Lack of Carcinogenic Sensitivity of the Glandular Stomach in Heterozygous p53 Knockout Mice Given N-Methyl-N-Nitrosourea in their Drinking Water for 26 Weeks

Gastric tumorigenic sensitivity to N-methyl-N-nitrosourea (MNU) was examined in heterozygous p53 knockout ‍(p53(+/-)) CBA mice and their wild-type littermates (p53(+/+)). In Experiment 1, 37 male p53(+/-) or 38 male p53(+/ ‍+) CBA mice were given MNU in their drinking water at concentration of 50ppm (Group 1 or 4), 10ppm (group 2 or ‍5) or 0ppm (group3 or 6) for 26 weeks. In Experiment 2, p53(+/-) and p53(+/+) CBA mice of both sexes received ‍water containing 50ppm MNU for 26 weeks. In Experiment 1, the incidences of hyperplasias in the glandular ‍stomach observed in p53 (+/-) CBA mice treated with 50ppm and 10ppm MNU were significantly increased, as ‍compared with the control group. No tumors were induced in the stomach of any treated groups. Some proliferative ‍or non-neoplastic lesions were observed in some p53 (+/-) CBA mice, but there was no significant difference in their ‍incidences between treated and control groups. In Experiment 2, the incidences of hyperplasias in the glandular ‍stomach observed in p53 (+/-) CBA mice of both sexes treated with 50ppm MNU were not significantly increased, as ‍compared with the treated p53(+/+) CBA group. One papilloma of the forestomach was observed only in a male ‍p53(+/-) CBA mouse treated with 50ppm MNU. The present study suggests that p53 (+/-) CBA mice have low ‍susceptibility to MNU-induced gastic carcinogenesis.     

Generation of an antitumour immune response to a murine mesothelioma cell line by the transfection of allogeneic mhc genes

We have determined whether transfection and expression of allogeneic MHC genes in a murine mesothelioma cell line can generate an anti-tumour immune response. The MHC genes encoding H-2K^b and H-2D^d were transfected into the mesothelioma cell line AC29 (derived from CBA mice, H-2^k) and transfectant clones isolated. Each of five H-2K^b and 4 H-2D^d transfectant clones were unable to form tumours in CBA mice, although they had maintained their ability to form tumours in F₁ crosses of CBA ± C57b1/10 or CBA ± BALB/c, respectively. Thus the tumours expressing the transfected MHC genes were rejected only in an allogeneic setting. Mice without tumours after transfectant challenge were inoculated on the opposite flank with 1 ± 10⁶ parental AC29. There was no evidence of systemic immunity to the parental cell line since tumours formed at the same rate as in naive mice. The mixing of allogeneic MHC transfectants with parental AC29 did, however, retard the growth of parental tumour. Our study illustrates that the expression of allogeneic MHC molecules on a highly immunosuppressive and non-immunogenic murine malignant mesothelioma cell line was able to stimulate rejection of tumour cells but was incapable of generating a systemic protective response against the parental cell line.     

Role of bacterial microflora in development of intestinal lesions from graft-versus-host reaction.

Acute secondary disease was induced in (C57BL X CBA)F1 mice by transplanting CBA bone marrow and spleen cells following lethal whole-body irradiation. The lesions of graft-versus-host (GvH) disease were scored quantitatively by counting of degenerated crypts in subcutaneous fetal gut implants that were free of bacteria. In conventional F1 mice the damage in F1 fetal gut was twice as great as in F1 fetal gut implants carried by decontaminated chimeras. CBA fetal gut implants developed substantial damage when present in conventional chimeras, but not when present in decontaminated chimeras. These results could be explained by assuming the presence of cross-reacting antigens on intestinal bacteria and in the gut epithelial tissue. They also explained the profound protection against delayed GvH mortality provided by removal of the intestinal microflora.     

