Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance to 0.8 microM 4'-(9-acridinylamino)methanesulphon-m-anisidide (m-AMSA) was induced by stepwise increases of drug concentration in the human tumor cell line CALc18 originating from a breast adenocarcinoma. The resistant cell line CALc18/AMSA exhibited a resistance index of 10 and a cross-resistance to other topoisomerase II inhibitors. A 3-fold decrease in the levels of topoisomerase II decatenating activity was found in CALc18/AMSA cells. By contrast, topoisomerase I activity was increased by about 3-fold in resistant cells. Interestingly this line was hypersensitive to camptothecin, a specific inhibitor of topoisomerase I. Restriction endonuclease patterns of the topoisomerase I and topoisomerase II loci were found to be identical in CALc18/AMSA and CALc18 with no evidence of gene amplification and rearrangements. Alkaline elution of m-AMSA-treated cells showed that DNA single strand breaks and DNA-protein crosslinks were decreased in CALc18/AMSA. The DNA lesions also obtained in m-AMSA-treated nuclei indicated that no drug uptake modification occurred in both cells. Moreover, the in vitro m-AMSA-induced DNA cleavage per unit of decatenating activity and the inhibitory effects of antitumoral drugs on decatenation were not found to be different with topoisomerase II from sensitive or resistant cells. However the specific cleavage induced by m-AMSA/per mg of crude protein from resistant cells was 2 to 3 times decreased. Multidrug resistance gene transcripts were not detected while levels of acidic glutathione S transferase mRNA were found to be 8 to 10-fold greater in resistant than in sensitive cell line with no amplification of the gene. In conclusion, the diminution of topoisomerase II activity and the increase of both topoisomerase I and acidic glutathione S transferase transcripts could contribute to the resistant phenotype of these breast cancer cells.
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PMID:Study of molecular markers of resistance to m-AMSA in a human breast cancer cell line. Decrease of topoisomerase II and increase of both topoisomerase I and acidic glutathione S transferase. 164 55

DNA topoisomerases are essential nuclear enzymes that are involved in DNA replication. Clinically useful antitumor drugs such as doxorubicin, daunorubicin (anthracyclines), etoposide, teniposide (epipodophyllotoxins), and amsacrine (an aminoacridine) interfere with the function of topoisomerase II and camptothecin and its analogs inhibit topoisomerase I. Some mammalian tumor cells that express resistance to drugs that interfere with topoisomerase I or topoisomerase II have alterations in their respective topoisomerases. In this paper, we review the functions of the topoisomerases, discuss aspects of their cellular regulation, ask how interference with topoisomerase function can lead to tumor cell death, discuss the biochemical features of tumor cells that are resistant to these anti-topoisomerase drugs, and, in the context of drug resistance, we raise questions about how these drugs exert their cytotoxicity.
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PMID:Mechanisms of resistance to drugs that inhibit DNA topoisomerases. 165 18

The effect of combinations of the anthracyclines aclarubicin and daunorubicin was investigated in a clonogenic assay using the human small cell lung cancer cell line OC-NYH and a multidrug-resistant (MDR) murine subline of Ehrlich ascites tumor (EHR2/DNR+). It was found that the cytotoxicity of daunorubicin in OC-NYH cells was antagonized by simultaneous exposure to nontoxic concentrations of aclarubicin. Coordinately, aclarubicin inhibited the formation of daunorubicin-induced protein-concealed DNA single-strand breaks and DNA-protein cross-links in OC-NYH cells when assayed by the alkaline elution technique. Aclarubicin had no influence on the accumulation of daunorubicin in these cells. In contrast, the accumulation of daunorubicin in EHR2/DNR+ cells was enhanced by more than 300% when the cells were simultaneously incubated with the MDR modulator verapamil, aclarubicin, or the two agents combined. Yet the cytotoxicity of daunorubicin was potentiated significantly only by verapamil. The increased cytotoxicity of daunorubicin in the presence of verapamil was completely antagonized when aclarubicin was used together with the MDR modulator. Finally, the effect of daunorubicin on the DNA cleavage activity of purified topoisomerase II in the presence and absence of aclarubicin was examined. It was found that daunorubicin stimulated DNA cleavage by topoisomerase II at specific DNA sites. The addition of aclarubicin completely inhibited the daunorubicin-induced stimulation of DNA cleavage. Taken together, these data indicate that aclarubicin-mediated inhibition of daunorubicin-induced cytotoxicity is due mainly to a drug interaction with the nuclear enzyme topoisomerase II. This antagonism at the nuclear level explains why aclarubicin is a poor modulator of daunorubicin resistance even though aclarubicin is able to increase the intracellular accumulation of daunorubicin in a MDR cell line.
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PMID:Antagonistic effect of aclarubicin on daunorubicin-induced cytotoxicity in human small cell lung cancer cells: relationship to DNA integrity and topoisomerase II. 165 44

