ag-490 and Precursor-Cell-Lymphoblastic-Leukemia-Lymphoma

Topics: Drug Design; Forecasting; Humans; Nitriles; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Protein-Tyrosine Kinases; Signal Transduction; Tyrphostins

JAK2 plays important roles in the regulation of a variety of cellular processes including cell migration, proliferation, and protection from apoptosis. Recently the L611S point mutation in JAK2 has been identified in a child with acute lymphoblastic leukemia. Here we analyzed the mechanism by which JAK2 exhibits its oncogenicity. In BaF3 murine hematopoietic cells, L611S mutant increased the expression of antiapoptotic proteins including X chromosome-linked inhibitor of apoptosis protein, inhibitor of apoptosis protein, and Bcl-XL. We also showed that JAK2 L611S mutant protects BaF3 cells from cytokine withdrawal-induced apoptotic cell death and leads to cytokine-independent cell growth. Furthermore BaF3 cells expressing JAK2 L611S mutant gained the ability to induce tumorigenesis in nude mice. The L611S mutant also exhibited malignancy, including prompt invasion and spreading into various organs, leading to rapid lethality of the mice. Finally we showed that a specific JAK2 inhibitor, AG490, potently inhibited cytokine-independent cell growth induced by JAK2 L611S mutant via the induction of apoptotic cell death. In addition, treatment with AG490 significantly inhibited the JAK2 L611S mutant-induced tumorigenesis in nude mice. Thus, our results both in vitro and in vivo strongly suggest that L611S mutant of JAK2 harbors potent oncogenic activity, and this probably requires the antiapoptotic signaling pathway.

Topics: Animals; Antineoplastic Agents; Apoptosis; Blotting, Western; Cell Proliferation; Cytokines; Flow Cytometry; Genetic Vectors; Hematopoietic Stem Cells; Janus Kinase 2; Liver Neoplasms, Experimental; Lymphatic Metastasis; Mice; Mice, Inbred BALB C; Mice, Nude; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Neoplasm Invasiveness; Phosphorylation; Point Mutation; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Proto-Oncogene Proteins c-akt; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Splenic Neoplasms; STAT5 Transcription Factor; Transfection; Tyrphostins

The ability of death-inducing tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to selectively kill a variety of cancer cells has been largely described, but one of the major concerns with the treatment is the occurrence of drug resistance and possible toxic side effects. Here, we report that TRAIL induces apoptosis in Jurkat and SUPT1 T cell lines and in human T-ALL blasts but not in healthy subject-derived peripheral blood mononuclear cells. In parallel, the treatment with TRAIL and Tyrphostin (AG-490), a selective Janus kinase 2 inhibitor, produces an evident enhancement of cytotoxicity, characterized by a significant inhibition of Stat3 phosphorylation compared to controls or to TRAIL alone-treated samples, and associated with a dramatic decrease of both cIAP-1 and cIAP-2 mRNA levels. Downregulation of cIAP-1 and cIAP-2 by specific small interference RNAs significantly amplifies TRAIL-reduced cytotoxicity. All together, these findings strongly indicate that cIAP-1 and cIAP-2 downregulation is a fundamental step in the signaling pathways mediating the combinatorial effect of TRAIL and AG-490 on T cell leukemia. These findings may help to open new routes for the development of less toxic pharmacological strategies in the treatment of patients affected by TRAIL-sensitive leukemias.

Topics: Antibodies; Antineoplastic Agents; Apoptosis; Baculoviral IAP Repeat-Containing 3 Protein; Down-Regulation; Drug Synergism; Humans; Inhibitor of Apoptosis Proteins; Janus Kinase 2; Jurkat Cells; Leukemia, T-Cell; Leukocytes, Mononuclear; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Receptors, TNF-Related Apoptosis-Inducing Ligand; RNA, Small Interfering; Signal Transduction; STAT3 Transcription Factor; TNF-Related Apoptosis-Inducing Ligand; Tyrphostins; Ubiquitin-Protein Ligases

To investigate the relation of Jak3 constitutive activation and acute lymphoblastic leukemia(ALL).. NALM-6 cells were treated with varying concentrations of AG490, a Jak3 inhibitor. Apoptosis and proliferation of NALM-6 cells were tested by flow cytometry (FCM) analysis and MTT assay.. With the exception of AG490 5 mumol/L, the AG490 10, 15, 20 mumol/L induced a strong apoptotic response in NALM-6 cells by FCM analysis(P < 0.05) and significantly inhibited the proliferation of NALM-6 cells by MTT assay(P < 0.05). All of the effects were dose-dependent.. Jak3 inhibitor AG490 can inhibit proliferation and induce apoptosis in NALM-6 cells, and Jak3 activation is associated with pre-B ALL.

Topics: Antineoplastic Agents; Apoptosis; Humans; Janus Kinase 3; Precursor B-Cell Lymphoblastic Leukemia-Lymphoma; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Protein-Tyrosine Kinases; Tumor Cells, Cultured; Tyrphostins

Acute lymphoblastic leukaemia (ALL) is the most common cancer of childhood. Despite the progress achieved in its treatment, 20% of cases relapse and no longer respond to chemotherapy. The most common phenotype of ALL cells share surface antigens with very early precursors of B cells and are therefore believed to originate from this lineage. Characterization of the growth requirement of ALL cells indicated that they were dependent on various cytokines, suggesting paracrine and/or autocrine growth regulation. Because many cytokines induce tyrosine phosphorylation in lymphoid progenitor cells, and constitutive tyrosine phosphorylation is commonly observed in B-lineage leukaemias, attempts have been made to develop protein tyrosine kinase (PTK) blockers of leukaemia cell growth. Here we show that leukaemic cells from patients in relapse have constitutively activated Jak-2 PTK. Inhibition of Jak-2 activity by a specific tyrosine kinase blocker, AG-490, selectively blocks leukaemic cell growth in vitro and in vivo by inducing programmed cell death, with no deleterious effect on normal haematopoiesis.

Topics: Animals; Antineoplastic Agents; B-Lymphocytes; Cell Division; Enzyme Inhibitors; Humans; Janus Kinase 2; Mice; Mice, SCID; Neoplasm Transplantation; Nitriles; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Structure-Activity Relationship; Tumor Cells, Cultured; Tyrphostins