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

The expression of the CDK inhibitor (CDI) genes p15(INK4B), p16(INK4A), p18 and p21Cip1 was examined in immortalized, non-tumorigenic cell lines derived from human breast epithelium, and in breast carcinoma derived lines. An increase in p16 expression, suggesting loss of pRb function, was recorded in two immortalized lines, and complete absence of p16 mRNA was observed in the third. In contrast, high levels of p21Cip1 mRNA were found in two immortalized lines. In addition to differences in p16 and p21Cipl, variations in the expression of p15 and p18 mRNA were observed between different cell lines. Immortalized A1N4 and HBL100 cells, as well as ER+, MCF-7 carcinoma cells, expressed high levels of p15 mRNA. A1N4, HBL100 cells and highly malignant ER MDA-MB-231 cells expressed high levels of p18 mRNA. Inhibition by genistein indicated that p18 mRNA expression was dependent on cellular tyrosine kinases in these cells. We conclude that the pattern of p15 and p18 mRNA expression was distinct from that of p16 and p21Cip1, suggesting different modes of regulation.
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PMID:Expression of CDK inhibitor genes in immortalized and carcinoma derived breast cell lines. 871 23

The addition of 10 nM staurosporine (ST) to MDA 361 breast carcinoma cells induces a G1 arrest, which correlates with the loss of the catalytic activity of the G1-associated cyclin-dependent kinases (cdks) and increased levels of underphosphorylated retinoblastoma protein. This treatment resulted in a slight but detectable reduction in the protein levels of cdk6 but did not reduce the levels of cdk2, cdk4, or the D cyclins. The level of cyclin E declined initially but returned to normal levels 24 h after exposure to 10 nM ST. Because the levels of the G1 cdks and cyclins did not correlate with loss of kinase activity, the role of the cdk inhibitors involved in regulating the activity of the G1-associated cdks was investigated. The significant reduction in cdk activity observed in MDA 361 cells treated with ST for 24 h correlated with increased levels of p18 and p27Kip. The inhibition of kinase activity of preformed cdk2 complexes by lysates of MDA 361 cells that had been treated with 10 nM ST for 24 h was shown to be due to p27Kip. The reduction in the level of the active phosphorylated form of cdk2 also correlated with an increase in the level of p27Kip, which has been shown to inhibit the phosphorylation of the activating Thr-160 residue of cdk2. These results indicate that treatment of MDA 361 cells with 10 nM ST induces a significant increase in the levels of several cdk inhibitors that appear to be responsible for the observed G1 arrest.
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PMID:Staurosporine-induced G1 arrest is associated with the induction and accumulation of cyclin-dependent kinase inhibitors. 889 34

Iron chelation, known to block progression through the cell cycle, was examined for effects on the activity and subunit levels of the cyclin-dependent protein kinases (cdk). Treatment of asynchronous MDA-MB-453 cells with the iron chelators mimosine or desferrioxamine (DFO) for 24 h stopped cell division, but did not produce a single, synchronous block. DNA content analysis demonstrated that although a majority of the cells were blocked in G1 (87.3%), an unexpectedly large fraction of the cells were blocked in S phase (11.5%). Western blot analysis of the treated lysates demonstrated the presence of cyclin B, confirming that part of the cell population was blocked in S phase. After release from mimosine treatment, 84% of the cell population remained in G1 up to 8 h. Treating breast cancer cells with 400 microM mimosine for 24 h inhibited cyclin E- and cyclin A-associated kinase activity by 85% or more, although immunoblots using anti-cyclin A, cyclin E, cdc2, and cdk2 antibodies showed that these key subunits were still present in the cells at pretreatment levels. Interestingly, Western blot analysis also demonstrated that iron chelation decreased the protein levels of the cyclin D and cdk4 subunits as compared to control and produced a change in retinoblastoma protein phosphorylation. These results indicate that iron deprivation effects the activity and protein levels of the cyclin-dependent kinases, and ultimately, the pathways that control cell division.
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PMID:Iron deprivation inhibits cyclin-dependent kinase activity and decreases cyclin D/CDK4 protein levels in asynchronous MDA-MB-453 human breast cancer cells. 894 Feb 49

In order to elucidate the biochemical mechanisms by which the universal cyclin kinase inhibitor p27Kip1 regulates cell cycle progression in human breast cancer cells, a recombinant adenovirus expressing human p27 was constructed (Adp27). Upon infection of human breast cancer cells MDA-MB-231 and MCF-7 with Adp27, a high level of p27 expression was observed, and this resulted in a marked decrease in the proportion of cells in S-phase. In multiple cell lines, comparison of the cytotoxicity of Adp27 with another adenovirus vector expressing the related universal cyclin kinase inhibitor WAF1/Cip1 (AdWAF1), showed Adp27 to be markedly more (up to 56-fold) toxic than AdWAF1. DNA histograms showed Adp27 to cause a G1/S arrest at lower viral doses than AdWAF1. Analysis of cyclin dependent kinase activity following Adp27 infections showed decreased Cdk2 and cyclin B1-Cdc2 activity at lower viral doses when compared with AdWAF1. Adp27 is therefore potentially useful for studies of growth regulation and for gene therapy when growth inhibition is desired.
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PMID:A recombinant adenovirus expressing p27Kip1 induces cell cycle arrest and loss of cyclin-Cdk activity in human breast cancer cells. 917 4

