Adiponectin differentially affects gene expression in human mammary epithelial and breast cancer cells

Chemerin Stimulates the Secretory Activity of BME-UV1 Bovine Mammary Epithelial Cells

Adipose tissue is an active endocrine gland, synthesizing and secreting multiple signaling molecules termed adipokines. Following the detection of adipokines and their receptors in the mammary tissue of various species, it is indicated that adipokines play a role in the development of the mammary gland. The aim of the present study was to determine the concentration-dependent influence of three adipokines, leptin, adiponectin, and chemerin, on the viability, apoptosis, and secretory activity of BME-UV1 bovine mammary epithelial cells. The study confirmed that BME-UV1 cells contain the leptin receptor (Ob-R) protein, and express transcripts of adiponectin (ADIPOR1 and ADIPOR2) and chemerin (CMLKR1 and GPR1) receptors. Regardless of the administered dose, none of the three tested adipokines had an effect on the viability of BME-UV1 cells, and the number of apoptotic cells remained unchanged. However, chemerin (100 ng/mL) stimulated BME-UV1 cells to synthesize and secrete αS1-casein, the major protein component of milk. These results indicate that chemerin may be a potent regulator of the bovine mammary epithelial cells' functional differentiation, contributing, along with the major systemic hormones and local growth factors, to the development of the bovine mammary gland.

Interactions Between Adiponectin-Pathway Polymorphisms and Obesity on Postmenopausal Breast Cancer Risk Among African American Women: The WHI SHARe Study

BACKGROUND

A decreased level of serum adiponectin is associated with obesity and an increased risk of breast cancer among postmenopausal women. Yet, the interplay between genetic variants associated with adiponectin phenotype, obesity, and breast cancer risk is unclear in African American (AA) women.

METHODS

We examined 32 single-nucleotide polymorphisms (SNPs) previously identified in genome-wide association and replication studies of serum adiponectin levels using data from 7,991 AA postmenopausal women in the Women's Health Initiative SNP Health Association Resource.

RESULTS

Stratifying by obesity status, we identified 18 adiponectin-related SNPs that were associated with breast cancer risk. Among women with BMI ≥ 30 kg/m2, the minor TT genotype of FER rs10447248 had an elevated breast cancer risk. Interaction was observed between obesity and the CT genotype of ADIPOQ rs6773957 on the additive scale for breast cancer risk (relative excess risk due to interaction, 0.62; 95% CI, 0.32-0.92). The joint effect of BMI ≥ 30 kg/m2 and the TC genotype of OR8S1 rs11168618 was larger than the sum of the independent effects on breast cancer risk.

CONCLUSIONS

We demonstrated that obesity plays a significant role as an effect modifier in an increased effect of the SNPs on breast cancer risk using one of the most extensive data on postmenopausal AA women.

IMPACT

The results suggest the potential use of adiponectin genetic variants as obesity-associated biomarkers for informing AA women who are at greater risk for breast cancer and also for promoting behavioral interventions, such as weight control, to those with risk genotypes.

Adipokine Leptin Co-operates With Mechanosensitive Ca2 +-Channels and Triggers Actomyosin-Mediated Motility of Breast Epithelial Cells

In postmenopausal women, a major risk factor for the development of breast cancer is obesity. In particular, the adipose tissue-derived adipokine leptin has been strongly linked to tumor cell proliferation, migration, and metastasis, but the underlying mechanisms remain unclear. Here we show that treatment of normal mammary epithelial cells with leptin induces EMT-like features characterized by higher cellular migration speeds, loss of structural ordering of 3D-mammo spheres, and enhancement of epithelial traction forces. Mechanistically, leptin triggers the phosphorylation of myosin light chain kinase-2 (MLC-2) through the interdependent activity of leptin receptor and Ca2+ channels. These data provide evidence that leptin-activated leptin receptors, in co-operation with mechanosensitive Ca2+ channels, play a role in the development of breast carcinomas through the regulation of actomyosin dynamics.

Novel insights into adiponectin action in breast cancer: Evidence of its mechanistic effects mediated by ERα expression

This review describes the multifaceted effects of adiponectin on breast cancer cell signalling, tumour metabolism, and microenvironment. It is largely documented that low adiponectin levels are associated with an increased risk of breast cancer. However, it needs to be still clarified what are the extents of the decrease of local/intra-tumoural adiponectin concentrations, which promote breast tumour malignancy. Most of the anti-proliferative and pro-apoptotic effects induced by adiponectin have been obtained in breast cancer cells not expressing estrogen receptor alpha (ERα). Here, we will highlight recent findings demonstrating the mechanistic effects through which adiponectin is able to fuel genomic and non-genomic estrogen signalling, inhibiting LKB1/AMPK/mTOR/S6K pathway and switching energy balance. Therefore, it emerges that the reduced adiponectin levels in patients with obesity work to sustain tumour growth and progression in ERα-positive breast cancer cells. All this may contribute to remove the misleading paradigm that adiponectin univocally inhibits breast cancer cell growth and progression independently on ERα status. The latter concept, here clearly provided by pre-clinical studies, may have translational relevance adopting adiponectin as a potential therapeutic tool. Indeed, the interfering role of ERα on adiponectin action addresses how a separate assessment of adiponectin treatment needs to be considered in novel therapeutic strategies for ERα-positive and ERα-negative breast cancer.

