Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mesothelioma is induced almost exclusively by exposure to asbestos fibers. We have investigated whether the induction of DNA damage in human bronchial epithelial BEAS 2B cells and human mesothelial MeT 5A cells by crocidolite asbestos (2 microg/cm2) requires the presence of asbestos fibers in the cells. DNA damage was measured microscopically by the Comet assay, and the presence of fibers in the same cells was assessed using bright-field illumination. After treatment times of 6-72 hr, damage levels were, on the average, two times higher in cells with fibers than in cells without fibers. It was further found that DNA damage decreased with time in BEAS 2B cells both with and without fibers. No decrease in damage with time was seen in MeT 5A cells, suggesting that these mesothelial cells repair the initial damage poorly, lack induction of protective systems, or constantly produce high levels of damaging species. Our results indicate that crocidolite-treated human mesothelial MeT 5A and bronchial epithelial BEAS 2B cells show an elevated level of DNA damage if they contain a fiber. In comparison with epithelial BEAS 2B cells, mesothelial MeT 5A cells have more DNA damage after the crocidolite treatment and the damage is more persistent.
Environ Mol Mutagen 2004
PMID:DNA damage in bronchial epithelial and mesothelial cells with and without associated crocidolite asbestos fibers. 1553 64

Exosomes are nanometer sized vesicles, secreted by a diverse range of cell types, whose biological functions remain ambiguous. Several groups have demonstrated the potential of manipulating exosomes for activating cellular immune responses. The possibility that exosomes may inhibit immunological responses, however, has not been widely addressed. We have investigated if exosomes produced by tumor cells can inhibit immunological functions, through modulating expression of the NKG2D receptor by effector cells. Incubating tumor exosomes with fresh peripheral blood leukocytes resulted in a marked reduction in the proportion of NKG2D-positive CD3+CD8+ Cells, and CD3- cells by 48 h. This effect was dose dependent and was shown with exosomes from different tumor cells including breast cancer and mesothelioma. Analysis of tumor exosome-phenotype revealed positive expression of several NKG2D ligands, and antibody blocking experiments revealed the importance of such ligands in driving the reduction in the proportion of NKG2D-positive effector cells. The functional importance of the decrease in NKG2D-positive cells was addressed in vitro cytotoxicity assays. For example a CD8+ T cell line pre-incubated with tumor exosomes had significant decreased capacity to kill peptide-pulsed T2 target cells. These data highlight a role for tumor exosomes bearing NKG2D ligands as a mechanism contributing to cancer immune evasion.
Blood Cells Mol Dis
PMID:Exosomes and the MICA-NKG2D system in cancer. 1588 3

Like many tumors, malignant mesothelioma exhibits significant chemoresistance and resistance to apoptosis in vivo that is not seen in current in vitro models. To study the mechanisms of this multicellular resistance, biologically relevant in vitro models are necessary. Therefore, we characterized and tested human mesothelioma tissue grown in vitro as tumor fragment spheroids. After 5-10 d in culture, fragments from each of 15 human mesothelioma tumors rounded into spheroids. The tumor fragment spheroids maintained multiple characteristics of the original tumors for up to 3 mo including the presence of viable mesothelioma cells, macrophages, and a collagen-rich stroma. In 14-d-old spheroids, mesothelioma cells showed the same proliferation rate and expression of a death receptor, DR5, as in the original tumor. To determine responses to treatment, we treated tumor fragment spheroids grown from three separate tumors with agents, TNF-related apoptosis-inducing ligand (TRAIL) plus cycloheximide, that induced near total apoptosis in three human mesothelioma cell lines (M28, REN, MS-1) grown as monolayers (94 +/- 6% apoptosis; mean +/- SEM). Compared with mesothelioma cells in monolayers, mesothelioma cells in the spheroids were resistant to TRAIL plus cycloheximide (32 +/- 4% apoptosis; mean +/- SEM). Apoptotic resistance of mesothelioma cells was significantly reduced by inhibiting either the PI3K/Akt pathway with LY294002 (47 +/- 6% apoptosis) or the mTOR pathway with rapamycin (50 +/- 17% apoptosis). We conclude that human mesothelioma can be maintained in vitro in a biologically relevant model that exhibits apoptotic resistance, thereby permitting study of its tumor biology and of novel approaches to therapy.
Am J Respir Cell Mol Biol 2005 Dec
PMID:A novel in vitro model of human mesothelioma for studying tumor biology and apoptotic resistance. 1612 94

