Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Elevated expression of multidrug efflux pumps such as P-glycoprotein (Pgp) have been associated with resistance to cytotoxic drugs used in the treatment of leukemias and other cancers. Imatinib mesylate (STI-571 or Gleevec) is a potent inhibitor of the BCR/ABL and c-KIT tyrosine kinases. It has displayed considerable efficacy in treatment of patients with Philadelphia-positive acute lymphoblastic leukemia and chronic myelogenous leukemia and those with gastrointestinal stromal tumors (GISTs). However, recently imatinib-resistant relapse has emerged as a significant problem. Although a major cause of resistance appears to be point mutation in the kinase domain of the target enzyme, the potential contribution of elevated multidrug efflux activity has not been systematically evaluated. The imatinib-sensitive human leukemic cell line K562, which is dependent on the activity of BCR/ABL for survival and growth, provides a convenient system for evaluating modulation of drug activity. By expressing Pgp at high levels in these cells, we have demonstrated that this pump provides minimal protection against cell growth inhibition and apoptosis induced by imatinib. In contrast, overexpression of Bcl-xL, which blocks apoptosis, resulted in partial protection against the drug. We conclude that Pgp up-regulation is not likely to be a significant contributor to imatinib resistance.
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PMID:Overexpression of P-glycoprotein in K562 cells does not confer resistance to the growth inhibitory effects of imatinib (STI571) in vitro. 1288 21

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors. The molecular etiology is the result of mutations in the c-Kit gene. The mutant c-Kit proteins, which are activated without a stem cell factor, contribute to the tumor development. STI571 selectively inhibits c-Kit, BCR-ABL, and PDGFR tyrosine kinases. Based on this potential to inhibit critical c-Kit function in GISTs, case studies have reported effective outcomes following treatment with STI571. This case report describes a highly effective use of STI571 in a 54-year-old woman with multiple liver metastases from a GIST originating in the duodenum.
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PMID:Effect of a tyrosine kinase inhibitor STI571 in a patient with hepatic metastases from a duodenal gastrointestinal stromal tumor. 1289 63

Gastrointestinal stromal tumors (GIST) are composed of KIT-positive mesenchymal-origin spindle- or polygonal-shaped tumor cells in the gastrointestinal tract without immunoreactivity for desmin and S-100. The gain-of-function mutations in the c-kit gene (90%) or platelet-derived growth factor receptor alpha (PDGF-R alpha) gene (5%) are now considered to be causative for GIST. STI571 (Glivec), a molecule designed to selectively inhibit Bcr-Abl, KIT, and PDGF-R activity, shows high response rate and efficacy for non-resectable and/or relapsed GIST (PR 60%). Its serious adverse effects (more than Grade 3) were infrequent, thus, tolerability and safety are good. Glivec is the first successful case of molecular target therapy for solid tumors. However, new resistance against this new generation of drug is going to appear and becomes an urgent problem.
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PMID:[Target-based therapy against gastrointestinal stromal tumors--from molecular diagnosis to molecular target therapy]. 1293 60

Gastrointestinal stromal tumors (GISTs), defined by the presence of constitutively activated KIT, are the most common gastrointestinal mesenchymal malignancies. This observation has been successfully exploited in clinical trials of Gleevec (also known as imatinib mesylate, STI-571) for patients with unresectable and/or metastatic GISTs. The biological mechanisms of Gleevec as well as its downstream molecular effects are generally unknown. We used a DNA microarray-based approach to identify gene expression patterns and signaling pathways that were altered in response to Gleevec in GIST cells. We identified a total of 148 genes or expressed sequence tags (of 10,367) that were differentially regulated; 7 known genes displayed a durable response after treatment. The significantly down-regulated genes were SPRY4A, FZD8, PDE2A, RTP801, FLJ20898, and ARHGEF2. The only up-regulated gene was MAFbx. On a functional level, we demonstrated that imatinib inhibited phosphorylation of KIT, AKT, and extracellular signal-regulated kinase 1/2 without affecting the total level of these proteins and that differential expression of these response genes involved activation of mitogen-activated protein kinase-dependent and -independent pathways. In an attempt to correlate these in vitro findings to clinical data, we examined GIST needle biopsy specimens taken from patients before and after Gleevec administration according to the CSTI571-B2222 Phase II trial and demonstrated that expression levels of the two gene transcripts evaluated correlated well with clinical response. This study emphasizes the potential value of an in vitro cell model to investigate GIST response to imatinib in vivo, for the purpose of identifying important genetic markers of clinical response, mechanisms of drug action, and possible therapeutic targets.
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PMID:Response markers and the molecular mechanisms of action of Gleevec in gastrointestinal stromal tumors. 2207 11

