Angiogenesis, a crucial step in tumor growth
and metastasis, is regulated by various pro- or anti-angiogenic
factors. Recently, microRNAs have been shown to
modulate angiogenic processes by modulating the expression
of critical angiogenic factors. However, roles of tumorderived
microRNAs in regulating tumor vascularization
remain to be elucidated. In this study, we found that delivery
of miR-494 into human vascular endothelial cells (ECs)
enhanced the EC migration and promoted angiogenesis. The
angiogenic effect of miR-494 was mediated by the targeting
of PTEN and the subsequent activation of Akt/eNOS pathway.
Importantly, co-culture experiments demonstrated that
a lung cancer cell line, A549, secreted and delivered miR-
494 into ECs via a microvesicle-mediated route. In addition,
we found that the expression of miR-494 was induced in the
tumor cells in response to hypoxia, likely via a HIF-1amediated
mechanism. Furthermore, a specific miR-494
antagomiR effectively inhibited angiogenesis and attenuated
the growth of tumor xenografts in nude mice. Taken
together, these results demonstrated that miR-494 is a novel
tumor-derived paracrine signal to promote angiogenesis and
tumor growth under hypoxic condition.