Obesity is associated with increased risk and poor prognosis of many types of cancers. Several obesity-related host factors involved in systemic metabolism can influence tumor initiation, progression, and/or response to therapy, and these have been implicated as key contributors to the complex effects of obesity on cancer incidence and outcomes. Such host factors include systemic metabolic regulators including insulin, insulin-like growth factor 1, adipokines, inflammation-related molecules, and steroid hormones, as well as the cellular and structural components of the tumor microenvironment, particularly adipose tissue. These secreted and structural host factors are extrinsic to, and interact with, the intrinsic metabolic characteristics of cancer cells to influence their growth and spread. This review will focus on the interplay of these tumor cell–intrinsic and extrinsic factors in the context of energy balance, with the objective of identifying new intervention targets for preventing obesity-associated cancer.

34Obesity is associated with poor prognosis in triple-negative breast cancer (TNBC). 35Preclinical models of TNBC were used to test the hypothesis that increased leptin 36 signaling drives obesity-associated TNBC development by promoting cancer stem cell

The reversibility of the procancer effects of obesity was interrogated in formerly obese C57BL/6 mice that lost weight via a nonrestricted low-fat diet (LFD) or 3 distinct calorie-restricted (CR) regimens (low-fat CR, Mediterranean-style CR, or intermittent CR). These mice, along with continuously obese mice and lean control mice, were orthotopically injected with E0771 cells, a mouse model of triple-negative breast cancer. Tumor weight, systemic cytokines, and incidence of lung metastases were elevated in the continuously obese and nonrestricted LFD mice relative to the 3 CR groups. Gene expression differed between the obese and all CR groups, but not the nonrestricted LFD group, for numerous tumoral genes associated with epithelial-to-mesenchymal transition as well as several genes in the normal mammary tissue associated with hypoxia, reactive oxygen species production, and p53 signaling. A high degree of concordance existed between differentially expressed mammary tissue genes from obese versus all CR mice and a microarray dataset from overweight/obese women randomized to either no intervention or a CR diet. Assessment of differentially methylated regions in mouse mammary tissues revealed that obesity, relative to the 4 weight loss groups, was associated with significant DNA hypermethylation. However, the anticancer effects of the CR interventions were independent of their ability to reverse obesity-associated mammary epigenetic reprogramming. Taken together, these preclinical data showing that the procancer effects of obesity are reversible by various forms of CR diets strongly support translational exploration of restricted dietary patterns for reducing the burden of obesity-associated cancers. Prevention Relevance: Obesity is an established risk and progression factor for triple-negative breast cancer (TNBC). Given rising global rates of obesity and TNBC, strategies to reduce the burden of obesity-driven TNBC are urgently needed. We report the genomic, epigenetic, and procancer effects of obesity are reversible by various calorie restriction regimens.

BackgroundDespite the growing body of evidence on growth differentiation factor 15 (GDF-15) reference values for patients with existing cardiovascular disease, limited investigation has been dedicated to characterizing the distribution and prognostic impact of GDF-15 in predominantly healthy populations. Furthermore, current cutoff values for GDF-15 fail to account for the well-documented age-dependence of circulating GDF-15.MethodsFrom 810 community-dwelling older adults, we selected a group of apparently healthy participants (n = 268). From this sample, circulating GDF-15 was modeled using the generalized additive models for location scale and shape (GAMLSS) to develop age-dependent centile values. Unadjusted and adjusted Cox proportional hazards models were used to assess the association between the derived GDF-15 reference values (expressed as centiles) and all-cause mortality.ResultsSmoothed centile curves showed increasing GDF-15 with age in the apparently healthy participants. An approximately three-fold difference was observed between the 95th and 5th GDF-15 centiles across ages. In a median 8.0 years of follow-up, 97 all-cause deaths were observed in 806 participants with eligible values. In unadjusted Cox regression analyses, the hazard ratio (95% CI) for all-cause mortality per 25-unit increase in GDF-15 centile was 1.80 (1.48–2.20) and dichotomized at the 95th centile, ≥95th versus <95th, was 3.04 (1.99–4.65). Age-dependent GDF-15 centiles remained a significant predictor of all-cause mortality in all subsequent adjusted models.ConclusionsAge-dependent GDF-15 centile values developed from a population of apparently healthy older adults are independently predictive of all-cause mortality. Therefore, GDF-15 reference values could be a useful tool for risk-stratification in a clinical setting.ClinicalTrials.gov IdentifierNCT01452178.

Adipose tissue dysregulation, a hallmark of obesity, contributes to a chronic state of low-grade inflammation and is associated with increased risk and progression of several breast cancer subtypes, including claudin-low breast tumors. Unfortunately, mechanistic targets for breaking the links between obesity-associated adipose tissue dysfunction, inflammation, and claudin-low breast cancer growth have not been elucidated. Ovariectomized female C57BL/6 mice were randomized (n = 15/group) to receive a control diet, a diet-induced obesity (DIO) diet, or a DIO + resveratrol (0.5% wt/wt) diet. Mice consumed these diets ad libitum throughout study and after 6 weeks were orthotopically injected with M-Wnt murine mammary tumor cells, a model of estrogen receptor (ER)-negative claudin-low breast cancer. Compared with controls, DIO mice displayed adipose dysregulation and metabolic perturbations including increased mammary adipocyte size, cyclooxygenase-2 (COX-2) expression, inflammatory eicosanoid levels, macrophage infiltration, and prevalence of crown-like structures (CLS). DIO mice (relative to controls) also had increased systemic inflammatory cytokines and decreased adipocyte expression of peroxisome proliferator-activated receptor gamma (PPARγ) and other adipogenesis-regulating genes. Supplementing the DIO diet with resveratrol prevented obesity-associated increases in mammary tumor growth, mammary adipocyte hypertrophy, COX-2 expression, macrophage infiltration, CLS prevalence, and serum cytokines. Resveratrol also offset the obesity-associated downregulation of adipocyte PPARγ and other adipogenesis genes in DIO mice. Our findings suggest that resveratrol may inhibit obesity-associated inflammation and claudin-low breast cancer growth by inhibiting adipocyte hypertrophy and associated adipose tissue dysregulation that typically accompanies obesity.