The pleural space is an attractive site for using viral vectors to deliver gene products to the lung parenchyma, other thoracic structures and the systemic circulation. The advantages of intrapleural gene transfer using viral vectors include: (i) easy accessibility; (ii) large surface area; (iii) ability to provide high concentrations of secreted gene products to chest structures; (iv) low risk of detrimental effects of possible vector-induced inflammation compared with intravascular delivery; and (v) because it is local, lower vector doses can be used to deliver therapeutic genes to thoracic structures than less efficient systemic routes. Examples of pleural gene transfer include the use of adenovirus vectors to treat mesothelioma by transiently expressing genes that encode toxic proteins, immunomodulatory molecules or anti-angiogenesis factors. Intrapleural delivery of adeno-associated viral vectors represents an efficient strategy to treat alpha1-antitrypsin (alpha1AT) deficiency, achieving high lung and systemic therapeutic levels of alpha1AT. Intrapleural delivery of gene transfer vectors holds promise for the treatment of diseases requiring transient, localized gene expression, as well as sustained expression of genes to correct hereditary disorders requiring localized or systemic expression of the therapeutic protein.
Curr Opin Mol Ther 2005 Oct
PMID:Intrapleural 'outside-in' gene therapy: therapeutics for organs of the chest via gene transfer to the pleura. 1624 79

Pemetrexed, a new generation antifolate recently approved for the treatment of mesothelioma and non-small cell lung cancer, is an excellent substrate for the reduced folate carrier (RFC). To explore the carrier's effect on pemetrexed activity, RFC was inactivated in HCT-15 colon cancer cells by mutagenesis and PT632 selective pressure. A clone (PT1) was obtained with a glycine to arginine substitution at amino acid 401, resulting in the loss of RFC function. PT1 cells were resistant to PT632 (178-fold), methotrexate (4-fold), and ZD1694 (Tomudex, raltitrexed; 20-fold), but were 3-fold collaterally sensitive to pemetrexed when grown in 25 nmol/L of 5-formyltetrahydrofolate. PT1 cells transfected with wild-type RFC had antifolate sensitivities comparable to that of wild-type HCT-15 cells, indicating that the RFC mutation was the sole basis for resistance. Folate pools were contracted in PT1 cells by 32% or 60%, as measured by radiolabeling intracellular folates or by an enzyme binding assay, respectively. This was reflected in marked (6.5-fold) collateral sensitivity to trimetrexate. The initial uptake of pemetrexed in PT1 cells was markedly reduced ( approximately 85%) but intracellular pemetrexed levels increased to approximately 60% and approximately 70% to that of wild-type cells after 2 hours and 6 days, respectively. There was increased pemetrexed inhibition of glycinamide ribonucleotide transformylase and, to a lesser extent, thymidylate synthase in PT1 cells growing in 5-formyltetrahydrofolate based on nucleoside protection analyses. Hence, loss of RFC function leads to collateral sensitivity to pemetrexed in HCT-15 cells, likely due to cellular folate pool contraction resulting in partial preservation of pemetrexed polyglutamylation and increased target enzyme inhibition. micro
Mol Cancer Ther 2006 Feb
PMID:The inverse relationship between reduced folate carrier function and pemetrexed activity in a human colon cancer cell line. 1650 19

The aim of this study was to test the possibility of using human antibodies to study the pathogenic mechanism of SV40 and asbestos in a hamster mesothelioma model. The cellular lysates from human and hamster primary mesothelial cells were tested by Western blot analysis. All of the antibodies we tested (HGF, Notch, VEGF, Sp1, p53, PP2A, p-ERK1, p-c-jun, Fra1, Fra2, MMP1, MMP9, NFkappaB p65, IkappaB, GAPDH) cross-reacted with their hamster counterparts. These data indicate that hamster mesothelioma model and more in general hamster experimental model, can be used for functional studies because many mouse, rabbit, and goat monoclonal antibodies prepared against human antigens cross-react with their hamster counterparts.
Mol Carcinog 2006 Jul
PMID:Cross reactivity between many anti-human antibodies for their hamster homologs provide the tools to study the signal transduction pathway activated by asbestos and SV40 in the malignant mesothelioma model. 1664 49

Malignant mesothelioma is an aggressive tumor of the serosal surfaces of the lungs, heart, and abdomen. Survival rates are poor and effective treatments are not available. However, recent therapeutic regimens targeting thymidylate synthase (TS) in malignant mesothelioma patients have shown promise. We have reported the use of an antisense oligodeoxynucleotide targeting TS mRNA (antisense TS ODN 83) to inhibit growth of human tumor cells. To test the potential for antisense targeting of TS mRNA in treatment of malignant mesothelioma, we assessed and compared the effects of antisense TS ODN 83 on three human malignant mesothelioma cell lines (211H, H2052, and H28) and human nonmalignant mesothelioma cells (HT29 colorectal adenocarcinoma, HeLa cervical carcinoma, and MCF7 breast tumor cell lines). We report that ODN 83 applied as a single agent effectively reduced TS mRNA and protein in malignant mesothelioma cell lines. Furthermore, it inhibited malignant mesothelioma growth significantly more effectively than it inhibited growth of nonmalignant mesothelioma human tumor cell lines: a difference in susceptibility was not observed in response to treatment with TS protein-targeting drugs. In malignant mesothelioma cells, antisense TS both induced apoptotic cell death and reduced proliferation. In nonmalignant mesothelioma cells, only reduced proliferation was observed. Thus, antisense TS-mediated induction of apoptosis may be the basis for the high malignant mesothelioma sensitivity to antisense targeting of TS. Further preclinical and clinical study of TS antisense oligodeoxynucleotides, alone and in combination with TS-targeting chemotherapy drugs, in mesothelioma is warranted.
Mol Cancer Ther 2006 Jun
PMID:Therapeutic potential of antisense oligodeoxynucleotides to down-regulate thymidylate synthase in mesothelioma. 1681

