guanosine-triphosphate and Lymphoma--T-Cell

RHOA is a member of RHO family small GTPases. Over the past 2 decades, numerous biochemical and cell biological studies on RHOA have demonstrated signalings such as activation of RHO-associated coiled-coil forming kinases through guanine nucleotide exchange and GTP hydrolysis, cellular responses such as actin fiber formation and myocin activation, biological consequences such as cell motility and cytokineses, etc. There have also been a plenty of active discussion on the roles of RHOA in tumorigenesis, primarily based on gain- and loss-of-function experiments. However, cell-type-specific functions of RHOA have only recently been delineated by conditional gene targeting strategies. Furthermore, very little information had been available on human cancer genetics until we and others recently reported frequent somatic RHOA mutations in a distinct subtype of T-cell-type malignant lymphoma called angioimmunoblastic T-cell lymphoma (AITL), and other T-cell lymphoma with AITL-like features. The RHOA mutations were very specific to these types of lymphoma among hematologic malignancies, and a single hotspot, glycine at the 17th position, was affected by the replacement with valine (G17V). Remarkably, G17V RHOA did not bind GTP, and moreover, it inhibited the GTP binding to wild-type RHOA. How G17V RHOA contributes to T-cell lymphomagenesis needs to be clarified.

Topics: Animals; Carcinogenesis; Guanosine Triphosphate; Humans; Lymphoma, T-Cell; Mutation, Missense; Protein Binding; rhoA GTP-Binding Protein

Topics: 3T3 Cells; Animals; Cell Membrane; Chromosome Mapping; Chromosomes, Human, Pair 21; GTP Phosphohydrolases; GTP-Binding Proteins; Guanine Nucleotide Exchange Factors; Guanosine Triphosphate; Humans; Lymphoma, T-Cell; Mice; Models, Biological; Mutagenesis; Neoplasm Invasiveness; Neoplasm Proteins; Neoplasms, Experimental; Platelet-Derived Growth Factor; Proteins; rac GTP-Binding Proteins; rhoA GTP-Binding Protein; Sequence Homology; Signal Transduction; T-Lymphoma Invasion and Metastasis-inducing Protein 1

In T lymphocytes, the Wiskott-Aldrich Syndrome protein (WASP) and WASP-interacting-protein (WIP) regulate T cell antigen receptor (TCR) signaling, but their role in lymphoma is largely unknown. Here we show that the expression of WASP and WIP is frequently low or absent in anaplastic large cell lymphoma (ALCL) compared to other T cell lymphomas. In anaplastic lymphoma kinase-positive (ALK+) ALCL, WASP and WIP expression is regulated by ALK oncogenic activity via its downstream mediators STAT3 and C/EBP-β. ALK+ lymphomas were accelerated in WASP- and WIP-deficient mice. In the absence of WASP, active GTP-bound CDC42 was increased and the genetic deletion of one CDC42 allele was sufficient to impair lymphoma growth. WASP-deficient lymphoma showed increased mitogen-activated protein kinase (MAPK) pathway activation that could be exploited as a therapeutic vulnerability. Our findings demonstrate that WASP and WIP are tumor suppressors in T cell lymphoma and suggest that MAP-kinase kinase (MEK) inhibitors combined with ALK inhibitors could achieve a more potent therapeutic effect in ALK+ ALCL.

Topics: Anaplastic Lymphoma Kinase; Animals; CCAAT-Enhancer-Binding Protein-beta; cdc42 GTP-Binding Protein; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cytoskeletal Proteins; Down-Regulation; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Guanosine Triphosphate; Humans; Intracellular Signaling Peptides and Proteins; Kaplan-Meier Estimate; Lymphoma, T-Cell; MAP Kinase Signaling System; Mice; Protein Binding; STAT3 Transcription Factor; T-Lymphocytes; Tumor Suppressor Proteins; Wiskott-Aldrich Syndrome Protein

