Putative role of antioxidant enzymes and glyoxalases in carcinogenesis.

The effects various drugs exert on antioxidant enzyme and glyoxalase activity in rat livers were studied. All drugs tested provoked a marked reduction in glutathione peroxidase and a small drop in both glyoxalase I and II activity. It is hypothesized that the substances tested support tumour development by neutralizing organic peroxides, thereby favouring the oxidation of carcinogens and, as a consequence, the formation of metabolites that trigger neoplastic transformation. The reduction in glyoxalase activity is probably attributable to the enhanced cell proliferation induced by the treatment.

Effects of dimethylsulfoxide on Friend erythroleukemic cell proliferation and on the activity of enzymes involved in this process.

Variations in catalase, glutathione peroxidase (GP) and adenylate cyclase (AC) activity in murine erythroleukemic (MEL) cells were studied during multiplication and dimethylsulfoxide (DMSO)-induced differentiation. The results demonstrated that, although DMSO favors the incorporation of 3H-thymidine into DNA of treated cells, it slows down cell multiplication. Increased incorporation was also observed in superoxide dismutase (SOD)-treated cells. DMSO also determined an early and significant drop in AC activity and a late fall in catalase activity, whereas there was no significant variation in GP activity in parallel with the decreased cell multiplication that accompanied cell differentiation. We hypothesize that DMSO and SOD favor 3H-thymidine incorporation by neutralizing the reactive forms of oxygen and that the reduction in catalase and AC activity is closely related to the mitotic activity of MEL cells.

Antioxidant enzymes and proliferative activity of cell lines of different origin.

The effects of catalase treatment were studied in two in vitro passaged ascites tumour lines (ATP C+ and EAT) and in three in vitro established human myeloid leukemia cell lines (HL-60; KG-1; KG-1a) characterized by the arrest of cells at different stages of maturation. The results demonstrate that catalase treatment favoured proliferation in the in vitro passaged ascites tumour cells, but not in the in vitro established leukemia lines. Enzyme assays on five in vitro cell lines revealed that catalase was only present in HL-60. Although glutathione peroxidase activity was initially found in all five cell lines, it disappeared from two ascites tumour cells when they were transferred in culture. It is hypothesized that catalase treatment favours ascites tumour cell proliferation because it replaces glutathione peroxidase in eliminating H2O2.

The role of antioxidant enzymes in benzo(a)pyrene-induced carcinogenesis.

Chick embryo hepatocytes were cultured in the presence of benzo(a)pyrene in order to study the effects of this carcinogen on catalase, glutathione peroxidase and superoxide dismutase activity. The results demonstrate that benzo(a)pyrene is incapable of modifying the activity of these enzymes, even though it is taken up by cultured cells to form benzo(a)pyrene-DNA adducts. The effect of culturing, however, caused a marked reduction in the activity of these enzymes. The significance of these activity variations in benzo(a)pyrene in vitro carcinogenesis is discussed.

Possible role of certain antioxidant enzymes in dimethylnitrosamine-induced liver carcinogenesis.

An investigation was carried out to establish whether the reduction in catalase, glutathione peroxidase and superoxide dismutase activity, normally observed in liver tumours, is an early event and therefore of pathogenetic importance, or whether it is a late occurrence. Experiments performed on dimethylnitrosamine-treated hepatectomized and non-hepatectomized rats show that the decrease in activity of these enzymes is entirely due to hepatectomy, since the tumour-inducing doses of dimethylnitrosamine failed to provoke variations in the activity of these enzymes, in either normal or regenerating liver.

Different response of chicken embryo fibroblasts and hepatocytes to the interference of certain antioxidants on the binding of [G-3H]benzo[a]pyrene to DNA.

The effects of treatment with reduced glutathione, cysteine and ascorbic acid on chick embryo fibroblasts and hepatocytes cultured in vitro in the presence of [G-3H]benzo[a]pyrene ([3H]BP) were studied in an attempt to evaluate the capacity of these antioxidants to interfere with the binding of the carcinogen to DNA in these two cell populations. The results revealed that in the absence of treatment with antioxidants, the carcinogen bound to the DNA of the hepatocytes less than it did to that of the fibroblasts, despite the fact that the two cell populations manifest more or less the same uptake of [G-3H]benzo[a]pyrene from the medium. Moreover the hepatocytes, unlike the fibroblasts, seemed to reap little advantage from the known capacity of the antioxidants to interfere with the binding of the carcinogen to DNA.

