Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molecular mechanism of androgen-independent growth of prostate cancer after androgen ablation was explored in LNCaP cells. An androgen-dependent clonal subline of the LNCaP human prostate carcinoma cell line, LNCaP 104-S, progressed to a slow growing stage (104-R1) and then to a faster growing stage (104-R2) during more than 2 yr of continuous culture in the absence of androgen. Androgen-induced proliferation of 104-S cells is inhibited by the antiandrogen Casodex, while proliferation of 104-R1 and 104-R2 cells is unaffected by Casodex. This indicates that proliferation of 104-R1 and 104-R2 cells is not supported by low levels of androgen in the culture medium. Compared with LNCaP 104-S cells, both 104-R1 and 104-R2 cells express higher basal levels of androgen receptor (AR), and proliferation of these two cell lines is paradoxically repressed by androgen. After continuous passage in androgen-containing medium, 104-R1 cells reverted back to an androgen-dependent phenotype. The mechanism of androgenic repression of 104-R1 and 104-R2 sublines was further evaluated by examining the role of critical regulatory factors involved in the control of cell cycle progression. At concentrations that repressed growth, androgen transiently induced the expression of the cyclin-dependent kinase (cdk) inhibitor p21waf1/cip1 in 104-R1 cells, while expression of the cdk inhibitor p27Kip1 was persistently induced by androgen in both 104-R1 and 104-R2 cells. Induced expression of murine p27Kip1 in 104-R2 cells resulted in G1 arrest. Specific immunoprecipitates of Cdk2 but not Cdk4 from androgen-treated 104-R1 cells contained both p21waf1/cip1 and p27Kip1. This observation was confirmed by in vitro assay of histone H1 and Rb (retinoblastoma protein) phosphorylation by the proteins associated with the immune complex. Furthermore, inhibition of Cdk2 activity correlated with the accumulation of p27Kip1 and not p21waf1/cip1. From these results we conclude that androgenic repression of LNCaP 104-R1 and 104-R2 cell proliferation is due to the induction of p27Kip1, which in turn inhibits Cdk2, a factor critical for cell cycle progression and proliferation.
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PMID:Progression of LNCaP prostate tumor cells during androgen deprivation: hormone-independent growth, repression of proliferation by androgen, and role for p27Kip1 in androgen-induced cell cycle arrest. 965 99

The human prostate cancer (CaP) xenograft, CWR22, mimics human CaP. CWR22 grows in testosterone-stimulated nude mice, regresses after castration, and recurs after 5-6 months in the absence of testicular androgen. Like human CaP that recurs during androgen deprivation therapy, the recurrent CWR22 expresses high levels of androgen receptor (AR). Immunohistochemical, Western, and Northern blot analyses demonstrated that AR expression in the androgen-independent CWR22 is similar to AR expression in the androgen-dependent CWR22 prior to castration. Expression of prostate-specific antigen and human kallikrein-2 mRNAs, two well-characterized androgen-regulated genes in human CaP, was androgen dependent in CWR22. Despite the absence of testicular androgen, prostate-specific antigen and human kallikrein-2 mRNA levels in recurrent CWR22 were higher than the levels in regressing CWR22 tumors from 12-day castrate mice and similar to those in the androgen-stimulated CWR22. Other AR-regulated genes followed a similar pattern of expression. Differential expression screening identified androgen regulation of alpha-enolase and alpha-tubulin as well as other unknown mRNAs. Insulin-like growth factor binding protein-5, the homeobox gene Nkx 3.1, the AR coactivator ARA-70, and cell cycle genes Cdk1 and Cdk2 were androgen regulated in CWR22. In recurrent CWR22, the steady-state levels of all these AR-dependent mRNAs were similar to those in the androgen-stimulated CWR22, despite the absence of testicular androgen. Expression of AR and AR-regulated genes in the androgen-deprived recurrent CWR22 at levels similar to the androgen-stimulated CWR22 suggests that AR is transcriptionally active in recurrent CWR22. Induction of these AR-regulated genes may enhance cellular proliferation in relative androgen absence but through an AR-dependent mechanism. Alternatively, in androgen-independent tumors, induced expression of the AR-regulated gene network might result from a non-AR transcription control mechanism common to these genes.
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PMID:Androgen receptor expression in androgen-independent prostate cancer is associated with increased expression of androgen-regulated genes. 986 29

