Distinct signalling pathways for mutated KIT(V560G) and KIT(D816V) in mastocytosis

Summary Background. The activating mutations KIT(V560G) and KIT(D816V) are associated with mastocytosis. Thus, identifying and inhibiting the signalling pathways associated with mutated KIT gene offers a potentially important strategy for the treatment of mastocytosis. Aim. To correlate KIT mutations with specific signalling pathways in human mast‐cell lines using pathway inhibitors. Methods. Human mast‐cell (HMC) lines expressing KIT(V560G) (the cell line HMC‐1) and KIT(V560G and D816V) (HMC‐1.2) were treated with specific signalling pathway inhibitors for 1–5 days, and the inhibitory effects on growth were determined by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) cell‐proliferation assay, western blotting and flow cytometry. Results. Growth inhibitory assays and western blot analyses showed that the Janus kinase 3/signal transducer and activator of transcription (JAK3/STAT) pathway is the preferential signalling pathway for KIT(V560G), whereas the mechanistic target of rapamycin complex 1/4E‐binding protein 1 (mTORC1/4E‐BP1) pathway is preferentially linked to KIT(D816V). Inhibition of these critical signalling pathways results in programmed cell death. Conclusions. KIT(V560G) and KIT(D816V) use different signalling pathways that promote mast‐cell growth. Inhibitors of these specific pathways might be effective in treating mastocytosis.