Diammine Dichloride Research Articles

Optimization of the efficiency of cross-linking PtIIoligonucleotide phosphorothioate complexes to complementary oligonucleotides

We have investigated the efficiency with which PtII complexes cross-link phosphorothioates of oligonucleotides to complementary DNA targets. The A and G residues 2-5 bases downstream from the 5'-phosphorothioate group are preferred sites for cross-linking. Replacement of residues in this part of the target by T residues results in greatly decreased cross-linking when cis platinum diammine dichloride (cisPtII) or potassium platinous chloride (K2PtCl4) are used. Trans platinum diammine dichloride (transPtII) forms cross-links with T residues if A and G residues are absent from the susceptible region of the target. Oligomers containing an internal phosphorothioate group can also be linked to their templates with transPtII, but not with cisPtII or K2PtCl4. Cross-linking via an internal phosphorothioate group tends to be less efficient than cross-linking via a 5'-terminal phosphorothioate. The Sp isomers of internal phosphorothioates are cross-linked more efficiently than the Rp isomers. Preliminary experiments suggest that the efficiency of cross-linking to RNA targets will prove similar to that found for DNA targets.

Radio-adaptive response: characterization of a cytogenetic repair induced by low-level ionizing radiation in cultured Chinese hamster cells

Pretreatment with low doses of β-rays from incorporated tritiated thymidine ([ 3H]dThd) or of Co-60 γ-rays (1 or 5 cGy) rendered actively growing Chinese hamster V79 cells more resistant to the induction of micronuclei or sister-chromatid exchanges (SCEs) by a subsequent high dose of γ-rays (1 Gy). This adaptive response to ionizing radiation (radio-adaptive response) can be induced by an optimal range of low doses of 3H β-rays, but not by much lower or higher adapting doses. Full expression of the adaptive response induced by the exposure to low doses of 60Co γ-rays occurred 4 h after the adapting dose. The cells pre-exposed to low doses of γ-rays showed cross-resistance to challenge doses of γ-rays themselves and also of mitomycin C(MMC) and near ultraviolet light (UV-B, 313 nm), but not to those of ethyl methanesulfonate (EMS) or cis-platinum (II) diammine dichloride (cisplatin) for SCE induction. These results suggest that the radio-adaptive response mechanistically couples to the repair network which copes with chromatin lesions induced by MMC and UV-B.

Inhibition of plasma membrane redox activities and elongation growth of soybean

NADH‐ferricyanide oxido‐reductase (EC 1,6,99,3) of purified plasma membrane vesicles isolated by aqueous two‐phase partition from segments of etiolated soybean [Glycine max (L.) Merr. cv. Williams] hypocotyls was used as a measure of plasma membrane redox activity. Elongation growth of hypocotyl segments floated on the solutions was determined in parallel. Cis‐platinum (II) diammine dichloride (cis‐platin), adriamycin and p‐nitrophenylacetate, agents known to inhibit cell proliferation and plasma membrane redox activities in mammalian cells inhibited both NADH‐ferricyanide oxido‐reductase of the isolated membrane vesicles and elongation growth of intact hypocotyl segments. Auxin(2,4‐dichlorophenoxyacetic acid)‐induced growth of the isolated segments was inhibited preferentially at drug concentrations where control growth was affected only slightly. The findings suggest a connection between plasma membrane redox reactions and the control of elongation growth in plants.

Isolation of alkylating agent-sensitive Chinese hamster ovary cell lines.

Six derivatives of a Chinese hamster ovary cell line have been isolated by selection for hypersensitivity to the cytotoxic effects of the monofunctional alkylating agent methyl methane sulphonate (MMS). These cells are up to 6-fold more sensitive to MMS than the parental line, as estimated from D37 values, and are cross-sensitive to methyl nitrosourea, as well as to the ethyl derivatives of these drugs. Comparisons of their sensitivities to the bifunctional alkylating agents cis-platinum (II) diammine dichloride, mitomycin C and melphalan reveals marked phenotypic diversity, with only one mutant, designated MMS-2, exhibiting appreciable hypersensitivity to all of these agents. No striking hypersensitivity to radiation or to the purine analogue caffeine is apparent in any of the mutant lines. Based on their profiles of sensitivity to DNA damaging agents, it would appear that these mutants are phenotypically unlike any previously described mammalian cell mutants and probably represent a number of different genetic complementation groups. These mutants may facilitate an investigation into the mechanisms of repair of alkylation damage in mammalian cells and could prove to be suitable hosts for the cloning of human DNA repair genes.

Regrowth assay method for quantitative evaluation of drug-induced cell damage in vitro: clarification of cell reduction kinetics of anticancer drugs and differential drug sensitivities of genitourinary cancer cell lines.

