Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0376358 (prostate cancer)
 59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Autocrine production of transforming growth factor alpha and overexpression of the epidermal growth factor receptor (EGFR) may contribute to androgen-independent prostatic cancer growth at both primary and metastatic sites. Previously, we showed that human EGFR-blocking monoclonal antibody mAb225 inhibited the growth of DU145 human prostatic cancer cells. Here we explore the hypothesis that mAb225 may act by interfering with cell cycle traversal in these cells. Treatment with mAb225 induced G1 arrest, which was accompanied by a marked decrease in CDK2-, cyclin A-, and cyclin E-associated histone H1 kinase activities, and a sustained increase in cell cycle inhibitor p27KIP1. The increased p27KIP1 levels were attributable to elevation of both transcription and translation. CDK2 associated with p27KIP1 was increased in mAb225-treated DU145 cells. The retinoblastoma-related protein p130 remained hypophosphorylated in these retinoblastoma-negative cells. These studies demonstrate that the antiproliferative effect of EGFR blockade in DU145 cells may be mediated by up-regulation of p27KIP1 at both the mRNA and protein levels.
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PMID:Anti-epidermal growth factor receptor monoclonal antibody 225 up-regulates p27KIP1 and induces G1 arrest in prostatic cancer cell line DU145. 870 5

Growth of prostatic epithelial cells is androgen-dependent; however, the mechanism of androgen action on cell growth is not well defined. We investigated whether androgen-dependent prostatic epithelial cell growth is mediated by androgen regulation of expression of genes controlling cell cycle progression. For this purpose, we used an androgen-dependent prostatic cancer cell line, LNCaP-FGC, as an in vitro model. We found that expression of CDK2 and CDK4 genes were up-regulated within hours of androgen treatment as detected in Northern and Western blot analyses. Kinase assay also confirmed that there was increased CDK2 kinase activity upon androgen stimulation. Moreover, androgen down-regulated expression of the cyclin-dependent kinase inhibitor p16 (MTS1, CDKN2) gene. The overall effects of these androgen actions result in an increased cyclin-dependent kinase activity and stimulation of the cell to enter S phase of the cell cycle, thereby enhancing cell proliferation. In contrast, an androgen-independent PC-3 cell line lost its response to androgen stimulation, and higher basal levels of CDK2, CDK4, and p16 genes were constitutively expressed in PC-3 cells. Collectively, these data suggest a possible signaling pathway of androgen in stimulating cell growth. These results also imply that in androgen-dependent prostate cancer, increased androgen receptor (AR) activity, resulting from AR gain-of-function mutations, AR gene amplification, or AR gene overexpression, malignantly stimulates proliferation of prostatic epithelial cells and constitutes one possible mechanism of androgen-dependent tumorigenesis.
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PMID:Regulation of androgen-dependent prostatic cancer cell growth: androgen regulation of CDK2, CDK4, and CKI p16 genes. 937 62

