Intermittent energy restriction inhibits tumor growth and enhances paclitaxel response in a transgenic mouse model of endometrial cancer

Objective

Overweight/obesity is the strongest risk factor for endometrial cancer (EC), and weight management can reduce that risk and improve survival. We aimed to establish the differential abilities of intermittent energy restriction (IER) and low-fat diet (LFD), alone and in combination with paclitaxel, to reverse the procancer effects of high-fat diet (HFD)-induced obesity in a mouse model of EC.

Methods

Lkb1 fl/fl p53 fl/fl mice were fed high-fat diet (HFD) or LFD to generate obese and lean phenotypes, respectively. Obese mice were maintained on HFD or switched to LFD (HFD-LFD) or IER (HFD-IER). Ten weeks after induction of endometrial tumor, mice in each group received paclitaxel or placebo for 4 weeks. Body and tumor weights; tumoral transcriptomic, metabolomic and oxylipin profiles; and serum metabolic hormones and chemocytokines were assessed.

Results

HFD-IER and HFD-LFD, relative to HFD, reduced body weight; reversed obesity-induced alterations in serum insulin, leptin and inflammatory factors; and decreased tumor incidence and mass, often to levels emulating those associated with continuous LFD. Concurrent paclitaxel, versus placebo, enhanced tumor suppression in each group, with greatest benefit in HFD-IER. The diets produced distinct tumoral gene expression and metabolic profiles, with HFD-IER associated with a more favorable (antitumor) metabolic and inflammatory environment.

Conclusion

In Lkb1 fl/fl p53 fl/fl mice, IER is generally more effective than LFD in promoting weight loss, inhibiting obesity-related endometrial tumor growth (particularly in combination with paclitaxel), and reversing detrimental obesity-related metabolic effects. These findings lay the foundation for further investigations of IER as a EC prevention strategy in women with overweight/obesity.

Abstract 3054: Proteomics and microRNA characterization of mammary tumor and adipose tissue-derived EVs and their combined impact on cancer cell metabolism

Background: Obesity increases the risk of triple negative breast cancer (TNBC) and its progression to metastasis, the primary cause of death in women with TNBC. In obesity, dysregulated adipose tissue secretes growth factors and hormones, promoting chronic inflammation. Adipose tissue also secretes extracellular vesicles (EVs), cell-derived nanoparticles (50 - 5000 nm diameter) containing proteins and nucleic acids that interact with and modify local and distant cellular targets. Research from our team and others demonstrated that the enzyme pyruvate carboxylase (PC) is upregulated during obesity. Moreover, PC upregulation correlates strongly with breast cancer progression to lung metastasis. We hypothesize that tumor and adipose-derived EVs from obese versus normoweight mice regulate PC activity promoting metabolic reprogramming and metastasis.

Methods: Female C57BL/6 mice (n=32) were randomized to receive either control diet (CON) or a diet-indued obesity (DIO) regimen for 15 weeks and then orthotopically injected with metMWntlung cells (a murine model of metastatic TNBC). Half of the mice were sacrificed when the tumor volume reached 0.5 cm3, and the other half at 1 cm3. The EVs from mammary tumors and visceral adipose tissue of CON and DIO mice were purified by differential centrifugation in combination with a flotation Iodixanol density gradient. In parallel, serum-EVs were isolated from the same mice. After proper characterization of the purity of EV by western blot, electron microscopy, and nanotracking analysis, the EV proteomics was analyzed by global LC-MS/MS analysis and the microRNA content by small RNA sequencing.

Results: Preliminary proteomic analysis of adipose-EV identified 2,844 proteins, of which 50% were associated with EV according to GOCC name. In adipose-EV, obesity but not tumor size significantly impacted protein composition. In the comparison DIO-0.5 cm3 versus CON-0.5 cm3, 613 proteins were statistically (p-value < 0.05) and biologically significant. In this comparison, 197 proteins were more abundant, and 412 were less abundant in the DIO-05 cm3 relative to CON-0.5 cm3. In addition, we detected the presence of PC in adipose and tumor-EVs. Ongoing analysis will compare the composition of EVs in more detail, determine the presence of PC regulators in EVs, and the metabolic consequences and metastatic effects of the combined action of adipose- and tumor-derived EVs. R01CA232589 to SDH and DT supports this research; an NCI diversity supplement of this grant supports XBM.

Citation Format: Ximena Minerva Bustamante-Marin, Emma J. Grindstaff, Laith A. Rayyan, Dorothy Teegarden, Stephen Hursting. Proteomics and microRNA characterization of mammary tumor and adipose tissue-derived EVs and their combined impact on cancer cell metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3054.

Abstract 2576: Calorie restriction reverses the tumorigenic effects of obesity to a greater extent than bariatric surgery in a murine model of breast cancer

Obesity is an established risk and prognostic factor for multiple breast cancer (BC) subtypes. Epidemiologic studies suggest that weight loss via bariatric surgery results in metabolic reprogramming that reverses systemic aberrations as well as the protumorigenic effects of obesity; however, data on the effects of nonsurgical weight loss interventions in obese women remain inconclusive. We previously established that diet-induced obesity (DIO) increases tumor progression in murine models of basal-like BC. The purpose of this study was to determine if surgical and dietary weight loss interventions could effectively reduce obesity-associated tumor progression. Our first experiment directly compared mammary tumor growth following weight loss in DIO mice. Female C57BL/6 mice were randomized to a low-fat control (CON; 10 kcal% fat) diet or DIO regimen (60 kcal% fat) for 15 weeks. DIO mice were then randomized to either remain on DIO diet (DIO-DIO) or initiate weight loss either via vertical sleeve gastrectomy (DIO-SURG, with concurrent switch to control diet) or switch to control diet without surgery (DIO-DIET). CON mice remained on the 10 kcal% fat diet throughout the study. Eight weeks later, all mice were orthotopically injected with E0771 basal-like mammary tumor cells and were euthanized when tumors from the DIO-DIO group reached 1.5cm3. Body weights were not significantly different between DIO-SURG and DIO-DIET mice but both groups weighed significantly less than DIO-DIO mice. Compared with CON mice, tumor burden was not different in DIO-SURG mice but was significantly greater in DIO-DIET mice, suggesting that surgical weight loss more effectively reverses the protumorigenic effects of obesity than a low-fat diet. We next sought to determine how the anticancer effects of calorie restricted diets compared with bariatric surgery. Another group of female C57BL/6 received DIO diet for 16 weeks, then randomized to the same CON or DIO-SURG interventions as above, or to receive one of two calorie restriction (CR) diets—chronic CR (DIO-CCR; 30% daily calorie reduction) or intermittent CR (DIO-ICR; 14% calorie reduction 5 days per week, 70% calorie reduction on 2 nonconsecutive days per week). At time of tumor collection, DIO-SURG, DIO-CCR, and DIO-ICR mice weighed significantly less than DIO-DIO mice; however, only DIO-CCR and DIO-ICR mice achieved body weights significantly lower than CON mice. Tumor weights were significantly reduced in DIO-CCR and DIO-ICR fed mice, relative to CON mice, while tumor weights of DIO-SURG mice were intermediate. Moreover, multiple linear regression indicated weight loss, irrespective of intervention, was the strongest predictor of tumor mass. Our results in a murine model of basal-like BC suggest that weight loss via CR regimens (CCR, ICR) and, to a lesser extent, bariatric surgery, mitigates the pro-tumorigenic effects of obesity.

Citation Format: Kristina K. Camp, Emily Rossi, Tori L. McFarlane, Steven Doerstling, Subreen Khatib, Elaine Glenny, Michael Coleman, Laura Bowers, Erika Rezeli, Randy J. Seeley, Alfor G. Lewis, Joel Parker, Anthony Fodor, Farnaz Fouladi, Stephen Hursting. Calorie restriction reverses the tumorigenic effects of obesity to a greater extent than bariatric surgery in a murine model of breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2576.

Obesity-Associated Leptin Signaling Promotes Chemotherapy Resistance in Basal-Like Breast Cancer: The Role of Tumor-Associated Macrophages

Objectives

Obesity is associated with a reduced response to cytotoxic chemotherapies. Given that the adipokine leptin has been shown to promote macrophage production of pro-tumor cytokines, we hypothesized that leptin-induced pro-tumor macrophage polarization is a key mediator of obesity-associated docetaxel resistance.

Methods

Wild-type C57BL/6 mice were fed a low-fat control (10% kcal from fat) or high-fat diet-induced obesity (DIO; 60% kcal from fat) diet for 15 weeks, then orthotopically injected with 2 mouse mammary tumor cell lines: EWnt-S (scrambled shRNA) and EWnt-L (shRNA to the leptin receptor) in the 9th and 4th mammary glands, respectively. Mice in each group were then randomized to vehicle or docetaxel (20 mg/kg/week IV for 3 weeks). The transcriptomes of both tumors (n = 6/group) were analyzed by microarray, and cell type enrichment analysis performed using the webtool xCell. The in vitro effects of leptin +/− docetaxel on macrophage polarization as well as cancer cell cytotoxicity and markers of invasive capacity are currently being assessed.

Results

The DIO mice had greater body weight and % body fat at euthanization versus control mice (P < 0.01 for both). Docetaxel treatment in DIO mice reduced tumor growth rate in EWnt-L tumors (P < 0.05), but not EWnt-S tumors. In contrast, docetaxel treatment reduced the EWnt-L and EWnt-S tumor growth rate in control mice (P < 0.05 for both). xCell analysis indicated that docetaxel treatment increased M2 macrophage levels in the DIO mouse tumors, but not the controls. Leptin receptor knockdown attenuated this effect. In addition, key genes related to “macrophage markers”, “cytokines and inflammatory response”, and “interleukin (IL)-6 signaling” were differentially expressed in docetaxel-treated EWnt-S tumors from DIO versus control mice.

Conclusions

These results indicate that leptin signaling mediates obesity-induced docetaxel resistance in the E-Wnt model of basal-like breast cancer. They also suggest that docetaxel interacts with leptin signaling to promote an increase in tumor-promoting M2 macrophages and subsequent docetaxel resistance. This hypothesis is currently being explored through our in vitro studies.

Funding Sources

This work was supported by a grant from the Developmental Funding Program, Lineberger Comprehensive Cancer Center, UNC Chapel Hill.

Dietary β-Hydroxy-β-Methylbutyrate Supplementation Promotes PDAC Response to Gemcitabine and Immunotherapy Response in Obese Mice

Objectives

Late diagnosis, aggressive underlying biology, and limited treatment options contribute towards the exceptionally poor survival of pancreatic ductal adenocarcinoma (PDAC). Obesity promotes both incidence and progression of PDAC via chronic systemic inflammation, generation of an immunosuppressive tumor microenvironment, and promotion of tumor fibrosis. β-Hydroxy-β-Methylbutyrate (HMB) reduces cancer associated cachexia and promotes modest reductions in tumor growth in animal models of cancer. The objective of this study was to determine if HMB supplementation would alter therapeutic response to either gemcitabine or anti-PD1 immunotherapy.

