Biomedical subjects

A C Plooy

Publications and source records attributed to A C Plooy.

5 recordsLinked to original sources

PubMed1985

Influence of treatment temperature on the genotoxic effects of cisplatin in CHO cells: cytotoxicity, mutagenicity and induction of lesions in DNA.

In cells exposed in vitro to the cytotoxic and mutagenic antitumor drug cisplatin (cis-Pt(NH3)2Cl2), various adducts with nuclear DNA are formed. A comparative study was made of the influence of temperature variation during treatment of cultured Chinese hamster ovary (CHO) cells with cisplatin on cytotoxicity, mutation induction and Pt-DNA adduct formation. Before and after treatment (1 h at 32, 37 or 40 degrees C) cells were kept at 37 degrees C. Cytotoxicity increased with temperature; D0 values were 29.6 +/- 1.6, 21.1 +/- 1.2 and 11.4 +/- 0.6 microM at 32, 37 and 40 degrees C, respectively. Pt-DNA binding to DNA at 40 degrees C was 2.0 (+/- 0.3) times as high as at 32 degrees C. This factor remained practically constant over a 24-h post-treatment incubation of the cells, during which about 60% of DNA-bound Pt were removed. As the increase in cytotoxicity between 32 and 40 degrees C was roughly in proportion to that in Pt binding, no substantial changes in the spectrum of adducts appeared to occur. The induction of DNA interstrand cross-links, studied at 32 and 40 degrees C, varied linearly with dose. Influence of temperature on cross-link formation was comparable to that on total Pt binding. Amounts of cross-links highly increased during 24 h after treatment. Plots of cross-links against survival after treatments at 32 and 40 degrees C almost coincided. Induction of 6-thioguanine-resistant (HGPRT) mutants at various cisplatin concentrations did not show a clear temperature dependency. Consequently, equitoxic treatments were significantly more mutagenic at 32 degrees C than at 40 degrees C, the opposite of what has been reported for E. coli.

Animals↗

PubMed1985

The quantitative detection of various Pt-DNA-adducts in Chinese hamster ovary cells treated with cisplatin: application of immunochemical techniques.

With polyclonal antibodies raised against cis-Pt(NH3)2Guo-GMP, small quantities of specific Pt-adducts could be detected in DNA from Chinese hamster ovary (CHO) cells treated with the antitumor agent cisplatin, after the DNA had been digested with nucleases and the degradation products separated by anion-exchange chromatography (FPLC). Directly after treatment with 83 microM cisplatin, resulting in 97 X 10(-6) platinum atoms bound per nucleotide, 35.9 +/- 4.7% of the platinum was recovered as cis-Pt(NH3)2d(pGpG), derived from intrastrand cross-links on two neighboring guanines, 3.1 +/- 1.6% as cis-Pt(NH3)2d(GMP)2, the degradation product of interstrand cross-links on two guanines (0.07%, according to separate studies) and of intrastrand cross-links on two guanines separated by one or more bases. The immunochemical method was not sensitive enough for the detection of monofunctionally bound platinum on guanine residues. The amount of these adducts, present in the digests as Pt(NH3)3dGMP, could be established with atomic absorption spectroscopy (AAS) (38.5% of the total Pt-content of the DNA). After a post-treatment incubation of the cells for 24 h, the total amount of platinum decreased to 59 X 10(-6) atoms per nucleotide, indicating the removal of adducts. In the digests, cis-Pt(NH3)2d(pGpG) accounted for 46.4 +/- 6.8% of the total Pt-content, cis-Pt(NH3)2d(GMP)2 for 3.0 +/- 0.9% (0.34% derived from DNA interstrand cross-links). The amounts of monofunctional adducts had decreased to such an extent that the exact quantities (below 15%) could not be determined. According to AAS-assays, at the elution position of cis-Pt(NH3)2d(pApG) a significant amount of Pt-product was present, both at t = 0 and 24 h, but the signals did not allow quantitative evaluation (however, below 48% and 28%, respectively). The possible role of the individual lesions in the DNA in the biological effects of this platinum compound in CHO cells is discussed.

Animals↗

PubMed1985

Formation and repair of DNA interstrand cross-links in relation to cytotoxicity and unscheduled DNA synthesis induced in control and mutant human cells treated with cis-diamminedichloroplatinum(II).