1Alpha,25-dihydroxyvitamin D3 (1,25 D), the most active metabolite of vitamin D3, exerts antiproliferative and prodifferentiating effects on some human prostate cancer cell lines. We previously reported an inverse relationship between functional vitamin D receptor (VDR) levels and antiproliferative response to 1,25 D in two human prostate cancer cell lines, LNCaP and ALVA 31. Although LNCaP cells are far more sensitive to growth inhibition by 1,25 D than ALVA 31 cells, LNCaP express approximately half the number of VDR as ALVA 31. Two other human prostate cancer cell lines studied, PC3 and DU145, express lower levels of functional VDR and are relatively insensitive to growth inhibition by 1,25 D. In this report, we investigated potential mechanisms of the variable antiproliferative activity of 1,25 D. In PC3 cells stably expressing VDR [PC3(VDR)] at levels comparable to LNCaP, 1,25 D treatment resulted in only moderate growth inhibition. These results further support the contention that VDR expression, although required, is not sufficient for maximal growth suppression by 1,25 D, as is exhibited by LNCaP cells. We did not detect 1,25 D-mediated DNA fragmentation after 4 days of 1,25 D treatment in either LNCaP or ALVA 31 cells. This result suggests that variability in 1,25 D sensitivity does not derive from differences in the capacity of these cells to undergo apoptosis in response to 1,25 D. Flow cytometry of propidium iodine-stained cells revealed that 48 h 1,25 D treatment of LNCaP cells resulted in a 2-fold decrease of cells in G2/M plus S phases and accumulation of LNCaP cells in the G1/G0 phase. This effect persisted for 72 h after 1,25 D removal. In contrast, 1,25 D did not significantly alter the cell cycle distribution of ALVA 31 or PC3(VDR) cells. Consistent with accumulation of cells in G1/G0, 1,25 D treatment of LNCaP cells resulted in decreased retinoblastoma protein phosphorylation, repressed E2F transcriptional activity, increased levels of the cyclin-dependent kinase (CDK) inhibitor p21(WAF1, CIP1), and decreased CDK2 activity. However, p21 messenger RNA levels were not altered, suggesting translational or posttranslational regulation of p21 by 1,25 D. In contrast, p21 was not detected in ALVA 31 or PC3(VDR) and was not induced by 1,25 D, consistent with the failure of 1,25 D to influence cell cycle distribution in these cells. These results suggest that variability in sensitivity to the antiproliferative effects of 1,25 D among prostate cancer cells is dependent, at least in part, on the integrity of the retinoblastoma pathway and in particular on p21 expression and 1,25 D regulation of CDK2 activity.
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PMID:Antiproliferative effect of 1alpha,25-dihydroxyvitamin D3 in human prostate cancer cell line LNCaP involves reduction of cyclin-dependent kinase 2 activity and persistent G1 accumulation. 949 54

Prostate cancer (PCA) is the most common nonskin malignancy and the second leading cause of cancer deaths in United States males. One practical and translational approach to control PCA is to define a mechanism-based anticarcinogenic agent(s). Recently, we showed that silymarin, a flavonoid antioxidant isolated from milk thistle, possesses exceptionally high to complete protective effects against experimentally induced tumorigenesis. Because the epidermal growth factor receptor (erbB1) and other members of the erbB family have been shown to play important roles in human PCA, efforts should be directed to identify inhibitors of this pathway for PCA intervention. In this study, we assessed whether silymarin inhibits erbB1 activation and associated downstream events and modulates cell cycle regulatory proteins and progression, leading to growth inhibition of human prostate carcinoma DU145 cells. Treatment of serum-starved cells with silymarin resulted in a significant inhibition of transforming growth factor alpha-mediated activation of erbB1 but no change in its protein levels. Silymarin treatment of cells also resulted in a significant decrease in tyrosine phosphorylation of an immediate downstream target of erbB1, the adapter protein SHC, together with a decrease in its binding to erbB1. In the studies analyzing cell cycle regulatory molecules, silymarin treatment of cells also resulted in a significant induction of cyclin-dependent kinase inhibitors (CDKIs) Cip1/p21 and Kip1/p27, concomitant with a significant decrease in CDK4 expression, but no change in the levels of CDK2 and CDK6 and their associated cyclins E and D1, respectively. Cells treated with silymarin also showed an increased binding of CDKIs with CDKs, together with a marked decrease in the kinase activity of CDKs and associated cyclins. In additional studies, treatment of cells grown in 10% serum with anti-epidermal growth factor receptor monoclonal antibody clone 225 or different doses of silymarin also resulted in significant inhibition of constitutive tyrosine phosphorylation of both erbB1 and SHC but no change in their protein levels. Furthermore, whereas silymarin treatment resulted in a significant increase in the protein levels of both Cip1/p21 and Kip1/p27, monoclonal antibody 225 showed an increase only in Kip1/p27. These findings suggest that silymarin also inhibits constitutive activation of erbB1 and that the observed effect of silymarin on an increase in CDKI protein levels is mediated via inhibition of erbB1 activation only in the case of Kip1/p27; however, additional pathways independent of inhibition of erbB1 activation are possibly responsible for the silymarin-caused increase in Cip1/p21 in DU145 cells. In other studies, silymarin treatment also induced a G1 arrest in the cell cycle progression of DU145 cells and resulted in a highly significant to complete inhibition of both anchorage-dependent and anchorage-independent growth of DU145 cells in a dose- and time-dependent manner. Taken together, these results suggest that silymarin may exert a strong anticarcinogenic effect against PCA and that this effect is likely to involve impairment of erbB1-SHC-mediated signaling pathway, induction of CDKIs, and a resultant G1 arrest.
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PMID:A flavonoid antioxidant, silymarin, inhibits activation of erbB1 signaling and induces cyclin-dependent kinase inhibitors, G1 arrest, and anticarcinogenic effects in human prostate carcinoma DU145 cells. 958 34

