Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006826 (cancer)
 1,092,456 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical properties of cyclic nucleotide phosphodiesterases in a nonmetastasizing and a spontaneously metastasizing rat mammary carcinoma were compared. The phosphooiesterases in both tumors had a pH optimum of around 8.0 and preferentially hydrolysed cyclic purine nucleotides. The rate of hydrolysis of purine nucleotides in the nonmetastasizing tumor was two times higher than in the metastasizing tumor, but the rate of pyrimidine nucleotide hydrolysis was equal in both tumors. Theophylline, caffeine, and D,L-4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro20-1724) inhibited the enzyme activity in both tumors; the percent inhibition was the same by each inhibitor. The cyclic nucleotie phosphodiesterase activity in either tumor was stimulated by Mg++, Mn++, and Co++ and suppressed by Ca++, Zn,++, and Ni++. EDTA inhibited the activity below the basal level (activity in the absence of added cation), an this inhibition could be recovered up to the basal level by an equimolar quantity of either Mn++ or Mg++. Further stimulation of the enzyme activity with increasing concentrations of divalent cations was observed only with Mn++. Similar effects were observe with ethylene glycol bis(beta-aminoethyl ether)-tn,n-tetraacetic acid. The stimulatory cations affected both the low and high Michaelis constant (tkm) enzymes in these tumors by increasing the maximum velocity. In the low Km enzyme, the Km was also slightly increased. Neither guanosine 3',5'-cyclic monophosphate nor adenosine 3',5'-cyclic monophosphate had any effect on the hydrolysis of the other at physiologic levels.
J Natl Cancer Inst 1976 Jan
PMID:Biochemical properties of cyclic nucleotide phosphodiesterase in metastasizing and nonmetastasizing rat mammary carcinomas. 0 60

It has been demonstrated previously that nontransformed C3H/10T1/2CL8 mouse embryo fibroblasts (10T1/2) can induce a state of reversible growth inhibition in cocultured malignantly transformed mouse fibroblasts and that this inhibition is modulated by serum concentration. The present study suggests that cyclic nucleotides may be implicated in this intercellular communication. The phosphodiesterase inhibitors theophylline, caffeine, and 3-isobutyl-1-methylxanthine (IBX) at concentrations of 10(-3) M, maintained continuously, were all found to inhibit the expression of 3-methylcholanthrene-induced malignant transformation when added 7 days after removal of carcinogen. IBX was the most potent, causing 100% inhibition at 10(-4) M and 70% inhibition at 10(-5) M. This inhibition was partially reversible in the former case and completely reversible in the latter case by removal of drug. Complete inhibition by 10(-4) M IBX was still observed when treatment was delayed 21 days postcarcinogen. In reconstruction experiments, utilizing confluent monolayers of 10T1/2 cells overlaid with transformed cells, IBX caused a dose-dependent inhibition of colony size of the transformed cells. Adenosine cyclic 2':3'-monophosphoric acid (cAMP) and N6,O2'-dibutyryladenosine cyclic 3':5'-monophophoric acid potentiated this response. The presence of non-transformed 10T1/2 cells was required for this effect, since a concentration of IBX (10(-4) M) inhibitory for the growth of transformed cells in mixed cultures was without effect on the growth rate, plating efficiency, or saturation density of pure cultures of 10T1/2 cells or of their transformed counterparts. Conditioned medium removed from IBX-treated 10T1/2 cells was not growth inhibitory for transformed cells, indicating a requirement for cell-cell contact. IBX caused a dose-dependent increase in intracellular cAMP in confluent 10T1/2 cells and a more pronounced increase in cAMP concentration in the culture medium of these cells. The dose-response effects of IBX on growth inhibition of malignant cells in mixed cultures appear to correlate well with its ability to elevate cAMP levels. Thus, IBX increased the capacity of 10T1/2 cells to cause reversible growth arrest of transformed cells and appears to act in a manner analogous to the previously reported effects of serum.
Cancer Res 1979 Sep
PMID:Modulation of cellular interactions between C3H/10T1/2 cells and their transformed counterparts by phosphodiesterase inhibitors. 8 99

Eight human hematopoietic cell lines, five derived from blood of patients with Down's syndrome (DS) and three from normal persons, were treated with mitomycin C (MC) and caffeine at various dose levels and for various durations. An increased rate of chromosome aberrations was found in all treated cultures. The extent of aberrations was correlated with the dose levels and duration; no difference occurred in sensitivity between the group of DS and normal lines at all dose levels and for all durations. Studies on the effect of MC severely reduced cell viability, but no difference was found in the rate of reduction of viable cell counts between DS and normal lines. Inhibition of mitoses by MC in DS lines, however, seemed stronger than that in normal lines.
J Natl Cancer Inst 1977 Jul
PMID:Response of hematopoietic cell lines derived from patients with Down's syndrome and from normal individuals to mitomycin C and caffeine. 14 25