Methods

C57BL/6 mice were fed either a diet induced obesity high fat diet or a matched low fat control. Following PANC02 tumor induction, animals were treated with HMB alone or in combination with gemcitabine or anti-PD1 immunotherapy. Tumor transcriptomic analysis was preformed using Affymetrix microarray, with subsequent gene set enrichment analysis. Immunohistochemistry was performed for CD3 (a T cell marker). C57BL/6 mice were fed either a diet induced obesity high fat diet or a matched low fat control. Following PANC02 tumor induction, animals were treated with HMB alone or in combination with gemcitabine or anti-PD1 immunotherapy. Tumor transcriptomic analysis was preformed using Affymetrix microarray, with subsequent gene set enrichment analysis. Immunohistochemistry was performed for CD3 (a T cell marker).

Results

DIO-induced immune suppression was partially reversed by HMB, with reduced tumor growth, increased T cell markers and enhanced efficacy of gemcitabine following HMB treatment in obese mice. Separately, HMB enhanced the efficacy of anti-PD1 immunotherapy.

Conclusions

HMB enhanced PDAC immune surveillance, augmenting both cytotoxic chemotherapy and immunotherapy. HMB-induced suppression of obesity driven PDAC tumor growth, and promotion of immune surveillance may provide extend the therapeutic index of both chemotherapies and immunotherapies in PDAC.

Funding Sources

This study was supported by a grant from the National Cancer Institute (R35 CA197627) to SDH.

Abstract P1-08-02: Omega-3 fatty acids modulate the ability of obese conditions to induce of a proinflammatory phenotype in fibroblasts

Background: Approximately 40% of American women suffer from obesity, and about 1 in 8 women will be diagnosed with breast cancer during her lifetime. The concurrence of these trends has the potential to be particularly detrimental, as obesity confers a worse prognosis for both pre- and postmenopausal breast cancer patients. While the precise mechanisms by which obesity impacts breast cancer prognosis remain to be discovered, evidence suggests that obesity upregulates components of cancer-associated fibroblast (CAF) and senescent cell secretomes, both causally associated with carcinogenesis. Specifically, obesity has been shown to induce expression of the secretory products prostaglandin E2, high mobility group protein B1, interleukin (IL)-6, IL-1 beta, and matrix metalloproteinase-1, the expression of which can be modulated by omega-3 fatty acid-induced signaling. However, studies have yet to determine whether obesity imparts these proinflammatory phenotypes in any individual cell type in the breast tumor microenvironment as well as whether these phenotypes can be modulated by administration of omega-3 fatty acids. This said, we hypothesize that fatty acids modulate the ability of obese conditions to induce a proinflammatory senescent- or CAF-like fibroblast phenotype and thus impact breast cancer progression. Because fibroblasts constitute 80% of the tumor stromal mass, it is of the utmost importance to study obesity-stimulated changes in this cellular compartment and their effects on tumor progression.

Methods: Fibroblasts were exposed to sera derived from lean or obese women with and without omega-3 fatty acid supplementation and assessed for changes in expression of proinflammatory genes, including IL-1α, IL-6, and IL-8, as well as nuclear localization of p65, a subunit of the NF-kB transcription factor, which transcribes about 75% of genes related to the senescent secretome. Conditioned media (CM) from these fibroblasts were then applied to breast cancer cells to assess measures of cancer cell aggressiveness. Finally, as an ex vivo study, breast tissue samples from lean and obese women and mice were compared for concentration of proinflammatory, senescent fibroblasts by immunohistochemical analyses.

Results: Gene and protein expression analyses demonstrated that obese conditions induced a proinflammatory phenotype in fibroblasts, an effect at least partially modulated by omega-3 fatty acids. These phenotypic changes were not without pathological consequence: CM from obesity-stimulated fibroblasts impacted in vitro measures of breast cancer cell aggressiveness to a greater degree than lean sera-stimulated fibroblasts.

Conclusions: While correlative, these data contribute to the identification of a link between obesity and proinflammatory, senescent phenotypes and will ultimately allow for elucidation of the means by which obese conditions confer a worse prognosis for breast cancer patients. In addition, these findings will contribute to our understanding of crosstalk within the tumor microenvironment and inform our pursuit for the development of novel therapeutic targets.

Citation Format: Brittany Harlow, Albert Davalos, Andrew Brenner, Christopher Jolly, Stefano Tiziani, Stephen Hursting, Linda deGraffenried. Omega-3 fatty acids modulate the ability of obese conditions to induce of a proinflammatory phenotype in fibroblasts [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-08-02.

Differential Response to 1,25-dihydroxyvitamin D in Metastatic and Non-Metastatic Breast Cancer Cell Lines in Hypoxia (P05-006-19)

Objectives

Prevention of metastasis is of utmost importance for increasing survival in breast cancer patients. Oxygen tension is variable throughout tumors, creating regions of hypoxia that have been linked with poor cancer prognosis. Hypoxia increases glycolytic flux via hypoxia-inducible factor-1α (HIF1α), and can therefore alter growth and survival of cancer cells. Our objectives are to (1) characterize changes in metabolism and survival that occur when metastatic and non-metastatic mammary cancer cell lines are cultured in hypoxia, and (2) determine whether 1,25-dihydroxyvitamin D (1,25(OH)2D) reduces overall survival in hypoxia.

Methods

We utilized Wnt oncogene-driven murine mammary cancer cells that are non-metastatic (M-Wnt) or that preferentially metastasize to the lung in vivo (metM-Wntlung). Viability of M-Wnt and metM-Wntlung cells treated with 10 nM 1,25(OH)2D and/or 20 mM 2-deoxyglucose (2DG, an inhibitor of glycolysis) was measured with MTT. Expression of HIF1α protein was determined by Western blotting.

Results

We show that 1,25(OH)2D treatment significantly decreased viability of metastatic metM-Wntlung cells grown in hypoxia by 41%, whereas viability of M-Wnt cells was not significantly impacted by 1,25(OH)2D treatment. Furthermore, treating cells with 2DG significantly decreased viability of both cells lines in hypoxia, with metM-Wntlung cells being more sensitive to 2DG. Interestingly, 1,25(OH)2D treatment partially rescued M-Wnt cells by 22% and metM-Wntlung cells by 24% when treated with 2DG in hypoxia. Finally, we show that M-Wnt cells have 1.9-fold increased expression of HIF1α protein compared to metM-Wntlung cells when grown in hypoxia.

Conclusions

Our results collectively suggest that non-metastatic M-Wnt cells are less sensitive to treatment with 1,25(OH)2D and 2DG in hypoxia than metastatic metM-Wntlungcells. These data may be explained, in part, by elevated expression of HIF1α in M-Wnt cells, which may contribute to their improved survival in hypoxia.

Funding Sources

National Institute of Health and USDA.

The role of miR200c in leptin-mediated triple-negative breast cancer progression to an epithelial-to-mesenchymal transition

e12548

Background: Almost 40% of women with breast cancer are obese at diagnosis. Obesity is associated with a worse prognosis in triple negative breast cancer (TNBC). Preclinical studies have shown that leptin is an important factor associated with TNBC by promoting cancer stem cell (CSC) enrichment and/or epithelial-to-mesenchymal transition (EMT). Transcription factors SNAIL, TWIST and ZEB are critical components in enhancing EMT in cancer cells. The specific mechanism(s) by leptin regulates SNAIL, TWIST and ZEB expression remain unclear, limiting the development of effective interventions to improve outcomes in obese TNBC patients. Recent studies have demonstrated that miR200c, downstream of leptin receptor signaling, regulates the expression of SNAIL1, TWIST and ZEB. We will test the hypothesis that leptin contributes to obesity-induced EMT/CSC in TNBC through modulation of miR200c. Methods: Ob-R (leptin receptor) expression was suppressed in TNBC MDA-MB-231 and E-Wnt cells using shRNA (Ob-R null). Ob-R and Ob-R null cells were exposed to sera pooled from lean or obese women, as well as lean sera supplemented with leptin, after which expression of SNAIL, TWIST, ZEB and miR200c was measured by qPCR, while activation of the JAK-STAT pathway was assessed by Western blotting. Results: TNBC cells exposed to obese and high leptin conditions demonstrated increased expression of EMT markers compared to levels expressed under lean conditions. The Ob-R WT and null cells were used to determine the specific role of leptin signaling in regulating expression of SNAIL, TWIST and ZEB through miR200c. Conclusions: Both obese and high leptin conditions result in increased expression of EMT regulators, suggesting that effective targeting of this pathway may provide clinical benefit in the obese breast cancer patient. Elucidating the specific mediators of this pathway will guide development of novel and more potent medical therapies.

Abstract 5131: Obese conditions induce changes in stromal fibroblast phenotype

Background: Over 40% of American women present a BMI ≥30, which is particularly alarming since obesity confers a worse prognosis for both pre- and postmenopausal breast cancer patients. Although the molecular mechanisms behind this remain unclear, obese conditions have been shown to upregulate certain components of the cancer-associated fibroblast (CAF) secretome and senescence associated secretory phenotype (SASP), both directly correlated with tumorigenesis. However, studies have yet to determine whether obesity induces a cohesive SASP or CAF-like phenotype from any one cell type of the breast tumor microenvironment. Because fibroblasts represent the most common breast tumor cell type, it is of particular importance to investigate obesity-induced changes in this cellular compartment and their effects on cancer cell behavior. Methods: Direct effects of obesity were examined by exposing IMR-90 and HCA2 human fibroblasts to media supplemented with 2% sera from obese women and measuring changes in gene and protein expression, while indirect effects were evaluated by exposing the fibroblasts to conditioned media (CM) from obesity-stimulated MCF-7 and T47D cells and assessing changes in expression of proinflammatory cytokines. Breast cancer cells were also exposed to CM from obesity-stimulated fibroblasts and measured for changes in proliferation, survival, motility, and invasion. Results and Conclusions: Obese conditions induced proinflammatory changes in fibroblasts both directly and indirectly and stimulated changes in the paracrine signaling between fibroblasts and breast cancer cells. These data contribute to the growing evidence implicating obesity in the promotion of breast cancer progression. Additionally, these findings provide a new line of research to develop potential therapeutic targets to improve outcome.

Citation Format: Brittany Harlow, Albert Davalos, Andrew Brenner, Christopher Jolly, Stephen Hursting, Linda deGraffenried. Obese conditions induce changes in stromal fibroblast phenotype [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 5131.

