Novel tissue-specific mechanism of regulation of angiogenesis and cancer growth in response to hyperglycemia.

BACKGROUND: Hyperglycemia is an independent risk factor for the development of vascular diabetic complications, which are characterized by endothelial dysfunction and tissue-specific aberrant angiogenesis. Tumor growth is also dependent on angiogenesis. Diabetes affects several cancers in a tissue-specific way. For example, it positively correlates with the incidence of breast cancer but negatively correlates with the incidence of prostate cancer. The tissue-specific molecular mechanisms activated by hyperglycemia that control angiogenesis are unknown. Here we describe a novel tissue- and cell-specific molecular pathway that is activated by high glucose and regulates angiogenesis. METHODS AND RESULTS: We have identified microRNA 467 (miR-467) as a translational suppressor of thrombospondin-1 (TSP-1), a potent antiangiogenic protein that is implicated in the pathogenesis of several diabetic complications. miR-467 was upregulated by hyperglycemia in a tissue-specific manner. It was induced by high glucose in microvascular endothelial cells and in breast cancer cells, where it suppressed the production of TSP-1 by sequestering mRNA in the nonpolysomal fraction. Mutation of the miR-467 binding site in TSP-1 3' UTR or miR-467 inhibitor relieved the translational silencing and restored TSP-1 production. In in vivo angiogenesis models, miR-467 promoted the growth of blood vessels, and TSP-1 was the main mediator of this effect. Breast cancer tumors showed increased growth in hyperglycemic mice and expressed higher levels of miR-467. The antagonist of miR-467 prevented the hyperglycemia-induced tumor growth. CONCLUSIONS: Our results demonstrate that miR-467 is implicated in the control of angiogenesis in response to high glucose, which makes it an attractive tissue-specific potential target for therapeutic regulation of aberrant angiogenesis and cancer growth in diabetes.

The integrin coactivator kindlin-2 plays a critical role in angiogenesis in mice and zebrafish.

Kindlin-2, a widely distributed cytoskeletal protein, has been implicated in integrin activation, and its absence is embryonically lethal in mice and causes severe developmental defects in zebrafish. Knockdown of kindlin-2 levels in endothelial cells resulted in defective adhesive and migratory responses, suggesting that angiogenesis might be aberrant even with partial reduction of kindlin-2. This hypothesis has now been tested in the kindlin-2(+/-) mice. RM1 prostate tumors grown in kindlin-2(+/-) mice had fewer blood vessels, which were thinner and shorter and supported less tumor growth compared with wild-type littermates. The vessels that did form in the kindlin-2(+/-) mice lacked smooth muscle cells and pericytes and had thinner basement membranes, indicative of immature vessels. VEGF-induced angiogenesis in matrigel implants was also abnormal in the kindlin-2(+/-) mice. Vessels in the kindlin-2(+/-) mice were leaky, and BM transplantation from kindlin-2(+/-) to WT mice did not correct this defect. Endothelial cells derived from kindlin-2(+/-) mice had integrin expression levels similar to WT mice but reduced αVß3-dependent signaling, migration, adhesion, spreading, and tube formation. Developmental angiogenesis was markedly impaired by kindlin-2 morpholinos in zebrafish. Taken together, kindlin-2 plays an important role in pathologic and developmental angiogenesis, which arises from defective activation of integrin αVß3.