Posttreatment incubation with nontoxic doses of caffeine resulted in enhancement of cell lethality and inhibition of cell growth in L1210 mouse leukemia cells which had been exposed to a protein antibiotic, neocarzinostatin. In addition, caffeine treatment appeared to inhibit the eventual maturation of newly synthesized DNA in L1210 cells following exposure to this antibiotic. These results, indicating the existence of caffeine-sensitive repair in L1210 leukemia cells treated with neocarzinostatin, provide further evidence for DNA damage as a mechanism of the cytocidal action of the antibiotic.
Cancer Res 1979 May
PMID:Enhancement by caffeine of neocarzinostatin cytotoxicity in murine leukemia L1210 cells. 15 73

Incorporation and alkaline sucrose sedimentation studies of DNA from mouse L-cells have demonstrated the following effects of N-methyl-N-nitrosourea (MNU) and methyl methanesulfonate (MMS). Increasing the concentration of both agents increases the number of single-strand breaks or alkali-labile lesions of existing DNA, which affects the incorporation of [3H]thymidine into DNA by reducing its relative rate. DNA that is newly synthesized during the 1st hr in [3H]thymidine after MNU treatment is of lower molecular weight than is existing DNA with alkali-labile lesions in treated cells and is also lower than DNA synthesized in control cells. Such small segments formed in treated cells are elongated and joined to form high-molecular-weight DNA in the subsequent 4-hr chase in thymidine or 5-bromo-2'-deoxyuridine. Near-ultraviolet photolysis selectively degrades 5-bromo-2'-deoxyuridine-elongated DNA to segments that are nearly as small as those before chase. Further, caffeine (2 mM) present during the thymidine chase prevents nascent-strand elongation, although caffeine-insensitive chain growth occurs partly in MNU-alkylated cells. The MMS lesion (single-strand breakage in alkali) in existing DNA also temporarily interrupts replicative synthesis and makes short segments, but their elongation seems insensitive to caffeine. Our results indicate that MNU may produce both caffeine-sensitive interruptions (probably gaps), as ultraviolet damage does, and apurinic site-directed, caffeine-insensitive interruptions in nascent strands, while MMS may cause exclusively the latter. Further evidence for this is the caffeine potentiation of only MNU killing, like ultraviolet killing, of L-cells. The extent of such a specific MNU lesion is estimated to be no more than 4% of the total extent of methylation, predicting that the lesion that is accessible to caffeine-sensitive repair will be a minor product(s) other than N7-methylguanine. Mutagenic and carcinogenic effects of MNU, which are higher than those of MMS, could be ascribed to such a particular MNU lesion(s) and its repair.
Cancer Res 1975 Oct
PMID:Postreplication repair of alkylation damage to DNA of mammalian cells in culture. 16 68

The activity of cyclic 3':5'-nucleotide phosphodiesterase (PDE) (EC 3.1.4.17) was measured in cultured normal and neoplastic rat mammary epithelium. Total PDE activity in normal cells was 1.6 to 6 times higher than that in tumor cells over a concentration range of 0.01 to 1 mM cyclic adenosine 3':5'-monophosphate. PDE activity was distributed between the low-speed (4000 x g) particulate and supernatant fractions in both cell lines, with the particulate fraction possessing 60 to 70% of the total. Double reciprocal kinetic plots were nonlinear, suggesting the presence of high- and low-affinity PDE activities. Similar, but not identical biphasic curves obtained from both normal and neoplastic cells suggested that at least two different PDE activities were present in a membrane-bound as well as a soluble form. Apparent Michealis constants for the high-affinity enzyme ranged from 2 to 6 muM; the low-affinity enzyme was 1 mM. In the presence of 10 mM caffeine and at a substrate concentration of 1 muM, PDE activity was inhibited 40 and 80% of basal levels in normal and tumor cells, respectively. In general, the membrane-bound enzyme was inhibited to a greater extent than the soluble, regardless of the cell line examined. Although normal cells exhibited higher PDE activities in terms of total specific activity, when soluble activities were compared at low substrate concentrations, the opposite was the case. At a substrate concentration of 0.01 muM, normal cell, low-Km soluble specific activity was 40% less than comparable tumor cell activity. Our results support the contention that PDE is induced by its own substrate, cyclic adenosine 3':5'-monophosphate. In addition, they suggest that the low cyclic adenosine 3':5'-monophosphate steady-state levels characteristic of malignant cells are maintained by a soluble high-affinity isozyme of PDE.
Cancer Res 1976 Jun
PMID:Cyclic nucleotide phosphodiesterase activity in normal and neoplastic rat mammary cells grown in monolayer culture. 17 39

A short review of pathogenic factors in U.V. light skin carcinogenesis in the mouse is presented. Caffeine and theophylline applied locally during U.V. irradiation caused a 50 percent reduction of skin tumour induction in Swiss mice. These two chemicals are inhibitors of DNA postreplication repair, but they also raise the intracellular level of cyclic AMP by inhibiting cAMP phosphodiesterase with, as a consequence, a possible slowing down of cellular growth. Control experiments using three different chemicals capable of raising the cAMP level in epidermal cells gave negative results. These experimental data are compatible with our original hypothesis according to which production of skin cancers by U.V. radiation is in same way related to DNA repair which helps the cell to survive but allows or favours the occurrence of errors in cellular DNA.
Bull Cancer 1978
PMID:Ultraviolet light induction of skin carcinoma in the mouse; influence of cAMP modifying agents. 21 89

