نورا
09-01-2007, 03:47 AM
بلييز ضروري مساعد فترجمة ذي النصوص الترجمه الاليكترونيه مو نافعه ابد
ابي العام بلييز مو حرفيا
<TT>Abstract </TT>
<TT>The tumor microenvironment is best characterized as a fluctuation of hypoxia and nutrient deprivation, which leads to epigenetic and genetic adaptation of clones and increased invasiveness and metastasis. In turn, these hypoxic adaptations make the tumors more difficult to treat and confer increased resistance to current therapies. Part of this adaptation is the regulation of gene products in response to hypoxia. Many of these hypoxia-regulated genes are mediated by the hypoxia-inducible factor 1 (HIF-1) complex, which is composed of a heterodimer pair of HIF-1 and HIF-1ß. This heterodimer binds to the promoter of hypoxia-responsive genes, while interacting with other transcription factors, such as p300, signal and transducer of transcription 3, and Redox effector factor 1/apurinic/apyrimidinic endonuclease. HIF-1 levels itself can be regulated by hypoxia transcriptionally and post-translationally through ubiquitination; but the magnitude of the response is modulated by several other pathways, including free radicals that affect crosstalk with HIF-1/HIF-1ß transcriptional activities. HIF-1 has emerged as an important transcription factor in breast cancer and prostate cancer biology, and is expressed in the early stages of mammary and prostate carcinogenesis. Its expression is correlated with diagnostic and prognostic indicators for early relapse and metastatic disease, thus making HIF-<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:metricconverter w:st="on" ProductID="1 a">1 a</st1:metricconverter> potential prognostic biomarker in proteomic assessments of breast and prostate cancers. The importance of HIF-<st1:metricconverter w:st="on" ProductID="1 in">1 in</st1:metricconverter> tumor progression makes it a logical target for chemoprevention strategies in patients at higher genetic risk of breast and prostate cancer with Cox 2 inhibitors or 2-methoxyestradiol, as well as a target for new approaches to inhibiting angiogenesis. The crosstalk between estrogen signaling pathways and HIF-1 is still not fully defined in breast cancer, but downstream estrogen receptor signaling may be a candidate for estrogen modulation of HIF-1 levels. In prostate cancer, androgens upregulate HIF-1 through androgen-regulated autocrine receptor tyrosine kinase receptor signaling. This review will put into perspective the role of HIF-<st1:metricconverter w:st="on" ProductID="1 in">1 in</st1:metricconverter> endocrine oncology and present new data on HIF-1 signaling and the potential for targeted therapies, including combinatory hormonal therapies. </TT>
<TT>__________________</TT><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
<TT>HIF-1 and epigenetic factors </TT>
<TT>Tumor hypoxia itself is a strong epigenetic factor for upregulation of HIF-1 protein. Several groups have shown that hypoxia, in addition to inhibiting the PHDs and inhibiting HIF-1, generates free oxygen-free radicals. In vitro, epigenetically oxygen-free radicals can stabilize HIF-1 protein (Kaelin 2005). Various free radical generating catechol estrogens (CEs) are also capable of inducing HIF-1 and VEGF (Muzandu et al. 2005). One of these CEs, 4-hydroxyestradiol (4-OHE2), goes through redox cycling producing reactive oxygen species, superoxide (O2*–), CE semiquinone, and catechol quinone (Muzandu et al. 2005). This epigenetic induction is sensitive to PI3K inhibitors, which suggest that 4-OHE2 might regulate HIF-1 and VEGF through the PI3K/Akt/FRAP pathway, not the MEK pathway (Gao et al. 2002). </TT>
<TT>A major question in the clinic is the actual epigenetic contribution of oxygen-free radicals to HIF-1 levels in tumor cells (Zhang et al. 1999). HIF-prolyl hydro-xylases regulate degradation of HIF-1; these hydro-xylases require 2-oxoglutarate, Fe2+, ascorbate, and molecular oxygen for enzymatic activity. All of these components are important to the intracellular concentration of oxygen-free radicals that effect PHD enzymatic actions on HIF-1 </TT>
