Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously reported that the ErbB2 oncoprotein prolongs and amplifies growth factor signalling by impairing ligand-dependent downregulation of hetero-oligomerised epidermal growth factor receptors. Here we show that treatment of A431 cells with different epidermal growth factor receptor ligands can cause growth inhibition to an extent paralleling ErbB2 tyrosine phosphorylation. To determine whether such growth inhibition signifies an interaction between the cell cycle machinery and ErbB2-dependent alterations of cell signalling kinetics, we used MCF7 breast cancer cells (which express wild-type p53) to create transient and stable ErbB2 transfectants (MCF7-B2). Compared with parental cells, MCF7-B2 cells are characterised by upregulation of p53, p21(WAF) and Myc, downregulation of Bcl2, and apoptosis. In contrast, MCF7-B2 cells co-transfected with dominant negative p53 (MCF7-B2/Delta p53) exhibit reduced apoptosis and enhanced growth relative to both parental MCF7-B2 and control cells. These data imply that wild-type p53 limits survival of ErbB2-overexpressing breast cancer cells, and suggest that signals of varying length and/or intensity may evoke different cell outcomes depending upon the integrity of cell cycle control genes. We submit that acquisition of cell cycle control defects may play a permissive role in ErbB2 upregulation, and that the ErbB2 overexpression phenotype may in turn select for the survival of cells with p53 mutations or other tumour suppressor gene defects.
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PMID:Dominant negative knockout of p53 abolishes ErbB2-dependent apoptosis and permits growth acceleration in human breast cancer cells. 1195 57

The LRIG1 gene (formerly LIG-1), recently cloned by us, displays structural similarities to the Drosophila Kek I gene. Kek I encodes a cell surface protein, Kekkon-1, which inhibits epidermal growth factor receptor-mediated signalling. We localized the LRIG1 gene to chromosome band 3p14.3, a region known to be deleted in various human cancers. In the present study LRIG1 gene expression was examined in different tumour cell lines and corresponding normal tissues by real-time RT-PCR. In many tumour cell lines, LRIG1 expression appeared absent or was down regulated compared to corresponding normal tissues. The results are consistent with LRIG1 being a tumour suppressor gene in humans. However, further studies are justified to elucidate the explicit role of LRIG1 as a negative regulator of oncogenesis.
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PMID:Is LRIG1 a tumour suppressor gene at chromosome 3p14.3? 1223 26

In de novo glioblastoma multiforme, loss of the tumour suppressor protein PTEN can coincide with the expression of a naturally occurring mutant epidermal growth factor receptor known as deltaEGFR. DeltaEGFR signals constitutively via the phosphatidylinositol 3-kinase (PI3K)/protein kinase Akt and mitogen-activated protein kinase pathways. In human U87MG glioblastoma cells that lack PTEN, deltaEGFR expression enhances tumourigenicity by increasing cellular proliferation. Inhibition of PI3K signaling with the pharmacologic inhibitor wortmannin, or by the reconstitution of physiological levels of PTEN to dephosphorylate the lipid products of PI3K, negated the growth advantage imparted by deltaEGFR on U87MG cells. PTEN reconstitution suppressed the elevated PI3K signaling, without affecting mitogen-activated protein kinase signaling and caused a delay in G1 cell cycle progression that was concomitant with increased cyclin-dependent protein kinase inhibitor p21CIP1/WAF1 protein levels. Our study provides insight into the mechanism by which deltaEGFR may contribute to glioblastoma development.
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PMID:Inhibition of phosphatidylinositol 3-kinase signaling negates the growth advantage imparted by a mutant epidermal growth factor receptor on human glioblastoma cells. 1270 66

