Standardization of the Alkaline Elution Procedure Using X-Ray-Damaged Nuclear DNA

Measurement of DNA single-strand breaks by alkaline elution and fluorometric DNA quantification

The method presented is based on the alkaline elution procedure for the determination of DNA single-stand (ss) breaks developed by Kohn and on the principles of DNA quantification after binding with the dye Hoechst 33258. In the present study, modification of the alkaline elution procedure with regard to the elution solution volume was performed. The influences of the DNA strandedness, the ethylenediaminetetraacetate/tetraethylammonium hydroxide denaturation and elution solution presence, the DNA solution pH, the dye amount, and the incubation time for the formation of the dye-ssDNA complex on the DNA fluorometric quantification were also studied. The modified DNA alkaline elution procedure followed by the optimized fluorometric determination of the ssDNA was applied on liver tissue from both untreated and treated (N-nitroso-N-methylurea- administered) Wistar rats. The criteria for the selection of the appropriate estimator and statistical analysis of the obtained results are also presented. The method of the DNA alkaline elution followed by fluorometric determination of ssDNA as modified and evaluated is an accurate and reliable approach for the determination of in vivo induced ssDNA strand breaks.

Synthesis, antitumor activity, distribution and toxicity of 4-[4-[bis(2-chloroethyl)amino]phenyl]-1-hydroxybutane-1 1-bisphosphonic acid (BAD), a new lost derivative with increased accumulation in rat osteosarcoma

The aim of this study was to investigate whether the newly synthesized bisphosphonic acid-linked N-Lost derivative BAD retains bone-seeking and cytostatic properties. The paper describes experiments on mutagenicity in vitro and on toxicity in vivo. BAD is characterized by very low mutagenic activity toward histidine auxotrophic Salmonella typhimurium strains. Cytotoxic effects were tested in rat osteosarcoma and in Walker carcinosarcoma 256B. The LD50 of i.v. injected BAD was 146 mg/kg. Acute toxicity is probably caused by calcium complexing of the bisphosphonate part of the molecule. Labeling experiments showed moderate accumulation in bone and osteosarcoma, as well as in lung metastases. BAD effected high tumor growth inhibition in osteosarcoma and Walker carcinosarcoma-bearing rats and marked prolongation of survival; histologic and radiographic examination revealed rapid calcification of osteosarcoma and lung metastases. BAD-pretreatment produced protective effects against osteolysis induced by intratibially implanted Walker carcinosarcoma ascites cells. The cytostatic efficacy of equitoxic doses of BAD in rat osteosarcoma is comparable to that of dacarbazine and in Walker carcinosarcoma to that of melphalan.

Comparison of DNA damage in various tissues, myelosuppression and serum levels of transaminases and bilirubin in tumor-bearing female Sprague-Dawley rats treated with 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea (HECNU)

Female Sprague-Dawley rats bearing methylnitrosourea-induced mammary carcinomas were treated with 100 mumol 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea (HECNU)/kg to investigate the time course of DNA-DNA interstrand cross-linking (DNA-XL) as measured by alkaline elution in tumor, bone marrow and liver cells. The inhibition of bone marrow stem cell colony formation in culture (CFU-C) and in spleens of lethally irradiated mice (CFU-S), serum transaminase levels and total bilirubin were concomitantly determined. All parameters were evaluated at different times from 4 to 72 h after treatment. The highest amounts of DNA-XL were found in tumor cells, peaking at 24 h after treatment. A parallel increase was observed in bone marrow cells up to 16 h with a subsequent rapid decrease to about one-third of DNA-XL in tumor cells after 72 h. Concomitantly, CFU-C and CFU-S were suppressed, the nadir being at 24 h after treatment. In liver cells, however, constant low levels of DNA-XL were found, which had disappeared after 48 h. In accordance with this observation, serum transaminase levels were only slightly elevated.

Experiments on the efficacy and toxicity of locoregional chemotherapy of liver tumors with 5-fluoro-2'-deoxyuridine (FUDR) and 5-fluorouracil (5-FU) in an animal model

For the investigation of locoregional chemotherapy of liver neoplasms we developed a standardized animal model in the rat. Continuous infusion therapy or repeated bolus injections of FUDR or 5-FU were given via the hepatic artery, the portal vein or the vena cava in tumor-bearing animals. The efficacy of the treatment was determined by measuring the tumor volume 3 weeks after tumor cell implantation. For the evaluation of the local and systemic toxicity serum GOT, GPT, and total bilirubin were determined. DNA single strand breaks were assessed in isolated liver and bone marrow cells. Inhibition of colony formation of bone marrow stem cells was determined by CFU-C and CFU-S bioassay. A significant reduction of tumor growth was observed only after continuous infusion of FUDR via the hepatic artery. Systemic toxicity was lowest in this group for both compounds while the local liver toxicity was only slightly elevated.

The level of DNA interstrand crosslinking in bone marrow parallels the extent of myelosuppression in mice treated with four chloroethylnitrosoureas

This study compares the level of DNA-DNA interstrand crosslinking in murine bone marrow with the decrease in mean number of blood progenitor cells in mice treated with chloroethylnitrosoureas. Male C57BL6 X C3HF1 mice were treated with single IP injections of 1-(2-chloroethyl)-1-nitroso-3-(methylene-carboxamido)-urea (acetamido-CNU), 1,2-bis(2-chloroethyl)-1-nitrosourea (BCNU), 2-[3-(2-chloroethyl)3-nitrosoureido]-beta-D-glucopyranose (chlorozotocin), or 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea (HECNU). After 16 h three aliquots of pooled bone marrow were assayed for DNA damage in the form of DNA-DNA interstrand crosslinks and myelosuppression in terms of the depletion of granulocyte-committed (CFU-C) and pluripotent (CFU-S) stem cell activity. Both acetamido-CNU and HECNU produced a dose-dependent increase in DNA-DNA interstrand crosslinking, which was paralleled by a marked inhibition of both types of progenitor cells. BCNU and chlorozotocin, however, were much less effective at crosslinking DNA, and were much less myelosuppressive in terms of CFU-C and CFU-S activity. These data suggest a correlation between the degree of myelosuppression at the level of the stem cell and the extent of DNA damage in murine bone marrow. The levels of haematosuppression did not parallel the acute single-dose toxicity in mice but rather reflected the relative antileukaemic activity of these agents. However, the degree of recovery of the stem cell compartments may be more relevant to the clinically important long-term toxicity after single and repeated doses.