The hallmark of chronic myelogenous leukemia (CML) is the Philadelphia chromosome, which arises from the reciprocal translocation of the c-abl proto-onogene on chromosome 9 and the bcr locus on chromosome 22. This translocation results in the expression of a 210 kDa fusion protein (Bcr-Abl) with constitutive tyrosine kinase activity that is responsible for CML pathogenesis. Bcr-Abl activates several signaling proteins important for the proliferation and survival of myeloid progenitors, including the Src family kinases Hck and Lyn, the Stat5 transcription factor and upstream components of the Ras/Erk pathway. Previous work from our laboratory found that kinase-defective Hck blocks Bcr-Abl-induced transformation of DAGM myeloid leukemia cells to cytokine independence, suggesting that activation of the Src kinase family may be essential to oncogenic signaling by Bcr-Abl.
Chapter II explores the contribution of Src kinases to Bcr-Abl signaling in vivo, using selective Src family kinase inhibitors. Inhibition of Src family kinases in Ph+ CML cell lines resulted in growth arrest, induction of apoptosis and blocked Stat5 and Erk activaton downstream. These data implicate the Src kinase family in Stat5 and Erk activation downstream of Bcr-Abl, and identify myeloid-specific Src kinases as potential drug targets in CML.
In Chapter III, I investigated the biochemical interactions between myeloid Src family members and Bcr-Abl. Hck, Lyn and Fyn each bind the kinase domain, C-terminal tail, and SH3/SH2 region of Bcr-Abl and strongly phosphorylated the Bcr-Abl SH3-SH2 protein in vitro. Seven phosphorylated tyrosine residues were identified and substitution of these residues with phenylalanine in the context of full-length Bcr-Abl blocked transformation of TF-1 myeloid cells to cytokine independence. The position of several of these tyrosines in the crystal structure of c-Abl and transformation defect of the Bcr-Abl mutant suggest that phosphorylation by Src kinases may impact Bcr-Abl autoregulation and downstream oncogenic signaling. Taken together, these data firmly establish an important role for Src family tyrosine kinases in Bcr-Abl-mediated oncogenic signaling and implicate Src kinases as a promising therapeutic target for chronic myelogenous leukemia.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12152004-152152 |
| Date | 21 December 2004 |
| Creators | Wilson, Matthew Brian |
| Contributors | Baskaran Rajasekaran, Thomas E. Smithgall, Martin C. Schmidt, Jack C. Yalowich, Richard A. Steinman |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-12152004-152152/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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