Inflammatory talk: linking obesity, NF-κB, and Aromatase

Dynamic role of the codon 72 p53 single-nucleotide polymorphism in mammary tumorigenesis in a humanized mouse model

Female breast cancer (BrCa) is the most common noncutaneous cancer among women in the United States. Human epidemiological studies reveal that a p53 single-nucleotide polymorphism (SNP) at codon 72, encoding proline (P72) or arginine (R72), is associated with differential risk of several cancers, including BrCa. However, the molecular mechanisms by which these variants affect mammary tumorigenesis remain unresolved. To investigate the effects of this polymorphism on susceptibility to mammary cancer, we used a humanized p53 mouse model, homozygous for either P72 or R72. Our studies revealed that R72 mice had a significantly higher mammary tumor incidence and reduced latency in both DMBA-induced and MMTV-Erbb2/Neu mouse mammary tumor models compared to P72 mice. Analyses showed that susceptible mammary glands from E-R72 (R72 x MMTV-Erbb2/Neu) mice developed a senescence-associated secretory phenotype (SASP) with influx of proinflammatory macrophages, ultimately resulting in chronic, protumorigenic inflammation. Mammary tumors arising in E-R72 mice also had an increased influx of tumor-associated macrophages, contributing to angiogenesis and elevated tumor growth rates. These results demonstrate that the p53 R72 variant increased susceptibility to mammary tumorigenesis through chronic inflammation.

Anxa2 gene silencing attenuates obesity-induced insulin resistance by suppressing the NF-κB signaling pathway

Insulin resistance (IR) continues to pose a major threat to public health due to its role in the pathogenesis of metabolic syndrome and its ever-increasing prevalence on a global scale. The aim of the current study was to investigate the efficacy of Anxa2 in obesity-induced IR through the mediation of the NF-κB signaling pathway. Microarray analysis was performed to screen differentially expressed genes associated with obesity. To verify whether Anxa2 was differentially expressed in IR triggered by obesity, IR mouse models were established in connection with a high-fat diet (HFD). In the mouse IR model, the role of differentially expressed Anxa2 in glycometabolism and IR was subsequently detected. To investigate the effect of Anxa2 on IR and its correlation with inflammation, a palmitic acid (PA)-induced IR cell model was established, with the relationship between Anxa2 and the NF-κB signaling pathway investigated accordingly. Anxa2 was determined to be highly expressed in IR. Silencing Anxa2 was shown to inhibit IR triggered by obesity. When Anxa2 was knocked down, elevated expression of phosphorylated insulin receptor substrate 1 (IRS1), IRS1 and peroxisome proliferator-activated receptor coactivator-1a, and glucose tolerance and insulin sensitivity along with 2-deoxy-d-glucose uptake was detected, whereas decreased expression of suppressor of cytokine signaling 3, IL-6, IL-1β, TNF-α, and p50 was observed. Taken together, the current study ultimately demonstrated that Anxa2 may be a novel drug strategy for IR disruption, indicating that Anxa2 gene silencing is capable of alleviating PA or HFD-induced IR and inflammation through its negative regulatory role in the process of p50 nuclear translocation of the NF-κB signaling pathway.

Beneficial bacteria stimulate host immune cells to counteract dietary and genetic predisposition to mammary cancer in mice

Recent studies suggest health benefits including protection from cancer after eating fermented foods such as probiotic yogurt, though the mechanisms are not well understood. Here we tested mechanistic hypotheses using two different animal models: the first model studied development of mammary cancer when eating a Westernized diet, and the second studied animals with a genetic predilection to breast cancer. For the first model, outbred Swiss mice were fed a Westernized chow putting them at increased risk for development of mammary tumors. In this Westernized diet model, mammary carcinogenesis was inhibited by routine exposure to Lactobacillus reuteri ATCC-PTA-6475 in drinking water. The second model was FVB strain erbB2 (HER2) mutant mice, genetically susceptible to mammary tumors mimicking breast cancers in humans, being fed a regular (non-Westernized) chow diet. We found that oral supplement with these purified lactic acid bacteria alone was sufficient to inhibit features of mammary neoplasia in both models. The protective mechanism was determined to be microbially-triggered CD4+CD25+ lymphocytes. When isolated and transplanted into other subjects, these L. reuteri-stimulated lymphocytes were sufficient to convey transplantable anti-cancer protection in the cell recipient animals. These data demonstrate that host immune responses to environmental microbes significantly impact and inhibit cancer progression in distal tissues such as mammary glands, even in genetically susceptible mice. This leads us to conclude that consuming fermentative microbes such as L. reuteri may offer a tractable public health approach to help counteract the accumulated dietary and genetic carcinogenic events integral in the Westernized diet and lifestyle.

