The broad, long-term objectives of the project are to identify and characterize protein tyrosine phosphatases (PTPases) as potential antagonists of the aberrant tyrosine phosphorylation associated with chronic myelogenous leukemia (CML). CML is a clonal disorder of the haematopoietic stem cell characterized by the Philadelphia chromosome, in which the c-Abl proto-oncogene becomes linked to the bcr gene on chromosome 22. This results in the generation of a fusion protein termed p210 bcr/abl, the kinase activity of which is enhanced relative to c-Abl, producing abnormal patterns of tyrosine phosphorylation in CML cells. Much research effort has focussed on the p210 bcr/abl kinase and the role of tyrosine phosphorylation in the disease. However protein phosphorylation in vivo is a reversible process in which the net phosphorylation state of a particular substrate depends upon the balance between the competing action of kinases and phosphatases. This project examines the potential involvement of PTPases in CML.
The specific aims are: 1) To characterize the role of PTP1B in controlling Abl functions in terms of: a) the physical association between PTP1B and c-Abl p210 bcr/abl, b) the effect of association of the enzyme activity of each component, c) the biological consequence of association and the ability of PTP1B to antagonize Abl. 2) To characterize modifications of PTP1B that may play a role in enhancing the stability of the PTP1B protein in p210 bcr/abl expressing derivatives of Mo7 cells. 3) To characterize a novel ser/Thr kinase that is recovered in immunoprecipitates of PTP1B. 4) To characterize novel PTPases in CML model systems and in human patient samples. The project presents chemical and molecular/cell biological approaches to studying PTPases in CML. The interaction between PTP1B and Abl will be defined by deletion/site directed mutagenesis. The effects of each component on the activity of the other will be determine in enzymatic assays. The biological consequences will be ascertained using retroviral expressions systems, for example to examine the potential of PTPases such as PTP1B to counter bcr/abl function. Covalent modifications, particularly phosphorylation, of PTP1B will be characterized by direct sequencing and comparative phosphopeptide mapping of in vitro and in vivo phosphorylated protein. Potential roles for such modification in determining the half-life of PTP1B and in controlling protein:protein interactions will be studied by a variety of techniques including analysis of immunoprecipitates of the PTPase from labelled cells. The grant also proposes reverse transcriptase-PCR based strategies to identify novel PTPases in CML model systems and patient samples to establish differences in PTPase expression that correlate with the presence of p210 bcr/abl. The health-relatedness of the project is that through the identification of PTPases that antagonize the activity of bcr/abl new insights will be provided into the molecular mechanisms underlying CML and new potential targets for therapeutic intervention will be uncovered.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Program Projects (P01)
Project #
Application #
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Berger, Alice H; Niki, Masaru; Morotti, Alessandro et al. (2010) Identification of DOK genes as lung tumor suppressors. Nat Genet 42:216-23
Rossi, Ferdinand; Yozgat, Yasemin; de Stanchina, Elisa et al. (2010) Imatinib upregulates compensatory integrin signaling in a mouse model of gastrointestinal stromal tumor and is more effective when combined with dasatinib. Mol Cancer Res 8:1271-83
Guo, Tianhua; Hajdu, Mihai; Agaram, Narasimhan P et al. (2009) Mechanisms of sunitinib resistance in gastrointestinal stromal tumors harboring KITAY502-3ins mutation: an in vitro mutagenesis screen for drug resistance. Clin Cancer Res 15:6862-70
Antczak, Christophe; Veach, Darren R; Ramirez, Christina N et al. (2009) Structure-activity relationships of 6-(2,6-dichlorophenyl)-8-methyl-2-(phenylamino)pyrido[2,3-d]pyrimidin-7-ones: toward selective Abl inhibitors. Bioorg Med Chem Lett 19:6872-6
Kashiwada, Masaki; Cattoretti, Giorgio; McKeag, Lisa et al. (2006) Downstream of tyrosine kinases-1 and Src homology 2-containing inositol 5'-phosphatase are required for regulation of CD4+CD25+ T cell development. J Immunol 176:3958-65
Liang, Xiquan; Hajivandi, Mahbod; Veach, Darren et al. (2006) Quantification of change in phosphorylation of BCR-ABL kinase and its substrates in response to Imatinib treatment in human chronic myelogenous leukemia cells. Proteomics 6:4554-64
Janas, Justyna; Skowronski, Jacek; Van Aelst, Linda (2006) Lentiviral delivery of RNAi in hippocampal neurons. Methods Enzymol 406:593-605
Zhao, Mingming; Janas, Justyna A; Niki, Masaru et al. (2006) Dok-1 independently attenuates Ras/mitogen-activated protein kinase and Src/c-myc pathways to inhibit platelet-derived growth factor-induced mitogenesis. Mol Cell Biol 26:2479-89
Oki, Shinji; Limnander, Andre; Yao, Pin Mei et al. (2005) Dok1 and SHIP act as negative regulators of v-Abl-induced pre-B cell transformation, proliferation and Ras/Erk activation. Cell Cycle 4:310-4
Wolff, Nicholas C; Veach, Darren R; Tong, William P et al. (2005) PD166326, a novel tyrosine kinase inhibitor, has greater antileukemic activity than imatinib mesylate in a murine model of chronic myeloid leukemia. Blood 105:3995-4003

Showing the most recent 10 out of 37 publications