Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to study the mechanisms by which p53 function is regulated, human wild-type p53 cDNA was cloned into a vaccinia virus vector and the expressed p53 protein was used to investigate binding of the p53 by cellular proteins from a cDNA expression library from human liver. One protein that bound wild-type p53 had > 99% homology with DNA topoisomerase IIb. p53 protein was coimmunoprecipitated from topoisomerase II-rich cell lysates (but not from topoisomerase II-deficient cell lysates) by an antibody to topoisomerase IIa and IIb. This binding was shown to occur without a dsDNA intermediary. Hepatocellular carcinomas (HCCs) and adjacent nontumorous liver tissues from ten patients were studied to determine the level of expression of topoisomerase II and p53. Overexpressed topoisomerase II proteins were detected by western blot in six of ten HCCs (60%), including several in which presumed wild-type p53 was detected by immunohistochemistry. No topoisomerase II expression was detectable in the ten nontumorous liver tissues from the same patients or in a sample of normal human liver.
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PMID:Binding of wild-type p53 by topoisomerase II and overexpression of topoisomerase II in human hepatocellular carcinoma. 916 88

Apoptosis is a major determinant of the effectiveness of antitumor chemotherapy since most of the drugs used in cancer treatment provoke cell death by this process. We selected L1210/0.7R (7-fold) and L1210/3R (16-fold) murine leukemia cells resistant to cisplatin (CDDP) by adaptation of parental L1210/S cells to increasing drug concentration. L1210/0.7R exhibited a decreased apoptosis response to CDDP compared to parental L1210/S, while it was totally defective in L1210/3R as analyzed by cell morphology, DNA fragmentation, and poly(ADP-ribose) polymerase cleavage. This default in apoptosis did not result from differential expression of the antiapoptotic protein bcl-2 or from altered expression of p53. L1210/3R was resistant to other cross-linking agents and sensitive to topoisomerase II inhibitors and microtubule poisons. Whatever the drug sensitivity phenotype to these agents, L1210/3R was totally defective in apoptosis in response to drug treatment, showing that apoptosis control cannot be directly involved in the resistance process of these cell lines.
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PMID:Deficient apoptotic process in cisplatin-resistant L1210 cells cannot account for the cellular response to various drug treatments. 917 54

The exact mechanisms for the selective toxicity of chemotherapeutic drugs against tumor cells are not fully understood. We designed a series of experiments to test the possibility that the positive proliferative signal initiated by oncogenes might change the sensitivity for apoptosis induction by the anticancer drug etoposide (VP16), an inhibitor of topoisomerase II (Topo II). Treatment with VP16 induced significantly increased apoptosis in NIH3T3 cells transformed by oncogenic src, ras or raf, compared with the normal 3T3 cells. Apopototic changes involved nuclear DNA fragmentation, morphological alterations and decreased viability. Furthermore it was shown that stress-activated protein kinase (SAPK) was activated much more strongly in all three transformed lines compared to untransformed cells by VP16 treatment, while slight activation of extracellular signal-regulated kinase (ERK1) was observed in all four cell lines. In addition, the transformed cells displayed arrest in mid-S-phase following the treatment, whereas NIH3T3 cells were primarily arrested in late S and G2/M phase. Finally, the cyclin-dependent kinase inhibitor p21 WAF1 was induced in all four cell lines, although induction of p53 was not detected in any of these cell lines. Taken together our results demonstrated that oncogenic transformation can sensitize the cells to apoptosis induction, stress kinase activation and cell cycle arrest in response to VP16 treatment. These results may have important implications for understanding the selective toxicity of anti-cancer drugs in tumor cells.
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PMID:Oncogenic transformation potentiates apoptosis, S-phase arrest and stress-kinase activation by etoposide. 934 97