Reduction in serum prostate-specific antigen (PSA) levels has been proposed as an endpoint biomarker for hormone-refractory human prostate cancer intervention. We examined whether a flavonoid antioxidant silibinin (an active constituent of milk thistle) decreases PSA levels in hormone-refractory human prostate carcinoma LNCaP cells and whether this effect has biological relevance. Silibinin treatment of cells grown in serum resulted in a significant decrease in both intracellular and secreted forms of PSA concomitant with a highly significant to complete inhibition of cell growth via a G1 arrest in cell cycle progression. Treatment of cells grown in charcoal-stripped serum and 5alpha-dihydrotestosterone showed that the observed effects of silibinin are those involving androgen-stimulated PSA expression and cell growth. Silibinin-induced G1 arrest was associated with a marked decrease in the kinase activity of cyclin-dependent kinases (CDKs) and associated cyclins because of a highly significant decrease in cyclin D1, CDK4, and CDK6 levels and an induction of Cip1/p21 and Kip1/p27 followed by their increased binding with CDK2. Silibinin treatment of cells did not result in apoptosis and changes in p53 and bcl2, suggesting that the observed increase in Cip1/p21 is a p53-independent effect that does not lead to an apoptotic cell death pathway. Conversely, silibinin treatment resulted in a significant neuroendocrine differentiation of LNCaP cells as an alternative pathway after Cip1/p21 induction and G1 arrest. Together, these results suggest that silibinin could be a useful agent for the intervention of hormone-refractory human prostate cancer.
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PMID:Silibinin decreases prostate-specific antigen with cell growth inhibition via G1 arrest, leading to differentiation of prostate carcinoma cells: implications for prostate cancer intervention. 1037 42

Prostate cells are dependent on androgen for proliferation, but during tumor progression prostate cancer cells achieve independence from the androgen requirement. We report that androgen withdrawal fails to inhibit cell cycle progression or influence the expression of cyclin-dependent kinase (CDK)/cyclins in androgen-independent prostate cancer cells, indicating that these cells signal for cell cycle progression in the absence of androgen. However, phosphorylation of the retinoblastoma tumor suppressor protein (RB) is still required for G1-S progression in androgen-independent cells, since the expression of constitutively active RB (PSM-RB) or p16ink4a caused cell cycle arrest and mimicked the effects of androgen withdrawal on downstream targets in androgen-dependent LNCaP cells. Since Ras is known to mediate mitogenic signaling to RB, we hypothesized that active V12Ras would induce androgen-independent cell cycle progression in LNCaP cells. Although V12Ras was able to stimulate ERK phosphorylation and induce cyclin D1 expression in the absence of androgen, it was not sufficient to promote androgen-independent cell cycle progression. Similarly, ectopic expression of CDK4/cyclin D1, which stimulated RB phosphorylation in the presence of androgen, was incapable of inactivating RB or driving cell cycle progression in the absence of androgen. We show that androgen regulates both CDK4/cyclin D1 and CDK2 complexes to inactivate RB and initiate cell cycle progression. Together, these data show that androgen independence is achieved via deregulation of the androgen to RB signal, and that this signal can only be partially initiated by the Ras pathway in androgen-dependent cells.
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PMID:Differential requirements for ras and the retinoblastoma tumor suppressor protein in the androgen dependence of prostatic adenocarcinoma cells. 1093 90

