Adiponectin mediates antiproliferative and apoptotic responses in human MCF7 breast cancer cells

in vitro Anti-Proliferative Effect of Adiponectin on Human Endometriotic Stromal Cells through AdipoR1 and AdipoR2 Gene Receptor Expression

BACKGROUND

Endometriosis is a complex disorder in reproductive age women which consist of stromal and epithelial cells implantation outside the uterine cavity. Adiponectin is a member of cytokine family with various metabolic roles and proliferation inhibition of many cancer cells. The aim of the present research was to determine adiponectin effect on human endometriotic stromal cells (ESCs) proliferation and their expression of adiponectin receptors.

METHODS

In this experimental study, endometrial biopsies (n=7) were taken. ESCs isolation was done by enzymatic digestion and cell filtrations. ESCs of each biopsy were divided into four groups: 0 (control), 10, 100, and 200 ng/ml adiponectin concentrations in three different times (24, 48 or 72 h). The effect of adiponectin on ESC viability and expression of mRNA Adipo receptor1 (R1) and Adipo receptor2 (R2) was determined by Trypan blue staining and semi-quantitative RT-PCR, respectively. Data were analyzed by one-way ANOVA and unpaired student's t-test, and P<0.05 was considered statistically significant.

RESULTS

Adiponectin inhibited human endometriotic stromal cell proliferation in time- and dose-dependent manners significantly (P=0.001). Expression of AdipoR1 and AdipoR2 gene receptors was increased in human ESCs significantly (P<0.05).

CONCLUSIONS

Adiponectin can suppress endometriosis by inhibiting ESC proliferation and increased AdipoR1 and AdipoR2 expression.

Arctigenin Suppress Th17 Cells and Ameliorates Experimental Autoimmune Encephalomyelitis Through AMPK and PPAR-γ/ROR-γt Signaling

Arctigenin is a herb compound extract from Arctium lappa and is reported to exhibit pharmacological properties, including neuronal protection and antidiabetic, antitumor, and antioxidant properties. However, the effects of arctigenin on autoimmune inflammatory diseases of the CNS, multiple sclerosis (MS), and its animal model experimental autoimmune encephalomyelitis (EAE) are still unclear. In this study, we demonstrated that arctigenin-treated mice are resistant to EAE; the clinical scores of arctigenin-treated mice are significantly reduced. Histochemical assays of spinal cord sections also showed that arctigenin reduces inflammation and demyelination in mice with EAE. Furthermore, the Th1 and Th17 cells in peripheral immune organs are inhibited by arctigenin in vivo. In addition, the Th1 cytokine IFN-γ and transcription factor T-bet, as well as the Th17 cytokines IL-17A, IL-17F, and transcription factor ROR-γt are significantly suppressed upon arctigenin treatment in vitro and in vivo. Interestedly, Th17 cells are obviously inhibited in CNS of mice with EAE, while Th1 cells do not significantly change. Besides, arctigenin significantly restrains the differentiation of Th17 cells. We further demonstrate that arctigenin activates AMPK and inhibits phosphorylated p38, in addition, upregulates PPAR-γ, and finally suppresses ROR-γt. These findings suggest that arctigenin may have anti-inflammatory and immunosuppressive properties via inhibiting Th17 cells, indicating that it could be a potential therapeutic drug for multiple sclerosis or other autoimmune inflammatory diseases.

Adiposity and cancer risk: new mechanistic insights from epidemiology

Excess body adiposity, commonly expressed as body mass index (BMI), is a risk factor for many common adult cancers. Over the past decade, epidemiological data have shown that adiposity-cancer risk associations are specific for gender, site, geographical population, histological subtype and molecular phenotype. The biological mechanisms underpinning these associations are incompletely understood but need to take account of the specificities observed in epidemiology to better inform future prevention strategies.

The diverse roles of adiponectin in non-small-cell lung cancer: current data and future perspectives

In recent years, there is growing research interest for the biological role of adipose tissue-derived bioactive factors, mainly including adipokines, in various forms of cancer. Adiponectin (APN) is the most abundant circulating adipokine, and a key mediator of several cancer-related processes, such as cell proliferation, apoptosis, regulation of tumor cell invasion and angiogenesis. In this review we summarize and critically discuss the published literature on the diverse roles of APN in non-small-cell lung cancer, including its implication in lung cancer development, its use as a diagnostic and prognostic biomarker, and its correlation with cancer-related cachexia. The main challenges and future perspectives, mainly with regard to the potential development of APN-targeted therapeutic agents in cancer therapeutics, are also briefly presented and discussed.

Adiponectin as a potential tumor suppressor inhibiting epithelial-to-mesenchymal transition but frequently silenced in prostate cancer by promoter methylation

BACKGROUND

Recent evidence suggests a particular role for obesity in prostate cancer (PCa) progression. Adiponectin (ADN) is a hormone secreted by adipose tissue and has a variety of functions including the inhibition of PCa cell proliferation. Although serum ADN levels have been identified to be related with carcinogenesis in a tissue-specific context, the exact role of endogenous ADN in PCa cells remains largely unknown.

METHODS

Two tissue microarrays were constructed and immunohistochemistry (IHC) was utilized to detect ADN's expression in a cohort of 96 Chinese PCa patients with radical prostatectomy as well as 15 cases with Benign Prostatic Hyperplasia (BPH). MTS and transwell assays were applied to validate the effects of ADN on proliferation and invasive capacity of PCa cells. Real-time PCR and Western blot were performed to evaluate the expression at transcript and protein levels. Epigenetic modifications of ADN's promoter after TGF-β1 treatment in 22RV1 cells was monitored by chromatin immunoprecipitation (ChIP). Methylation-Specific PCR (MSP) was performed to determine the methylation status of ADN's promoter.

