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Over the past 10 years there has been a significant increase in the armamentarium of agents available for use in the treatment of advanced colorectal cancer (CRC). Among these new agents are two monoclonal antibodies targeting the epidermal growth factor receptor (EGFR): cetuximab, a mouse-human chimeric monoclonal antibody, and panitumumab, a fully human monoclonal antibody. Both are approved as monotherapy for the treatment of chemotherapy-refractory advanced CRC. Cetuximab is also indicated for use in combination with irinotecan. Here, we review 10 reports of phase II and III clinical studies of patients treated with panitumumab or cetuximab monotherapy. The clinical trials demonstrate similar efficacy profiles for advanced CRC patients treated with panitumumab and cetuximab monotherapy, with some differences in their adverse event profiles. In addition, the recent results of retrospective tumor KRAS gene mutational analyses in CRC patients treated with anti-EGFR monotherapy are reviewed. Data from the clinical trials reviewed here clearly demonstrate that anti-EGFR monotherapy is an effective treatment modality for patients with chemotherapy-refractory advanced CRC.
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PMID:Anti-epidermal growth factor receptor monotherapy in the treatment of metastatic colorectal cancer: where are we today? 1914 81

Cancer is a real challenge for modern medicine. Biologically, it is of a host origin and therefore its eradication appears not so easy as one could expect to do it. Cancer presents itself with many faces as if it would be Janus the deity. The basic knowledge on tumorigenesis at the level of evolutionary science is weak. Additionally, accumulating molecular data are still focused on experimental systems, but more important fact is to determine the molecular pathobiology that could have impact on improvement of control of malignant disease. Poland is among the countries with high cancer morbidity and mortality. Multidisciplinary approach to detect, control, and treat cancer diseases is the only way to get improved clinical results. Moreover, it is worth pointing out that individual considerations of every patient would offer clinical benefits. Biology of human tumors with the modem armament of molecular and chemical methods would be a help-hand to construct novel drugs. Making a list of crucial pathways worth blocking with their translation into clinical benefits appears to be a great step forward. Chemistry is a real partner to modem medicine due to a technical possibility to have impact on molecules (xenobiotics) that will finally become approved drugs. Combinatorial chemistry offers automated methods for pipeline organic synthesis a large number of chemicals that are further capable of undertaking investigation at a bed. Many chemicals have been used for more than ten years upon treating various cancer patients. New drugs have various origin , i.e., monoclonal antibodies (Herceptin, Erbitux, Avastin) or small molecules (Glivec, Tarceva, Sutent, Nexavar). We do hope that in the future many new drugs will be available for treatment of particular disease in relation to genetic characterization of individual patient's tumor. At the same time, we realize the great need for changes in the financial facets of modem individual treatment, and hoping not to hamper the development of new drugs due to the lack of financial solution how to make new and expensive drugs available to many patients.
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PMID:Molecular underpinnings of the targeted therapy for cancer. 1917 44

Overexpression of epidermal growth factor receptor (EGFR) and mutation of pten tumor suppressor gene in human cancer cells leads to activated EGFR downstream signaling including PI3-kinase/AKT (PI3K/AKT) and/or mitogen-activated protein kinases (RAS/RAF/MAPK) and have been linked to resistance to anti-EGFR targeted therapies. Cetuximab is a chimeric IgG1 monoclonal antibody that binds the EGFR with high specificity and have been developed as promising therapeutic anticancer treatments in several solid tumors, including colorectal and head and neck squamous cell carcinomas. Cetuximab activity is related to PI3K/AKT and RAS/RAF/MAPK signaling pathways functionality and its activity has been shown to be higher in wild-type KRAS tumors. To study the influence of PTEN expression on cell response to cetuximab, we used wild-type KRAS, PTEN-null, EGFR overexpressing PC3 prostate cancer cells. Reintroduction of PTEN significantly reduced the constitutive overexpression of phosphorylated-AKT (p-AKT) and downstream kinases (p-GSK3beta and p-P70S6 kinase) as well as phosphorylated-ERK1/2 (p-ERK1/2) and consequently significantly restored cetuximab-induced cell growth inhibition and apoptosis induction. Taken together, the results achieved in the present study show that PTEN controls the cellular response to cetuximab in KRAS wild-type prostate carcinoma PC3 cells through the regulation of AKT phosphorylation and restoration of the functionality of EGFR downstream signaling. Extrapolation of these findings to clinical situation, suggests that the assessment of EGFR downstream signaling functionality could be proposed as a diagnostic response predictive marker for anti-EGFR targeted therapies.
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PMID:PTEN expression controls cellular response to cetuximab by mediating PI3K/AKT and RAS/RAF/MAPK downstream signaling in KRAS wild-type, hormone refractory prostate cancer cells. 1921 33

