Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51812 (mitogen-activated protein)
 10,636 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatitis C virus (HCV) core protein either enhances or inhibits apoptosis depending on the apoptosis-inducing stimuli and cell conditions. In this paper we studied possible effect of HCV core protein on apoptosis induced by serum starvation. NIH3T3 cells stably expressing HCV core protein were more resistant to serum starvation-induced apoptosis than were the non-expressing control. Neither p53, p21Waf1 nor Bax was detectably induced after serum starvation, irrespective of HCV core protein expression, suggesting that the observed apoptosis is p53-independent. Serum starvation-induced apoptosis was partially inhibited by SB203580, a specific inhibitor of p38 mitogen-activated protein (MAP) kinase, in the non-expressing control, but not in HCV core protein-expressing cells. Moreover, activation of p38 MAP kinase after serum starvation, as measured by the amount of its phosphorylated form, was inhibited in HCV core protein-expressing cells. Our results suggest that HCV core protein inhibits serum starvation-induced apoptosis through inhibition of p38 MAP kinase activation.
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PMID:Suppression of serum starvation-induced apoptosis by hepatitis C virus core protein. 1159 27

Recent studies in cell culture have shown that isothiocyanates (ITCs) induce apoptosis via activation of mitogen-activated protein (MAP) kinases and p53 pathways, suggesting a potential for ITCs or their conjugates to inhibit tumorigenesis during the postinitiation phase. To evaluate whether ITC compounds administered after carcinogen treatment inhibit lung tumorigenesis, we investigated in A/J mice the effects of the N-acetylcysteine (NAC) conjugates of benzyl (BITC-NAC) and phenethyl ITC (PEITC-NAC) in the diet (15 micromol/g) administered after a single dose of 20 micromol benzo(a)pyrene [B(a)P]. The formation of lung adenomas was examined 140 days after B(a)P dosing. Both the BITC-NAC and PEITC-NAC-treated groups showed a significant reduction in lung tumor multiplicity from 6.1 +/- 3.1 tumors/mouse in the B(a)P group fed the control diet to 3.7 +/- 2.9 and 3.4 +/- 2.7 tumors/mouse (P = 0.018 and 0.006, respectively). To investigate the mechanisms of tumor inhibition, lung tissues were obtained at 21, 84, and 140 days at interim sacrifices during the bioassay. These tissues showed a significant increase in apoptosis as determined by in situ end-labeling for both ITC-NAC-treated groups. The MAP kinase pathway was activated in the ITC-NAC-treated groups. The activation of c-Jun NH(2)-terminal kinase was higher in the BITC-NAC and PEITC-NAC groups when compared with B(a)P-treated control. The phosphorylation of p38 and extracellular signal-regulated kinases (ErKs) 1 and 2 was also induced by these treatments. To determine the downstream target of MAP kinases, activator protein-1 (AP-1) and nuclear factor-kappaB activities were evaluated by gel shift assay. The AP-1 binding activity was remarkably increased in lung tissue from both the BITC-NAC and PEITC-NAC groups. No change in nuclear factor-kappaB binding activity was found, however. Phosphorylation of p53 was also higher than the constitutive levels in both ITC-NAC-treated groups, but no induction of p53 expression was detected. This study demonstrates the chemopreventive efficacy of the NAC conjugates of PEITC and BITC administered in the diet after a single dose of B(a)P for lung tumorigenesis and provides the first in vivo evidence that activation of MAP kinases, AP-1 transcription factors, p53 phosphorylation, and the induction of apoptosis may be involved in the chemopreventive activity of these compounds.
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PMID:Inhibition of benzo(a)pyrene-induced lung tumorigenesis in A/J mice by dietary N-acetylcysteine conjugates of benzyl and phenethyl isothiocyanates during the postinitiation phase is associated with activation of mitogen-activated protein kinases and p53 activity and induction of apoptosis. 1178 48