Interfering Role of ERα on Adiponectin Action in Breast Cancer

Obesity is characterized by an excess of adipose tissue, due to adipocyte hypertrophy and hyperplasia. Adipose tissue is an endocrine organ producing many bioactive molecules, called adipokines. During obesity, dysfunctional adipocytes alter adipokine secretion, contributing to pathophysiology of obesity-associated diseases, including metabolic syndrome, type 2-diabetes, cardiovascular diseases and many types of malignancies. Circulating adiponectin levels are inversely correlated with BMI, thus adiponectin concentrations are lower in obese than normal-weight subjects. Many clinical investigations highlight that low adiponectin levels represent a serious risk factor in breast carcinogenesis, and are associated with the development of more aggressive phenotype. A large-scale meta-analysis suggests that BMI was positively associated with breast cancer mortality in women with ERα-positive disease, regardless menopausal status. This suggests the importance of estrogen signaling contribution in breast tumorigenesis of obese patients. It has been largely demonstrated that adiponectin exerts a protective role in ERα-negative cells, promoting anti-proliferative and pro-apoptotic effects, while controversial data have been reported in ERα-positive cells. Indeed, emerging data provide evidences that adiponectin in obese patients behave as growth factor in ERα-positive breast cancer cells. This addresses how ERα signaling interference may enhance the potential inhibitory threshold of adiponectin in ERα-positive cells. Thus, we may reasonably speculate that the relatively low adiponectin concentrations could be still not adequate to elicit, in ERα-positive breast cancer cells, the same inhibitory effects observed in ERα-negative cells. In the present review we will focus on the molecular mechanisms through which adiponectin affects breast cancer cell behavior in relationship to ERα expression.

Inhibition of ubiquitin-specific protease 2 causes accumulation of reactive oxygen species, mitochondria dysfunction, and intracellular ATP decrement in C2C12 myoblasts

Ubiquitin-specific protease 2 (USP2) is considered to participate in the differentiation of myoblasts to myotubes, however, its functions in myoblasts under growth conditions remain elusive. In this study, we analyzed the physiological roles of USP2 in myoblasts using Usp2 knockout (KO) C2C12 cells as well as a USP2 specific inhibitor. In addition to the disruption of differentiation, clustered regularly interspaced short palindromic repeats/Cas9-generated Usp2KO cells exhibited inhibition of proliferation compared to parental C2C12 cells. Usp2KO cells reduced the accumulation of intracellular adenosine triphosphate (ATP) content and oxygen consumption. Moreover, Usp2KO cells had fragmented mitochondria, suggesting that mitochondrial respiration was inactive. The deficiency of Usp2 did not affect the enzymatic activities of respiratory chain complexes I, III, IV, and V. However, mitochondrial membrane permeability-evaluated using calcein AM-cobalt staining-was increased in Usp2KO cells. The membrane potential of Usp2KO cells was clearly decreased. Usp2KO cells accumulated reactive oxygen species (ROS) in the mitochondria. The USP2-selective inhibitor ML364 also increased the levels of mitochondrial ROS, and modulated the membrane potential and morphology of the mitochondria. These effects were followed by a decrement in the intracellular content of ATP. Based on these findings, we speculate that USP2 may be involved in maintaining the integrity of the mitochondrial membrane. This process ensures the supply of ATP in myoblasts, presumably leading to proliferation and differentiation.

Adipokines as therapeutic targets in breast cancer treatment

INTRODUCTION

Adipocytes, which represent a substantial part of the tumor microenvironment in breast cancer, secrete several adipokines that affect tumorigenesis, cancer progression, metastasis, and treatment resistance via multiple signaling pathways. Areas covered: In this review, we focus on the role of leptin, adiponectin, autotaxin, and interleukin-6 in breast cancer initiation, progression, metastasis, and drug response. Furthermore, we investigated adipokines as potential targets of breast cancer-specific drugs. Expert opinion: Adipokines and adipokine receptors are deregulated in breast cancer. Adipokines play various roles in breast cancer initiation, progression, metastasis, and drug response, hence, adipokine signaling could be an effective drug target. Several clinical trials are in progress to test the efficacy of adipokine targeting agents. However, adipokines also affect metabolic homeostasis; hence, the adverse effects of the targeted drug should be investigated and addressed.

Adiponectin as a Potential Therapeutic Target for Prostate Cancer

Adipokines are bioactive proteins that mediate proliferation, metabolism, inflammation, and angiogenesis. Adiponectin is an important adipokine that exerts multiple key functions via its anti-metabolic syndrome and anti-inflammatory properties. A number of adiponectin receptors, AdipoR1, AdipoR2 and T-cadherin, have been identified. Recent studies have suggested the involvement of adiponectin and receptors in several cancers, including prostate, breast, endometrial, brain, and colon cancer. Altered levels of adiponectin expression, or its interacting receptors, in cancers can lead to dysregulation of signaling pathways. Our current review describes the molecular mechanisms underlying the anti-tumorigenesis activity of adiponectin and the role of its receptors in prostate carcinogenesis, and provides perspectives of adiponectin-mediated signaling as a potential target for therapy.

Expression of AdipoR1 and AdipoR2 Receptors as Leptin-Breast Cancer Regulation Mechanisms

The development of breast cancer is influenced by the adipose tissue through the proteins leptin and adiponectin. However, there is little research concerning AdipoR1 and AdipoR2 receptors and the influence of leptin over them. The objective of this work was to analyze the expression of AdipoR1 and AdipoR2, modulated by differential concentrations of leptin in an obesity model (10 ng/mL, 100 ng/mL, and 1000 ng/mL) associated with breast cancer in MCF-7 and HCC1937 cell lines. Each cell line was characterized through immunohistochemistry, and the expression of AdipoR1 and AdipoR2 was analyzed by PCR in real time using TaqMan® probes. Leptin induced an increase in cell population of MCF-7 (23.8%, 10 ng/mL, 48 h) and HCC1937 (17.24%, 1000 ng/mL, 72 h). In MCF-7, the expression of AdipoR1 decreased (3.81%, 1000 ng/mL) and the expression of AdipoR2 increased by 13.74 times (10 ng/mL) with regard to the control. In HCC1937, the expression of AdipoR1 decreased by 86.28% (10 ng/mL), as well as the expression of AdipoR2 (50.3%, 100 ng/mL). In regard to the results obtained, it could be concluded that leptin has an effect over the expression of AdipoR1 and AdipoR2 mRNA.

