FLT3LG and brain neoplasm: To test the hypothesis that HMGB1 secreted from GBM-bearing mice after treatment with Flt3L plus TK (GCV) mediates TLR2 signaling and T cell-dependent brain tumor regression in vivo, we blocked circulating HMGB1 in vivo using glycyrrhizin or specific anti-HMGB1 immunoglobulins.