Arsenic is a well-documented carcinogen that also appears to be a valuable therapeutic tool in cancer treatment. This creates a paradox for which no unified hypothesis has been reached regarding the molecular mechanisms that determine whether arsenic will act as a carcinogen or as an effectual chemotherapeutic agent. Much of our knowledge with respect to the actions of arsenic has been drawn from epidemiological or clinical studies. The actions of arsenic are likely to be related to cell type, arsenic species, and length and dose of exposure. Arsenic unquestionably induces apoptosis and may specifically target certain tumor cells. Research data strongly suggest that arsenic influences distinct signaling pathways involved in mediating proliferation or apoptosis, including mitogen-activated protein kinases, p53, activator protein-1 or nuclear factor kappa B. The primary purpose of this review is to examine recent findings, from this laboratory and others, that focus on the molecular mechanisms of arsenic's actions in cell transformation and as a therapeutic agent.
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PMID:The paradox of arsenic: molecular mechanisms of cell transformation and chemotherapeutic effects. 1192 65

Oncogenic activation of the mitogen-activated protein (MAP) kinase cascade in murine fibroblasts initiates a senescence-like cell cycle arrest that depends on the ARF/p53 tumor suppressor pathway. To investigate whether p53 is sufficient to induce senescence, we introduced a conditional murine p53 allele (p53(val135)) into p53-null mouse embryonic fibroblasts and examined cell proliferation and senescence in cells expressing p53, oncogenic Ras, or both gene products. Conditional p53 activation efficiently induced a reversible cell cycle arrest but was unable to induce features of senescence. In contrast, coexpression of oncogenic ras or activated mek1 with p53 enhanced both p53 levels and activity relative to that observed for p53 alone and produced an irreversible cell cycle arrest that displayed features of cellular senescence. p19(ARF) was required for this effect, since p53(-/-) ARF(-/-) double-null cells were unable to undergo senescence following coexpression of oncogenic Ras and p53. Although the levels of exogenous p53 achieved in ARF-null cells were relatively low, the stabilizing effects of p19(ARF) on p53 could not explain the cooperation between oncogenic Ras and p53 in promoting senescence. Hence, enforced p53 expression without oncogenic ras in p53(-/-) mdm2(-/-) double-null cells produced extremely high p53 levels but did not induce senescence. Taken together, our results indicate that oncogenic activation of the MAP kinase pathway in murine fibroblasts converts p53 into a senescence inducer through both quantitative and qualitative mechanisms.
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PMID:Oncogenic ras and p53 cooperate to induce cellular senescence. 1197 80

Previous studies have suggested that p53 is required for apoptosis induction by phenethyl isothiocyanate (PEITC), which is a highly promising cancer chemopreventive agent. Here, we report that p53 is not required for PEITC-induced apoptosis in the PC-3 human prostate cancer cell line and that the PEITC-induced apoptosis is mediated by extracellular signal-regulated kinases (ERK1/2). Exposure of PC-3 cells to an apoptosis-inducing concentration of PEITC (10 microM) resulted in a rapid and sustained activation of ERK1/2 that was evident as early as 1 h after PEITC treatment and persisted for the duration of the experiment (24-h after PEITC exposure). The PEITC-mediated activation of ERK1/2 was associated with an increase in phosphorylation of its substrate Elk-1 at Ser383. The PEITC-induced activation of ERK1/2 as well as apoptosis was abolished in the presence of mitogen-activated protein/ERK kinase 1 (a kinase upstream of ERK1/2) inhibitor PD98059. Exposure of PC-3 cells to 10 microM PEITC also resulted in a time-dependent activation of p38 protein kinase that was associated with increased phosphorylation of activating transcription factor 2 at Thr71. Even though the PEITC-induced activation of p38 protein kinase was abrogated in the presence of its specific inhibitor SB202190, inhibition of p38 protein kinase activation did not prevent PEITC-induced apoptosis. In contrast to previous reports in other cellular systems, c-Jun NH(2)-terminal kinases were not activated by PEITC treatment in PC-3 human prostate carcinoma cell line. In conclusion, the results of the present study indicate that p53 is not essential for PEITC-induced apoptosis and that the PEITC-induced apoptosis in PC-3 human prostate carcinoma cell line is mediated by ERKs. Thus, it seems reasonable to postulate that PEITC may be effective against tumors with normal as well as mutant p53.
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PMID:Phenethyl isothiocyanate-induced apoptosis in p53-deficient PC-3 human prostate cancer cell line is mediated by extracellular signal-regulated kinases. 1209 62