Replicative behaviour of ascites tumour cells transplanted in BALB C mice of different sex.

The present research demonstrates that cells from an ascites tumour (ATP C+) multiply more actively in the peritoneum of male mice, provided they are maintained alive in this environment for long periods of time by weekly transplants in animals of the same sex. Solid tumours obtained by inoculating ATP C+ cells, removed from the peritoneum of male mice, into the subcutaneous dorsal region of castrated male mice, grew more rapidly than those obtained by inoculating the same cells removed from the peritoneum of female mice, always provided that the cells had been passaged at length in animals of the same sex. Cytogenetical studies of these two cell subpopulations revealed that cells reproduced for 2 years in males had a less stabile karyotype and a greater incidence of acrocentric associations.

Different behaviour of normal and neoplastic cells cultured in vitro in the presence of catalase and superoxide dismutase.

Chicken embryo fibroblasts and hepatocytes were studied in the presence of catalase and superoxide dismutase in order to establish whether these enzymes had the capacity to favour cell multiplication as previously shown for in vitro tumour ascites cells (ATP C+). The results indicate that, unlike ATP C+ cells, both fibroblasts and hepatocytes are inhibited in their multiplication by superoxide dismutase. Similar effects are exerted on hepatocytes by catalase, whereas the multiplication of fibroblasts is favoured by high doses of this enzyme. Enzyme determinations revealed high levels of catalase and superoxide dismutase in hepatocytes, whereas both enzymes were poor in fibroblasts and ATP C+.

Antagonism between catalase and ascorbic acid in control of normal and neoplastic cell multiplication.

The authors studied the effects of a treatment with ascorbic acid on in vitro multiplication of ascites tumour cells (ATP C+), of fibroblast-like cells and of hepatocytes from chick embryos, by measuring [3H]thymidine incorporation into DNA. The results obtained show that the ATP C+ cells are the most sensitive to the toxic effects of the experimental treatment, while the hepatocytes are the most resistant cell population. A treatment with catalase was able to greatly reduce the damage caused by ascorbic acid on the ATP C+ cells. It is hypothesized that ascorbic acid inhibits cell multiplication by the H2O2 formed by its oxidation and that the cells having the highest level of catalase are more resistant to its toxic effects.

Cell multiplication of an ascites tumour in the presence of superoxide dismutase and catalase.

Superoxide dismutase and catalase were demonstrated to favour the multiplication of ascites tumour cells in vitro. It is proposed that these enzymes neutralize the O2-. and H2O2 that may accumulate in the neoplastic cell and that cell damage occurs because the cellular levels of both enzymes are low.

Onset and growth rate of solid tumours derived from implanted ascites tumour cells pretreated with ascorbic acid.

A study on the onset and growth kinetics of solid tumours obtained by injecting ATP C+ cells preincubated with ascorbic acid, iodoacetate or citric acid into BALB Cf/Had/Se substrain mice showed that ascorbic acid was not as effective as iodoacetate in inhibiting the growth of these tumours, since higher doses of ascorbic acid were required to obtain a similar effect. This suggests that ascorbic acid, unlike iodoacetate, does not act by blocking the SH groups. Furthermore, not only did incubation of ATP C+ cells with lower doses of ascorbic acid fail to inhibit tumour growth, but rather favoured the growth of solid tumours derived from these cells. Other experiments designed to evaluate the degree of immunity provided by ascorbic acid, iodoacetate and citric acid pretreated cells in mice indicated that such treatment was of limited efficiency, since it considerably reduced the antigenicity of the cells.

Inhibition of the binding of 7,12-dimethylbenz[a]anthracene to DNA by ascorbic acid, reduced glutathione and cysteine in chick embryo cells cultured in vitro.

A study on the capacity of ascorbic acid, reduced glutathione and cysteine to interfere with 3H-7,12-dimethylbenz[a]anthracene (3H-DMBA) binding to DNA in cultured fibroblast-like cells from 11-day-old chick embryos showed that, although the total amount of 3H-DMBA in the treated cells was greater than in the untreated cells, the DNA-bound 3H-DMBA was less. Comparisons between the various experimental groups demonstrated that the greater 3H-DMBA in the ascorbic acid-, reduced glutathione-, and cysteine-treated groups could not be attributed to an initially higher number of cells, nor to a treatment-induced increase in DNA synthesis. It is proposed that the three substances examined inhibit the oxidative degradation of 3H-DMBA, thereby favoring its accumulation within the cell and reducing the formation of DNA-binding metabolites.

