Protein Kinase CK2 Controls CD8+ T Cell Effector and Memory Function during Infection

Protein kinase CK2 is a serine/threonine kinase composed of two catalytic subunits (CK2α and/or CK2α') and two regulatory subunits (CK2β). CK2 promotes cancer progression by activating the NF-κB, PI3K/AKT/mTOR, and JAK/STAT pathways, and also is critical for immune cell development and function. The potential involvement of CK2 in CD8⁺ T cell function has not been explored. We demonstrate that CK2 protein levels and kinase activity are enhanced upon mouse CD8⁺ T cell activation. CK2α deficiency results in impaired CD8⁺ T cell activation and proliferation upon TCR stimulation. Furthermore, CK2α is involved in CD8⁺ T cell metabolic reprogramming through regulating the AKT/mTOR pathway. Lastly, using a mouse Listeria monocytogenes infection model, we demonstrate that CK2α is required for CD8⁺ T cell expansion, maintenance, and effector function in both primary and memory immune responses. Collectively, our study implicates CK2α as an important regulator of mouse CD8⁺ T cell activation, metabolic reprogramming, and differentiation both in vitro and in vivo.

Neutrophil-specific Socs3 deficiency induces brain-targeted experimental autoimmune encephalomyelitis with increased cerebellar neutrophils

Multiple sclerosis (MS) is associated with a dysregulated JAK/STAT signaling pathway. Suppressors of cytokine signaling (SOCS) negatively regulate the JAK/STAT pathway. MS patients with disease affecting the cerebellum display rapid progression and poor prognosis. Previous data from our laboratory demonstrates a severe, brain-targeted form of experimental autoimmune encephalomyelitis (EAE) in mice lacking Socs3 in myeloid cells (Socs3ΔLysM), with increased cerebellar infiltration of primed neutrophils. Here, we induced EAE in mice lacking Socs3 specifically in neutrophils (Socs3ΔLy6G; n=26) and Ly6G−/+ control mice (n=13), and examined disease progression, neutrophil populations and CD4+ T-cell polarization at disease peak. Ly6G−/+ mice exhibited clinical signs of classical EAE, whereas Socs3ΔLy6G mice exhibited clinical signs of brain-targeted EAE, similar to Socs3ΔLysM mice. An analysis of the cerebellar cell infiltrate in Socs3ΔLy6G mice demonstrated an increased cellularity (p=0.005), which was comprised of both an increase in the percentage (p=0.020) and total number (p<0.001) of cerebellar neutrophils. Neutrophils from Socs3ΔLy6G mice exhibited a primed phenotype with increased surface expression of CD11b (p=0.084) and reduced expression of CD62L (p<0.001). Additionally, Socs3ΔLy6G mice exhibited an increase in the percent of cerebellar CD4+ T-cells (p=0.018) and a shift toward IFN-γ-producing Th1 CD4+ T-cells (p=0.012). These data conclusively document that neutrophil-specific deficiency of Socs3 is sufficient to induce brain-targeted EAE. Future studies will identify targets to dampen the role of neutrophils in brain-targeted autoimmune neuroinflammation.

Manipulating the Wnt/β-catenin signaling pathway to promote anti-tumor immune infiltration into the TME to sensitize ovarian cancer to ICB therapy

OBJECTIVE

Immune checkpoint blockade (ICB) therapy shows limited efficacy in ovarian cancers due to the "cold" immune phenotype surrounding these tumors. Previous studies have shown that in ovarian cancer Wnt/β-catenin pathway activation contributes to this immune phenotype. Here, we evaluated the anti-tumor and immune-enhancing properties of the Wnt inhibitor, CGX-1321, used alone or in combination with either DKN-01 or anti-PD-1 therapy, in pre-clinical ovarian cancer models.

METHODS

The parental ID8 murine ovarian cancer model harboring a knock-out of p53 (ID8p53^-/-) and MISIIR-Tag spontaneous ovarian cancer models were used to test the effects of CGX-1321 alone or in combination therapies on tumor burden and immune cell landscape in the tumor microenvironment (TME). Flow cytometry and NanoString analyses were used to characterize the changes in tumor-intrinsic signaling and immune-related profiles in the TME of ovarian cancer in response to treatments.

RESULTS

CGX-1321 significantly reduced tumor burden and constrained tumor progression in the ID8p53^-/- and MISIIR-Tag models. Furthermore, CGX-1321 increased infiltrating CD8+ T cells in the TME. Combining CGX-1321 with either DKN-01 or anti-PD-1 therapy also decreased tumor burden and increased CD8+ T cell infiltration in the omentum TME but did not do so to a greater extent that CGX-1321 monotherapy.

CONCLUSIONS

CGX-1321 significantly reduced tumor burden and enhanced CD8+ T cell levels in ovarian cancer, nevertheless the addition of DKN-01 or anti-PD-1 therapies did not enhance these effects of CGX-1321. Further investigation is needed to determine if CGX-1321 + DKN-01 combination treatment sensitizes pre-clinical ovarian cancer to ICB therapy.