Growth kinetic curves of various human genitourinary cancer cell lines following treatment with an anticancer drug were determined to find a reliable index of cell damage. They showed a triphasic growth pattern consisting of growth inhibition phase, exponential growth phase (regrowth phase) and stationary phase. The percent survival at the turning point from growth inhibition phase to regrowth phase was considered to be a reliable cell damage index indicating to what extent the proliferative capacity of a cell population was impaired by treatment with the drug.Dose-response curves determined by this assay procedure of cell damage (regrowth assay method) clarified the cell reduction kinetics of cis-plati-num (II) diammine dichloride and bleomycin that would provide a rational basis for the mode of their administration in clinical use. They also disclosed the differential drug sensitivities among the cell lines derived from cancers of the different organs represented by HeLa S3, KU 1 and KU 2 and among those from cancers of the same histological type represented by KU 2, NRC 12 and OUR 10 from renal cell carcinoma and KU 1, MGH-U1 and T 24 from transitional cell carcinoma of the bladder. These results suggested that, as the increasing number of human cancer cell lines is established, correlation be-tween drug sensitivity and morphological and functional properties of cancer can be investigated in vitro and the results might provide a rational basis for drug selection.It was concluded that the regrowth assay method to determine drug-induced cell damage in vitro not only has a wide applicability but also is reli-able enough to clarify the cell reduction kinetics of anticancer drugs and the differential drug sensitivities among various genitourinary cancer cell lines.

DNA repair mechanisms and cytotoxicity of antitumour alkylating agents and neutral platinum complexes.

There are many indications that the cytotoxic action of a number of different antitumour agents, including chlorambucil and cis-platinum (II) diammine dichloride, is due to their ability to react with DNA and thereby inactivate it as a template for DNA replication. Moreover, the sensitivity of cells to these agents is related to their ability, either to remove the damage from DNA by some form of excision repair process, or to circumvent the lesions during DNA replication by so-called post-replication repair.

G 1 phase chinese hamster V79-379A cells are inherently more sensitive to platinum bound to their dna than mid S phase or asynchronously treated cells

The importance of expressing cell sensitivity in terms of extent of platinum bound to DNA is demonstrated using HeLa and Chinese hamster V79-379A cells. HeLa cells were found to be slightly more sensitive to cis platinum {II} diammine dichloride ( cis Pt {II}) for a given extent of platinum binding to DNA compared with Chinese hamster V79-379A cells, although the difference between the two cell lines was less than that indicated by dose-survival data. Chinese hamster cells in the G 1 phase of their cell cycles were more sensitive to treatment with cis Pt {II} than cells in other phases of the cell cycle or than cells in an asynchronous cell culture. This sensitivity of G 1 phase cells was not due to an increased uptake of platinum into the cells but rather reflected an inherent increase in sensitivity of these cells to a given binding of cis Pt {II} to their DNA. Chinese hamster cells were inherently more sensitive to the drug when they were treated in a stationary growth phase followed by dilution as compared with treatment in an exponential growth phase.

The interaction of antitumour platinum compounds with cellular DNA in cultured cells and animal tissues: relationship to DNA cellular repair processes

Summary Hela and Chinese hamster cells in the G1 phases of their cell cycles are more sensitive to treatment with cis platinum (II) diammine dichloride (cis Pt(II)) than cells in other phases of the cell cycle and than the corresponding cell in asynchronous culture. The increased sensitivity of G1 phase cells is not due to an increased uptake of platinum into cells but reflects an inherent increase in the sensitivity of these cells to platinum bound to their DNA. Similarly, stationary phase Hela and Chinese hamster cells which are diluted to a cell number which permits growth immediately after treatment are more sensitive to cis Pt(II) than exponentially growing cells. Fibroblasts which were obtained from Xeroderma pigmentosum (XP) patients and which were deficient in the repair of UV-irradiation induced thymine dimers were more sensitive both to UV-irradiation and to platinum bound to their DNA than were normal human fœtal lung cells. It is presumed therefore that this difference in response to DNA bound platinum reflects the greater capacity of normal cells, as compared with XP cells, to excise platinum adducts from their DNA. Following treatment of animals bearing a plasmacytoma with cis platinum (II) diammine dichloride the extent of binding of platinum to the DNA of tumour cells was comparable with that to the DNA of cells in culture treated with an equitoxic dose of the drug, a finding which supports the concept that DNA in cells is the target for cis Pt(II) both in vivo and in vitro. The time course of binding of platinum to the DNA of both tumour and liver cells indicates that excision repair processes probably also operate in vivo. The levels of reaction of a number of platinum drugs with the DNA of cultured cells following their treatment with concentrations producing measured effects on cell survival have been compared with similar data obtained with cis Pt(II). Differences were found in the effectiveness of lesions on the DNA introduced by the various congeners of cis Pt(II).