RESULTS

IHC showed decreased levels of ADN in 1 of 15 (6.7%) BPH cases, 6 of 27 (22.2%) PCa cases with low Gleason score (<7), 18 of 26 (69.2%) cases with Gleason score 7, but 32 of 43 (74.4%) cases with high Gleason score (>7). Silencing endogenous ADN could promote proliferation and invasion of 22RV1 cells via orchestrating Epithelial-to-mesenchymal Transition (EMT) process. TGF-β1, a potent EMT inducer, could decrease levels of chromatin markers associated with active genes (H3K4me3, H4acetylK16), and increase levels of repressive marker (H3K27me3) at ADN promoter in 22RV1 cells. Additionally, 5-aza and TSA treatment restored ADN expression in LNCaP cells in which the ADN expression was almost absent. MSP analysis revealed that methylation in the promoter might be involved in decreased expression of ADN in PCa tissues.

CONCLUSION

Our findings indicated that endogenous ADN may function as a tumor suppressor gene through inhibiting EMT of PCa cells but is down-regulated in PCa via promoter hypermethylation.

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.

The association of adiponectin gene promoter variations with non-small cell lung cancer in a Han Chinese population

Recently, in vitro studies have demonstrated that adiponectin has antiangiogenic and tumor growth-limiting properties. Additionally, serum adiponectin levels have been associated with the risk of several cancers; specifically, serum adiponectin was significantly lower in lung cancer patients with advanced-stage disease. In this study, we examined the association of adiponectin gene promoter variations associated with adiponectin gene expression and plasma levels in non-small cell lung cancer (NSCLC) in a Han Chinese population. A total of 319 patients with NSCLC and 489 healthy individuals were recruited to evaluate the association of four adiponectin gene promoter single-nucleotide polymorphisms (SNPs) (SNP-12140G>A, SNP-11426A>G, SNP-11391G>A and SNP-11377C>G) with NSCLS risk. Additionally, we constructed haplotypes of these four SNPs and evaluated the association of these haplotypes with NSCLS risk. Our results showed that among these four SNPs, only SNP-12140G>A was associated with NSCLC risk (P<0.05). The haplotype analysis showed that no haplotype was associated with NSCLC after performing a Bonferroni correction (P>0.05). Additionally, an association analysis of the four SNPs stratified into pathologic stages I+II and III+IV showed that these SNPs did not exhibit significant differences between pathologic stages I+II and III+IV. Moreover, we did not observe any differences in allele and genotype frequency for these SNPs between adenocarcinoma and squamous cell carcinoma. Our results indicated that the G allele of SNP-12140 may be a risk factor for NSCLC (OR = 1.516; 95% CI: 1.098-2.094) in this Han Chinese population.

Estrogen receptor-α drives adiponectin effects on cyclin D1 expression in breast cancer cells

Obesity is a risk factor for breast cancer, largely due to altered expression of various adipocytokines. As it concerns adiponectin, there are not univocal results regarding its role in breast cancer occurrence and progression. Here, we demonstrate that in animals injected with human estrogen receptor (ER)-α-negative MDA-MB-231 cells pretreated with adiponectin (1 and 5 µg/ml), a significant reduction (60 and 40%, respectively) in tumor volume is observed, whereas an increased tumor growth (54 and 109%, respectively) is evidenced in the animals receiving human ER-α-positive MCF-7 cells. Moreover, cyclin D1 (CD1) mRNA and protein levels are decreased in MDA-MB-231 cells, whereas they are up-regulated in ER-α-positive cells by adiponectin. These findings fit with the opposite effects of adiponectin on CD1 promoter: 0.44- and 0.34-fold decrease in MDA-MB-231 cells and 0.63- and 0.95-fold increase in MCF-7 cells, treated with 1 and 5 µg/ml, respectively. Functional studies indicate that these effects are mediated by the specific protein 1 motif located in the CD1 promoter. In the absence of ER-α, the adiponectin-mediated down-regulation of CD1 involves the recruitment of corepressors. In the presence of ER-α, the adiponectin-induced expression of CD1 requires the involvement of an activator complex. In conclusion, we propose that a possible mechanism through which adiponectin differently affects breast cancer growth is the opposite modulation of CD1 levels accordingly to ER-α expression.

Modulatory effects of adiponectin on the polarization of tumor-associated macrophages

The plasticity of macrophages with selective functional phenotypes partially arises in respective to their microenvironment. Tumor-associated macrophages (TAMs) may promote disease progression with tumor specific manner. Here we report that in pediatric malignant soft-tissue tumors, the presence of TAMs and expression of adiponectin (APN) are heterogeneous. Both APN and TAMs had high expression in rhabdomyosarcoma, especially in the malignant subtype, alveolar rhabdomyosarcoma. To investigate the mode of action of APN on TAM activation, a murine MN/MCA1 sarcoma model was used. The Results revealed that exogenous APN had no effect on MN/MCA1 proliferation but tumor size was markedly reduced in apn(-/-) mice versus WT controls. The accumulation of TAMs in apn(-/-) mice was also reduced which correlated to downregulated serum levels of MCP-1. Likewise, TAMs in apn(-/-) mice exhibited a M1-like phenotype, characterized by increase in MHC II(high) population and M1 phenotypic markers, such as iNOS gene and serum TNF-α accompanied by a decrease in M2 markers, namely YM1 gene and serum IL-10. In addition, APN deficiency increased the number of CD4(+) T cells, CD8(+) T cells and NK cells in tumors and reduced tumor metastasis. The altered phenotype of TAMs in apn(-/-) mice was associated with a marked decrease in phospho-p38 and treatment with a p38 MAPK inhibitor significantly reduced tumor size and increased MHC II expression on TAMs in WT mice, implying p38 MAPK signaling pathway may contribute to APN-mediated TAM polarization. Collectively, our findings suggest that APN may have a potential role in regulating soft tissue sarcoma growth.

