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At least 919 records · Page 51Linked to original sources
PubMed1975

Mode of action of antitumour antibiotics. spectrophotometric studies on the interaction of chromomycin A3 with DNA and chromatin of normal and neoplastic tissue.

The binding of chromomycin A3, an antitumour antibiotic, to various DNA and chromatin isolated from mouse and rat liver, mouse fibrosarcoma and Yoshida ascites sarcoma cells was studied spectrophotometrically at 29 degrees C in 10-2 M Tris-HCl buffer, pH 8.0, containing small amounts of MgCl2 (4.5-10-5--25-10-5 M). An isobestic point at 415 nm was observed when chromomycin A3 was gradually titrated with DNA/chromatin and its spectrum shifted towards higher wavelength. The rates and extent of these spectral changes were found to be dependent on the concentration of Mg2+. The change in absorbance at 440 nm was used to calculate apparent binding constant (Kap M-1) and sites per nucleotide (n) from Scatchard plots for various DNA and chromatins. As expected, values of n for chromatin (0.06-0.10) were found to be lower than found for corresponding DNA (0.10-0.15). Apparently no such correlation exists between binding constants (Kap M-1)-10-4) of DNA (6.4--11.2) and of chromatin (3.1--8.3), but Kap M-1 of chromatin isolated from mouse fibrosarcoma and Yoshida ascites sarcoma are 1.5--3 times higher than that found for mouse and rat liver chromatin. These differences may be taken to indicate structural difference in nucleoprotein complexes caused by neoplasia. The relevance of this finding to tumour suppressive action of chromomycin A3 is discussed.

Animals↗
PubMed1983

Isophosphoramide mustard, a metabolite of ifosfamide with activity against murine tumours comparable to cyclophosphamide.

Isophosphoramide mustard was synthesized and was found to demonstrate activity essentially comparable to cyclophosphamide and ifosfamide against L1210 and P388 leukaemia. Lewis lung carcinoma, mammary adenocarcinoma 16/C, ovarian sarcoma M5076, and colon tumour 6A, in mice and Yoshida ascitic sarcoma in rats. At doses less than, or equivalent to, the LD10, isophosphoramide mustard retained high activity against cyclophosphamide-resistant L1210 and P388 leukaemias, but was less active against intracerebrally-implanted P388 leukaemia while cyclophosphamide produced a 4 log10 tumour cell reduction. It was also less active (one log10 lower cell kill) than cyclophosphamide against the B16 melonoma. Metabolism studies on ifosfamide in mice identified isophosphoramide mustard in blood. In addition, unchanged drug, carboxyifosfamide, 4-ketoifosfamide, dechloroethyl cyclophosphamide, dechloroethylifosfamide, and alcoifosfamide were identified. The latter 4 metabolites were also identified in urine from an ifosfamide-treated dog. In a simulated in vitro pharmacokinetic experiment against L1210 leukaemia in which drugs were incubated at various concentrations for various times, both 4-hydroxycyclophosphamide and isophosphoramide mustard exhibited significant cytoxicity at concentration times time values of 100-1000 micrograms X min ml-1, while acrolein was significantly cytotoxic at 10 micrograms X min ml-1. Treatment of mice with drug followed by L1210 cells demonstrated a shorter duration of effective levels of cytotoxic activity for isophosphoramide mustard and phosphoramide mustard in comparison with cyclophosphamide and ifosfamide. Isophosphoramide mustard and 2-chloroethylamine, a potential hydrolysis product of isophosphoramide mustard and carboxyifosfamide, were less mutagenic in the standard Ames test than the 2 corresponding metabolites of cyclophosphamide [phosphoramide mustard and bis(2-chloroethyl)amine].

Adenocarcinoma↗
PubMed1990

Antitumor effect of the new rhodium (II) complex: Rh2 (form)2 (O2 CCF3)2 (H2O)2 (form = N,N'-di-p-tolyl formamidinate).

The new rhodium(II) complex Rh2(Form) (O2CCF3)2(H2O)2 (Form = N,N'-di-p-tolyl formamidinate) was evaluated for its toxicity on the rat and for its efficacy against two tumors of this animal: the Yoshida ascites sarcoma and the T8 sarcoma of Guérin. The rhodium(II) formamidinate shows very low toxicity: in fact 150 mg/kg (the highest quantity of drug soluble in 4 ml of dimenthyl sulfoxide) is not toxic for rats. We were unable to establish the lethal dose or the highest nontoxic dose since larger mounts of complex require a dose of dimethyl sulfoxide (DMSO) that is itself toxic and the compound is insoluble in other solvents such as water or Tween. Doses of rhodium(II) formamidinate, varying from 3 to 30 mg/kg, were administered once by i.p., i.v., i.m. and intratumor (i.t.) route from 1 to 7 days after i.p. injection of 10(6) Yoshida ascites sarcoma cells and subcutaneous (s.c.) implantation of approximately 300 mg (corresponding to 2-3 x 10(7) living tumor cells) of T8 sarcoma of Guérin. The compound is active when administered i.p. 24 hours after Yoshida ascites sarcoma at the smallest dose tested (3 mg/Kg), increasing the average life span of 62.3% and allowing the survival of 50% of the rats. It is also active when administered i.p. at the highest dose tested (30 mg/Kg) 7 days after tumor cell challenge, increasing the average life span in 43.8% and allowing survival in 20% of the rats; it is not active after i.v. or i.m administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Nilemycin, an intercalating agent for deoxyribonucleic acid.

1. Nilemycin (NM) is found to exert an inhibitory effect on the mouse tumor Sarcoma 180 near toxic doses but not with Leukemia 1210. 2. In Yoshida rat sarcoma cells NM inhibits cellular de novo nucleic acid synthesis and protein to a much lesser extent. 3. More than 50% inhibition by NM to de novo synthesis of RNA, in a system using calf thymus DNA as a template, could be observed. 4. Suitable levels of NM reduce the S values of DNA. 5. The antibiotic induced metachromatic changes in the u.v. spectrum of DNA solutions. 6. NM markedly inhibited the polynucleotide ligase repairing action on DNase-1-nicked DNA. 7. It is presumed that NM intercalates nicked DNA into such a configuration that the reactive sites of the polynucleotides are inaccessible to the ligase activities.

Animals↗