Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0009402 (colorectal cancer)
 53,228 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance to antiepidermal growth factor (EGFR) strategies is an emerging clinical problem. Using human colorectal cancer (CRC) cells, we evaluated the involvement of the insulin receptor isoform-A (InsR-A) in de novo resistance to gefitinib, an EGFR tyrosine kinase inhibitor. Challenging the EGFR positive LoVo cells with gefitinib (1 microM) resulted in a small ( approximately 18%) inhibition of cell growth and although a modest reduction in phospho (p)EGFR Tyr845 was seen, pEGFR at residues -Tyr1068 and -Tyr1173 were unchanged. LoVo cells produced unprocessed pro-IGF-1R protein, substantial levels of IGF-II mRNA and mature InsR protein, consisting mainly of the InsR-A isoform. Insulin and IGF-II promoted cell growth and pEGFR Tyr845, Tyr1068 and Tyr1173 activity and conversely, the insulin-like growth factor-1 receptor (IGF-1R)/InsR inhibitor ABDP (1 muM) inhibited growth and reduced pEGFR activity at all three tyrosine residues. pInsR and pAkt levels were increased after gefitinib treatment. Blocking of pInsR with ABDP enabled gefitinib to markedly reduce pEGFR Tyr845, Tyr1068 and Tyr1173. Short-term gefitinib/ABDP dual treatment was more effective than either agent alone and chronic exposure to this combination resulted in total cell loss after 9 weeks, preventing acquisition of resistance to ABDP. LoVo cells with acquired resistance to ABDP were acutely sensitive to gefitinib. We concluded that InsR-A reduces sensitivity to gefitinib in LoVo CRC cells, thus its co-targeting alongside EGFR can improve the anti-tumour effect of gefitinib.
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PMID:Inhibition of insulin receptor isoform-A signalling restores sensitivity to gefitinib in previously de novo resistant colon cancer cells. 1681 46

Angiogenesis plays a central role in the process of tumor growth and metastatic dissemination. The vascular endothelial growth factor (VEGF) family of peptide growth factors and receptors are key regulators of this process. Agents directed either against VEGF or VEGF receptors (VEGFRs) have been developed. The tyrosine kinase inhibitors of VEGFRs are low-molecular-weight, ATP-mimetic proteins that bind to the ATP-binding catalytic site of the tyrosine kinase domain of VEG-FRs, resulting in blockade of intracellular signaling. Several of these agents are currently in different phases of clinical development. Large randomized phase III trials have demonstrated the efficacy of sunitinib and sorafenib in the treatment of patients affected by gastrointestinal stromal tumors and renal cancer refractory to standard therapies, respectively. Positive results also have been reported with the combination of ZD6474 and chemotherapy in previously treated non-small cell lung cancer patients. For other agents, such as vatalanib, contrasting outcomes in metastatic colorectal cancer patients have been reported: the final results of these trials are expected in 2006. However, several key questions remain to be addressed, regarding the choice of an adequate dose or schedule, the presence of "off-target" effects, the safety of long-term administration, and the research of new clinical end points or methodological approaches for the optimal clinical development of these agents.
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PMID:Tyrosine kinase inhibitors of vascular endothelial growth factor receptors in clinical trials: current status and future directions. 1688 Feb 34

The anti-epidermal growth factor receptor (EGFR) monoclonal antibody cetuximab has been approved for the treatment of patients with metastatic colorectal cancer. However, there is currently no reliable marker for response to therapy with the EGFR inhibitors. In this study, we investigated the sensitivity of 10 human colorectal tumor cell lines (DiFi, CCL218, CCL221, CCL225, CCL227, CCL228, CCL231, CCL235, CCL244, and HCT-116) to treatment with our anti-EGFR monoclonal antibody, ICR62, and/or the EGFR tyrosine kinase inhibitor, gefitinib. Of the cells examined, only DiFi contained high levels of constitutively active EGFR and were highly sensitive to treatment with both ICR62 (IC(50) = 0.52 nmol/L) and gefitinib (IC(50) = 27.5 nmol/L). In contrast, the growth of other tumor cell lines, which contained low levels of the EGFR, HER-2, and pAkt but comparable or even higher basal levels of phosphorylated mitogen-activated protein kinase (pMAPK), were relatively resistant to treatment with both inhibitors. Both ICR62 and gefitinib induced EGFR down-regulation, reduced the basal levels of pEGFR at five known tyrosine residues, pMAPK, and pAkt, and increased the sub-G(1) population in DiFi cells. However, treatment with a combination of ICR62 and gefitinib neither sensitized colorectal tumor cells that were insensitive to treatment with the single agent nor enhanced the growth-inhibitory effect of the single agent in DiFi cells. These results indicate that basal levels of pMAPK and pAkt are not good indicators of response to the EGFR inhibitors in colorectal cancer cells and dual targeting of the EGFR by a combination of ICR62 and gefitinib is not superior to treatment with a single agent.
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PMID:Responses of human colorectal tumor cells to treatment with the anti-epidermal growth factor receptor monoclonal antibody ICR62 used alone and in combination with the EGFR tyrosine kinase inhibitor gefitinib. 1688 73