Effect of reduced dietary fat on estradiol, adiponectin, and IGF-1 levels in postmenopausal women with breast cancer

Introduction

In recent years, epidemiological studies have strongly related obesity with an increased risk of developing postmenopausal breast cancer. The aromatization of fatty tissue increases the levels of estradiol and adiponectin, which is correlated with the body mass index (BMI). It is of interest to investigate the effect of reducing BMI on estradiol, adiponectin, and IGF-1, as reducing BMI could be a new strategy to limit the risk of recurrence during the adjuvant treatment of breast cancer.

Objective

The aim of this study is to investigate the effect of reduced dietary fat on the levels of serum estradiol, adiponectin, and IGF-1 among postmenopausal Mexican women with breast cancer.

Methods

In this controlled clinical trial, 100 female patients were randomly divided into two groups and followed for six months. Group 1 (n = 50) was subjected to reduced dietary fat, whereas Group 2 (n = 50) was subjected to a control diet. The levels of serum estradiol and testosterone were determined using an enzyme-linked immunosorbent assay, whereas the concentrations of adiponectin and IGF-1 were determined using a radioimmunoassay.

Results

The patients subjected to reduced dietary fat showed a significant difference in BMI (27.93 ± 4.45 vs 26.05 ± 2.65; p = 0.01) and waist circumference (99.92 vs 91.59 cm; p = 0.0001) after the treatment. Moreover, a significant decrease in serum estradiol was observed (21.23 ± 14.32 vs 16.05 ± 10.25 ng/mL; p < 0.001). The adiponectin concentration also decreased significantly (47.53 ± 12.19 vs 42.52 ± 12.34 µg/mL; p = 0.004), while IGF-1 and testosterone did not show significant changes (p > 0.05). In addition, BMI had a relationship with serum adiponectin (r = −0.27; p = 0.02) and estradiol (r = 0.37; p = 0.001).

Conclusion

The current study shows that reducing BMI decreases serum estradiol and adiponectin. Large clinical trials are needed to investigate the role of adiponectin in breast cancer development in obese women.

Macrophage ubiquitin-specific protease 2 modifies insulin sensitivity in obese mice

We previously reported that ubiquitin-specific protease (USP) 2 in macrophages down-regulates genes associated with metabolic diseases, suggesting a putative anti-diabetic role for USP2 in macrophages. In this study, we evaluate this role at both cellular and individual levels. Isolated macrophages forcibly expressing Usp2a, a longer splicing variant of USP2, failed to modulate the insulin sensitivity of 3T3-L1 adipocytes. Similarly, macrophage-selective overexpression of Usp2a in mice (Usp2a transgenic mice) had a negligible effect on insulin sensitivity relative to wild type littermates following a three-month high-fat diet. However, Usp2a transgenic mice exhibited fewer M1 macrophages in their mesenteric adipose tissue. Following a six-month high-fat diet, Usp2a transgenic mice exhibited a retarded progression of insulin resistance in their skeletal muscle and liver, and an improvement in insulin sensitivity at an individual level. Although conditioned media from Usp2a-overexpressing macrophages did not directly affect the insulin sensitivity of C2C12 myotubes compared to media from control macrophages, they did increase the insulin sensitivity of C2C12 cells after subsequent conditioning with 3T3-L1 cells. These results indicate that macrophage USP2A hampers obesity-elicited insulin resistance via an adipocyte-dependent mechanism.

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USP2A controls macrophage population in mesenteric adipose tissue during obesity.

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Overexpression of USP2A in macrophages retards progression of insulin resistance.

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Overexpression of USP2A in macrophages represses high-fat diet-induced obesity.

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Macrophage USP2A controls insulin sensitivity of muscle dependent on adipocytes.

Globular adiponectin enhances invasion in human breast cancer cells

Every year, a large number of women succumb to metastatic breast cancer due to a lack of curative approaches for this disease. Adiponectin (AdipoQ) is the most abundant of the adipocyte-secreted adipokines. In recent years, there has been an interest in the use of AdipoQ and AdipoQ receptor agonists as therapeutic agents for the treatment of breast cancer. However, while multiple epidemiological studies have previously indicated that low levels of circulating plasma AdipoQ portend poor prognosis in patients with breast cancer, recent studies have reported that elevated expression levels of AdipoQ in breast tissue are correlated with advanced stages of the disease. Thus, the aim of the present study was to clarify the mechanism by which AdipoQ in breast tissue acts directly on tumor cells to regulate the early steps of breast cancer metastasis. In the present study, the effects of different AdipoQ isoforms on the metastatic potential of human breast cancer cells were investigated. The results revealed that globular adiponectin (gAd) promoted invasive cell morphology and significantly increased the migration and invasion abilities of breast cancer cells, whereas full-length adiponectin (fAd) had no effect on these cells. Additionally, gAd, but not fAd, increased the expression levels of microtubule-associated protein 1 light chain 3 beta (LC3B)-II and intracellular LC3B puncta, which are indicators of autophagosome formation, thus suggesting autophagic induction by gAd. Furthermore, the inhibition of autophagic function by autophagy-related protein 7 knockdown attenuated the gAd-induced increase in invasiveness in breast cancer cells. Therefore, the results of the present study suggested that a specific AdipoQ isoform may enhance breast cancer invasion, possibly via autophagic induction. Understanding the roles of the different AdipoQ isoforms as microenvironmental regulatory molecules may aid the development of effective AdipoQ-based treatments for breast cancer.