Therapeutic Time-restricted Feeding Reduces Renal Tumor Bioluminescence in Mice but Fails to Improve Anti-CTLA-4 Efficacy

BACKGROUND/AIM

Dietary interventions like time-restricted feeding (TRF) show promising anti-cancer properties. We examined whether therapeutic TRF alone or combined with immunotherapy would diminish renal tumor growth in mice of varying body weights.

MATERIALS AND METHODS

Young (7 week) chow-fed or older (27 week) high-fat diet (HFD)-fed BALB/c mice were orthotopically injected with renal tumor cells expressing luciferase. After tumor establishment, mice were randomized to ad libitum feeding or TRF +/- anti-CTLA-4. Body composition, tumor viability and growth, and immune responses were quantified.

RESULTS

TRF alone reduced renal tumor bioluminescence in older HFD-fed, but not young chow-fed mice. In the latter, TRF mitigated tumor-induced loss of lean- and fat-mass. However, TRF did not alter excised renal tumor weights or intratumoral immune responses and failed to improve anti-CTLA-4 outcomes in any mice.

CONCLUSION

Therapeutic TRF exhibits modest anti-cancer properties but fails to improve anti-CTLA-4 immune checkpoint blockade in murine renal cancer.

Obesity-Associated Myeloid-Derived Suppressor Cells Promote Apoptosis of Tumor-Infiltrating CD8 T Cells and Immunotherapy Resistance in Breast Cancer

Nearly 70% of adults in the US are currently overweight or obese. Despite such high prevalence, the impact of obesity on antitumor immunity and immunotherapy outcomes remains incompletely understood, particularly in patients with breast cancer. Here, we addressed these gaps in knowledge using two murine models of breast cancer combined with diet-induced obesity. We report that obesity increases CXCL1 concentrations in the mammary tumor microenvironment, driving CXCR2-mediated chemotaxis and accumulation of granulocytic myeloid-derived suppressor cells (G-MDSCs) expressing Fas ligand (FasL). Obesity simultaneously promotes hyperactivation of CD8 tumor-infiltrating lymphocytes (TILs), as evidenced by increased expression of CD44, PD-1, Ki-67, IFNγ, and the death receptor Fas. Accordingly, G-MDSCs induce Fas/FasL-mediated apoptosis of CD8 T cells ex vivo and in vivo. These changes promote immunotherapy resistance in obese mice. Disruption of CXCR2-mediated G-MDSC chemotaxis in obese mice is sufficient to limit intratumoral G-MDSC accumulation and improve immunotherapy outcomes. The translational relevance of our findings is demonstrated by transcriptomic analyses of human breast tumor tissues, which reveal positive associations between CXCL1 expression and body mass index, poor survival, and a MDSC gene signature. Further, this MDSC gene signature is positively associated with FASLG expression. Thus, we have identified a pathway wherein obesity leads to increased intratumoral CXCL1 concentrations, which promotes CXCR2-mediated accumulation of FasL⁺ G-MDSCs, resulting in heightened CD8 TIL apoptosis and immunotherapy resistance. Disruption of this pathway may improve immunotherapy outcomes in patients with breast cancer and obesity.

Wnt signaling modulator DKK1 as an immunotherapeutic target in ovarian cancer

OBJECTIVES

Wnt pathway mutations are a hallmark of endometrioid and clear cell subtypes of epithelial ovarian carcinoma (EOC). However, no drugs targeting the Wnt pathway in EOC are FDA-approved. Dickkopf-related protein 1 (DKK1), a modulator of the Wnt pathway, has emerged as a promising therapeutic target. We aimed to examine the role of DKK1 and the effects of a monoclonal antibody against DKK1 (DKN-01) in vivo and in a murine model of ovarian cancer.

METHODS

We examined in vitro the role of DKK1 and the effects of DKK1 inhibition in EOC cell lines. We then studied in vivo the role of DKN-01 and DKK1 overexpression on tumor burden and anti-tumor immune cell populations using the ID8 syngeneic mouse model.

RESULTS

DKN-01 did not phenotypically alter ES2 cells in vitro; however, DKK1 inhibition promoted Wnt signaling. Tumor burden and immune populations were unchanged in ID8 challenged mice treated with mDKN01. Mice challenged with ID8 cells overexpressing DKK1 had tumor burden similar to controls (p = 0.175). However, the overexpression of DKK1 decreased CD45⁺ leukocyte infiltration into the peritoneum (p = 0.008) and omentum (p = 0.032), reducing both natural killer (NK) and CD8 T cells, and reducing interferon-gamma (IFNγ) expression on activated CD8 T cells.