Erlotinib [Tarceva, R 1415, CP 358774, OSI 774, NSC 718781] is a small molecular, once-a-day, orally active inhibitor of the epidermal growth factor receptor tyrosine kinase. This profile has been selected from R&D Insight, a pharmaceutical intelligence database produced by Adis International Ltd. It is one of a class of anticancer drugs that target the underlying molecular mechanism involving oncogenes and tumour suppressor genes, which play critical roles in the conversion of normal cells into a cancerous state. Erlotinib is undergoing clinical development as an oral tablet by an alliance between OSI Pharmaceuticals, Genentech and Roche. OSI Pharmaceuticals, Genentech and Roche have entered an agreement for the global development and commercialisation of erlotinib. Under the terms of the agreement, Genentech and OSI will share costs and profit-taking for commercialising the product in the US. The overall costs of the development programme will be shared equally between the three companies. OSI will keep certain co-promotion rights in the US and Genentech will be responsible for commercialising the drug in the US should the FDA approve it. Roche will take the responsibility for obtaining regulatory approval and commercialisation in territories outside the US and pay royalties to OSI on net sales of the product in these markets. Initially, the alliance partners intend to pursue development of erlotinib in all the major tumour markets, particularly for non-small cell lung cancer (NSCLC) in which the group will focus on front-line combination approaches. Pfizer and OSI Pharmaceuticals in the US were developing erlotinib as a treatment for solid tumours. However, in June 2000, Pfizer merged with Warner-Lambert. The resulting company retained the Pfizer name, but in order to meet Federal Trade Commission requirements for the merger Pfizer granted all developmental and marketing rights for erlotinib to OSI Pharmaceuticals. This divestiture of the erlotinib portfolio, in effect, gave OSI a royalty-free, cashless license to the drug. In November 2001, OSI announced a partnership deal with HopeLink Corporation, a healthcare information technology company with an Internet-based Clinical Trial Service. The partnership will enable OSI to heighten awareness of its clinical trials and shorten patient accrual times. It will initially involve the presentation of the OSI phase III pancreatic and refractory NSCLC trials via Hopelink's Syndicated Network. In addition to this the two companies have also agreed to develop additional products and service together that will increase the efficiency of the clinical trial process, increase awareness of clinical trials, and enhance patient accrual techniques. OSI has also entered into an agreement with Therradex, a contract research organisation (CRO) to monitor phase II trials for erlotinib in NSCLC, ovarian and head and neck cancer. In addition, OSI entered into an agreement in 2001 with the US NCI. The NCI is conducting trials in a variety of different cancers. A phase III front-line NSCLC trial (TRIBUTE) of erlotinib in combination with carboplatin and paclitaxel was initiated in July 2001. The multicentre study is being conducted by Genentech in 1000 patients in the US, and will determine whether the addition of erlotinib to carboplatin chemotherapy is able to improve the duration of patient survival. Enrolment for this trial was completed in July 2002. An independent Data Monitoring Committee (DMC) has since reviewed the data from the trial and concluded that there are no safety or efficacy concerns that would warrant stopping the trial. However, the DMC did recommend stopping erlotinib at the time of disease progression or at the start of second-line therapy. A front-line phase III study of erlotinib in NSCLC (TALENT) in combination with gemcitabine and cisplatin chemotherapy was initiated by Roche in Europe in November 2001. Enrolment into this study was completed in September 2002, with approximately 1200 patients. Roche has confirmed that the study woulde has confirmed that the study would be included in the alliance's potential regulatory submission for front-line therapy in chemotherapy-naive patients in the US. Data from the trial is expected in the second half of 2003. OSI has opened two additional phase Ib studies to examine the potential of erlotinib in combination with carboplatin and paclitaxel in one study and gemcitabine and cisplatin in the other. A phase I study of erlotinib is also being conducted in patients with lung cancer in Japan. OSI received fast-track status from the US FDA in September 2002 for erlotinib as a second- or third-line treatment for patients with incurable stage IIIB/IV NSCLC who have failed to respond to standard therapy for advanced metastatic disease. Fast-track status was also granted to erlotinib in May 2002 for the treatment of chemotherapy-naive stage III/IV NSCLC. There are important differences between phase III studies of erlotinib and AstraZeneca's direct competitor drug gefitinib, which recently returned disappointing results in a frontline NSCLC trial with combination chemotherapy. In assessing the survival benefit of erlotinib with chemotherapy, the dose employed of 150 mg/day is the maximum tolerated dose (MTD), whereas the gefitinib trials were conducted at relatively lower doses than the MTD determined in earlier phase I studies. OSI is also investigating the survival benefit of erlotinib in a phase III study in refractory NSCLC patients, a key registration study. Patient size of the NSCLC trial was increased from 330 to 700 as OSI shifted emphasis from its pancreatic cancer trials. Phase II development for this indication was initiated based on data from a phase I trial, which had completed patient enrolment by April 2003. OSI and the US NCI signed a collaborative research agreement in 2001. The NCI is developing erlotinib through its CTEP programme for multiple tumour types including epithelial malignancies, gastrointestinal and genitourinary tracts, gynaecological malignancies and brain tumours. OSI supplies erlotinib for the trial, but the NCI provides the funding and manages the trials. A series of approximately ten phase Ib trials are already underway or were set to start in the US in 2001 to determine safety, tolerance and pharmacokinetic parameters of erlotinib in combination with a number of commonly used chemotherapeutic agents. The Wall Street Journal reported on 25 February 2002, that analysts at Robert Stephens, New York, USA, have forecast Tarceva to reach annual sales of >$US1 billion. Other analysts, at Merrill Lynch & Co., have predicted that products belonging to the same class as Tarceva could reach combined worldwide sales of $US6 billion to $US10 billion annually. In an earlier report by the Financial Times on 10 May 2001, it was stated that approximately 12 new anticancer agents are expected to be approved by the FDA through to the end of 2002. These agents, of which Tarceva is one, were said to have the potential to generate total sales of $US2.6 billion. Goldman Sachs have forecast Tarceva to reach peak sales of $US250 million for the indication of head and neck cancer alone. Previously in January 2001, the Financial Times claimed that OSI Pharmaceuticals, one of the development partners for Tarceva, stood to gain $US187 million pending regulatory approval. Genentech and Roche were each said to be buying $US35 million worth of OSI's stock and paying upfront fees. Tarceva is facing competition by two similar compounds, developed by AstraZeneca and ImClone, respectively.
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PMID:Erlotinib: CP 358774, NSC 718781, OSI 774, R 1415. 1284 90