Low levels of p27Kip1 in primary prostate cancer specimens have been shown to be associated with higher rates of disease recurrence and poor rates of disease-free survival in patients with localized disease. In this study, we provide the first direct evidence showing that dihydrotestosterone (DHT), a major proliferation regulator of prostate cancer, can down-regulate p27Kip1 and stimulate cyclin-dependent kinase-2 (CDK2) activity in established prostate cancer cell lines. We investigated the cooperative effects of DHT and epidermal growth factor (EGF) on the proliferation of androgen-responsive MDA PCa 2a and MDA PCa 2b prostate cancer cells. DHT and EGF each stimulated proliferation of these cells, but exposure of the cells to DHT and EGF together stimulated greater proliferation. Stimulation of cell proliferation by DHT and/or EGF was associated with increased CDK2 activity and a decreased level of p27Kip1. There seems to be a positive feedback stimulation loop between androgen-induced gene transcription and EGF-stimulated signal transduction, as one could stimulate the synthesis of the receptors for the other. Dual blockade of androgen receptor function with the antiandrogen hydroxyflutamide and EGF receptor superfamily-mediated signal transduction with the anti-EGF receptor monoclonal antibody C225 and the anti-HER2 receptor monoclonal antibody Herceptin significantly enhanced growth inhibition of the MDA PCa 2a cells. Our results demonstrate the importance of counteracting both androgen receptors and EGF receptors in the development of novel therapies for prostate cancer.
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PMID:Androgen and epidermal growth factor down-regulate cyclin-dependent kinase inhibitor p27Kip1 and costimulate proliferation of MDA PCa 2a and MDA PCa 2b prostate cancer cells. 1047 2

We have previously reported the identification of seven in vivo phosphorylation sites in the amino-terminal region of the human progesterone receptor (PR). From our previous in vivo studies, it was evident that several phosphopeptides remained unidentified. In particular, we wished to determine whether human PR contains a phosphorylation site in the hinge region, as do other steroid receptors including chicken PR, human androgen receptor, and mouse estrogen receptor. Previously, problematic trypsin cleavage sites hampered our ability to detect phosphorylation sites in large incomplete tryptic peptides. Using a combination of mass spectrometry and in vitro phosphorylation, we have identified six previously unidentified phosphorylation sites in human PR. Using nanoelectrospray ionization mass spectrometry, we have identified two new in vivo phosphorylation sites, Ser(20) and Ser(676), in baculovirus-expressed human PR. Ser(676) is analogous to the hinge site identified in other steroid receptors. Additionally, precursor ion scans identified another phosphopeptide that contains Ser(130)-Pro(131), a likely candidate for phosphorylation. In vitro phosphorylation of PR with Cdk2 has revealed five additional in vitro Cdk2 phosphorylation sites: Ser(25), Ser(213), Thr(430), Ser(554), and Ser(676). At least two of these, Ser(213) and Ser(676), are authentic in vivo sites. We confirmed the presence of the Cdk2-phosphorylated peptide containing Ser(213) in PR from in vivo labeled T47D cells, indicating that this is an in vivo site. Our combined studies indicate that most, if not all, of the Ser-Pro motifs in human PR are sites for phosphorylation. Taken together, these data indicate that the phosphorylation of PR is highly complex, with at least 14 phosphorylation sites.
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PMID:Identification of a phosphorylation site in the hinge region of the human progesterone receptor and additional amino-terminal phosphorylation sites. 1111 Aug 1