The p53 tumour suppressor protein plays a key role in the integration of stress signals. Multi-site phosphorylation of p53 may play an integral part in the transmission of these signals and is catalysed by many different protein kinases including an unidentified p53-N-terminus-targeted protein kinase (p53NK) which phosphorylates a group of sites at the N-terminus of the protein. In this paper, we present evidence that the delta and epsilon isoforms of casein kinase 1 (CK1delta and CK1epsilon) show identical features to p53NK and can phosphorylate p53 both in vitro and in vivo. Recombinant, purified glutathione S-transferase (GST)-CK1delta and GST-CK1epsilon fusion proteins each phosphorylate p53 in vitro at serines 4, 6 and 9, the sites recognised by p53NK. Furthermore, p53NK (i) co-purifies with CK1delta/epsilon, (ii) shares identical kinetic properties to CK1delta/epsilon, and (iii) is inhibited by a CK1delta/epsilon-specific inhibitor (IC261). In addition, CK1delta is also present in purified preparations of p53NK as judged by immunoanalysis using a CK1delta-specific monoclonal antibody. Treatment of murine SV3T3 cells with IC261 specifically blocked phosphorylation in vivo of the CK1delta/epsilon phosphorylation sites in p53, indicating that p53 interacts physiologically with CK1delta and/or CK1epsilon. Similarly, over-expression of a green fluorescent protein (GFP)-CK1delta fusion protein led to hyper-phosphorylation of p53 at its N-terminus. Treatment of MethAp53ts cells with the topoisomerase-directed drugs etoposide or camptothecin led to increases in both CK1delta-mRNA and -protein levels in a manner dependent on the integrity of p53. These data suggest that p53 is phosphorylated by CK1delta and CK1epsilon and additionally that there may be a regulatory feedback loop involving p53 and CK1delta.
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PMID:p53 is phosphorylated in vitro and in vivo by the delta and epsilon isoforms of casein kinase 1 and enhances the level of casein kinase 1 delta in response to topoisomerase-directed drugs. 934 7

The acridine derivative m-AMCA (methyl-N-[4-(9-acridinylamino)-2-methoxyphenyl]carbamate hydrochloride), a carbamate analogue of the topoisomerase II poison amsacrine, is distinguished by its high cytotoxicity against non-cycling tumour cells. We compared the response of cultured Lewis lung carcinoma cells to m-AMCA, amsacrine and the topoisomerase I poison camptothecin. The DNA polymerase inhibitor aphidicolin reversed the cytotoxicity of camptothecin fully, that of amsacrine partially, and that of m-AMCA minimally. The ability of m-AMCA to induce the enzyme poly(ADP-ribose)polymerase (PARP) was markedly lower than that of camptothecin or amsacrine. Cell cycle responses to m-AMCA and amsacrine were similar, with slowing of progress through S-phase and arrest in G2-phase. These cell cycle changes were also observed when plateau phase cultures were exposed to drug for 1 h, washed free of drug and cultured in fresh medium, with m-AMCA having a more pronounced effect than amsacrine and camptothecin having no effect. We also examined the role of p53 protein in the response using cultured human H460 cells. Both m-AMCA and amsacrine induced p53 protein expression in proliferating but not in non-proliferating H460 cells, and induced p21WAF1 regardless of proliferation status. Both induced G1-phase cell cycle arrest. It is suggested that two cytotoxicity mechanisms can be distinguished using these drugs. The first is specific for S-phase cells, is reversed by aphidicolin and induces PARP activity. The second is cell cycle non-specific, does not induce PARP and is unaffected by aphidicolin. Camptothecin activates only the first, m-AMCA primarily the second and amsacrine activates both.
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PMID:Cellular responses to methyl-N-[4-9-acridinylamino)-2-methoxyphenyl] carbamate hydrochloride, an analogue of amsacrine active against non-proliferating cells. 938 32

