Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023473 (chronic myeloid leukemia)
 18,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The chimeric BCR/ABL protein is characteristic of Philadelphia (Ph)+ leukemia because it is the direct product of the Ph translocation and it has been shown to play a causal role in the genesis of leukemia. The BCR/ABL protein exhibits a deregulated tyrosine-kinase activity capable of phosphorylating different cellular substrates in vivo and in vitro. CRKL, an adaptor protein consisting of SH2 and SH3 domains in the absence of a catalytic domain, is one potential in vivo substrate of BCR/ABL. Previous experiments have shown that CRKL is phosphorylated on tyrosine in the chronic myelogenous leukemia (CML) cell line K562 and that CRKL is a substrate for ABL and for BCR/ABL in COS-1 cells. In the current study, we show that in peripheral blood cells a direct correlation exists between the presence of BCR/ABL and the phosphorylation status of CRKL. In Ph- peripheral blood cells, CRKL is present only in the nonphosphorylated form. In contrast, all BCR/ABL+ CML and acute lymphoblastic leukemia patient samples examined showed clear tyrosine-phosphorylation of CRKL. This result strongly suggests that CRKL is a biologically significant substrate for BCR/ABL and is likely to play a major role in the development of Ph+ leukemia.
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PMID:Tyrosine phosphorylation of CRKL in Philadelphia+ leukemia. 752 85

The Philadelphia chromosome (Ph1), detected in virtually all cases of chronic myelogenous leukemia (CML), is formed by a reciprocal translocation between chromosome 9 and 22 that fuses Bcr-encoded sequences upstream of exon 2 of c-Abl. This oncogene produces a fusion protein, p210bcr-abl, in which the Abl tyrosine kinase activity is elevated. Using anti-phosphotyrosine immunoblotting, we have compared the pattern of phosphotyrosine-containing proteins from freshly prepared neutrophils of patients in the stable phase of CML to normal controls. The only consistent difference was the presence of a 39-kDa tyrosine-phosphorylated protein in 18 out of 18 neutrophil samples from CML patients that was not seen in normal controls. This same protein, as assessed by two-dimensional anti-phosphotyrosine immunoblotting, was also present in cell lines expressing p210bcr-abl, including K562 cells. Using K562 cells as a source of protein, the 39-kDa protein was purified and identified by microsequencing as Crkl, an SH2/SH3 adaptor protein related to the crk oncogene of the avian sarcoma virus, CT10. A direct interaction between Crkl and Abl has also been shown using a yeast two-hybrid screen.
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PMID:Crkl is the major tyrosine-phosphorylated protein in neutrophils from patients with chronic myelogenous leukemia. 808 88

Chronic myelogenous leukemia is characterized by a specific chromosomal translocation, t(9;22), in which the ABL protooncogene and the BCR gene become juxtaposed. The chimeric BCR/ABL gene produces a P210 fusion protein with deregulated tyrosine kinase activity. We have recently isolated a complementary DNA, CRKL, which could code for an adaptor protein consisting of one SH2 and two SH3 domains and lacking any catalytic domain. In the current study, we show that CRKL is highly phosphorylated in the chronic myelogenous leukemia cell line K562 and that it is a substrate for the p210 BCR/ABL and p145 ABL kinases. BCR/ABL and ABL are coimmunoprecipitated with CRKL in vivo, demonstrating that relatively stable complexes are formed. In addition, the nucleotide exchange factor mSOS1 was found to be coimmunoprecipitated with CRKL. These findings establish a putative signal transduction pathway way through which BCR/ABL mediates its oncogenic activity.
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PMID:Cellular interactions of CRKL, and SH2-SH3 adaptor protein. 816 80

The CRKL adaptor protein was recently identified as a substrate for the BCR-ABL tyrosine kinase in patients with chronic myelogenous leukemia, but its function is unknown. Here we report that CRKL is phosphorylated when overexpressed, activates RAS and JUN kinase signaling pathways, and transforms fibroblasts in a RAS-dependent fashion. We examined the potential role of CRKL in BCR-ABL function by deleting the CRKL binding site in BCR-ABL. This mutant BCR-ABL protein shows a 50% reduction in fibroblast transforming activity. The GRB2 adaptor protein has previously been implicated in this pathway, presumably linking BCR-ABL to RAS. To address the relative roles of CRKL and GRB2 in this system, we compared BCR-ABL mutants with defects in binding to one or both adaptors. Whereas each single mutant showed a 2-3-fold loss in transforming activity, the double mutant showed a 15-fold reduction, suggesting that GRB2 and CRKL both contribute to BCR-ABL transformation. These results demonstrate the oncogenic potential of CRKL and provide functional evidence that CRKL plays a role in fibroblast transformation by BCR-ABL in conjunction with other adaptor proteins.
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PMID:The CRKL adaptor protein transforms fibroblasts and functions in transformation by the BCR-ABL oncogene. 879 23

