Journal of cellular biochemistry
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Review
Androgen receptor: a key molecule in the progression of prostate cancer to hormone independence.
Despite earlier detection and recent advances in surgery and radiation, prostate cancer is second only to lung cancer in male cancer deaths in the United States. Hormone therapy in the form of medical or surgical castration remains the mainstay of systemic treatment in prostate cancer. Over the last 15 years with the clinical use of prostate specific antigen (PSA), there has been a shift to using hormone therapy earlier in the disease course and for longer duration. ⋯ These growth factors working through receptor tyrosine kinase pathways may promote AR activation and growth in low androgen environments. The clinical significance of these AR alterations in the development and progression of androgen-independent prostate cancer remains to be determined. Understanding the changes in AR signaling in the evolution of androgen-independent prostate cancer will be key to the development of more effective hormone therapy.
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(-)-Epigallocatechin-3-gallate (EGCG) potently inhibits cell proliferation and suppresses tumor growth both in vitro and vivo, but little is known regarding the cell cycle regulatory proteins mediating these effects. This study investigated the effects of EGCG and other catechins on the cell cycle progression. DNA flow cytometric analysis indicated that 30 microM of EGCG blocked cell cycle progression at G1 phase in asynchronous MCF-7 cells. ⋯ The level of p21 mRNA also increased under the same conditions. In addition, EGCG also increased the expression of the Cdk inhibitor p27 protein within 6 h after EGCG treatment. These results suggest that EGCG either exerts its growth-inhibitory effects through modulation of the activities of several key G1 regulatory proteins such as Cdk2 and Cdk4 or mediates the induction of Cdk inhibitor p21 and p27.
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Lactoferrin inhibits cell proliferation and suppresses tumor growth in vivo. However, the molecular mechanisms underlying these effects remain unknown. In this in vitro study, we demonstrate that treatment of breast carcinoma cells MDA-MB-231 with human lactoferrin induces growth arrest at the G1 to S transition of the cell cycle. ⋯ Additional experiments with synchronized cells by serum depletion confirm the anti-proliferative activity of human lactoferrin. These effects of lactoferrin occur through a p53-independent mechanism both in MDA-MB-231 cells and other epithelial cell lines such as HBL-100, MCF-7, and HT-29. These findings demonstrate that lactoferrin induces growth arrest by modulating the expression and the activity of key G1 regulatory proteins.
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Using the combination of a cDNA library prepared from membrane glucocorticoid (mGR)-enriched S-49 cells and a mouse leukocyte genomic library, we have cloned a 7.3 kb full-length glucocorticoid receptor 1A cDNA. Primer extension, 5'RACE, and long distance PCR identified the transcription start site as being located at 1026 bp from the ATG codon. The first 1,013 nucleotides (nts) of the full length sequence constitute 5' UTR sequence (exon 1), the next 2349 bp, the coding region, and the last 3,907 bp, the 3'UTR. ⋯ Western blot analysis compared the molecular weight of in vitro translation products from the cloned 1A cDNA with partially purified cellular mGR. Both preparations contained the novel 150 KD and the 94 KD classical GR peptides, suggesting that transcript 1A encodes both receptor forms. Transfection of mGR-less and glucocorticoid lysis-resistant AtT-20 and HL-60 cells with full-length GR 1A cDNA imparted both mGR expression and glucocorticoid lysis-sensitivity to these cells.
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Opioids decrease cell proliferation in different systems including breast, prostate, lung, kidney, and intestine, through an interaction with opioid as well as other membrane-receptor systems (somatostatin, cholinergic), through an unidentified mechanism. Recently, we have reported an interaction of taxol with opioid membrane sites (BBRC 235, 201-204, 1997), and an involvement of opioids to the modification of actin cytoskeleton in renal OK cells (J Cell Biochem. [19981 70:60-69), indicating a possible action of the opioid effect. In the present work, we have examined the effect of two general opioid agonists (ethylketocyclazocine and etorphine) on the cell cycle, in human breast cancer T47D cells, as well as a possible modification of the cellular cytoskeleton under their action, in order to explain the antiproliferative effect of these agents. ⋯ Furthermore, the observed tubulin-opioid interaction by opioids provides a possible explanation of the arrest at the G2/M phase of T47D cells under opioid treatment. Nevertheless, although the observed interaction of opioids with cytoskeletal elements gives a plausible answer of the antiproliferative effects of the agents, this might not be the only action of these agents in cell proliferation. Other, direct or indirect, genomic actions, which which remains to be elucidated, might be taken into consideration.