Stearoyl gemcitabine nanoparticles overcome obesity-induced cancer cell resistance to gemcitabine in a mouse postmenopausal breast cancer model

Obesity is associated with increased breast tumor aggressiveness and decreased response to multiple modalities of therapy in postmenopausal women. Delivering cancer chemotherapeutic drugs using nanoparticles has evolved as a promising approach to improve the efficacy of anticancer agents. However, the application of nanoparticles in cancer chemotherapy in the context of obesity has not been studied before. The nucleoside analog gemcitabine is widely used in solid tumor therapy. Previously, we developed a novel stearoyl gemcitabine solid-lipid nanoparticle formulation (GemC18-NPs) and showed that the GemC18-NPs are significantly more effective than gemcitabine in controlling tumor growth in mouse models. In the present study, using ovariectomized diet-induced obese female C57BL/6 mice with orthotopically transplanted MMTV-Wnt-1 mammary tumors as a model of postmenopausal obesity and breast cancer, we discovered that obesity induces tumor cell resistance to gemcitabine. Furthermore, our GemC18-NPs can overcome the obesity-related resistance to gemcitabine chemotherapy. These findings have important clinical implications for cancer chemotherapies involving gemcitabine or other nucleoside analogs in the context of obesity.

Methylseleninic acid is a novel suppressor of aromatase expression

Elevated circulating estrogen levels, as a result of increased peripheral aromatization of androgens by aromatase, have been indicated to underlie the association between obesity and a higher risk of breast cancer in postmenopausal women. Although aromatase inhibitors have been used as a first-line therapy for estrogen receptor-positive breast cancer in postmenopausal women, their potential as breast cancer chemopreventive agents has been limited due to toxicities and high costs. It is therefore imperative to develop new aromatase-inhibiting/suppressing agents with lower toxicities and lower costs for breast cancer chemoprevention, especially in obese postmenopausal women. The expression of the aromatase gene, CYP19, is controlled in a tissue-specific manner by the alternate use of different promoters. In obese postmenopausal women, increased peripheral aromatase is primarily attributed to the activity of the glucocorticoid-stimulated promoter, PI.4, and the cAMP-stimulated promoter, PII. In the present study, we show that methylseleninic acid (MSA), a second-generation selenium compound, can effectively suppress aromatase activation by dexamethasone, a synthetic glucocorticoid, and forskolin, a specific activator of adenylate cyclase. Unlike the action of aromatase inhibitors, MSA suppression of aromatase activation is not mediated via direct inhibition of aromatase enzymatic activity. Rather, it is attributable to a marked downregulation of promoters PI.4- and PII-specific aromatase mRNA expression, and thereby a reduction of aromatase protein. Considering the low-cost and low-toxicity nature of MSA, our findings provide a strong rationale for the further development of MSA as a breast cancer chemopreventive agent for obese postmenopausal women.

Advancements in the use of blood tests for cancer screening in women at high risk for endometrial and breast cancer

Several years ago, it was argued that the identification of serum biomarkers is one of the most promising approaches for the detection of early-stage malignant or even premalignant lesions. In this review, the need to establish better monitoring protocols is described for obese women who are at higher risk for the development of malignancies commonly associated with excess weight; specifically endometrial and postmenopausal breast cancer. These cancers have been chosen for this review article as our aim was to focus on female cancers that have been linked with obesity. Cancer screening is essential in detecting disease in its earliest stage in order to reduce morbidity and mortality; however, effective screening is not available for many cancer types. Even for cancers that have effective screening protocols available, there are barriers to screening in obese individuals, such as reduced mobility and embarrassment. These barriers often delay screening in these vulnerable population groups, leading to detection of the disease at a more advanced stage and ultimately leading to a poorer prognosis. As of today, biomarkers do not replace but augment imaging and other existing screening approaches. Future development of blood- or urine-based biomarkers as a way to screen individuals at high risk for certain cancers may prove to be an excellent method for overcoming the barriers that individuals at high risk are facing today. The overall purpose of this manuscript is to provide an overview of screening techniques and to identified barriers and alternate biomarker-based approaches for improvement of endometrial and breast cancer screening in obese women.