Signals from the Adipose Microenvironment and the Obesity-Cancer Link-A Systematic Review

Obesity and its associated metabolic dysregulation are established risk factors for many cancers. However, the biologic mechanisms underlying this relationship remain incompletely understood. Given the rising rates of both obesity and cancer worldwide, and the challenges for many people to lose excess adipose tissue, a systematic approach to identify potential molecular and metabolic targets is needed to develop effective mechanism-based strategies for the prevention and control of obesity-driven cancer. Epidemiologic, clinical, and preclinical data suggest that within the growth-promoting, proinflammatory microenvironment accompanying obesity, crosstalk between adipose tissue (comprised of adipocytes, macrophages and other cells) and cancer-prone cells may occur via obesity-associated hormones, cytokines, and other mediators that have been linked to increased cancer risk and/or progression. We report here a systematic review on the direct "crosstalk" between adipose tissue and carcinomas in humans. We identified 4,641 articles with n = 20 human clinical studies, which are summarized as: (i) breast (n = 7); (ii) colorectal (n = 4); (iii) esophageal (n = 2); (iv) esophageal/colorectal (n = 1); (v) endometrial (n = 1); (vi) prostate (n = 4); and (vii) ear-nose-throat (ENT) cancer (n = 1). Findings from these clinical studies reinforce preclinical data and suggest organ-dependent crosstalk between adipose tissue and carcinomas via VEGF, IL6, TNFα, and other mechanisms. Moreover, visceral white adipose tissue plays a more central role, as it is more bioenergetically active and is associated with a more procancer secretome than subcutaneous adipose tissue. Efforts to eavesdrop and ultimately interfere with this cancer-enhancing crosstalk may lead to new targets and strategies for decreasing the burden of obesity-related cancers. Cancer Prev Res; 10(9); 494-506. ©2017 AACR.

Tumor-extrinsic discoidin domain receptor 1 promotes mammary tumor growth by regulating adipose stromal interleukin 6 production in mice

Discoidin domain receptor 1 (DDR1) is a collagen receptor that mediates cell communication with the extracellular matrix (ECM). Aberrant expression and activity of DDR1 in tumor cells are known to promote tumor growth. Although elevated DDR1 levels in the stroma of breast tumors are associated with poor patient outcome, a causal role for tumor-extrinsic DDR1 in cancer promotion remains unclear. Here we report that murine mammary tumor cells transplanted to syngeneic recipient mice in which Ddr1 has been knocked out (KO) grow less robustly than in WT mice. We also found that the tumor-associated stroma in Ddr1-KO mice exhibits reduced collagen deposition compared with the WT controls, supporting a role for stromal DDR1 in ECM remodeling of the tumor microenvironment. Furthermore, the stromal-vascular fraction (SVF) of Ddr1 knockout adipose tissue, which contains committed adipose stem/progenitor cells and preadipocytes, was impaired in its ability to stimulate tumor cell migration and invasion. Cytokine array-based screening identified interleukin 6 (IL-6) as a cytokine secreted by the SVF in a DDR1-dependent manner. SVF-produced IL-6 is important for SVF-stimulated tumor cell invasion in vitro, and, using antibody-based neutralization, we show that tumor promotion by IL-6 in vivo requires DDR1. In conclusion, our work demonstrates a previously unrecognized function of DDR1 in promoting tumor growth.

Abstract A26: Body fatness and adipose tissue subtypes are associated with circulating biomarkers of inflammation and angiogenesis in colorectal cancer patients: The ColoCare Study

Background: Adiposity has been linked to both risk and prognosis of colorectal cancer; however, the impact of different compartments of adipose tissue (visceral vs. subcutaneous) is unclear. In healthy individuals, adiposity is associated with elevated biomarkers of inflammation, which provides a mechanistic link between adiposity and cancer risk. For prognosis, the downstream effects of inflammation on angiogenesis may be central. We investigated associations between adiposity and biomarkers of inflammation, as well as angiogenesis, in colorectal cancer patients enrolled in the ColoCare Study, an international multicenter patient cohort.

Methods: We utilized preoperatively obtained serum samples of patients with newly diagnosed colorectal cancer [n=164; (stage I-IV)] from the ColoCare Study in Heidelberg, Germany, with available diagnostic multi-detector-CT images for adipose tissue quantification. Abdominal adipose tissue was assessed by area-based quantification of visceral (VAT), and subcutaneous adipose tissue (SAT), as well as their ratio (VAT/SAT) on levels L3/L4 and L4/L5. Body mass index (BMI) was calculated (kg/m2) and demographic and clinical-surgical data were abstracted from medical records. Circulating CRP, SAA, VEGF-A, VEGF-D, sICAM-1 and sVCAM-1 levels were assessed on the Meso Scale Discoveries platform with V-plex assays at the Huntsman Cancer Institute (average intra-plate CVs 2.9%, inter-plate CVs 7.9%). Partial correlations and regression analyses, adjusting for age, sex and tumor stage were performed.

Results: While overall obesity (BMI) was only significantly associated with sVCAM (r=0.23, p=0.006), visceral adiposity (VAT) was associated with both CRP and SAA (r=0.21, p=0.01 and r=0.17, p=0.04, respectively). There was no association between SAT and the measured biomarkers. Most predictive was the ratio of VAT/SAT on level L3/L4, which was associated with CRP (r=0.18, p=0.04), SAA (r=0.24, p=0.006), sICAM-1 (r=0.18, p=0.04), and particularly VEGF-A (r=0.28, p=0.0008). Similar associations were observed for the VAT/SAT ratio on level L4/5.

Conclusions: We demonstrated a link between specifically visceral adiposity and biomarkers of inflammation in colorectal cancer patients. In addition, we showed that visceral adiposity also affects circulating VEGF-A levels. This protein has various effects, including the induction of angiogenesis, vasculogenesis and endothelial cell growth, as well as the promotion of cell migration, and the inhibition of apoptosis. Our findings support a mechanistic role of visceral adipose tissue in colorectal cancer risk and potentially prognosis.

Citation Format: Cornelia M. Ulrich, Jürgen Böhm, Christy Warby, Tengda Lin, Mariam Salou, Biljana Gigic, Dominique Scherer, Johanna Nattenmueller, Jennifer Ose, Lin Zielske, Petra Schrotz-King, Torsten Kölsch, Erin Siegel, Christopher Li, Alexis Ulrich, Hanno Glimm, Jewel Samadder, Stephen Hursting, Hans-Ulrich Kauczor. Body fatness and adipose tissue subtypes are associated with circulating biomarkers of inflammation and angiogenesis in colorectal cancer patients: The ColoCare Study. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr A26.

Breast Cancer Genetic and Molecular Subtype Impacts Response to Omega-3 Fatty Acid Ethyl Esters

Epidemiological studies have correlated frequent omega-3 (n-3) fatty acid consumption with a lower risk for breast cancer; however, recent prospective studies have been less conclusive. Efforts in the preventive setting have focused on the use of n-3 fatty acids, and the pharmaceutical ethyl esters (EE) of these natural compounds, for high-risk patient populations. Limited understanding of specific mechanisms by which these agents function has hampered identification of the cancer subtype(s) that would gain the greatest therapeutic benefit. In this study, we investigated the in vitro effects of n-3 EEs in four distinct breast cancer subtypes and explored how they affect not only breast cancer cell survival but also modulate the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) and peroxisome proliferator-activated receptor gamma signaling pathways. Similar to the high variance in response observed in human studies, we found that the effectiveness of n-3 EEs depends on the molecular characteristics of the MCF-7, CAMA-1, MDA-MB-231, and SKBR3 breast cancer cell lines and is closely associated with the suppression of NF-κB. These data strongly suggest that the use of n-3 fatty acids and their pharmaceutical ether esters in the prevention and therapeutic setting should be guided by specific tumor characteristics.

Abstract P5-14-01: Docosahexanoic acid's modulation of survival and invasion is associated with altered CCL20/CCR6 chemokine levels and signaling in hyperplastic, DCIS and metastatic breast cancer cell lines

Introduction: High dietary intake of docosahexanoic acid is associated with a lower risk of breast cancer and reduced metastasis. Epidemiological and preclinical studies suggest that the regulation of monocyte recruitment may play an important role in lowering breast cancer risk and decreasing breast cancer metastasis. In addition to promoting the recruitment of pro-inflammatory leukocytes, the CCL20/CCR6 chemokine axis has been implicated in promoting breast cancer cell migration and invasion. We hypothesize that one mechanism by which DHA suppresses breast cancer progression and metastasis is through the suppression of CCL20/CCR6 signaling.

Methods: The 21PT, 21NT and 21MT-1 cell lines have been previously described as reflecting the characteristics of hyperplastic, in situ and metastatic breast cells, respectively. We measured the impact of physiological DHA concentrations on cell survival and cell proliferation using colony formation and MTT assays respectively. Invasion of 21PT, 21NT and 21MT-1 cells were evaluated using invasion chambers. Changes in CCL20 and CCR6 expression were measured using qPCR. The activity and expression levels of JNK, ERK1/2 and c-Jun, downstream modulators of the CCL20/CCR6 axis, were evaluated using Western blot analyses.

Results: Following a 24 hr exposure to 20 uM DHA and 5-7 days of recovery, colony counts of all three cell lines were significantly suppressed, with 21NT cells experiencing the largest percent reduction. Invasion capacity of 21PT, 21NT and 21MT-1 accurately mirrored the stages of breast cancer they represent. Treatment with DHA reduced the invasion capacity of 21MT-1 to the levels of its hyperplastic counterpart. CCL20 mRNA levels were reduced when cells were exposed to DHA for 48 hrs. Western blot analyses suggest that activation of ERK1/2 and JNK signaling may be critical in orchestrating DHA-associated reduction of invasion.

Conclusions: With the support from epidemiological and preclinical studies, the use of omega-3 based preventive regimen may prove useful for reducing breast cancer risk and breast cancer metastasis. In vitro studies using premalignant breast cancer can provide invaluable insights to the molecular mechanisms accountable for preventive properties of omega-3 fatty acids. DHA-associated regulation of CCL20/CCR6 signal transduction may be an important preventive mechanism and future studies will warrant deepened understanding of how nutraceutical compounds can prevent breast cancer.

Citation Format: Ching Hui Chen, Laura Garcia, Carol Fabian, Stephen Hursting, Linda deGraffenried. Docosahexanoic acid's modulation of survival and invasion is associated with altered CCL20/CCR6 chemokine levels and signaling in hyperplastic, DCIS and metastatic breast cancer cell lines [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-14-01.