Congenital ocular and other systemic abnormalities associated with ring-11 chromosome.

The ocular and systemic abnormalities in a boy with ring chromosome 11 [46, XY/46, XY, r(11) (p 15.5----q25] are described. The ocular anomalies consisted of bilateral hypermetropia, microcornea, anterior chamber cleavage syndrome with prominent Wölfflin nodes, and cartwheel configuration of the anterior iris leaf. The systemic changes consisted of skeletal, muscular and articular defects, obesity, cryptorchidism, and mild mental retardation.

Influence of sexual hormones on solid tumor growth and ATP C+ cell replication.

Solid tumors obtained by implanting ATP C+ cells subcutaneously into the back of BALB/cf/Had/Se substrain mice developed more rapidly in males than females. Experiments conducted on gonadectomized animals demonstrated that female gonads inhibit the development of this tumor. Studies on ATP C+ cells cultured in vitro with various doses of male and female hormones showed that mainly progesterone, but to a lesser extent also estradiol, significantly inhibit cell proliferation with respect to testosterone. The treatment of normal and gonadectomized animals with testosterone and progesterone confirms the results obtained in vitro. Analyses carried out on ATP C+ cells do not reveal presence of estradiol and progesterone receptors.

Effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system.

The authors studied the effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system, in order to establish if these substances influence cell proliferation by interfering with glyoxalase activity. The results demonstrate that both ascorbic and dehydroascorbic acid do not alter glyoxalase activity in vitro, even if employed at high doses.

Effects of ascorbic and dehydroascorbic acid on the multiplication of tumor ascites cells in vitro.

The effects of AA and DHA on ATP C+ cell multiplication in vitro were studied by measuring incorporation of 3H thymidine into DNA. The results obtained demonstrate that both AA and DHA have the same effects: they favor cell multiplication at low doses and inhibit it at high doses. Experiments carried out with serial doses of both these substances revealed that AA is more efficient in determining both stimulating and inhibiting effects. The lesser efficiency of DHA may be attributed to its limited stability in culture medium. Studies on the effect of high doses of AA and DHA added to the culture medium in single or fractionated doses revealed that fractionated administration is more efficient in inhibiting cell multiplication than single administration.

Absence of accumulation phenomena in normal and tumoral tissues of mice treated with ascorbic acid.

The authors studied the effects of an energetic and prolonged ascorbic acid (AA) treatment on AA concentration in a solid tumor obtained by transplanting ascites tumor cells in the dorsal subcutaneous region of Balb/C1/Had/Se substrain mice. The results demonstrate that this tumor, whose growth is favored by AA, not only is incapable of accumulating AA, but surprisingly presents a lowering of its concentration as the result of treatment with very high doses of AA. The levels of AA in various organs and tissues of mice bearing the aforesaid tumor show no significant difference to those observed in organs and tissues of healthy mice. An energetic and prolonged treatment with AA not only is incapable of favoring accumulation, but also causes a lowering of its concentration in the liver and kidney, similar to that observed in tumors. Therefore, the hypothesis may be advanced that this decrease is caused by the adaptation of some enzymatic system, which results in a greater utilization of AA. This greater consumption could be the cause of the decreased AA levels once esogenous administration is arrested.

Stimulating effect of ascorbic acid on ascites tumor cell multiplication in vitro.

In a preceding report evidence has been presented that ascorbic acid (AA) accelerated solid tumor growth obtained by inoculating tumor ascites cells into the subcutaneous dorsal region of inbred Balb/cf/Had/Se substrain mice. The present work investigates whether this effect is the result of a direct action of AA on neoplastic cell multiplication or of an indirect action on the tumor cells mediated by changes induced by AA in the organism bearing the tumor. The results obtained demonstrate that AA at low doses (microgram 10-30/ml) stimulates ascites tumor cell multiplication in vitro, while at high doses (microgram 60-120/ml) the opposite occurs. These results suggest that the major growth of solid tumors observed in mice treated with AA may be attribute to the capacity of this substance to favor the multiplication of ATP cells which were used to induce the tumors.