HMGB1: a two-headed signal regulating tumor progression and immunity.

Cells of the innate immune system sense tissue damage recognizing in the extracellular environment bona fide intracellular moieties, like high mobility group box 1 (HMGB1). In the case of tumors, HMGB1 recognition has a paradoxical dual effect: it promotes tumor neoangiogenesis and triggers protective anti-neoplastic T-cell responses. Recent advances in the study of HMGB1 have identified candidate molecular mechanisms underlying these apparently contrasting outcomes. A surprising role for innate receptors, including toll like receptor 4 (TLR4), in the response to conventional cancer radio and chemotherapy has also recently emerged, providing new insight into the mechanisms by which these treatments actually work.