Abstract A06: Obesity induces a metabolic switch toward aerobic glycolysis in breast cancer cells in vitro and in vivo

Background: The prevalence of obesity is steadily increasing worldwide, impacting the incidence of a variety of diseases, including breast cancer (BCa). Although epidemiological studies show a strong association between elevated body mass index (BMI) and a heightened risk of postmenopausal BCa, the underlying etiology remains relatively unknown. One potential mechanism by which obesity contributes to BCa progression and recurrence is through induction of obesity-induced stress (OBIS). Reactive oxygen species (ROS) are byproducts of metabolism, and excessive production or accumulation of ROS is known to contribute to early tumor initiating events through redox modulation of p53 transcriptional activity.

Objectives: Recent studies indicate that p53 is a key regulator of glycolysis. As the obese state is known to promote aerobic glycolysis, the preferred mode of energy production by most transformed cells, and because approximately 40% of human breast cancers harbor p53 mutations, the aim of this study was to determine the impact of obesity on rates of glucose consumption and genotoxic stress in the context of p53 status.

Results: Using the MMTV-Wnt1 transgenic mouse model of spontaneous breast cancer harboring a heterozygous deletion mutation for p53, we determined the impact of diet-induced obesity (DIO) on markers of aerobic glycolysis and oxidative stress. Interestingly, thioredoxin interacting protein (TXNIP), a regulator of glucose homeostasis, was found to be induced in the normal mammary fat pad (MFP) of obese p53-heterozygous (p53-het) mice versus p53-wild type (p53-wt) MFPs. Conversely, MCF-7 breast cancer cells grown in vitro in serum from these obese mice showed a 50% decrease in TXNIP expression in comparison to cells cultured in serum from the non-obese mice. These findings are consistent with TXNIP's putative role as a tumor suppressor gene. Further, glucose transporter 1 (GLUT-1), a basal glucose transporter required to sustain cellular respiration, was upregulated 5-fold in the MFP of obese p53-het mice compared to MFP taken from non-obese p53-het mice, confirming that obesity regulates glucose uptake in the MFP independently of p53 status. Additionally, the obese p53-het mice displayed elevated serum levels of 8-isoprostane, a biomarker of oxidative stress. Additional in vitro studies demonstrate that MCF-7 cells cultured in serum derived from obese versus non-obese C57BL/6 mice (Ob-serum and non-Ob serum) displayed heightened levels of ROS and significant modulation of HIF-1α, a ROS-inducible transcription factor known to regulate glycolysis. Ob-serum also enhanced lactate dehydrogenase activity and inhibited expression of pyruvate dehydrogenase (PDH), concurrently promoting glycolysis and bypassing oxidative phosphorylation (OXPHOS). This metabolic shift was associated with the accumulation of γ-H2AX foci, a known indicator of DNA double-strand breaks (DSBs). Finally, we observed that a combined shRNA-mediated knockdown of TXNIP and p53 in MCF-7 cells resulted in a dramatic induction of DSBs, and this was exacerbated by exposure to Ob-serum.

Potential Impact: Based on these findings, we conclude that obesity may enhance the rate of metabolic reprogramming in breast cancer cells, resulting in OBIS and accumulation of ROS; thereby promoting disease progression by enhancing genotoxic stress in cells harboring a p53 mutation.

Citation Format: David Antonio Cavazos, Karrie Wheatly, Stephen Hursting. Obesity induces a metabolic switch toward aerobic glycolysis in breast cancer cells in vitro and in vivo. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr A06.

Abstract P4-09-02: Omega-3 ethyl esters suppress breast cancer growth by modulating inflammatory signaling

Introduction: Inflammation has been identified as a key contributor to breast cancer development. Both clinical and preclinical studies confirm a role for inflammatory mediators such as cytokines, interleukins, embedded immune cells and prostaglandins in promoting development of breast cancer. Elevated levels/activity of cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6) are correlated with a more aggressive disease. Omega-3 fatty acid (n-3) intake is correlated with an inverse risk for breast cancer development and improvement in prognostic markers. One key target of omega-3 fatty acids is the COX-2 enzyme. We hypothesize that one mechanism by which omega-3 fatty acids suppress breast cancer progression is through inhibition of inflammatory signaling.

Methods: The impact of omega-3 ethyl esters (n-3 EE), a component of some omega-3 supplements, on the viability of MCF-7 breast cancer cells grown in a pro-inflammatory environment was assessed by MTT analysis and on proliferation by cell counting. Supplementation of the growth media with IL-6 (10ng/mL) was used to simulate a pro-inflammatory environment. Changes in expression levels of key components of inflammatory pathways were assessed by Western blot analyses and quantitative PCR. Prostaglandin E2 (PGE2) levels were measured using ELISA assays.

Results: A significant suppression in IL-6-induced proliferation was observed when cells were exposed to physiological concentrations (20 uM) of n-3 EE for 96 hrs. Molecular analyses suggest that the suppression of the NF-kB/COX-2/PGE2 signaling axis was important for mediating this effect. These results are consistent with other studies using specific COX-2 inhibitors.

Conclusions: With their potent anti-inflammatory activity, n-3 EE may prove useful in reducing malignancy of breast cancer and also slow development of new breast cancers. Importantly, they appear to have none of the toxicities associated with pharmaceutical COX inhibitors (NSAIDs). Future studies are planned to incorporate nutraceutical compounds to standard therapy to improve efficacy and reduce associated side effects.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-09-02.

Abstract 3071: Obesity-associated growth factor signaling upregulates aromatase expression and estrogen receptor activity in breast cancer cells

Obesity increases the risk of breast cancer by approximately 50% in postmenopausal women and is also associated with a worse prognosis. Elevated estrogen synthesis by the local mammary epithelia and adipose tissue is thought to be the principal mediator of breast tumorigenesis in this population, which primarily develops estrogen receptor alpha (ERα) positive breast cancer. However, the elevated levels of free insulin-like growth factor 1 (IGF-1) that accompany obesity are also thought to play a role. IGF-1 has significant tumorigenic effects in the breast and also regulates aromatase, the key enzyme in the conversion of androgens to estrogen. Consequently, we hypothesized that obesity increases the risk of postmenopausal breast cancer via growth factor-induced aromatase expression and/or activity in the local mammary tissue. We have previously shown that MMTV-Wnt-1 mammary tumors from obese ovariectomized mice express higher levels of aromatase in comparison to tumors from lean ovariectomized mice. To examine the molecular pathways responsible for this effect, we have utilized an in vitro model of obesity in which ERα positive MCF-7 breast cancer cells were exposed to human sera obtained from postmenopausal women and pooled by BMI category. Our data indicates that exposure to obese (BMI ≤ 30 kg/m2) human serum stimulates greater aromatase expression in comparison to control (BMI: 18.5-24.9 kg/m2). This is coupled with enhanced ERα activity when exogenous androgen is present, indicating that the increased aromatase expression results in greater estrogen production. Obese human sera also activates MCF-7 cells’ Akt pathway to a greater degree than control, while MCF-7 cells expressing a constitutively active Akt demonstrate higher levels of aromatase expression in comparison to MCF-7 cells. This suggests that circulating growth factors in the obese sera, like IGF-1, may induce elevated aromatase expression via the downstream PI3K/Akt pathway. To expand on our findings, we plan to assess whether treatment with PI3K/Akt pathway inhibitors eliminates the difference in MCF-7 cells’ aromatase expression following exposure to obese versus control sera. We will also examine how inhibition of the PI3K/Akt pathway affects ERα activity in sera-exposed MCF-7 cells. Through elucidation of the signaling pathways responsible for obesity's upregulation of local aromatase expression, we ultimately hope to develop rational and effective chemopreventive and chemotherapeutic regimens for the high-risk obese postmenopausal population.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3071. doi:1538-7445.AM2012-3071

Abstract 5444: In vitro modeling for breast cancer prevention - omega-3 ethyl esters functioning as preventive agents in 21T series models

Over the past few decades, multiple trials have warranted the benefits of using prevention as an effective strategy for lowering breast cancer incidence. The Breast Cancer Prevention Trial (BCPT) and Study of Tamoxifen and Raloxifene (STAR) conducted by National Cancer Institute demonstrated the effectiveness of tamoxifen and raloxifene as preventive agents in reducing diagnoses of invasive breast cancer. Another prevention study the VITAL cohort study demonstrated that omega-3 supplementation reduces breast cancer incidence in postmenopausal women. In vivo studies have produced results that demonstrated a delay in onset of breast cancer in transgenic mice model. However, current in vitro effort did not have a system that closely resembles the linear progression of breast cancer and therefore stalls the molecular investigation of breast cancer prevention. Majority of in vitro preventive studies have been conducted using cancer cell lines that do not represent precancerous status of mammary tissues and do not mirror the observation of delayed onset or reduced incidence in in vivo and clinical trials. A recent report has suggested the use of a new series of mammary cells that represent hyperplasia, ductal carcinoma in situ (DCIS) and invasive carcinoma in nude mice. In this study we propose the use of 21T series breast cancer cells as a model for breast cancer prevention study using omega-3 ethyl esters. Preliminary data using this model has shown that omega-3 ethyl esters derived from Omacor® reduce proliferation only in 21NT (DCIS) and 21MT-1 (Invasive Carcinoma) and not in 21PT cells (hyperplasic). Suppression of proliferation is most optimal in the presence of estrogen. Survival of cells is inhibited in all cell lines and Ki67 index is reduced in the presence of treatments. Targets of omega-3 ethyl esters may include Akt, ER and NF-kB. Current studies are conducted to investigate the effect of omega-3 ethyl esters on these targets.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5444. doi:1538-7445.AM2012-5444

Dietary energy balance modulates prostate cancer progression in Hi-Myc mice

Male Hi-Myc mice were placed on three dietary regimens [30% calorie restriction (CR), overweight control (modified AIN76A with 10 kcal% fat), and a diet-induced obesity regimen (DIO) 60 kcal% fat]. All diet groups had approximately similar incidence of hyperplasia and low-grade prostatic intraepithelial neoplasia in the ventral prostate at 3 and 6 months of age. However, 30% CR significantly reduced the incidence of in situ adenocarcinomas at 3 months compared with the DIO group and at 6 months compared with both the overweight control and DIO groups. Furthermore, the DIO regimen significantly increased the incidence of adenocarcinoma with aggressive stromal invasion, as compared with the overweight control group (96% vs. 65%, respectively; P = 0.02) at the 6-month time point. In addition, at both 3 and 6 months, only in situ carcinomas were observed in mice maintained on the 30% CR diet. Relative to overweight control, DIO increased whereas 30% CR reduced activation of Akt, mTORC1, STAT3, and NFκB (p65) in ventral prostate. DIO also significantly increased (and 30% CR decreased) numbers of T-lymphocytes and macrophages in the ventral prostate compared with overweight control. The mRNA levels for interleukin (IL) 1α, IL1β, IL6, IL7, IL23, IL27, NFκB1 (p50), TNFα, and VEGF family members were significantly increased in the ventral prostate of the DIO group compared with both the overweight control and 30% CR diet groups. Collectively, these findings suggest that enhanced growth factor (Akt/mTORC1 and STAT3) and inflammatory (NFκB and cytokines) signaling may play a role in dietary energy balance effects on prostate cancer progression in Hi-Myc mice.

