Tissue levels of adiponectin in breast cancer patients

The locoregional adiponectin and its synergistic antitumor effect with HIF-1α blockade in TSCC

Adiponectin (APN) is a kind of endogenous anti-tumor adipocytokine, which exerts its function by binding to its receptors (AdipoR1 and AdipoR2). However, hyperadiponectinemia is found in some pathophysiological processes without significant protective effect, which indicates the existence of APN resistance. Here, we aimed to investigate the locoregional expression of APN in tongue squamous cell carcinoma (TSCC) tissues, and to explore the potential regulatory mechanism of APN resistance under hypoxia. Consequently, we found that the protein expression of APN and AdipoR1, but not AdipoR2, was upregulated in the early stage of TSCC and after hypoxic treatment ex vivo and in vitro. Knockdown of HIF-1α decreased the level of APN and AdipoR1, and simultaneously, HIF-1α was identified as transcriptor of the APN. Intriguingly, a regenerative feedback of HIF-1α was unexpectedly detected after application of recombinant globular APN (gAPN), which most likely contributed to the APN resistance. Furthermore, HIF-1α blockade combined with gAPN has a prominent synergistic antitumor effect, which suggested an effective amelioration in APN resistance. In all, our study revealed the possible mechanism of APN resistance under hypoxia and provides a promising strategy of bi-target treatment with APN and HIF-1α for TSCC therapy.

Targeting of the Peritumoral Adipose Tissue Microenvironment as an Innovative Antitumor Therapeutic Strategy

The tumor microenvironment (TME) plays a key role in promoting and sustaining cancer growth. Adipose tissue (AT), due to its anatomical distribution, is a prevalent component of TME, and contributes to cancer development and progression. Cancer-associated adipocytes (CAAs), reprogrammed by cancer stem cells (CSCs), drive cancer progression by releasing metabolites and inflammatory adipokines. In this review, we highlight the mechanisms underlying the bidirectional crosstalk among CAAs, CSCs, and stromal cells. Moreover, we focus on the recent advances in the therapeutic targeting of adipocyte-released factors as an innovative strategy to counteract cancer progression.

Postmenopausal estrogen receptor positive breast cancer and obesity associated gene variants

Obesity is one of the most important health risks in postmenopausal women. Molecular pathways that are connected with obesity are believed to interact with the pathogenesis of breast cancer (BC). The aim of this research was to study the polymorphisms of two obesity-associated genes ADIPOQ and FTO that are also related to the pathogenesis of BC. Obesity-associated gene polymorphisms ADIPOQ rs1501299 and rs2241766, and FTO rs1477196, rs7206790, rs8047395, and rs9939609 were studied in 101 Turkish postmenopausal estrogen receptor-positive BC patients and 100 healthy control individuals. ADIPOQ rs1501299 was detected to be associated with protection against BC. The ADIPOQ rs1501299 TT genotype, the rs2241766 GT genotype and the G allele were found to be significantly higher in the control group. In addition, ADIPOQ rs1501299 polymorphism was protective in the recessive model and rs2241766 polymorphism was protective in the dominant model. While none of the FTO gene polymorphisms were found to be associated with BC, the frequencies of rs9939609 A allele and rs7206790 G allele were correlated with body mass index (BMI) in BC patients. ADIPOQ rs1501299 TT genotype, rs2241766 GT genotype, and G allele might be protective against BC in the Turkish population but this conclusion needs to be further verified.

Interaction between adipose tissue and cancer cells: role for cancer progression

Environment surrounding tumours are now recognized to play an important role in tumour development and progression. Among the cells found in the tumour environment, adipocytes from adipose tissue establish a vicious cycle with cancer cells to promote cancer survival, proliferation, metastasis and treatment resistance. This cycle is particularly of interest in the context of obesity, which has been found as a cancer risk factor. Cancers cells can reprogram adipocyte physiology leading to an "activated" phenotype characterized by delipidation and secretion of inflammatory adipokines. The adipocyte secretions then influence tumour growth and metastasis which has been mainly attributed to interleukin 6 (IL-6) or leptin but also to the release of fatty acids which are able to change cancer cell metabolism and signalling pathways. The aim of this review is to report recent advances in the understanding of the molecular mechanisms linking adipose tissue with cancer progression in order to propose new therapeutic strategies based on pharmacological or nutritional intervention.