We have studied the effects of olomoucine, a selective inhibitor of cdk2, cdc2 and MAP kinase, on the rate of proliferation and the cell cycle progression in human cancer cells in culture. Olomoucine inhibited the growth of the KB 3-1, MDA-MB-231 and Evsa-T cell lines in a concentration-dependent manner, with EC50 values of 45, 75 and 85 microM, respectively. Incubation of exponentially growing KB 3-1 cells in the presence of olomoucine led to an increased proportion of cells in G1 phase after 24 h or more of incubation. Olomoucine failed to rapidly affect the phosphorylation of the Rb tumor-supressor gene product. However, [3H]thymidine incorporation into the cell DNA was rapidly inhibited. We show that this inhibition is due, at least in part, to the diminution of thymidine entry into the cells. Surprisingly, all these cell lines, when synchronized at the G1/S interface and relaxed in the presence of olomoucine, progressed unhindered through the S phase. Under these conditions, the G2 phase transit was markedly retarded but not prevented. Insufficient permeability of the cell membrane to olomoucine may explain the low activity of the drug.
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PMID:Effects of olomoucine, a selective inhibitor of cyclin-dependent kinases, on cell cycle progression in human cancer cell lines. 930 May 78

Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables such as cabbage, broccoli, and Brussels sprouts, has been shown to reduce the incidence of spontaneous and carcinogen-induced mammary tumors. Treatment of cultured human MCF7 breast cancer cells with I3C reversibly suppresses the incorporation of [3H]thymidine without affecting cell viability or estrogen receptor (ER) responsiveness. Flow cytometry of propidium iodide-stained cells revealed that I3C induces a G1 cell cycle arrest. Concurrent with the I3C-induced growth inhibition, Northern blot and Western blot analyses demonstrated that I3C selectively abolished the expression of cyclin-dependent kinase 6 (CDK6) in a dose- and time-dependent manner. Furthermore, I3C inhibited the endogenous retinoblastoma protein phosphorylation and CDK6 phosphorylation of retinoblastoma in vitro to the same extent. After the MCF7 cells reached their maximal growth arrest, the levels of the p21 and p27 CDK inhibitors increased by 50%. The antiestrogen tamoxifen also suppressed MCF7 cell DNA synthesis but had no effect on CDK6 expression, while a combination of I3C and tamoxifen inhibited MCF7 cell growth more stringently than either agent alone. The I3C-mediated cell cycle arrest and repression of CDK6 production were also observed in estrogen receptor-deficient MDA-MB-231 human breast cancer cells, which demonstrates that this indole can suppress the growth of mammary tumor cells independent of estrogen receptor signaling. Thus, our observations have uncovered a previously undefined antiproliferative pathway for I3C that implicates CDK6 as a target for cell cycle control in human breast cancer cells. Moreover, our results establish for the first time that CDK6 gene expression can be inhibited in response to an extracellular antiproliferative signal.
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PMID:Indole-3-carbinol inhibits the expression of cyclin-dependent kinase-6 and induces a G1 cell cycle arrest of human breast cancer cells independent of estrogen receptor signaling. 946 64

[2-(R)-(1-Ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylp urine] (roscovitine) is a potent and selective inhibitor of cyclin-dependent kinases cdc2 and cdk2. In this study, we evaluated the potential involvement of this novel cyclin-dependent kinase inhibitor in the proliferative activity of malignant and non-malignant human breast epithelial cells in vitro. Estrogen receptor-positive MCF-7 breast carcinoma cells, immortalized estrogen receptor-negative breast epithelial cells and highly malignant estrogen receptor-negative MDA-MB-231 breast epithelial cells, were incubated with different concentrations of roscovitine ranging from 1 to 40 micrograms/ml, and cell numbers were measured with the WST-1 colorimetric assay after 24, 48, 72, 96, 120, and 144 hours of treatment. Our results demonstrated that roscovitine inhibited the proliferation of human breast epithelial cells in a dose- and time-dependent manner. Roscovitine treatment decreased the number of viable cells and prevented the exponential growth of all the cell lines examined. The antiproliferative effect of this potent cdk inhibitor was independent of the estrogen receptor status of the cells. These data suggest that roscovitine is a potential antiproliferative drug for the treatment and/or prevention of both estrogen responsive and non-responsive breast cancers.
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PMID:Roscovitine inhibits the proliferative activity of immortal and neoplastic human breast epithelial cells. 961 15

