Metastatic spread is a characteristic feature of malignant tumor disease. The transcription factor hypoxia-inducible factor 1 (HIF-1) coordinates hypoxia-induced gene expression in cancer cells and is known to be pro-metastatic. Because in vitro hypoxic HIF-1 activity can be modulated by nitric oxide we investigated the effects of NO exposure on hematogenous metastasis by injection of B16F10-melanoma cells into the tail vein of C57Bl/6J-mice. Nodules visible on lung surface were counted fifteen days after injection. Twelve hours of hypoxic pre-incubation of B16F10-melanoma cells led to increased formation of lung nodules. In contrast simultaneous pre-incubation with 100 µM DETA-NO completely eliminated this hypoxic effect. In vitro experiments performed in parallel showed a reduced hypoxic induction of the HIF-1 target gene carbonic anhydrase IX after application of DETA-NO.

Given that one of the pro-metastatic characteristics of HIF-1 is promoting adhesion of intravascularly circulating tumor cells to endothelium we will establish an in vitro adhesion assay to test if this effect also plays a prominent role during lung metastasis of B16F10 melanoma cells.

Further in vitro and in vivo experiments e.g. with stable HIF-1 knock down B16F10-melanoma cells will provide evidence for the role of HIF-1 in hematogenous metastasis after NO exposure.