There is an increasing interest in identifying potent cancer preventive and therapeutic agents against prostate cancer (PCA). In a recent study, we showed that a polyphenolic fraction isolated from grape seeds (hereafter referred to as GSP) that is substantially rich in antioxidant procyanidins exerts exceptionally high preventive effects against tumorigenesis in a murine skin model. In the present study, we investigated the anticarcinogenic effect of GSP against PCA by employing DU145 human prostate carcinoma cells. GSP treatment (10-100 microg/mL doses for 2-6 d) of cells resulted in a highly significant (P < 0.01-0.001) inhibition of cell growth in both dose- and time-dependent manner. Compared with the vehicle, 2 d of GSP treatment resulted in 27, 39, and 76% growth inhibition at 50, 75, and 100 microg/mL doses, respectively, whereas 28-97% and 12-98% inhibition was evident at 10-100 microg/mL doses of GSP after 4 and 6 d of treatment, respectively. These doses of GSP also resulted in dose- and time-dependent cell death (6-50%, P <0.1-0. 001) that was later characterized as apoptotic death. In molecular mechanistic studies, treatment of DU145 cells with GSP at 25-75 microg/mL doses for 24, 48, and 72 h resulted in 77-88%, 65-93%, and 38-98% reduction, respectively (P < 0.001), in phospho-extracellular signal-regulated protein kinase (ERK) 1 and 78%, 19-76%, and 63-71% reduction (P < 0.1-0.001) in phospho-ERK2 levels, respectively. In other studies, similar doses of GSP showed up to 1.9-fold increases in Cip1/p21 and a significant (P < 0.001) decrease in cyclin-dependent kinase (CDK) 4 (up to 90% decrease), CDK2 (up to 50% decrease), and cyclin E (up to 60% decrease). GSP treatment of DU145 cells also resulted in a significant (P < 0.001) G1 arrest in cell-cycle progression in a dose-dependent manner. The growth-inhibitory and cell-death effects of GSP were also observed in another human PCA line, LNCaP. Together, these results suggest that GSP may exert strong anticarcinogenic effect against PCA and that this effect possibly involves modulation of mitogenic signaling and cell-cycle regulators and induction of G1 arrest, cell-growth inhibition, and apoptotic death. Mol. Carcinog. 28:129-138, 2000.
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PMID:Anticarcinogenic effect of a polyphenolic fraction isolated from grape seeds in human prostate carcinoma DU145 cells: modulation of mitogenic signaling and cell-cycle regulators and induction of G1 arrest and apoptosis. 1094 29

