Tumor-bearing Female Mice Research Articles

Myeloid-derived suppressor cell subset heterogeneity drives glioblastoma progression in a sex-dependent manner

Abstract Immunosuppression is a major factor facilitating glioblastoma (GBM) progression and therapeutic resistance. We previously demonstrated that myeloid-derived suppressor cells (MDSCs) expand in GBM patients, but the mechanisms by which MDSC subsets promote tumorigenesis remain unknown. Using multiple syngeneic mouse GBM models, we show that monocytic MDSCs (mMDSCs) accumulate in tumors of males and associate with poor prognosis. Consistent with preclinical observations, males, who constitute 60% of GBM patients and have a worse prognosis than females, had significantly more tumor-infiltrating mMDSCs. In contrast, female tumor-bearing mice had a two-fold increase in circulating granulocytic MDSC (gMDSC) frequency, and a high gMDSC gene signature correlated with poor prognosis of female patients. Male-to-female bone marrow transplantation indicated that immune cell-intrinsic discrepancies drive the sex differences in GBM survival. In line with the differential MDSC localization, targeting gMDSCs with anti-Ly6G neutralizing antibodies extended the lifespan of female mice without affecting males. However, mMDSCs were protected from the anti-Ly6C depletion strategy due to their systemic and local proliferation, as indicated by ex vivo Ki-67 staining and subsequently confirmed by gene expression analysis. Drug-prediction using the differential expression profiles and subsequent pre-clinical testing established that mMDSCs can be targeted by chemotherapies, while IL-1 inhibitors are effective against gMDSCs. These findings indicate that MDSC subset variation represents an opportunity for improved immunotherapy efficacy while accounting for sex as a biological variable.

Cancer Attenuates Nutrient Activation of Skeletal Muscle mTORC1 in Female Mice

Cancer‐induced metabolic disruptions can alter tissue specific energy demands and has the potential to alter muscle responses to feeding. Mechanistic target of rapamycin complex 1 (mTORC1) signaling axis is activated by nutrient stimuli, and cancer cachexia can suppress basal muscle mTORC1 signaling in mice. However, gaps still remain in our understanding of how the cancer environment effects skeletal muscle nutrient regulation of mTORC1 signaling.PurposeWe examined the effect of feeding on skeletal muscle mTORC1 signaling in female tumor bearing mice.MethodsFemale C57BL/6 (B6) and ApcMin/+ (MIN) mice were fasted for 12‐hrs during the light cycle. Following the 12‐hr fast, mice were given access to a food pellet for 1‐hr (B6 FED:N=7, MIN FED:N=8) or fasted for another hour (B6 FAST:N=6, MIN FAST:N=7). Circulating blood glucose, and plasma IL‐6 and insulin were taken prior to sacrifice. Gastrocnemius muscle was homogenized for protein analysis. Statistical significance was set at p£0.05.ResultsThe MIN FED and MIN FAST groups were not different in percent body weight change, polyp number, plasma IL‐6, and hindlimb muscle mass. 1‐hour food intake was not different between B6 FED and MIN FED mice. Both MIN FED and B6 FED increased stomach mass, blood glucose, and circulating insulin levels. Compared to FAST mice, FED mice increased p70S6K and rpS6 phosphorylation, and was positively associated to insulin in both B6 and MIN mice. 4E‐BP1 phosphorylation was increased in the B6 FED compared to B6 FAST, but this response was blunted in the MIN FED. Additionally, circulating insulin concentration was associated to 4E‐BP1 phosphorylation in the B6 FED, but not in the MIN FED.ConclusionThe cancer environment can suppress the nutrient‐induced phosphorylation of skeletal muscle 4E‐BP1. Future studies are warranted to determine if the combination of exercise or muscle contraction can improve skeletal muscle mTORC1’s response to nutrients in the female cancer environmentAcknowledgementsNCI R01‐CA121249