Abstract 815: Dietary energy balance modulates skin tumor promotion through altered IGF-1R and EGFR crosstalk

Negative energy balance (calorie restriction, CR) inhibits, while positive energy balance enhances tumor promotion using the two-stage skin carcinogenesis model. Biochemical studies have demonstrated that CR reduced, while diet-induced obesity (DIO) increased insulin-like growth factor 1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) activation and downstream signaling (i.e., Akt and mTOR) following TPA treatment. Additional studies performed using the liver IGF-1 deficient (LID) mouse model (i.e., 75% reduction in circulating IGF-1) demonstrated reduced susceptibility to epithelial carcinogenesis and attenuated IGF-1R and EGFR signaling during tumor promotion, similar to CR mice. Taken together, these findings suggest that dietary energy balance, primarily through its effects on levels of circulating IGF-1, modulates epithelial carcinogenesis and tumor promotion through diet-induced changes in IGF-1R and EGFR signaling and receptor crosstalk. To determine the impact of IGF-1 on IGF-1R and EGFR signaling and receptor crosstalk, Western blot analyses, immunoprecipiation and qPCR analyses were performed using C50 cells (a nontumorigenic keratinocyte cell line) stimulated with IGF-1. IGF-1 treatment of serum starved cells induced rapid phosphorylation (within 5 minutes) of the IGF-1R, as well as the EGFR and ErbB2. Additional experiments were conducted to evaluate mechanisms underlying the effects of IGF-1 on EGFR activation. Immunoprecipitation experiments demonstrated that IGF-1 induced an association between the IGF-1R and the EGFR. Furthermore, qPCR analysis demonstrated that IGF-1 induced HB-EGF and amphiregulin mRNA expression. Current experiments are exploring the possibility that IGF-1 treatment also leads to increased ectodomain shedding of membrane bound EGFR ligands. Further studies were conducted to examine the impact of caloric consumption on IGF-1R and EGFR crosstalk in vivo. For these experiments, ICR female mice were maintained on either a 30% CR or 60Kcal% fat (DIO) regimen for 15 weeks, and then treated with a single application of either acetone or 3.4 nmol TPA. CR reduced, while DIO increased the interaction between the IGF-1R and the EGFR in the epidermis of TPA treated mice. Furthermore, CR reduced, while DIO increased mRNA expression of EGFR ligands both in the presence and absence of TPA treatment. Additional experiments are in progress to confirm that IGF-1 levels, per se, are directly responsible for these diet-induced changes in IGF-1R/EGFR receptor crosstalk. Collectively, the current data suggest that IGF-1 levels and the activation status of the IGF-1R modulate IGF-1R and EGFR receptor crosstalk. Furthermore, diet-induced changes in IGF-1R/EGFR receptor crosstalk subsequently modulate downstream signaling to Akt and mTOR, thus contributing, at least in part, to the effect of dietary energy balance on skin tumor promotion.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 815. doi:10.1158/1538-7445.AM2011-815

Abstract 5586: Omega-3 ethyl esters: Differential involvement of NF-kB in suppressing cell viability of genetically diverse breast cancer cell lines

Background: Global incidence of breast cancer suggests a strong relationship between genetics and diet, including omega-3 fatty acid intake. Over the past several years, research from our lab and others has identified NF-kB as a critical target for n-3 mediated anti-cancer effects. Recently, n-3 ethyl esters, derivatives of n-3 fatty acids, have been exploited in pharmaceutical drugs designed to treat chronic diseases but limited data has been generated investigating their potential as chemopreventive agents. This study in conjunction with an ongoing breast cancer chemoprevention trial using n-3 ethyl esters delves into the molecular mechanism of their chemopreventive effects in the four major molecular subtypes of breast cancer to test the hypothesis that n-3 ethyl esters suppress breast cancer viability through NF-kB modulation.

Methods: Eight breast cancer cell lines representing the four molecular subtypes of breast cancer were treated with n-3 ethyl esters at 10, 20 and 40uM for various lengths of time. Biological assays assessing cell survival and proliferation were conducted simultaneously with molecular assays measuring p65 translocation, p65 DNA binding and NF-kB initiated transcription, the chronological events of NF-kB signaling/regulation. Transient shIKBα knockdown were conducted to determine the role NF-kB plays in the context of distinctive breast cancer genetic backgrounds. In addition, toxicity of n-3 ethyl esters in non-cancerous cells were evaluated by subjecting Human Epithelial Mammary Cells (HMEC) and MCF-10A cells to identical treatments.

Results: Preliminary data showed that n-3 ethyl esters suppressed survival of breast cancer cells at all concentrations without impacting cell proliferation. NF-kB function was hindered at two events of p65 signaling: p65 exclusion and blunted NF-kB transcriptional activity. Across the panel of cell lines HER2 overexpressors demonstrated relative resistance to treatments. A 30% knockdown of IKBα did not recover the suppression of n-3 ethyl esters in HER2 overexpressors but fully rescued the reduction of NF-kB transcriptional activity in MDA-MB-231 and MCF-7 cells. p65 DNA binding ability and toxicity assessment of n-3 ethyl esters are currently been evaluated in HMEC and MCF-10A.

Conclusion: N-3 ethyl esters demonstrate anti-cancer properties in all subtypes of breast cancer within which NF-kB plays differential roles. The HER2 overexpressors display relative resistance to n-3 ethyl esters when p65 involvement is assessed and it is hypothesized to be the lack of dependence on NF-kB signaling in this subtype. The in vitro assessment conducted herein may translate to a projected success of chemoprevention for luminal A, B and basal-like but not the prevention of HER2 overexpressing tumors when high-risk patients are subjected to n-3 ethyl ester chemo-preventive regimens.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5586. doi:10.1158/1538-7445.AM2011-5586

Abstract P1-06-01: Omega-3 Fatty Acids for Chemoprevention: NF-Kb as a Molecular Target in Both Pre and Post Menopausal High-Risk Breast Cancer Models

Genetic heterogeneity of human breast cancer has complicated treatment, prevention and therapeutic regimens in both clinical and personal care settings. With the recent advances in genetic analyses, human breast tumors are now segregated into four principle molecular subtypes: luminal A, luminal B, basal and HER2 overexpressors, each differing in their driver mutations, estrogen receptor status and dependence on specific cell signaling pathways to maintain growth and tumorigenicity. Omega-3 fatty acids have been shown in previous studies to be effective in modulating tumor growth in preclinical models of breast cancer, but epidemiological studies have been less clear regarding their efficacy as chemopreventive agents. Like many targeted therapies, we hypothesize that omega-3 fatty acids will be most effective against specific subtypes of disease, and it will be critical to identify these subtypes if these dietary agents are to be exploited most effectively. In this current study, the genetic diversity of breast cancer was represented by appropriate cell lines of matching molecular backgrounds and each class of breast cancer were subjected to exposures of omega-3 fatty ethyl esters derived from Lovaza®, an anti-hypertriglyceride medication that is currently under clinical evaluation as a chemopreventive for breast cancer. Previous studies have suggested that a target for omega-3 fatty acid modulation is the transcription factor NF-kB, a central key mediator of inflammation and cancer cell survival. Coined the single most important molecular machinery required for cancer initiation and promotion, NF-kB has been identified to play critical roles in all stages of breast cancer development. The omega-3 ethyl esters demonstrated suppression of NF-kB transcriptional activity, nuclear localization and overall function with high efficacy in the cell lines reflective of the luminal A, luminal B and basal subtypes, correlating with inhibition of proliferation and overall survival. Interestingly, among the panel of breast cancer subtypes, the aggressive HER2 overexpressing cell lines were resistant to the inhibitory effects of the omega-3 ethyl esters. One of the proposed mechanisms by which NF-kB is regulated is co-localization with IkB. siRNA knockdown assays suggest IkB involvement in the repression of NF-kB function by the omega-3 ethyl esters in the responding cell lines. Results from an ongoing clinical trial with omega-3 ethyl esters will help confirm if specific subtypes of breast cancers will be more effectively prevented using these agents, and whether NF-kB is the target by which they are mediating their anti-cancer effects. These studies are some of the first to use molecular profiles to identify potential responders and non-responders for dietary intervention and may provide better direction for future clinical studies evaluating the efficacy of diet and lifestyle in the preventive setting.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-06-01.

Abstract 1873: Delayed progression to hormone-independent prostate cancer through modulation of mTOR by omega-3 fatty acids

Prostate cancer is the second leading cause of cancer related deaths in men. The primary obstacle in effective treatment of prostate cancer is the progression of the disease from a hormone-dependent to a hormone-independent state. Previous studies indicate that activation of the mammalian Target of Rapamycin (mTOR) signaling pathway may be involved in progression of prostate cancer. Several studies have demonstrated a significant role for mTOR in promoting androgen independence. Recent data indicate that the combination of androgen deprivation with mTOR inhibition provides an additive anti-tumor effect in vivo. mTOR is directly involved in regulating cell survival, growth, proliferation, and differentiation. Many dietary and lifestyle interventions that reduce cancer risk and progression mediate their effects through regulation of mTOR signaling. Epidemiological studies indicate an inverse relation between dietary intake of omega-3 fatty acids and prostate cancer risk. Omega-3 fatty acids have been shown to inhibit prostate cell growth both in vitro and in vivo. Preliminary data from our laboratory demonstrated that treatment of LNCaP prostate cancer cells with omega-3 fatty acids, specifically docosahexaonoic acid (DHA), delayed development of androgen independence in vitro. This delay correlated with a decrease in protein expression of downstream targets of mTOR regulation, including phosphorylated S6, Bcl-2, and cyclin D. We hypothesize that omega-3 fatty acids may prevent prostate cancer progression to a hormone independent phenotype in part through modulation of mTOR. To test this hypothesis, we transiently transfected LNCaP cells to express a constitutively active mTOR. Our results showed that expression of the constitutively active mTOR correlated with a reduction in response to hormone deprivation, resembling that observed in our previously generated hormone refractory LNCaP cell line. When exposed to hormone-ablation conditions, the proliferation rates observed compared to the that of the vector-only control cells were 64% higher in the constitutively active mTOR cells, and 55% higher in the hormone-refractory cell. Ongoing studies are using a stable transfectant of constitutively active mTOR to determine if modulation of mTOR signaling is one mechanism by which the omega-3 fatty acids delay the progression to hormone-independence. These studies suggest that inhibition of mTOR is critical for cellular response to hormone ablation, and that mTOR may be a viable target for delaying progression to a hormone refractory disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1873.