Development of a xenograft glioma model in mouse brain

Xenograft intracerebral glioma models have been developed in normal mice by growing the rat C6 glioma in either adult or neonatal mouse brains. Using this tumor line it was possible to grow discrete intracerebral gliomas in either CBA or AKR adult mice or neonatal mice. The size of the tumor mass and length of survival was directly related to the number of tumor cells injected and the time after implantation. To obtain localized intracranial tumor growth cells were suspended in a 1% agarose solution before implantation. Following injection of 10(6) cells into the frontal lobe of adult CBA or AKR mice, discrete tumor masses greater than 4 mm in diameter were obtained in 90% of animals at 14 days, and the largest tumors in adult mice occurred between 21 and 28 days after implantation. The tumor size following implantation of 10(6) cells was significantly greater than with 10(5) cells at 7 days (P less than 0.05) and at 14 and 21 days (P less than 0.01). Less than 60% of mice of BALB/c, RIII, or C57 black strains developed tumors greater than 4 mm diameter at 14 days after intracerebral injection of 10(6) C6 cells. Using neonatal mice it was found that when 10(5) cells were injected intracranially tumors greater than 4 mm in diameter developed in 14 of 15 animals within 2 weeks (CBA mice). Similar results were seen in the RIII, AKR, C57 black, and BALB/c strains. Longer growth periods resulted in larger tumors, up to 8 mm in diameter (6 of 10 animals at 20 days). The tumors in the neonatal animals were not as discrete as in the adult mice, and tumor often spread to the meninges and into the lateral ventricles. The tumor harvested from the brain had a cloning efficiency of 1.2 +/- 0.4% (SD). A panel of monoclonal antibodies was raised to the C6 glioma, and this was used to define clearly the margins of the tumor within the brain. The xenograft mouse models should prove useful for the study of the therapy of gliomas.     

Effect of ethidium bromide on transplanted virus-induced tumor cells.

Ethidium bromide (2,3-diamino-5-ethyl-6-phenylphenanthridinium bromide) significantly inhibited the RNA-dependent DNA polymerase of types A and C particles isolated from transplanted adenovirus 12-induced tumors of CBA mice. It was also cytotoxic for an established in vitro line of adenovirus 12-induced tumor cells of CBA mice and caused cell death, inhibition of [3H]thymidine uptake, and a significant reduction of cells in metaphase. Ethidium bromide significantly inhibited the in vivo growth of transplanted adenovirus 12-induced tumor cells of CBA mice, simian virus 40-induced tumor cells of hamsters, and murine leukemia virus-induced lymphoma cells of BALB/c mice. The compound may have exerted the antitumor activity by selectively affecting oncornavirus in the tumor cells.     

Pararenal angiosarcoma induced in male mice by 1,2-dimethylhydrazine - a model for studying the role of androgens in chemical carcinogenesis

CBA male mice treated with 1,2-dimethylhydrazine (DMH) developedhigh incidence (up to 97%) of pararenal angiosar-comas. Castrationthat preceeded DMH-treatment almost completely inhibited theinduction of these tumours while castration that followed DMH-treatmenthad on influence on their development. Testosterone propionate(TP) was efficient in restoring the incidence of DMH-inducedpararenal tumours in castrated males only when given simultaneouslywith DMH and was totally inefficient when given after the cessationof DMH-administration. Castrated CBA female mice developed 92%of pararenal angiosarcomas when they received combined treatmentwith DMH and TP; no such tumours appeared in the intact femalestreated with DMH alone. The incidence of pararenal tumours inmales of different strains was as follows: CBA, 97%; (CBA xC57BI)F₁ 36%; C57Bl, 4%; C3H, 35%; BALB/c, 13%; C3HA, 7%.     

Effects of rufloxacin in Salmonella typhimurium infection in mice.

This study was undertaken to investigate the efficacy of rufloxacin, a new quinolone which is interesting due to its pharmacokinetics characterized by a long plasma half-life, in the treatment of systemic salmonella infections in the mouse typhoid model. Innately susceptible BALB/c and resistant CBA mice were used to investigate the efficacy of rufloxacin in controlling systemic salmonella infections when given for brief or prolonged periods. The present study shows that rufloxacin is not only very effective on both mouse strains, but can completely eradicate the salmonellae from livers and spleens when given early in the infection of CBA resistant mice.     