ADIPOQ rs2241766 SNP as protective marker against DIBC development in Mexican population

BACKGROUND

Adiponectin protein and some variations in its gene, ADIPOQ have recently been associated with cancer because they regulate glucose and lipid metabolism as well as anti-apoptotic and anti-inflammatory proteins.

AIM

The aim of this study was to analyse the relationship between selected biochemical markers, anthropometric indices and ADIPOQ rs2241766 and rs1501299 SNPs in ductal infiltrating breast cancer (DIBC) in a Mexican population.

METHODS

This cross-sectional study included 64 DIBC patients and 167 healthy women. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was performed to identify the genotypes of the rs2241766 (exon 2) and rs1501299 (intron 2) ADIPOQ polymorphisms. Corporal composition and biochemical markers included body mass index (BMI), waist circumference (WC), hip circumference (HC), waist-hip ratio (WHR), glucose, cholesterol, triglycerides and high- and low-density lipoprotein cholesterol.

RESULTS

Patients with DIBC had higher serum glucose, WC and WHR than controls. Intergroup differences in allele and genotype frequencies were found for both polymorphisms (P < 0.05). Patients carrying the rs2241766 TT and TG genotypes had higher values of WC, HC and WHR, but only TG carriers had higher levels of glucose. For the SNP rs1501299, carriers of the GG genotype in the DIBC group had higher values of glucose, WC, HC and WHR than the respective control group.

CONCLUSIONS

These results suggest that WC, HC and WHR are better predictors of DIBC than BMI. The ADIPOQ SNP rs2241766 emerges as a protective factor, whereas rs1501299 is a risk factor for DIBC development in a Mexican population.

Association of serum adiponectin with breast cancer: A meta-analysis of 27 case-control studies

BACKGROUND

Emerging published studies have indicated that adiponectin is involved in tumorigenesis of breast cancer. However, the results of available studies were inconsistent. The aim of this updated meta-analysis was to assess the association of adiponectin with breast cancer.

MATERIALS AND METHODS

PubMed, EMBASE, Wanfang databases, and the China National Knowledge Infrastructure (CNKI) were systematically searched from inception to June 2018. The mean difference (MD) with 95% confidence interval (CI) were estimated and pooled to investigate the effect sizes.

RESULTS

Twenty-seven eligible articles that met the study criteria were included in the current meta-analysis. Overall, there was an evident inverse association between serum adiponectin levels and breast cancer (MD = -0.29, 95%CI = (-0.38, -0.21), P < .001). Asian subgroup showed a significant negative association between serum adiponectin concentrations and breast cancer in subgroup analysis by ethnicity (MD = -2.19, 95%CI = (-3.45, -0.94), P < .001). However, no statistical significance was found in Caucasian subgroup (MD = -0.65, 95%CI = (-1.47, 0.17), P = 0.12). Additionally, a further subgroup analysis of Asian stratified by menopausal status showed higher concentrations of adiponectin in healthy control group, whether they were premenopausal (MD = -0.85, 95%CI = (-1.50, -0.19), P = .01) or postmenopausal (MD = -2.17, 95%CI = (-4.17, -0.18), P = .03). No significant difference was observed concerning the association between serum adiponectin and breast cancer metastasis (MD = -1.56, 95%CI = (-4.90, 1.78), P = .36).

CONCLUSION

The current meta-analysis suggests that the serum adiponectin may be inversely associated with breast cancer. Decreased serum adiponectin levels in premenopausal women may also be inversely associated with breast cancer risk other than postmenopausal status. In addition, low serum adiponectin levels in Asian women were more likely to be associated with breast cancer risk than Caucasian women.

