Hypoxia and hypoxia-inducible factor 1 repress SEMA4B expression to promote non-small cell lung cancer invasion.

Sema domain of semaphorin 4B (SEMA4B), which is an interacting protein of LNM35, plays an important role in lung cancer invasion. However, the regulation mechanism of this protein is completely unknown. Here, we report that hypoxia and hypoxia mimic reagent could downregulate the expression of SEMA4B in human non-small cell lung cancer (NSCLC) lines. We provide evidences that SEMA4B is a direct target of hypoxia-inducible factor 1 (HIF-1). Silencing the expression of HIF-1α in cancer cells by RNA interference abolished hypoxia-repressed SEMA4B expression. Using luciferase reporter assay, we showed that HIF-1α recognized a hypoxia-responsive element (HRE) of SEMA4B gene, which is required for HIF-1-repressed SEMA4B expression. Moreover, ectopic expression of SEMA4B abolished invasion of hypoxia-induced NSCLC cells. Taken together, these data would shed novel insights on the mechanisms for invasion of hypoxia-induced NSCLC cells.