Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA synthesis has been studied in nuclei isolated from phytohaemagglutinin-stimulated lymphocytes from normal subjects and patients with megaloblastic anaemia. Lymphocytes were incubated for 72 h, nuclei isolated and incorporation of tritiated deoxythymidine triphosphate ([3H]TTP) into DNA measured, usually over a 10 min incubation period. Preincubation of normal phytohaemagglutinin-stimulated lymphocytes with methotrexate (1 - 10(-5) M, 48--72 h), 5-fluorouracil (1 - 10(-6) M, 70--72 h), and 1-beta-D-arabinofuranosyl cytosine (cytosine arabinoside) (4 - 10(-5) M, 71--72 h) caused a mean rise in [3H]TTP incorporation of 1.7 (P less than 0.01), 1.7 (P less than 0.05) and 2.4 (P less than 0.0025) fold, respectively. Hydroxyurea (3 - 10(-4) M, 48--72 h) in two experiments caused a mean increase of 1.6 fold. Untreated vitamin B-12- and folate-deficient cells showed a 2.0-fold (P less than 0.05) increase above the incorporation when the deficiencies were corrected by addition of vitamin B-12 and folic acid between 0 and 72 h in vitro. The mean percentages of the incorporation due to ATP-independent synthesis in nuclei from normal untreated cells, 5-fluorouracil-treated, cytosine arabinoside treated and vitamin B-12- or folate-deficient cells were 56 +/- 7% S.E., 41 +/- 7%, 84 +/- 3% and 28 +/- 6%, respectively. 5-Fluorouracil caused a two-fold increase in the cytoplasmic fraction of DNA polymerase when added to phytohaemagglutinin-stimulated lymphocytes between 48 and 72 h of culture but had no significant effect when added between 70 and 72 h.
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PMID:DNA synthesis in isolated lymphocyte nuclei. Effects of megaloblastic anaemia due to folate or vitamin B-12 deficiency or antimetabolite drugs. 88 15

Using new in vitro techniques developed at the Cancer Research Unit, cell kinetic measurements were obtained in primary and metastatic human colonic tumors, polyps and normal bowel that did not require in vivo 3HTdR and required only single samples of tissue. These techniques included the measurement of the number of cells in DNA synthesis (LI), an estimate of the DNA synthesis time (Ts) and the growth fraction of tissues by means of the primer-available DNA-dependent DNA polymerase assay (PDP). From these data, the potential doubling time and the cell cycle time (Tc) of the tumors were calculated. Early preliminary data on human colonic specimens presented in Tables 1 and 2 indicate that there is an increase in LI from the low polyps to higher adenocarcinomas. There is little difference between primary and metastatic tumor cell kinetics. Growth fraction estimates (PDP) of the various colonic tissue types are also not significantly different and except for villous adenomas, DNA synthesis times are constant. The median 3HTdR labeling indices of 7% primary adenocarcinomas include a number of samples (approximately 20% of all samples) with high labeling indices (in the 10--20% range). These high labeling tumors may be those that show objective response to S-phase active drugs, e.g., 5-FU.
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PMID:Human colonic tumor cell kinetics: potential for therapy. 92 8