Roles of Adiponectin Signaling Related Proteins in Mammary Tumor Development

Objective

This study aims to investigate the expression levels of adiponectin signaling related proteins in mammary tissue, liver and breast cancer tissue in mice. Adiponectin, an adipocytokine, is secreted from adipose tissue and has been documented to have roles in diabetes, inflammation, and cancer development. In particular, levels of serum adiponectin are inversely associated with obesity and a decrease in serum adiponectin levels have been reported to be associated with breast cancer. There are two adiponectin receptor subtypes, AdipoR1 and AdipoR2, which have been identified in mammalian tissues, including human cancer cell lines and also in human mammary tumors. However, the role of adiponectin receptors in breast cancer development remains to be established.

Methods

In this study, MMTV-TGF-α transgenic mice were fed from week 10 up to week 74 of age. Expression levels of adiponectin, AdipoR1 and AdipoR2 proteins were measured in the mammary fat pad (MFP), mammary tumor (MT) and liver tissues from 74 weeks old MMTV-TGF-α transgenic mice with and without MT using Western Blot. Adiponectin levels were measured using ELISA assay.

Results

Protein expression levels of Adiponectin and AdipoR1 were significantly lower in MTs compared to control tissues. However, AdipoR2 protein expression levels were similar in MT and MFP tissues from MT-positive and MT-negative mice. The expression levels of adiponectin, AdipoR1 and AdipoR2 proteins in liver tissues were also similar in MT-positive and MT-negative mice. Serum adiponectin levels of the MT-positive and MT-negative mice were similar.

Conclusion

These results indicate that adiponectin and its receptors are differentially regulated depending upon the specific tissue analyzed. AdipoR1 and adiponectin may play important roles in MT development.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

ADIPOQ/adiponectin induces cytotoxic autophagy in breast cancer cells through STK11/LKB1-mediated activation of the AMPK-ULK1 axis

ADIPOQ/adiponectin, an adipocytokine secreted by adipocytes in the breast tumor microenvironment, negatively regulates cancer cell growth hence increased levels of ADIPOQ/adiponectin are associated with decreased breast cancer growth. However, its mechanisms of action remain largely elusive. We report that ADIPOQ/adiponectin induces a robust accumulation of autophagosomes, increases MAP1LC3B-II/LC3B-II and decreases SQSTM1/p62 in breast cancer cells. ADIPOQ/adiponectin-treated cells and xenografts exhibit increased expression of autophagy-related proteins. LysoTracker Red-staining and tandem-mCherry-GFP-LC3B assay show that fusion of autophagosomes and lysosomes is augmented upon ADIPOQ/adiponectin treatment. ADIPOQ/adiponectin significantly inhibits breast cancer growth and induces apoptosis both in vitro and in vivo, and these events are preceded by macroautophagy/autophagy, which is integral for ADIPOQ/adiponectin-mediated cell death. Accordingly, blunting autophagosome formation, blocking autophagosome-lysosome fusion or genetic-knockout of BECN1/Beclin1 and ATG7 effectively impedes ADIPOQ/adiponectin induced growth-inhibition and apoptosis-induction. Mechanistic studies show that ADIPOQ/adiponectin reduces intracellular ATP levels and increases PRKAA1 phosphorylation leading to ULK1 activation. AMPK-inhibition abrogates ADIPOQ/adiponectin-induced ULK1-activation, LC3B-turnover and SQSTM1/p62-degradation while AMPK-activation potentiates ADIPOQ/adiponectin's effects. Further, ADIPOQ/adiponectin-mediated AMPK-activation and autophagy-induction are regulated by upstream master-kinase STK11/LKB1, which is a key node in antitumor function of ADIPOQ/adiponectin as STK11/LKB1-knockout abrogates ADIPOQ/adiponectin-mediated inhibition of breast tumorigenesis and molecular analyses of tumors corroborate in vitro mechanistic findings. ADIPOQ/adiponectin increases the efficacy of chemotherapeutic agents. Notably, high expression of ADIPOQ receptor ADIPOR2, ADIPOQ/adiponectin and BECN1 significantly correlates with increased overall survival in chemotherapy-treated breast cancer patients. Collectively, these data uncover that ADIPOQ/adiponectin induces autophagic cell death in breast cancer and provide in vitro and in vivo evidence for the integral role of STK11/LKB1-AMPK-ULK1 axis in ADIPOQ/adiponectin-mediated cytotoxic autophagy.