Cross-Talk between Adiponectin and IGF-IR in Breast Cancer

Obesity is a chronic and multifactorial disorder that is reaching epidemic proportions. It is characterized by an enlarged mass of adipose tissue caused by a combination of size increase of preexisting adipocytes (hypertrophy) and de novo adipocyte differentiation (hyperplasia). Obesity is related to many metabolic disorders like hypertension, type 2 diabetes, metabolic syndrome, and cardiovascular disease, and it is associated with an increased risk of cancer development in different tissues including breast. Adipose tissue is now regarded as not just a storage reservoir for excess energy, but rather as an endocrine organ, secreting a large number of bioactive molecules called adipokines. Among these, adiponectin represents the most abundant adipose tissue-excreted protein, which exhibits insulin sensitizing, anti-inflammatory, and antiatherogenic properties. The serum concentrations of adiponectin are inversely correlated with body mass index. Recently, low levels of plasma adiponectin have been associated with an increased risk for obesity-related cancers and development of more aggressive phenotype, concomitantly with alterations in the bioavailability of insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) signaling pathways. In this review, we discuss the cross-talk between adiponectin/AdipoR1 and IGF-I/IGF-IR in breast cancer.

Adiponectin receptor signaling on dendritic cells blunts antitumor immunity

Immune escape is a fundamental trait of cancer. Dendritic cells (DC) that interact with T cells represent a crucial site for the development of tolerance to tumor antigens, but there remains incomplete knowledge about how DC-tolerizing signals evolve during tumorigenesis. In this study, we show that DCs isolated from patients with metastatic or locally advanced breast cancer express high levels of the adiponectin receptors AdipoR1 and AdipoR2, which are sufficient to blunt antitumor immunity. Mechanistic investigations of ligand-receptor interactions on DCs revealed novel signaling pathways for each receptor. AdipoR1 stimulated IL10 production by activating the AMPK and MAPKp38 pathways, whereas AdipoR2 modified inflammatory processes by activating the COX-2 and PPARγ pathways. Stimulation of these pathways was sufficient to block activation of NF-κB in DC, thereby attenuating their ability to stimulate antigen-specific T-cell responses. Together, our findings reveal novel insights into how DC-tolerizing signals evolve in cancer to promote immune escape. Furthermore, by defining a critical role for adiponectin signaling in this process, our work suggests new and broadly applicable strategies for immunometabolic therapy in patients with cancer.

Estradiol affects extracellular leptin:adiponectin ratio in human breast tissue in vivo

CONTEXT

Exposure to sex steroids is associated with increased breast cancer risk, and adipokines, leptin and adiponectin have been implicated in cancer progression. However, it is not known whether sex steroids affect adipokine secretion in breast tissue.

OBJECTIVE

To elucidate the role of estrogen and tamoxifen on adipokine release in normal human breast tissue and breast cancer.

SETTING AND DESIGN

Microdialysis sampling was used to collect extracellular in vivo leptin and adiponectin from normal human breast tissue in premenopausal healthy volunteers during the menstrual cycle and in postmenopausal women before tamoxifen treatment and after 6 weeks of treatment. In women with breast cancer, microdialysis was performed intratumorally before surgery. In addition, whole normal breast tissue biopsies were cultured ex vivo, and murine breast cancer models were evaluated.

RESULTS

In normal breast tissue, plasma estradiol negatively correlated with local extracellular adiponectin levels (r = -0.34; P < .05) and positively correlated with leptin (r = 0.37; P < .05) and leptin:adiponectin ratio (r = 0.38; P < .05). In postmenopausal women, tamoxifen treatment increased adiponectin (P < 0.05) and decreased leptin (P < .01) and the leptin:adiponectin ratio (P < .01). These in vivo results were confirmed in breast tissue biopsies cultured ex vivo. In patients with breast cancer, extracellular leptin was higher (P < .01) and adiponectin lower (P < .05) in tumors than in normal adjacent breast tissue. In a murine model of breast cancer, estrogen exposure increased leptin secretion (P < .05).

CONCLUSIONS

Estrogen exposure may have a critical role in the regulation of adipokines in human breast tissue and may serve as therapeutic targets for treatment and prevention.

Association between chemotherapy and plasma adipokines in patients with colorectal cancer

BACKGROUND

A link between chemotherapy, the serum level of selected adipokines and clinical outcome in colorectal patients was investigated.

METHODS

Leptin, adiponectin, resistin, visfatin and insulin were measured by ELISA in colorectal cancer patients before and 3 months after the administration of cancer therapy. From August 2012 to August 2013, 34 patients with pathologically documented advanced colorectal cancer (T3/T4 with metastases or nodal status up to N3) and measurable metastatic disease, who required palliative chemotherapy based on the combination of 5-fluorouracil, oxaliplatin and irinotecan, were prospectively recruited in this study. Patients previously underwent curative surgical tumour resection, but the disease was disseminated (metastases in the liver and/or lungs) at the time of admission to the hospital.