Patients with metastatic testis tumors are generally curable using chemotherapy, whereas those with disseminated bladder carcinomas are not. We have compared levels of the nuclear enzyme topoisomerase II in three testis (SuSa, 833K, and GH) and three bladder (RT4, RT112, and HT1376) cancer cell lines which differ in their sensitivity to chemotherapeutic agents. The testis cell lines were more sensitive than the bladder lines to three drugs whose cytotoxicity is mediated in part by inhibiting topoisomerase II: amsacrine; Adriamycin; and etoposide (VP16). The frequency of DNA strand breaks induced by amsacrine was higher (1.5- to 13-fold) in the testis cells than in the bladder cells. The level of topoisomerase II-mediated DNA strand breakage in vitro, measured by filter trapping of amsacrine-induced protein:DNA cross-links, was similarly higher in nuclear extracts from the testis than the bladder cells. Western blot analysis showed a generally higher level of topoisomerase II protein in testis than in bladder cell nuclear extracts. Topoisomerase II protein expression broadly correlated with drug-induced strand breakage in both protein extracts and whole cells, but not with population doubling time. However, despite a 2- to 20-fold increased sensitivity to the different topoisomerase II inhibitors, the testis line 833K had a less than 2-fold higher level of topoisomerase II protein than that of the bladder line RT4. These results indicate that the level of expression of topoisomerase II is an important determinant of the relative chemosensitivity of testis and bladder tumor cell lines, but that additional factors must contribute to the extreme chemosensitivity of testis cells.
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PMID:Relationship between topoisomerase II level and chemosensitivity in human tumor cell lines. 166 Mar 43

The cellular levels of topoisomerase II expression were compared between 10 fresh human tumors and normal tissues to predict the selective anticancer effect of its inhibitors such as adriamycin and VP-16. Topoisomerase II expression was observed in 9 of the 10 tumor tissues (90.0 per cent), 3 of which showed extremely high levels, whereas only 5 of the normal tissues (50.0 per cent) expressed any cellular topoisomerase II and the levels were not higher than those seen in the cancer cells. Six of the 9 positive tumors showed a higher level of topoisomerase II expression than the normal tissues, while the other 3 showed the same level. It can be interpreted from these results that topoisomerase II inhibitors could be effective in cancer patients due to the greater level of this enzyme in tumor cells than in normal tissues. Thus, it is suggested that a comparative analysis of topoisomerase II expression between tumors and normal tissues may be useful for predicting the selective cytotoxicity of topoisomerase II inhibitors in clinical practice.
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PMID:mRNA expression of topoisomerase II in human tumors and normal tissues. 166 37

This study was designed to investigate the biologic and molecular basis of the aggressive behavior of high-grade post-thymic T-cell malignancies. Freshly frozen tumor tissues from (1) human T-cell leukemia/lymphoma virus type I (HTLV-I)-positive adult T-cell lymphoma (ATL) (7 cases), (2) HTLV-I-negative aggressive T-cell lymphoma (12 cases), and (3) HTLV-I-negative nonaggressive T-cell lymphoma (11 cases) were studied for the expression of several growth-related genes or proliferation antigens including interleukin-2 receptor (IL-2R), Ki-67, transforming growth factor-beta (TGF-beta), topoisomerase, and the multidrug resistance (MDR) gene by immunohistochemistry and Northern blot hybridization. Our results showed that tumor cells associated with HTLV-I and anaplastic morphology had an enhanced expression of Ki-67, TGF-beta, and topoisomerase, as compared to nonaggressive T-cell lymphoma. The expression of IL-2R was limited to ATL and one Ki-1 lymphoma. The MDR gene was frequently expressed in ATL, but only infrequently in other, HTLV-I-negative, malignancies. Clinical progression or relapse was associated with the expression of MDR, in addition to an increased expression of Ki-67. We therefore conclude that the aggressive clinical behavior of high-grade T-cell lymphoma may result mainly from the high proliferative activity of tumor cells, but the association with HTLV-I and clinical relapse is further complicated by the development of drug resistance.
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PMID:Expression of growth-related genes and drug-resistance genes in HTLV-I-positive and HTLV-I-negative post-thymic T-cell malignancies. 167 81