The molecular basis of breast cancer pathological phenotypes

The histopathological evaluation of morphological features in breast tumours provides prognostic information to guide therapy. Adjunct molecular analyses provide further diagnostic, prognostic and predictive information. However, there is limited knowledge of the molecular basis of morphological phenotypes in invasive breast cancer. This study integrated genomic, transcriptomic and protein data to provide a comprehensive molecular profiling of morphological features in breast cancer. Fifteen pathologists assessed 850 invasive breast cancer cases from The Cancer Genome Atlas (TCGA). Morphological features were significantly associated with genomic alteration, DNA methylation subtype, PAM50 and microRNA subtypes, proliferation scores, gene expression and/or reverse-phase protein assay subtype. Marked nuclear pleomorphism, necrosis, inflammation and a high mitotic count were associated with the basal-like subtype, and had a similar molecular basis. Omics-based signatures were constructed to predict morphological features. The association of morphology transcriptome signatures with overall survival in oestrogen receptor (ER)-positive and ER-negative breast cancer was first assessed by use of the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) dataset; signatures that remained prognostic in the METABRIC multivariate analysis were further evaluated in five additional datasets. The transcriptomic signature of poorly differentiated epithelial tubules was prognostic in ER-positive breast cancer. No signature was prognostic in ER-negative breast cancer. This study provided new insights into the molecular basis of breast cancer morphological phenotypes. The integration of morphological with molecular data has the potential to refine breast cancer classification, predict response to therapy, enhance our understanding of breast cancer biology, and improve clinical management. This work is publicly accessible at www.dx.ai/tcga_breast. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Obesity-Breast Cancer Conundrum: An Analysis of the Issues

Breast cancer develops over a timeframe of 2-3 decades prior to clinical detection. Given this prolonged latency, it is somewhat unexpected from a biological perspective that obesity has no effect or reduces the risk for breast cancer in premenopausal women yet increases the risk for breast cancer in postmenopausal women. This conundrum is particularly striking in light of the generally negative effects of obesity on breast cancer outcomes, including larger tumor size at diagnosis and poorer prognosis in both pre- and postmenopausal women. This review and analysis identifies factors that may contribute to this apparent conundrum, issues that merit further investigation, and characteristics of preclinical models for breast cancer and obesity that should be considered if animal models are used to deconstruct the conundrum.

The Relationship between Adiponectin and Breast Cancer

OBJECTIVE

Breast cancer is the most common type of cancer in women worldwide. It is indicated that increased body mass index elevates the risk of developing breast cancer, worsens prognosis, and decreases survival. Several polymorphisms of adiponectin have been shown to affect serum levels of adiponectin and their association with breast cancer. The aim of this study was to investigate the relationship between the adiponectin 45T/G and 276 G/T gene polymorphism and breast cancer in the East Marmara region.

MATERIALS AND METHODS

A case-control study was performed in 97 patients with breast cancer and 101 controls in East Marmara in order to evaluate the prevalence of adiponectin gene polymorphism at positions 45 and 276. Patients with familial breast cancer and those who had received chemotherapy or radiotherapy were excluded from the study. Adiponectin gene polymorphisms were investigated using polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Adiponectin 45T/G gene genotype frequencies of TT, TG, and GG were 61.9%, 37.1%, and 1% in patients with breast cancer, and 67.3%, 30.7%, and 2% in the control group, respectively. Adiponectin 276G/T gene genotype frequencies of GG, GT, and TT were 45.4%, 45.4%, and 9.3% in patients with breast cancer and 55.4%, 39.6%, and 5.0% in the control group, respectively.

