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Levels of the DNA promutagenic methylation damage, O6-methylguanine (O6-MeG) and the activity of the O6-methylguanine-DNA methyltransferase (MGMT), the enzyme responsible for repairing O6-MeG, were measured at various time intervals in tissues of BDF-I mice administered a single therapeutic dose of the antischistosomal agents hycanthone, oxaminiquine and metrifonate. Hycanthone increased O6-MeG in the liver-DNA after 6 h, then decreased by 3-fold after 48 h. Lower levels of the adduct and a slower rate of formation were found in the intestine and bladder. MGMT activities were significantly lower in the liver (74%) and bladder (25%) compared to control animals after 6 h, then restored by 48 h. Oxaminiquine increased O6-MeG in all tissues, but spleen, after 6 h and persisted only in the bladder after 48 h. Liver and bladder tissues of these animals exhibited a pattern of alteration in the MGMT activity similar to that observed for hycanthone. Metrifonate induced a profile of O6-MeG comparable to that of oxaminiquine but the levels of the adduct were about 2-fold lower. Hepatic MGMT in these animals was significantly lower (approximately 38%) than the control values after 6 h, then restored by 48 h. A significant negative correlation was obtained between O6-MeG and MGMT activity in the liver (r=- 0.85), intestine (r=- 0.62) and bladder (r=- 0.59). These results demonstrate that treatment with antischistosomal agents may lead to the formation of promutagenic alkylation damage in the tissue DNA and alterations in the DNA repair capacity.

Mouse lymphoma cells of the L5178Y TK + /-3.7.2C line were exposed to varying concentrations of the anti-schistosomal drug hycanthone methanesulfonate. The trifluorothymidine (TFT)-resistant cells fell into two classes based on colony size. Southern blot analyses were performed using NcoI-digested DNA from a number of large and small mutant colonies from each treatment group. Two different restriction fragment banding patterns were identified in these analyses, those colonies that contained the 6.4 kb NcoI restriction fragment and those that did not. A total of 471 mutant colonies were analyzed and 84.5% (398) of these colonies did not exhibit the 6.4 kb fragment. There did not appear to be a hycanthone methanesulfonate dose response effect in the number of colonies that did not contain the 6.4 kb fragment among the treated groups. In addition, 82% (154 out of 188) of spontaneous mutants did not contain the 6.4 kb fragment. The results imply that greater than 80% of all spontaneous mutations found in the mouse lymphoma assay regardless of colony size do not contain the 6.4 kb fragment and each may be considered to be a large scale mutation. In addition, greater than 80% of the hycanthone induced mutations in the mouse lymphoma assay do not contain the 6.4 kb fragment and thus may be considered to be a large scale mutation.

A simplified method, using recombinant interleukin-2, foetal bovine serum and freeze-killed feeder cells, has been developed for the mass culture of T-lymphocytes derived from human peripheral blood. In this protocol, bulk cultures can be cryopreserved approximately 8 days after initiation, and subsequent mass cultures generated a further week after recovery. At the end of this period, the lymphocytes have maintained a normal karyotype and cultures from different donors are very similar in terms of rate of cell division and expression of key antigenic markers. Background micronucleus frequencies and dose-responses for micronucleus induction by a reference clastogen, hycanthone, were also very similar in all the cultures examined. Such extended-term T-lymphocyte cultures are potentially valuable in genotoxicity testing, providing cells with the normal human karyotype which can be characterised and handled with the practical convenience of established rodent cell lines.

The clastogenic effect of the antischistosomal drug hycanthone methanesulfonate was studied with the micronucleus test in mouse bone marrow cells. Male and female (102/El x C3H/El)F1 mice were treated with single i.p. injections. Bone marrow was sampled 18, 24 and 30 h after treatment with 100 mg/kg. The highest micronucleus yield occurred at 24 h. The dose response for micronucleus induction at 24 h after treatment was non-linear for doses between 5 and 300 mg/kg. The lowest effective dose was 5 mg/kg for females and 10 mg/kg for males. The experiments revealed a significantly higher sensitivity of female mice for the induction of micronuclei in polychromatic erythrocytes by hycanthone methanesulfonate. This result supports the recommendation to use both sexes for quantitative assessment of genotoxicity in the micronucleus test.