Beta-lapachone and camptothecin are structurally unrelated agents thought to inhibit topoisomerase-I activity through distinct mechanisms. We find that beta-lapachone is much more potent than camptothecin in inducing acute cytotoxic effects on human malignant glioma cells. Acute cytotoxicity induced by both drugs is apoptotic by electron microscopy, but not blocked by inhibitors of RNA or protein synthesis and not associated with changes in the expression of bcl-2, bax, p53, p21 or GADD45 proteins. In contrast, prolonged exposure of glioma cells to both drugs for 72 hr results in growth inhibition and apoptosis, with EC50 values around 1 microM. None of 7 glioma cell lines tested were resistant to either drug. LN-229 cells which have partial p53-wild-type activity show enhanced expression of p53, p21 and bax protein, whereas bcl-2 levels decrease, after exposure to camptothecin. In contrast, beta-lapachone increases bax protein expression in the absence of p53 activation. T98G cells are mutant for p53. In these cells, p53 levels do not change and p21 is not induced. bax accumulation in T98G cells is induced by both drugs, with bcl-2 levels unaltered. Surprisingly, ectopic expression of murine bcl-2 fails to abrogate the toxicity of either drug. Camptothecin, but not beta-lapachone, sensitizes human malignant glioma cells to apoptosis induced by the cytotoxic cytokines, tumor necrosis factor-alpha and CD95 ligand. Thus, both drugs have potent anti-glioma activity that may be mediated by enhanced bax expression but is not inhibited by ectopic bcl-2 expression. Camptothecin-like agents are particularly promising for immunochemotherapy of malignant glioma using cytotoxic drugs and CD95 ligand.
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PMID:Topoisomerase-I inhibitors for human malignant glioma: differential modulation of p53, p21, bax and bcl-2 expression and of CD95-mediated apoptosis by camptothecin and beta-lapachone. 939 50

In contrast to intrinsic drug resistance, induced multidrug resistance in gastric cancer cells has not been well studied. Therefore, two doxorubicin-resistant cell lines, (SNU-1DOX, SNU-16DOX), were derived in vitro from gastric carcinoma cell lines (SNU-1, SNU-16) respectively, and their characteristics were investigated. These resistances were not associated with overexpression of mdrl, multidrug resistance associated protein 1 (MRP1), pi or liver class of glutathione S transferase (GST pi, GSTL), heat shock protein 70 (HSP70), p53 or transglutaminase C (TGC). Levels of p21WAF1 RNA and topoisomerase II protein were decreased in the SNU-16DOX, but not in SNU-1DOX. However, the subsequent enzyme activity of topoisomerase II in SNU-16DOX was not decreased, but rather increased in SNU-16DOX. Furthermore, both resistant cell lines showed lower uptake and higher efflux of doxorubicin and induced cross-resistance to etoposide and vincristine in addition to doxorubicin, indicating a multi-drug resistance phenotype. In summary, we report two gastric carcinoma cell lines exhibiting induced multidrug resistance phenotype and suggest that mdrl, MRP1, GST, TGC, HSP70 and p53 do not play important roles in induced drug resistance in these cell lines. The role of changes in topoisomerase II activity and/or protein is still inconclusive, and p21WAF1 is associated with induced multidrug resistance in the SNU-16DOX gastric carcinoma cell line.
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PMID:Characteristics of human gastric carcinoma cell lines with induced multidrug resistance. 941 98

Expression of the tumor suppressor gene product p53 and the cyclin-dependent kinase inhibitor p21, which is transcriptionally activated by p53, was investigated and compared with patient survival in a retrospective longitudinal study of 202 cases of endometrial carcinoma. The median duration of follow-up was 4.3 years. P53 was observed immunohistochemically in 63 (31%) of the tumors and was found by univariate analysis to be related to reduced adjusted survival (p = 0.00028) and disease-free survival (p = 0.04). However, p53 expression was not found by multivariate analysis to be an independent prognostic factor when compared with FIGO stage, histologic grade, and proliferative activity, as determined by immunoreactivity for topoisomerase IIalpha with the antibody Ki-S1. Overexpression of p53 was related to histologic grade (p < 0.00001), proliferative activity (p = 0.0071), and inversely to progesterone receptor content (p = 0.042). Immunohistochemical identification of p21 was investigated in 95 cases and found to be positive in 19 (39%) of 49 tumors with p53 overexpression and in 13 (28%) of 46 tumors without p53 overexpression (p = 0.28). Expression of p21 is therefore not related to p53 expression, nor was it found to be related to proliferative activity. Strong expression of p21 was observed in tumors negative for progesterone receptors (p = 0.0028). P53 in endometrial carcinoma is not associated with induction of the cell cycle inhibitor p21, but is associated with an enhanced proliferative activity. The findings of multivariate analysis suggest that the prognostic significance of p53 is related mainly to cell proliferation.
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PMID:p53 protein in endometrial cancer is related to proliferative activity and prognosis but not to expression of p21 protein. 942 Oct 76