To date, clinical studies combining the new generation of targeted therapies and chemotherapy have had mixed results. Preclinical studies can be used to identify potential antagonism/synergy between certain agents, with the potential to predict the most efficacious combinations for further investigation in the clinical setting. In this study, we investigated the sequence-dependent interactions of ZD6474 with oxaliplatin in two human colon cell lines in vitro. We evaluated the in vitro antitumor activity of ZD6474, an inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and RET tyrosine kinase activity, and oxaliplatin using three combination schedules: ZD6474 before oxaliplatin, oxaliplatin before ZD6474, and concurrent exposure. Cell proliferation studies showed that treatment with oxaliplatin followed by ZD6474 was highly synergistic, whereas the reverse sequence was clearly antagonistic as was concurrent exposure. Oxaliplatin induced a G(2)-M arrest, which was antagonized if the cells were previously or concurrently treated with ZD6474. ZD6474 enhanced oxaliplatin-induced apoptosis but only when added after oxaliplatin. The sequence-dependent antitumor effects appeared, in part, to be based on modulation of compensatory prosurvival pathways. Thus, expression of total and active phosphorylated EGFR, as well as AKT and extracellular signal-regulated kinase, was markedly increased by oxaliplatin. This increase was blocked by subsequent treatment with ZD6474. Furthermore, the synergistic sequence resulted in reduced expression of insulin-like growth factor-I receptor and a marked reduction in secretion of vascular endothelial growth factor protein. ZD6474 in combination with oxaliplatin has synergistic antiproliferative properties in human colorectal cancer cell lines in vitro when oxaliplatin is administered before ZD6474.
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PMID:Sequence-dependent inhibition of human colon cancer cell growth and of prosurvival pathways by oxaliplatin in combination with ZD6474 (Zactima), an inhibitor of VEGFR and EGFR tyrosine kinases. 1689 75

Novel therapeutic agents that target the epidermal growth factor receptor (EGFR) constitute an important addition to the therapeutic armamentarium for the treatment of metastatic disease. EGFR-targeted agents currently approved by the U.S. Food and Drug Administration include cetuximab, a monoclonal antibody for the treatment of colorectal cancer; and the small-molecule EGFR tyrosine kinase inhibitor (TKI) erlotinib for the treatment of nonsmall cell lung cancer (NSCLC) and pancreatic cancer. Approval of the TKI gefitinib for NSCLC recently was withdrawn. Although both classes of anti-EGFR agents target the same receptor, substantial distinctions regarding their mechanism significantly affect dosing requirements, toxicity profiles, and their use as combination agents.
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PMID:Clinical implications of the mechanism of epidermal growth factor receptor inhibitors. 1690 23

We recently showed by DNA microarray analysis that vascular endothelial growth factor (VEGF) receptor (VEGFR) is expressed in HCT8/S11 human colon cancer cells, suggesting that several angiogenic factors may target colon cancer cells themselves. In this study, transcripts encoding the VEGF-165 and semaphorin 3A (Sema3A) receptors and coreceptors Flt-1, KDR/Flk-1, plexin A1, and neuropilins NP-1 and NP-2 were identified by reverse transcription-PCR in the human colon cancer cell lines HCT8/S11, HT29, HCT116, and PCmsrc. Collagen invasion induced by VEGF-165 and Sema3A in HCT8/S11 cells (EC(50), 0.4-1 nmol/L) required p42/44 mitogen-activated protein kinase and signaling through RhoA/Rho-kinase-dependent and -independent pathways, respectively. As expected, the VEGFR signaling inhibitor ZD4190 selectively abrogated the proinvasive activity of VEGF in collagen gels (IC(50), 10 nmol/L) and chick heart fragments. We identify a novel function for VEGF-165 and Sema3A as proinvasive factors for human colorectal cancer cells. Interestingly, oral administration of the single drug ZD4190 to athymic mice (50 mg/kg/d, once daily) inhibited by 70% the growth of HCT8/S11 tumor cell xenografts. Combinations between the src tyrosine kinase inhibitor M475271 and ZD4190 or cisplatin resulted in additive therapeutic activity against LNM35 human lung tumor xenografts. Our data have significant implications for new therapeutic approaches and individualized treatment targeting VEGFR and src signaling pathways in combination with established clinical drugs at primary tumors and distant metastases in colon and lung cancer patients.
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PMID:Inhibition of vascular endothelial growth factor (VEGF)-165 and semaphorin 3A-mediated cellular invasion and tumor growth by the VEGF signaling inhibitor ZD4190 in human colon cancer cells and xenografts. 1692 28