Expression of adiponectin and its receptors is altered in epithelial ovarian tumors and ascites-derived ovarian cancer cell lines

OBJECTIVES

Recent evidence suggests that higher body mass index is associated with a modest increase in ovarian cancer risk. Reduced serum levels of adiponectin are correlated with obesity and increased cancer risk. The objectives of the present study are to determine if expressions of adiponectin and its receptors, AdipoR1 and AdipoR2, are altered in epithelial ovarian tumors and ascites-derived ovarian cancer cell lines and to determine if plasma adiponectin levels are altered in the chicken model of ovarian cancer.

METHODS

Adiponectin, AdipoR1, and AdipoR2 mRNA concentrations in ovaries and chicken ovarian cancer (COVCAR) cell lines were determined by quantitative real-time polymerase chain reaction analysis. Existence of adiponectin isoforms in the ovaries and COVCAR cells was identified by nondenaturing gel electrophoresis. Adiponectin, AdipoR1, and AdipoR2 protein amounts were determined by Western blot analysis. Plasma total adiponectin levels were determined by an enzyme immunoassay.

RESULTS

Adiponectin, AdipoR1, and AdipoR2 mRNA concentrations were significantly lower in cancerous ovaries and COVCAR cell lines compared with normal ovaries and normal ovarian surface epithelial (NOSE) cells, respectively. Adiponectin in ovary and COVCAR cell lines appeared as a heavy-molecular-weight isoform that is greater than 720-kd mass. In addition, a lower-molecular-weight adiponectin isoform was found in COVCAR cells but not in NOSE cells. Adiponectin and AdipoR1 protein concentrations were not different in COVCAR cell lines compared with NOSE cells. However, AdipoR2 protein concentrations were significantly higher in cancerous ovaries but lower in COVCAR cell lines compared with normal ovaries and NOSE cells, respectively. Plasma adiponectin concentrations were not different in chickens that had ovarian carcinoma compared with control animals.

CONCLUSIONS

Expression of adiponectin in ovarian tumors and in metastatic ovarian tumor cells is likely to affect cellular metabolism and proliferation through activating AdipoR1 and/or AdipoR2. Plasma adiponectin levels may not be predictive of advanced stages of ovarian tumor in the chicken model.

Adiponectin mediates antiproliferative and apoptotic responses in endometrial carcinoma by the AdipoRs/AMPK pathway

OBJECTIVE

Determine the serum adiponectin levels in endometrial carcinoma (EC) cases and controls and explore the correlation between them. We assessed the functions of AdipoR1 and AdipoR2 in endometrial cancer cells to determine whether the AMPK/ERK and Akt pathways mediate the effects of adiponectin-induced apoptosis and anti-proliferation.

MATERIAL AND METHODS

The serum adiponectin levels were measured via enzyme-linked immunosorbent assay (ELISA). The proliferation and apoptosis rates were determined with MTT and annexin V/PI assays. To evaluate the activation of AMPK, ERK, and Akt and the expression of Bcl-2 and Cyclin D1, western blot analysis was performed in Ishikawa 3-H-12 cells. We down-regulated AdipoRs by si-RNA to assess their functions.

RESULTS

The serum adiponectin levels were significantly decreased in patients with EC compared to controls. The adiponectin-induced apoptosis and anti-proliferation effects in EC cells were blocked by Compound C. Ishikawa 3-H-12 cells exhibited time- and dose-dependent increases in the p-AMPK levels after treatment with adiponectin. Adiponectin treatment reduced the levels of ERK and Akt phosphorylations and cyclin D1 and Bcl-2 mRNA and protein expression. Compound C blocked the effects on ERK, Akt, cyclin D1, and Bcl-2. AdipoR1 and AdipoR2 were involved in adiponectin-induced growth inhibition and ERK activation inhibition. We speculated that AdipoR1 has a greater role than adipoR2 in apoptosis and Akt activation inhibition after adiponectin treatment.

CONCLUSION

Adiponectin was an apoptotic and anti-proliferation agent for EC cells, and these effects were dependent on the AMPK/ERK and Akt pathways. AdipoR1 and AdipoR2 may play different roles in this process.

Inverse association between visceral obesity and lymph node metastasis in gastric cancer

BACKGROUND

The relationship between fat distribution and lymph node metastasis has not been well studied. The goal of this study was to determine the impact of visceral obesity on lymph node metastasis in gastric cancer.

MATERIALS AND METHODS

Metastatic lymph node ratio (MLR) was defined as the number of involved nodes by tumor divided by the total number of resected lymph nodes. Visceral (VFA) and subcutaneous fat areas (SFA) were determined by measuring abdominal fat volume distribution via CT scan, and visceral obesity was defined as a VFA to total fat area ratio (V/T) >0.29.

RESULTS

With lymph node metastasis as a dependent variable, the following factors were significant in multivariate analysis among 495 patients: pathologic T stage (P < 0.001), lympho-vascular invasion (P < 0.001), and V/T (hazard ratio (HR) = 0.455, 95 % confidence interval (CI) = 0.263-0.786, P = 0.005). Similarly, when MLR was the dependent variable in multivariate analysis, MLR was significantly associated with lympho-vascular invasion (HR = 2.222, 95 % CI = 1.149-4.296, P = 0.018), and V/T (HR = 0.247, 95 % CI = 0.133-0.458, P < 0.001).

