KIT and systemic mastocytosis: In addition to targeting the KIT D816V receptor and its downstream substrates in SM, HMC cells and primary neoplastic mast cells derived from aggressive SM patients carrying the KIT D816V mutation appear to be sensitive to treatment by demethylating agents including 5-azacytidine (5-AZA) and 5-aza-2′deoxycytidine (Decitabine / DAC).