The radiation response of SCCVII tumor cells in C3H/He mice varies with the irradiation conditions

The radiation response of SCCVII tumor cells in C3H/He mice under various irradiation conditions was studied using an in vivo-in vitro assay. When tumor-bearing mice were irradiated without anesthesia or physical restraint, the tumor had a hypoxic fraction of 5.4%. Both anesthesia and immobilization of the tumor-bearing leg with adhesive tape produced significant increases in the hypoxic fraction (23 and 28%, respectively). Restraining the mouse in a jig without immobilizing the tumor-bearing leg also increased the hypoxic fraction (13%).     

Development of a cellular immune response in a highly cancer-susceptible C3H/He strain of mice and its nonfactor substrain C3H/f after the transplantation of a syngeneic mammary gland tumor]

Syngeneic mammary gland tumor (MMT-1) grew slower in non-factor C3H/f (MTV-L) mice than in wirus-positive C3H/He (MTV-S) mice. The immunization of mice with tumor (MMT-1), inoculated and later excised, revealed a higher immune reactivity in the mice of the non-factor substrain. In studying the dynamics of the cytotoxic activity of lymphocytes in regional lymph nodes cytotoxically active lymphocytes were found to appear in C3H/f mice on day 6 after the inoculation of tumor (MMT-1), while the areactive state of lymphocytes was observed in C3H/He mice on days 3 and 24 and in C3H/f mice on day 24 after the inoculation of tumor (MMT-1). Spleen lymphocytes in C3H/f mice had no cytotoxic effect on tumor cells.     

Trypanosoma cruzi specific antibody response in immunized C3H(He) mice during infection

C3H(He) mice previously immunized with live culture derived Corpus Christi strain T. cruzi are significantly protected (up to 100% survival) against challenge by Brazil strain blood trypanosomes. The antibody response, directed against the Brazil strain or the Corpus Christi strain, in these mice has been observed by comparing sera from mice immunized only, infected only, or immunized and infected. The anti- T. cruzi titers determined by both direct agglutination (DA) and indirect fluorescence (IFA) were routinely found to be highest for immunized and infected mice with immunized mice and infected mice following in decreasing order. The use of mercaptoethanol treatment of sera (DA) and isotope specific second antibody (IFA) showed that IgG is the major parasite specific immunoglobulin response through infection. Evidence of cross-reacting antigens on the two parasite strains was found. By both DA and IFA, 11 of 18 anti-Brazil strain monoclonal antibodies were found to react (IFA titers of 320 or greater) with both parasite strains. No evidence of localization of cross-reacting antigens (using mouse antisera) or antigenic determinants (using monoclonal antibodies) was found in that uniform fluorescence over the parasite was observed in all IFA tests.     

The effects of LPS on the cellular composition of the splenic white pulp in responder C3H/He and non-responder C3H/HeJ mice

The aim of the present study was to compare the effects of LPS on the cellular composition of the splenic white pulp in responder C3H/He and non-responder C3H/HeJ mice. The present results show that an intravenous injection of LPS in C3H/He mice results in a number of prominent changes in the histology of the spleen, but none of these histological changes could be demonstrated in the unresponsive C3H/HeJ mice. However, the present study shows that LPS administration resulted in the disappearance of previously trapped immune complexes from the follicles in both responder C3H/He and non-responder C3H/HeJ mice. The significance of this phenomenon is discussed. The localization of intravenously injected LPS in both mouse strains was compared using an immunoperoxidase technique. Most of the injected LPS was taken up by marginal zone macrophages at 2 h after administration. No major differences could be detected in the localization pattern of LPS between C3H/He and C3H/HeJ mice. The present results support the suggestion that the genetically based unresponsiveness of C3H/HeJ mice could be due to an intracellular defect in their response to LPS.     

Radiation-induced myeloid leukemia in C3H/He mice and the effect of prednisolone acetate on leukemogenesis

We found that the incidence of spontaneous myeloid leukemia in C3H/He male mice was less than 1%, but it could be increased considerably by total-body X irradiation. The induction of myeloid leukemia was seen to increase after doses from 0.47 Gy (3%) to 2.84 Gy (23.9%), and then decrease after a dose of 4.73 Gy (13.6%). The administration of prednisolone acetate (synthesized glucocorticoid) after irradiation resulted in a significant increase in the incidence of myeloid leukemia from 23.9 to 38.5% after a dose of 2.84 Gy; however, corticosterone, a glucocorticoid secreted by cells, did not have such an enhancing effect.     

Cytogenetic analysis of radiation-induced leukemia in Trp53-deficient C3H/He mice

C3H/He mice develop acute myeloid leukemia (AML) after whole-body irradiation, but the strain becomes highly susceptible to stem cell leukemia (SCL) when a null mutation is introduced into the Trp53 gene. To examine the etiology of SCL and the influence of chromosomal instability on leukemogenesis, 12 SCLs and two AMLs arising from Trp53-deficient C3H/He mice were investigated cytogenetically. Each SCL demonstrated cell-to-cell variation in the number and structural integrity of their chromosomes, indicating chromosomal instability. Typical deletion of chromosome 2 was observed in the two AML cases, while most SCL cells did not display this aberration. Deletions and rearrangements of chromosome 11 were noticeable in SCLs from Trp53 heterozygotes but not in AMLs. Analysis of loss of heterozygosity revealed that aberrations involving chromosome 11 in SCLs resulted in loss of the wild-type Trp53 allele. These results suggest that loss of Trp53 function triggers the tumorigenic process leading toward SCL through the induction of chromosomal instability, and that SCL and AML are distinct varieties of leukemia.     

Comparison of glucokinase in C3H/He and C58 mice that differ in their hepatic activity

Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gk^a and Gk^b, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K _m values for MgATP^2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.).     