Examples of collateral sensitivity, even in experimental tumor systems, remain few. Preliminary data from this laboratory indicated that certain tumor cells expressed increased sensitivity to cisplatin after exposure in vitro to x-irradiation. To further clarify whether the type of fractionated radiation procedure used clinically can induce hypersensitivities to certain antitumor drugs we have pre-exposed the human ovarian carcinoma cell line JA-T/P derived from a tumor from an untreated patient to fractionated x-irradiation (total dose 50 Gy) in vitro. The resultant subline JA-T/DXR-10 expressed collateral sensitivity to cisplatin (CDDP), methotrexate (MTX) and fluorouracil (5-FU), but not to acute x-irradiation. Hypersensitivity to CDDP was associated with decreased activity of DNA polymerase beta (3.5-fold, P less than .01), but unaltered glutathione metabolism. Pre-incubation with cyclosporin A or with 3-aminobenzamide significantly enhanced (twofold, P less than .01) CDDP-induced cytotoxicity in JA-T/P cells, but not in the DXR-10 subline. Consistent with MTX hypersensitivity dihydrofolate reductase activity was significantly decreased (2.9-fold, P less than .01). Despite collateral sensitivity to 5-FU, however, thymidylate synthase activity was increased (twofold, P less than .05) suggesting alternative mechanisms for 5-FU-induced cytotoxicity in these JA-T/DXR-10 cells. These data demonstrate that DNA repair and associated reduced folate metabolism can be modified not only by drugs but also by fractionated x-irradiation.
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PMID:Expression of collateral sensitivity to cisplatin, methotrexate, and fluorouracil in a human ovarian carcinoma cell line following exposure to fractionated x-irradiation in vitro. 155 59

1. Pharmacodynamics and pharmacokinetics of antimetabolites. Antimetabolites are administered in the form of a base or its riboside, which is incorporated into the cell and converted to an active or inactive metabolite. The active metabolite remain in the cell inhibiting the enzymes to catalyze nucleotide synthesis for nucleotide triphosphate formation, but the inactive metabolites are rapidly excreted out of the cell. The inhibitory effect of antimetabolites on nucleotide formation is correlated with factors, such as maintenance of drug blood level, incorporation of the drug into the cell, activation and inactivation of the drug, affinity of the active form to the corresponding enzyme, and change in pool size of the intermediate metabolites in nucleotide synthesis. The salvage synthesis occurring at the higher level of the enzymes catalyzing nucleotide synthesis to counteract the inhibition by the drug is also correlated with the nucleotide formation. II. Pyrimidine antagonists 1. Cytosine arabinoside (ara-C) and its derivatives Ara-C is rapidly converted to ara-CTP and ara-U. The former remains in the cell and inhibits DNA polymerase, but the latter is excreted rapidly out of the cell. A small portion of ara-C is incorporated into DNA, which results in the degradation of DNA as demonstrated by reduced sedimentation of bulk DNA in alkaline sucrose gradient centrifugation and the ladder DNA fragmentation with a minimum fragment of approximately 180 base pairs and its conjugates in agarose gel electrophoresis. Behenoyl ara-C (BHAC) is highly lipophilic and highly distributed in the erythrocyte stroma and membrane fraction of leukocytes after iv infusion. The incorporated BHAC is released after the plasma BHAC level decreases, which suggests that erythrocytes can be a drug reservoir after iv infusion. Therefore, severe anemia should be treated before BHAC chemotherapy for longer maintenance of the plasma BHAC level. 2. 5-Fluorouracil (5-FU) and its derivatives Activation of 5-FU in the cells is metabolized by uracil metabolizing enzymes to FUMP and FdUMP. FUMP is further metabolized to FdUMP and is also incorporated to RNA. FdUMP produces a ternary complex with thymidylate synthetase and leucovorin; subsequently, conversion of dUMP to dTMP is strongly inhibited. Thus, FUMP and FdUMP inhibit RNA and DNA metabolism, respectively. Enzyme activity during 5-FU metabolism and consequently the degree of inhibition of DNA and RNA syntheses markedly differ with the tumor cell species. This should be taken into consideration when performing chemotherapy of malignancies.
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PMID:[Clinical pharmacology of anticancer agents (Part 4). Antimetabolites (1)]. 173 42