CONCLUSION

Our study showed that adiponectin 45T/G and 276 G/T gene polymorphism is not associated with breast cancer risk in patients from the East Marmara region.

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.

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.

The role of adiponectin signaling in metabolic syndrome and cancer

The increased prevalence of obesity has mandated extensive research focused on mechanisms responsible for associated clinical complications. Emerging from the focus on adipose tissue biology as a vitally important adipokine is adiponectin which is now believed to mediate anti-diabetic, anti-atherosclerotic, anti-inflammatory, cardioprotective and cancer modifying actions. Adiponectin mediates these primarily beneficial effects via direct signaling effects and via enhancing insulin sensitivity via crosstalk with insulin signaling pathways. Reduced adiponectin action is detrimental and occurs in obesity via decreased circulating levels of adiponectin action or development of adiponectin resistance. This review will focus on cellular mechanisms of adiponectin action, their crosstalk with insulin signaling and the resultant role of adiponectin in cardiovascular disease, diabetes and cancer and reviews data from in vitro cell based studies through animal models to clinical observations.

Genetic variation in adipokine genes and associations with adiponectin and leptin concentrations in plasma and breast tissue

BACKGROUND

Circulating adipokines may be associated with breast cancer risk. Genetic variants governing adipokines and adipokine receptors may also predict risk, but their effect on breast adipokine concentrations is unknown.

METHODS

We conducted a cross-sectional analysis of functional SNPs in 5 adipokine genes [adiponectin, leptin (LEP), and their receptors] among 85 cancer-free women who were undergoing reduction mammoplasty.

RESULTS

In multivariable-adjusted regression models, compared with the common GG genotype, the AA genotype of the LEP A19G SNP was associated with 27% lower plasma adiponectin [ratio, 0.73; 95% confidence interval (CI), 0.54-0.98] and leptin (ratio, 0.73; 95% CI, 0.55-0.96). Women with the AG genotype of LEP A19G had 39% lower breast leptin (ratio, 0.61; 95% CI, 0.39-0.97) compared with those with the GG genotype. No associations were observed for SNPs in the remaining genes.

CONCLUSIONS

Genetic variation in LEP may alter endogenous adipokine concentrations in circulation and in breast tissues.

IMPACT

These preliminary findings may support the hypothesis that genetic variation in adipokine genes modifies circulating adipokine concentrations and possibly leptin concentrations in local breast tissues, which may be associated with breast cancer risk.

Excess weight gain accelerates 1-methyl-1-nitrosourea-induced mammary carcinogenesis in a rat model of premenopausal breast cancer

In contrast to the null effects generally reported, high-risk premenopausal women (Gail score ≥1.66) enrolled in the Breast Cancer Prevention P-1 Trial were recently reported to be at increased risk for breast cancer when overweight (HR = 1.59) or obese (HR = 1.70). To investigate this clinical observation in a preclinical setting, ovary-intact female rats were intraperitoneally injected with 50 mg/kg 1-methyl-1-nitrosourea at 21 days of age to simulate premenopausal women with increased risk. Two commercially available strains of Sprague-Dawley rat (Taconic Farms) were used, which are dietary resistant (DR) or dietary susceptible (DS) to excess weight gain when fed a purified diet containing 32% kcal from fat, similar to levels consumed by the typical American woman. DS rats were approximately 15.5% heavier than DR rats at study termination and plasma leptin indicated a marked difference in adiposity. DS rats had higher incidence (26% increase), multiplicity (2.5-fold increase), and burden (5.4-fold increase) of mammary carcinomas with a concomitant reduction in cancer latency (16% earlier detection) compared with DR rats (P < 0.001 for all analyses), and displayed a higher proportion of hormone receptor negative tumors compared with DR rats [OR = 1.78; 95% confidence interval (CI), 0.83-3.81]. Circulating levels of several breast cancer-risk factors, including leptin, adiponectin:leptin ratio, insulin, insulin-like growth factor (IGF)-1, IGF-1:IGF-1 binding protein-3 ratio, and calculated insulin resistance (HOMA-IR) were negatively impacted in DS rats (P < 0.05 for all analyses). These findings support further investigation of the effects of excess weight in high-risk premenopausal women and demonstrate a useful preclinical model for rapid evaluation of mechanistic hypotheses.

