Deferasirox shows in vitro and in vivo antileukemic effects on murine leukemic cell lines regardless of iron status.

Numerous studies have shown the antiproliferative effect of iron chelating agents (ICAs), which have been used traditionally in patients with secondary iron overload (SIO). Because the in vivo model for these studies has been animals with normal iron status, the antileukemic effect of ICAs in the SIO condition has not been determined clearly. We investigated the in vitro and in vivo effects of ICAs in murine leukemic cell lines regarding the iron status. The viability of both EL4 cells and L1210 cells incubated with either deferoxamine (DFO) or deferasirox (DFX) decreased in a concentration-dependent manner. This effect was most prominent in L1210 cells treated with DFX. The viability of L1210 cells incubated with both ICAs did not change regardless of the presence of ferric chloride. The percentage of apoptosis in L1210 cells treated with DFO or DFX increased in a concentration-dependent manner; however, the expression of Fas showed no significant change. The non-SIO mice and SIO mice bearing L1210 cells showed longer survival than other groups when treated with DFX, whereas the SIO mice treated with DFO showed shorter survival than the control group. The tumor was significantly smaller in the SIO mice treated with DFX or DFO compared with the control group. The iron content of the liver or the tumor in SIO mice decreased after ICA treatment. This study indicates an antileukemic effect of DFX regardless of iron status and suggests that the use of DFX has a survival benefit for SIO leukemia murine model in terms of iron chelation and antileukemic therapy.

Influence of leukaemia on acetaminophen-induced hepatotoxicity in mice.

Since it is known that the metabolism of acetaminophen is involved in its hepatotoxicity and that drug metabolizing enzyme activity is decreased in tumor bearing animals, it was of interest to study the influence of L-1210 leukaemia on acetaminophen hepatotoxicity in BDF-1 male mice. A single oral dose of acetaminophen, 125 mg/kg, was given at the fifth day of the mice survival period (7.7 days) and the animals killed twenty-four hours later. As revealed by serum glutamic-pyruvic transaminase, serum glutamic-oxaloacetic transaminase and lactic dehydrogenase, acetaminophen was less hepatotoxic in leukaemic mice than in control mice by comparison with their own saline group; on the other hand the difference between control and leukaemic mice treated with acetaminophen was significant only for glutamic-pyruvic transaminase. Moreover, we found higher unchanged acetaminophen concentrations in plasma, liver, kidneys, brain and fat of the leukaemic mice as compared to controls, less conjugated metabolites in plasma and liver, decreased in vitro aniline hydroxylation and ethylmorphine N-demethylation. Finally, following acetaminophen administration, reduced hepatic glutathione was depleted to a much lesser extent in the tumor bearing animals than in controls. In conclusion, the L-1210 leukaemia seems to modify the acetaminophen hepatotoxicity and this effect might be explained by decreased acetaminophen biotransformation into toxic metabolites or intermediates.

Resistance to L1210 mouse leukemia cells in moderately protein-malnourished BALB/c mice treated in vivo with thymosin fraction V.

Moderate protein malnutrition retarded the i.p. proliferation of L1210 mouse leukemia cells in BALB/c mice. The increased resistance against leukemia cell growth in protein-malnourished mice was correlated with increased in vitro mitogenic responsiveness of spleen lymphocytes to phytohemagglutinin and increased levels of serum corticosterone but could not be correlated with altered development of splenic lymphocyte-mediated cytotoxicity. The increased resistance against leukemia cells in well-fed mice treated with thymosin alone could not be correlated with an increase in any of these parameters. Treatment with Thymosin Fraction V further increased the resistance of protein-malnourished mice to i.p. leukemia cell growth. The increased resistance of these mice to tumor cell growth was correlated with increased splenic lymphocyte mitogenic responsiveness to phytohemagglutinin, elevated serum corticosterone levels, and a slight increase in lymphocyte-mediated cytotoxicity 14 days after tumor challenge. For 7 days after the last treatment, protein-malnourished mice had reduced serum corticosterone levels. Nevertheless, the serum corticosterone levels were still higher than normal in these mice.

Leukemoid reaction induced by different transplantable tumors in three inbred mouse strains.

We have studied the induction of a granulocyte-associated leukocytosis (leukemoid reaction) in C3HA, C57B1/6, and DBA/2 mice by a number of transplantable tumors of different origin. Leukemia L1210, Hepatoma 22, a transplantable mammary carcinoma of spontaneous C3HA origin, and a L929 culture fibroblasts-derived rhabdomyosarcoma, all induced a leukemoid reaction in their specific mouse strain. Melanoma B16 and Lewis lung carcinoma gave no reaction; Adenocarcinoma 755 and Harding-Passey melanoma evoked a leukocytosis but not due to an increase in neutrophils. Some extratumoral factors can influence the hematological response; the intensity of final leukemoid reaction was higher in female mice than in males bearing the same tumor. On the other hand, Ehrlich ascites tumor transplanted in all three inbred mouse strains rendered different levels of leukemoid reaction; response was higher in DBA/2, intermediate in C3HA and lower in C57B1/6.

Shortened platelet survival as a cause of thrombocytopenia in mice with L1210 leukemia.