CONCLUSIONS

Visceral obesity defined by higher visceral to total fat area ratio was significantly associated with decreased MLR.

CTAB induced mitochondrial apoptosis by activating the AMPK–p53 pathway in hepatocarcinoma cells

CTAB induced mitochondrial apoptosis by activating the AMPK-p53 pathway in hepatocarcinoma cells.

The role of cytokines in breast cancer development and progression

Cytokines are highly inducible, secretory proteins that mediate intercellular communication in the immune system. They are grouped into several protein families that are referred to as tumor necrosis factors, interleukins, interferons, and colony-stimulating factors. In recent years, it has become clear that some of these proteins as well as their receptors are produced in the organisms under physiological and pathological conditions. The exact initiation process of breast cancer is unknown, although several hypotheses have emerged. Inflammation has been proposed as an important player in tumor initiation, promotion, angiogenesis, and metastasis, all phenomena in which cytokines are prominent players. The data here suggest that cytokines play an important role in the regulation of both induction and protection in breast cancer. This knowledge could be fundamental for the proposal of new therapeutic approaches to particularly breast cancer and other cancer-related disorders.

Epistatic interaction between adiponectin and survivin gene polymorphisms in endometrial carcinoma

Adiponectin appears to play an important role in the development and progression of several obesity-related malignancies. Also, overexpression of survivin, an inhibitor of apoptosis protein, is associated with increased risk of cancers. The aim of this study was to investigate the association between two polymorphisms in the adiponectin gene and endometrial cancer (EC) risk. We also investigated whether epistasis between surviving and adiponectin gene polymorphisms are associated with EC risk in an Iranian population. The samples comprised formalin-fixed, paraffin-embedded tissue sections obtained from the archive of the pathology department, Imam-Khomeini Hospital and Firouzgar hospital. After DNA extraction the genotyping was performed using PCR-RFLP technique. Single nucleotide polymorphisms (SNPs) in adiponectin (rs1063539, rs2241766) and survivin (rs9904341) gene were evaluated in the study. The increased frequency of ADIPOQ rs1063539C allele (CC+CG genotype) was associated with decreased EC risk [OR: 0.39(0.17-0.90)]. Survivin rs9904341C allele (CC+CG genotype) was associated with increased EC risk [crude OR: 2.75(1.27-5.95), adjusted OR: 2.93(1.27-6.76)]. We observed an epistatic interaction between survivin rs9904341 CC+CG genotype and ADIPOQ rs1063539 GG genotype increasing the risk of EC compared to those with other genotypes [OR: 4.86(1.88-12.54), P=0.001]. Our findings indicate that adiponectin might have a modulatory effect on survivin role and function in EC, which requires further investigation.

n-3 polyunsaturated fatty acids and mechanisms to mitigate inflammatory paracrine signaling in obesity-associated breast cancer

Globally, the prevalence of obesity is increasing which subsequently increases the risk of the development of obesity-related chronic diseases. Low-grade chronic inflammation and dysregulated adipose tissue inflammatory mediator/adipokine secretion are well-established in obesity, and these factors increase the risk of developing inflammation-associated cancer. Breast cancer is of particular interest given that increased inflammation within the subcutaneous mammary adipose tissue depot can alter the local tissue inflammatory microenvironment such that it resembles that of obese visceral adipose tissue. Therefore, in obese women with breast cancer, increased inflammatory mediators both locally and systemically can perpetuate inflammation-associated pro-carcinogenic signaling pathways, thereby increasing disease severity. Herein, we discuss some of these inflammation-associated pro-carcinogenic mechanisms of the combined obese breast cancer phenotype and offer evidence that dietary long chain n-3 polyunsaturated fatty acids (PUFA) may have utility in mitigating the severity of obesity-associated inflammation and breast cancer.

Adiponectin as novel regulator of cell proliferation in human glioblastoma

Adiponectin (Acrp30) is an adipocyte-secreted hormone with pleiotropic metabolic effects, whose reduced levels were related to development and progression of several malignancies. We looked at the presence of Acrp30 receptors in human glioblastomas (GBM), hypothesizing a role for Acrp30 also in this untreatable cancer. Here we demonstrate that human GBM express Acrp30 receptors (AdipoR1 and AdipoR2), which are often co-expressed in GBM samples (70% of the analyzed tumors). To investigate the effects of Acrp30 on GBM growth, we used human GBM cell lines U87-MG and U251, expressing both AdipoR1 and AdipoR2 receptors. In these cells, Acrp30 treatment inhibits DNA synthesis and cell proliferation rate, inducing arrest in G1 phase of the cell cycle. These effects were correlated to a sustained activation of ERK1/2 and Akt kinases, upon Acrp30 treatment. Our results suggest that Acrp30 may represent a novel endogenous negative regulator of GBM cell proliferation, to be evaluated for the possible development of novel pharmacological approaches.

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.

SNPs in the adiponectin receptor 2 gene and their associations with chicken performance traits

The adiponectin receptor 2 (ADIPOR2) is a receptor for both globular and full-length adiponectin. In the current study, two genetic variations in ADIPOR2 gene were identified in an F2 resource population of Gushi chicken and Anka broiler. Association analysis between the two SNPs and chicken performance traits were determined using the linear mixed model. The data revealed that the g.34490C > T mutation in intron 3 was significantly associated with liver weight and globulin, the g.35363T > C polymorphism in exon 5 was significantly associated with body weights at 6, 10, and 12 weeks of age. Both polymorphisms have no significant effects on serum glucose and fat-related traits. The g.34490C > T mutation might play an important role in regulating liver weight. The g.35363T > C polymorphism does contribute in a significant manner to growth traits at the medium and later development stage but it is uncertain whether it could be a molecular marker for liver disease.

