Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006826 (cancer)
 1,092,456 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The remarkable responses observed with imatinib (Gleevec) in the therapy of CML led many scientists to think that drug resistance, long recognized as a problem with "cytotoxic" agents, would soon become a thing of the past. But then reality set in. We learned that imatinib, a wonderful drug by any measure, was also susceptible to the development of resistance, as was gefitinib (Iressa), and then erlotinib (Tarceva). This evidence on resistance to "novel agents" together with new data on the complexity of cancer, the rapidly evolving story of microRNAs and their diverse roles, as well as evidence of the importance of epigenetic changes have allowed us to refine our models of drug resistance and how cells acquire these phenotypes. In this overview I will look at examples of how drug resistance develops including older and more recent data on the role of mutations, translocations, deletions, and amplification. The role of epigenetic changes and microRNAs will be discussed, as examples of different mechanisms by which a cell achieves the same end. Recurrent themes that have emerged will be underscored as we seek to understand how drug resistance occurs.
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PMID:Multiple paths to a drug resistance phenotype: mutations, translocations, deletions and amplification of coding genes or promoter regions, epigenetic changes and microRNAs. 1735 Mar 22

Survival for patients with pancreatic cancer remains abysmal. Standard treatment for resected and locally advanced disease usually consists of 5-fluorouracil (5-FU, either bolus or continuous infusion) and external beam radiation. However, recent studies have shown the role of gemcitabine either used alone or incorporated with 5-FU and external beam radiation in this setting. Gemcitabine and erlotinib (Tarceva) are currently the only standard chemotherapeutic agents approved by FDA for the treatment of advanced pancreatic cancer. Combination chemotherapy trials incorporating gemcitabine with other agents such as 5-FU, oxaliplatin, or capecitabine generally show improved outcomes in objective response rates but with little or no improvement in survival in phase III trials. In this article, the author summarizes the key studies in pancreatic cancer presented at the 2007 Gastrointestinal Cancers Symposium (Orlando, FL, USA; January, 2007). The studies discussed here include preliminary results of the Cancer and Leukemia Group B (CALGB) phase III trial of gemcitabine plus bevacizumab and activity of other targeted agents including sorafenib, cetuximab, retrospective and population-based studies evaluating the role of chemo-radiotherapy and radiotherapy, an analysis of 3,306 patients from the Surveillance, Epidemiology and End Results (SEER) database evaluating the predictive role of lymph nodes in survival following pancreatectomy and the assessment of novel agents, such as Genexol-PM and S-1.
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PMID:Pancreatic cancer: are we moving forward yet? Highlights from the Gastrointestinal Cancers Symposium. Orlando, FL, USA. January 20th, 2007. 1735 39

Abnormal expression and signaling of ErbB receptors has been implicated in multiple epithelial malignancies, including pancreatic cancer. Erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), has been recently approved for pancreatic cancer treatment, but there are no reliable predictors of patient response. Expression of additional ErbB receptors seems to influence tumor response to EGFR-targeted therapy. We analyzed the influence of ErbB3 expression on pancreatic cancer cell response to erlotinib treatment. Proliferation assays of five human pancreatic cancer cell lines were performed following treatment with erlotinib. Expression and phosphorylation profiles of ErbB receptors and downstream adaptor protein (Akt, ERK1/2, STAT3, mTOR) were evaluated following stimulation with EGF or neuregulin-beta. The formation of EGFR homodimers and EGFR-ErbB3 heterodimers, necessary to enable ErbB3 downstream signaling, was demonstrated by chemical cross-linking assays. The effects of RNA inhibition of ErbB3 on sensitivity to erlotinib treatment were evaluated in AsPC-1 pancreatic cancer cells. Erlotinib inhibited Akt phosphorylation and proliferation of all the ErbB3-expressing cell lines but did not affect mTOR activation. Cross-linking studies confirmed the presence of EGFR-ErbB3 heterodimers in pancreatic cancer cells. Only the ErbB3-deficient MIA PaCa-2 cells displayed persistent Akt activation and ongoing proliferation in spite of erlotinib treatment. siRNA-mediated inhibition of ErbB3 expression in AsPC-1 cells resulted in acquired resistance to erlotinib treatment. Pancreatic cancer cells which lack ErbB3 do not display activation of the ErbB3-PI3K-Akt cascade induced by EGFR/ErbB3 heterodimers and become less critically dependent on EGFR signaling and therefore resistant to erlotinib. Pancreatic cancer expression of ErbB3 may be useful for EGFR-targeted therapy patient selection.
Cancer Biol Ther 2007 Apr
PMID:ErbB3 expression and dimerization with EGFR influence pancreatic cancer cell sensitivity to erlotinib. 1745 47

