Transforming Mutations of Jak3 (A573V and M511I) Show Differential Sensitivity to Selective Jak3 Inhibitors

Abstract

Background A medical need exists for successfully treating patients afflicted with leukemia and especially those that relapse and ultimately become refractory to front line chemotherapies. Leukemia cases are particularly high within Hispanic populations where this disease is among the most frequently occurring cancer. A possible cause is somatic mutations in Janus tyrosine kinase (Jak3). Fourteen somatic mutations have been reported in Jak3, including M511I and A573V, from patients with various forms of leukemia. While several of these Jak3 mutations have been shown to possess transforming ability in cell lines, whether these mutations are susceptible to Jak3 selective inhibitors remains less clear. Methods The IL-3 dependent pro-B cell line Ba/F3 was virally transduced with plasmids encoding GFP and different mutant forms of Jak3, some of which conferred IL-3 independence. Sensitivity to pre-clinical and clinical Jak3 selective inhibitors was assessed for cellular viability and growth. Results Two Jak3 mutations conferred IL-3 independent growth in Ba/F3 cells. However, the level of drug sensitivity varied with respect to Jak3 inhibitors NC1153, CP-690,550, and EP-009. Conclusion Jak3 inhibitors CP-690,550 and NC1153 showed efficacy in reducing viability of Ba/F3 cells transformed with mutant forms of Jak3, thus providing new therapeutic strategies to treat these types of cancer.

JAK/STAT-Activating Genomic Alterations Are a Hallmark of T-PLL

“…JAK3 mutations were the most recurrent genomic aberration affecting JAK/STAT genes in this meta-analysis with a hotspot mutation rate of 36.4% (literature: 21% [12]-71% [17]). The oncogenic potential of the most frequent JAK3 mutation M511I as well as the less frequently occurring mutations A573V and V674A was shown in various systems: M511I, A573V, as well as V674A mutant cell lines demonstrated high phosphorylation of STAT5 and ERK, leading to cytokine independent growth [39,40]. When transplanting mice with bone marrow progenitor cells harboring the M511I or A573V mutation in JAK3, they develop a T-ALL-like disease, characterized by an expansion of immature CD8 + T-cells.…”

Failure of tofacitinib to achieve an objective response in a DDX3X-MLLT10 T-lymphoblastic leukemia with activating JAK3 mutations

“…Different activating mutations of JAK3 confer differential sensitivity to JAK inhibitors ( Losdyck et al 2015 ; Steven Martinez et al 2016 ). Preclinical data suggest that most, but not all, JAK3 mutants transform T-ALL cell lines to cytokine-independent proliferation in vitro and cause leukemia in vivo.…”

Deregulation of the Interleukin-7 Signaling Pathway in Lymphoid Malignancies

“…The transforming capacity of JAK3 mutations has been investigated using in vitro cell-based assays and in vivo bone marrow transplant models [ 84 , 94 , 95 , 96 ]. Although the majority of JAK3 mutations in ALL are located in the JH2 pseudokinase and JH1 kinase domain, the most frequent alteration, JAK3 p.M511I, affects an amino acid right outside the pseudokinase domain [ 67 , 89 , 90 , 97 ].…”

“…Moreover, not all mutations identified are gain-of-function alterations that drive leukemogenesis. So-called passenger mutations, such as some JAK3 kinase domain mutations and the majority of mutations in the FERM/SH2 domain of JAK3, do not contribute to cellular transformation nor leukemia development [ 84 , 94 , 95 , 96 ].…”

“…Ruxolitinib, which is a JAK1/JAK2-selective inhibitor, inhibited the proliferation of cells transformed by pseudokinase domain JAK3 mutants, whereas cells expressing JAK3 kinase domain mutations were less sensitive [ 94 , 95 ]. The latter were, in contrast, more sensitive to JAK3-specific inhibitors [ 84 , 95 , 96 ]. For the JAK1/JAK3-specific inhibitor tofacitinib, the pseudokinase and kinase domain mutants showed a similar sensitivity, whereas treatment with a combination of ruxolitinib and tofacitinib synergistically inhibited the proliferation of cells transformed by pseudokinase, but not kinase domain mutants [ 94 , 95 ].…”