Adhesion events in angiogenesis

Regulation of angiogenesis by the aging suppressor gene klotho

Advanced age is a major risk factor of peripheral artery disease. We examined the effects of the aging-suppressor gene klotho on angiogenesis in response to ischemia by introducing ischemic hindlimb model in mice heterozygously deficient for the klotho gene and in wild type mice. Blood flow recovery as assessed by laser doppler perfusion imaging and angiogenesis as assessed by density of PECAM-1/CD31-positive positive capillaries were markedly impaired in mice heterozygously deficient for the klotho gene (both <0.05). Our findings show that the aging-suppressor gene klotho affects angiogenesis and the possibility that age-related impairment of angiogenesis might be regulated by the klotho gene. Our results present a new possibility of therapeutic angiogenesis for patients of advanced age.

Networks and crosstalk: integrin signalling spreads

Multicellular organisms must coordinate signals from adhesion receptors with those from other signalling receptors (for example, growth factor receptors). Here, we briefly review paradigms of integrin-adhesion-receptor signalling. We discuss how adhesive signalling is coordinately regulated through intersecting networks. We also examine some examples of how some forms of integrin crosstalk may lead to unforeseen and potentially deleterious responses.

Cell-cell signaling by direct contact increases cell proliferation via a PI3K-dependent signal

We report a novel mechanism of cellular growth control. Increasing the density of endothelial or smooth muscle cells in culture increased cell-cell contact and decreased cell spreading, leading to growth arrest. Using a new method to independently control cell-cell contact and cell spreading, we found that introducing cell-cell contact positively regulates proliferation, but that contact-mediated proliferation can be masked by changes in cell spreading: Round cells with many contacts proliferated less than spread cells with none. Physically blocking cell-cell contact or inhibiting PI3K signaling abrogated cell-cell induced proliferation, but inhibiting diffusible paracrine signaling did not. Thus, direct cell-cell contact induces proliferation in these cells.

Inhibition of tumor angiogenesis by non-steroidal anti-inflammatory drugs: emerging mechanisms and therapeutic perspectives

Chronic intake of non steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced risk of developing gastrointestinal tumors, in particular colon cancer. Increasing evidence indicates that NSAID exert tumor-suppressive activity on pre-malignant lesions (polyps) in humans and on established experimental tumors in mice. Some of the tumor-suppressive effects of NSAIDs depend on the inhibition of cyclooxygenase-2 (COX-2), a key enzyme in the synthesis of prostaglandins and thromboxane, which is highly expressed in inflammation and cancer. Recent findings indicate that NSAIDs exert their anti-tumor effects by suppressing tumor angiogenesis. The availability of COX-2-specific NSAIDs opens the possibility of using this drug class as anti-angiogenic agents in combination with chemotheapy or radiotherapy for the treatment of human cancer. Here we will briefly review recent advances in the understanding of the mechanism by which NSAIDs suppress tumor angiogenesis and discuss their potential clinical application as anti-cancer agents.