RESULTS

Of the 34 patients in this study, 5 accomplished a chemotherapy course with partial response (PR), 23 with SD (stabilisation) and 6 with progression (PD). For further study, only patients with good prognostic outcomes (i.e., PR and SD patients) were included. The mean level of leptin before chemotherapy was 26.39 ± 9.53 ng/ml. After six courses of cancer treatment, the leptin level increased by 118-57.44 ± 27.72 ng/ml (p<0.001). Additionally, the adiponectin level increased considerably (47%) from 9.89 ± 3.96 ng/ml to 14.51 ± 7.79 ng/ml (p<0.001). In contrast to leptin and adiponectin, the resistin and visfatin levels decreased significantly from 7.24 ± 1.17 and 1.98 ± 0.44 to 6.36 ± 1.36 and 1.48 ± 0.34 ng/ml (p<0.001), respectively. Insulin also declined remarkably from 16.20 ± 1.96 to 12.87 ± 1.80 (p<0.001). There were no significant differences the between male and female patients regarding age, BMI, and leptin, adiponectin, resistin, visfatin and insulin serum levels.

CONCLUSIONS

The results of the present study are relevant because we found that chemotherapy in colorectal cancer patients, in addition to its beneficial clinical impact on the course of disease, positively affects cytokine production and release (increases the anti-inflammatory adiponectin and decreases visfatin and resistin, which are proangiogenic and promote cancer cell proliferation). The restoration of adequate adipose tissue function is essential for patients to achieve a good survival prognosis.

Linking adiponectin and autophagy in the regulation of breast cancer metastasis

Adipokines within the tumor microenvironment may play important roles in regulating the early steps of breast cancer metastasis. Adiponectin (AdipoQ) is the most abundant adipokine and exists in multiple forms: full-length multimers (fAd) and a cleaved, globular isoform (gAd). While these isoforms are observed as having distinct biological properties, nearly all investigation into AdipoQ in breast cancer has focused on the antitumor roles of fAd, while mostly ignoring gAd. However, evidence from other disease settings suggests that gAd is linked to processes known to promote metastasis. Here, we discuss key areas in which knowledge about AdipoQ in breast cancer is lacking, expressly focusing on data suggesting that gAd is elevated in the microenvironment and may act directly on invasive breast cancer cells to support their initial metastatic progression. We discuss autophagy as a potential mechanism of action for this effect. Overall, given that AdipoQ and AdipoQ receptor agonists have been proposed as therapeutic strategies, it is necessary to better understand the various functions of these regulatory molecules in metastatic breast cancer. Doing so will help ensure the most effective approaches to treating this disease, for which there remain no curative options.

Evidences that estrogen receptor α interferes with adiponectin effects on breast cancer cell growth

Adiponectin, the most abundant protein secreted by adipose tissue, exhibits insulin-sensitizing, anti-inflammatory, antiatherogenic, and antiproliferative properties. In addition, it appears to play an important role also in the development and progression of several obesity-related malignancies, including breast cancer.   Here, we demonstrated that adiponectin induces a dichotomic effect on breast cancer growth. Indeed, it stimulates growth in ERα+ MCF-7 cells while inhibiting proliferation of ERα- MDA-MB-231 cells. Notably, only in MCF-7 cells adiponectin exposure exerts a rapid activation of MAPK phosphorylation, which is markedly reduced when knockdown of the ERα gene occurred. In addition, adiponectin induces rapid IGF-IR phosphorylation in MCF-7 cells, and the use of ERα siRNA prevents this effect. Moreover, MAPK activation induced by adiponectin was reversed by IGF-IR siRNA. Coimmunoprecipitation studies show the existence of a multiprotein complex involving AdipoR1, APPL1, ERα, IGF-IR, and c-Src that is responsible for MAPK signaling activation in ERα+ positive breast cancer cells. It is well known that in addition to the rapid effects through non-genomic mechanisms, ERα also mediates nuclear genomic actions. In this concern, we demonstrated that adiponectin is able to transactivate ERα in MCF-7 cells. We showed the classical features of ERα transactivation: nuclear localization, downregulation of mRNA and protein levels, and upregulation of estrogen-dependent genes. Thus, our study clarifies the molecular mechanism through which adiponectin modulates breast cancer cell growth, providing evidences on the cell-type dependency of adiponectin action in relationship to ERα status.

Obesity-related markers and breast cancer in CPS-II Nutrition Cohort

Low circulating levels of adiponectin and high levels of insulin-like growth factor-1 (IGF-1), C-reactive protein (CRP), and C-peptide have been shown to be related to postmenopausal breast cancer risk, and to partially mediate the obesity-postmenopausal breast cancer association; however, data from prospective studies, especially those limited to non-users of postmenopausal hormones, are sparse. To further evaluate these associations, we measured these markers in a case-control study nested in the Cancer Prevention Study-II (CPS-II) Nutrition Cohort. Plasma samples from 302 postmenopausal breast cancer cases and matched controls were analyzed. None of the women were taking postmenopausal hormones at blood draw. Multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression models. Low levels of total adiponectin and high levels of total IGF-1 and CRP were associated with increased breast cancer risk, but associations were not statistically significant. The association with C-peptide was statistically significant (T3 vs. T1: OR=1.63, 95% CI 1.08-2.45; p-value for linear trend=0.001), but was slightly attenuated after further adjustment for BMI (T3 vs. T1: OR=1.51, 95% CI 0.99-2.31; p-value for linear trend=0.004). The association between BMI and breast cancer risk was attenuated toward the null after controlling for C-peptide (from OR=1.43 to OR=1.25 for BMI ≥30 kg/m(2) compared to <25 kg/m>(2)). The elevated risk of postmenopausal breast cancer associated with higher circulating levels of C-peptide is consistent with a role of hyperinsulinemia in breast carcinogenesis, and might account for some of the higher risk associated with obesity.