CONCLUSIONS

Our results suggest that DKK1 inhibition does not affect tumor growth in the ID8 ovarian cancer model. DKK1 overexpression alters anti-tumor immune populations within the tumor microenvironment. Thus, our findings confirm DKK1 as a new therapeutic target in EOC and suggest that DKK1 inhibition may function best in a combinatorial, immune-modulatory therapy.

Obesity and CD8 T cell metabolism: Implications for anti-tumor immunity and cancer immunotherapy outcomes

Obesity is an established risk factor for many cancers and has recently been found to alter the efficacy of T cell-based immunotherapies. Currently, however, the effects of obesity on immunometabolism remain unclear. Understanding these associations is critical, given the fact that T cell metabolism is tightly linked to effector function. Thus, any obesity-associated changes in T cell bioenergetics are likely to drive functional changes at the cellular level, alter the metabolome and cytokine/chemokine milieu, and impact cancer immunotherapy outcomes. Here, we provide a brief overview of T cell metabolism in the presence and absence of solid tumor growth and summarize current literature regarding obesity-associated changes in T cell function and bioenergetics. We also discuss recent findings related to the impact of host obesity on cancer immunotherapy outcomes and present potential mechanisms by which T cell metabolism may influence therapeutic efficacy. Finally, we describe promising pharmaceutical therapies that are being investigated for their ability to improve CD8 T cell metabolism and enhance cancer immunotherapy outcomes in patients, regardless of their obesity status.

Increased Adiposity Enhances the Accumulation of MDSCs in the Tumor Microenvironment and Adipose Tissue of Pancreatic Tumor-Bearing Mice and in Immune Organs of Tumor-Free Hosts

Obesity is associated with increased risk and reduced survival for many types of cancer. Increasing adiposity may affect the balance between immunosuppressive and antitumor mechanisms critical for dictating cancer progression or remission. The goal of the current study was to determine if increased adiposity altered tumor growth, survival, and myeloid-derived suppressor cell (MDSC) accumulation in a subcutaneous murine model of pancreatic cancer. C57BL/6 mice were placed on a 30% kcal calorie-restricted diet, 10% kcal from fat diet fed ad libitum, or 60% kcal from fat diet fed ad libitum for 16 weeks to generate lean, overweight, and obese mice, respectively; followed by subcutaneous injection with 1 × 10⁶ Panc.02 cells. We observed a significant linear relationship between increased adiposity and increased tumor growth and mortality; increased accumulation of Gr-1⁺CD11b⁺ MDSCs; and reduced CD8 T cell:MDSC ratio in multiple tissues, including tumor. Increased adiposity also increased the accumulation of MDSCs in the spleen and lymph node of tumor-free mice. These data suggest adiposity induces MDSC accumulation, which may contribute to an immunosuppressive environment promoting tumor growth. Overall, our findings provide a rationale to prevent or reverse increased body weight as a strategy to reduce the accumulation of immunosuppressive cell types.

Physical Activity Plus Energy Restriction Prevents 4T1.2 Mammary Tumor Progression, MDSC Accumulation, and an Immunosuppressive Tumor Microenvironment

Physical activity and the prevention of weight gain decrease breast cancer incidence and improve survival. Unraveling the biological mechanisms underlying these cancer prevention effects is difficult because activity and dietary restriction are often linked. The goal of this study was to determine whether physical activity (PA), preventing weight gain via energy restriction (ER), or the combination was most effective in delaying tumor growth, reducing metastatic progression, and improving survival in the 4T1.2 mammary tumor model. Furthermore, we determined whether any of these interventions prevented the expansion of protumor immunosuppressive cells and altered the tumor microenvironment (TME). Female BALB/c mice (n = 7-20/group) were randomized to sedentary (SED) or PA wheel cages and fed ad libitum (AL) or 90% of control food intake (ER). After 8 weeks on the interventions, mice were inoculated with 5 × 10⁴ 4T1.2^luc cells into the 4th mammary fat pad and continued on their respective intervention. PA+ER significantly delayed primary tumor growth (final tumor volume, 0.193 ± 0.042 vs. 0.369 ± 0.049 cm³, P < 0.001), reduced metastatic burden in the lungs (0.72 ± 0.36 vs. 16.27 ± 6.98, P = 0.054) and increased survival (median survival, 68 vs 40 days, P = 0.043) compared with SED+AL mice. PA+ER also reduced the expression level of metastatic and immunosuppressive genes and resulted in favorable changes in immune cell infiltrates in the tumor. These data suggest that both PA and ER are needed to reduce tumor growth, delay metastatic progression, and improve survival, and that this protection is associated with changes in immune-mediated mechanisms.