Adiponectin inhibits neutrophil apoptosis via activation of AMP kinase, PKB and ERK 1/2 MAP kinase

Neutrophils are abundant, short-lived leukocytes that play a key role in the immune defense against microbial infections. These cells die by apoptosis following activation and uptake of microbes and will also enter apoptosis spontaneously at the end of their lifespan if they do not encounter a pathogen. Adiponectin exerts anti-inflammatory effects on neutrophil antimicrobial functions, but whether this abundant adipokine influences neutrophil apoptosis is unknown. Here we report that adiponectin in the physiological range (1–10 μg/ml) reduced apoptosis in resting neutrophils, decreasing caspase-3 cleavage and maintaining Mcl-1 expression by stabilizing this anti-apoptotic protein. We show that adiponectin induced phosphorylation of AMP-activated kinase (AMPK), protein kinase B (PKB), extracellular signal-regulated kinase (ERK 1/2) and p38 mitogen activated protein kinase (MAPK). Pharmacological inhibition of AMPK, PKB and ERK 1/2 ablated the pro-survival effects of adiponectin and treatment of neutrophils with an AMPK specific activator (AICAR) and AMPK inhibitor (compound C) respectively decreased and increased apoptosis. Finally, activation of AMPK by AICAR or adiponectin also decreased ceramide accumulation in the neutrophil cell membrane, a process involved in the early stages of spontaneous apoptosis, giving another possible mechanism downstream of AMPK activation for the inhibition of neutrophil apoptosis.

A test for comparing two groups of samples when analyzing multiple omics profiles

BACKGROUND

A number of statistical models has been proposed for studying the association between gene expression and copy number data in integrated analysis. The next step is to compare association patterns between different groups of samples.

RESULTS

We propose a method, named dSIM, to find differences in association between copy number and gene expression, when comparing two groups of samples. Firstly, we use ridge regression to correct for the baseline associations between copy number and gene expression. Secondly, the global test is applied to the corrected data in order to find differences in association patterns between two groups of samples. We show that dSIM detects differences even in small genomic regions in a simulation study. We also apply dSIM to two publicly available breast cancer datasets and identify chromosome arms where copy number led gene expression regulation differs between positive and negative estrogen receptor samples. In spite of differing genomic coverage, some selected arms are identified in both datasets.

CONCLUSION

We developed a flexible and robust method for studying association differences between two groups of samples while integrating genomic data from different platforms. dSIM can be used with most types of microarray/sequencing data, including methylation and microRNA expression. The method is implemented in R and will be made part of the BioConductor package SIM.

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.

Globular adiponectin and its downstream target genes are up-regulated locally in human colorectal tumors: ex vivo and in vitro studies

OBJECTIVE

Low plasma adiponectin levels are linked to obesity, insulin resistance, and the risk of several types of malignancy. Despite the decline in circulating adiponectin concentrations, the increase in the expression of adiponectin receptors AdipoR1 and AdipoR2 is greater in cancerous than in normal colonic tissue. The purpose of this study was to obtain new information regarding local adiponectin signaling in the pathogenesis of colorectal cancer (CRC).

METHODS

We characterized the expressions of adiponectin and several of its downstream targets in paired samples of tumor tissue and adjacent noncancerous mucosa in 60 surgical patients with colorectal adenocarcinomas.

RESULTS

Adiponectin was expressed in both colorectal tumors and the adjacent mucosa. The expressions of adiponectin mRNA and its globular protein variant (gAd), adiponectin receptor type 1 and 5' AMP-activated protein kinase (AMPK) mRNA were significantly higher in colorectal tumors than in the adjacent mucosa. This finding was accompanied by increased mRNA expression of genes encoding proteins involved in fatty-acid trafficking and oxidation. The potential interference between adiponectin stimulation and AMPK activation through AMPK1 was examined in an in vitro model with the aid of silencing-RNA experiments. Furthermore, AMPK mRNA expression on tumors was positively correlated with a more advanced tumor stage in the patients.

CONCLUSION

We propose that the globular adiponectin-AMPK pathway functions in an autocrine manner in colorectal tumors, explaining some of the beneficial changes in cellular oxidative capacity in tumors in favor of tumorigenesis.

Adiponectin receptor expression predicts favorable prognosis in cases of hepatocellular carcinoma

Obesity influences risk, progression and prognosis of various cancers including hepatocellular carcinoma (HCC). Adipose-tissue-derived adipokines has been considered to be involved in tumorigenesis and adiponecin, one such adipokine, has antiproliferative effect on obesity-related malignancies, though variable signal pathway mediated by adiponectin receptors-AdipoR1 and AdipoR2. In this study, we investigated expression of adiponectin and adiponectin receptors in tumor and non-tumorous hepatic tissues of HCC patients and its clinicopathological significance. We collected 75 HCC tissues and 70 non-tumorous hepatic tissues from HCC patients who underwent surgical resection. The tissue microarrays were constructed and immunohistochemical study for adiponectin, AdipoR1 and AipoR2 was performed. Adiponectin and AdipoR1 expression rates were significantly lower in HCC than non-neoplastic hepatic tissues (82.7 % vs. 97.1 % and 24.0 % vs. 90 %, P = 0.005 and <0.001, respectively). Immunopositivity for adiponectin was associated with small tumor size, low Edmonson-Steiner grade and absence of other organ invasion (P = 0.015, 0.021 and 0.028, respectively). AdipoR1 expression had association with absence of vascular invasion (P = 0.028) and AdipoR2 expression was correlated with lower histologic grade and low pathologic T-stage (P = 0.003 and 0.008, respectively). Cox regression analysis revealed that low expression of AdipoR1 and AdipoR2 were associated with increased risk of recurrence and death, respectively (hazard ration = 3.222 and 14.797, respectively). These findings suggest that loss of adiponectin, and adiponectin receptors expression is associated with aggressive clinicopathological features of HCC and AdipoR1 and AdipoR2 might serve as the independent prognostic factors for HCC patients.