Abstract 943: Obesity, P13k/Akt/mTOR signaling and prostate carcinogenesis in HiMyc mice

Obesity has increased over the last 30 years in the U.S. and is associated with increased mortality rates for various cancers, including prostate cancer. In contrast, calorie restriction (CR) has been shown to act as a potent inhibitor of tumorigenesis. While this association between dietary energy balance and cancer has been clearly established, the mechanisms underlying these effects are poorly understood. To study the role of obesity and dietary fat in prostate cancer, we have used the HiMyc transgenic mouse model, a well-characterized model for the study of prostate carcinogenesis. For the current studies, HiMyc mice at weaning were placed on three dietary regimens [30% CR, 10kcal% fat (AIN76A), 60 kcal% fat], therefore generating lean, overweight and obese phenotypes. Groups of mice were then sacrificed at 3 and 6 months of age and urogenital tracts were removed and embedded in paraffin for histological analyses. In separate groups of mice, ventral prostate (VP) was removed and used to generate protein lysates for Western blot analyses. Histopathologic evaluation revealed a variety of lesions, with the severity of the lesion correlating with caloric intake. All diet groups had approximately similar incidence of hyperplasia and low grade PIN at 3 and 6 months of age. However, the different energy diets primarily affected the progression of premalignant lesions to malignant lesions in the ventral prostate. At 6 months, diet induced obesity (DIO; 60 kcal% fat) significantly increased the incidence of adenocarcinoma with aggressive stromal invasion, as compared to the overweight control group (96% vs. 65% respectively, p=0.0221), while only in situ carcinomas but no invasive adenocarcinomas were observed in mice maintained on the CR diet. Immunohistochemistry was performed on additional sections to evaluate differences in activation or total levels of Akt, mTOR, P-S6 ribosomal, angiogenesis markers and cell cycle markers. DIO increased, while CR reduced activation of signaling through both Akt and mTOR. Similar effects were observed for levels of cyclin D1 and CD31 proteins. Western blot analyses performed on protein lysates from VP of mice maintained on the same dietary regimen for 6 months confirmed these differential effects of dietary energy balance on Akt and mTOR signaling. The observed changes in signaling appeared to be due, at least in part, to changes in signaling through the insulin-like growth factor 1 receptor (IGF-1R) as a result of altered levels of circulating IGF-1. Taken together, these findings suggest that pathways activated by obesity, such as the Akt and mTOR pathways, may be key targets for preventing and controlling obesity-related prostate cancer progression. Supported by grant CA 107588 and MD Anderson Prostate Spore grant CA 140388.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 943.

Abstract 966: Dietary energy balance modulates IGF-1R and EGFR signaling and crosstalk during tumor promotion

Negative energy balance (calorie restriction, CR) inhibits, while positive energy balance enhances tumor promotion during two-stage skin carcinogenesis. Biochemical studies have demonstrated that CR reduced, while diet-induced obesity (DIO) increased activation of the insulin-like growth factor-1 receptor (IGF-1R) and the epidermal growth factor receptor (EGFR), as well as downstream signaling (e.g., Akt and mTOR) during tumor promotion. Additional studies performed using the liver IGF-1 deficient (LID) mouse model demonstrated that a 75% reduction in circulating IGF-1 attenuated growth factor signaling through the IGF-1R and the EGFR similar to mice on CR diets. These findings suggest that dietary energy balance, primarily through its effects on levels of circulating IGF-1, modulates epithelial carcinogenesis and tumor promotion through diet-induced changes in signaling and crosstalk between the IGF-1R and the EGFR, which subsequently alters signaling to downstream effectors. To determine the impact of IGF-1 on IGF-1R and EGFR signaling and crosstalk, Western blot analyses, immunoprecipiation and qPCR analyses were performed on C50 cells (nontumorigenic keratincyte cell line) stimulated with IGF-1. IGF-1 increased activation of the IGF-1R and the EGFR, as well as signaling to downstream effectors (i.e., Akt and mTOR). Immunoprecipitation experiments demonstrated an increase in association between the IGF-1R and the EGFR following IGF-1 stimulation. Furthermore, IGF-1 induced changes in expression levels of the EGFR, as well as EGFR ligands (i.e., HB-EGF, amphiregulin, TGF-α). Additional experiments performed using C50 cells stably transfected with EGFR shRNA or cells pretreated with PD153035 (EGFR inhibitor) demonstrated reduced IGF-1 mediated activation of the EGFR as well as reduced downstream signaling to Akt and mTOR. In vivo studies were performed to evaluate the effect of dietary energy balance on IGF-1R and EGFR crosstalk. For these experiments, ICR mice were maintained on a CR and DIO regimen for 15 weeks, after which they were treated with a single application of 3.4 nmol TPA. CR reduced, while DIO increased the interaction between the IGF-1R and the EGFR in the epidermis of TPA treated mice. Furthermore, dietary energy balance modulated EGFR and EGFR ligand expression levels. Taken together, these data suggest that levels of IGF-1 can modulate signaling through both the IGF-1R and the EGFR. Furthermore, diet-induced changes in IGF-1R/EGFR crosstalk subsequently modulate activation of downstream signaling to Akt and mTOR, thus contributing, at least in part, to the effect of dietary energy balance on skin tumor promotion. Supported by NIH grants CA37111 and CA129409.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 966.

Abstract 5713: Omega-3 fatty acid molecular and cellular modulation of in vitro models of high-risk breast cancer

Omega-3 (n-3) fatty acids, especially the long-chain polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaonoic acid (DHA), have been shown to have potential antitumor effects for a wide range of cancer types, including breast. Multiple and widely diverse mechanisms have been purported through which n-3 fatty acids act as antitumor agents. Due to this wide range of effects, the n-3 fatty acids EPA and DHA in particular have been extrapolated to be possible chemo-preventive agents. Recent epidemiological studies have demonstrated that high intake of n-3 fatty acids from fish is inversely correlated with breast cancer risk. In this current study, we explore the molecular and cellular effects of EPA and DHA in breast cancer cells demonstrating abnormalities similar to those found in high risk patient populations, including MCF-7 cells with stable suppression of PTEN expression, MDA-MB-231 cells that mimic the triple negative phenotype and mouse epithelial cells that are derived from MMTV-erbB2 mouse breast tumors. Loss of PTEN activity has been reported in as much as 50% of all breast cancers. Triple negative disease exhibits an aggressive and early pattern of metastasis, with limited treatment options and a poor prognosis. ErbB2 is overexpressed in 30% of breast tumors and has been associated with a more aggressive and a pro-inflammatory disease. Based upon the highly inflammatory nature of these three cell types, we hypothesized that omega-3 fatty acids would be effective in modulating cellular processes that promote the more aggressive phenotype associated with these abnormalities. We are investigating the effect of EPA and DHA on survival, proliferation and apoptosis of the three modulated cell lines in comparison to less aggressive cell lines, and the molecular changes that correlate with response. Preliminary data suggest that cell proliferation is not modulated by exposure to either EPA or DHA. However, both EPA and DHA effectively suppressed NF-kB transcriptional activity in these cells. These data suggest that one important mechanism by which omega-3 fatty acids may function as anti-tumor and possibly chemo-preventive agents is through regulation of NF-kB-induced inflammation. Studies are currently on-going to evaluate if modulation of NF-kB is critical for mediating the protective effects of omega-3 fatty acids on breast cancer development and progression and if reduction of inflammatory responses will correlate with a less aggressive disease in these cells that closely reflect high risk patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5713.

Abstract 5088: In vitro induction of a more aggressive prostate cancer phenotype by exposure to obese sera

Prostate cancer continues to be the second-leading cause of cancer related deaths for men in the United States. Obesity is a known risk factor for the progression of prostate cancer. Studies have shown an association between obesity and chronic inflammation. Inflammation may contribute to prostate growth by promoting benign prostatic hyperplasia or inducing neoplastic changes. The mechanism(s) by which obesity promotes an aggressive prostate cancer is not fully understood. Investigating these mechanisms has been hampered by the lack of appropriate in vitro and in vivo model systems. Our main hypothesis is that obesity-induced chronic inflammation promotes metastatic prostate cancer through modulation of key signaling pathways, including NF-[[Unable to Display Character: ĸ]]B. Our first objective was to develop an appropriate in vitro model system to recapitulate the molecular events associated with obesity. In this current study, we obtained sera from obese and non-obese mice. Using an adipokine protein array 3 independent profiles were identified in obese mice sera that are consistent with metabolic obesity: metabolic syndrome, pro-metastatic and pro-inflammatory profile. We treated LNCaP prostate cancer cells with sera from obese and non-obese mice to determine physiological responses associated with an aggressive phenotype. We observed obese sera promoting invasion and increasing cell motility while having no effect on proliferation. In addition, obese mouse sera induced an EMT phenotype, evidenced by cytoplasmic dispersion of e-cadherin from cell-cell junctions and an increase in vimentin, which corresponded in greater tumor invasion. This study suggests that we can use an in vitro system to mimic the physiological changes in tumor biology induced by exposure to obese sera to investigate the molecular changes that induce a more aggressive phenotype.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5088.