Biological Sex Mediates Cancer Cachexia Associated Muscle Weakness

Cancer cachexia is a complex metabolic and wasting disease that results in death in up to one‐third of cancer patients and affects up to 80%. Currently, there are no clear diagnostic criteria, its effects are irreversible, and it cannot be treated. Therefore, a great need exists to better understand this disease. Furthermore, recent evidence states that cancer cachexia presents in a sexually dimorphic manner. Therefore, the purpose of this study was to determine whether cancer cachexia alters skeletal muscle function in a sexually dimorphic manner and to determine underlying mechanisms responsible for muscle wasting. Male and female mice underwent a 3 week period of tumor bearing (1×106 LLC cells in flank). Both male and female tumor bearing mice exhibited a loss in grip strength compared to baseline values. Interestingly, males exhibited a significantly greater loss in grip strength compared females (−17% vs −13%, P < 0.05). Male mice also exhibited significantly larger tumors compared to female mice (P < 0.01). Next, possible mechanisms responsible for cancer cachexia‐mediated muscle wasting were investigated. Since protein degratory pathways are known to play an important role in pathological muscle wasting, autophagy was investigated. Interestingly, while both male and female gastrocnemius exhibited an increase in LC3‐II protein levels (increased autophagy) compared to non‐tumor bearing controls, only female gastrocnemius LC3‐II levels were significantly increased (P<0.05). Since inflammation is thought to exacerbate pathological muscle wasting, IL‐1beta was investigated. Both male and female gastrocnemius exhibited increased IL‐1beta compared to non‐tumor bearing controls, though only male gastrocnemius exhibited a significant increase in IL‐1beta protein levels (P < 0.05). These data indicate that cancer cachexia does result in skeletal muscle weakness in a sexually dimprophic manner and that possible underlying mechanisms may differ by biological sex. Such data are critical in elucidating how cancer cachexia variably presents and progresses by biological sex, and in the identification of therapeutic targets aimed at muscle wasting in a sex specific manner.

IMMU-01. MYELOID-DERIVED SUPPRESSOR CELL HETEROGENEITY DRIVES GLIOBLASTOMA PROGRESSION IN A SEX-DEPENDENT MANNER

Abstract An immunosuppressive tumor microenvironment is a major factor facilitating glioblastoma (GBM) progression and therapeutic resistance. Immunotherapies have had variable success in improving the outcome of GBM patients, suggesting that there is a need to gain insight into the mechanisms of immunosuppression. Our group previously demonstrated that myeloid-derived suppressor cells (MDSCs) expand in GBM patients and infiltrate tumors, where they suppress the activity of cytotoxic cells. However, the mechanisms by which individual MDSC subsets promote tumorigenesis remain understudied. Using the syngeneic mouse glioma models GL261, CT-2A and SB28, we show that monocytic MDSCs (mMDSCs) are prevalent in tumors and that their frequency is significantly higher in males, who constitute 60% of GBM patients and have a worse prognosis than females. mMDSC abundance was further associated with poor survival, and male mice reached morbidity endpoint earlier. Consistent with preclinical observations, male GBM patient specimens had significantly more IBA+CD204+ immunosuppressive myeloid cells compared to female GBM tissue. In contrast, female tumor-bearing mice had a two-fold increase in circulating granulocytic MDSC (gMDSC) frequency, while this population remained unchanged in males. Female-to-male bone marrow chimeras demonstrated that intrinsic discrepancies in immune cell characteristics drive the sex differences in survival. Consistent with the differential MDSC accumulation pattern, targeting gMDSCs with anti-Ly6G neutralizing antibodies extended the lifespan of female mice without providing a survival advantage to males. However, mMDSCs were protected from the anti-Ly6C depletion strategy due to their systemic and local proliferation, as indicated by ex vivo Ki-67 staining and subsequently confirmed by gene expression analysis. Drug-prediction algorithms using the differential RNA sequencing profiles demonstrated that mMDSCs can be targeted by chemotherapeutics, while immunomodulatory drugs are effective against gMDSCs. Collectively, these findings indicate that MDSC subset variation might represent a therapeutic opportunity for improved therapeutic efficacy of immunotherapies while accounting for sex as a biological variable.