Abstract 586: CD4+and CD8+T cells influence 4T1.2luc mammary tumor growth and survival

The 4T1.2 syngeneic murine breast cancer model is an aggressive model of stage IV triple-negative breast cancer. Despite its significant strength, the 4T1.2 model is poorly immunogenic with few defined tumor antigens. The firefly luciferase gene, luc2, has been transfected into various tumor cell lines as a reporter for bioluminescence imaging. However, studies have shown that the luciferase (Luc) may serve as a tumor antigen and induce CD8+ cytotoxic T cell responses. The goal of the current study was to determine if luciferase expression in 4T1.2 tumor cells would enhance the immunogenicity of the tumor, and explore the role of immune effector cells in the parental 4T1.2 and luciferase-transfected 4T1.2luc tumor model. In vitro proliferation of the 4T1.2 and 4T1.2luc cells was assessed using the MTS cell proliferation assay. For in vivo experiments, female BALB/c mice were randomized into 2 groups and orthotopically injected with 5x104 4T1.2 or 4T1.2luc cells, respectively. Tumor growth was assessed until day 35 post tumor implantation. Each group was further randomized into 5 subgroups and received i.p. injections of PBS, rat IgG2b mAb, anti-CD4 mAb, anti-CD8 mAb, or anti-asialo GM1. Mice were sacrificed between day 28-35 post tumor implantation, and lung metastases were analyzed for each group. To further evaluate the immunogenicity of luciferase in the 4T1.2luc model, a separate cohort of mice were orthotopically injected with 5x104 4T1.2luc cells and sacrificed at day 35 post tumor implantation. Splenocytes were harvested and cultured in the presence of 1 or 10 µg/ml peptides representing MHC I-restricted Luc epitopes for 5 days, and cytotoxicity of the effector cells was assessed by the chromium-release assay. In vitro proliferation rates were not significantly different between 4T1.2 and 4T1.2luc tumor cells. However, 4T1.2luc tumor-bearing mice showed a significant reduction in primary tumor growth compared to 4T1.2 tumor-bearing mice. 4T1.2 primary tumor growth was not altered by the depletion of any immune cell type, while 4T1.2luc primary tumor growth was significantly increased by the depletion of CD8+ T cells, and reduced by the depletion of NK cells. Depletion of CD4+ T cells, CD8+ T cells or NK cells in 4T1.2luc tumor-bearing mice resulted in a significant reduction in median survival. Splenocytes from 4T1.2luc tumor bearing mice demonstrated Luc-specific cytotoxicity upon ex vivo restimulation with Luc peptides, and a stronger response was observed when cells were restimulated with 1 µg/ml compared to 10 µg/ml Luc peptides. These findings suggest that luciferase may serve as a tumor antigen in the 4T1.2luc tumor model, and host immune components (CD4+ and CD8+ T cells) may play a role in controlling 4T1.2luc primary tumor growth and survival. The stronger immunogenicity of 4T1.2luc conferred by luciferase will enable future immunotherapeutic research that ultimately may benefit breast cancer patients.

Citation Format: Yitong Xu, Shizhao Duan, William J. Turbitt, Andrea M. Mastro, Connie J. Rogers. CD4+and CD8+T cells influence 4T1.2luc mammary tumor growth and survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 586.

Abstract 509: Acarbose, but not metformin, reduces tumor burden and improves intra-tumoral immune responses in a pre-clinical breast cancer model

Finding ways to enhance T cell infiltration into tumors and boost effector function remains a critical knowledge gap that must be addressed to improve responses to immune-stimulatory therapies. Acarbose and metformin are FDA-approved drugs for the treatment of type two diabetes that display potent anti-hyperglycemic activity. A treatment strategy that decreases intra-tumoral glucose could reduce cancer cell viability and render tumors more susceptible to immunotherapy-mediated clearance. The goal of the current study was to determine if acarbose and/or metformin reduce tumor burdens and promote anti-tumor immunity in a preclinical model of breast cancer. Eight-week-old female C57BL/6 mice were orthotopically injected with EO771-Fluc mammary tumor cells then randomized to control (CTRL), CTRL+acarbose (ACA), CTRL+metformin (MET), or acarbose+metformin (ACA+MET) for four weeks. Compared to CTRL, single-agent ACA reduced primary tumor growth (50% decrease; p&lt;0.001) and spontaneous lung metastases (48% decrease; p=0.035) without altering body weight. No effects of single-agent MET or the combination of ACA+MET on EO771 tumor growth or spontaneous lung metastases were observed. nanoString analysis of whole-tumors revealed increased dendritic cell-, T cell-, T helper 1 cell-, CD8+ T cell-, and exhausted CD8+ T cell-based gene signature scores in ACA compared to CTRL-fed mice. Cellular analysis revealed an ACA-induced increase in the percent of tumor-infiltrating PD-1+CD8+ T cells (p=0.042) and a trend toward decreased tumor-infiltrating myeloid-derived suppressor cells, resulting in improved CD8:MDSC ratios. The beneficial effects of ACA on intra-tumoral immunity, specifically promoting T cell immunity within the tumor microenvironment, illustrate the potential for future combined use of ACA with immunotherapies, such as PD-1 or CTLA-4 blockade.