HO-221, N-[4-(5-bromo-2-pyrimidinyloxy)-3-chlorophenyl]-N'-(2- nitrobenzoyl) urea is a new benzoylphenylurea derivative. The compound exhibits significant antitumor effects against various animal tumors, and was especially effective against the solid tumors implanted subcutaneously. HO-221 inhibits DNA polymerase alpha activity strongly in vitro. In this study, we examined the cross-resistance of HO-221 to various antitumor agents using sublines of mouse leukemia. HO-221 showed antitumor effects in mice bearing L 1210 or P 388 leukemia resistant to 10 antitumor agents, DM (daunomycin), MMC (mitomycin C), CDDP (cisplatin), 5-FU (5-fluorouracil), Ara-C (cytosine arabinoside), MTX (methotrexate), CPA (cyclophosphamide), CQ (carboquone), ADM (adriamycin) and VCR (vincristine), respectively. These antitumor agents were also effective in P 388 leukemia resistant to HO-221 (P 388/HO-221). Furthermore, CDDP- and MMC-resistant sublines showed a collateral sensitivity to HO-221 in vivo. The grow the inhibitory effects were also noted in vitro in ADM-, CDDP- and MMC-resistant cells by HO-221. However, the in vitro experiments didn't show such collateral sensitivity on the resistant sublines. These results suggest that there is no cross-resistance between HO-221 and other known antitumor agents, and that HO-221 seemed to be worth for evaluating clinical usefulness.
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PMID:[Cross-resistance of HO-221 and various antitumor agents in sublines of mouse leukemia]. 189 47

We have examined the induction of alkali-labile regions in DNA of human neoplastic cells treated with 5-fluorouracil and 5-fluorodeoxyuridine. 5-Fluorouracil induces DNA lesions by two mechanisms: incorporation of drug into DNA and a second mechanism not involving the incorporation. The second mechanism is seen in cells treated with aphidicolin, a specific inhibitor of DNA polymerase alpha, to stop the movement of the DNA replication forks. 5-Fluorodeoxyuridine is not incorporated into DNA of these cells; only the second mechanism of induction of alkali-labile DNA is detected. The second mechanism is in all probability due to inefficient DNA repair of normally occurring defects in purine and pyrimidine residues. Furthermore there is a correlation between increasing levels of alkali-labile regions in the DNA and cytotoxicity of the drugs. This may be one explanation for the cytocidal effects of 5-fluoropyrimidines.
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PMID:DNA lesions in human neoplastic cells and cytotoxicity of 5-fluoropyrimidines. 294 36

The feasibility of a cytokinetic chemotherapy based on estrogenic recruitment has been evaluated in 5 patients, affected by locally advanced breast cancer with low or absent receptor content. Tumor proliferative activity was evaluated by the thymidine labeling index (TLI) and the primer-dependent alpha DNA polymerase assay (PDP-LI) which gives an in vitro estimation of tumor growth fraction. The patients have been treated with diethylstilbestrol (DES) 1 mg/die. for 3 days, followed by FAC (5-Fluorouracil 600 mg/m2, Adriamycin 50 mg/m2, Cytoxan 600 mg/m2) i.v. on day 4 q. 21 days. Radical surgery was performed after 3 DES-FAC regimens. Tumor biopsies for evaluation of tumor proliferative activity were performed immediately before and after DES and 24 h after chemotherapy. Our results demonstrate that DES was able to induce an increase in TLI in 3/5 of the patients while the PDP-LI was significantly increased in 5/5 of the patients; subsequent chemotherapy induced a sharp decrease in tumor proliferation. These results provide the rationale for the design of cytokinetic regimens where chemotherapy is administered at the time of estrogen induced tumor cell recruitment.
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PMID:Estrogen induced expansion of the growth fraction in receptor negative human breast cancer. 409 31