The Effect of Estradiol Administration on Muscle Mass Loss and Cachexia Progression in Female Apc Min/+ Mice.

Cancer cachexia is a multifactorial muscle wasting condition characterized by severe body weight and muscle mass loss which is secondary to chronic disease. The mechanistic examination of cachexia has predominately focused on the male phenotype and created significant gaps in understanding cachexia progression in the female. Female hypogonadism can accompany cancer cachexia and is characterized by reduced circulating 17ß-estradiol and uterine atrophy. Estrogen has known functions in skeletal muscle homeostasis involving the regulation of muscle protein turnover, cellular stressors, and oxidative metabolism. However, 17ß-estradiol's ability to regulate cachexia progression in the female is not known. The purpose of this study was to determine the effect of gonadal function and estradiol administration on muscle mass loss and cachexia progression in female ApcMin/+ mice.Methods: Female C57BL/6 (B6; N = 82) and ApcMin/+ (MIN; N = 88) mice were used in two separate experiments. In experiment 1, mice were sacrificed at either 12 (N = 20) or 20 (N = 41) weeks of age. Body weight and estrous cycle presence was determined weekly. In experiment 2, B6 and MIN mice were randomly allocated to: Control (N = 17), received E2 pellet (E2, N = 18), ovariectomy surgery (OVX; N = 19) or ovariectomy surgery with E2 pellet (OVX + E2; N = 21). 17ß-estradiol was administered through an implanted slow-releasing pellet (0.1 mg). In estrogen and ovariectomy experiments, food intake, and functional outcomes were recorded 1 week prior to sacrifice.Results: We report that E2 administration prevented body weight loss, muscle mass loss, cage inactivity, and grip strength loss associated with cachexia. In skeletal muscle, E2 reduced skeletal muscle AMPK phosphorylation, improved mTORC1 signaling, and prevented mitochondrial dysfunction.Conclusion: Our results demonstrate a role for 17ß-estradiol for the prevention of skeletal muscle mass loss in female tumor bearing mice. Furthermore, 17ß-estradiol prevented cachexia's disruption in skeletal muscle signaling involving AMPK and mTORC1, in addition to improving mitochondrial function in female tumor bearing mice.

Synthesis of a 4-nitroimidazole indocyanine dye-conjugate and imaging of tumor hypoxia in BALB/c tumor-bearing female mice

Extending our previous work with 2-nitroimidazole-indocyanine dye-conjugate 4, we prepared the 4-nitroimidazole-piperazine-indocyanine derivative (6). We also prepared imidazole derivative 5 as a control. We compared the in vivo hypoxia targeting performance of both 5 and 6 with the previously tested 4, and 6 showed a higher fluorescent intensity after 15 min post-injection, about 1.5-fold higher than 4 and 2.5-fold higher than 5. Cells treated with 6 under hypoxic conditions showed a higher fluorescence yield when compared to the cells kept under normoxic conditions. All findings were supported with fluorescence images of histological sections of tumor samples using a Li-COR scanner and an immunohistochemistry technique for tumor hypoxia.

Chemosensitizing and nephroprotective effect of resveratrol in cisplatin -treated animals.