A review of clinical experience with cis-platinum diammine dichloride : 1972–1978

A review of clinical experience with cis-platinum diammine dichloride : 1972–1978

23 Excision repair of cis platinum II diammine dichloride induced damage to DNA of chinese hamster cells

23 Excision repair of cis platinum II diammine dichloride induced damage to DNA of chinese hamster cells

Increased sensitivity of UV-repair-deficient human cells to DNA bound platinum products which unlike thymine dimers are not recognized by an endonuclease extracted from Micrococcus luteus

We have studied the response of human cells in culture to cis platinum[II] diammine dichloride ( cis Pt[II]) induced DNA damage. The survival data, measured as a function of cis Pt[II] dose were similar in a normal cell line (Human foetal lung) compared to a UV-sensitive, thymine dimer excision repair-deficient cell line (Xeroderma pigmentosum). However, there was a marked difference between the two cell lines when binding to DNA was plotted against dose of cis Pt[II] given for 1 h. When these findings were expressed as cell survival versus binding to DNA, a 4.1-fold difference between the slopes of the survival curves for the two cell lines was obtained. These findings are consistent with the notion that normal cells are able to excise cisPt[II] induced damage from their genome and thus increase their ability to survive as compared to excision-deficient cells. An endonuclease preparation from Micrococcus luteus is able to recognise UV damage in DNA, but did not recognise cis Pt[II] induced damage. These results possibly indicate differences in the pathways of repair of damage caused by the two agents.

High dose Cis-platinum diammine dichloride.Amelioration of renal toxicity by mannitol diuresis

A clinical trial was undertaken to improve the therapeutic index of cis-platinum diammine dichloride with a concomitantly administered mannitol induced diuresis. Sixty patients, heavily pretreated, were entered; fifty-one are evaluable. The technique of concomitant osmotic diuresis and CPDD administration is described in detail. Doses ranged from 3 mg/kg to 5 mg/kg. At 5 mg/kg, dose-limiting renal, marrow and ototoxicity were seen, and resulted in one drug death. Marrow toxicity was moderate. Renal toxicity was limited to transient elevations in serum creatinine levels, except in some patients who had renal impairment prior to CPDD treatment. These patients had moderate renal toxicity. Serial treatments as frequently as once every 3 weeks were used to maintain responses. Serial high dose CPDD produced only mild renal dysfunction. Ototoxicity, usually subclinical, was quantitated audiometrically, and found to be dose related, but not clinically prohibitive at 4 mg/kg or less. The overall response rate (PR/MR) was 42%. Clinically significant responses in epidermoid carcinoma of the head and neck, adenocarcinoma of the ovary, and germ cell tumors of the testis were seen. All six responding patients with germ cell tumor of the testis, had been resistant to low dose (1mg/kg) CPDD. Two responding patients with ovarian adenocarcinoma had been resistant to alkylating agents.

Post-replication repair of DNA in chinese hamster cells treated with CIS platinum (II) diamine dichloride. Enhancement of toxicity and chromosome damage by caffeine

The anti-tumor agent cis platinum (II) diammine dichloride ( cis Pt(II)) caused chromosomal abnormalities in Chinese hamster V79–379A cells. The time of appearance of these abnormalities suggested that they arise as a consequence of DNA synthesis on a damaged template. The yield and severity of chromosomal abnormalities was greatly enhanced by a non-toxic concentration of caffeine, and this enhancement was associated with a potentiation of cis Pt(II) induced cell death. These results suggest that damage to DNA which arises from cis Pt(II) treatment can be repaired in this cell line by a caffeine-sensitive post-replication repair process.

Interactions between mammalian cell DNA and inorganic platinum compounds—I: DNA interstrand cross-linking and cytotoxic properties of platinum(II) compounds

The effects of cis and trans Pt(II)diammine dichloride on the colony forming ability of HeLa cells have been measured. Higher doses of trans Pt(II)diammine dichloride than the cis isomer had to be administered to cells to produce equal effects on cell survival. Determination of the amount of drug bound to cellular macromolecules showed that more of the trans compound was bound to DNA than cis when cell survival was reduced by the same amount, suggesting there was a real difference in the mechanisms of action of the two isomers. The levels of reaction of cis and trans Pt(II)diammine dichloride at known toxic concentrations with DNA. RNA and protein supported the hypothesis that DNA is the primary target of the platinum(II)compounds. The ability of equal doses of cis and trans Pt(II)- diammine dichloride to form DNA interstrand cross-links differed less when isolated DNA was used than when whole cells were treated with these agents. The difference in cross-linking ability of the two compounds in whole cells could explain the difference in toxicity between the cis and trans isomers. The importance of DNA interstrand cross-linking as a cytotoxic event in its own right, and as a possible indicator of other cytotoxic lesions is discussed.