Several studies indicate that a number of signal-transducing molecules involved in the proliferation, differentiation, and functional activation of normal hemopoietic cells may be constitutively activated in primary leukemic cells and play a role in the outcome or in the progression of these neoplastic disorders. In this study we show that the product of the proto-oncogene c-Cbl, whose function is still unknown, is constitutively tyrosine phosphorylated not only in cells from chronic myelogenous leukemias (CMLs) in the blast phase, but also in cells from acute myeloblastic leukemias (AMLs), Ph-negative acute T-lymphoblastic leukemias (T-ALLs), and Ph-negative pre-B lymphoblastic leukemias (pre-B ALL). Moreover, in acute leukemia cells, c-Cbl was not stably complexed with the tyrosine-phosphorylated adaptor protein CrkL. The analysis of Grb2/c-Cbl interaction demonstrated that, in both acute leukemia and CML blasts, c-Cbl was stably complexed with the N-terminal Src homology (SH) 3 domain of Grb2 and, in blasts from ALL patients, with the Grb2 SH2 domain. The analysis of c-Cbl subcellular distribution showed that in all cases of leukemia tested, as well as in growth factor-stimulated M-07e cells, c-Cbl was present in the cytosolic, in the membrane, and in the detergent-insoluble fractions. Finally, in polymorphonuclear neutrophils (PMNs) from CML patients, c-Cbl was found stably associated with the detergent-insoluble fraction, whereas in PMNs from normal donors, it was detected only in the cytosolic fraction. Our findings that c-Cbl is constitutively tyrosine phosphorylated and associated with the detergent-insoluble fraction in AML and ALL blasts and in PMNs from CML patients suggest that this event represents a common step in the neoplastic transformation of both myeloid and lymphoid progenitor cells.
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PMID:c-Cbl tyrosine phosphorylation and subcellular localization in human primary leukemic cells. 984 79

The SH2-SH3 domain-containing adaptor protein CRKL is the predominant tyrosine phosphorylated protein in chronic myelogenous leukemia (CML) neutrophils and BCR-ABL-expressing cell lines. The amino terminal CRKL SH3 domain binds directly to a proline-rich region in the C-terminus of BCR-ABL. BCR-ABL mutants with deletions of this region were constructed to assess biologic effects of eliminating the CRKL binding site. Yeast two-hybrid analysis and gel overlay assays show eradication of the direct interaction of CRKL with BCR-ABL in the proline deletion mutants. However, these BCR-ABL mutants transform myeloid cells to growth factor independence, and in these cells CRKL is tyrosine phosphorylated and associates with BCR-ABL. These findings suggest both direct and indirect interactions of CRKL with BCR-ABL. Thus, disruption of the direct interaction with BCR-ABL has not excluded a role for CRKL in BCR-ABL-mediated transformation.
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PMID:CRKL binding to BCR-ABL and BCR-ABL transformation. 1019 28

CrkL is an SH2 and SH3 domain-containing adaptor protein implicated in pathogenesis of chronic myelogenous leukemia. Here, we demonstrate that overexpression of CrkL enhances the erythropoietin (Epo)- or interleukin (IL)-3-induced activation of Elk-1 and the c-fos gene promoter activity in 32D/EpoR-Wt cells. Moreover, the Epo-induced activation of ERK1 and ERK2 was augmented and prolonged in cells inducibly overexpressing CrkL. A moderate increase in Epo-induced activation of JNK was also observed in cells overexpressing CrkL. Overexpression of C3G enhanced the Elk-1 activation synergistically with CrkL, while a C3G mutant lacking the guanine nucleotide exchange domain showed an inhibitory effect. Studies using a dominant negative Ha-Ras mutant demonstrated that the Elk-1 and ERK2 activation enhanced by CrkL and C3G was dependent on Ras. Consistent with this, the Epo-induced activation of Ras was augmented in cells inducibly overexpressing CrkL. Most importantly, a CrkL mutant defective in the SH2 or N-terminal SH3 domain showed an inhibitory effect on the Epo-induced activation of ERK2. These data indicate that the CrkL-C3G complex plays a role in Epo- or IL-3-induced, Ras-dependent activation of the Raf/ERK pathway leading to the activation of Elk-1 and the c-fos gene transcription.
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PMID:CrkL mediates Ras-dependent activation of the Raf/ERK pathway through the guanine nucleotide exchange factor C3G in hematopoietic cells stimulated with erythropoietin or interleukin-3. 1051 5