Tyrosine kinases, which are important regulators of intracellular signal-transduction pathways, have mutated forms that are often associated with oncogenesis and are attractive targets for therapeutic intervention. Recently, systematic mutational analyses of tyrosine kinases revealed that a minimum of 30% of colorectal cancer contain at least one mutation in the tyrosine kinases. To further explore these mutations, we examined all reported mutations of NTRK3, FES, KDR, EPHA3, NTRK2, JAK1, PDGFRA, EPHA7, EPHA8, ERBB4, FGFR1, MLK4 and GUCY2F genes in the 24 colorectal cancer cell lines. Unexpectedly, among 24 colorectal cancer cell lines, only two cell lines (LoVo and CaR1) harbored mutation C1408T (R470C) in MLK4 gene. The mutation rate was extremely low compared to that previously reported. Therefore, we analyzed mutations in 46 colorectal cancer samples resected from the same number of Japanese patients. Surprisingly, none of the 46 samples contained any of the mutations reported. Based on our study, we advise that a more comprehensive tyrosine kinase gene mutation assay is necessary in the future.
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PMID:Absence of tyrosine kinase mutations in Japanese colorectal cancer patients. 1701 44

In combination chemotherapy for metastatic colorectal cancer, i.v. 5-fluorouracil (5-FU) can be replaced by oral 5-FU (in the form of capecitabine or another orally available analogue) without negatively affecting overall toxicity and without remarkably reducing the efficacy of treatment in terms of response rate or overall survival. Preclinical evidence of synergy has led to promising early and successfully completed studies combining capecitabine plus oxaliplatin with bevacizumab, cetuximab, and epidermal growth factor receptor tyrosine kinase inhibitors. The use of preoperative capecitabine plus radiation is achieving good rates of pathological complete response in rectal cancer. While capecitabine is generally well tolerated, its potential toxicities need careful management and may require individual dose adaption.
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PMID:Update on capecitabine in colorectal cancer. 1703 Jun 42

Novel targeted agents increase the therapeutic armamentarium in metastatic colorectal cancer (mCRC). Monoclonal antibodies against the epidermal growth factor receptor (EGFR) are active against EGFR-expressing mCRC that is refractory to irinotecan. EGFR monoclonal antibodies also have promise in less advanced stages of CRC. Cetuximab and panitumumab are clearly active agents. It has been shown that cetuximab is more active when administered in combination with irinotecan. Phase II studies also report promising activity when monoclonal antibodies against the EGFR are combined with classic chemotherapeutic regimens in the first-line treatment of mCRC. However, the best means of scheduling such agents and integrating them with each other and with chemotherapy have yet to be established. The management of toxicity (particularly rash) and finding appropriate means of selecting patients pose additional challenges. While the occurrence of rash is associated with greater likelihood of response, EGFR staining by immunohistochemistry at baseline is not. For reasons that are not yet clear, the tyrosine kinase inhibitors of EGFR seem less effective than their monoclonal antibody counterparts in the therapy of mCRC.
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PMID:Challenges in the use of epidermal growth factor receptor inhibitors in colorectal cancer. 1703 Jun 43

The EGFR is a validated anticancer target whose successful exploitation has added novel agents to our current treatment protocols. Subsets of patients have shown to benefit the most from these therapies, and though these differential responses have yet to be completely defined, they are mostly of genetic nature. Egfr amplifications have shown to increase sensitivity to both small molecule inhibitors and specific monoclonal antibodies targeting the EGFR. A somatic/germline egfr intron 1 CA repeat sequence polymorphism has shown to have an important role in the control of EGFR protein expression, and has been linked to an increased risk of familial breast cancer, a worse outcome in patients with colorectal cancer, and anti-EGFR treatment efficacy in preclinical models. Egfr activating mutations have been recently described in lung cancer linking a cluster of genotypes with sensitivity to EGFR tyrosine kinase pharmacological inhibition. Despite the initial excitement that this discovery elicited, follow-up reports have not unequivocally confirmed this finding, and these drugs have been solidly efficacious both in individual patients and in diseases generally lacking egfr mutations such as pancreas cancer. We are witnessing exciting developments in the field of the pharmacogenomics of cancer, and this has particularly evolved in the area pertaining EGFR tyrosine kinase inhibitors. This review will discuss the background and currently available preclinical and clinical data.
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PMID:Pharmacogenomics of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. 1704 3


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