Resistance to erythroleukemia in immunodeficient xid- CBA/N mice with susceptibility after immune stimulation

CBA/N (xid-) mice failed to develop erythroleukemia when inoculated with an NB-tropic, anemia-causing Friend virus stock (FVA), while Fv-2ss mouse strains succumbed rapidly to the characteristic Friend disease, even after a virus dose 30-fold lower than that given to CBA/N mice. Immunization with bacterial antigens or with spleen cell allografts prior to FVA inoculation rendered CBA/N mice highly susceptible to FVA. Transplantation studies confirmed that non-immunized CBA/N mice were able to both support erythroleukemic cells and permit erythroleukemic transformation, thus arguing against host defense mechanisms as a cause of resistance. On the basis of early erythroid progenitor cell sensitivity to hydroxyurea in vivo, the CBA/N strain appeared to have the FVA sensitive genotype (Fv-2ss). These results imply that CBA/N mice are not intrinsically resistant to FVA and that an as yet unknown type of immunological activity, evoked both by various immunizations and allogeneic transplantation, is required for Friend leukemogenesis in this immunodeficient inbred strain. These findings further suggest that the erythroid target cells transformed by Friend viruses are influenced by immunological activity.     

Modifications of an immunodominant peptide antigen induce different anti-polyoma tumor responses in two separate mouse strains.

An immunodominant polyoma peptide antigen MT162-176 was modified with regard to amino acid (aa) composition in an attempt to analyze its immunogenicity in detail. Twelve modifications of peptide MT162-176, 3 overlapping peptides and 9 peptides with point mutations, were synthesized and used for immunizations of (A.CA x C57BL/6)F1 and CBA mice against the syngeneic polyoma tumors SECA and SEBA. All 3 overlapping peptides MT162-176, MT165-174 and MT170-176, were immunogenic in (A.CA x C57BL/6)F1 mice against SECA, indicating that possibly more than one immunogenic epitope may be recognized within the MT162-176 sequence. In CBA mice, the 2 peptides covering the C-terminal half were immunogenic against SEBA, while the N-terminal peptide was possibly somewhat less efficient. The peptides with aa point mutations induced different anti-tumor responses in the 2 mouse strains. In CBA mice, only one mutant, MT162-176.28, was immunogenic. For (A.CA x C57BI)F1 3 different mutants, MT162-176.29, MT162-176.35 and MT162-176.36 were immunogenic against SECA, while the remaining 6 had lost their activity. These results suggest that a different emphasis of recognition of peptide MT162-176 exists with regard to the 2 mouse strains examined. Furthermore, different immunization procedures were tested. We found that repeated immunizations with peptide without Freund's adjuvant was the most efficient.     

Effects of Rufloxacin in Salmonella typhimurium Infection in Mice

Summary

This study was undertaken to investigate the efficacy of rufloxacin, a new quinolone which is interesting due to its pharmacokinetics characterized by a long plasma half-life, in the treatment of systemic salmonella infections in the mouse typhoid model. Innately susceptible BALB/c and resistant CBA mice were used to investigate the efficacy of rufloxacin in controlling systemic salmonella infections when given for brief or prolonged periods. The present study shows that rufloxacin is not only very effective on both mouse strains, but can completely eradicate the salmonellae from livers and spleens when given early in the infection of CBA resistant mice.     

Foreign-body tumors of mice: strain and sex differences in latency and incidence.

Sarcomas were induced by sc implantation of unplasticized polyvinylchloride acetate films in female and male mice of strains AKR/J, BALB/cJ, BALB/cWat, CBA/H and CBA/H-T6, C3H/HeJ, C57BL/10ScSn, C57BL/6J-bgj, C57BL/cdJ, DBA/-1J l/LnJ, LP/J, SJL/J, X/Gf, 129/J, and hybrids (CBA/H-T6 X AKR/J)F1, (C57BL/10ScSn x CBA/H or CBA/H-T6)F1, (C57BL/6J-bgj x C57BL/6J)F1. The strains and sexes showed marked differences in incidence and mean latency of resulting tumors. Crucial information was provided for the selection of appropriate mouse strains for the study of interrelationships between genotypes, defined somatic properties, and the multifactorial process of foreign-body tumorigenesis.     