Citation Format: William J. Turbitt, Rachael M. Orlandella, Justin T. Gibson, Lyse A. Norian. Acarbose, but not metformin, reduces tumor burden and improves intra-tumoral immune responses in a pre-clinical breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 509.

Targeting Glucose Metabolism to Enhance Immunotherapy: Emerging Evidence on Intermittent Fasting and Calorie Restriction Mimetics

There is growing interest in harnessing lifestyle and pharmaceutical interventions to boost immune function, reduce tumor growth, and improve cancer treatment efficacy while reducing treatment toxicity. Interventions targeting glucose metabolism are particularly promising, as they have the potential to directly inhibit tumor cell proliferation. However, because anti-tumor immune effector cells also rely on glycolysis to sustain their clonal expansion and function, it remains unclear whether glucose-modulating therapies will support or hinder anti-tumor immunity. In this perspective, we summarize a growing body of literature that evaluates the effects of intermittent fasting, calorie restriction mimetics, and anti-hyperglycemic agents on anti-tumor immunity and immunotherapy outcomes. Based on the limited data currently available, we contend that additional pre-clinical studies and clinical trials are warranted to address the effects of co-administration of anti-hyperglycemic agents or glucose-lowering lifestyle modifications on anti-tumor immunity and cancer treatment outcomes. We stress that there is currently insufficient evidence to provide recommendations regarding these interventions to cancer patients undergoing immunotherapy. However, if found to be safe and effective in clinical trials, interventions targeting glucose metabolism could act as low-cost combinatorial adjuvants for cancer patients receiving immune checkpoint blockade or other immunotherapies.

Abstract 2240: Diet and exercise-induced weight maintenance, alone and in combination with a whole tumor cell vaccine, delays mammary tumor growth and reduces tumor-infiltrating MDSCs expressing PD-L1 and IDO

Obesity and physical inactivity increase breast cancer risk, while the prevention of weight gain by diet and exercise can be protective. Numerous biological mechanisms are proposed to explain the beneficial effects of weight maintenance, including changes in metabolic, inflammatory and immune mediators. We have previously shown that diet and exercise-induced weight maintenance (WM), in combination with a whole 4T1.2luc tumor cell vaccine (VAX), significantly reduced mammary tumor growth and metastases in the 4T1.2luc murine mammary tumor model. This reduction in growth and metastases occurred concomitantly with an elevation in tumor antigen-induced splenic IFN-γ production and a reduction in the accumulation of splenic myeloid-derived suppressor cells (MDSCs) at day 35 post-tumor implantation. The goal of the current study was to determine if WM+VAX alters the tumor microenvironment at an early stage of tumor growth (day 24 post-tumor implantation) which may contribute to reduced tumor growth and enhanced immune outcomes at day 35 post-tumor implantation. Female BALB/c mice were randomized into sedentary, weight gain (WG) or exercising (access to voluntary running wheel), weight maintenance (WM) groups (n=22-27/group). After 8 weeks on the intervention, all mice were orthotopically injected with 5x104 4T1.2luc cells into the fourth mammary fat pad and continued on their intervention. Once injected, both WG and WM mice were further randomized into vaccination (VAX) or vehicle control (VEH) groups (n=10-15/group) and administered 1x106 irradiated 4T1.2luc cells (VAX) or HBSS (VEH) at day 7, 14 and 21 post-tumor implantation. Mice were sacrificed at day 24 post-tumor implantation and tumor-infiltrating immune cells were isolated for analyses. Both WM+VEH and WM+VAX groups showed a significant reduction in primary tumor growth and splenomegaly compared to both WG groups (p&lt;0.001). Flow cytometric analysis demonstrated that the combination of WM+VAX significantly reduced total tumor-infiltrating MDSCs and MDSCs expressing PD-L1 and indoleamine 2,3-dioxygenase (IDO) compared to WG+VEH (p&lt;0.05). This finding was consistent with a 1.5-4.5 fold decrease in the gene expression level of Pdcd1, Ido1 and Ifng in the total tumor infiltrates. These results suggest that the combination of weight maintenance and the whole tumor cell vaccine may be altering both the number and immunosuppressive capacity of tumor-infiltrating MDSCs. Thus, preventing weight gain through diet and exercise may be an important recommendation in combination with immune-based therapies to enhance efficacy and improve clinical outcomes. This work is supported by R21 CA209144; T32GM108563. W.J.T is currently funded by the NIH T32DK062710 grant; NORC, UAB, Birmngham, AL.

Citation Format: Yitong Xu, William J. Turbitt, Andrea M. Mastro, Connie J. Rogers. Diet and exercise-induced weight maintenance, alone and in combination with a whole tumor cell vaccine, delays mammary tumor growth and reduces tumor-infiltrating MDSCs expressing PD-L1 and IDO [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2240.