In all, 31 renal cell carcinomas (RCCs) were examined for expression of the potential tumour suppressor LRIG1 (formerly Lig-1) and the epidermal growth factor receptor (EGFR). Eight matched samples of uninvolved kidney cortex were also evaluated. Gene expression was examined by quantitative real-time RT-PCR. In the eight matched sample pairs (uninvolved kidney cortex and tumour), protein expression was examined by immunohistochemistry. Conventional (clear cell) tumours showed an expected upregulation of EGFR. LRIG1 expression was generally downregulated in conventional and papillary RCC but not in chromophobic RCC. The ratio between EGFR and LRIG1 was more than 2.5-fold higher in the eight tumours compared with matched uninvolved kidney cortex and was at least two-fold higher than the mean normal ratio in 21 of 31 samples analysed. The observed downregulation of LRIG1 and increased EGFR/LRIG1 ratios are consistent with LRIG1 being a suppressor of oncogenesis in RCC by counteracting the tumour-promoting properties of EGFR. Further studies are justified to elucidate the explicit role of LRIG1 in the oncogenesis of RCC.
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PMID:LRIG1 and epidermal growth factor receptor in renal cell carcinoma: a quantitative RT--PCR and immunohistochemical analysis. 1452 Apr 61

RNA interference (RNAi) has the potential to knock down oncogenes in cancer, including brain cancer. However, the therapeutic potential of RNAi will not be realised until the rate-limiting step of delivery is solved. The development of RNA-based therapeutics is not practical, due to the instability of RNA in vivo. However, plasmid DNA can be engineered to express short hairpin RNA (shRNA), similar to endogenous microRNAs. Intravenous, non-viral RNAi-based gene therapy is enabled with a new gene-targeting technology, which encapsulates the plasmid DNA inside receptor-specific pegylated immunoliposomes (PILs). The feasibility of this RNAi approach was evaluated by showing it was possible to achieve a 90% knockdown of brain tumour-specific gene expression with a single intravenous injection in adult rats or mice with intracranial brain cancer. The survival of mice with intracranial human brain cancer was extended by nearly 90% with weekly intravenous injections of PILs carrying plasmid DNA expressing a shRNA directed against the human epidermal growth factor receptor. RNAi-based gene therapy can be coupled with gene therapy that replaces mutated tumour suppressor genes to build a polygenic approach to the gene therapy of cancer.
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PMID:Intravenous, non-viral RNAi gene therapy of brain cancer. 1526 77

PTEN is a novel tumour suppressor gene located on chromosome 10. PTEN mutations are believed to exert their effects through the putative PI3K-AKT-mTOR signalling pathway. Specifically, loss of PTEN leads to activation of AKT, which in turn promotes anti-apoptotic and pro-cell cycle entry pathways believed to be essential in tumourigenesis. Whilst PTEN mutations are frequent in a variety of sporadic cancers and inherited cancer syndromes, it is not clear how frequently PTEN mutations and immunohistochemical loss of PTEN expression occur in sporadic breast cancer. This study used tissue microarrays (TMAs) to assess wild-type PTEN and pAKT immunohistochemical staining in 670 and 691 cases, respectively, of primary operable breast cancer. Scores of 0, 1, and 2 were given for negative, weakly positive, and strongly positive degrees of immunoreactivity, respectively. In addition, immunohistochemical assessment of epidermal growth factor receptor (EGFR), Her2, and proliferation by MIB1 expression was performed on the same TMAs and the scores were compared with those of PTEN and pAKT. Eight per cent of cases did not express wild-type PTEN. No correlation was observed between patient, tumour and outcome variables and PTEN. pAKT expression correlated inversely with adverse tumour variables such as tumour grade (p< 0.001) and correlated positively with ER status (p< 0.001). No correlation was seen between either PTEN or AKT and EGFR, Her2 or MIB1. No association of PTEN or pAKT was seen in Kaplan-Meier or multivariate analysis for overall survival. The results indicate that loss of PTEN expression is infrequent in breast cancer. PTEN and AKT do not appear to be prognostic markers. The study argues against the current model of a simple linear tumourigenic PTEN-PI3K-AKT-mTOR pathway in breast cancer. It also suggests that, in this group of breast cancers, the most common upstream regulator of AKT may be ER rather than PTEN, EGFR or Her2.
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PMID:The role of PTEN and its signalling pathways, including AKT, in breast cancer; an assessment of relationships with other prognostic factors and with outcome. 1530 42