Adrenocortical carcinoma is a rare tumor that carries a very poor prognosis. Despite efforts to develop new therapeutic regimens to treat this disease, surgery remains the mainstay of treatment. Laboratory studies of adrenocortical cancers have revealed a wide variety of signaling pathways that can be altered in these neoplasms. Although ACTH signaling through adenylyl cyclase and protein kinase A is important for normal adrenal cellular physiology, there is evidence to suggest that this pathway may inhibit the growth of adrenocortical tumors, and that inactivation of the ACTH receptor may promote tumor formation. Although multiple signal transduction pathways are essential for normal adrenal growth and hormone secretion, efforts to identify events required for neoplastic transformation have met with limited success. Alterations that have frequently been observed in adrenocortical carcinoma include up-regulation of the IGF-II system, as well as mutations in TP53 and RAS. Current studies aim to elucidate the mechanisms of tumor growth by studying proproliferative signaling pathways, such as those involving Akt/PKB and the mitogen-activated protein kinases (MAPKs). Although studies of single pathways have been helpful in guiding investigations, new tools to study the integration and multiplicity of signaling pathways hold the hope of improved understanding of the signaling pathway alterations in adrenocortical cancer.
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PMID:Signaling pathways in adrenocortical cancer. 1211 79

Although urothelium is constantly bathed in high concentrations of epidermal growth factor (EGF) and most urothelial carcinomas overexpress EGF receptor (EGFr), relatively little is known about the role of EGFr signaling pathway in urothelial growth and transformation. In the present study, we used the uroplakin II gene promoter to drive the urothelial overexpression of EGFr in transgenic mice. Three transgenic lines were established, all expressing a higher level of the EGFr mRNA and protein in the urothelium than the nontransgenic controls. The overexpressed EGFr was functionally active because it was autophosphorylated, and its downstream mitogen-activated protein kinases were highly activated. Phenotypically, the urinary bladders of all transgenic lines developed simple urothelial hyperplasia that was strongly positive for proliferative cell nuclear antigen and weakly positive for bromodeoxyuridine incorporation. When coexpressed with the activated Ha-ras oncogene in double transgenic mice, EGFr had no apparent tumor-enhancing effects over the urothelial hyperplastic phenotype induced by Ha-ras oncogene. However, when coexpressed with the SV40 large T antigen, EGFr accelerated tumor growth and converted the carcinoma in situ of the SV40T mice into high-grade bladder carcinomas, without triggering tumor invasion. Our studies indicate that urothelial overexpression of EGFr can induce urothelial proliferation but not frank carcinoma formation. Our results also suggest that, whereas EGFr and Ha-ras, both of which act in the same signal transduction cascade, stimulated urothelial hyperplasia, they were not synergistic in urothelial tumorigenesis, and EGFr overexpression can cooperate with p53 and pRB dysfunction (as occurring in SV40T transgenic mice) to promote bladder tumor growth.
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PMID:Overexpression of epidermal growth factor receptor in urothelium elicits urothelial hyperplasia and promotes bladder tumor growth. 1212 55