Epidermal growth factor receptor (EGFR) is overexpressed by several solid tumors, including pancreatic cancer, and has become an important target for novel anticancer pharmacotherapy. Erlotinib (Tarceva, OSI-774) is an orally available small-molecule inhibitor of the EGFR tyrosine kinase. The addition of erlotinib to gemcitabine has been shown to prolong survival of patients treated for advanced pancreatic cancer in the National Cancer Institute of Canada PA.3 trial. This survival advantage is small yet noteworthy, in that numerous gemcitabine-containing combinations have failed to show a statistically significant survival advantage over gemcitabine alone. The most frequent toxicities associated with the addition of erlotinib are diarrhea and rash. Erlotinib-induced rash appears to be predictive of outcome. Further clinical studies of erlotinib in the treatment of pancreatic cancer are ongoing.
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PMID:Erlotinib: success of a molecularly targeted agent for the treatment of advanced pancreatic cancer. 1754 18

Erlotinib (Tarceva), an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has clinical activity in advanced lung cancer, but disease that initially responds to erlotinib eventually progresses. The mechanism of this acquired resistance is unclear. We established two erlotinib-resistant pools of A-431 cells, a well-characterized epidermoid cancer cell line that constitutively overexpresses EGFR and is sensitive to erlotinib, by continuous exposure to erlotinib over a 6-month period. The extent of EGFR gene amplification or mutation of the EGFR tyrosine kinase domain was not altered in the resistant cells. Intracellular erlotinib concentrations, determined by liquid chromatography-tandem mass spectrometry, were almost the same in all three cell lines. Immunoprecipitation with EGFR antibody followed by detection with phosphotyrosine antibody revealed that erlotinib effectively reduced EGFR phosphorylation in both parental cells and resistant cells. Erlotinib induced mutated in multiple advanced cancers 1/phosphatase and tensin homologue (MMAC1/PTEN) and suppressed phosphorylated Akt (Ser(473)) but not in the erlotinib-resistant cells. Overexpression of MMAC1/PTEN by transfection with Ad.MMAC1/PTEN or by pharmacologic suppression of Akt activity restored erlotinib sensitivity in both resistant pools. Further, transfection of parental A-431 cells with constitutively active Akt was sufficient to cause resistance to erlotinib. We propose that acquired erlotinib resistance associated with MMAC1/PTEN down-regulation and Akt activation could be overcome by inhibitors of signaling through the phosphatidylinositol 3-kinase pathway.
Cancer Res 2007 Jun 15
PMID:Acquired resistance to erlotinib in A-431 epidermoid cancer cells requires down-regulation of MMAC1/PTEN and up-regulation of phosphorylated Akt. 1757 45

The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase (TK) receptor that is frequently expressed in many epithelial tumors. The signaling pathways of EGFR is involved in cancer cell proliferation, apoptosis, angiogenesis, invasions and metastasis. The EGFR was the first receptor to be proposed for cancer therapy and two EGFR-targeted pharmacological approaches have been successfully developed: monoclonal antibodies and small-molecule inhibitor of the EGFR TK enzymatic activity. Erlotinib is a quinazoline derivative that selectively and reversibly inhibits the TK activity of EGFR. Erlotinib, on the basis of the results of a large randomized phase III clinical trial (BR21) in which show a survival benefit versus placebo-treated patients, received regular approval for the treatment of advanced non-small-cell lung cancer (NSCLC) patients after failure a platinum-containing chemotherapy. Erlotinib was recently approved in combination with gemcitabine chemotherapy for the treatment of advanced pancreatic cancer, and continues to be investigated in a number of tumor types. Furthermore, it has been investigated the role of factors that would predict the efficacy of erlotinib treatment, including anatomoclinical, pathologic and molecular features. This review will focus on the clinical results available with erlotinib in the treatment of NSCLC, pancreatic, head and neck and other tumor types.
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PMID:Erlotinib in cancer treatment. 1759 29