The functional and quantitative alterations in cell cycle regulators after androgen depletion in an androgen-dependent cancer cell and the interaction between androgen receptor and cell cycle regulators were examined in order to clarify the initial response of cancer cells to anti-androgen therapy. Fluorescence activated cell sorter analysis (FACS) of androgen-dependent cancer cell line (SC-3) cells cultured with or without 1 nM dihydrotestosterone (DHT) revealed that suppression of cell growth after androgen withdrawal was due to G1 arrest. The protein level of cyclin D1 decreased without any apparent change in the amounts of Cdk2, Cdk4, cyclin E or cyclin A. Among various Cdk inhibitors (CKIs) examined, p27 was upregulated at both mRNA and protein levels 24 h after androgen depletion. On the other hand, cyclin E has been shown to increase the transactivation activity of the human androgen receptor (AR) in the presence of DHT. These results suggest that cell cycle regulators are critical targets in the initial response of androgen-dependent cancer cells to androgen depletion and play a key role in the transcriptional activity of AR.
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PMID:[Clinical role of cell cycle regulators in androgen-dependent cancer cell growth]. 1121 7

Human prostate cancer is initially dependent on androgens for growth, and androgen-dependent cells undergo apoptosis after castration. However, a subset of androgen-responsive cells survives and eventually proliferates in the absence of testicular androgen. The high levels of androgen receptor in both androgen-dependent and recurrent tumors led us to investigate androgen regulation of cell cycle proteins in human prostate cancer using the CWR22 xenograft. Cellular proliferation decreased dramatically in CWR22 tumors after castration. Testosterone propionate (TP) treatment of castrated mice restored cellular proliferation after 24-48 hours. Growth of CWR22 tumors in the absence of testicular androgen recurred several months after castration. CDK1 and CDK2, and cyclin A and cyclin B1 messenger RNAs were decreased 6 days after castration, increased 6-12 hours after TP treatment, and were expressed at high levels in recurrent CWR22 tumors. Coimmunoprecipitated cyclin B1/CDK1 and cyclin D1/CDK4 protein complexes decreased after castration and increased after TP treatment of castrated mice. In addition, CDK1 and CDK2 kinase activities were upregulated by androgen in parallel with hyperphosphorylation of retinoblastoma (Rb) protein. Despite the absence of testicular androgen in recurrent CWR22, the levels of these androgen-regulated cyclin/ CDK protein complexes and hyperphosphorylation of Rb were equal to or greater than in tumors from intact mice. The results indicate that androgen receptor regulates cellular proliferation by control of CDK and cyclins at the transcriptional level and by post-translational modifications that influence cell cycle protein activity.
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PMID:Androgen receptor regulation of G1 cyclin and cyclin-dependent kinase function in the CWR22 human prostate cancer xenograft. 1145 50

Cell-cycle regulatory events associated with inhibition of androgen-dependent cell proliferation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were studied in the human-derived LNCaP cell line. TCDD blocked the G(1) to S transition of LNCaP cells synchronized in G(0)/G(1) when these cells were induced to reinitiate cell-cycle progression by dihydrotestosterone (DHT). Western blot analyses of these cells revealed altered expression levels of G(1) regulatory proteins, including increases in hypophosphorylated retinoblastoma protein and concomitant decreases in cyclin D1. p21(WAF1/CIP1), which is involved in the assembly of cyclin D1/cyclin-dependent kinase-4 complexes, was increased by DHT or TCDD when each compound was administered singly but was reduced to background levels in cells simultaneously treated with DHT and TCDD. Reporter gene assays revealed the presence of several Ah receptor response-element motifs in the promoter and first intron of the p21(WAF1/CIP1) gene that respond to TCDD-mediated Ah receptor activation independently of p53. Transcription studies showed that activation of aryl hydrocarbon receptor blocks androgen-dependent gene induction in LNCaP cells as well as in African green monkey CV-1 cells. These data point to at least two mechanisms whereby TCDD blocks androgen receptor function: 1) by blocking androgen-induced cell proliferation through modulation of the expression and activities of regulatory proteins controlling cell-cycle progression; and 2) by squelching androgen receptor-mediated gene transcription through receptor cross-talk, possibly involving competition for coregulators or by direct protein interaction.
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PMID:2,3,7,8-Tetrachlorodibenzo-p-dioxin blocks androgen-dependent cell proliferation of LNCaP cells through modulation of pRB phosphorylation. 1532 41