Natural antibody in mammary tumor virus-infected mice that reacts with intracytoplasmic A particles of mouse mammary tumors.

By an indirect immunofluorescence technique with prolonged serum incubation on murine mammary tumor (MT) slices, 179 of 424 mice examined were found to possess natural serum antibody (antibodies) that reacted with intracytoplasmic A particles (iAp) of MT cells. The immunologic specificity of this antibody was supported by absorption and blocking experiments. Furthermore, a strong similarity was seen between the mouse antibody reaction on various MT and the fluorescence pattern of rabbit anti-iAp antiserum on these tumors. In female mice, incidence and geometric mean titers of the antibody in part were correlated to the spontaneous MT frequency of the mouse strains examined. Some mice of the strains XVII/Bin and CBA/BinfXVII/Bin, hitherto regarded as "free" of the mouse mammary tumor virus (MuMTV), also contained anti-iAp antibody in their sera. In contrast to MuMTV)-producing CBA/Bin micethese animals did not possess detectable spontaneous antibody reacting with MuMTV-B particles. Therefore, hypothetically, the antibody response in these mice might be induced by incomplete MuMTV expression. In the strain CBA/Bin, females 4 months old and older possessed the antibody in significantly higher geometric mean titers when compared to 4-week-old female mice. The history of lactation seemed to have no influence on the titer of antibody. In the comparatively high MT strains CBA/Bin and C3H/Bin, adult (4-month-old) females had the antibody in significantly higher levels when compared to age-matched males.     

Effect of chloramphenicol on the toxic and therapeutic effect of N-nitrosomethylurea

The influence of chloramphenical (CAP) on toxic and therapeutic effect of N-nitrosomethyl urea (MNU) in mice of CBA line was studied. It is shown that in injection of lethal doses of MNU--0.08--0.1 mg/g in intact animals CAP reduced LD100 to LD50 and LD50 to LD0. Also CAP increased an average survival of animals with ascites Ehrlich tumor when injected the lethal dose of MNU--0.1 mg/g. Therapeutic effect of MNU in a dose of 0.05--0.075 mg/g in the presence of CAP was not changed and sometimes was even increased. Under discussion is the significance of the obtained results for chemotherapy of malignant tumors in man.     

Occurrence of tumours in the descendants of CBA male mice prenatally treated with diethylstilbestrol

There is well documented evidence both in humans and in experimental animals that exposure to diethylstilbestrol (DES) during pregnancy results in an increased incidence of tumours in the progeny. The increased cancer risk has been reported to persist in the second generation descendants of DES-exposed pregnant mice. In the present experiment, female mice of the CBA strain were treated at day 17 of pregnancy with I μg/g body weight of DES. The descendants of DES-treated mothers, described as F₁DES, were mated among each other or with untreated animals. The F₁DES females were found to be sterile when mated with either F₁DES or untreated males. F₁DES males were successfully mated with untreated females. In the female offspring so obtained, but not in the male, a statistically significant increased incidence of tumours was observed, in particular of uterine sarcomas, and also of benign ovarian tumours and of lymphomas.     

The innate resistance of CBA mice to endogenous murine leukaemia virus infection.

The incidence of lymphomata in CBA mice is low and furthermore is unaltered by transplantation at the early blastocyst stage and being born from the lymphoma-prone AKR. The number of C-type murine leukaemia virus particles in CBA derived in this manner and milk-fostered by AKR mice in no way differs from normal CBA. The results suggest that the oncogenic Gross virus does not pass through either the transplacental or transmammary routes, or alternatively that viral replication in the CBA was in some way inhibited. Both possibilities have still to be distinguished.     