Genistein is an isoflavone known to inhibit both tyrosine protein kinase and DNA topoisomerase II. We have investigated the mechanism of genistein-induced growth inhibition in MCF-7 and MDA-MB-231 breast carcinoma cell lines. DNA flow cytometric analysis indicated that genistein induced a G2/M arrest in both cell lines. Therefore, we examined the effect of genistein on cell cycle-related proteins. Western blot analysis using whole cell lysates from MCF-7 and MDA-MB-231 treated with genistein demonstrated that genistein treatment did not change the steady-state level of cdks, cyclin A, D-type cyclins and cyclin E protein, but inhibited expression of cyclin B1 protein in a time-dependent manner. The reduction in the protein level of cyclin B1 correlated with a decrease in the level of cyclin B1 mRNA. Genistein induced expression of p21, and the increased levels of p21 were associated with increased binding of p21 with cdc2 and cdk2. These observations suggest that genistein induces a G2/M arrest in human breast cancer cells, the mechanism of which is in part due to inhibition of kinase activities of cdc2 and cdk2, and decrease in cyclin B1 expression.
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PMID:Genistein-induced G2/M arrest is associated with the inhibition of cyclin B1 and the induction of p21 in human breast carcinoma cells. 966 38

The G1 cyclins, cyclin D1 and E, are rate limiting for progression through G1 phase of the cell cycle in breast epithelial cells and are oncogenic when expressed in the mammary epithelium of transgenic mice. These genes are frequently overexpressed in clinical breast cancer where overexpression appears to be associated with specific disease phenotypes, altered responsiveness to therapeutic intervention and patient survival. In order to investigate the functional correlates of cyclin D1 and cyclin E overexpression we employed a panel of normal, immortalized and neoplastic breast epithelial cell lines to examine the relationships between cyclin gene expression, cyclin-CDK complex formation and CDK activity. In agreement with earlier studies cyclin D1 and E expression varied over an approximately tenfold range among the 18 cell lines studied. There was no apparent relationship, however, between cyclin D1 expression and the in vitro activity of its major kinase partner, Cdk4, although MDA-MB-134 cells displayed the highest level of both cyclin D1 expression and Cdk4 activity. Similarly, there was no significant relationship between cyclin E expression and cyclin E-Cdk2 activity. Fractionation of whole cell lysates by gel filtration chromatography revealed that approximately 90% of the cyclin E protein was present in inactive complexes containing the CDK inhibitors p21 and p27. Much of the small fraction of active cyclin E protein was of very high apparent molecular mass, >400 kDa, suggesting that formation of these complexes is a more important determinant of cyclin E-Cdk2 activity than cyclin E abundance. These data suggest that properties of cyclins D1 and E in addition to their ability to activate Cdk4 and Cdk2 may contribute to the effects of overexpression on the breast cancer phenotype.
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PMID:Lack of relationship between CDK activity and G1 cyclin expression in breast cancer cells. 967 7

We have examined the effect of neutralizing TGF-beta antibodies on cisplatin-mediated cytotoxicity against MDA-231 human breast tumor cell spheroids. These tridimensional in vitro systems have been shown to recapitulate the drug sensitivity pattern of tumor cells in vivo. MDA-231 tumor cell spheroids exhibit higher protein levels of the cyclin-dependent kinase (Cdk) inhibitors p21 and p27 and >10-fold lower Cdk2 activity compared to adherent cell monolayers, as well as pRb hypophosphorylation, a predominant G1 population, and a cisplatin 1-h IC50 of approximately 100 microM. Treatment of MDA-231 cells in monolayer with cisplatin for 1 h, subsequently grown as spheroids, increased steady-state TGF-beta1 mRNA levels, secretion of active TGF-beta, cellular Cdk2 activity, pRb phosphorylation, and p21 protein levels, while downregulating p27. Accumulation of cells in G2M and progression into S were noted 48 h after treatment with 100 microM cisplatin. We tested whether drug-induced upregulation of TGF-beta1 and p21, perhaps by preventing cell cycle progression, were protective mechanisms against drug-mediated toxicity by using neutralizing anti-TGF-beta antibodies. Anti-TGF-beta antibodies diminished the induction of p21, enhanced the activation of Cdk2, and facilitated progression into S and G2M following cisplatin treatment. This resulted in a >twofold enhancement of drug-induced DNA fragmentation and a shift in the cisplatin 1-h IC50 from 100 to <10 microM. These data suggest that tumor cell TGF-beta1 may protect from DNA damage and that postchemotherapy administration of TGF-beta inhibitors may facilitate progression beyond G1/S, potentially increasing the efficacy of cytotoxic chemotherapy.
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PMID:Blockade of tumor cell transforming growth factor-betas enhances cell cycle progression and sensitizes human breast carcinoma cells to cytotoxic chemotherapy. 985 76


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