A comparative study was performed with a variety of human cell lines on the effects of treatments with cis-diamminedichloroplatinum(II) (cisplatin) on cell survival and the induction of unscheduled DNA synthesis. In addition to control fibroblasts (Han, MB), cell lines defective in DNA repair were used [xeroderma pigmentosum, XP(A) and XP(F), and Fanconi's anemia (FA)], as well as cells deficient in arylsulfatase A (mucolipidosis II, ML1 and ML2). Ultraviolet light and mitomycin C were included in this study as model DNA-damaging agents. Furthermore, induction of DNA interstrand cross-links by cisplatin and their repair were studied. As for survival, only XP cells were abnormally sensitive to ultraviolet light, and only FA cells were abnormally sensitive to mitomycin C. To cisplatin, however, all mutants tested were more sensitive (2 to 5 times) than were normal cells. Unscheduled DNA synthesis induction by ultraviolet light was strong in all but the XP cells; the other two agents did not induce unscheduled DNA synthesis. Induction of DNA interstrand cross-links by cisplatin was linear with dose. Formation continued for up to 18 to 24 h after treatment. During this period, all cells but the ML mutants responded similarly. In ML cells, much fewer cross-links were induced, which were repaired rapidly. In FA cells, accumulation continued for at least 96 h; in the other cells, most of the cross-links had been removed after that period. In the discussion, the cisplatin-induced DNA interstrand cross-links are proposed as an important potentially lethal lesion, in view of their persistence in the highly sensitive FA cells. Furthermore, the possible involvement of certain steps of the long-patch excision repair pathway in the removal of this lesion is considered. The sensitivity of ML cells to cisplatin is attributed to cytoplasmic effects, rather than to chromosomal damage.

Cell Line↗

PubMed1984

Induction and repair of DNA cross-links in chinese hamster ovary cells treated with various platinum coordination compounds in relation to platinum binding to DNA, cytotoxicity, mutagenicity, and antitumor activity.

Several effects of four diamminechloroplatinum compounds (II and IV) in Chinese hamster ovary cells were studied. The two cis-compounds [cis-diamminedichloroplatinum(II) and cis-diamminetetrachloroplatinum(IV)] are known to possess antitumor activity, whereas the two trans-stereoisomers [trans-diamminedichloroplatinum(II) and trans-diamminetetrachloroplatinum(IV)] are inactive. When the effects of the cis-and trans-platinum compounds were compared after treatments that resulted in the binding of equal amounts of platinum to the DNA of the cells, the following differences were found: (a) the cis-platinum adducts gave a much higher cytotoxicity; (b) only the cis-platinum-DNA complexes were strongly mutagenic (forward mutations at the hypoxanthine-guanine phosphoribosyltransferase locus); (c) the cis-platinum adducts induced more sister chromatid exchanges; (d) the cis compounds initially induced fewer DNA-protein cross-links (Factors 5 to 8), but these cis-platinum cross-links were much more persistent; (e) for both cis complexes, the amount of DNA interstrand cross-links passed through a maximum between 6 and 12 hr after treatment, and the cross-links were repaired slowly. One trans-compound [trans-diamminetetrachloroplatinum(IV)] resembled the cis complexes with respect to the overall kinetics of formation and disappearance of this type of lesion, but the repair went faster. For the other trans compound [trans-diamminedichloroplatinum(II)], the highest number of cross-links was detected directly after the treatment of the cells, and they were rapidly eliminated. Neither the number of platinum-DNA lesions as such nor the initial amount of DNA interstrand cross-links could be related to the (geno)toxic effects of the compounds. However, as the slow repair of the cis-platinum-induced interstrand and DNA-protein cross-links leads to a certain persistency of these adducts, the unrepaired lesions might be responsible for cytotoxicity, mutagenicity, and antitumor activity. This indicates discriminating properties of the repair systems for certain cis-or trans-platinum-DNA adducts. The sister chromatid exchange induction seems to be related to the persistent DNA interstrand cross-links.

Animals↗

PubMed1980

Platinum compounds with anti-tumour activity.

Ten platinum (Pt) coordination complexes with different ligands, comprising both Pt(II) and Pt(IV) complexes of which the cis-compounds all possessed at least some anti-tumour activity and the trans-compounds were inactive, were tested as to their effect on cell survival and the induction and repair of DNA damage in cultured Chinese hamster cells (CHO). The tests used were the determination of cytotoxicity, inhibition of the semi-conservative DNA replication, induction of damage in DNA and mutagenicity. The Pt-compounds could be divided in 3 groups on the basis of their cytotoxicity. The compounds with high cytotoxicity were also active anti-tumour drugs, but a clear correlation between cytotoxicity and anti-tumour activity was not observed. All compounds inhibited semi-conservative DNA synthesis and induced DNA repair replication. No induction of DNA single strand breaks and DNA cross-links was detected. However, the occurrence of alkali labile sites in the DNA of treated CHO cells demonstrated the induction of unidentified DNA base damages. The 4 compounds tested so far, 2 cis- and 2 trans-Pt complexes, induced mutations in CHO cells, leading to resistance to 6-thioguanine; the cis-compounds were more mutagenic than the trans-compounds.

Alkalies↗