Cooperating JAK1 and JAK3 mutants increase resistance to JAK inhibitors

Abstract

Key Points• Cells transformed by activating JAK1 mutations become resistant to JAK inhibitor by acquiring activating mutations in JAK3 and vice versa.• JAK1 and JAK3 mutants cooperatively activate STAT transcription factors.The acquisition of growth signal self-sufficiency is 1 of the hallmarks of cancer. We previously reported that the murine interleukin-9-dependent TS1 cell line gives rise to growth factor-independent clones with constitutive activation of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway. Here, we show that this transforming event results from activating mutations either in JAK1, JAK3, or in both kinases. Transient and stable expression of JAK1 and/or JAK3 mutants showed that each mutant induces STAT activation and that their coexpression further increases this activation. The proliferation of growth factor-independent TS1 clones can be efficiently blocked by JAK inhibitors such as ruxolitinib or CMP6 in short-term assays. However, resistant clones occur upon long-term culture in the presence of inhibitors. Surprisingly, resistance to CMP6 was not caused by the acquisition of secondary mutations in the adenosine triphosphate-binding pocket of the JAK mutant. Indeed, cells that originally showed a JAK1-activating mutation became resistant to inhibitors by acquiring another activating mutation in JAK3, whereas cells that originally showed a JAK3-activating mutation became resistant to inhibitors by acquiring another activating mutation in JAK1. These observations underline the cooperation between JAK1 and JAK3 mutants in T-cell transformation and represent a new mechanism of acquisition of resistance against JAK inhibitors. (Blood. 2014;124(26):3924-3931)

RNA sequencing unravels the genetics of refractory/relapsed T-cell acute lymphoblastic leukemia. Prognostic and therapeutic implications

“…Moreover, cells with a JAK1 mutation alone were more sensitive than cases harboring additional mutations in the pathway, as observed in cell lines. 45 As already noted for JAK/STAT, RAS/PTEN alterations are a common feature of T-ALL; their prognostic impact is still controversial in childood. [46][47][48][49] In particular, in their study of children treated with the Berlin-FrankfurtMunster protocol, Bandapalli et al reported that patients with PTEN and NOTCH1 mutations had a marked sensitivity to induction treatment and excellent long-term outcome, similar to that of patients with NOTCH1 mutations only and more favorable than that of patients with PTEN mutations only.…”

Distinct Acute Lymphoblastic Leukemia (ALL)-associated Janus Kinase 3 (JAK3) Mutants Exhibit Different Cytokine-Receptor Requirements and JAK Inhibitor Specificities

“…Cell lysate preparation, gel electrophoresis, and transfer to nitrocellulose membranes were performed as previously described (16 Murine Bone Marrow Transplantation-Balb/c mice were purchased from Charles River Laboratories. Harvest of bone marrow cells from male donor mice, lineage negative cells enrichment, transduction with viral supernatant, and injection into irradiated female recipient mice was performed as previously described (13).…”

“…6B. By contrast, the receptor-dependent mutants map to the interface between pseudokinase and kinase domains, as previously described (16).…”

“…To address this question, other activating mutations of the kinase domain were investigated. These consisted of one JAK3 mutation associated with T cell pro-lymphocytic leukemia (Y824D) (24), three ALL-associated mutants (L875H, P906S, and E958K), 7 and one mutant described in a murine T cell line (T848A) (16). As illustrated in Fig.…”

Therapeutic targeting of IL-7Rα signaling pathways in ALL treatment

“…61 Experience with MPN suggests that resistance to JAK inhibition may develop, fueled by additional mutations in JAK proteins, increased JAK2 expression, or shifting transphosphorylation partners; resistance has been identified in both MPN and T-ALL. 62,63 There are several potential approaches to overcoming resistance to JAK inhibition. New generations of JAK inhibitors are being developed to bind inactive forms of JAK to overcome resistance.…”