Repression of miR-126 and upregulation of adrenomedullin in the stromal endothelium by cancer-stromal cross talks confers angiogenesis of cervical cancer.

miR-126 is an endothelial-specific microRNA essential for maintaining vessel integrity during development. Its role of tumor angiogenesis in cancer stroma is unclear. This study investigated the temporal and spatial expression and the role of miR-126 in the course of cervical carcinogenesis. miR-126 was found to be mainly expressed in the stromal endothelium of the uterine cervix. This downregulation was recapitulated in a cell coculture model, wherein cross talk of cervical cancer cells and fibroblasts induced a downregulation of miR-126 in human umbilical vein endothelial cells, with consequent increase of tube formation. Coinjection of cancer-associated fibroblasts of human cervix enhanced tumorigenesis of cervical cancer cells, with an increase of microvessel density and dye retention in the tumor vasculature. In association with angiogenesis, host-originated miR-126 in these xenograft tumors was progressively downregulated, whereas supplement of the miR-126 precursor in the coinjection suppressed angiogenesis and tumor growth. A proangiogenic gene adrenomedullin (ADM), which was found to be upregulated in the stroma of cervical cancer and which localized mainly in the blood and lymphatic vessels, was identified as a target of inhibition by miR-126 at the carcinoma in situ-to-invasion stage. The study suggests a cancer stroma cross talk induced repression of miR-126 and upregulation of ADM, and probably other proangiogenic factors, to facilitate angiogenesis and invasion growth of cervical cancer.