Chronic arsenic exposure and angiogenesis in human bronchial epithelial cells via the ROS/miR-199a-5p/HIF-1α/COX-2 pathway.

BACKGROUND: Environmental and occupational exposure to arsenic is a major public health concern. Although it has been identified as a human carcinogen, the molecular mechanism underlying the arsenic-induced carcinogenesis is not well understood. OBJECTIVES: We aimed to determine the role and mechanisms of miRNAs in arsenic-induced tumor angiogenesis and tumor growth. METHODS: We utilized an in vitro model in which human lung epithelial BEAS-2B cells were transformed through long-term exposure to arsenic. A human xenograft tumor model was established to assess tumor angiogenesis and tumor growth in vivo. Tube formation assay and chorio-allantoic membranes assay were used to assess tumor angiogenesis. RESULTS: We found that miR-199a-5p expression levels were more than 100-fold lower in arsenic-transformed cells than parental cells. Re-expression of miR-199a-5p impaired arsenic-induced angiogenesis and tumor growth through its direct targets HIF-1 alpha and COX-2. We further showed that arsenic induced COX-2 expression through HIF-1 regulation at the transcriptional level. In addition, we demonstrated that reactive oxygen species are an upstream event of miR-199a-5p/HIF-1 alpha/COX-2 pathway in arsenic-induced carcinogenesis. CONCLUSION: The findings establish critical roles of miR-199a-5p and its downstream targets HIF-1/COX-2 in arsenic-induced tumor growth and angiogenesis.