Seminal studies with STI-571 and Herceptin in chronic myeloid leukemia, gastrointestinal stromal tumors, and breast cancer have clearly demonstrated that blockade of pathogenic tyrosine kinases can alter the natural history of appropriately selected human tumors. On the other hand, trials with EGF receptor inhibitors in unselected populations have shown anywhere from modest to no clinical activity. I will contrast below aspects in the development of inhibitors of Abl, c-Kit, HER2/neu (erbB2), and EGFR, highlight successes and pitfalls in this field, and propose some approaches for the future development of tyrosine kinase inhibitors in human cancer.
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PMID:Inhibiting tyrosine kinases: successes and limitations. 1450 84

Topics discussed here include PTEN mutations and colonic polyps; WNT signaling, APC, beta-catenin, and gastrointestinal neoplasms; mismatch-repair genes (MLH1, MSH2, PMS1, MSH6) and hereditary nonpolyposis colorectal cancer; MYH mutations and autosomal recessive colorectal tumors; STK11 mutations and Peutz-Jeghers syndrome; TGFbeta and gastrointestinal cancer; BMPR1A mutations and juvenile polyposis; FGF/FGFR alterations in gastrointestinal neoplasms; PTCH mutations and gastrointestinal neoplasms; RUNX3 expression and gastric cancer; role of mucins in gastric carcinogenesis; KIT, PDGFRalpha, and gastrointestinal stromal tumors; intestinal neurofibromatosis; and gastrointestinal tumors in other disorders.
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PMID:Molecular dimensions of gastrointestinal tumors: some thoughts for digestion. 1451 68

Mutations in the proto-oncogene c-kit cause constitutive kinase activity of its product, KIT protein, and are associated with human mastocytosis and gastrointestinal stromal tumors (GISTs). Although currently available tyrosine kinase inhibitors are effective in the treatment of GISTs, there has been limited success in the treatment of mastocytosis. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), a benzoquinoid ansamycin antibiotic, which binds to heat shock protein 90 (hsp90) causes destabilization of various hsp90-dependent kinases important in oncogenesis. Treatment with 17-AAG of the mast cell line HMC-1.2, harboring the Asp816Val and Val560Gly KIT mutations, and the cell line HMC-1.1, harboring a single Val560Gly mutation, causes both the level and activity of KIT and downstream signaling molecules AKT and STAT3 to be down-regulated following drug exposure. These data were validated using Cos-7 cells transfected with wild-type and mutated KIT. 17-AAG promotes cell death of both HMC mast cell lines. In addition, neoplastic mast cells isolated from patients with mastocytosis, incubated with 17-AAG ex vivo, are selectively sensitive to the drug compared to the mononuclear fraction. These data provide compelling evidence that 17-AAG may be effective in the treatment of c-kit-related diseases including mastocytosis, GISTs, mast cell leukemia, subtypes of acute myelogenous leukemia, and testicular cancer.
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PMID:17-Allylamino-17-demethoxygeldanamycin (17-AAG) is effective in down-regulating mutated, constitutively activated KIT protein in human mast cells. 1455 Nov 38

