MPO and neoplasm: Papilloma induced by topical treatment of susceptible mice with 7, 12-dimethylbenz[α]anthracene (DMBA) and 12-O-tetradecanoyl phorbol-13-acetate (TPA) contained substantial numbers of MPO+ CXCR2+ Gr1+ MDSCs, and CXCR2 KO mice were profoundly resistant to the tumor induction [238].