Systemic mastocytosis (SM), a myeloproliferative disorder with variable clinical manifestations, is associated in most cases with the D816V mutation in KIT. The identification of the KIT D816V mutation in patients with systemic mastocytosis has gained a major prognostic significance in the last several years, largely because of the availability of tyrosine kinase receptor inhibitors such as imatinib. However, imatinib is ineffective in patients carrying KIT D816V mutation. In collaboration with Deciphera Pharmaceuticals, we thus evaluated inhibitors that target the switch pocket (SP) of KIT by altering the catalytic conformation of KIT, thus inhibiting mast cell proliferation and activation. Two SP inhibitors, DP-2976 and DP-4851, were examined for effects on neoplastic mast cell proliferation and mast cell activation. KIT D816V was blocked by these compounds in transfected 293T cells, HMC 1.1 and 1.2 human mast cell lines, and in CD34+-derived human mast cells activated by stem cell factor. Both inhibitors induced apoptosis in the neoplastic mast cell lines and reduced survival of primary bone marrow mast cells from patients with mastocytosis. Additionally, the SP inhibitors more selectively blocked SCF potentiation of FceRI-mediated mast cell activation. Overall, switch pocket inhibitors thus may provide therapeutic benefit. KIT has two major variants which differ by four amino acids (GNNK- or GNNK+) at the juxta-membrane region of the extracellular domain. We hypothesized that the expression pattern of these variants differ in systemic mastocytosis, and that transcripts containing the KIT D816V mutation segregate preferentially to one GNNK variant. A quantitative real-time PCR assay to assess GNNK- and GNNK+ transcripts from bone marrow mononuclear cells was developed. We found that the GNNK-/GNNK+ copy number ratio positively trended with % neoplastic mast cell involvement and KIT D816V containing transcripts displayed a significantly elevated GNNK-/GNNK+ copy number ratio. Relative expression of the GNNK- variant, but not the GNNK+, correlated with increasing percent of neoplastic mast cell involvement. A mast cell transfection system revealed that the GNNK- isoform of wild type KIT was associated with increased granule formation, histamine content and growth. These data suggest that neoplastic mast cells favor a GNNK- variant predominance, which in turn enhances the activating potential of the KIT D816V mutation and thus may influence therapeutic sensitivity in systemic mastocytosis.

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Cruse, Glenn; Metcalfe, Dean D; Olivera, Ana (2014) Functional deregulation of KIT: link to mast cell proliferative diseases and other neoplasms. Immunol Allergy Clin North Am 34:219-37
Chan, Eunice Ching; Bai, Yun; Kirshenbaum, Arnold S et al. (2014) Mastocytosis associated with a rare germline KIT K509I mutation displays a well-differentiated mast cell phenotype. J Allergy Clin Immunol 134:178-87
Carter, Melody C; Metcalfe, Dean D; Komarow, Hirsh D (2014) Mastocytosis. Immunol Allergy Clin North Am 34:181-96
Valent, P; Escribano, L; Broesby-Olsen, S et al. (2014) Proposed diagnostic algorithm for patients with suspected mastocytosis: a proposal of the European Competence Network on Mastocytosis. Allergy :
Williams, Kelli W; Metcalfe, Dean D; Prussin, Calman et al. (2014) Telangiectasia macularis eruptiva perstans or highly vascularized urticaria pigmentosa? J Allergy Clin Immunol Pract 2:813-5
Valent, P; Sotlar, K; Sperr, W R et al. (2014) Refined diagnostic criteria and classification of mast cell leukemia (MCL) and myelomastocytic leukemia (MML): a consensus proposal. Ann Oncol 25:1691-1700
Gotlib, Jason; Pardanani, Animesh; Akin, Cem et al. (2013) International Working Group-Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) & European Competence Network on Mastocytosis (ECNM) consensus response criteria in advanced systemic mastocytosis. Blood 121:2393-401
Chan, Eunice Ching; Bai, Yun; Bandara, Geethani et al. (2013) KIT GNNK splice variants: expression in systemic mastocytosis and influence on the activating potential of the D816V mutation in mast cells. Exp Hematol 41:870-881.e2
Uzzaman, Ashraf; Maric, Irina; Noel, Pierre et al. (2009) Pediatric-onset mastocytosis: a long term clinical follow-up and correlation with bone marrow histopathology. Pediatr Blood Cancer 53:629-34
Metcalfe, Dean D; Schwartz, Lawrence B (2009) Assessing anaphylactic risk? Consider mast cell clonality. J Allergy Clin Immunol 123:687-8

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