Treatment of advanced renal cancer has made little progress in the past 30 yr. Most clinical efforts have incorporated cytokine-based therapy. The presumption has been that the cytokines may trigger a host immune response against the renal cancer. Only IFN-alpha and high-dose IL-2 seemed to have positive effects on patient outcomes. IFN has prolonged the lives of patients by a few months, and high-dose IL-2 is capable of inducing very prolonged remissions (>5 yr) for a small number of patients. Nephrectomy in the presence of metastatic disease has been established as an effective procedure for select patients, providing palliation and prolonging survival. Finally, enthusiasm has focused on the use of nonmyeloablative allogeneic stem cell transplantation and donor leukocyte infusion for the induction of graft versus tumor effects. Early results are both provocative and promising. A number of agents that target the critical gene products downstream from pVHL and hypoxia-inducible factor-1, such as vascular endothelial growth factor, PDGF, EGF receptor, and TGF-alpha, have recently become available. The new agents are capable of inhibiting specific cellular targets, and the biologic characteristics of clear cell carcinoma of the kidney support their application. If the correct targets are carefully selected for inhibition in tumors in which the targets are present (clear cell histologic features and loss of VHL expression), then results should resemble those others have observed with targeted therapy, such as the use of STI-571 (Gleevec; Novartis Pharmaceuticals, East Hanover, NJ) for treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors or anti-HER2/neu (Herceptin; Genentech, South San Francisco, CA) for treatment of breast cancer.
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PMID:Targeting of the VHL-hypoxia-inducible factor-hypoxia-induced gene pathway for renal cell carcinoma therapy. 1456 78

Modulation of the signaling pathways that are aberrant in cancer cells has the potential to provide an effective nontoxic approach to patient management in a broad range of cancers. This quest has taken a major leap forward with the demonstration that STI-571 (imatinib mesylate) induces clinical and molecular remissions in the majority of patients with interferon-refractory chronic myelogenous leukemia and gastrointestinal stromal tumors through inhibition of the Bcr/Abl fusion protein required for the initiation and progression of chronic myelogenous leukemia and inhibition of a mutant, activated c-kit present in gastrointestinal stromal tumors. Support for the concept of targeting products of fusion genes found in specific cancers was first provided by the efficacy of all-trans retinoic acid in acute promyelocytic leukemia where the RARalpha all-trans retinoic acid target is the target of multiple different chromosomal rearrangements. In breast cancer, trastuzumab, which alters the function of the HER2 proto-oncogene overexpressed in a portion of breast cancers, provides an additional example of targeting specific molecular aberrations present in cancer cells. Although the target for these signal transduction modulators is functional in normal cells, acceptable therapeutic indices sufficient to prevent tumor growth without unacceptable toxicities have been observed. Whether STI-571 and other signal transduction modulators also target the stroma, and specifically the neovasculature, in addition to the tumor remains an open question. The presence of the target in the cancer cells or in the surrounding stroma appears to be required but not sufficient for the action of molecular therapeutics. Thus, linking molecular diagnostics to identify patients where the target is amplified or activated and driving the pathophysiology of the patients' tumor to effective molecular therapeutics will be necessary to translate these concepts into approaches that will alter the outcome for breast cancer patients. This review will focus on the phosphatidylinositol 3-kinase pathway and novel molecules targeting this pathway to illustrate the questions and challenges underlying the implementation of molecular therapeutics in breast cancer.
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PMID:Linking molecular diagnostics to molecular therapeutics: targeting the PI3K pathway in breast cancer. 1461 30

Scientific knowledge on gastrointestinal stromal tumors (GIST) has dramatically progressed over the last 10 years. During this period, this distinct disease entity was identified under various acronyms (GIST remaining the most commonly used), the molecular basis of disease transformation (i.e. activating c-KIT mutations) was identified in sporadic and familial cases, and finally GIST was identified as the sarcoma subtype most resistant to chemotherapy in both retrospective and prospective studies. Until 2000, surgery was the only reported efficient treatment modality in this disease, both in the localized and metastatic phase. In 2000, the first GIST patient received Glivec, and in the last 3 years, more than 2,000 patients were included in prospective trials evaluating this compound in advanced phases. Disease control is initially achieved in 80-90% of patients, with only 10-15% of patients dying in the first year following the occurrence of metastases, while the median overall survival was less than 12 months with previous treatment options. However, there still remain several questions regarding long-term outcome, tolerance, cure, dose of Glivec, and alternative treatment upon relapse of GIST in patients receiving Glivec. Additional follow-up is necessary. Glivec treatment of GIST is the first example of an efficient targeted treatment in a solid tumor.
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PMID:Gastrointestinal stromal tumors: biology and treatment. 1465 91


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