Few studies have analyzed the relationship among pathology, therapy-induced changes, proliferative activity, and outcome for rhabdomyosarcoma (RMS), despite the challenges of histopathologic interpretation of this tumor after treatment. Although cytodifferentiation and decreased mitotic activity after treatment were documented previously, the clinical consequences of these changes are uncertain because of the small number of cases analyzed. We analyzed 16 RMSs with pre- and post-treatment specimens for clinicopathologic features, outcome, and immunohistochemical data on formalin-fixed, paraffin-embedded tissue for vimentin, smooth muscle actin, muscle-specific actin, desmin, myoglobin, p53 protein, topoisomerase II-alpha, and MIB-1 proliferative activity. Four of eight alveolar (ARMS), five of five botryoid (BRMS), and two of three nonbotryoid embryonal (ERMS) RMSs displayed varying degrees of post-therapeutic histologic maturation and expressed one or more myoid markers. The remaining five RMSs had no cytodifferentiation. Myoid marker expression did not change significantly. In BRMS, MIB-1 and topoisomerase II-alpha proliferative activity decreased after therapy and correlated with cytodifferentiation and survival. This relationship was less clear for ERMS and ARMS. Five nonbotryoid RMSs without cytodifferentiation had either unchanged or increased proliferative activity, and four of these patients died of RMS. Six nonbotryoid RMSs with both cytodifferentiation and residual foci of undifferentiated cells had variable outcomes, including longer survival. We conclude that BRMS and ERMS exhibit therapy-induced cytodifferentiation more frequently than does ARMS. Cytodifferentiation and decreased proliferative activity are associated with favorable outcome in BRMS; unchanged or increased post-therapeutic proliferative activity suggests aggressive biologic potential in ERMS and ARMS. Combined patterns of cytodifferentiation and residual undifferentiated foci might be associated with increased, decreased, or unchanged proliferative activity and are difficult to interpret, but the presence of cytodifferentiation might presage an improved survival. Immunohistochemical analysis for proliferation markers might be useful for highlighting foci of less differentiated RMS or cytodifferentiated tumor cells in contrast to non-neoplastic, terminally differentiated muscle cells.
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PMID:Pathologic features of rhabdomyosarcoma before and after treatment: a clinicopathologic and immunohistochemical analysis. 943 61

Melanoma cells often display a multidrug-resistant phenotype, but the mechanisms involved are largely unknown. In order to establish a reproducable model system for studying the exact mechanisms conferring chemoresistance, we selected drug-resistant sublines in vitro derived from one parental human melanoma (MeWo) cell line. Four commonly used chemotherapeutic drugs (vindesine, etoposide, fotemustine, cisplatin) with different modes of action were choosen and stable sublines exhibiting four different levels of resistance against each drug were selected by continuous exposure over two years. Analysis of the drug-resistant sublines regarding their pharmacological characteristics and cross-resistance pattern revealed an up to 26-fold increased relative resistance against the alkylating agent fotemustine (MeWoFOTE) and an up to 35.7-fold increased relative resistance against topoisomerase-II-inhibiting etoposide (MeWoETO). Cisplatin selection (MeWoCIS) resulted in a 6-fold higher resistance compared to parental MeWo cells, whereas vindesine exposure (MeWoVIND) increased relative resistance up to 10.2-fold. Sublines selected separately for resistance to the DNA-damaging agents fotemustine, cisplatin and etoposide demonstrated strong cross-resistance. In comparison to the parental cell line drug-resistant sublines showed altered expression patterns of proto-oncogenes. Levels of p53 mRNA decreased with increasing resistance to vindesine, etoposide and fotemustine. Expression of bcl-2 family members (bax, bcl-x) was modulated by fotemustine, etoposide and cisplatin. In addition the expression of members of the fos (c-fos) and jun (c-jun, jun-D) gene family encoding transcription factors of the AP-1 complex was altered in all drug-resistant sublines. The pattern of expression varied with the inducing stimulus and this was paralleled by changes in the transactivation potential of AP-1. Our results reinforce the central role of AP-l in drug resistance probably through its participation in a programmed cellular stress response.
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PMID:Human melanoma cell lines selected in vitro displaying various levels of drug resistance against cisplatin, fotemustine, vindesine or etoposide: modulation of proto-oncogene expression. 949 34


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