Ubiquitin-specific protease 2-69 in macrophages potentially modulates metainflammation

Macrophages play a critical role in chronic inflammation and metabolic diseases. We identified a longer splice variant of ubiquitin specific protease (USP) 2-69 as a novel molecule that modulates pathways implicated in metabolic disorders. Expression levels of aP2/FABP4 and PAI-1/SERPINE1 genes were increased by 4- and 1.8-fold, respectively, after short hairpin RNA-mediated knockdown (KD) of the USP2 gene, and such expression was alleviated by overexpression of USP2-69 in human myeloid cell lines. Supernatants derived from USP2-KD cells induced IL6 (∼6-fold) and SAA3 (∼15-fold) in 3T3-L1 adipocytes to suggest the anti-inflammatory properties of USP2. In addition, we observed a 30% decrease in the number of macrophages in mesenteric adipose tissue derived from USP2-69 transgenic mice fed a high-fat diet for 14 wk compared with that in their C57BL/6 littermates (P<0.01), which was consistent with a ∼40% decrease in transcription of aP2 and PAI-1. The aP2 locus exhibited elevated chromatin accessibility (>2.1-fold), methylation of histone H3 lysine 4 (>4.5-fold), and acetylation of histone H4 (>2.5-fold) in USP2-KD cells. Transfection of isopeptidase-mutated USP2-69 did not alter chromatin conformation on the aP2 locus in USP2-KD cells. Our results suggest that USP2-69 suppresses meta-inflammatory molecules involved in the development of type-2 diabetes.

Serum adiponectin level and different kinds of cancer: a review of recent evidence

Background. Adiponectin, an adipokine secreted from adipose tissue, has antiobesity, anti-insulin resistance, and anticancer roles. The present study aimed to review the epidemiologic evidence about the association between adiponectin and cancers. Method. We searched in PubMed from 2002 to October 2011 by using the following key words: cancer, malignancy, cell proliferation, and adiponectin. Finally, 45 articles were recruited to review in the present paper. Findings. Several findings suggested inverse association between concentration of hormone and breast cancer risk. Low levels of adiponectin increase the risk of endometrial cancer in women. Adiponectin levels were significantly associated with prostate cancer in men. It seems that there is an inverse relationship between levels of adiponectin or its gene and colorectal cancer. Significant association between hormone and pancreatic cancer was found. Conclusion. Several findings suggested the negative correlation between adiponectin and risk of cancers. This relationship was more elucidated by the correlation between the hormone with obesity and insulin resistance. Suppression of growth and proliferation of cancer cells by adiponectin were explained via several mechanisms.

The role of adiponectin in cancer: a review of current evidence

Excess body weight is associated not only with an increased risk of type 2 diabetes and cardiovascular disease (CVD) but also with various types of malignancies. Adiponectin, the most abundant protein secreted by adipose tissue, exhibits insulin-sensitizing, antiinflammatory, antiatherogenic, proapoptotic, and antiproliferative properties. Circulating adiponectin levels, which are determined predominantly by genetic factors, diet, physical activity, and abdominal adiposity, are decreased in patients with diabetes, CVD, and several obesity-associated cancers. Also, adiponectin levels are inversely associated with the risk of developing diabetes, CVD, and several malignancies later in life. Many cancer cell lines express adiponectin receptors, and adiponectin in vitro limits cell proliferation and induces apoptosis. Recent in vitro studies demonstrate the antiangiogenic and tumor growth-limiting properties of adiponectin. Studies in both animals and humans have investigated adiponectin and adiponectin receptor regulation and expression in several cancers. Current evidence supports a role of adiponectin as a novel risk factor and potential diagnostic and prognostic biomarker in cancer. In addition, either adiponectin per se or medications that increase adiponectin levels or up-regulate signaling pathways downstream of adiponectin may prove to be useful anticancer agents. This review presents the role of adiponectin in carcinogenesis and cancer progression and examines the pathophysiological mechanisms that underlie the association between adiponectin and malignancy in the context of a dysfunctional adipose tissue in obesity. Understanding of these mechanisms may be important for the development of preventive and therapeutic strategies against obesity-associated malignancies.

USP2a protein deubiquitinates and stabilizes the circadian protein CRY1 in response to inflammatory signals

The mammalian circadian clock coordinates various physiological activities with environmental cues to achieve optimal adaptation. The clock manifests oscillations of key clock proteins, which are under dynamic control at multiple post-translational levels. As a major post-translational regulator, the ubiquitination-dependent proteasome degradation system is counterbalanced by a large group of deubiquitin proteases with distinct substrate preference. Until now, whether deubiquitination by ubiquitin-specific proteases can regulate the clock protein stability and circadian pathways remains largely unclear. The mammalian clock protein, cryptochrome 1 (CRY1), is degraded via the FBXL3-mediated ubiquitination pathway, suggesting that it is also likely to be targeted by the deubiquitination pathway. Here, we identified that USP2a, a circadian-controlled deubiquitinating enzyme, interacts with CRY1 and enhances its protein stability via deubiquitination upon serum shock. Depletion of Usp2a by shRNA greatly enhances the ubiquitination of CRY1 and dampens the oscillation amplitude of the CRY1 protein during a circadian cycle. By stabilizing the CRY1 protein, USP2a represses the Per2 promoter activity as well as the endogenous Per2 gene expression. We also demonstrated that USP2a-dependent deubiquitination and stabilization of the CRY1 protein occur in the mouse liver. Interestingly, the pro-inflammatory cytokine, TNF-α, increases the CRY1 protein level and inhibits circadian gene expression in a USP2a-dependent fashion. Therefore, USP2a potentially mediates circadian disruption by suppressing the CRY1 degradation during inflammation.