A series of beta-alkylaminopropiophenone derivatives were demonstrated to be potent antineoplastic agents. Several compounds showed activity against Ehrlich ascites carcinoma growth in CF1 mice by demonstrating over 70% inhibition. Most of these agents proved to be potent cytotoxic agents in inhibiting the growth of a number of murine and human cancer cell lines grown in tissue culture. Their ED50 values were comparable to those of the selected standard anticancer drugs, such as 6-MP, ara-C, hydroxyurea, 5-FU, 6-aza-UMP, etoposide, antimycin A, actinomycin D and cycloheximide. In the mode of action studies in Tmolt3 cells, beta-(3",5"-dimethyl)piperidinopropiophenone was observed to reduce DNA and RNA synthesis significantly at 25 microM within 60 min incubation. The site of action of this agent appears to involve the reduction of the activities of Tmolt3 DNA polymerase alpha 1 dihydrofolate reductase, PRPP-amido transferase and ribonucleoside reductase.
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PMID:Antineoplastic activities of 2,3,4-chloro-substituted beta-alkylaminopropiophenone derivatives in CF1 mice and in murine and human tumor cells. 886 31

To clarify the clinical significance of PyNPase (Pyrimidine Nucleoside Phosphorylase)/ PD-ECGF activity in breast cancer, we examined the possible correlation of PyNPase activity to clinicopathological features and prognosis in 195 patients with primary breast cancer between January 1992 through December 1993. The mean PyNPase activity of primary breast cancer, assayed by ELISA method, was 140.6 U/ml, which was between that of benign breast disease (18.2) and recurrent tumors (270.9). In histological type of breast cancer, tumors with solid-tubular carcinoma had significantly higher levels of PyNPase activity. The activity of ER negative or aneuploid tumors was higher than that of ER positive or diploid tumors, respectively. And there was a significant relationship between PyNPase activity and proliferative activity determined by S-phase fraction (SPF) or DNA polymerase alpha. These findings suggested that PyNPase activity was associated with the degree of malignancy. As regards prognosis, in lower SPF (< 16%) group, patients with higher PyNPase activity had significantly lower disease--free survival rates, whereas those with higher activity had a favorable prognosis in the higher SPF (> or = 16%) group. The contradiction might be explained by the possibility that 5-FU derivatives were effective only in patients with high SPF and PyNPase activity, as all patients were treated by a regimen containing 5-FU derivatives. We suggest that PyNPase activity is associated with progression and proliferation of breast cancer, and that it may be useful for prediction of prognosis and therapeutic efficacy of 5-FU derivatives.
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PMID:[Prognostic effect of PyNPase (pyrimidine nucleoside phosphorylase) activity in breast cancer]. 946 30

5-Fluorouracil (5-FU) is a commonly used adjuvant therapeutic drug in treating breast cancer. 5-FU is metabolically converted to 5-fluorouracil-2'-deoxyuridine-5'-monophosphate-(FdUMP) which is believed to inhibit DNA synthesis in neoplastic cells by forming a tightly bound ternary complex with thymidylate synthase (TS). In the present study, we examined the possible relationship between TS levels and clinico-pathologic and prognostic features in breast disease. Mean TS levels of 2.9 pmol/g, 6.1 pmol/g, and 23.1 pmol/g were obtained in cases of benign breast disease (3 cases), primary breast cancer (115 cases), and recurrent tumors (4 cases), respectively. In breast cancer, mean TS levels significantly correlated with S-phase fraction (SPF), DNA polymerase a and lymphatic invasion. Thus, TS levels in breast cancer significantly reflected cell proliferation and malignancy. Regarding the survival rate, patients with TS values above 10 pmol/g showed an unfavorable prognosis. The effectiveness of adjuvant 5-FU derivatives chemotherapy was reflected in a higher disease-free survival rate in node (+) cases showing TS levels between 5 and 10 pmol/g (p < 0.1), but not in node (-) cases. In conclusion, TS levels in neoplastic tissues of the breast were highest in recurrent tumors, followed by those in primary cancer, benign breast disease and in breast cancer which reflected proliferative activity. Breast cancers with extremely high TS levels were accompanied by an unfavorable prognosis; however, those with moderately high TS levels tended to respond to adjuvant chemotherapy with 5-FU derivatives.
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PMID:Thymidylate synthase levels as a therapeutic and prognostic predictor in breast cancer. 1069 29


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