Lung cancers, malignant mesotheliomas (MM), and fibrosis are devastating diseases with limited treatment strategies, in part due to poorly-effective drug delivery to affected areas of lung. We hypothesized that acid-prepared mesoporous spheres (APMS) (1-2 microm diameter, 40 A pore size) might be effective vehicles for pulmonary chemotherapeutic drug delivery. To assess this, APMS, chemically modified with different surface molecules (lipid, a linker having a terminal amine group, a thiol group, or tetraethylene glycol [TEG]), were evaluated for uptake and possible cytotoxic effects after in vitro administration to murine alveolar epithelial Type II (C10) and human mesothelioma (MM) cells and after intrapleural or intranasal administration to C57Bl/6 mice. APMS coated with TEG (APMS-TEG) were most efficiently taken up by C10 and MM cells. The mechanism of cell uptake was rapid, actin-dependent, and did not involve clathrin- or caveolae-mediated mechanisms nor fusion of membrane-bound APMS with lysosomes. When injected intrapleurally in mice, APMS-TEG were taken up by both CD45-positive and -negative cells of the diaphragm, lung, and spleen, whereas APMS administered by the intranasal route were predominantly in lung epithelial cells and alveolar macrophages. After intrapleural or intranasal administration, APMS were nonimmunogenic and nontoxic as evaluated by differential cell counts and lactate dehydrogenase levels in bronchoalveolar and pleural lavage fluids. In the treatment of lung and pleural diseases, APMS-TEG may be useful tools to deliver chemotherapeutic drugs or molecular constructs.
Am J Respir Cell Mol Biol 2007 Mar
PMID:Unique uptake of acid-prepared mesoporous spheres by lung epithelial and mesothelioma cells. 1703 62

Pemetrexed is a new-generation antifolate inhibitor of thymidylate synthase (TS) and a weaker inhibitor of glycinamide ribonucleotide transformylase (GARFT) required for de novo purine synthesis. Methylthioadenosine phosphorylase (MTAP) salvages purines by releasing adenine from methylthioadenosine and is often deleted in mesothelioma. The current study addresses the effect of MTAP on pemetrexed activity using a highly potent transition state inhibitor of MTAP, MT-DADMe-Immucillin A (ImmA; K(i) = 86 pmol/L) in the MTAP(+) NCI-H28 and MTAP(-) NCI-H2052 mesothelioma cell lines. Based on selective nucleoside protection, TS was found to be the primary pemetrexed target in both cell lines with GARFT inhibition requiring 20- to 30-fold higher pemetrexed concentrations. ImmA had no effect on pemetrexed activity but, when thymidine was added, the pemetrexed IC(50) decreased by a factor of approximately 3 in MTAP(+) H28 cells with no effect in MTAP(-) H2052 cells. Conversely, the transfection of MTAP into H2052 cells increased the pemetrexed IC(50) by nearly 3-fold but only in the presence of thymidine; this was reversed by ImmA. An MTAP-specific short interfering RNA produced a 2-fold decrease in pemetrexed IC(50) in MTAP(+) HeLa cells in the presence of thymidine. These data indicate that suppression of constitutive MTAP has no effect on pemetrexed activity when the primary target is TS. There is a modest salutary effect when the pemetrexed target is GARFT alone.
Mol Cancer Ther 2006 Oct
PMID:The effect of a novel transition state inhibitor of methylthioadenosine phosphorylase on pemetrexed activity. 1704 Oct 99

Pemetrexed is a new-generation antifolate, approved for the treatment of mesothelioma and non-small cell lung cancer, currently being evaluated for the treatment of a variety of other solid tumors. This review traces the history of antifolates that led to the development of pemetrexed and describes the unique properties of this agent that distinguish it from other antifolates. These include (a) its very rapid conversion to active polyglutamate derivatives in cells that build to high levels and are retained for long intervals to achieve prolonged and potent inhibition of its major target enzyme thymidylate synthase, (b) its high affinity for three folate transporters, and (c) its marked sensitivity to the level of physiologic folates in cells. The latter results in the unique and paradoxical finding that when transport mediated by the major folate transporter (the reduced folate carrier) is impaired, pemetrexed activity is preserved. This is due to concurrent contraction of competing cellular physiologic folates and utilization of a novel second transport carrier for which pemetrexed has high affinity, recently identified as the proton-coupled folate transporter (PCFT). Laboratory studies are reviewed that raise the possibility of new approaches to the use of folic acid supplementation in clinical regimens with pemetrexed.
Mol Cancer Ther 2007 Feb
PMID:Pemetrexed: biochemical and cellular pharmacology, mechanisms, and clinical applications. 1730 42


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