Male and female gametogeneses differ markedly in all mammals. While male germ cells are continuously being produced from stem cells throughout the reproductive life span, the number of female germ cells is fixed during prenatal development and, soon after birth, all of the oocytes are arrested in a modified diplotene, or dictyate, stage. Following puberty, dictyate oocytes are hormonally triggered to mature either singly or in groups, resulting in ovulation and the completion of the first meiotic division. It has been hypothesized that female mice are more susceptible to dominant lethal effects of intercalating agents than male mice because oocyte chromosomes, which are arrested in a diffuse state, are generally more accessable to intercalation than are the more condensed chromosomes present within most male germ cell stages. This hypothesis was further tested using the intercalating agent hycanthone methane-sulfonate. Effects of hycanthone were studied in maturing and primordial oocytes and in male germ cells throughout spermatogenesis. No induction of dominant lethality was observed for treated males while a significant increase in embryonic death, expressed around the time of implantation, was observed in females that mated within 4.5 days after treatment. These effects were the result of dominant lethal mutations induced in maturing oocytes and not of maternal toxicity as indicated by the presence of chromosomal aberrations observed at first-cleavage metaphase of zygotes obtained from treated females. These results add support to the hypothesis that certain intercalating chemicals, which are not mutagenic to male mice, may be mutagenic to females and point to a need for more in-depth studies of female-specific mutagenesis.

Cytophotometric measurement of the effect of praziquantel (500 mg/kg for 2 days) versus hycanthone (60 mg/kg for 3 days) on hepatocyte nuclear deoxyribonucleic acid (DNA) content was evaluated in Schistosoma mansoni infected mice. Drugs were given 8 weeks post-infection and repeated weekly for 4 weeks. DNA values of infected untreated control and infected drug treated groups were related to the median and upper diploid DNA values of normal control. Schistosoma mansoni infection per se did not change the hepatocyte DNA content, yet aneuploidy was 16.7%. Praziquantel did not result in significant change of DNA content or ploidy, while hycanthone resulted in marked significant increase of DNA content (328.9%) and aneuploidy (100%), compared to infected untreated control. Histopathological examination revealed hyperchromatic nuclei with mitosis in the hepatocytes of hycanthone treated mice, but not in praziquantel treated animals. These DNA changes were found to correlate with the reported safety of praziquantel and the carcinogenicity of hycanthone.

Ad-3 mutants induced by hycanthone, lucanthone and their indazole analogs, IA-3, IA-4 and IA-5 were studied to characterize the genetic alterations produced by these agents in Neurospora crassa. The results of genetic analysis indicate that, in marked contrast to past experiments with chemical mutagens on heterokaryon 12, all of these antischistosomal agents induce a very high frequency of multilocus deletions.

4 presumptive clastogens (caffeine, dimethyl sulfoxide, diethylstilbestrol and p,p'-DDE) and 4 chemicals thought to induce chromosomal mutations in L5178Y mouse lymphoma cells (procarbazine X HCl, epichlorohydrin, hycanthone and iodomethane) were tested in the CHO/HGPRT gene mutation assay for the induction of 6-thioguanine-resistant ( 6TGR ) mutants. Of the clastogens, p,p'-DDE was mutagenic at several concentrations and diethylstilbestrol (DES) increased the 6TGR mutant frequency over control levels at the 6.7 and 8.0 micrograms/ml doses, but the results for DES were neither convincing nor significant. Caffeine was not mutagenic although at very high concentrations (6667-8000 micrograms/ml) there was a slight elevation in mutant frequency over background. This was probably due to a selective effect of caffeine against the HGPRT+ phenotype, for 2 different HGPRT- cell lines were refractory to the toxic effects of caffeine at the highest test level (8000 micrograms/ml). All 4 'chromosomal mutagens' produced dose-related increases in mutant frequencies at the HGPRT locus of these CHO cells. 6TGR colonies were generally uniform in size when normal precautions were taken to prevent the formation of satellite (secondary) colonies. Excepting DES, dimethyl sulfoxide, and caffeine, these data demonstrate that 5 of 8 clastogenic chemicals reproducibly induce mutations at the HGPRT locus of CHO cells which lack the small colony-forming potential of 3.7.2C L5178Y cells.

