Date Published: July 15, 2012
Publisher: John Wiley & Sons, Ltd.
Author(s): E Hadzijusufovic, B Peter, H Herrmann, T Rülicke, S Cerny-Reiterer, K Schuch, L Kenner, T Thaiwong, V Yuzbasiyan-Gurkan, W F Pickl, M Willmann, P Valent.
Advanced mast cell (MC) disorders are characterized by uncontrolled growth of neoplastic MC in various organs, mediator-related symptoms, and a poor prognosis. Kit mutations supposedly contribute to abnormal growth and drug resistance in these patients.
We established a novel canine mastocytoma cell line, NI-1, from a patient suffering from MC leukemia.
NI-1 cells were found to form mastocytoma lesions in NOD/SCID IL-2Rgammanull mice and to harbor several homozygous Kit mutations, including missense mutations at nucleotides 107(C→T) and 1187(A→G), a 12-bp duplication (nucleotide 1263), and a 12-bp deletion (nucleotide 1550). NI-1 cells expressed several MC differentiation antigens, including tryptase, Kit, and a functional IgE receptor. Compared to the C2 mastocytoma cell line harboring a Kit exon 11 mutation, NI-1 cells were found to be less responsive against the Kit tyrosine kinase inhibitors (TKI) masitinib and imatinib, but were even more sensitive against proliferation-inhibitory effects of the mammalian target of rapamycin (mTOR) blocker RAD001 and PI3-kinase/mTOR blocker NVP-BEZ235. The Kit-targeting multikinase inhibitors PKC412 and dasatinib were also found to override TKI resistance in NI-1 cells, and produced growth inhibition with reasonable IC50 values (<0.1 μM). NI-1 may serve as a useful tool to investigate IgE-dependent reactions and mechanisms of abnormal growth and drug resistance in neoplastic MC in advanced mastocytosis.
Mastocytomas are among the most frequent life-threatening neoplasms in dogs (29). During the past few years, Kit has been identified as a major molecular target in neoplastic MC in humans and canines (6–12). In both species, Kit-targeting TKI have been used to counteract the growth of neoplastic MC (6–12, 16–18). However, resistances against TKI have been described (10, 12, 18). Although the exact mechanisms remain unknown, several observations suggest that mutations in Kit and other genes may be involved. To better define the mechanisms of drug resistance in canine MC disorders, it seems important to create novel robust cell line models. We have established a novel canine MC line, NI-1, which harbors several Kit mutations and exhibits relative resistance against masitinib and other Kit-targeting TKI.