BCX-34 inhibits RBC PNP in vitro from humans, rats, and mice with IC50S ranging from 5 to 36 nM. BCX-34 also, in the presence but not in the absence of deoxyguanosine, inhibits human CCRF-CEM T-cell proliferation with an IC50 of 0.57 microM but not rat or mouse T-cell proliferation up to 30 microM. Inhibition of human T-cell proliferation is accompanied by an accumulation of intracellular dGTP with an associated reduction in GTP. These nucleotide changes do not occur in BC16A mouse T-cells and explain why proliferation is not inhibited by PNP inhibitors in this case. Reduction in intracellular GTP is not essential for the antiproliferative action of BCX-34. Oral bioavailability of BCX-34 in rats is 76%. BCX-34 is orally active in elevating plasma inosine in rats (2-fold at 30 mg/kg), in suppressing ex vivo RBC PNP activity in rats (98% at 3 h. 100 mg/kg), and in suppressing ex vivo skin PNP in mice (39% at 3 h, 100 mg/kg). The results demonstrate that BCX-34 inhibits human PNP and T-cell proliferation, is orally bioavailable in rodents, and pharmacologically active in vivo in rodents after oral dosing with no apparent side effects or toxicity. BCX-34 may, therefore, be useful in treating human T-cell proliferative inflammatory disorders.

Topics: Animals; Cells, Cultured; Deoxyguanine Nucleotides; Guanine; Guanosine Triphosphate; Humans; Immunosuppressive Agents; Lymphocyte Activation; Lymphoma, T-Cell; Mice; Purine-Nucleoside Phosphorylase; Rats; T-Lymphocytes; Tumor Cells, Cultured

Several serine/threonine and tyrosine kinase signal transduction pathways have been recently linked to prolactin (PRL) action in lymphoid cells. Utilizing the lactogen-dependent, rat pre-T lymphoma cell line, Nb2-11, and the autonomous subline, Nb2-SFJCD1, studies were conducted to determine whether PRL- or interleukin-2 (IL-2)-stimulated Nb2 cell proliferation is coupled to the activation of p21ras and mitogen-activated protein (MAP) kinase. Stimulation of Nb2-11 cells, growth-arrested in the early G1 phase of the cell cycle, with PRL or IL-2 rapidly (5-10 min) provoked GTP binding to Ras, enhanced tyrosyl phosphorylation of MAP kinase, significantly increased its enzymatic activity, and caused its nuclear translocation. The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), which directly activates protein kinase C, similarly activated Ras and MAP kinase but failed to cause its nuclear translocation. Tyrosine kinase antagonism with genistein inhibited PRL-stimulated Ras and MAP kinase activation. In other experiments, Ras and MAP kinase were each found to be constitutively active in the Nb2-SFJCD1 line. The addition of PRL to these cultures enhanced the activity of these signaling proteins. Finally, the effects of PRL, IL-2, TPA, and phosphatase inhibition on Nb2-11 cell population density and [3H]thymidine uptake were compared. The addition of PRL, IL-2, and TPA significantly stimulated[3H] thymidine incorporation, while only the polypeptide growth factors augmented cell density. Phosphatase inhibition had no effect on either parameter. These results indicate that Nb2 cell proliferation is associated with the early activation of Ras and MAP kinase. Moreover, tyrosyl phosphorylation upstream of Ras activation appears to be required for its subsequent stimulation of mediators, which activate MAP kinase. Protein kinase C activation may be coupled to MAP kinase activation but is not sufficient for Nb2 cell proliferation.

Topics: Animals; Calcium-Calmodulin-Dependent Protein Kinases; Cell Division; Enzyme Activation; Enzyme Inhibitors; Genistein; Guanosine Triphosphate; Interleukin-2; Isoflavones; Lymph Nodes; Lymphoma, T-Cell; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Phosphorylation; Prolactin; Protein-Tyrosine Kinases; Proto-Oncogene Proteins p21(ras); Rats; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Tyrosine