<TT>__________________________________________ </TT>
<o:p></o:p>
ابي العام بلييز مو حرفيا
<TT>Abstract </TT>
<TT>The tumor microenvironment is best characterized as a fluctuation of hypoxia and nutrient deprivation, which leads to epigenetic and genetic adaptation of clones and increased invasiveness and metastasis. In turn, these hypoxic adaptations make the tumors more difficult to treat and confer increased resistance to current therapies. Part of this adaptation is the regulation of gene products in response to hypoxia. Many of these hypoxia-regulated genes are mediated by the hypoxia-inducible factor 1 (HIF-1) complex, which is composed of a heterodimer pair of HIF-1 and HIF-1ß. This heterodimer binds to the promoter of hypoxia-responsive genes, while interacting with other transcription factors, such as p300, signal and transducer of transcription 3, and Redox effector factor 1/apurinic/apyrimidinic endonuclease. HIF-1 levels itself can be regulated by hypoxia transcriptionally and post-translationally through ubiquitination; but the magnitude of the response is modulated by several other pathways, including free radicals that affect crosstalk with HIF-1/HIF-1ß transcriptional activities. HIF-1 has emerged as an important transcription factor in breast cancer and prostate cancer biology, and is expressed in the early stages of mammary and prostate carcinogenesis. Its expression is correlated with diagnostic and prognostic indicators for early relapse and metastatic disease, thus making HIF-<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:metricconverter w:st="on" ProductID="1 a">1 a</st1:metricconverter> potential prognostic biomarker in proteomic assessments of breast and prostate cancers. The importance of HIF-<st1:metricconverter w:st="on" ProductID="1 in">1 in</st1:metricconverter> tumor progression makes it a logical target for chemoprevention strategies in patients at higher genetic risk of breast and prostate cancer with Cox 2 inhibitors or 2-methoxyestradiol, as well as a target for new approaches to inhibiting angiogenesis. The crosstalk between estrogen signaling pathways and HIF-1 is still not fully defined in breast cancer, but downstream estrogen receptor signaling may be a candidate for estrogen modulation of HIF-1 levels. In prostate cancer, androgens upregulate HIF-1 through androgen-regulated autocrine receptor tyrosine kinase receptor signaling. This review will put into perspective the role of HIF-<st1:metricconverter w:st="on" ProductID="1 in">1 in</st1:metricconverter> endocrine oncology and present new data on HIF-1 signaling and the potential for targeted therapies, including combinatory hormonal therapies. </TT>
<TT>__________________</TT><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
<TT>HIF-1 and epigenetic factors </TT>
<TT>Tumor hypoxia itself is a strong epigenetic factor for upregulation of HIF-1 protein. Several groups have shown that hypoxia, in addition to inhibiting the PHDs and inhibiting HIF-1, generates free oxygen-free radicals. In vitro, epigenetically oxygen-free radicals can stabilize HIF-1 protein (Kaelin 2005). Various free radical generating catechol estrogens (CEs) are also capable of inducing HIF-1 and VEGF (Muzandu et al. 2005). One of these CEs, 4-hydroxyestradiol (4-OHE2), goes through redox cycling producing reactive oxygen species, superoxide (O2*–), CE semiquinone, and catechol quinone (Muzandu et al. 2005). This epigenetic induction is sensitive to PI3K inhibitors, which suggest that 4-OHE2 might regulate HIF-1 and VEGF through the PI3K/Akt/FRAP pathway, not the MEK pathway (Gao et al. 2002). </TT>
<TT>A major question in the clinic is the actual epigenetic contribution of oxygen-free radicals to HIF-1 levels in tumor cells (Zhang et al. 1999). HIF-prolyl hydro-xylases regulate degradation of HIF-1; these hydro-xylases require 2-oxoglutarate, Fe2+, ascorbate, and molecular oxygen for enzymatic activity. All of these components are important to the intracellular concentration of oxygen-free radicals that effect PHD enzymatic actions on HIF-1 </TT>
<TT>__________________________________________ </TT>
<o:p></o:p>