We have previously shown that the Jak2 tyrosine kinase is activated in Bcr-Abl positive cell lines and blood cells from CML blast crisis patients by tyrosine phosphorylation. We are searching for downstream targets of Jak2 in Bcr-Abl positive cells. It is known that c-Myc expression is required for the oncogenic effects of Bcr-Abl, and that over-expression of c-Myc complements the transformation defect of the Bcr-Abl SH2 deletion mutant. Moreover, the Bcr-Abl SH2 deletion mutant and an Abl C-terminal deletion mutant are deficient in activating c-Myc expression. Since the Jak2 binds to the C-terminal domain of Bcr-Abl and optimal Jak2 activation requires the SH2 domain, we tested whether Jak2 was involved in c-Myc protein induction by Bcr-Abl. We treated the 32Dp210 Bcr-Abl cells with the Jak2 specific tyrosine kinase inhibitor, AG490, and found that this drug, like the Abl tyrosine kinase inhibitor STI-571, inhibited c-Myc protein induction by Bcr-Abl. Treatment of 32Dp210 Bcr-Abl cells with AG490 also inhibited c-MYC RNA expression. It is also known that c-Myc protein is a labile protein that is increased in amounts in response to various growth factors by a mechanism not involving new Myc protein formation. Treatment of 32Dp210 Bcr-Abl cells with both the proteasome inhibitor MG132 and AG490 blocked the reduction of the c-Myc protein observed by AG490 alone. An adaptor protein SH2-Bbeta is involved in the enhancement of the tyrosine kinase activity of Jak2 following ligand/receptor interaction. In this regard we showed that the Jak2/Bcr-Abl complex contains SH2-Bbeta. Expression of the SH2-Bbeta R555E mutant in 32Dp210 Bcr-Abl cells reduced c-Myc expression about 40% compared to a vector control. Interestingly, we found the reduction of the c-Myc protein in several clones of dominant-negative (DN) Jak2 expressing K562 cells correlated very well with the reduction of tumor growth of these cells in nude mice as compared to vector transfected K562 cells. Both STI-571 and AG490 also induced apoptosis in 32Dp210 cells. Of interest, IL-3 containing medium reversed the STI-571 induced apoptosis of 32Dp210 cells but did not reverse the induction of apoptosis by AG490, which strongly supports the specificity of the inhibitory effects of AG490 on the Jak2 tyrosine kinase. In summary, our findings indicate that Jak2 mediates the increase in c-Myc expression that is induced by Bcr-Abl. Our results indicate that activated Jak2 not only mediates an increase of c-MYC RNA expression but also interferes with proteasome-dependent degradation of c-Myc protein.
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PMID:Jak2 is involved in c-Myc induction by Bcr-Abl. 1237 Aug 3

Chronic myelogenous leukaemia (CML) is one of the most intensively studied human malignancies. It has been the focus of major efforts to develop potent drugs for several decades, but until recently cure rates remained low. A breakthrough in CML therapy was very likely accomplished with the clinical introduction of STI-571 [imatinib mesylate; Gleevec (USA); Glivec (other countries)] in 2000/2001. Despite the hope that STI-571 has generated for many CML patients, development of resistance to this drug is already apparent in some cases, especially if the CML is diagnosed in its later stages. Therefore, novel drugs which can be used alone or in combination with STI-571 are highly desirable. This review briefly summarises the current understanding and therapy of CML and then discusses in more detail basic laboratory research that attempts to target Grb2, an adaptor protein known to directly interact with the Bcr portion of the Bcr-Abl fusion protein. Blocking the binding of Grb2 to the GDP-releasing protein SoS is well known to abrogate the activation of the GTPase Ras, a major driving force of the central mitogenic (MAP kinase) pathway. Additional Grb2 effector proteins may also contribute to the proliferation-inhibiting effects observed upon uncoupling Grb2 from its downstream signalling system. Since Grb2 is a known signal transducer for several major human oncogenes, this approach may have applications for a wider range of human cancers.
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PMID:High affinity molecules disrupting GRB2 protein complexes as a therapeutic strategy for chronic myelogenous leukaemia. 1268 10

Denbinobin (5-hydroxy-3,7-dimethoxy-1,4-phenanthraquinone) has been reported to exhibit anti-tumor and anti-inflammatory activity. Nevertheless, the anti-tumor mechanism of denbinobin remains unclear. In the present study, we evaluated the anticancer activity of denbinobin in human myelogenous K562 leukemia cells. In accordance with the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, we demonstrated that denbinobin inhibited cell viability in a concentration-dependent manner with an IC50 value of 1.84 microM. Cell cycle analysis illustrated that exposure of denbinobin caused a G2/M phase accumulation in a time-dependent manner. Tubulin polymerization in cells was apparently enhanced by denbinobin, implying that denbinobin might have a regulatory role in tubulin/microtubule. Furthermore, denbinobin significantly suppressed the expression of Bcr-Abl and phosphorylation of CrkL, a crucial tyrosine kinase and an adaptor protein in chronic myeloid leukemia, respectively. Denbinobin also markedly enhanced CD11b expression after a long-term treatment, suggesting that denbinobin might play a role in facilitating differentiation in K562 cells. In summary, we have demonstrated that denbinobin displays anticancer effects in K562 cells through the increase of levels of tubulin polymerization and deregulation of Bcr-Abl signaling. Our data demonstrate that denbinobin could be a potential anticancer lead compound for further development.
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PMID:Denbinobin-mediated anticancer effect in human K562 leukemia cells: role in tubulin polymerization and Bcr-Abl activity. 1586 44


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