Dendritic cells turn traitorous

Dendritic cells present antigens during immune responses and are thought to be important in antitumor activity. However, under the influence of the known cancer promoter VEGF-A, dendritic cell precursors take on the trappings of endothelial cells and contribute to tumor blood vessels, speeding the cancer's growth, according to a report by Jose Conejo-Garcia, Fabian Benencia, George Coukos (University of Pennsylvania Medical Center, Philadelphia, PA), and colleagues.

Hoping to boost anti-tumor immunity in a mouse model of ovarian cancer, Conejo-Garcia et al. found that expression of the inflammatory peptides β-defensins attracted dendritic cells to the tumor. In tumors with low levels of VEGF-A, the immune cells slowed the cancer's growth presumably via anti-tumor immunity, but when VEGF-A was abundant, they actually promoted tumor growth via increased vascularization. The dendritic cells started expressing endothelial cell surface markers...