We describe the immunohistochemical profile of rare primary squamous carcinoma of the clitoris metastasizing to the bilateral inguinal lymph nodes. Several antigens were assessed immunohistochemically (pRb1, p16INK4A, cyclin D1, cdk4, estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), p53, Ki-67, p27KIP1, PTEN, hMLh1, phospho-AKT, collagen IV, leptin and CD90) in both tumors. All the antibodies applied revealed a staining pattern that is typical of primary and metastatic carcinomas. Cyclin D1-cdk4 complex was overexpressed, whereas there was no p16INK4A immunostaining. Moreover, both tumors expressed positivity for p53 protein, but were negative for estrogen and progesterone receptors. The proliferative activity of cancer, assessed by MIB-1 Proliferative Index, amounted to 25% either for primary or for metastatic tumors. As a conclusion, immunohistochemical assessment of various cell-cycle-associated molecules yield clues as to their possible function during the process of spread of rare neoplasm originating from the clitoris.
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PMID:The immunohistochemical profile of the primary and metastatic carcinoma of the clitoris: a case report. 1616 59

3,3'-Diindolylmethane (DIM) is a potential chemopreventive phytochemical derived from Brassica vegetables. In this study we characterized the effect of DIM on cell cycle regulation in both androgen-dependent LNCaP and androgen receptor negative p53 mutant DU145 human prostate cancer cells. DIM had an anti-proliferative effect on both LNCaP and DU145 cells, as it significantly inhibited [3H]-thymidine incorporation. FACS analysis revealed a DIM-mediated G(1) cell cycle arrest. DIM strongly inhibited the expression of cdk2 and cdk4 protein and increased the expression of the cell cycle inhibitor p27(Kip1) protein in LNCaP and DU145 cells. Promoter deletion studies with p27(Kip1) reporter gene constructs showed that this DIM-mediated increase in p27(Kip1) was dependent on the Sp1 transcription factor. Moreover, using a dominant negative inhibitor of p38 MAPK, we showed that the induction of p27(Kip1) and subsequent G(1) arrest by DIM involve activation of the p38 MAPK pathway in the DU145 cells. Taken together, our results indicate that DIM is able to stop the cell cycle progression of human prostate cancer cells regardless of their androgen-dependence and p53 status, by differentially modulating cell cycle regulatory pathways. The Sp1 and p38 MAPK pathways mediate the DIM cell cycle regulatory effect in DU145 cells.
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PMID:3,3'-Diindolylmethane induces a G(1) arrest in human prostate cancer cells irrespective of androgen receptor and p53 status. 1943 67

Previous studies have suggested that 1,25 dihydroxyvitamin D(3) (1,25(OH)2D3) induces cell cycle arrest and/or apoptosis in prostate cancer cells in vitro, suggesting that vitamin D may be a useful adjuvant therapy for prostate cancer and a chemopreventive agent. Most epidemiological data however shows a weak link between serum 25(OH)D3 and risk of prostate cancer. To explore this dichotomy we have compared tumor progression in the LPB-Tag model of prostate in VDR knock out (VDRKO) and wild type (VDRWT) mice. On the C57BL/6 background LPB-Tag tumors progress significantly more rapidly in the VDRKO mice. VDRKO tumors show significantly higher levels of cell proliferation than VDRWT tumors. In mice supplemented with testosterone to restore the serum levels to the normal range, these differences in tumor progression, and proliferation are abrogated, suggesting that there is considerable cross-talk between the androgen receptor (AR) and the vitamin D axis which is reflected in significant changes in steady state mRNA levels of the AR, PCNA, cdk2 survivin and IGFR1 and 2 genes. These alterations may explain the differences between the in vitro data and the epidemiological studies.
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PMID:Tumor progression in the LPB-Tag transgenic model of prostate cancer is altered by vitamin D receptor and serum testosterone status. 2034 77


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