Conference Report: Seventh Annual AACR International Conference on Frontiers in Cancer Prevention Research

In November, 2008 the AACR held the Seventh Annual Frontiers in Cancer Prevention Research meeting in Washington, DC. At this meeting, a wide range of cutting-edge cancer prevention research was presented. This summary highlights some of the most impactful presentations with a focus on the interaction between inflammation, infections, the immune system, and tumor microenvironment in promoting cancer. Several of these presentations described targeting host-tumor interactions as a means for cancer prevention. As discussed below, this meeting continues to represent all phases of cancer prevention research including epidemiologic studies, behavioral and lifestyle interventions, carcinogenesis research, preclinical studies testing novel preventive interventions, and the results of early- and late-phase cancer prevention trials. Major advances presented at the 2008 meeting included studies showing that immune cells can be either protumorigenic or antitumorigenic, efforts to develop more comprehensive human papillomavirus vaccines to more effectively prevent cervical cancer and other human papillomavirus-related cancers, controversial studies of vitamin D and cancer risk, and studies of single-nucleotide polymorphisms to better assess cancer risk. These and the other presentations at this meeting continue to provide strong support for the concept that cancer will be most effectively controlled by applying modern cancer prevention strategies.

mTOR Inhibition and Diet Induced Obesity in a Mouse Model of Postmenopausal Breast Cancer

Background:Breast cancer is the most common type of noncutaneous cancer among white women. It is more frequently diagnosed after menopause, and the majority of cases are estrogen receptor positive (ER+). Obesity is associated with poor prognosis, increasing risk by 50% in post-menopausal women, and correlates with shorter disease-free and overall survival. Unfortunately, the mechanism underlying the poorer outcomes in obese breast cancer patients is not known. The majority of ER+ tumors present with genomic ER activity; however, nongenomic ER activity can also occur, resulting in interaction with growth factor (GF) receptors.In the obese state nongenomic activity may be especially enhanced, promoting ER and GF signaling crosstalk, breast tumor cell growth and survival. Since Akt/mTOR signaling has been implicated in breast cancer, and obesity (through activation of GF signaling pathways) can activate this pathway, we hypothesized that the enhancement of tumor growth in response to obesity can be offset by mTOR inhibition. To test this we used a mouse model of postmenopausal breast cancer and investigated the effects of obesity (relative to lean and overweight phenotypes) with and without pharmacologic mTOR inhibition by RAD001.Methods:Ovariectomized C57BL/6 mice were randomized to diet regimens that induce either a lean, control (overweight), or a diet-induced obesity (DIO) phenotype. After 17 weeks on the diets, DIO mice were switched to the control diet and acclimated for 3 weeks. To determine diet-induced changes in adiposity, quantitative magnetic resonance (qMR) was performed at wk 18. At wk 21 mice were injected with syngeneic MMTV-Wnt-1 mammary tumor cells in the 4th mammary fat pad. Two weeks after tumor injection, the mice received RAD001 (10 mg/kg) or vehicle by oral gavage twice a week for 6 weeks.Tumor growth was measured weekly.Results:At week 17, mice in the DIO group were significantly heavier (42.8 g) than control (34.5 g) and lean mice (24.6 g) (p <0.001) and % fat was also higher (p<0.001) in DIO (54.5%) when compared to the control (42.2%) and lean (30.7%) groups.Tumor growth was different between the three diet regimens, confirming that dietary modulation directly influences MMTV-Wnt-1 tumor growth in a postmenopausal mouse model of breast cancer. DIO mice displayed significantly enhanced tumor growth (p<0.05) when compared to the control and lean mice. Overall, RAD001 was effective at decreasing tumor growth in all diet groups (p<0.01). However, the relative effect of RAD001 versus placebo was diminished in DIO mice compared to control and lean mice, suggesting obese mice may be partially resistant to RAD001. This resistance was overcome in the DIO mice by increasing the RAD001 dose to 15 mg/kg.Conclusion:Our results confirm that DIO increases tumor growth in the context of postmenopausal breast cancer. In addition, treatment with the mTOR inhibitor RAD001 reversed the mammary tumor enhancing effects of obesity (particularly at the higher dose of RAD001), further supporting mTOR as an important molecular target for breaking the obesity-breast cancer link.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5077.

Effects of obesity on anastrozole response in a mouse model of postmenopausal breast cancer

Abstract #1146

Background: The prevalence of obesity, an established breast cancer risk factor for postmenopausal women, has risen rapidly in the US in recent decades. The majority of postmenopausal breast tumors are estrogen receptor-α positive (ER-α+) and responsive to the mitogenic effects of estrogen. Tamoxifen, a selective estrogen receptor modulator, has been the endocrine agent of choice for the treatment and prevention of ER-α+ breast cancer. Unfortunately, resistance to tamoxifen develops in the majority of cases. Akt activation in breast tumors is associated with poor prognosis and resistance to tamoxifen and other forms of endocrine therapy. Akt activation in the mammary epithelium is also enhanced by obesity, possibly due to elevated growth factor and hormone levels known to activate the PI3K/Akt/mTOR pathway. Aromatase inhibitors, such as anastrozole, are emerging as the treatment of choice for the postmenopausal patient, yet little is known as to how obesity may modulate response to these agents. In this study we examined the effect of obesity on tumor growth response to anastrozole and local tumor aromatase expression. We also assessed the correlation between obesity, Akt activation and tumor growth.
 Methods: To mimic postmenopausal obesity, ovariectomized C57BL/6 mice (n=80) were randomized to a control diet (10 Kcal% fat; ∼10.2 kcal/day) or a diet-induced obesity (DIO) regimen (60 Kcal% fat; ∼14.4 kcal/day). After 14 wk on the diets mice were injected with isogenic MMTV-Wnt-1 mammary tumor cells (5x104 cells/mouse) in the 4th mammary fat pad. After tumors became palpable mice were injected with the AI anastrozole (10 μg/day s.c.) or vehicle control (0.3% hydroxypropylcellulose) for 4 wk. Serum leptin and resistin were measured at the end of the study, RT-PCR and western blot analyses were used to determine aromatase gene expression and total and phosphorylated protein levels in the tumors.
 Results: Mice on the DIO regimens were significantly heavier (39.2 g ±0.7) than controls (29.7 g ±1.23), with significantly higher circulating levels of the obesity-related adipokines leptin and resistin. Tumors from DIO mice, relative to controls, displayed increased aromatase expression. Anastrozole had no effect on food consumption or body weight but intriguingly increased aromatase expression in tumors from both control and DIO mice. Importantly, DIO mice, relative to controls, were much less responsive to the tumor inhibitory effect of anastrozole. Akt protein expression correlated positively with tumor weight, regardless of dietary or hormonal treatment.
 Conclusion: In the context of postmenopausal breast cancer, our results suggest that obese mice compared to controls are less responsive to the effects of anastrozole on tumor growth and that aromatase expression in tumors is higher in obese mice regardless of anastrozole treatment. We also found a strong correlation between Akt activation and tumor growth, irrespective of diet or hormonal treatment.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1146.

Abstract PL05-01: Mechanistic targets for preventing obesity-related cancers

PL05-01

The prevalence of obesity, an established risk factor for many cancers (1), has risen steadily for the past several decades in the US and many other countries (2). Unfortunately, the mechanisms underlying the obesity and cancer connection are not well understood, and new targets and strategies for offsetting the impact of obesity on cancer risk are urgently needed. Several hormones and growth factors have been implicated as potential mediators of the energy metabolism -carcinogenesis relationship. These include insulin-like growth factor-1 (IGF-1), insulin, several adipokines, and inflammatory/ oxidative stress factors. Calorie restriction (CR), the most commonly recommended dietary strategy for preventing or reversing obesity, has been shown to inhibit spontaneous, transplanted and chemically induced tumors in a variety of animal models (3). In contrast, diet-induced obesity enhances tumorigenesis in many of these same models (3-6). We have also shown in a series of transgenic model systems and microarray studies that the insulin and insulin-like growth factor signaling pathways appear central to many of the anti-cancer effects of CR, as well as the pro-cancer effects of obesity (3). Using AZIP/F1 transgenic mice, which lack white adipose tissue but have high levels of insulin, IGF-1 and inflammatory markers, we have reported that elevated IGF-1 and insulin, as well as increased inflammatory factors (which typically accompany obesity), independent of the adipose tissue per se, appear to be the important dietary targets for disrupting the obesity-cancer link (4). In addition, biochemical and molecular analyses of tissues from lean, overweight and obese mice, as well as IGF-1 deficient mice, established that the Akt and mTOR pathways provide an important target for disrupting the obesity-cancer link via dietary energy balance (5,6).

The other side of the energy balance equation is energy expenditure, which includes the energetics of growth, metabolism, thermoregulation and physical activity (the only truly modulatable aspect of energy expenditure). Epidemiologic studies have established that increased physical activity is associated with reduced risk of colorectal cancer and postmenopausal breast cancer (7). In addition, there is limited but encouraging epidemiologic data suggesting that increased physical activity may be associated with reduced risk of several other cancers as well (7). Physical activity also exerts anticancer effects in several of our transgenic models, but apparently through very different mechanisms than CR (7). For example, the protective effects of exercise appear to be dependent on p53 gene dosage and independent of IGF-1, based on studies in Apc min mice and Wnt-1 transgenic mice (7,8). A better understanding of the mechanisms underlying the energy balance-cancer link will facilitate the development of novel prevention and treatment strategies for offsetting the effects of obesity on cancer.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):PL05-01.

Abstract B3: Exercise and calorie restriction differentially regulate energy balance-related cell signaling pathways in a model of post-menopausal obesity

B3

Epidemiological data suggest that induced negative energy balance through calorie restriction (CR) or increased exercise (EX) decreases postmenopausal breast cancer risk associated with obesity. Although the mechanism responsible for the beneficial effects of these anti-obesity strategies is not known, hormone alteration seems to play a critical role. Increased adiposity is associated with alterations in circulating adipokines, such as increased leptin and decreased adiponectin levels. In fact, reports show a positive correlation between leptin levels and breast cancer risk, and a negative association between adiponectin levels and breast-cancer patients. The aim of this study was to compare changes in adipokines and downstream signaling pathways proven to be altered in human breast cancers following either CR or EX in a mouse model of post-menopausal obesity. Ovariectomized female C57BL/6 mice (n=45) were administered a high-fat diet for 8 weeks to induce obesity. At week 9, these diet induced obesity (DIO) mice were randomized into 3 groups (n=15/group): control (AIN-76A diet ad libitum); CR (30% reduction in calories relative to control); EX (control diet + increased physical activity). The EX group was run on a variable speed treadmill for 45 minutes a day, five days a week at a maximum speed of 20 m/min At week 16, mice were euthanized and tissue was collected. At the end of the study, CR mice weighed significantly (p<.01) less than control mice (19.9 ± 0.5 vs. 28.8 ± 0.6 g, respectively) and the EX mice (26.0 ± 0.9). Although the CR mice weighed significantly less than the exercised mice, there was no difference in percent body fat between the groups (38.9 ± 1.7 vs. 33.7 ± 1.4 %, respectively), and both groups had significantly less percent body fat than the sedentary, ad libitum-fed controls (48.1 ± 1.9 %). CR, but not EX, demonstrated improved insulin sensitivity based on a glucose tolerance test compared to controls. Serum leptin levels were significantly reduced in CR and EX mice compared to controls and CR displayed increased serum adiponectin levels compared to exercise. Some of the cell signaling pathways regulated by these hormones, including AMPK, Akt and ERK, converge at mTOR; a molecule involved in coupling energy balance signals to protein translation and cell growth. Interestingly, mammary fat pads of CR, but not EX, displayed significantly higher AMPK phosphorylation and lower Akt phosphorylation relative to controls. Alternatively, mammary fat pads from both CR and EX displayed much lower levels of ERK phosphorylation compared to control. In addition, the key downstream effectors of mTOR activation such as S6 kinase and S6 ribosomal protein displayed decreased activation in both CR and EX compared to control. These data suggest that although EX can act on similar pathways as CR, CR possess a more global effect on cell signaling and therefore may produce a more potent anti-cancer effect.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):B3.

