HMGB1 and cancer: These include High Mobility Group Box 1 (HMGB1) and the extracellular release of ATP, which can activate professional antigen presenting cells (APCs), such as the dendritic cell (DC), and engender tumor antigen-specific T-cell responses.6,7 In addition, the induction of DNA damage subsequent to treatment with IR can lead to the production of novel (and potentially immunogenic) proteins and has been shown to upregulate tumor cell expression of class I MHC.5 Taken together, these data demonstrate the immunogenic potential of radiation therapy for cancer.