Mutagenesis assays at the thymidine kinase (TK) locus in L5178Y mouse lymphoma cells frequently yield mutant colonies with a bimodal size distribution. The objectives of this study were to determine whether a relationship exists between mutant colony size and chromosomal aberrations and whether the colony-size distributions obtained from this assay can indicate the clastogenic activity of a test chemical. Cells from 8 different types of L5178Y mouse lymphoma cell colonies were examined for chromosomal abnormalities within 10 cell generations after colony isolation. The colonies included small (sigma) and large (lambda) unselected cell (UC) and trifluorothymidine-resistant (TFTr) colonies derived from TK +/- cell cultures treated with the solvent dimethyl sulfoxide (DMSO) or hycanthone methanesulfonate (HYC). Chromosome abnormalities were present in cells from 12% (7/60) of the UC colonies, but there was no apparent relationship between colony diameter and the presence of chromosomal abnormalities. Abnormalities affecting chromosome 11, which is believed to be the site of the TK gene, were not observed in cells from UC colonies. Abnormalities affecting chromosome 11 were observed only in cells from sigma-TFTr colonies irrespective of whether they were spontaneous (5/15 colonies) or induced by HYC (4/15 colonies). Overall, 30% (9/30) of sigma-TFTr colonies had cells with an abnormal chromosome 11 and 10% (3/30) had abnormalities affecting other chromosomes. Abnormalities affecting chromosome 11 were not observed in cells from lambda-TFTr colonies (0/30 colonies). The observation of only 30% of sigma-TFTr colonies with chromosome damage affecting chromosome 11 indicates that other mechanisms, in addition to chromosome damage at the level of resolution used in this study (i.e., 200-300 chromosome bands). contribute to small TFTr colony size.

The antimuscarinic activity of hycanthone and five antischistosomal analogs was determined in three biological assays of cholinergic systems. A linear relationship was established between the LD50 values of hycanthone analogs in mice and 1) the Ki values obtained from the inhibition of [3H]quinuclidinyl benzilate binding to the muscarinic receptors of N4TG1 neuroblastoma cells; 2) the I50 values obtained from the inhibition of alpha-amylase secretion induced by carbachol in pancreatic acini cells; and 3) the KB values obtained from the inhibition of guinea-pig ileum contraction induced by acetylcholine. The linear relationship established between antimuscarinic potency and toxicity in mice suggests that a possible relationship exists between the toxicity of the hycanthone analogs and their antimuscarinic activities. On the other hand, no correlation was established between antischistosomal efficacy and antimuscarinic potency. The Ki and I50 values ranged from 10(-7) to 10(-5) M for the inhibition of the binding of [3H]quinuclidinyl benzilate to the muscarinic receptors and for the inhibition of alpha-amylase secretion. The KB values determined by the guinea-pig ileum assays were approximately 10(-5) to 10(-6) M. The ranking of antimuscarinic potency of the compounds in the three different assays were in good agreement.

Hycanthone, an antischistosomal drug possessing activity against experimental murine tumors, was administered by 20-minute infusion daily x 5 days to 12 patients with advanced cancer to determine dose-limiting toxicity and to look for therapeutic effect. No objective responses were seen. The dose-limiting toxic effect was acute hepatitis occurring in two of four patients treated at 100 mg/m2/day x 5. Moderate nausea and vomiting occurring on treatment days was the only other toxic effect. Hycanthone was not myelosuppressive. Assay of plasma concentrations of hycanthone revealed a plasma half-life of 3-5 hours and no accumulation of drug over the 5 days of treatment.

This report is submitted not to refute the occurrence of any toxicity but to record that in St. Lucia, given reasonable care in administration and careful follow-up, we have not yet encountered jaundice, liver necrosis or other serious side effects.

Hycanthone was administered to Schistosoma mansoni-infected and non-infected Syrian golden hamsters and Swiss mice by intraperitoneal and intramuscular injection of amounts up to the maximum tolerated dose. No tumors attributable to treatment were observed in hamsters. In infected mice, the overall incidence of hepatomas and hepatocellular carcinomas increased from 3.4% in untreated mice to 10.6% in those treated with hycanthone. Non-infected control mice developed 0.8% of these tumors compared to 10.2% in mice treated with hycanthone. Despite the use of high dose levels of hycanthone, statistical significance was attained only with non-infected female mice injected intraperitoneally and intramuscularly with hycanthone and then only at confidence levels of 92 and 95% respectively.

Stable, tandem dicentric chromosomes were discovered in two mutant cell colonies resulting from exposure of L5178Y mouse lymphoma cells to chemical mutagens. These unusual dicentrics were present in all metaphase cells examined from these colonies, even after approximately 65 cell generations in culture. Observation of cells in metaphase and anaphase suggests that the interstitial centromere in these dicentrics is non-functional, and that the terminal centromere is solely responsible for their orderly anaphase segregation.