Abstract B144: Obesity-induced impairments in innate and adaptive immune responses are differentially altered by exercise and dietary restriction

B144

Obesity increases the risk of several solid tumors, including breast, prostate, pancreatic, and colon. One of several mechanisms that may contribute to the relationship between obesity and tumor risk is an obesity-induced impairment in immunity. We have previously shown that numerous innate and adaptive immune responses, including NK cell cytotoxicity, antigen-specific CD4+ T cell proliferation, and CD8+ T cell cytotoxicity, are impaired in diet-induced obese (DIO) mice. The current study was designed to determine if the obesity-induced decrements in immunity were reversible with weight loss achieved via the most common obesity interventions used in humans: exercise (EX), energy restriction (ER), or a combination of EX+ER. Female C57BL/6 mice consumed a 60 kcal % fat diet, with 20 kcal % protein and carbohydrate, ad libitum for 15 weeks to induce obesity. After achieving a mean (± SD) body weight of 48.3 ± 1.9 grams, DIO mice were randomized to one of the following intervention groups (n=7-9/group): 1) DIO controls, which continued on 60 kcal % fat diet ad libitum; 2) DIO mice with access to running wheels (DIO+EX); 3) DIO mice placed on an energy-restricted diet consisting of a 30% reduction in kcal from fat (42 kcal % fat diet, with 29 kcal% protein & carbohydrate) (DIO+ER); or 4) DIO mice placed on an ER diet with access to running wheels (DIO+ER+EX). Mice on the aforementioned interventions consumed 20.9 ± 0.6 kcal/d, 20.6 ± 0.3 kcal/d, 15.6 ± 0.4 kcal/d, and 15.4 ±0.3 kcal/d, respectively. Mice were on one of the four interventions for 8 weeks prior to receiving a primary vaccination with a subcutaneous pox virus-based vaccine, followed by 2 booster vaccinations 2 and 4 weeks following the prime. Animals were sacrificed 3 weeks following the last boost, and spleens were collected for assessment of immune function. Following 15 weeks on the interventions, DIO, DIO+EX, DIO+ER, and DIO+ER+EX mice weighed 55.3 ± 1.3 g, 50.2 ± 1.3 g, 39.3 ± 1.7 g, 28.5 ± 0.8 g, respectively. Only mice on the ER diets (DIO+ER and DIO+ER+EX mice) weighed significantly less than the DIO control mice (P<0.05). Despite the lack of significant change in body weight with the exercise intervention alone, EX (either alone or in combination with ER) significantly (P <0.05) enhanced NK cell cytotoxicity, antigen-specific CD4+ T cell proliferation, and CD8+ T cell cytotoxicity in DIO mice, whereas ER alone did not. These findings demonstrate that obesity-induced immune impairments in NK cell and T cell function can be reversed by EX or a combination of ER plus EX, but not ER alone. These results suggest that in obese mice exercise enhances immune function independently of changes in body weight, and that in humans exercise may be an important intervention to couple with energy restriction to reduce body weight and enhance immune responsiveness in obese patients.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):B144.

Abstract 1604: Dietary energy balance modulates multistage epithelial carcinogenesis in mouse skin

Dietary energy balance refers to the balance between caloric intake and energy expenditure. Findings from both epidemiological and experimental studies suggest chronic positive energy balance, which can lead to obesity, heightens the risk of developing multiple cancers, while a negative energy balance state, as induced by calorie restriction (CR), decreases these risks. In the present study, we used the two-stage skin carcinogenesis model to examine the effect of dietary energy balance manipulation on both the promotion and progression stages of skin tumorigenesis. Groups of female ICR mice (n=30) were initiated with 25 nmol DMBA and then placed on one of four dietary treatment regimens: 30% CR, 15% CR, 10Kcal% fat (control), or 60Kcal% fat [diet-induced obesity (DIO) diet]. Following four weeks on diet, mice were then promoted with either acetone or 6.8 nmol TPA twice-weekly for the duration of the study. Chronic CR (30% CR) led to a statistically significant inhibition of papilloma formation in the TPA treated group compared to the other TPA treated diet groups. In contrast, while there was a slightly higher number of papillomas per mouse in the DIO diet group treated with TPA, this was not statistically different from the control and 15% CR groups treated with TPA. This experiment is currently being carried to carcinoma development to determine the impact of dietary energy balance manipulation on the conversion of papillomas to carcinomas in this model of epithelial multistage carcinogenesis. Mechanistic studies have been performed to examine the impact of dietary energy balance manipulation on epidermal cell signaling pathways related to TPA-mediated skin tumor promotion. In this regard, CR reduced whereas DIO increased activation of both epidermal Akt and mTOR (assessed by Western blot analysis of phosphorylated proteins) both in the absence and presence of TPA. Furthermore, activation of both the EGFr and IGF-1R was modulated in a similar manner by the different diets. These results suggest that dietary energy balance may modulate tumor promotion in part through modulation of critical signaling pathways downstream of cell surface receptors such as the EGFr and IGF-1R.

Premenopausal breast cancer and the association between estrogen receptor status, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3) and leptin

640

Background: The IGF pathway and leptin are associated with breast cancer risk in premenopausal women. These proteins are implicated in breast carcinogenesis through their interactions with the estrogen pathway, potentially resulting in specific breast cancer histopathologic subtypes. Methods: Pretreatment serum IGF-I, IGFBP-3 and leptin levels were examined in newly diagnosed premenopausal breast cancer cases to determine whether an association with tumor estrogen receptor status exists. Odds ratios were determined by logistic regression analysis. Likelihood ratio tests for interaction with BMI were conducted. Results: One hundred and eight women were evaluated (mean age 42); 82 were ER positive and 26 were ER negative. 62 were normal weight (BMI<25) and 46 were overweight and obese (BMI≥25). Mean IGF-I, IGFBP-3 and leptin levels did not differ between the ER positive and ER negative tumors. No associations were found between IGF-I, IGFBP-3 or leptin and ER status of tumors overall or by subset analysis in normal weight versus overweight and obese individuals. A suggestion that elevated IGFBP-3 was associated with ER-negative disease did not reach statistical significance. Additionally, normal-weight women with ER-negative disease had higher leptin levels than their normal-weight ER-positive counterparts, although we lacked statistical power to detect an effect of BMI on the association between leptin levels and tumor hormone receptor status. Conclusions: This is the first report examining the IGF pathway and leptin in relation to ER status in premenopausal women with newly diagnosed breast cancer. Our small number of cases suggests a number of intriguing findings that should be evaluated in larger studies. Determining links between ER status and IGFBP-3 and leptin may help better define risk factors and potentially appropriate interventions for ER-negative versus ER-positive breast cancer.

No significant financial relationships to disclose.

Genomic instability and aging-like phenotype in the absence of mammalian SIRT6

The Sir2 histone deacetylase functions as a chromatin silencer to regulate recombination, genomic stability, and aging in budding yeast. Seven mammalian Sir2 homologs have been identified (SIRT1-SIRT7), and it has been speculated that some may have similar functions to Sir2. Here, we demonstrate that SIRT6 is a nuclear, chromatin-associated protein that promotes resistance to DNA damage and suppresses genomic instability in mouse cells, in association with a role in base excision repair (BER). SIRT6-deficient mice are small and at 2-3 weeks of age develop abnormalities that include profound lymphopenia, loss of subcutaneous fat, lordokyphosis, and severe metabolic defects, eventually dying at about 4 weeks. We conclude that one function of SIRT6 is to promote normal DNA repair, and that SIRT6 loss leads to abnormalities in mice that overlap with aging-associated degenerative processes.

Medroxyprogesterone acetate elevation of Nm23-H1 metastasis suppressor expression in hormone receptor-negative breast cancer

BACKGROUND

Reestablishment of metastasis suppressor gene expression may constitute a therapeutic strategy for high-risk breast cancer patients. We previously showed that medroxyprogesterone acetate (MPA), a progestin that has been tested as treatment for advanced breast cancer, elevates expression of the Nm23-H1 metastasis suppressor gene in hormone receptor-negative metastatic human breast carcinoma cell lines in vitro via a glucocorticoid receptor-based mechanism. Here, we tested whether MPA treatment inhibits metastatic colonization of a hormone receptor-negative breast cancer cell line in vivo.

METHODS

We tested the soft-agar colony-forming efficiency of untransfected MDA-MB-231T human breast carcinoma cells and MDA-MB-231T cells transfected with antisense Nm23-H1 in the presence and absence of MPA. Pharmacokinetic studies were used to establish dose and injection schedules that led to MPA serum levels in mice similar to those achievable in humans. For in vivo studies, nude mice were injected intravenously with MDA-MB-231T cells. After 4 weeks, mice were randomized to control or MPA arms. Endpoints included incidence, number, and size of gross pulmonary metastases; Nm23-H1 protein expression in gross metastases; and side effects. All statistical tests were two-sided.

RESULTS

MPA reduced colony formation of MDA-MB-231T cells by 40%-50% but had no effect on colony formation of Nm23-H1 antisense transfectants. Metastases developed in 100% (95% confidence interval [CI] = 78% to 100% and 77% to 100%, respectively) of control mice injected with MDA-MB-231T cells. In two independent experiments, only 73% (95% CI = 45% to 92%) and 64% (95% CI = 35% to 87%) of mice injected with 2 mg of MPA developed metastases. Mice injected with 2 mg of MPA showed reductions in the mean numbers, per mouse, of all metastases and of large (>3 mm) metastases (P = .04 and .013, respectively). Nm23-H1 was expressed at high levels in 43% of pulmonary metastases in MPA-treated mice but only 13% of metastases in untreated mice. Mice receiving at least 1-mg doses of MPA gained more weight than control-treated mice but exhibited no bone density alterations or abnormal mammary fat pad histology.

CONCLUSION

Our preclinical results show that MPA appears to elevate Nm23-H1 metastasis suppressor gene expression, thereby reducing metastatic colonization. The data suggest a new use for an old agent in a molecularly defined subset of breast cancer patients.

Aspects of the rationale for the Women's Health Trial

A 5.5-fold range in breast cancer incidence rates in 21 countries shows strong correlation with national estimates of per capita intake of dietary fat, but not with other caloric sources (proteins and carbohydrates). It is argued that certain breast cancer and hormone factors may contribute little to the explanation of such international variations in incidence of this neoplasm. It is further argued that experimental studies in animals support a specific role for dietary fat in the promotion of mammary tumors, but the effects of calories alone seem to be largely restricted to tumor initiation. Finally, data from international, migrant-population, and analytic epidemiologic investigations are used to motivate the basic relative risk assumption of study designs thus far proposed for the Women's Health Trial, and some continuing motivations for a dietary intervention (low-fat diet) trial are discussed.