Abstract 2912: Protein pathway activation mapping of leukemia-associated JAK1 mutants

The Janus kinase 1 (JAK1) is a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors and plays a nonredundant role in lymphoid cell precursor proliferation, survival and differentiation. We documented that somatic mutations in JAK1 occur in individuals with acute lymphoblastic leukemia (ALL) (Flex et al. 2008, J Exp Med 205:751-8). JAK1 mutations were more prevalent among adult subjects with T-cell precursor ALL, where they accounted for approximately 20% of cases, and were associated with poor response to therapy and overall prognosis. In order to understand the molecular and cellular mechanisms by which aberrant JAK1 function contribute to leukemogenesis we analysed the signaling architecture of BaF3 cell lines stably expressing a series of leukemia-associated JAK1 gene mutations by Reverse Phase Protein Microarray (RPMA). We utilized BaF3 cell lines, stably expressing human wild type JAK1 and five ALL-associated mutants bearing missense mutations in different domains of the kinase. Cells were serum starved for 16 hours and lysed before and after induction with IL-3 for 20 minutes. RPMA analysis was performed to determine the phosphorylation/activation state of 102 different key signalling proteins involved in the major intracellular signal transduction pathways. Results showed that intacellular signaling downstream JAK/STAT is differentially modulated between cell lines expressing the different ALL-associated JAK1 mutants. Statistical analysis revealed that mutations affecting the pseudo-kinase and in the kinase domains resulted in a different phosphorylation pathway network compared to mutations involving the FERM and SH2 domains. Our results support a model in which mutations affecting distinct domains of JAK1 have a differential perturbing effect on JAK1 function and signalling. Characterization of the consequences of leukemia-associated JAK1 mutants on the protein signalling network may help to identify new therapeutic targets for ALL. The present findings further document that functional protein pathway activation mapping using RPMA represents a powerful approach to uncovering mutation-driven events, and elucidating the specific events associated with different mutations within a single protein. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2912. doi:10.1158/1538-7445.AM2011-2912