Curcumin molecular targets in obesity and obesity-related cancers

Obesity is characterized as an increased BMI, which is associated with the increased risk of several common cancers, including colorectal, breast, endometrial, renal, esophageal, gallbladder, melanoma, multiple myeloma, leukemia, lymphoma and prostate cancer. The increased risk of obesity-related cancers could be mediated by insulin resistance, adipokines, obesity-related inflammatory cytokines, sex hormones, transcription factors and oxidative stress, which disrupt the balance between cell proliferation and apoptosis. The yellowish compound, curcumin (diferuloylmethane), is known to possess multifaceted pharmacological effects. The molecular mechanisms linking obesity to cancer risk, and how curcumin mediates anticancer and obesity activities, have not yet been publicized. Curcumin modulates multiple molecular targets and reverses insulin resistance as well as other symptoms that are associated with obesity-related cancers. In this study, we show that ample evidence exists to support recommendations that curcumin mediates multiple molecular pathways, and is considered to be of therapeutic value in the treatment and prevention of obesity-related cancers.

New insights into anticarcinogenic properties of adiponectin: a potential therapeutic approach in breast cancer?

Obesity is a recognized breast cancer risk factor in postmenopausal women. A recent hypothesis suggests a major role for adipose tissue in carcinogenesis. During many years, the adipose tissue was only considered as a fat storage of energy. This tissue is now described as an endocrine organ secreting a large range of molecules called adipokines. Among these adipokines, adiponectin may play a major role in breast cancer. Plasma adiponectin levels were found to be decreased in cases of breast cancer and in obese patients. Adiponectin may act directly on breast cancer cells by inhibiting proliferation and angiogenesis or by stimulating apoptosis. Increasing adiponectin levels may be of major importance in the prevention and/or the treatment of breast cancer. This therapeutic approach may be of particular significance for obese patients. The beneficial effects of adiponectin and its possible therapeutic applications will be discussed in this review.

Paracrine-acting adiponectin promotes mammary epithelial differentiation and synergizes with genistein to enhance transcriptional response to estrogen receptor β signaling

Mammary stromal adipocytes constitute an active site for the synthesis of the adipokine, adiponectin (APN) that may influence the mammary epithelial microenvironment. The relationship between "local," mammary tissue-derived APN and breast cancer risk is poorly understood. Here, we identify a novel mechanism of APN-mediated signaling that influences mammary epithelial cell proliferation, differentiation, and apoptosis to modify breast cancer risk. We demonstrate that early dietary exposure to soy protein isolate induced mammary tissue APN production without corresponding effects on systemic APN levels. In estrogen receptor (ER)-negative MCF-10A cells, recombinant APN promoted lobuloalveolar differentiation by inhibiting oncogenic signal transducer and activator of transcription 3 activity. In ER-positive HC11 cells, recombinant APN increased ERβ expression, inhibited cell proliferation, and induced apoptosis. Using the estrogen-responsive 4X-estrogen response element promoter-reporter construct to assess ER transactivation and small interfering RNA targeting of ERα and ERβ, we show that APN synergized with the soy phytoestrogen genistein to promote ERβ signaling in the presence of estrogen (17β-estradiol) and ERβ-specific agonist 2,3-bis(4-hydroxyphenyl)-propionitrile and to oppose ERα signaling in the presence of the ERα-specific agonist 4,4',4'-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol. The enhancement of ERβ signaling with APN + genistein cotreatments was associated with induction of apoptosis, increased expression of proapoptotic/prodifferentiation genes (Bad, p53, and Pten), and decreased antiapoptotic (Bcl2 and survivin) transcript levels. Our results suggest that mammary-derived APN can influence adjacent epithelial function by ER-dependent and ER-independent mechanisms that are consistent with reduction of breast cancer risk and suggest local APN induction by dietary factors as a targeted approach for promotion of breast health.

Molecular mechanisms of leptin and adiponectin in breast cancer

Obesity is associated with an increased risk of breast cancer in postmenopausal women. Accumulating evidence suggests that adipose tissue, which is an endocrine organ producing a large range of factors, may interfere with breast cancer development. Leptin and adiponectin are two major adipocyte-secreted hormones. The pro-carcinogenic effect of leptin and conversely, the anti-carcinogenic effect of adiponectin result from two main mechanisms: a modulation in the signalling pathways involved in proliferation process and a subtle regulation of the apoptotic response. This review provides insight into recent findings on the molecular mechanisms of leptin and adiponectin in mammary tumours, and discusses the potential interplay between these two adipokines in breast cancer.

Bidirectional signaling of mammary epithelium and stroma: implications for breast cancer--preventive actions of dietary factors

The mammary gland is composed of two major cellular compartments: a highly dynamic epithelium that undergoes cycles of proliferation, differentiation and apoptosis in response to local and endocrine signals and the underlying stroma comprised of fibroblasts, endothelial cells and adipocytes, which collectively form the mammary fat pad. Breast cancer originates from subversions of normal growth regulatory pathways in mammary epithelial cells due to genetic mutations and epigenetic modifications in tumor suppressors, oncogenes and DNA repair genes. Diet is considered a highly modifiable determinant of breast cancer risk; thus, considerable efforts are focused on understanding how certain dietary factors may promote resistance of mammary epithelial cells to growth dysregulation. The recent indications that stromal cells contribute to the maintenance of the mammary epithelial 'niche' and the increasing appreciation for adipose tissue as an endocrine organ with a complex secretome have led to the novel paradigm that the mammary stromal compartment is itself a relevant target of bioactive dietary factors. In this review, we address the potential influence of dietary factors on mammary epithelial-stromal bidirectional signaling to provide mechanistic insights into how dietary factors may promote early mammary epithelial differentiation to decrease adult breast cancer risk.