Pancreatic cancer represents the fourth leading cause of cancer-related mortality in the United States. The vast majority of patients are diagnosed at advanced stages of the disease, at which time gemcitabine-based chemotherapy is typically offered as the standard of care. However, as investigators have arrived at a greater understanding of pancreatic tumor biology, newer therapeutic agents that "target" specific pathways or molecules governing the growth, spread, and maintenance of tumor cells have gained considerable interest. Erlotinib, an orally bioavailable small molecule inhibitor of the epidermal growth factor receptor, is the first of these targeted compounds to be approved for use in combination with gemcitabine for patients with advanced pancreatic cancer. Other targeted agents, including monoclonal antibodies and small molecule inhibitors aimed at a variety of targets, also have been extensively evaluated, with limited success to date. A newer strategy worth pursuing involves tailoring an individual patient's therapy according to the molecular characteristics of both host and tumor, as has shown promise in other solid tumor types.
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PMID:Future strategies for targeted therapies and tailored patient management in pancreatic cancer. 1767 64

We have shown previously that blockade of epidermal growth factor receptor (EGFR) cooperates with a pan-selective inhibitor of phosphoinositide-3-kinase (PI3K) in EGFR-driven glioma. In this communication, we tested EGFR-driven glioma differing in PTEN status, treating with the EGFR inhibitor erlotinib and a novel dual inhibitor of PI3Kalpha and mTOR (PI-103). Erlotinib blocked proliferation only in PTEN(wt) cells expressing EGFR. Although erlotinib monotherapy showed little effect in PTEN(mt) glioma, PI-103 greatly augmented the antiproliferative efficacy of erlotinib in this setting. To address the importance of PI3K blockade, we showed in PTEN(mt) glioma that combining PI-103 and erlotinib was superior to either monotherapy or to therapy combining erlotinib with either rapamycin (an inhibitor of mTOR) or PIK-90 (an inhibitor of PI3Kalpha). These experiments show that a dual inhibitor of PI3Kalpha and mTOR augments the activity of EGFR blockade, offering a mechanistic rationale for targeting EGFR, PI3Kalpha, and mTOR in the treatment of EGFR-driven, PTEN-mutant glioma.
Cancer Res 2007 Sep 01
PMID:A dual phosphoinositide-3-kinase alpha/mTOR inhibitor cooperates with blockade of epidermal growth factor receptor in PTEN-mutant glioma. 1780 2

New cancer-specific therapies are based on specific molecular alterations of malignant tumors which are targeted by small inhibitory molecules or specific antibodies. During the development of these agents potential molecular targets are characterized for their expression and importance for pathogenesis and clinical course of the disease. Frequently the assumption is made that the degree of expression of the target protein or the molecular alteration of the target gene allows a prediction if a certain patient will profit from the therapy against this specific protein or not. The first example was that breast cancer patients with overexpression and/or amplification of Her-2 respond to a Her-2-specific antibody (Herceptin) therapy. The expression or activation of the Epidermal Growth Factor Receptor (EGFR, Her-1) are altered in many epithelial tumours and clinical studies indicate that they have important roles in tumor aetiology and progression. Several EGFR-specific monoclonal antibodies and specific tyrosine kinase inhibitors were developed in the last years. Cetuximab is approved for the treatment of metastatic colorectal cancer and advanced squamous cell carcinoma of the head and neck and is investigated in numerous trials for other tumors. The expression of EGFR in the tumor was a prerequisite for the therapy in the first trials, giving the pathologist a central role in treatment decision. However, recent data clearly demonstrate that the degree of EGFR expression does not correlate with therapy response. Therefore a therapy should be not denied to a individual patient solely because of lack of EGFR expression in the tumor. Tyrosine kinase inhibitors (e. g. Gefitinib, Erlotinib) are effective in the treatment of non small cell lung cancer and also investigated in ongoing trials in many cancer types. The correlation of therapy response with both specific molecular alterations (EGFR tyrosine kinase domain mutations) and clinicopathological features (Asian ethnicity, women, non-smokers, bronchioloalveolar differentation) is a good example of the potential role of predictive molecular pathology in the future.
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PMID:[Role of predictive pathology in oncology--example of new therapies targeting EGFR]. 1786 89

Protein kinases are involved in many diseases like cancer, inflammation, cardiovascular disease, and diabetes. They have become attractive target classes for drug development, making kinase inhibitors as important class of therapeutics. The success of small-molecule ATP-competitive kinase inhibitors such as Gleevec, Iressa, and Tarceva has attracted much attention in the recent past. Kinases make use of ATP for phosphorylation of a specific residue(s) on their protein substrates. More than 400 X-ray structures of about 70 different kinases are publicly available. These structures provide insights into selectivity and mechanisms of inhibition. However, prediction of binding specificity of kinase inhibitors based on structural information alone appears to be insufficient. Here, we will review these observations to gain insights into the rules that govern protein kinase inhibitor selectivity.
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PMID:Protein kinase inhibitors: structural insights into selectivity. 1789 21


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