Angiogenesis

About: Angiogenesis is a research topic. Over the lifetime, 58248 publications have been published within this topic receiving 3290129 citations. The topic is also known as: blood vessel formation from pre-existing blood vessels & GO:0001525.

Protracted low-dose effects on human endothelial cell proliferation and survival in vitro reveal a selective antiangiogenic window for various chemotherapeutic drugs.

Abstract: Recent preclinical studies have shown that frequent administration in vivo of low doses of chemotherapeutic drugs (“metronomic” dosing) can affect tumor endothelium and inhibit tumor angiogenesis, reducing significant side effects (e.g., myelosuppression) involving other tissues, even after chronic treatment. This suggests that activated endothelial cells may be more sensitive, or even selectively sensitive, to protracted (“high-time”) low-dose chemotherapy compared with other types of normal cells, thus creating a potential therapeutic window. To examine this hypothesis, we assessed the effects of several different chemotherapeutic drugs—namely paclitaxel, 4-hydroperoxycyclophosphamide, BMS-275183 (an oral taxane), doxorubicin, epothilone B (EpoB) and its analogue 5-methylpyridine EpoB—on human microvascular or macrovascular endothelial cells, fibroblasts, and drug-sensitive or multidrug-resistant breast cancer cell lines in cell culture, using both short-term (24 h) versus long-term (144 h), continuous exposures, where drug-containing medium was replaced every 24 h. Whereas little differential and only weak effects were observed using the short-term exposure, a striking trend of comparative vascular endothelial cell hypersensitivity was induced using the continuous long-term exposure protocol. Potent differential growth inhibition effects as well as induction of apoptosis were observed with IC50 values in the range of 25–143 pm for paclitaxel, BMS-275183, EpoB, and 5-methylpyridine-EpoB. In contrast, the IC50 values for tumor cells and fibroblasts tested were in the range of 500 pm to >1 nm for these drugs. Similar differential IC50 values were noted using 4-hydroperoxycyclophosphamide. The results are consistent with the possibility that continuous low-dose therapy with various chemotherapeutic drugs may have a highly selective effect against cycling vascular endothelial cells, and may be relevant to the use of continuous or frequent administration of low doses of certain types of drugs as an optimal way of delivering antiangiogenic therapy.

Interferons alpha and beta down-regulate the expression of basic fibroblast growth factor in human carcinomas

Abstract: We investigated the influence of interferons alpha, beta, and gamma (IFN-alpha, -beta, and -gamma) on the production of basic fibroblast growth factor (bFGF) by human renal carcinoma cells. The human renal carcinoma cell metastatic line SN12PM6 was established in culture from a lung metastasis and SN12PM6-resistant cells were selected in vitro for resistance to the antiproliferative effects of IFN-alpha or IFN-beta. IFN-alpha and IFN-beta, but not IFN-gamma, down-regulated the expression of bFGF at the mRNA and protein levels by a mechanism independent of their antiproliferative effects. Down-regulation of bFGF required a long exposure (> 4 days) of cells to low concentrations (> 10 units/ml) of IFN-alpha or IFN-beta. The withdrawal of IFN-alpha or IFN-beta from the medium permitted SN12PM6-resistant cells to resume production of bFGF. The incubation of human bladder, prostate, colon, and breast carcinoma cells with noncytostatic concentrations of IFN-alpha or IFN-beta also produced down-regulation of bFGF production.

Cell surface tumor endothelial markers are conserved in mice and humans.

Abstract: We recently identified genes encoding tumor endothelial markers (TEMs) that displayed elevated expression during tumor angiogenesis. From both biological and clinical points of view, TEMs associated with the cell surface membrane are of particular interest. Accordingly, we have further characterized four such genes, TEM1, TEM5, TEM7, and TEM8, all of which contain putative transmembrane domains. TEM5 appears to be a seven-pass transmembrane receptor, whereas TEM1, TEM7, and TEM8 span the membrane once. We identified mouse counterparts of each of these genes, designated mTEM1, mTEM5, mTEM7, and mTEM8. Examination of these mTEMs in mouse tumors, embryos, and adult tissues demonstrated that three of them (mTEM1, mTEM5, and mTEM8) were abundantly expressed in tumor vessels as well as in the vasculature of the developing embryo. Importantly, expression of these mTEMs in normal adult mouse tissues was either undetectable or detected only in a small fraction of the vessels. These results demonstrate conservation of human and mouse tumor angiogenesis at the molecular level and support the idea that tumor angiogenesis largely reflects normal physiological neovasculaturization. The coordinate expression of TEM1, TEM5, and TEM8 on tumor endothelium in humans and mice makes these genes attractive targets for the development of antiangiogenic therapies.

Fatty acid carbon is essential for dNTP synthesis in endothelial cells

Abstract: The metabolism of endothelial cells during vessel sprouting remains poorly studied. Here we report that endothelial loss of CPT1A, a rate-limiting enzyme of fatty acid oxidation (FAO), causes vascular sprouting defects due to impaired proliferation, not migration, of human and murine endothelial cells. Reduction of FAO in endothelial cells did not cause energy depletion or disturb redox homeostasis, but impaired de novo nucleotide synthesis for DNA replication. Isotope labelling studies in control endothelial cells showed that fatty acid carbons substantially replenished the Krebs cycle, and were incorporated into aspartate (a nucleotide precursor), uridine monophosphate (a precursor of pyrimidine nucleoside triphosphates) and DNA. CPT1A silencing reduced these processes and depleted endothelial cell stores of aspartate and deoxyribonucleoside triphosphates. Acetate (metabolized to acetyl-CoA, thereby substituting for the depleted FAO-derived acetyl-CoA) or a nucleoside mix rescued the phenotype of CPT1A-silenced endothelial cells. Finally, CPT1 blockade inhibited pathological ocular angiogenesis in mice, suggesting a novel strategy for blocking angiogenesis.