HMGB1 and mantle cell lymphoma: Treatment of diffuse large B‐cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) cell lines with 9‐cis‐retinoic acid (RA) and IFN‐α was found to exert therapeutic effects through the induction of CRT outgrowth, early HSP70/90 membrane exposure, CD47 downregulation, and enhanced HMGB1 secretion.