Comparison of mammary tumorigenesis between litters in relation to mammary tumor virus antigenic expression in the milk of C3H/He mice

As a possible step to estimate the relationship between mammary tumor virus (MTV) and mammary tumorigenesis in mice, MTV antigenic expression in mother's milk and spontaneous mammary tumorigenesis in their daughters were compared between the 1st, the 2nd and the 3rd litters of the highly inbred strains of C3H/He mice with low mammary tumor incidence. While MTV antigenic expression was detected in all undiluted samples at each litter by immunodiffusion test, the amount of antigen as measured by the single radial immunodiffusion method was increased with increasing litter numbers. On the other hand, the development of preneoplastic mammary hyperplastic alveolar nodules was different little between litters and mammary tumor incidence by 13 months of age was very low with no difference in all litters. The pattern of estrous cycles and plasma prolactin level were also similar in each litter. The results suggest that spontaneous mammary tumorigenesis in mice is not always affected quantitatively by the amount of MTV when endocrine and genetical conditions are similar.     

Forestomach ulcers in Crj:B6C3 (C57BL/6NCrj x C3H/HeNCrj) F1 mice

An unusually high incidence of forestomach ulcers was observed in a mouse strain that is used frequently for long-term toxicology studies. Examination of 98 untreated male and 98 untreated female B6C3F1 hybrid mice, the majority of which were between 105 and 113 weeks of age, revealed forestomach ulcers in 52% of the males and 54% of the females. Glandular stomach ulcers were uncommon, being found in only four female mice. The incidence of the ulcers increased with age. The etiology of the lesion is unknown.     

Dietary manipulation of mammary tumor development in adult C3H/Bi mice

Chronic energy intake restriction (CEIR) in virgin female mice is one of the most effective ways of reducing significantly mammary adenocarcinoma in C3H/Bi mice, a strain which develops mammary adenocarcinoma associated with the murine mammary tumor virus spontaneously and at high incidence. In this study, the influence of chronic energy intake restriction imposed on fully mature (4- to 5-month-old), breeding female C3H/Bi mice was addressed, and the influence of energy intake where energy was derived largely from fat versus diets in which energy was derived largely from carbohydrates on tumor development and survival rate was investigated. The results show that chronic energy intake restriction can be delayed until full maturation and successful reproduction and still reduce significantly the incidence of mammary tumor development in this relatively short-lived strain of mice. Our findings demonstrate that the overriding dietary factor controlling mammary tumor development in these experiments in C3H/Bi mice was the level of energy intake, regardless of the primary source of energy (fat or carbohydrates).     

Analysis of free growth and post-treatment regrowth of C3H mammary carcinoma in individual mice

Free growth and post-Doxorubicin treatment regrowth of the C3H mammary carcinoma were analysed in individual mice. In both cases, the Gompertzian function provided a better fit than the exponential function, and the difference was statistically significant (P less than 0.001, chi 2 test). No comprehensive Gompertzian function was found, and each individual tumour growth or regrowth was described by a specific curve. Nevertheless, although both individually measured alpha 0 and beta, Gompertzian parameters varied from one animal to another, in both free-growing and post-treatment regrowing tumours a strong linear correlation between alpha 0 and beta was found. A parallelism test was performed to verify if there exists any treatment-induced alteration. The two regression lines appeared to be identical, however.     

Adaptive response and the bystander effect induced by radiation in C3H 10T(1/2) cells in culture.

This paper discusses two phenomena of importance at low doses that have an impact on the shape of the dose-response relationship. First, there is the bystander effect, the term used to describe the biological effects observed in cells that are not themselves traversed by a charged particle, but are neighbors of cells that are; this exaggerates the effect of small doses of radiation. Second, there is the adaptive response, whereby exposure to a low level of DNA stress renders cells resistant to a subsequent exposure; this reduces the effect of low doses of radiation. The present work was undertaken to assess the relative importance of the adaptive response and the bystander effect induced by radiation in C3H 10T(1/2) cells in culture. When the single-cell microbeam delivered from 1 to 12 alpha particles through the nuclei of 10% of C3H 10T(1/2) cells, more cells were inactivated than were actually traversed by alpha particles. The magnitude of this bystander effect increased with the number of particles per cell. An adaptive dose of 2 cGy of gamma rays, delivered 6 h beforehand, canceled out about half of the bystander effect produced by the alpha particles.     

Lipid phosphate phosphatase-1 expression in cancer cells attenuates tumor growth and metastasis in mice

Lipid phosphate phosphatase-1 (LPP1) degrades lysophosphatidate (LPA) and attenuates receptor-mediated signaling. LPP1 expression is low in many cancer cells and tumors compared with normal tissues. It was hypothesized from studies with cultured cells that increasing LPP1 activity would decrease tumor growth and metastasis. This hypothesis has never been tested in vivo. To do this, we inducibly expressed LPP1 or a catalytically inactive mutant in cancer cells. Expressing active LPP1 increased extracellular LPA degradation by 5-fold. It also decreased the stimulation of Ca²⁺ transients by LPA, a nondephosphorylatable LPA_1/2 receptor agonist and a protease-activated receptor-1 peptide. The latter results demonstrate that LPP1 has effects downstream of receptor activation. Decreased Ca²⁺ mobilization and Rho activation contributed to the effects of LPP1 in attenuating the LPA-induced migration of MDA-MB-231 breast cancer cells and their growth in 3D culture. Increasing LPP1 expression in breast and thyroid cancer cells decreased tumor growth and the metastasis by up to 80% compared with expression of inactive LPP1 or green fluorescent protein in syngeneic and xenograft mouse models. The present work demonstrates for the first time that increasing the LPP1 activity in three lines of aggressive cancer cells decreases their abilities to produce tumors and metastases in mice.