Obesity, metabolism and the microenvironment: Links to cancer

Historically, cancer research has focused on identifying mutations or amplification of genes within the tumor, which informed the development of targeted therapies against affected pathways. This work often considers tumor cells in isolation; however, it is becoming increasingly apparent that the microenvironment surrounding tumor cells strongly influences tumor onset and progression. This is the so-called “seed and soil” hypothesis wherein the seed (cancer cell) is fed and molded by the metabolites, growth factors, modifications of the extracellular matrix or angiogenic factors provided by the soil (or stroma). Currently, 65% of the US population is obese or overweight; similarly staggering figures are reported in US children and globally. Obesity mediates and can exacerbate, both normal and tumor microenvironment dysfunction. Many obesity-associated endocrine, metabolic and inflammatory mediators are suspected to play a role in oncogenesis by modifying systemic nutrient metabolism and the nutrient substrates available locally in the stroma. It is vitally important to understand the biological processes linking obesity and cancer to develop better intervention strategies aimed at curbing the carcinogenic events associated with obesity. In this review, obesity-driven changes in both the normal and tumor microenvironment, alterations in metabolism, and release of signaling molecules such as endocrine, growth, and inflammatory mediators will be highlighted. In addition, we will discuss the effects of the timing of obesity onset or particular “windows of susceptibility,” with a focus on breast cancer etiology.

Decreased adiponectin level is associated with aggressive phenotype of tongue squamous cell carcinoma

Circulating adiponectin levels are inversely associated with risk of various obesity-related cancers. However, the effect of adiponectin on carcinogenesis and progression of tongue squamous cell carcinoma (TSCC) remains unknown. We measured serum adiponectin levels in 59 patients with TSCC and 50 healthy controls. Expression of adiponectin and its receptors in paired tumor and paracancerous specimens were determined by immunohistochemical staining (n = 37) and western blot (n = 30), respectively. Serum adiponectin level was lower in patients than in controls (5.0 ± 2.4 vs 8.4 ± 3.5 μg/mL, P < 0.01), and was inversely associated with histological grade and lymph node metastasis but not tumor size. Local adiponectin levels in tumor tissue gradually decreased as tumor-node-metastasis stage increased, while the expression of adiponectin receptors was unchanged. In addition, serum adiponectin levels in the TSCC patients without metabolic and cardiovascular diseases, or without smoking and drinking habits, were still lower than in controls. Furthermore, adiponectin inhibited the migration, but not proliferation, of SCC15 cells in vitro. These results indicate that a decreased adiponectin level is associated with risk of TSCC. Hypoadiponectinemia might be used as a biomarker to predict an aggressive phenotype of TSCC.

Associations between adiponectin and two different cancers: breast and colon

OBJECTIVES

Breast and colon cancer are neoplasms well known to be related to obesity. Adiponectin, a protein that increases in obesity, seems to be involved in the relationship but clinical data are limited.

METHODS

In this study, we therefore evaluated the serum adiponectin levels in 87 breast and 27 colon cancer patients and assessed the relation with BMI, menopausal status, receptor status and stage of disease.

RESULTS

Serum adiponectin levels were lower in cancer cases (8583 ± 2095 ng/ml for breast cancer, 9513 ± 2276 for colon cancer) than in controls (13905 ± 3263).

CONCLUSION

A low serum adiponectin level may be associated with both breast and colon cancer, and that this association is not statistically significant for either receptor or menopausal status in breast cancer groups.

Adipokines in plasma and breast tissues: associations with breast cancer risk factors

BACKGROUND

Blood adipokines are associated with breast cancer risk; however, blood-breast adipokine correlations and factors that explain variation in adipokines are unknown.

METHODS

Plasma (n = 155) and breast (n = 85) leptin and adiponectin were assessed by immunoassays in women with no history of cancer. Multivariable-adjusted regression models were used to determine breast adipokine associations.