Abstract 243: Diet and exercise-induced weight maintenance, alone and in combination with a whole tumor cell vaccine, delays mammary tumor growth and reduces MDSC accumulation

Obesity and physical inactivity increase breast cancer risk, while the prevention of weight gain by diet and exercise can be protective. Numerous biological mechanism(s) have been proposed to explain the beneficial effects of weight maintenance; however few studies have examined the immune response to energy balance. We have previously shown that diet and exercise-induced weight maintenance (WM) achieved via a 10% restriction in calories and access to voluntary running wheels in combination with a whole tumor cell vaccine (VAX) significantly reduced mammary tumor growth and metastases in the 4T1 mammary tumor model. This WM-induced reduction in tumor growth occurred concurrently with an elevation in tumor specific IFN-γ production and a reduction in the number of myeloid-derived suppressor cells (MDSCs). However, because tumor size is positively correlated with immune suppression, the goal of the current study was to investigate if mice in the WM+VAX intervention had enhanced anti-tumor immune responses and/or fewer MDSCs controlling for tumor size. Female BALB/c mice were randomized into weight gain (WG) and WM groups (n=8/group) and had access to voluntary running wheels or standard cages, respectively. WG mice were fed ad libitum while WM mice were energy-restricted by 10% to maintain a stable body weight. After 8 weeks on the intervention, all mice were orthotopically injected with 5x104 4T1.2 cells into the fourth mammary fat pad and continued on their intervention. Once injected, both WG and WM mice were further randomized into vaccination (VAX) and vehicle control (VEH) groups (n=4/gr) and administered 1x106 irradiated 4T1.2 cells (VAX) or HBSS (VEH) at day 7 post-tumor implantation. Primary tumor growth was quantified, and mice were sacrificed when tumor volume reached 0.1-0.2 cm3. WM mice weighed significantly less than WG mice over the course of the study (p&lt;0.001). Mice in both WM+VEH and WM+VAX groups took a significantly longer number of days post tumor implantation to reach a tumor size of 0.1-0.2 cm3 (26.3 ± 3.3 d, p=0.003; 23.8 ± 0.5 d, p=0.039, respectively) compared to the WG+VEH group (18.3 ± 2.5 d). Despite the fact that mice were sacrificed when the tumor volumes were standardized at 0.1-0.2 cm3, the combination of WM+VAX resulted in a significant reduction of splenic MDSC accumulation (p=0.049) and enhanced CD4+ T cell proliferation ex vivo. These results suggest that diet and exercise-induced WM was highly effective in delaying primary mammary tumor growth. The combination of WM and an allogenic whole tumor cell vaccine reduced pro-tumorigenic MDSC accumulation and enhanced effector T cell function. Furthermore, these data suggest that diet and exercise may be changing the tumor microenvironment at an early stage of tumor growth favoring tumor clearance. This work is supported by R21 CA209144; T32AI074551.

Citation Format: Yitong Xu, William J. Turbitt, Andrea M. Mastro, Connie J. Rogers. Diet and exercise-induced weight maintenance, alone and in combination with a whole tumor cell vaccine, delays mammary tumor growth and reduces MDSC accumulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 243. doi:10.1158/1538-7445.AM2017-243

Bioactive growth hormone in older men and women: It's relationship to immune markers and healthspan

OBJECTIVE

The consequences of age-related decline in the somatotropic axis of humans are complex and remain largely unresolved. We tested the hypothesis that hGH measurements of plasma by bioassay vs immunoassay from samples obtained from free-living, elderly individuals would reveal a dichotomy in GH activities that are correlated with the functional status of the donors, i.e. their healthspan.

DESIGN

Forty-one men and women of advanced age (men: N=16, age, 80.5±6.5years; height, 173.1±6.9cm; body mass, 81.8±13.0kg) and (women: N=25, age, 80.7±7.2years; height, 157.7±6.0cm; body mass, 68.8±17kg), were recruited for a cross-sectional study. Participants filled out PROMIS (Patient-Reported Outcomes Measurement Information System, U. S. Department of Health and Human Services) scales, undertook physical performance tests and had fasted blood samples obtained at rest for measurement of hormonal and immunology biomarkers.

RESULTS

When measured by the well-established rat tibial line GH bioassay, one half of the plasma samples (n=20) contained bioassayable GH (bGH), but the other half (n=21) failed to mount increases in tibial plate width above saline injected controls. This difference did not correlate with the age, sex or physical functionality of the plasma donor. It also did not correlate with hGH concentrations measured by immunoassay. In those cases in which bGH was detected, various hierarchical regression models predicted that GHRH, c-peptide, VEGF, NPY, IL-4 and T-regulatory lymphocytes were associated with the difference and predicted bGH.

CONCLUSION

Results from this study suggest that the actions of bGH at the cellular level may be modified by other factors and that this may explain the lack of correlations observed in this study.