Adiponectin and breast cancer

Adiponectin, an adipose tissue-derived hormone, has been studied intensively for the past decade because of its anti-inflammatory, anti-atherogenic, and anti-diabetic properties. Recent advances suggest that adiponectin also plays an important role in the development and progression of various cancers, especially obesity-related cancers. In this review, the authors focus on the potential role of adiponectin in breast cancer, an obesity- and endocrine-associated tumor. Epidemiological studies have shown that plasma adiponectin level is a risk factor for breast cancer in post-menopausal women. Adiponectin and its receptors are expressed on both breast cancer line cells and tumor tissues. Furthermore, exogenous adiponectin has exhibited therapeutic potential in animal models. Underlying mechanisms include the inhibition of cell proliferation and promotion of apoptosis, the regulation of tumorigenic-related factors, and the suppression of angiogenesis. The signaling pathways linking adiponectin with tumorigenesis might provide potential drug targets for the future. However, more convincing evidence is needed to fully elucidate the exact role of adiponectin in breast cancer, since both its beneficial effects and possible mechanisms remain controversial.

Adiponectin and breast cancer

Adiponectin, an adipose tissue-derived hormone, has been studied intensively for the past decade because of its anti-inflammatory, anti-atherogenic, and anti-diabetic properties. Recent advances suggest that adiponectin also plays an important role in the development and progression of various cancers, especially obesity-related cancers. In this review, the authors focus on the potential role of adiponectin in breast cancer, an obesity- and endocrine-associated tumor. Epidemiological studies have shown that plasma adiponectin level is a risk factor for breast cancer in post-menopausal women. Adiponectin and its receptors are expressed on both breast cancer line cells and tumor tissues. Furthermore, exogenous adiponectin has exhibited therapeutic potential in animal models. Underlying mechanisms include the inhibition of cell proliferation and promotion of apoptosis, the regulation of tumorigenic-related factors, and the suppression of angiogenesis. The signaling pathways linking adiponectin with tumorigenesis might provide potential drug targets for the future. However, more convincing evidence is needed to fully elucidate the exact role of adiponectin in breast cancer, since both its beneficial effects and possible mechanisms remain controversial.

Impact of AdipoR1 expression on breast cancer development

OBJECTIVE

Adiponectin serum levels have been shown to be inversely correlated with breast cancer risk. The protein is believed to act through adiponectin receptor 1 (AdipoR1) and has been suggested to play an important role in cancer development. While AdipoR1 is known to be expressed in invasive tumors, its role in DCIS remains elusive. We therefore investigated AdipoR1 expression in both invasive and preinvasive breast cancer.

METHODS

Tissue microarrays were established from paraffin-embedded archived tissues which contained 104 invasive breast cancers with adjacent preinvasive component (DCIS) as well as 96 preinvasive breast cancers. AdipoR1 expression was investigated by immunohistochemistry and correlated with clinical and tumor parameters.

RESULTS

AdipoR1 was detected in stromal and epithelial components of both invasive and preinvasive breast cancer. However, stromal and epithelial immunoreactivity for AdipoR1 was significantly higher in invasive breast cancer compared to preinvasive DCIS (p<0.001 and p=0.009). Within DCIS, AdipoR1 expression was inversely correlated with tumor size (r=-0.238, p=0.033). Menopausal status showed no influence on AdipoR1 expression.

CONCLUSIONS

The altered expression of AdipoR1 in invasive breast cancer compared to DCIS suggests that the receptor-binding protein adiponectin might exert growth inhibitory effects that are overcome in transformation of preinvasive to invasive breast cancer.

Influence of insulin resistance on adiponectin receptor expression in breast cancer

OBJECTIVE

Adipositas and insulin resistance are modifiable risk factors for breast cancer. Adiponectin seems to be an important linkage of these associations. In this study, we investigated the relationship between intratumoral adiponectin receptor expression and insulin resistance as well as intratumoral insulin/IGF receptor expression in breast cancer specimen.

METHODS

Breast cancer tissue and fasting serum were collected from 26 female patients. After microdissection of frozen samples, RNA was isolated and expression of insulin receptor, IGFR1, IGFR2, AdipoR1 and AdipoR2 was measured on mRNA level by means of real time RT-PCR. Fasting insulin, glucose and c-peptide serum levels were analysed by ELISA. Insulin resistance was calculated using the HOMA model.

RESULTS

We were able to confirm AdipoR1 and AdipoR2 expression, respectively, in breast cancer specimen. Actually, neither insulin serum level nor whole-body insulin resistance showed any effect on insulin/IGF or adiponectin receptor expression in breast cancer. A strong positive correlation between insulin as well as IGF1 receptor and AdipoR1, but not AdipoR2, expression could be observed. Interestingly, AdipoR2 expression significantly correlated with vascular and lymphovascular invasion of breast cancer.

CONCLUSION

We propose a close relationship between the intratumoral insulin signalling system and AdipoR1 but not AdipoR2 expression. As AdipoR2 but not AdipoR1 expression seems to correlate with invasiveness, we assume different functions of the two adiponectin receptors in breast cancer.