RESULTS

Through body mass index (BMI)-adjusted analyses, we initially observed positive plasma-breast correlations for leptin (r = 0.41, P = 0.0002) and adiponectin (r = 0.23, P = 0.05). The positive plasma-breast correlation for leptin was strongest among normal weight women (r = 0.62), whereas the correlation for adiponectin was strongest among obese women (r = 0.31). In multivariable models, adjusting for BMI, demographic, reproductive, and lifestyle factors, plasma leptin was not associated with breast leptin, and only the highest quartile of plasma adiponectin was associated with tissue levels. Of the risk factors investigated, those that contributed most to the variation in breast tissue adipokines were BMI and race for leptin, oral contraceptive use and smoking status for adiponectin.

CONCLUSIONS

Although we report positive plasma-breast adipokine correlations overall, plasma adipokine concentrations may not be good surrogates for breast concentrations among all women. Predictors of breast adipokines vary, depending on subject characteristics, possibly explaining inconsistent epidemiologic results and they implicate differing pathways toward carcinogenesis.

IMPACT

A clearer understanding of the relationships between plasma adipokines and their levels within the target organ is necessary to better understand the impact of these hormones on breast cancer risk. Future studies are needed to identify additional factors associated with breast adipokines in target tissues.

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.

Expression of leptin, leptin receptor, adiponectin, and adiponectin receptor in ductal carcinoma in situ and invasive breast cancer

PURPOSE

Adipocytokines, such as leptin, resistin, and adiponectin, are associated with obesity and breast cancer. Several studies have indicated that adipocytokines may influence tumor growth or differentiation. The aims of this study were to determine the expression of leptin, leptin receptor (ObR), adiponectin and adiponectin receptor (AdipoR) in human breast cancer, to evaluate their prognostic significance in the breast cancer.

METHODS

Specimens from 198 patients with primary breast cancer were enrolled, and representative paraffin tumor blocks were selected for constructing tissue microarrarys (TMA). Immunohistochemical staining for leptin, ObR, adiponectin, and AdipoR was performed using TMA, and the clinicopathologic characteristics were evaluated from the patient's medical records.

RESULTS

Stage 0 breast cancer accounted for 41 cases, and 157 cases were invasive cancer. Positive rates of leptin and ObR expression in the ductal carcinoma in situ (DCIS) group were significantly higher than those of the invasive cancer group (97.4% vs. 34.0%, p<0.001; 74.4% vs. 29.8%, p<0.001). However, positive rates of adiponectin and AdipoR expression in the invasive cancer group were significantly higher than those in the DCIS group (53.7% vs. 33.3%, p=0.024; 59.9% vs. 26.3%, p<0.001). High leptin expression was significantly associated with high Ki-67 expression (p=0.016). High adiponectin expression was significantly correlated with smaller tumor size (p=0.001).

CONCLUSION

We suggest that losses of leptin and ObR expression could be associated with invasive cancer, whereas high adiponectin and AdipoR expression may be associated with breast cancer invasiveness.

The role of adiponectin (ADIPOQ) gene polymorphisms in the susceptibility and prognosis of non-small cell lung cancer

To study the role of the adiponectin (ADIPOQ) gene single-nucleotide polymorphism (SNP) in the susceptibility and prognosis for non-small cell lung cancer (NSCLC), we recruited 344 patients with NSCLC, of which 141 had undergone surgical resection and post-surgery follow up. For controls, there were 264 healthy volunteers for the control group, matched in age and sex with the NSCLC patients. Genotyping of SNPs in the ADIPOQ gene, namely, rs266729 (11365C>G); rs822395 (4034A>C); rs822396 (3964A>G); rs2241766 (+45T>G) were performed. Of all SNPs in the ADIPOQ gene, only the TT genotype and T allele frequency of the rs2241766 were more prevalent in NSCLC subjects than in controls. The TT genotype of rs2241766 was significantly associated with susceptibility to NSCLC before and after adjustment for age, sex, body mass index, and smoking status. In the survival analyses of subjects receiving surgical resection, only the SNPs of rs2241766 were significantly related to overall survival of NSCLC. Our results suggest that the SNP rs2241766 of the ADIPOQ gene may determine both susceptibility to NSCLC, and the prognosis for those who underwent surgical treatment.