Cetuximab, which blocks ligand binding to epidermal growth factor receptor (EGFR), is currently being studied as a novel treatment for non-small cell lung cancer (NSCLC). However, its mechanisms of action toward metastasis, and markers of drug sensitivity, have not been fully elucidated. This study was conducted to (a) determine the effect of Cetuximab on invasion and NSCLC-metastasis; (b) investigate urokinase-type plasminogen activator receptor (u-PAR), a major molecule promoting invasion and metastasis, as a target molecule; (c) delineate molecular mediators of Cetuximab-induced metastasis inhibition; and (d) identify biomarkers of drug sensitivity in NSCLC. Cetuximab treatment resulted in reduced growth and Matrigel invasion of H1395 and A549 NSCLC cell lines, in parallel with reduced u-PAR mRNA and protein. u-PAR down-regulation was brought about by suppressing the binding of JunD and c-Jun to u-PAR promoter motif -190/-171 in vivo, and an inhibition of MAP/ERK kinase signaling. Furthermore, Cetuximab inhibited NSCLC proliferation and metastasis to distant organs in vivo as indicated by the chicken embryo metastasis assay. Low E-cadherin and high u-PAR, but not EGFR, was associated with resistance to Cetuximab in seven NSCLC cell lines. Furthermore, siRNA knockdown of u-PAR led to a resensitization to Cetuximab. Moreover, low E-cadherin and high u-PAR was found in 63% of resected tumor tissues of NSCLC patients progressing under Cetuximab therapy. This is the first study to show u-PAR as a target and marker of sensitivity to Cetuximab, and to delineate novel mechanisms leading to metastasis suppression of NSCLC by Cetuximab.
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PMID:Cetuximab attenuates metastasis and u-PAR expression in non-small cell lung cancer: u-PAR and E-cadherin are novel biomarkers of cetuximab sensitivity. 1927 67

Colorectal carcinoma (CRC) represents a serious problem worldwide: in the Slovak republic are diagnosed about 2600 new CRC cases annually and its incidence is increasing. Colorectal cancer patients may succumb to the disease because of local recurrence or local formation of metastasis. Therefore, it is necessary to modulate therapeutic algorithm with new methods, leading to early diagnostic of CRC or changing the existing therapeutic procedures. Recent progresses have been made in understanding of EGFR pathway involved in CRC carcinogenesis, especially the role of Ras protein. Mutations in KRAS oncogene are frequently found in human cancers, particularly colorectal, pancreatic, billiary tract and lung tumors. The presence of the KRAS mutations in metastatic colorectal cancer patients correlates with lack of response to the certain epidemal growth factor receptor (EGFR) inhibitor therapies, such as Panitumumab and Cetuximab. Consequently, screening for KRAS mutations status may be used as a prognostic marker, because the CRC patients with KRAS positive tumors have a worse prognosis. The aim of our study was to establish the methods for rapid and sensitive detection of KRAS mutation status in formalin fixed paraffin embedded (FFPE) tissues DNA. We applied Real Time PCR analysis (TheraScreen KRAS Mutation Test Kit) and sequencing analysis (optimised for the analysis of FFPE tissues) to detect somatic mutations in codon 12 and 13 of KRAS gene. Both methods were used concurrently in the panel of DNA isolated from 25 colorectal FFPE tissues tumor. The positive or negative results from all 25 samples were identified by both methods independently. The KRAS mutations were presented in 8 of 25 patients (32%). Our results demonstrate that the Real Time PCR analysis can be used for detection of somatic KRAS mutations in FFPE clinical samples. However, we also recognize that the sequencing analysis of approximately 200bp amplicons may be used for mutations status screening, but with care of method sensitivity.
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PMID:Genetic analysis of KRAS mutation status in metastatic colorectal cancer patients. 1930 32