Flavone acetic acid induces a coagulopathy in mice

The effects of flavone acetic acid (FAA) on the coagulation properties of plasma from tumour-bearing and non-tumour-bearing mice have been investigated. The study was carried out primarily on CBA mice and the CaNT tumour, although substantiating data are included for two other tumours grown in the WH strain. FAA was injected at a range of single doses up to a maximum of 300 mg kg-1, and clotting properties of the plasma were measured in vitro at various times after FAA administration. Platelet numbers and the concentration of fibrin degradation products (FDP) in the plasma were also determined. Following a dose of 300 mg kg-1, the clotting times were significantly reduced at 15-30 min in both tumour-bearing and non-tumour-bearing mice of both strains. Detailed studies on coagulation in the CBA strain (+/- CaNT tumour) indicate that in tumour-bearing animals the initial decrease in clotting time is followed 4-6 h later by an increase in clotting time, thrombin time and FDP levels. Platelet counts of tumour-bearing mice also decreased significantly over this period. Similar experiments in non-tumour-bearing mice did not show these late effects. All the data from the coagulation tests on mice with CaNT tumours are consistent with the hypothesis that intravascular coagulation occurs following treatment with FAA, and that vascular occlusion in tumours, as a results of FAA-induced coagulopathy, may contribute to tumour regression.     

Modulation of medullary thyroid carcinoma penetrance suggests the presence of modifier genes in a RET transgenic mouse model

We described previously a thyroid phenotype for transgenic mice expressing an activated Ret oncogene driven from a human calcitonin promoter. Medullary thyroid carcinomas (MTC), a tumor of the thyroid parafollicular C cells, occur in this transgenic line with a pathology analogous to that seen in patients with multiple endocrine neoplasia type 2 (MEN2). When the transgene was introgressed onto four different genetic backgrounds, between 0 and 98% of transgenic progeny developed thyroid tumors by 10 months of age, indicating that tumor penetrance could be modulated by genetic background. Furthermore, tumors on the CBA/ca and C57BL/6J backgrounds were significantly larger than those arising in BALB/c transgenic mice. These results are relevant to human MEN2 disease, because this model system may be used to study genes modifying thyroid tumor penetrance in the dominantly inherited human cancer syndrome.     

Effect of exposure to light-at-night on life span and spontaneous carcinogenesis in female CBA mice

The effect of constant illumination on the development of spontaneous tumors in female CBA mice was investigated. Fifty female CBA mice starting from the age of 2 months were kept under standard light/dark regimen (12 hr light:12 hr dark; LD) and 50 CBA mice of similar age were kept under constant illumination (24 hr a day, 2,500 Lux, LL). Exposure to the LL regimen decreased food consumption but did not influence body weight, significantly accelerated age-related disturbances in estrous function, and was followed by a significant increase in spontaneous tumor incidence in female CBA mice. Tumor incidence as well as the number of total or malignant tumors was significantly increased in the LL group compared to the LD group (p < 0.001). The incidence of lung adenocarcinomas, leukemias and hepatocarcinomas was 7/50; 6/50 and 4/50 in the LL group and 1/50; 0/50 and 0/50 in the LD group. Mice from the LL groups had shorter life spans then those from the LD group. The data demonstrate, for the first time, that exposure to constant illumination was followed by increases in the incidence of spontaneous lung carcinoma, leukemias and hepatocarcinoma in female CBA mice.     

The antioxidant tempol reduces carcinogenesis and enhances survival in mice when administered after nonlethal total body radiation

There is significant interest in the development of agents that can ameliorate radiation damage after exposure to radiation has occurred. Here we report that chronic supplementation of the antioxidant Tempol in the diet of mice can reduce body weight without toxicity, decrease cancer, and extend survival when administered after nonlethal total body radiation (TBI). These effects were apparent in two different strains of mice (C3H, CBA) exposed to TBI (3 Gy). Notably, delaying administration of the Tempol diet one month after TBI could also enhance survival. Tempol reduced the incidence of hematopoietic neoplasms (lymphomas) in both strains, whereas both the onset and incidence of nonhematopoietic neoplasms were reduced in CBA mice. These results encourage further study of Tempol as a chemopreventive, to reduce the incidence of radiation-induced second malignancies after a course of definitive radiation therapy. Tempol may also find applications to reduce the risk of cancers in populations exposed to nonlethal radiation due to nuclear accidents or terrorist attacks. Cancer Res; 72(18); 4846-55. ?2012 AACR.