-1 (sVEGFR-1), and soluble endoglin, a transforming growth factor beta1 and 3 coreceptor. Here, we tested the hypothesis that these altered levels of angiogenic cytokines and of the anti-angiogenic soluble forms of cytokine receptors could be the consequence of hypoxia. METHODS: Normal human umbilical vein endothelial cells, immortalized first trimester extravillous trophoblast cells (HTR8/SVneo) and first trimester placental villi explants (8-14 weeks) were used for culture under normoxia (20% O(2)) or hypoxia (1% O(2)). Culture media were collected for the measurement of cytokines by enzyme-linked immunosorbent assay. Total RNA was extracted for RT-PCR analysis. RESULTS: Under hypoxia, villous trophoblast expressed higher levels of VEGF, VEGFR-1, sVEGFR-1 and VEGFR-2 mRNAs (P < 0.001), and secreted more VEGF and sVEGFR-1 proteins (P < 0.05). In contrast, PlGF mRNA and protein were decreased in 1% O(2) (P < 0.001), whereas endoglin (Eng) was not modulated. Additionally, sVEGFR-1 directly abolished VEGF/PlGF-induced angiogenesis in the rat aortic ring assay. CONCLUSIONS: Our results support the hypotheses that, in pre-eclampsia, (i) overproduction of VEGF family factors by pre-eclamptic placenta is a consequence of induced hypoxia; (ii) overproduction of sVEGFR-1 by hypoxic villous trophoblast accounts for maternal free VEGF depletion; (iii) low circulating level of free PlGF is not only related to sVEGFR-1 overproduction, but also to hypoxia-induced mRNA down-regulation; (iv) Eng is not modulated by hypoxia.

Catalytically inactive human cathepsin D triggers fibroblast invasive growth.

The aspartyl-protease cathepsin D (cath-D) is overexpressed and hypersecreted by epithelial breast cancer cells and stimulates their proliferation. As tumor epithelial-fibroblast cell interactions are important events in cancer progression, we investigated whether cath-D overexpression affects also fibroblast behavior. We demonstrate a requirement of cath-D for fibroblast invasive growth using a three-dimensional (3D) coculture assay with cancer cells secreting or not pro-cath-D. Ectopic expression of cath-D in cath-D-deficient fibroblasts stimulates 3D outgrowth that is associated with a significant increase in fibroblast proliferation, survival, motility, and invasive capacity, accompanied by activation of the ras-MAPK pathway. Interestingly, all these stimulatory effects on fibroblasts are independent of cath-D proteolytic activity. Finally, we show that pro-cath-D secreted by cancer cells is captured by fibroblasts and partially mimics effects of transfected cath-D. We conclude that cath-D is crucial for fibroblast invasive outgrowth and could act as a key paracrine communicator between cancer and stromal cells, independently of its catalytic activity.

Multifunctional role of matrix metalloproteinases in multiple myeloma: a study in the 5T2MM mouse model.

Matrix metalloproteinases (MMPs) are known to play a role in cell growth, invasion, angiogenesis, metastasis, and bone degradation, all important events in the pathogenesis of cancer. Multiple myeloma is a B-cell cancer characterized by the proliferation of malignant plasma cells in the bone marrow, increased angiogenesis, and the development of osteolytic bone disease. The role of MMPs in the development of multiple myeloma is poorly understood. Using SC-964, a potent inhibitor of several MMPs (MMP-2, -3, -8, -9, and -13), we investigated the role of MMPs in the 5T2MM murine model. Reverse transcriptase-polymerase chain reaction demonstrated the presence of mRNA for MMP-2, -8, -9, and -13 in 5T2MM-diseased bone marrow. Mice bearing 5T2MM cells were given access to food containing SC-964. The concentration of SC-964 measured in the plasma of mice after 11 days of treatment was able to inhibit MMP-9 activity in gelatin zymography. Treatment of 5T2MM-bearing mice resulted in a significant reduction in tumor burden, a significant decrease in angiogenesis, and partially protective effect against the development of osteolytic bone disease. The direct role of MMPs in these different processes was confirmed by in vitro experiments. All these results support the multifunctional role of MMPs in the development of multiple myeloma.

Histone deacetylases inhibitors as anti-angiogenic agents altering vascular endothelial growth factor signaling.

Angiogenesis is a complex biological process involving the coordinated modulation of many genes. Histone deacetylases (HDAC) are a growing family of enzymes that mediate the availability of chromatin to the transcriptional machinery. Trichostatin-A (TSA) and suberoylanilide hydroxamic acid (SAHA), two HDAC inhibitors known to relieve gene silencing, were evaluated as potential antiangiogenic agents. TSA and SAHA were shown to prevent vascular endothelial growth factor (VEGF)-stimulated human umbilical cord endothelial cells (HUVEC) from invading a type I collagen gel and forming capillary-like structures. SAHA and TSA inhibited the VEGF-induced formation of a CD31-positive capillary-like network in embryoid bodies and inhibited the VEGF-induced angiogenesis in the CAM assay. TSA also prevented, in a dose-response relationship, the sprouting of capillaries from rat aortic rings. TSA inhibited in a dose-dependent and reversible fashion the VEGF-induced expression of VEGF receptors, VEGFR1, VEGFR2, and neuropilin-1. TSA and SAHA upregulated the expression by HUVEC of semaphorin III, a recently described VEGF competitor, at both mRNA and protein levels. This effect was specific to endothelial cells and was not observed in human fibroblasts neither in vascular smooth muscle cells. These observations provide a conspicuous demonstration that HDAC inhibitors are potent anti-angiogenic factors altering VEGF signaling.