Glucocorticoids such as dexamethasone are widely used as comedication in the treatment of head and neck cancer, e.g., to improve appetite and decrease weight loss and fatigue in patients with advanced disease or as antiallergic and antiemetic prophylaxis during anti-EGFR therapy. However, the literature suggests that dexamethasone induces resistance to antineoplastic agents in many solid tumor models in vitro and in vivo. Since this phenomenon has never been investigated in head and neck cancer, the present study was conducted to investigate the effect of dexamethasone on the antiproliferative activity of cetuximab in vitro in squamous cell carcinoma of the head and neck (SCCHN) cell lines. The antiproliferative effect of the anti-EGFR agent cetuximab alone and in combination with increasing concentrations of dexamethasone was examined in eight SCCHN cell lines at three different time-points (24, 48 and 72 h). Cell growth inhibition and viability were measured quantitatively using WST and LDH assays. Absolute tumor cell numbers were determined by cell counting in a Rosenthal chamber. Cetuximab alone inhibited the growth of all eight SCCHN cell lines significantly (p=0.008). In some cases the addition of dexamethasone reduced the antiproliferative activity of cetuximab (p<or=0.038) but remained significant in all of the eight SCCHN cell lines compared with untreated controls (p<or=0.028) at each drug concentration and each time-point. In contrast to the results reported for other tumor models, in our study dexamethasone showed in the majority of the evaluated dexamethasone drug concentrations and time-points no inhibition of the cytotoxic activity of cetuximab. The reasons for these discrepant findings are unclear but may be related to the degree of tumor cell differentiation or proliferation rate. Thus, further studies are required to elucidate the molecular mechanisms underlying the interaction between dexamethasone and cetuximab in different tumors.
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PMID:Does dexamethasone inhibit anticancer activity of cetuximab in squamous cell carcinoma cell lines of the head and neck? 1951 20

Cetuximab, an anti-EGFR human/mouse chimeric antibody, has just been approved in Japan for patients with EGFR positive unresectable or recurrent colorectal cancer, as monotherapy or in combination with irinotecan. We reported two cases of unresectable or recurrent colorectal cancer effectively treated by cetuximab after the progression of the prior chemotherapy. Case 1: A51-year-old male suffered from sigmoid colon cancer with synchronous liver metastases. He received cetuximab plus irinotecan combination therapy in the third-line setting. Amonth after the initiation of the chemotherapy, abdominal CT showed tumor shrinkage of liver metastases. Case 2: A57-year-old female suffered from sigmoid colon cancer with metachronous liver, ovarian metastases, ascites and pleural effusion. Her performance status(PS)according to ECOG performance scale was 1, and she complained of dyspnea on exertion. She received cetuximab monotherapy in the fourth-line setting. Five weeks after initiation of chemotherapy, her chest, abdominal and pelvic CT showed tumor shrinkage of the liver metastases and the reduction of both ascites and pleural effusion, together with resolution of her dyspnea on exertion. Before cetuximab administration, we investigated KRAS status on cancer tissue previously resected in the above 2 cases, which showed KRAS wild-type. Cetuximab could be effective for KRAS wild-type colorectal cancer, as well as the previous reports from Western countries.
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PMID:[Two cases of KRAS wild-type unresectable or recurrent colorectal cancer effectively treated by cetuximab after progression of prior chemotherapy]. 1954 25

