Inhibition of the MAP2K7-JNK pathway with 5Z-7-oxozeaenol induces apoptosis in T-cell acute lymphoblastic leukemia

Rational Design of Highly Potent and Selective Covalent MAP2K7 Inhibitors

The mitogen-activated protein kinase signaling cascade is conserved across eukaryotes, where it plays a critical role in the regulation of activities including proliferation, differentiation, and stress responses. This pathway propagates external stimuli through a series of phosphorylation events, which allows external signals to influence metabolic and transcriptional activities. Within the cascade, MEK, or MAP2K, enzymes occupy a molecular crossroads immediately upstream to significant signal divergence and cross-talk. One such kinase, MAP2K7, also known as MEK7 and MKK7, is a protein of great interest in the molecular pathophysiology underlying pediatric T cell acute lymphoblastic leukemia (T-ALL). Herein, we describe the rational design, synthesis, evaluation, and optimization of a novel class of irreversible MAP2K7 inhibitors. With a streamlined one-pot synthesis, favorable in vitro potency and selectivity, and promising cellular activity, this novel class of compounds wields promise as a powerful tool in the study of pediatric T-ALL.

Antileukemic properties of the kinase inhibitor OTSSP167 in T-cell acute lymphoblastic leukemia

Novel drugs are needed to increase treatment response in children with high-risk T-cell acute lymphoblastic leukemia (T-ALL). Following up on our previous report on the activation of the MAP2K7-JNK pathway in pediatric T-ALL, here we demonstrate that OTSSP167, recently shown to inhibit MAP2K7, has antileukemic capacity in T-ALL. OTSSP167 exhibited dose-dependent cytotoxicity against a panel of T-ALL cell lines with IC50 in the nanomolar range (10-50 nM). OTSSP167 induces apoptosis and cell cycle arrest in T-ALL cell lines, associated at least partially with the inhibition of MAP2K7 kinase activity and lower activation of its downstream substrate, JNK. Other leukemic T-cell survival pathways, such as mTOR and NOTCH1 were also inhibited. Daily intraperitoneal administration of 10 mg/kg OTSSP167 was well tolerated, with mice showing no hematological toxicity, and effective at reducing the expansion of human T-ALL cells in a cell-based xenograft model. The same dosage of OTSSP167 efficiently controlled the leukemia burden in the blood, bone marrow, and spleen of 3 patient-derived xenografts, which resulted in prolonged survival. OTSSP167 exhibited synergistic interactions when combined with dexamethasone, L-asparaginase, vincristine, and etoposide. Our findings reveal novel antileukemic properties of OTSSP167 in T-ALL and support the use of OTSSP167 as an adjuvant drug to increase treatment response and reduce relapses in pediatric T-ALL.

Phospho-Specific Flow Cytometry Reveals Signaling Heterogeneity in T-Cell Acute Lymphoblastic Leukemia Cell Lines

Several signaling pathways are aberrantly activated in T-ALL due to genetic alterations of their components and in response to external microenvironmental cues. To functionally characterize elements of the signaling network in T-ALL, here we analyzed ten signaling proteins that are frequently altered in T-ALL -namely Akt, Erk1/2, JNK, Lck, NF-κB p65, p38, STAT3, STAT5, ZAP70, Rb- in Jurkat, CEM and MOLT4 cell lines, using phospho-specific flow cytometry. Phosphorylation statuses of signaling proteins were measured in the basal condition or under modulation with H₂O₂, PMA, CXCL12 or IL7. Signaling profiles are characterized by a high variability across the analyzed T-ALL cell lines. Hierarchical clustering analysis documents that higher intrinsic phosphorylation of Erk1/2, Lck, ZAP70, and Akt, together with ZAP70 phosphorylation induced by H₂O₂, identifies Jurkat cells. In contrast, CEM are characterized by higher intrinsic phosphorylation of JNK and Rb and higher responsiveness of Akt to external stimuli. MOLT4 cells are characterized by higher basal STAT3 phosphorylation. These data document that phospho-specific flow cytometry reveals a high variability in intrinsic as well as modulated signaling networks across different T-ALL cell lines. Characterizing signaling network profiles across individual leukemia could provide the basis to identify molecular targets for personalized T-ALL therapy.