P-glycoprotein (P-gp) expression and DNA topoisomerase (Topo) II are important variables in multidrug resistant tumor cell lines. The aim of this study was to evaluate P-gp expression and Topo I and II activity in benign and malignant epithelial ovarian tumors. P-gp expression was analyzed immunohistochemically in cryostat sections of fresh tumor specimens. In the same specimens Topo I and II activity were measured by, respectively, relaxation of supercoiled plasmid pBR322 DNA and decatenation of kinetoplast DNA. P-gp expression (range, 5-100% positive staining cells) was found in 3 of 6 cystadenomas, 0 of 2 borderline tumors, 15 of 21 untreated ovarian cancers, and 8 of 13 platinum/cyclophosphamide treated ovarian cancers. Median Topo I and II activity were elevated in malignant ovarian tumors compared to benign and borderline tumors. No difference was found between median Topo I activity in untreated ovarian cancer and platinum/cyclophosphamide treated ovarian cancer. High Topo II activity (greater than or equal to 8 x 10(2) units/mg protein) was more frequent in untreated compared to platinum/cyclophosphamide treated samples. Respectively, 8- and 16-fold differences in Topo I and II activity were found in the malignant tumors. Topo II activity in malignant tumors correlated with Topo I activity (r = 0.36, P less than 0.05) and the tumor volume index (r = 0.35, P less than 0.05). However, this last weak correlation cannot explain the 16-fold differences in Topo II activity in malignant tumors. Mitotic index and P-gp expression did not correlate with Topo I or II activity. A large variability in P-gp expression and Topo I and II activity was observed in patients with ovarian cancer.
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PMID:P-glycoprotein expression and DNA topoisomerase I and II activity in benign tumors of the ovary and in malignant tumors of the ovary, before and after platinum/cyclophosphamide chemotherapy. 168 37

A differentiation inducer butyrate and a tumor promoter teleocidin had inhibitory effects on the proliferation of PLC/PRF/5 hepatoma. Both of these reagents stimulated the production of procollagen type III peptide, enhanced the cytokeratin assembly and altered the morphological appearance. Novobiocin, a topoisomerase II inhibitor, enhanced the cytokeratin assembly induced by butyrate but antagonized that induced by teleocidin without changing the expression and the phosphorylation state of cytokeratin proteins. In addition, novobiocin acted synergistically with butyrate but not with teleocidin in stimulating the procollagen production and the acetate uptake. These results suggest that butyrate and teleocidin induce cell differentiation via distinct signaling pathway and that novobiocin and butyrate can be used as subsidiary drugs in preventing the growth of hepatoma.
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PMID:Novobiocin modulates cytokeratin assembly and differentiation of human hepatoma cells induced by butyrate and teleocidin. 171 36

Chronic lymphocytic leukemia lymphocytes were used to study mechanisms involved in apoptosis (programmed cell death). Apoptosis, which was determined by morphological changes including cell death and by internucleosomal DNA fragmentation, occurred during culture for 1 to 2 days in a portion of the cells from three of the four patients tested. Most of the cells underwent apoptosis and DNA fragmentation was greatly enhanced when cells were cultured in the presence of the microtubule inhibitor colchicine, the topoisomerase II inhibitor etoposide, or the glucocorticoid methylprednisolone. Tumor-promoting phorbol esters inhibited spontaneous DNA fragmentation and cell death including that induced by colchicine, etoposide, and methylprednisolone, indicating that they act on an event common to apoptosis caused by diverse stimuli. Phorbol esters probably act through protein phosphorylation, since they were effective at concentrations which modulated protein kinase C (PKC) and their action was prevented by H-7, which binds to and inactivates the catalytic site of PKC. In the absence of phorbol ester, H-7 itself induced some apoptosis. These findings implicate PKC in the suppression of apoptosis, but its precise role requires systematic investigation.
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PMID:Induction of apoptosis in chronic lymphocytic leukemia cells and its prevention by phorbol ester. 172 40

The mechanism of death induced by recombinant human tumor necrosis factor (rHuTNF) in L929 tumor cells of C3H mice was investigated. Treatment with rHuTNF led to fragmentation of DNA into nucleosomal oligomers and to induction of the expression of TRPM-2, a programmed cell death-associated gene. Both events preceded cell death by several hours. Treatment with DNA topoisomerase II inhibitors accelerated both the rHuTNF-mediated DNA fragmentation and the elevation in TRPM-2 messenger RNA levels. These results suggest that rHuTNF exerts its cytotoxicity on L929 cells by activating programmed cell death, leading to apoptosis, and that topoisomerase II inhibitors enhance rHuTNF-mediated cytotoxicity by accelerating this process.
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PMID:Activation of programmed cell death by recombinant human tumor necrosis factor plus topoisomerase II-targeted drugs in L929 tumor cells. 156 7


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