Overexpression of the epidermal growth factor (EGF) receptor (EGFR) in cancer cells correlates with tumor malignancy and poor prognosis for cancer patients. For this reason, the EGFR has become one of the main targets of anticancer therapies. Structural data obtained in the last few years have revealed the molecular mechanism for ligand-induced EGFR dimerization and subsequent signal transduction, and also how this signal is blocked by either monoclonal antibodies or small molecules. Nimotuzumab (also known as h-R3) is a humanized antibody that targets the EGFR and has been successful in the clinics. In this work, we report the crystal structure of the Fab fragment of Nimotuzumab, revealing some unique structural features in the heavy variable domain. Furthermore, competition assays show that Nimotuzumab binds to domain III of the extracellular region of the EGFR, within an area that overlaps with both the surface patch recognized by Cetuximab (another anti-EGFR antibody) and the binding site for EGF. A computer model of the Nimotuzumab-EGFR complex, constructed by docking and molecular dynamics simulations and supported by mutagenesis studies, unveils a novel mechanism of action, with Nimotuzumab blocking EGF binding while still allowing the receptor to adopt its active conformation, hence warranting a basal level of signaling.
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PMID:Nimotuzumab, an antitumor antibody that targets the epidermal growth factor receptor, blocks ligand binding while permitting the active receptor conformation. 1958 89

Cetuximab (Erbitux) has been highlighted for its anti-proliferative effects in solid tumors and it is currently used as an adjuvant modality with other anti-cancer treatments. Photodynamic therapy (PDT) is used widely in many specialties of medicine. This study evaluated the efficacy of a combination treatment of two modalities (Cetuximab, PDT) both in vivo and in vitro. The SNU-1041 cell line was used for both the in vitro and in vivo studies. The in vivo and in vitro experiments were each classified into four groups, control group, Cetuximab applied group, PDT applied group and combined modality group. A migration study was performed to determine the anti-migration effect of Cetuximab, and a MTT assay was performed to compare the anti-proliferative effect of the modalities in vitro. For the in vivo study, the cells were implanted into 5-week-old nude mice. The measured volume of the tumor for each group was compared as a function of time. In the migration study, the control group showed a longer migration length than the Cetuximab applied group. In the MTT assay, the combination modality group showed less survival than the uni-modality groups. The measured tumor size after treatment showed that the combination treatment was more effective than the single modalities. PDT and Cetuximab are treatment modalities that target different molecular pathways. A combination of these two treatment modalities was found to more effective than an individual treatment. However, further studies will be needed to determine the optimal dose of the photosensitizer and Cetuximab.
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PMID:Combination treatment of Cetuximab and photodynamic therapy in SNU-1041 squamous cancer cell line. 1972 46

Cetuximab is an anti-epidermal growth factor receptor monoclonal antibody used in the treatment of colorectal and head and neck cancers. Part of the interindividual differences in response may be explained by interindividual variability in pharmacokinetics. An assay measuring cetuximab serum concentrations is therefore needed. An enzyme-linked immunosorbent assay was developed using microtiter plates sensitized with a recombinant human epidermal growth factor receptor extracellular domain. Lower and upper limits of quantitation and limit of detection were determined. Eight standard calibrators (SCs) and 3 quality controls (QCs), that is, 0.75, 7.5, and 15 mg/L, were tested on 5 occasions on 1 day and on 5 occasions on different days. Trough and peak serum concentrations of cetuximab were measured in 15 patients with metastatic colorectal cancer and 1 patient with undetermined neoplasia undergoing cetuximab-based chemotherapy. Cetuximab concentrations were described using a 2-compartment population pharmacokinetic model. Imprecision and accuracy of SC and QC were < or = 20%, except for the 0 and 0.1 mg/L SC concentrations (< or = 20%). The limit of detection was 0.012 mg/L. Lower and upper limits of quantitation were 0.75 and 15 mg/L, respectively. A total number of 198 blood samples were available from the 16 patients. Median (range) trough and peak concentrations during the treatment were 49.6 (5.8-105.4) and 177.2 (97.5-235) mg/L, respectively. This method is rapid, accurate, and reproducible and may be useful for pharmacokinetic and pharmacokinetic-pharmacodynamic studies, as well as in therapeutic drug monitoring of cetuximab.
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PMID:An enzyme-linked immunosorbent assay for therapeutic drug monitoring of cetuximab. 1973 Feb 78

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