Enhancement of host cell reactivation (HCR) of ultraviolet (UV)-irradiated herpes simplex virus (HSV) was demonstrated in cell cultures pretreated with caffeine, hydroxyurea, or 5-bromodeoxyuridine (BrdUrd). The effect of caffeine on HCR was shown to depend on the time of drug treatment with respect to infection. In cultures treated with caffeine during the course of virus replication, the infectivity of irradiated HSV was reduced about nine-fold, while cultures pretreated with the drug before infection showed an increase in infectivity. The extent of HCR enhancement depended on the time interval between treatment with caffeine and infection, drug concentration, and the UV irradiation dose to which HSV was exposed. Magnitude of enhancement of HCR by caffeine differed in various cell species. The results suggest that enhanced HCR of UV-irradiated HSV by DNA antimetabolities is associated with DNA repair activated in consequence of cell DNA damage.
Int J Cancer 1979 May 15
PMID:Enhancement of host cell reactivation of ultraviolet-irradiated Herpes simplex virus by caffeine, hydroxyurea and 5-bromodeoxyuridine. 22 93

We have used the technique of host cell reactivation of UV-irradiated herpes simplex virus type 1 as a measure of the repair capacity of three Bloom's syndrome skin fibroblast strains. At low multiplicity of infection (less than 6 x 10(-4) plaque-forming unit/cell), reactivation of the virus by the Bloom's syndrome strains was indistinguishable from that by normal strains. Reactivation at higher multiplicities was measured using an infectious centers assay. At 3 plaque-forming units/cell, survival of UV-irradiated herpes simplex virus was higher in all cell strains as a result of the multiplicity reactivation effect. This effect was, however, much smaller in one Bloom's syndrome strain, GM1492, than in either the normal strains or the other Bloom's syndrome fibroblasts. The defect in GM1492 was manifest only at relatively high multiplicates of infection. Thus, at 0.01 plaque-forming unit/cell, the GM1492 strain appeared normal, using the infectious centers assay. Clonal survival of the UV-irradiated GM1492 fibroblasts was also normal. Caffeine at 4 mM had little effect on either virus or cell survival following UV irradiation. The results indicate that the Bloom's syndrome strain GM1492 may be deficient in one of the cellular functions responsible for the multiplicity reactivation effect. These effects include complementation and recombinational events. Alternatively, the GM1492 strain may have a defective UV repair system which becomes saturated at high levels of damage.
Cancer Res 1979 Sep
PMID:Defective reactivation of ultraviolet light-irradiated herpesvirus by a Bloom's syndrome fibroblast strain. 22 21

A well-documented rationale exists for the study of the induction of cancer at the cellular level. Transformation can be quantitated; its frequency follows a linear relationship with dose and is consistent with a "one-hit" phenomenon. Transformed colonies do produce transformed lines with attributes of neoplastic cells including the production of tumors; in vitro activity correlates with in vivo activity to provide evidence that chemically induced carcinogenesis can be studied in vitro. In vitro techniques utilizing mammalian cells in culture have made possible the rapid evaluation of carcinogenicity of agents in man's environment. Neoplastic transformation is inductive and not the result of the selection of preexisting tumor cells. The addition of a host-mediated step in the bioassay makes it possible to decrease the number of false negatives, which may result from the requirement for metabolic activation of the chemical. Thus the in vitro studies described have a high probability of providing practical methods for determining which chemicals in use have a potential of producing cancer. Furthermore, the nature of the cell-target insult interaction can be determined, as well as the chemical nature of the ultimate carcinogen, the degree to which any agent acts alone, be it a chemical, a virus, or irradiation, and the extent to which one agent interacts with another from the same or a different category of carcinogens. Sequential treatment involving chemicals, viruses, and radiation are important, since combinations of various agents may be responsible for an increased risk of cancer in laboratory animals and human populations. The use of multiple agents may also lead to different but specific new types of assays to use for surveillance of our environment for carcinogenic agents. Pretreatment of Syrian golden hamster embryo cells with either X-irradiation or methyl methanesulfonate, but not UV-irradiation, increases the frequency of chemical transformation as does posttreatment with caffeine. Most, if not all, chemical carcinogens will increase the sensitivity of hamster embryo cells to transformation by a carcinogenic simian adenovirus SA7. The enhancement of virus transformation is related to both the length of chemical treatment and the interval between chemical and viral addition. The mechanism of transformation enhancement by various agents has yet to be explained. They may affect a number of molecular processes or cause a modification of existing DNA and thus provide an explanation for carcinogenesis; in fact, in some systems some of these agents may also show mutagenic activity and produce chromosomal aberrations, However, although DNA is the critical site for a mutagen, the critical target(s) of chemical carcinogens is still unknown.
Natl Cancer Inst Monogr 1978 May
PMID:In vitro carcinogenesis with cells in early passage. 37 16


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