BackgroundCisplatin (CIS) is one of the most effective anticancer drug used in the treatment of several solid tumors .Its use is limited by its nephrotoxicity. The present study was designed to assess the role of a natural product resveratrol (RSVL) on sensitization of mammary carcinoma (Ehrlich ascites carcinoma) to the action of CIS and the possible protective effect against CIS-induced nephrotoxicity in rats.MethodsThe percent survival of female tumor bearing mice was used for determination the cytotoxic activity of CIS in the presence or the absence of RSVL. Uptake and cell cycle effect, serum creatinine (CREA), blood urea nitrogen (BUN), Reduced Glutathione (GSH) and histopatholgical examination of kidney tissues after CIS and/or RSVL therapy were also investigated.ResultsRSVL increased the intracellular level of CIS in EAC cells and there was a strong correlation between the high cellular level of CIS and its cytotoxicity. CIS at a dose level of 5 mg/kg increased the mean survival time of female tumor bearing mice to 25 days compared with 17 days for tumor-bearing control mice. Administration of RSVL at a dose level of 25 mg/kg simultaneously with CIS increased the mean survival time to 48 days with 60% survival of the tumor-bearing animals. Cell cycle analysis of tumor cells showed that CIS treatment decreases the proliferation index of tumor cells while in presence of RSVL there was more significant inhibitions. Also, CIS treatment caused increase in level of creatinine and blood urea with significant decrease in the GSH level. While, in the presence of RSVL, level of creatinine and blood urea restored to control level.ConclusionThis study suggests that RSVL could increase the cytotoxic activity of CIS and protect against its nephrotoxicity.

Sleep Deprivation Increases Mortality in Female Mice Bearing Ehrlich Ascitic Tumor

Objectives: Sleep deprivation is a growing public health hazard, yet it is still under-recognized. Sleep disorders and disruption of sleep patterns may compromise the immune function and adversely affect host resistance to infectious diseases. This is a particular risk in cancer patients, who report a high frequency of sleep disturbances. The present study investigated the effects of sleep deprivation on the development of Ehrlich ascitic tumors (EAT) in female BALB/c mice. Our study also evaluated whether EAT would induce alterations in sleep pattern. Spleen lymphocyte cell populations and mortality were also quantified. Methods: Female BALB/c mice were intraperitoneally inoculated with EAT cells. Immediately after the inoculation procedure, animals were sleep deprived for 72 h. Ten or 15 days after inoculation, the number of tumoral cells was quantified and the lymphocytic cell population in the spleen was characterized by flow cytometry. In addition, the effect of sleep deprivation on EAT-induced mortality was quantified and the influence of EAT on sleep patterns was determined. Results: Sleep deprivation did not potentiate EAT growth, but it significantly increased mortality. Additionally, both EAT and sleep deprivation decreased frequencies of splenic CD4+, CD8+ and CD19+ cells. With respect to sleep patterns, EAT significantly enhanced paradoxical sleep time. Conclusions: Although sleep deprivation did not potentiate EAT growth, it decreased the survival of female tumor-bearing mice.

Comparative pathological and cytogenetical study of ethanolic extract of Vinca rosea L. and Vinblastine in treating mammary gland adenocarcinoma implanted mice

Pathological, cytogenetical comparative study was the main objectives of this project between the influence of ethanolic extract of Vinca rosea and Vinblastine (vinca alkaloid) as chemotherapy. Fourty female adult Swiss albino balb/C mice of approximately body weight (20-26g) and age (8-10) weeks were used in whole experiments. In cytogenetic study two parameters mitotic index (MI) and blast index (BI) were used. The results showed significant increase (p‹0.05) in mitotic index (MI) and blast index (BI) values in groups treated with ethanolic extract of Vinca rosea. Also the results showed significant decrease in these values in groups treated with Vinblastine. Histopathological sections in control group showed the presence of tumor growth characterized by formation of acinar like structures, with pleomorphic tumor cells and hyperchromatic nuclei with a tendency to form giant cells and high numbers of mitotic figures with extensive areas of necrosis. The tumor showed metastasis in liver and Lung, with aggregation of tumor associated macrophages in liver. Histopathological sections in groups of tumor-bearing female mice, treated with ethanolic extract, were showed large areas of necrosis, mononuclear cell infiltration and encapsulate with fibrous connective tissue capsule with mononuclear cell infiltrations in lung and formation of early granuloma in liver. In chemotherapy, tissue sections showed vacuolation and necrosis of tumor cells which encapsulated with fibrous connective tissue. The pathological changes characterized by alopecia, and large pneumonic areas with extensive coagulative necrosis and apoptosis in liver with hyperplastic nodules formation. Bone section showed marked depletion of hemopoietic tissue of bone marrow and increased in the number of megakaryocytes, with signs of osteoporosis. We concluded that both ethanolic extract of Vinca rosea and Vinblastine have cytotoxic effect on transplanted mammary tumor cells in mice, with no side effect in case of Vinca rosea in comparison with vinblastine which cause severe pathological changes in internal target organs with signs of osteoporosis and precancerous lesions, with significant changes in the blood picture and in cytogenetic parameters.