Prostate cancer (PCA) is the most common invasive malignancy and leading cause (after lung) of cancer deaths in males. Since PCA is initially androgen-dependent, strategies are targeted toward androgen depletion for its control. However, tumor re-growth mostly occurs following this modality, and is androgen-independent. A loss of functional androgen receptor and an enhanced expression of growth factor receptors (e.g. erbB family members) and associated ligands have been shown to be the causal genetic events in PCA progression. These genetic alterations lead to an epigenetic mechanism where a feed-back autocrine loop between membrane receptor (e.g. epidermal growth factor receptor [erbB1] and associated ligand (e.g. transforming growth factor-alpha) results in an enhanced activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) as an essential component of the uncontrolled growth of PCA at an advanced and androgen-independent stage. Together, we rationalized that inhibiting these epigenetic events would be useful in controlling advanced PCA growth. Dietary polyphenolic flavonoids and isoflavones are being studied extensively as cancer-preventive and interventive agents. Therefore, we focused our attention on silymarin, genistein, and epigallocatechin 3-gallate (EGCG), present in milk thistle, soy beans, and green tea, respectively. The effect of these agents was assessed on the erbB1-Shc-ERK1/2 signal transduction pathway, cell cycle regulatory molecules, and cell growth and death. In androgen-independent human prostate carcinoma DU145 cells, silymarin, genistein, and EGCG resulted in a significant to complete inhibition of transforming growth factor-alpha-caused activation of membrane receptor erbB1 followed by inhibition of downstream cytoplasmic signaling target Shc activation and a decrease in its binding with erbB1, without an alteration in their protein expression. Silymarin and genistein also inhibited ERK1/2 activation, suggesting that these agents impair the activation of erbB1-Shc-ERK1/2 signaling in DU145 cells. In the case of EGCG, a further increase in ERK1/2 activation was observed that was related to its pro-oxidant and apoptotic activities. Silymarin, genistein, and EGCG also resulted in a significant induction of Cip1/p21 and Kip1/p27 and a decrease in cyclin-dependent kinase (CDK) 4, but a moderate inhibition of CDK2, cyclin D1, and cyclin E was observed. An enhanced level of Cip1/p21 and Kip1/27 also led to an increase in their binding to CDK4 and CDK2. Treatment of cells with silymarin, genistein, and EGCG also resulted in strong cell growth inhibition at lower doses, and complete inhibition at higher doses. In contrast to silymarin, higher doses of genistein also showed cell death. A more profound cytotoxic effect was observed in the case of EGCG, with strong cell death at lower doses and complete loss of viability at higher doses. Together, these results suggest that cell signaling and regulators of cell cycle are potential epigenetic molecular targets for prostate cancer prevention by dietary agents. More studies, therefore, are needed with these agents to explore their anticarcinogenic potential against human prostate cancer.
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PMID:Cell signaling and regulators of cell cycle as molecular targets for prostate cancer prevention by dietary agents. 1100 41

Treatment with millimolar concentrations of phenylacetate (PA), results in cytostasis, growth inhibition and differentiation in several human cancer cell lines, including prostate cancer. However, the molecular basis of PA-induced biological effects has not been elucidated in detail. In this study we focused on its influence on cell cycle events and investigated alterations in cell cycle regulators in androgen-dependent and independent human prostate cancer cell lines. FACS analysis revealed that suppression of cell growth by PA was due to G1 arrest, with reduced phosphorylation of the retinoblastoma protein (pRb) and CDK2 activity. Expression of p27Kip1 was increased, while p21Cip1, p53, cyclinD1 and cyclin E were not affected by PA. Binding of p27Kip1 to CDK2 increased significantly following treatment with PA. Furthermore, antisense p27Kip1 oligonucleotide attenuated the inhibitory effect of PA. Our results suggested that p27Kip1 might be a critical target in PA-mediated cell growth arrest in prostate cancer cells playing a key role in CDK2 inactivation followed by hypophosphorylation of pRB and subsequent G1 cell cycle arrest.
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PMID:p27Kip1 is the key mediator of phenylacetate induced cell cycle arrest in human prostate cancer cells. 1106 25

Previous studies have shown that dietary or pharmacological methionine restriction inhibits growth of human prostate cancer cells in vitro or as xenografts in mice. We undertook the present studies to clarify the molecular mechanisms by which methionine restriction inhibits prostate cancer cell growth. We found that PC-3 and DU 145 cells stopped proliferating within six days in growth medium containing homocysteine in place of methionine. In contrast, proliferation of LNCaP cells was only partially inhibited by the absence of methionine. Using flow cytometry, we found that methionine restriction caused PC-3 cells to arrest in all phases of the cell cycle, but predominantly in the G2/M phase, whereas LNCaP cells accumulated exclusively in the G1 phase. Methionine restriction led to accumulation of the cyclin-dependent kinase inhibitors p21 and p27, as determined by Western blot analysis, and inhibited the enzymatic activities of the cyclin-dependent kinases CDK2 and cdc2, as determined by an in vitro kinase assay: However, methionine restriction had little or no effect on CDK2 or cdc2 protein levels. Methionine restriction also induced PC-3 cells to undergo apoptosis, as indicated by the appearance of a typical nucleosomal ladder on gel electrophoresis of genomic DNA. We conclude that methionine restriction has potential as a novel treatment strategy for prostate cancer.
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PMID:Molecular mechanisms of cell cycle block by methionine restriction in human prostate cancer cells. 1134 Oct 37


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