Adiponectin inhibits leptin-induced oncogenic signalling in oesophageal cancer cells by activation of PTP1B

Obesity is characterised by hyperleptinaemia and hypoadiponectinaemia and these metabolic abnormalities may contribute to the progression of several obesity-associated cancers including oesophageal adenocarcinoma (OAC). We have examined the effects of leptin and adiponectin on OE33 OAC cells. Leptin stimulated proliferation, invasion and migration and inhibited apoptosis in a STAT3-dependant manner. Leptin-stimulated MMP-2 secretion in a partly STAT3-dependent manner and MMP-9 secretion via a STAT3-independent pathway. Adiponectin inhibited leptin-induced proliferation, migration, invasion, MMP secretion and reduced the anti-apoptotic effects: these effects of adiponectin were ameliorated by both a non-specific tyrosine phosphatase inhibitor and a specific PTP1B inhibitor. Adiponectin reduced leptin-stimulated JAK2 activation and STAT3 transcriptional activity in a PTP1B-sensitive manner and adiponectin increased both PTP1B protein and activity. We conclude that adiponectin restrains leptin-induced signalling and pro-carcinogenic behaviour by inhibiting the early events in leptin-induced signal transduction by activating PTP1B. Relative adiponectin deficiency in obesity may contribute to the promotion of OAC.

Biochemical and molecular mechanisms for the association between obesity, chronic inflammation, and breast cancer

Upper body obesity is a risk factor for postmenopausal breast cancer and is related to an aggressive tumor phenotype and a poor prognosis regardless of menopausal status. After the menopause, the major mechanism for the association with disease risk is elevated estrogen production by adipose tissue, due to a high level of aromatase activity: these hormone-dependent tumors express both estrogen and progesterone receptors. Other important biological factors of risk include leptin and adiponectin, adipokines with opposing endocrine and paracrine activities, and obesity-related hyperinsulinemia. Chronic inflammation of the breast adipose tissue, which occurs in some obese women and is indicated by the accumulation of macrophages around dead adipocytes ("crown-like structures"), rather than adiposity per se, may prove to be the pathological lesion responsible for both local aromatase induction, and enhanced invasiveness and metastatic capacity through biological mechanisms that involve leptin, tumor necrosis factor-α, and insulin. A causal association between obesity in premenopausal women and breast cell epithelial-mesenchymal transition, perhaps with the participation of the Wnt signaling pathway, and aggressive hormone-independent breast cancer is suggested by a number of experimental and clinical studies.

The role of obesity in gastrointestinal cancer: evidence and opinion

There is increasing recognition of the impact of being overweight and obese on the development of cancers at diverse sites including the gastrointestinal tract. Large epidemiological studies indicate that up to 14% of tumours may be related to obesity. Pathophysiological mechanisms underpinning this association are not well understood and so are discussed in this review.

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.

Leptin and adiponectin: emerging therapeutic targets in breast cancer

Obesity is a recognized risk factor for breast cancer development and poorer response to therapy. Two major fat tissue-derived adipokines, leptin and adiponectin have been implicated in mammary carcinogenesis. Leptin appears to promote breast cancer progression through activation of mitogenic, antiapoptotic, and metastatic pathways, while adiponectin may restrict tumorigenic processes primarily by inhibiting cell metabolism. Furthermore, adiponectin is known to counteract detrimental leptin effects in breast cancer models. Thus, therapeutic inhibition of pro-neoplastic leptin pathways and reactivation of anti-neoplastic adiponectin signaling may benefit breast cancer patients, especially the obese subpopulation. This review focuses on current experimental strategies aiming at leptin and adiponectin pathways in breast cancer models. Novel leptin receptor antagonists and adiponectin receptor agonists as well as other compounds for therapeutic modulation of adipokine pathways are discussed in detail, including potential pharmacological advantages and limitations of these approaches.

Role of adipokines and cytokines in obesity-associated breast cancer: therapeutic targets

Obesity is the cause of a large proportion of breast cancer incidences and mortality in post-menopausal women. In obese people, elevated levels of various growth factors such as insulin and insulin-like growth factors (IGFs) are found. Elevated insulin level leads to increased secretion of estrogen by binding to the circulating sex hormone binding globulin (SHBG). The increased estrogen-mediated downstream signaling favors breast carcinogenesis. Obesity leads to altered expression profiles of various adipokines and cytokines including leptin, adiponectin, IL-6, TNF-α and IL-1β. The increased levels of leptin and decreased adiponectin secretion are directly associated with breast cancer development. Increased levels of pro-inflammatory cytokines within the tumor microenvironment promote tumor development. Efficacy of available breast cancer drugs against obesity-associated breast cancer is yet to be confirmed. In this review, we will discuss different adipokine- and cytokine-mediated molecular signaling pathways involved in obesity-associated breast cancer, available therapeutic strategies and potential therapeutic targets for obesity-associated breast cancer.