In VivoAntitumor and Antioxidative Effects of a Rapeseed Meal Protein Hydrolysate on an S180 Tumor-Bearing Murine Model

The antitumor and antioxidative activities of a rapeseed protein hydrolysate (RSCH) obtained from rapeseed meal were evaluated by using an in vivo S180 tumor-bearing Kunming mice model. Tumor-bearing female mice were given RSCH for 10 at doses of 0, 50, 100, and 150 mg/kg/d by gastric perfusion. RSCH significantly decreased the tumor weight by 44% and 53% in the 100 and 150 mg/kg/d groups, respectively, without causing mortality or growth retardation. The thymus and spleen indices (organ weight relative to body weight) were increased significantly in the 150 mg/kg/d group. The phagocytic capability of coeliac macrophages and delayed-type hypersensitivity (DTH) were significantly increased in tumor-bearing mice treated with RSCH at 150 mg/kg/d. RSCH administration also enhanced the superoxide dismutase activity and reduced the serum level of thiobarbituric acid reactive substances. Our results show that an oral RSCH administration had an antitumor protective effect and may improve immune function by reducing free radical formation and oxidative stress in a murine model.

Gender dimorphism of tumor growth: role of gonadal hormones in differential regulation of apoptosis of a murine T cell lymphoma

The present investigation was undertaken to study if a gender-dependent differential induction of tumor cell apoptosis is responsible for the manifestation of gender dimorphism observed in the growth of a transplantable murine T cell lymphoma, designated as Dalton's lymphoma (DL). Tumor cell samples obtained from male tumor-bearing mice showed a higher number of cells with apoptotic morphology compared to that observed in female tumor-bearing mice. In this report we demonstrate that male hormone androgen and female hormone estrogen can differentially modulate tumor cell proliferation and apoptosis through alteration in the expression pattern of cell death regulating genes: p53 and CAD. DL cells were shown to express mRNA for androgen and estrogen receptors. Further these gonadal hormones also induced tumor cells to produce tumor growth regulating proteins: VEGF, TGF-beta, IL-2, IL-2R, SOCS, Hsp-70 and IFN-gamma which in turn either through autocrine action on tumor cells or via TAM-derived NO were observed to regulate tumor cell apoptosis leading to gender dimorphism of tumor growth. This study also discusses the possible mechanism involved. The study has clinical significance as these results will helps in understanding the mechanism of gender dimorphism with respect to the progression of T-cells tumors.

Gender dimorphism in the myeloid differentiation of bone marrow precursor cells in a murine host bearing a T cell lymphoma