Effect of chronic and intermittent calorie restriction on serum adiponectin and leptin and mammary tumorigenesis

The effect of chronic (CCR) and intermittent (ICR) caloric restriction on serum adiponectin and leptin levels was investigated in relation to mammary tumorigenesis. 10-wks old MMTV-TGF-α female mice were assigned to ad libitum fed (AL; AIN-93M diet), ICR (3-week 50% caloric restriction, AIN-93M-mod diet, 2× protein, fat, vitamins, and minerals followed by 3-wks 100% AL consumption of AIN-93M), and CCR (calorie and nutrient intake matched for each 6-wks ICR cycle, ∼ 75% of AL) groups. Mice were sacrificed at 79 (end of restriction) or 82 (end of refeeding) wks of age. Serum was obtained in cycles 1, 3, 5, 8, 11, and terminal. Mammary tumor incidence was 71.0%, 35.4%, and 9.1% for AL, CCR, and ICR mice, respectively. Serum adiponectin levels were similar among groups with no impact of either CCR or ICR. Serum leptin level rose in AL mice with increasing age but was significantly reduced by long-term CCR and ICR. The ICR protocol was also associated with an elevated adiponectin/leptin ratio. In addition, ICR-restricted mice had increased mammary tissue AdipoR1 expression and decreased leptin and ObRb expression compared with AL mice. Mammary fat pads from tumor-free ICR-mice had higher adiponectin expression than AL and CCR mice whereas all tumor-bearing mice had weak adiponectin signal in mammary fat pad. Although we did not show an association of either adiponectin or leptin with individual mice in relation to mammary tumorigenesis, we did find that reduced serum leptin and elevated adiponectin/leptin ratio were associated with the protective effect of intermittent calorie restriction.

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.

Leptin and Adiponectin: new players in the field of tumor cell and leukocyte migration

Adipose tissue is no longer considered to be solely an energy storage, but exerts important endocrine functions, which are primarily mediated by a network of various soluble factors derived from fat cells, called adipocytokines. In addition to their responsibility to influence energy homeostasis, new studies have identified important pathways linking metabolism with the immune system, and demonstrating a modulatory role of adipocytokines in immune function. Additionally, epidemiological studies underline that obesity represents a significant risk factor for the development of cancer, although the exact mechanism of this relationship remains to be determined. Whereas a possible influence of adipocytokines on the proliferation of tumor cells is already known, new evidence has come to light elucidating a modulatory role of this signaling substances in the regulation of migration of leukocytes and tumor cells. The migration of leukocytes is a key feature to fight cancer cells, whereas the locomotion of tumor cells is a prerequisite for tumor formation and metastasis. We herein review the latest tumor biological findings on the role of the most prominent adipocytokines leptin and adiponectin, which are secreted by fat cells, and which are involved in leukocyte migration, tumor growth, invasion and metastasis. This review thus accentuates the complex, interactive involvement of adipocytokines in the regulation of migration of both leukocytes and tumor cells, and gives an insight in the underlying molecular mechanisms.

IL-1 family in breast cancer: potential interplay with leptin and other adipocytokines

Obesity is associated with an increased risk of breast cancer. interleukin-1 (IL-1), a pro-inflammatory cytokine secreted by adipose tissue, is involved in breast cancer development. There is also convincing evidence that other adipocytokines including leptin not only have a role in haematopoiesis, reproduction and immunity but are also growth factors in cancer. Therefore, IL-1 family and leptin family are adipocytokines which could represent a major link between obesity and breast cancer progression. This minireview provides insight into recent findings on the prognostic significance of IL-1 and leptin in mammary tumours, and discusses the potential interplay between IL-1 family members and adipocyte-derived hormones in breast cancer.