HMGB1 and neoplasm: Filipin and BODIPY‐cholesterol stainingConfocal microscopyFlow cytometryATP and HMGB1 release assaysProphylactic vaccination‐rechallenge assaysIn vivo tumor growth and survival studiesT‐cell depletion experimentsImmunoblottingqRT‐PCRmolecular docking for NPC1/2 bindingTEM