Little information is available regarding the existence of gender dimorphism of tumor growth for most types of tumors. In a previous report we have demonstrated the existence of gender dimorphism in the growth of a murine T cell lymphoma, designated as Dalton's lymphoma (DL); moreover, tumor-associated macrophages (TAM) were found to play a central role in the manifestation of gender dimorphism observed in the growth of this T cell lymphoma. In view of these observations, the present investigation was undertaken to study if gender dimorphism in the growth of a T cell tumor also could be associated with a gender-dependent differential myelopoiesis of bone marrow cells. We have demonstrated the existence of a gender dimorphism in the proliferation, apoptosis and myeloid differentiation of bone marrow cells obtained from male and female tumor-bearing hosts. Androgen and estrogen were found to alter directly the growth properties of bone marrow cells, as also determined by the use of receptor antagonists of these hormones, flutamide and tamoxifen. Bone marrow cells of male and female tumor-bearing hosts also showed a differential expression of the cell cycle and apoptosis regulatory protein p53 and macrophage-colony stimulating factor (M-CSF) genes. Bone marrow cells of male tumor-bearing hosts showed a predominant differentiation in the macrophage lineage whereas those of female tumor-bearing mice were in the granulocyte lineage. Bone marrow-derived macrophages (BMDM) from male and female tumor-bearing mice also showed the existence of gender dimorphism with respect to their differentiation and activation. These observations are of clinical significance with respect to understanding of the host–tumor relationship at the level of gender dimorphism of myelopoiesis.

Anesthetic Agents Modify Tissue Proteinase Inhibitor Content and Tumor Behavior

Anesthetic agents may modify the tissue content of low molecular weight proteinase inhibitors (mol wt less than 50,000) and affect the colonization and proliferation of B16-F10 melanoma cells in lungs. Lungs of female mice exposed to halothane in oxygen had significantly greater low molecular weight proteinase inhibitor activity than those from unexposed female mice. The amount of activity in male mice similarly exposed did not differ from unexposed controls. Lungs of exposed female mice also had greater activity as compared with males similarly exposed. No differences occurred in identical experiments with ketamine. High-performance liquid chromatography revealed that the inhibitor in all groups of both sexes shared a major peak with a molecular weight similar to that of the trypsin inhibitor aprotinin. Female mice bearing B16-F10 melanoma cells and exposed to halothane in oxygen had significantly more small lung tumor nodules than tumor-bearing female mice injected with ketamine. However, the total number of nodules did not differ between the two groups. These observations support the hypothesis that stimulation of proteinase inhibitory activity by halothane in oxygen may be responsible for an inhibition of tumor cell proliferation, resulting in smaller tumor nodules and no effect on the incidence of colonization.

Diabetes and retinal function.

<h3>Background</h3> A potently immunosuppressive tumor microenvironment facilitates progression of glioblastoma (GBM). Immunotherapies have had variable success in improving the outcome of GBM patients, suggesting that there is a need to gain insight into the mechanisms of immunosuppression. Our findings indicated that proliferating monocytic MDSCs (mMDSCs) accumulate in tumors of male mice and patients, while female tumor-bearing mice had an increase in circulating granulocytic MDSC (gMDSC) frequency, and a high gMDSC gene signature correlated with worse outcome of female patients. <h3>Methods</h3> To investigate the basis and prognostic value of sex differences in MDSC profile, we analyzed the role of sex hormones, determined gene expression signatures of MDSCs and preclinically tested the therapeutic benefit of candidate drugs predicted to be effective against individual MDSC subsets. <h3>Results</h3> In line with the differential MDSC accumulation pattern, targeting the systemic gMDSCs with the anti-Ly6G neutralizing antibody extended the lifespan of female mice without affecting males. These differences were not driven by sex steroids, as castration or ovariectomy failed to alter MDSC subset accumulation patterns in GBM-bearing mice. Drug-prediction algorithms using the differential MDSC gene expression profiles predicted IL-1 inhibitors are effective against gMDSCs. Correspondingly, IL-1β was highly expressed in female but not male gMDSCs. Single-cell sequencing revealed that circulating but not tumor-infiltrating gMDSCs were the primary source of IL-1β and that its neutralization provided a female-specific survival advantage by reducing circulating gMDSCs. This was accompanied by declines in tumor infiltration of microglia, microglia activation status and tumor cell proliferation. In vitro, IL-1β inhibition reduced viability and expression of activation markers by primary microglia. <h3>Conclusions</h3> These findings highlight a novel peripheral gMDSC-microglia IL-1β mediated communication axis in female GBM and indicate expression differences in MDSC subsets can be leveraged for improved immunotherapy efficacy in a sex-specific, precision medicine strategy.

