Tumor angiogenesis is caused by single melanoma cells in a reactive oxygen species and NF-κB dependent manner

Abstract

Melanomas have a high angiogenic potential, but respond poorly to medical treatment and metastasize very early. To understand the early events in tumor angiogenesis, animal models with high tumor- and blood vessel resolution are required which provide the opportunity to test small molecule inhibitors for modulating the angiogenic tumor programme. We have established a transgenic melanoma angiogenesis model in the small laboratory fish species Japanese medaka. Here, pigment cells are transformed by an oncogenic receptor tyrosine kinase in fishes expressing GFP throughout their vasculature. We show that angiogenesis occurs in a reactive oxygen species- and NF-κB-dependent, but hypoxia-independent manner. Intriguingly, we observed that blood vessel sprouting is induced even by single transformed pigment cells. The oncogenic receptor as well as human melanoma cells harbouring other oncogenes caused the production of pro-angiogenic factors, most prominently angiogenin, via NF-κB signalling. Inhibiting NF-κB prevented tumor angiogenesis and led to the regression of existing tumor blood vessels. In conclusion, our high resolution medaka melanoma model discloses that ROS and NF-κB signaling from single tumor cells causes hypoxia-independent angiogenesis, thus demonstrating that the intrinsic malignant tumor cell features are sufficient to initiate and maintain a pro-angiogenic signaling threshold.