Squamous cell carcinoma of the head and neck (HNSCC) is a heterogeneous but largely preventable disease with complex molecular abnormalities. It arises from a premalignant progenitor followed by outgrowth of clonal populations associated with cumulative genetic alterations and phenotypic progression to invasive malignancy. These genetic alterations result in inactivation of multiple tumour suppressor genes and activation of proto-oncogenes, including p16(ink4A), p53, cyclin D1, p14(ARF), FHIT, RASSF1A, epidermal growth factor receptor (EGFR), and Rb. Intramucosal migration and clonal expansion of transformed cells with formation of abnormal genetic fields appear to be responsible for local recurrences and development of second primary tumours.
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PMID:Molecular biology of squamous cell carcinoma of the head and neck. 1664 82

Accumulating evidence suggests that cancer can be envisioned as a "signaling disease", in which alterations in the cellular genome affect the expression and/or function of oncogenes and tumour suppressor genes. This ultimately disrupts the physiologic transmission of biochemical signals that normally regulate cell growth, differentiation and programmed cell death (apoptosis). From a clinical standpoint, signal transduction inhibition as a therapeutic strategy for human malignancies has recently achieved remarkable success. However, as additional drugs move forward into the clinical arena, intrinsic and acquired resistance to "targeted" agents becomes an issue for their clinical utility. One way to overcome resistance to targeted agents is to identify genetic and epigenetic aberrations underlying sensitivity/resistance, thus enabling the selection of patients that will most likely benefit from a specific therapy. Since resistance often ensues as a result of the concomitant activation of multiple, often overlapping, signaling pathways, another possibility is to interfere with multiple, cross-talking pathways involved in growth and survival control in a rational, mechanism-based, fashion. These concepts may be usefully applied, among others, to agents that target two major signal transduction pathways: the one initiated by epidermal growth factor receptor (EGFR) signaling and the one converging on mitogen-activated protein kinase (MAPK) activation. Here, we review the molecular mechanisms of sensitivity/resistance to EGFR inhibitors, as well as the rationale for combining them with other targeted agents, in an attempt to overcome resistance. In the second part of the paper, we review MAPK-targeted agents, focusing on their therapeutic potential in haematologic malignancies, and examine the prospects for combinations of MAPK inhibitors with cytotoxic agents or other signal transduction-targeted agents to obtain synergistic anti-tumour effects.
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PMID:Overcoming resistance to molecularly targeted anticancer therapies: Rational drug combinations based on EGFR and MAPK inhibition for solid tumours and haematologic malignancies. 1748 3

Oligosaccharides are present in human milk in large amounts and in a high variety. We have previously shown that these oligosaccharides are strong inhibitors of proliferation and inducers of differentiation in intestinal cell lines. To elucidate the molecular mechanism, we investigated the influence on cell cycle events via flow cytometry and expression levels by using quantitative real-time RT-PCR. Human intestinal cells, i.e. HT-29, HIEC and Caco-2 cells, were exposed to neutral or acidic human milk oligosaccharides. Both fractions induced a concentration-dependent G2/M arrest. Cell cycle analysis for HT-29 revealed 37 % of cells in G1 and 35 % in G2/M (neutral oligosaccharides) and incubation with acidic oligosaccharides led to 42 % cells in G1 and 40 % in G2/M. In control experiments without oligosaccharides we found 71 % of cells to be in G1 and 17 % in G2/M. This G2/M arrest was associated with changes in mRNA expression of cyclin A and B. A G2/M arrest with concomitant alterations of cell cycle gene expression could also be shown for HIEC and Caco-2 cells. Analysing the expression of cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1) and the tumour suppressor p53 we observed that the expression of p21(cip1) was p53-independent and necessary for arresting cells in the G2/M phase, while p27(kip1) was associated with differentiation effects. Both neutral and acidic human milk oligosaccharides were able to induce epidermal growth factor receptor, extracellular signal-regulated kinase 1/2 and p38 phosphorylation. These results suggest that oligosaccharides from human milk inhibited intestinal cell proliferation and altered cell cycle dynamics by affecting corresponding regulator genes and mitogen-activated protein kinase signalling.
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PMID:Oligosaccharides from human milk induce growth arrest via G2/M by influencing growth-related cell cycle genes in intestinal epithelial cells. 1907 36


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