Amino Acid-Restricted Diets in the Treatment of Mammary Adenocarcinoma in Mice

The effect of a diet moderately restricted in tryptophan on the tumor and the nutritional status of C3H mice bearing mammary adenocarcinoma was examined. Five groups of female tumor-bearing mice were fed ad libitum a diet containing 1) 15% casein, 2) 15% amino acid mixture, 3) 15% amino acid mixture restricted in tryptophan 4) 15% zein supplemented with lysine and tryptophan or 5) 15% zein supplemented with lysine and restricted in tryptophan. Another group of tumor-free mice of similar age fed 15% casein served as a control for the tumor-bearing group fed the 15% casein diet. Moderate restriction of tryptophan in the diet appeared to have no effect on the tumor status of the animal. Tumor burden usually induced malnutrition in the animal. However, tryptophan restriction did not further aggravate this malnutrition. The source of protein, whether casein, amino acid mixture or zein, appeared to make a difference in nutritional status of tumor-bearing animals though not in tumor status. Casein-fed animals generally tended to have higher values for all the nutritional markers studied than did animals fed the amino acid mixture or zein.

Androgen-dependent human prostate cancer in nude mice. The PC-82 tumor model.

Permanent transplantable human tumors in nude mice offer the possibility of studying the impact of different (endocrine) treatment regimens on human cancer tissue. Among the limited number of human tumor models in athymic nude mice developed so far, the PC-82 tumor (which was established in our institution) mimics many of the important properties of clinical prostate cancer. The absence of PC-82 tumor growth in intact female and in castrated male mice indicates the absolute requirement of androgen for the growth of this tumor. Delayed testosterone (T) substitution (up to 70 days after tumor grafting) in PC-82 transplanted female mice resulted in tumor growth. This indicated that after androgen withdrawal at least part of the cells do not die and keep the capability to respond to androgens. Androgen withdrawal from T-implanted tumor-bearing female mice caused a rapid reduction (90% within 1 day) of the tissue T and a slower decline (up to 90% within 7-10 days) of tissue DHT concentrations. By the use of Silastic implants, containing different proportions of T mixed with cholesterol, circulating T levels of 0.2-20 nmol/L were obtained. It was observed that a constant plasma T level between 1 and 2 nmol/L (achieved with 10% T implants) is the threshold below which growth of the PC-82 tumor tissue is no longer stimulated.

Age- and Sex-Related Differences in Antibody Formation And Blastogenic Responsiveness of Splenocytes From RIII Mice Developing Virus-Induced Mammary Adenocarcinoma&lt;xref ref-type="fn" rid="fn2"&gt;2&lt;/xref&gt;

Inbred RIII mice, known to be infected neonatally with murine mammary tumor virus so that females develop mammary adenocarcinoma by 12-15 months of age, were examined with regard to antisheep red blood cell antibody responses at the cellular level. Female mice, 3-11 months old, compared to male mice of the same ages had consistent and significant depression of the antibody response of their splenocytes. Furthermore, female mice with adenocarcinoma showed an even greater depression of the antibody response. Spleen sizes were consistently increased in females as compared to those of male mice throughout the first year of life. The blastogenic responsiveness of the splenocytes to the B-cell mitogen Escherichia coli lipopolysaccharide and the T-cell mitogen phytohemagglutinin-P was not significantly different between male and female mice during the same periods, although the responses of the older tumor-bearing female mice to phytohemagglutinin-P were lower than those of non-tumor-bearing female mice. A complex relationship between age, sex, and immune responsiveness was evident in these mammary tumor virus-infected mice, which made it difficult to attribute a specific immune event to emergence of the mammary adenocarcinomas in the female as compared to male mice.