Neoplasia Driven by Mutant c-KIT Is Mediated by Intracellular, Not Plasma Membrane, Receptor Signaling

Abstract

Activating mutations in c-KIT are associated with gastrointestinal stromal tumors, mastocytosis, and acute myeloid leukemia. In attempting to establish a murine model of human KIT^D816V (hKIT^D816V)-mediated leukemia, we uncovered an unexpected relationship between cellular transformation and intracellular trafficking. We found that transport of hKIT^D816V protein was blocked at the endoplasmic reticulum in a species-specific fashion. We exploited these species-specific trafficking differences and a set of localization domain-tagged KIT mutants to explore the relationship between subcellular localization of mutant KIT and cellular transformation. The protein products of fully transforming KIT mutants localized to the Golgi apparatus and to a lesser extent the plasma membrane. Domain-tagged KIT^D816V targeted to the Golgi apparatus remained constitutively active and transforming. Chemical inhibition of intracellular transport demonstrated that Golgi localization is sufficient, but plasma membrane localization is dispensable, for downstream signaling mediated by KIT mutation. When expressed in murine bone marrow, endoplasmic reticulum-localized hKIT^D816V failed to induce disease in mice, while expression of either Golgi-localized HyKIT^D816V or cytosol-localized, ectodomain-deleted KIT^D816V uniformly caused fatal myeloproliferative diseases. Taken together, these data demonstrate that intracellular, non-plasma membrane receptor signaling is sufficient to drive neoplasia caused by mutant c-KIT and provide the first animal model of myelomonocytic neoplasia initiated by human KIT^D816V.

We thank Stuart Kornfeld, Linda Pike, Thomas Jahn, and Paddy Ross for valuable discussions and Timothy Ley, Timothy Graubert, Katherine Weilbaecher, Daniel Link, and Julie O'Neal for critical reading of the manuscript. Leonie Ashman and Masao Mizuki provided valuable reagents. We are grateful to Richard Steet for technical assistance with immunofluorescence staining and Bill Eades for assistance with flow cytometry.

This work was supported by NIH grant P01 CA 101937-01 (M.H.T.).