Underactivation of the adiponectin-adiponectin receptor 1 axis in clear cell renal cell carcinoma: implications for progression

Energy-sensing pathways, normally coordinated by 5' AMP-activated protein kinase (AMPK), are dysregulated in renal cell carcinoma (RCC). Obesity can accentuate the pre-existing pro-tumorigenic metabolic machinery in RCC cells through its associated obesogenic hormonal milieu, characterized by lower circulating levels of adiponectin. In RCC patients, low adiponectin levels associate clinically with more aggressive disease. We investigated the adiponectin signaling pathway in RCC, focusing on adiponectin receptor 1 (AdipoR1) and associated activation of AMPK. AdipoR1 protein in RCC and normal surrounding renal tissues was determined by Western blot analysis and immunohistochemistry. Anti-tumorigenic effects of adiponectin in RCC cells in vitro were investigated via VEGF and MMP ELISA and invasion assays. Using in vivo models of RCC, the effect of AdipoR1-knockdown (shRNA) on tumor latency, growth and dissemination were determined. AdipoR1 protein was significantly reduced in clear cell RCC specimens. Adiponectin treatment inhibited VEGF, MMP-2 and MMP-9 secretion and activity and invasive and migratory capacities of RCC cells. AMPKα1-knockdown (shRNA) attenuated adiponectin's effects. In cells stably expressing AdipoR1-specific shRNA, AMPK activation by adiponectin was significantly reduced compared to cells expressing control shRNA. In vivo, AdipoR1 knockdown increased the growth, dissemination and angiogenesis of RCC. These findings suggest that deficiencies in the entire adiponectin hormonal axis (the hormone and its receptor) result in underactivation of AMPK leading to increased angiogenic and invasive capacities of RCC. The established link between obesity and RCC can therefore be further explained by the adiponectin deficiency in obese individuals together with reduced AdipoR1 protein in RCC.

Weight control, endocrine hormones and cancer prevention

The prevalence of obesity is increasing which becomes worrisome due to its association with several diseases and certain types of cancers. While weight control through dietary caloric restriction and/or physical activity protects against cancer in animal models, the underlying mechanisms are not fully defined. Weight loss due to negative energy balance is associated with alterations of multiple growth factors and endocrine hormones. The altered hormones and hormone-related functions appear to be responsible for anti-cancer mechanisms. In this review, we summarize the recent studies related to weight loss and the altered endocrine hormones, focusing on the reduced levels of the mitogenic insulin-like growth factor 1 (IGF-1) and adipokine leptin as well as the raised levels of adiponectin and glucocorticoids. The potential molecular targets of these hormone-dependent signalling pathways are also discussed. Considering the increasing trends of obesity throughout the world, a better understanding of the underlying mechanisms between body weight, endocrine hormones and cancer risk may lead to novel approaches to cancer prevention and treatment.

Prediagnostic leptin, adiponectin, C-reactive protein, and the risk of postmenopausal breast cancer

Obesity has been associated with an increased risk of postmenopausal breast cancer. Adipokines and systemic inflammation have been hypothesized to underlie this association. In a case-control study nested within the Multiethnic Cohort, conditional logistic regression was used to calculate the ORs and 95% confidence intervals (CI) for postmenopausal breast cancer associated with prediagnostic levels of serum leptin, adiponectin, the leptin:adiponectin ratio, and C-reactive protein (CRP). The 706 cases and 706 controls were matched on ethnicity, location (Hawaii or Los Angeles), birth year, date and time of blood draw, hours fasting before blood draw, and hormone replacement therapy use at blood draw. Higher circulating levels of leptin [ORQ4 vs. Q1, 1.94 (1.37-2.75); Ptrend ≤ 0.001), the leptin:adiponectin ratio [OR, 1.91 (1.36-2.68); Ptrend = 0.005], and CRP [OR, 1.41 (1.01-1.96); Ptrend = 0.014] were associated with an increased risk of postmenopausal breast cancer. The positive associations for these markers remained after adjustment for body mass index (BMI). No associations were detected for adiponectin. These data suggest that adipokines and systemic inflammation may be associated with the risk of postmenopausal breast cancer independently of BMI. Further prospective studies examining the role of adipokines and inflammatory processes in the etiology of postmenopausal breast cancer are warranted. Cancer Prev Res; 6(3); 188-95. ©2013 AACR.

Expression of adiponectin receptor 1 is indicative of favorable prognosis in non-small cell lung carcinoma

Lung cancer is a major cause of cancer-related death worldwide. It is believed that obesity-related malignancies such as breast, endometrial, colorectal, and kidney carcinomas have lower plasma level and/or tissue expression of adiponectin receptors. However, the association between adiponectin receptors and lung cancer, a non obesity-related malignancy, is still unknown. We evaluated the tissue expression of adiponectin receptor (AdipoR) 1 and AdipoR2 in 83 cases of non-small cell lung carcinoma (NSCLC) and matched non-neoplastic lung tissues by immunohistochemistry and real-time polymerase chain reaction (PCR). Clinicopathological data, including smoking history, smoker's bronchiolitis, emphysema, lymph node metastasis, and T-stage were collected and evaluated. Expression of immunohistochemically stained AdipoR1 and AdipoR2 was observed in all samples of non-neoplastic lung tissues. Both receptors showed higher mRNA expression in non-neoplastic than neoplastic tissues (p < 0.05). In NSCLC tissues, AdipoR1 immunohistochemical expression was not observed in most of patients with squamous cell carcinoma and current smoking history (31/42, p = 0.04 and 25/29, p = 0.003, respectively). Additionally, AdipoR1 mRNA expression was significantly lower in patients with lymph node metastasis (p = 0.05). Meanwhile, AdipoR2 immunohistochemical stain expression was inversely correlated with T-stage (p = 0.05) and AdipoR2 mRNA expression was significantly lower in patients with smoker's bronchiolitis (p = 0.01) and emphysema (p = 0.03). Patients with expression of AdipoR1 had longer overall survival. AdipoR2 expression was not correlated with patients' survival. In conclusion, we suggest that expression of AdipoR1 is indicative of favorable prognosis and may be used as prognostic marker in NSCLC.