Abstract 2877: Exercise, alone and in combination with a whole tumor cell vaccine reduces mammary tumor cell growth and enhances anti-tumor immunity

Regular, moderate exercise (EX) can reduce both the incidence and recurrence of breast cancer (BC), and improve survival. Numerous biological mechanism(s) have been proposed to explain these beneficial clinical effects of EX. However, little work has been done to examine the effect of EX on immunomodulation, i.e. the balance between anti-tumor immunity and the emergence of immunosuppressive cells, in particular myeloid derived suppressor cells (MDSC). We have previously demonstrated that moderate EX significantly enhances antigen-specific CD4+ and CD8+ T cell responses and reduces regulatory T cell function in tumor free-mice. Thus, the goal of the current study was to determine if EX could enhance effector function and reduce immunosuppression in tumor bearing mice, and determine if there were any synergistic effects of EX and the administration of a whole tumor cell vaccine on the aforementioned outcomes. Female Balb/c mice were randomized into EX or sedentary control (SED) groups (n = 14-16/group) and had access to running wheel or standard cages, respectively, for 12 weeks prior to the injection of 5×10^4 lucerifase-transfected 4T1.2 tumor cells into the 4th mammary fat pad. Mice were further randomized into vaccination (n = 6-8/group) or vehicle control (n = 4/group) and administered 1×10^6 irradiated 4T1.2 cells (VAC) or HBSS (VEH) at day 7, 14, 21, and 28 post tumor injection. All mice were fed the AIN-76A diet; however, the EX mice (n = 14) were fed 90% of caloric intake of SED animals to remain in energy balance (prevent weight gain) over the course of the study. Primary tumor growth was quantified, and at sacrifice (day 35) organs were collected to assess the following endpoints: splenic antigen-specific CD8+ effector function and myeloid derived suppressor cell (MDSC) accumulation, and metastatic burden in femurs. EX mice, with or without vaccine, weighed significantly less than SED mice (p&lt;0.001). There was a significant effect of both vaccination and EX on primary tumor growth (F(24,200) = 7.386, p&lt;0.001), splenic IFN-γ production (KW = 11.43, p = 0.010); and the accumulation of MDSC (F(3,28) = 6.486, p = 0.021). However, there was only an EX effect on metastatic burden (p = 0.027). There was a synergistic effect of the combination of vaccine+EX on tumor growth, but no other endpoint. These results demonstrate that exercise alone (i.e. in a prevention model, 12 weeks prior to tumor implantation) is highly effective in reducing primary tumor growth and metastases in an aggressive tumor, and significantly shifted the balance of effector and immunosuppressive factors in the direction of anti-tumor immunity. Furthermore, these results demonstrate that exercise is a viable intervention that may yield significant clinical benefit when used in combination with therapeutic cancer vaccines. This work is supported by internal PSU pilot funds for CJR; T32AI074551-03 for WJT.

Citation Format: William J. Turbitt, Donna Sosnoski, Andrea Mastro, Connie Rogers. Exercise, alone and in combination with a whole tumor cell vaccine reduces mammary tumor cell growth and enhances anti-tumor immunity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2877. doi:10.1158/1538-7445.AM2015-2877

Fish Oil Enhances T Cell Function and Tumor Infiltration and Is Correlated With a Cancer Prevention Effect in HER-2/neu But Not PyMT Transgenic Mice

Few studies have explored the effects of omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation on immune modulation in murine models of mammary carcinogenesis. HER-2/neu and PyMT mice were randomized to 2 dietary interventions: AIN-93G-based diet with 1) 11% of diet (per gram weight) as corn oil (CO) or 2) 10% of diet as menhaden fish oil plus 1% of diet as corn oil (FO). FO significantly reduced the incidence and multiplicity of tumors (P < 0.001) in HER-2/neu, but not PyMT mice. FO-fed mice had significantly larger splenocyte counts than CO-fed mice in both the HER-2/neu and PyMT models; and in both models this was comprised of an increase in most cell types, including Gr-1(+)/CD11b(+) cells. T cells from FO-fed HER-2/neu mice produced significantly more interleukin-2 (P = 0.004) and interferon-γ (P = 0.012) in response to in vitro stimulation with anti-CD3 (0.5 µg/ml). Lastly, FO-fed HER-2/neu mice had significantly more tumor immune infiltrates than CO-fed mice, including NK1.1(+), F4/80(+), and Gr-1(+)/CD11b(+) cells (P ≤ 0.05). Greater Th1 cytokine production and significantly more tumor immune infiltrates in FO-fed Her2/neu mice may account for the cancer prevention effect of fish oil in this model.