Thrombocytopenia is a frequent complication of acute leukemias of humans and animals. To define the possible causes of this decrease in platelets, we have studied platelet kinetics in mice after transplantation of 10(6) ascites cells from mice bearing L1210 leukemia. The circulating half-time of 51Cr-labeled platelets was reduced to approximately one-half that of controls when studied 1 or 3 days posttransplantation. Recovery of transfused 51Cr-labeled platelets was reduced to approximately one-half that in controls when studied 3 days after introduction of L1210 cells. Megakaryocyte concentration showed no change during the 5-day survival after i.v. infusion of leukemic cells but was increased on Day 5 and i.p. inoculation with an average host survival of 7 days. Megakaryocyte diameter distributions were significantly shifted toward larger sizes beginning on Day 2 after i.v. inoculation and on Day 3 after i.p. inoculation. Twenty-four-hr [3H]thymidine labeling indices of megakaryocytes were significantly increased beginning on Day 3 after i.v. inoculation but were significantly decreased on Days 5 and 6 after i.p. introduction of L1210 cells. We conclude that the decrease in platelets in mice transplanted with L1210 leukemia results primarily from shortened platelet survival and organ pooling. Megakaryocytes remain normal in concentration but increase in size, a usual response to decreases in platelet count.

Effect of L1210 leukemia on the susceptibility of mice to Candida albicans infections.

This study was carried out to determine whether animals bearing L1210 leukemia were more susceptible to candida infection in the absence of immunosuppression and to determine also if the L1210 cells suppressed the inflammatory response of the animal host. Systemic infection was studied by intravenous injection of Candida albicans and checking for the number of candida organisms cultured from the blood and the kidneys. Localized infection was studied by intramuscular injection of C. albicans into the thighs and measuring the changes in the thigh size. Compared with tumor-free controls, the intravenous injection resulted in higher counts of C. albicans from the blood and the kidneys of tumor-bearing animals. No significant difference in the localized swelling was noted between tumor- and nontumor-bearing mice with respect to intramuscular injection of C. albicans. The results thus indicate that L1210 leukemia increases susceptibility of tumor-bearing animals to systemic candida infection. L1210 cells were shown to reduce the accumulation of neutrophils and to suppress the inflammatory reaction elicited by C. albicans.

Pepstatin, an ascites retardant of L1210 tumor-bearing mice.

The effect of pepstatin on the kinetics of ascitic fluid accumulation in L1210 tumor-bearing mice (DBA/2) was observed. Following inoculation of 1.5x10(6) tumor cells, untreated mice reached a peak of fluid accumulation on day 6 and remained at this level until death on day 9. A "lag" phase of 4 days occurred before fluid accumulation was seen. Pepstatin administered SC in a single dose of 80 mg/kg during the lag phase, significantly retarded fluid accumulation as compared to untreated animals. Pepstatin administered following fluid accumulation was much less effective. We concluded that pepstatin prevents fluid accumulation rather than acts as a diuretic agent. The term "ascites retardant" is suggested for the pharmacologic actions of pepstatin, since it prevents fluid accumulation without diminishing the cell count.

Antiinflammatory reaction associated with murine L1210 leukemia.

Mice bearing L1210 leukemia did not show impaired humoral or cellular immune response to antigenic stimulation druing the early stage of the tumor, and a depressed response was noted only in the terminal stage. L1210 cells were shown to suppress inflammatory reaction in vivo.

Pepstatin, an inhibitor of leukokinin formation and ascitic fluid accumulation.

Ascites fluid accumulation accompanying a mastocytoma or L1210 murine tumor is significantly retarded following the i.p. or s.c. injection of moderate quantities of pepstatin, a known acid protease inhibitor. No effect on cell count was noted by pepstatin treatment. The probable mechanism by which pepstatin acts is by inhigiting the enzymatic formation of chemical mediators known as leukokinins. These are pharmoacologically active peptiedes having potent permeability characteristics previously described by this laboratory. Leukokinins are formed by cathepsin D-like enzymes present in the invading cells and in the ascites fluid acting on a protein substrate, leukokininogen. present in the ascites fluid. Pestatin inhibits the action of these leukokinin-forming enzymes invitro but has no effect on kallikreins (bradykinin-forming enzymes) in vitro. Human ascites fluid from a patient with ovarian carcioma was found to have a paepstatin-inhibited, leukokinin-generating system, as does the mouse. A 'chemical mediator' theory is proposed for ascites fromation which broadens the previously held theory of lymphatic blockage (Holm-Nielsen) and may explain the recent findings of Hirabayashi and Graham of increased plasma-ascites exchange in peritoneal carcionmatosis. Pepstatin inhibition of chemical mediator formation may represent a new therapeutic approach to ascites fluid accumulation in neoplastic disease.

Behavioral parameters in rats and mice bearing tumors, carcinogens and inflammatory agents in the brain.

Walker tumor cells and carcinogens were implanted into the brains of rats and L1210, P388 and Ehrlich ascites tumors, in addition to inflammatory agents and hydrocarbons, injected cortically into mice. Behavioral changes were followed in such animals by several psychological criteria, a discriminated lever-press task in rats and an exploratory task, the poke test, in rats and mice. An activity wheel was also employed for further amplification of mouse behavior. No definite changes could be discerned by these tests between rats bearing tumor or carcinogen and the respective controls as was also the case with levels of activity in the mouse. In marked contrast, mice administered tumors or kaolin cortically demonstrated significant reductions in the mean number of pokes, especially with the higher numbers of cells injected and where neurological symptoms were evident. Behavioral changes, if any, were minimal in mice with cortically implanted carcinogens.