Effect of low-fat diets on plasma levels of NF-κB-regulated inflammatory cytokines and angiogenic factors in men with prostate cancer

Diet, nutritional status, and certain dietary supplements are postulated to influence the development and progression of prostate cancer. Angiogenesis and inflammation are central to tumor growth and progression, but the effect of diet on these processes remains uncertain. We explored changes in 50 plasma cytokines and angiogenic factors (CAF) in 145 men with prostate cancer enrolled in a preoperative, randomized controlled phase II trial with four arms: control (usual diet), low-fat (LF) diet, flaxseed-supplemented (FS) diet, and FS+LS diet. The mean duration of dietary intervention was 30 to 31 days. Among the individual arms, the largest number of significant changes (baseline vs. preoperative follow-up) was observed in the LF arm, with 19 CAFs decreasing and one increasing (P < 0.05). Compared with the control arm, 6 CAFs-including proangiogenic factors (stromal-cell derived-1α) and myeloid factors (granulocyte-colony-stimulating factor, macrophage colony-stimulating factor)-all decreased in the LF arm compared with controls; three and four CAFs changed in the FS and FS+LF arms, respectively. Weight loss occurred in the LF arms and significantly correlated with VEGF decreases (P < 0.001). The CAFs that changed in the LF arm are all known to be regulated by NF-κB, and a pathway analysis identified NF-κB as the most likely regulatory network associated with these changes in the LF arm but not in the FS-containing arms. These results suggest that a LF diet without flaxseed may reduce levels of specific inflammatory CAFs and suggests that the NF-κB pathway may be a mediator of these changes.

Rapamycin partially mimics the anticancer effects of calorie restriction in a murine model of pancreatic cancer

Etiologic factors for pancreatic cancer, the 4th deadliest malignant neoplasm in the United States, include obesity and abnormal glucose metabolism. Calorie restriction (CR) and rapamycin each affect energy metabolism and cell survival pathways via inhibition of mammalian target of rapamycin (mTOR) signaling. By using a Panc02 murine pancreatic cancer cell transplant model in 45 male C57BL/6 mice, we tested the hypothesis that rapamycin mimics the effects of CR on pancreatic tumor growth. A chronic regimen of CR, relative to an ad libitum-fed control diet, produced global metabolic effects such as reduced body weight (20.6 ± 1.6 g vs. 29.3 ± 2.3 g; P < 0.0001), improved glucose responsiveness, and decreased circulating levels of insulin-like growth factor (IGF)-1 (126 ± 8 ng/mL vs. 199 ± 11 ng/mL; P = 0.0006) and leptin (1.14 ± 0.2 ng/mL vs. 5.05 ± 1.2 ng/mL; P = 0.01). In contrast, rapamycin treatment (2.5 mg/kg intraperitoneal every other day, initiated in mice following 20 weeks of ad libitum control diet consumption), relative to control diet, produced no significant change in body weight, IGF-1 or leptin levels, but decreased glucose responsiveness. Pancreatic tumor volume was significantly reduced in the CR group (221 ± 107 mm(3); P < 0.001) and, to a lesser extent, the rapamycin group (374 ± 206 mm(3); P = 0.04) relative to controls (550 ± 147 mm(3)), and this differential inhibition correlated with expression of the proliferation marker Ki-67. Both CR and rapamycin decreased phosphorylation of mTOR, p70/S6K, and S6 ribosomal protein, but only CR decreased phosphorylation of Akt, GSK-3β, extracellular signal regulated kinase/mitogen-activated protein kinase, and STAT3(TYR705). These findings suggest that rapamycin partially mimics the anticancer effects of CR on tumor growth in a murine model of pancreatic cancer.