Dietary methionine restriction inhibits prostatic intraepithelial neoplasia in TRAMP mice

BACKGROUND

Prostate cancer (PCa) is a major aging-related disease for which little progress has been made in developing preventive strategies. Over the past several years, methionine restriction (MR), the feeding of a diet low in methionine (Met), has been identified as an intervention which significantly extends lifespan and reduces the onset of chronic diseases, including cancer, in laboratory animals. We, therefore, hypothesized that MR may be an effective strategy for inhibiting PCa.

METHODS

Control (0.86% Met) or MR (0.12% Met) diets were fed to 5-week old TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) mice, a well-characterized model for PCa. The mice were sacrificed at 16 weeks of age and prostate and other tissues were harvested for histological and biochemical analyses.

RESULTS

As previously reported, MR was associated with a decrease in body weight which was not associated with lowered food intake. MR led to significant reductions in the development of Prostatic Intraepithelial Neoplasia (PIN) lesions, specifically in the anterior and dorsal lobes of the prostate where the incidence of high-grade PIN was reduced by ∼50% (P < 0.02). The reduction in PIN severity was associated with 46-64% reductions in cell proliferation rates (P < 0.02) and plasma IGF-1 levels (P < 0.0001), which might, in part, explain the effects on carcinogenesis. Additionally, no adverse consequences of MR on immune function were observed in the TRAMP mice.

CONCLUSIONS

Overall, these findings indicate that MR is associated with a reduction in prostate cancer development in the TRAMP model and supports the continued development of MR as a potential PCa prevention strategy.

Abstract 3691: Fish oil increases immune cell infiltration of tumors and reduces the incidence of mammary carcinogenesis in Her2neu mice

The role of omega-3 fatty acids (n-3 FA) in breast cancer prevention is widely studied, however much controversy exists in the field. In numerous preclinical models including the Her2neu transgenic model, consumption of n-3 FA provides a protective effect in mammary carcinogenesis. However, to date few studies have explored the effect of n-3 FA supplementation on immune modulation and if such changes contribute to the cancer prevention effects of n-3 FA. The goal of the current study was to explore the role of fish oil, as the source of n-3 FA, on immune markers and tumor yield in a Her2/neu transgenic model. Her2neu mice were randomized to two dietary interventions: AIN-93G-based diet with 1) 11% of diet (per gram weight) as corn oil (CO) or 2) 10% of diet as menhaden fish oil plus 1% of diet as corn oil (FO) (n=30/gr). FO significantly reduced the incidence and multiplicity of tumors in Her2neu mice (P&lt;0.05). A cohort of mice (n=10/gr) were sacrificed at 4 months just prior to developing focal malignant mammary lesions. No differences in the size or cellularity of the spleen were observed; however flow cytometric analysis revealed that FO mice had a significantly greater number of several cell types (CD3+ T cells, NK1.1+ NK cells, CD11c+ DCs) and a greater number of splenic Gr1+/CD11b+ cells than CO mice (14.3 ± 2.6 X 106 vs. 3.6 ± 1.8 X106, respectively; P&lt;0.05). Gr1+/CD11b+ cells are markers that define myeloid derived suppressor cells (MDSCs) which increase with tumor growth and have immunosuppressive function. However, recent reports have documented a role for MDSCs in immune modulation and the emergence of MDSCs subtypes that have different functional roles. A second cohort of mice (n=10/gr) were sacrificed at 12-15 months when ∼80% of control mice have been shown to develop mammary tumors. FO mice had significantly larger spleens with greater splenocyte counts than CO mice (270.3 ± 69.3 X106 and 198.9 ± 38.7 X 106, respectively; P&lt;0.05), which was comprised of a greater number of most cells types (CD3+, F480+, CD11c+, and NK1.1+ cells) including splenic Gr-1+/CD11b+ MDSCs (13.1 ± 4.6 X 106 and 3.4 ± 1.8 X106, respectively P&lt;0.05). Despite the presence of more Gr1+/CD11b+ cells in the spleens of FO mice, T cells from these mice had significantly greater IL-2 and IFN- γ release in response to in vitro stimulation with anti-CD3 (0.5 μg/ml), suggesting that Gr1+/CD11b+ cells may not be inhibiting T cell function in FO mice. Lastly, FO mice had a greater number of tumor infiltrating immune cells than CO mice, including CD3+, NK1.1+, F480+ and Gr1+/CD11b+ cells (P&lt;0.05). The presence of a greater number of tumor infiltrating immune cells correlates with reduced tumor burden in the FO mice. These data suggest unique immune modulatory effects of FO in tumor-bearing animals. This work is supported by the Susan G. Komen Foundation, Komen Grant KG0681632.

Citation Format: William J. Turbitt, Shawntawnee D. Collins, Haifang Xu, Sharlene Washington, Cesar Aliaga, Karam El-Bayoumy, Andrea Manni, Connie J. Rogers. Fish oil increases immune cell infiltration of tumors and reduces the incidence of mammary carcinogenesis in Her2neu mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3691. doi:10.1158/1538-7445.AM2013-3691