We have assessed the growth response of Chinese-hamster ovary (CHO) cells to activation of recombinantly expressed G-protein-coupled muscarinic M(2) or M(3) acetylcholine receptors (AChRs). We show that activation of these receptors leads to divergent growth responses: M(2) AChR activation causes an increase in DNA synthesis, whereas M(3) AChR activation causes a dramatic decrease in DNA synthesis. We have characterized the M(3) AChR-mediated growth inhibition and show that it involves a G(1) phase cell-cycle arrest. Further analysis of this arrest indicates that it involves an increase in expression of the cyclin-dependent kinase (CDK) inhibitor, p21(Cip1/Waf1) (where Cip1 is CDK-interacting protein 1 and Waf1 is wild-type p53-associated fragment 1), in response to M(3) AChR activation. This increase in protein expression leads to an increase in p21(Cip1/Waf1) association with CDK2, a decrease in CDK2 activity and an accumulation of hypophosphorylated retinoblastoma protein. The increased p21(Cip1/Waf1) expression is due, at least in part, to an increase in p21(Cip1/Waf1) mRNA, and receptor-mediated changes in phosphorylation of c-Jun provide a mechanism to account for this p21(Cip1/Waf1) transcriptional regulation. Evaluation of the extracellular signal-regulated protein kinase and c-Jun N-terminal kinase activities has shown striking differences in the profiles of activation of these mitogen-activated protein kinases by the M(2) and M(3) AChRs, and their potential involvement in mediating growth arrest by the M(3) AChR is discussed.
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PMID:Growth inhibition by the muscarinic M(3) acetylcholine receptor: evidence for p21(Cip1/Waf1) involvement in G(1) arrest. 1212 81

The human disease neurofibromatosis type 1 (NF1) is caused by mutations in the NF1 gene, and is characterized by the formation of benign and malignant tumors of the peripheral nervous system. We have shown previously that aberrant expression of the epidermal growth factor receptor (EGFR) is a common feature of human NF1-related tumor development in humans and in NF1 animal models. One recent approach taken to investigate the changes associated with NF1 tumor formation is the development of the Nf1:p53 mouse tumor model. Here, we examined a series of tumor cell lines derived from Nf1:p53 mice for their expression of EGFR family members. Immunoblotting analyses revealed that 23 of the 24 cell lines examined express the EGFR, and 24 of 24 express the related tyrosine kinase erbB2, whereas erbB3 was detected in only 6 of 24. All of the cell lines expressing EGFR responded to epidermal growth factor (EGF) by activation of the downstream signaling pathways, mitogen-activated protein (MAP)/extracellular signal-regulated kinase kinase/MAP kinase, and phosphatidylinositol 3'-kinase (PI3k)/AKT. Growth of the cell lines was greatly stimulated by EGF in vitro and could be blocked by an antagonist of the EGFR. In addition, inhibition of the PI3k pathway potently inhibited the EGF-dependent growth of these cell lines, whereas inhibition of the MAP/extracellular signal-regulated kinase kinase/MAP kinase pathway had more limited effects. We conclude that EGFR expression is a common feature of the Nf1:p53 tumor cell lines and that inhibition of this molecule or its downstream target PI3k, may be useful in the treatment of NF1-related malignancies.
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PMID:Epidermal growth factor receptor signaling pathways are associated with tumorigenesis in the Nf1:p53 mouse tumor model. 1215 62

Although the understanding of how toxicants alter cardiac ion-channel function has matured rapidly over the past 20-30 yr, little is known about how xenobiotics may alter the signaling pathways of cardiac myocyte growth and death. Signaling molecules and pathways responsible for the growth of cardiac myocytes include the mitogen-activated protein kinases (MAPKs), janus kinase-signal transducer and activator of transcription (JAK-STATs), nuclear receptor signaling, calcineurin, and the mobilization of free calcium. Signaling molecules and pathways responsible for programmed cardiac myocyte death include the death receptors, mitochondrial proteins, p53 tumor suppressor protein, ceramide signaling, and caspases. Overlap or "crosstalk" between the various growth and death pathways in the myocardium is evident, and these pathways likely exist in a delicate balance where, for example, slight reductions in growth signaling may favor pathways leading to cardiac myocyte apoptosis. Several classical cardiotoxicants are now known to alter signaling pathways in cardiac myocytes; however, the significance of these effects is not entirely clear. Furthermore, xenobiotics that alter the interstitium or extracellular matrix, or both, may significantly alter signaling pathways in cardiac myocytes. The goal of this review is to summarize current findings regarding the interaction of xenobiotics with myocardial signal transduction pathways in the hope of stimulating new insights and highlighting important areas for future research.
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PMID:Interaction of xenobiotics with myocardial signal transduction pathways. 1218 77


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