A Saccharomyces cerevisiae assay system to investigate ligand/AdipoR1 interactions that lead to cellular signaling

Adiponectin is a mammalian hormone that exerts anti-diabetic, anti-cancer and cardioprotective effects through interaction with its major ubiquitously expressed plasma membrane localized receptors, AdipoR1 and AdipoR2. Here, we report a Saccharomyces cerevisiae based method for investigating agonist-AdipoR interactions that is amenable for high-throughput scale-up and can be used to study both AdipoRs separately. Agonist-AdipoR1 interactions are detected using a split firefly luciferase assay based on reconstitution of firefly luciferase (Luc) activity due to juxtaposition of its N- and C-terminal fragments, NLuc and CLuc, by ligand induced interaction of the chimeric proteins CLuc-AdipoR1 and APPL1-NLuc (adaptor protein containing pleckstrin homology domain, phosphotyrosine binding domain and leucine zipper motif 1-NLuc) in a S. cerevisiae strain lacking the yeast homolog of AdipoRs (Izh2p). The assay monitors the earliest known step in the adiponectin-AdipoR anti-diabetic signaling cascade. We demonstrate that reconstituted Luc activity can be detected in colonies or cells using a CCD camera and quantified in cell suspensions using a microplate reader. AdipoR1-APPL1 interaction occurs in absence of ligand but can be stimulated specifically by agonists such as adiponectin and the tobacco protein osmotin that was shown to have AdipoR-dependent adiponectin-like biological activity in mammalian cells. To further validate this assay, we have modeled the three dimensional structures of receptor-ligand complexes of membrane-embedded AdipoR1 with cyclic peptides derived from osmotin or osmotin-like plant proteins. We demonstrate that the calculated AdipoR1-peptide binding energies correlate with the peptides’ ability to behave as AdipoR1 agonists in the split luciferase assay. Further, we demonstrate agonist-AdipoR dependent activation of protein kinase A (PKA) signaling and AMP activated protein kinase (AMPK) phosphorylation in S. cerevisiae, which are homologous to important mammalian adiponectin-AdipoR1 signaling pathways. This system should facilitate the development of therapeutic inventions targeting adiponectin and/or AdipoR physiology.

The relationship between visceral obesity and colorectal cancer

SUMMARY The prevalence of obesity continues to rise globally and physicians and healthcare systems have to prepare for rising rates of obesity-associated disease. Aside from cardiovascular disease and diabetes, recent evidence suggests a strong association between obesity and the development of cancer, including colorectal cancer. Using BMI as a marker for obesity, excess body fat is associated with an increased risk of colorectal cancer; however, this relationship appears to be stronger among males and more consistent for colon rather than rectal cancer. Epidemiologic literature evaluating the risk of obesity on colorectal cancer survival using BMI is less consistent. Recent evidence suggests that visceral fat plays a greater role in the development of disease. Current research on the effect of visceral obesity on colorectal cancer outcomes is in its infancy, but may drive a new wave of practice for this ever-growing population of colorectal cancer patients.

Adiponectin pathway polymorphisms and risk of breast cancer in African Americans and Hispanics in the Women's Health Initiative

Adiponectin, a protein secreted by the adipose tissue, is an endogenous insulin sensitizer with circulating levels that are decreased in obese and diabetic subjects. Recently, circulating levels of adiponectin have been correlated with breast cancer risk. Our previous work showed that polymorphisms of the adiponectin pathway are associated with breast cancer risk. We conducted the first study of adiponectin pathways in African Americans and Hispanics in the Women's Health Initiative SNP Health Association Resource cohort of 3,642 self-identified Hispanic women and 8,515 self-identified African American women who provided consent for DNA analysis. Single nucleotide polymorphisms (SNPs) from three genes were included in this analysis: ADIPOQ, ADIPOR1, and ADIPOR2. The genome-wide human SNP array 6.0 (909,622 SNPs) ( www.affymetrix.com ) was used. We found that rs1501299, a functional SNP of ADIPOQ that we previously reported was associated with breast cancer risk in a mostly Caucasian population, was also significantly associated with breast cancer incidence (HR for the GG/TG genotype: 1.23; 95 % CI 1.059-1.43) in African American women. We did not find any other SNPs in these genes to be associated with breast cancer incidence. This is the first study assessing the role of adiponectin pathway SNPs in breast cancer risk in African Americans and Hispanics. RS1501299 is significantly associated with breast cancer risk in African American women. As the rates of obesity and diabetes increase in African Americans and Hispanics, adiponectin and its functional SNPs may aid in breast cancer risk assessment.

Role of adiponectin and its receptors in cancer

Adiponectin (APN), a novel hormone/cytokine derived from adipocyte tissue, is involved in various physiological functions. Genetics, nutrition, and adiposity are factors contributing to circulating plasma concentrations of APN. Clinical correlation studies have shown that lower levels of serum APN are associated with increased malignancy of various cancers, such as breast and colon cancers, suggesting that APN has a role in tumorigenesis. APN affects insulin resistance, thus further influencing cancer development. Tumor cells may express receptors for APN. Cellular signaling is the mechanism by which APN exerts its host-protective responses. These factors suggest that serum APN levels and downstream signaling targets of APN may serve as potential diagnostic markers for malignancies. Further research is necessary to clarify the exact role of APN in cancer diagnosis and therapy.

Identification of adiponectin receptor agonist utilizing a fluorescence polarization based high throughput assay

Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (-)-arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases.