Growth-inhibitory effect of adiponectin via adiponectin receptor 1 on human breast cancer cells through inhibition of S-phase entry without inducing apoptosis

Immunological roles for resistin and related adipokines in obesity-associated tumors

Rationale Obesity is an independent risk factor for the occurrence and development of tumors. Obesity is influenced by signaling of adipokines, which are secreted factors from adipocytes and resident immune cells within adipose tissues that mediate lipid metabolism. More recently, adipokines have been implicated in chronic inflammation as well as in tumor formation and growth. Among them, resistin has received increasing attention in research related to the growth and expansion of solid tumors and hematological cancers through various signaling pathways. Objective and findings We reviewed the physiological, biochemical, and immune functions of adipose tissue, with a focus on the structure and expression of resistin and adipokines within multiple adipose cell types, their signaling pathways and putative effects on tumor cells, as well as their in vivo regulation. Current evidence indicates that adipokines such as resistin act as pro-inflammatory factors to stimulate immune cells which, in turn, promotes tumor angiogenesis, connective tissue proliferation, and matrix fibrosis. Concurrently, in states of metabolic dysfunction and lipotoxicity in obese individuals, the numbers and functions of immune cells are compromised, leading to an immunosuppressive environment that fosters tumor cell survival and weak cancer immune monitoring. Conclusion Adipokines such as resistin are important to the development of obesity-related tumors. Clarifying the roles for obesity-related factors in immune regulation and tumor progression may lead to the discovery of novel anti-tumor strategies for targeting obesity factors such as resistin to limit tumor growth and manage obesity, or both.

Adiponectin Receptor Agonist Effectively Suppresses Hepatocellular Carcinoma Growth

Hepatocellular carcinoma (HCC) is the second lethal cancer. Short overall survival, low five-year survival rate, and unimproved treatment efficacy urge the need to improve HCC prognosis. Adiponectin is key protector against cancer and hepatic abnormalities. Hypoadiponectinemia occurs in and promotes carcinogenesis and hepatic diseases. Adiponectin reactivation by different methods showed impressive effect against cancer and hepatic diseases. Recently, AdipoRon, an adiponectin receptor agonist, can interact with both Adiponectin receptors. AdipoRon showed promising anti-cancer effect in some cancers, but no study on HCC yet. The in vitro effect of AdipoRon on HCC was investigated by cell viability, migration, invasion, colony formation and apoptosis assays. The signalling alteration was determined by RT-qPCR and Western blot. The effect of treatment was interpreted by comparison between treatments and control. The difference between two cell lines was relatively compared. Our results showed significant in vitro anti-cancer effect of AdipoRon via AMPK- and dose-dependent manner. Huh7 cells showed a lower level of AdipoR1/2 and a superior proliferation and aggressiveness, compared to Hep3B. In addition, Huh7 cells were more sensitive to AdipoRon treatment (lower IC50, less cell growth, migration, invasion and colonies upon AdipoRon treatment) than Hep3B cells. In conclusion, AdipoRon effectively inhibited HCC growth and invasiveness in vitro. The deficient expression of adiponectin receptors affects efficacy of AdipoRon and aggressiveness of HCC cells.

Obesity-Associated Breast Cancer: Analysis of Risk Factors and Current Clinical Evaluation

Several studies show that a significantly stronger association is obvious between increased body mass index (BMI) and higher breast cancer incidence. Additionally, obese and postmenopausal women are at higher risk of all-cause and breast cancer-specific mortality compared with non-obese women with breast cancer. In this context, increased levels of estrogens, excessive aromatization activity of the adipose tissue, overexpression of pro-inflammatory cytokines, insulin resistance, adipocyte-derived adipokines, hypercholesterolemia, and excessive oxidative stress contribute to the development of breast cancer in obese women. Genetic evaluation is an integral part of diagnosis and treatment for patients with breast cancer. Despite trimodality therapy, the four-year cumulative incidence of regional recurrence is significantly higher. Axillary lymph nodes as well as primary lesions have diagnostic, prognostic, and therapeutic significance for the management of breast cancer. In clinical setting, because of the obese population primary lesions and enlarged lymph nodes could be less palpable, the diagnosis may be challenging due to misinterpretation of physical findings. Thereby, a nomogram has been created as the "Breast Imaging Reporting and Data System" (BI-RADS) to increase agreement and decision-making consistency between mammography and ultrasonography (USG) experts. Additionally, the "breast density classification system," "artificial intelligence risk scores," ligand-targeted receptor probes," "digital breast tomosynthesis," "diffusion-weighted imaging," "18F-fluoro-2-deoxy-D-glucose positron emission tomography," and "dynamic contrast-enhanced magnetic resonance imaging (MRI)" are important techniques for the earlier detection of breast cancers and to reduce false-positive results. A high concordance between estrogen receptor (ER) and progesterone receptor (PR) status evaluated in preoperative percutaneous core needle biopsy and surgical specimens is demonstrated. Breast cancer surgery has become increasingly conservative; however, mastectomy may be combined with any axillary procedures, such as sentinel lymph node biopsy (SLNB) and/or axillary lymph node dissection whenever is required. As a rule, SLNB-guided axillary dissection in breast cancer patients who have clinically axillary lymph node-positive to node-negative conversion following neoadjuvant chemotherapy is recommended, because lymphedema is the most debilitating complication after any axillary surgery. There is no clear consensus on the optimal treatment of occult breast cancer, which is much discussed today. Similarly, the current trend in metastatic breast cancer is that the main palliative treatment option is systemic therapy.

Beyond Body Size: Adiponectin as a Key Player in Obesity-Driven Cancers

Obesity, a complex and multifactorial disease influenced by genetic, environmental, and psychological factors, has reached epidemic proportions globally, posing a significant health challenge. In addition to its established association with cardiovascular disease and type II diabetes, obesity has been implicated as a risk factor for various cancers. However, the precise biological mechanisms linking obesity and cancer remain largely understood. Adipose tissue, an active endocrine organ, produces numerous hormones and bioactive molecules known as adipokines, which play a crucial role in metabolism, immune responses, and systemic inflammation. Notably, adiponectin (APN), the principal adipocyte secretory protein, exhibits reduced expression levels in obesity. In this scoping review, we explore and discuss the role of APN in influencing cancer in common malignancies, including lung, breast, colorectal, prostate, gastric, and endometrial cancers. Our review aims to emphasize the critical significance of investigating this field, as it holds great potential for the development of innovative treatment strategies that specifically target obesity-related malignancies. Furthermore, the implementation of more rigorous and comprehensive prevention and treatment policies for obesity is imperative in order to effectively mitigate the risk of associated diseases, such as cancer.

Unraveling the Role of Adiponectin Receptors in Obesity-Related Breast Cancer

Obesity has a noteworthy role in breast tumor initiation and progression. Among the mechanisms proposed, the most validated is the development of chronic low-grade inflammation, supported by immune cell infiltration along with dysfunction in adipose tissue biology, characterized by an imbalance in adipocytokines secretion and alteration of their receptors within the tumor microenvironment. Many of these receptors belong to the seven-transmembrane receptor family, which are involved in physiological features, such as immune responses and metabolism, as well as in the development and progression of several malignancies, including breast cancer. These receptors are classified as canonical (G protein-coupled receptors, GPCRs) and atypical receptors, which fail to interact and activate G proteins. Among the atypical receptors, adiponectin receptors (AdipoRs) mediate the effect of adiponectin, the most abundant adipocytes-derived hormone, on breast cancer cell proliferation, whose serum levels are reduced in obesity. The adiponectin/AdipoRs axis is becoming increasingly important regarding its role in breast tumorigenesis and as a therapeutic target for breast cancer treatment. The objectives of this review are as follows: to point out the structural and functional differences between GPCRs and AdipoRs, and to focus on the effect of AdipoRs activation in the development and progression of obesity-dependent breast cancer.

Targeting Adiponectin in Breast Cancer

Obesity and breast cancer are two major health issues that could be categorized as sincere threats to human health. In the last few decades, the relationship between obesity and cancer has been well established and extensively investigated. There is strong evidence that overweight and obesity increase the risk of postmenopausal breast cancer, and adipokines are the central players in this relationship. Produced and secreted predominantly by white adipose tissue, adiponectin is a bioactive molecule that exhibits numerous protective effects and is considered the guardian angel of adipokine. In the obesity-cancer relationship, more and more evidence shows that adiponectin may prevent and protect individuals from developing breast cancer. Recently, several updates have been published on the implication of adiponectin in regulating tumor development, progression, and metastases. In this review, we provide an updated overview of the metabolic signaling linking adiponectin and breast cancer in all its stages. On the other hand, we critically summarize all the available promising candidates that may reactivate these pathways mainly by targeting adiponectin receptors. These molecules could be synthetic small molecules or plant-based proteins. Interestingly, the advances in genomics have made it possible to create peptide sequences that could specifically replace human adiponectin, activate its receptor, and mimic its function. Thus, the obvious anti-cancer activity of adiponectin on breast cancer should be better exploited, and adiponectin must be regarded as a serious biomarker that should be targeted in order to confront this threatening disease.

Role of Adiponectin Peptide I (APNp1) in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disease that can cause central vision loss, particularly in the elderly population. There are 2 classes of AMD, wet-type and dry-type. Wet-type involves excess angiogenesis around the macula, referred to as choroidal neovascularization (CNV). This can result in leaky vessels, often causing more severe vision loss than dry-type AMD. Adiponectin peptide 1 (APNp1) has been shown to slow the progression of CNV. Here, we used a mouse model and FITC-labeled APNp1 to determine if APNp1 could be delivered effectively as an eye drop. Our experiment revealed that topically applied FITC-APNp1 could reach the macula of the eye, which is crucial for treating wet-type AMD. We also tested delivery of APNp1 via injection of an adeno-associated virus (AAV) vector in a mouse model of CNV. AAV is a harmless virus easy to manipulate and is very often used for protein or peptide deliveries. Results revealed an increase in the expression of APNp1 in the retina and choroid over a 28-day period. Finally, we investigated the mechanism by which APNp1 affects CNV by examining the expression of adiponectin receptor 1 (AdipoR1) and proliferating cell nuclear antigen (PCNA) in the retinal and choroidal tissue of the mouse eyes. AdipoR1 and PCNA were overexpressed in these tissues in mice with laser-induced CNV compared to naïve mice. Based on our data shown here, we think it will enhance our understanding of APNp1 as a therapeutic agent for wet-type AMD and possible treatment alternatives that could be more beneficial for patients.

Targeting obesity-related dysfunction in hormonally driven cancers

Obesity is a risk factor for at least 13 different types of cancer, many of which are hormonally driven, and is associated with increased cancer incidence and morbidity. Adult obesity rates are steadily increasing and a subsequent increase in cancer burden is anticipated. Obesity-related dysfunction can contribute to cancer pathogenesis and treatment resistance through various mechanisms, including those mediated by insulin, leptin, adipokine, and aromatase signalling pathways, particularly in women. Furthermore, adiposity-related changes can influence tumour vascularity and inflammation in the tumour microenvironment, which can support tumour development and growth. Trials investigating non-pharmacological approaches to target the mechanisms driving obesity-mediated cancer pathogenesis are emerging and are necessary to better appreciate the interplay between malignancy, adiposity, diet and exercise. Diet, exercise and bariatric surgery are potential strategies to reverse the cancer-promoting effects of obesity; trials of these interventions should be conducted in a scientifically rigorous manner with dose escalation and appropriate selection of tumour phenotypes and have cancer-related clinical and mechanistic endpoints. We are only beginning to understand the mechanisms by which obesity effects cell signalling and systemic factors that contribute to oncogenesis. As the rates of obesity and cancer increase, we must promote the development of non-pharmacological lifestyle trials for the treatment and prevention of malignancy.

The effect of caloric restriction and fasting on cancer

Cancer is one of the most frequent causes of worldwide death and morbidity and is a major public health problem. Although, there are several widely used treatment methods including chemo-, immune- and radiotherapies, these mostly lack sufficient efficiency and induce toxicities in normal surrounding tissues. Thus, finding new approaches to mitigate side effects and potentially accelerate treatment is paramount. In line with this, increasing preclinical evidence indicates that caloric restriction (CR) and fasting might have anticancer effects by reducing tumor progression, enhancing death of cancer cells, and elevating the effectiveness and tolerability of chemo- and radiotherapies. Nonetheless, clinical studies assessing the potential of CR and fasting in cancer are scarce and inconsistent, and more investigations are still required to clarify their effect in different aspects of cancer treatment. In this review, we have summarized the findings of preclinical and clinical studies of CR and fasting with respect to efficacy and on the adverse effects of standard cancer treatments.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

IMPACT

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

Obesity and Androgen Receptor Signaling: Associations and Potential Crosstalk in Breast Cancer Cells

Obesity is an increasing health challenge and is recognized as a breast cancer risk factor. Although obesity-related breast cancer mechanisms are not fully understood, this association has been linked to impaired hormone secretion by the dysfunctional obese adipose tissue (hyperplasic and hypertrophic adipocytes). Among these hormones, altered production of androgens and adipokines is observed, and both, are independently associated with breast cancer development. In this review, we describe and comment on the relationships reported between these factors and breast cancer, focusing on the biological associations that have helped to unveil the mechanisms by which signaling from androgens and adipokines modifies the behavior of mammary epithelial cells. Furthermore, we discuss the potential crosstalk between the two most abundant adipokines produced by the adipose tissue (adiponectin and leptin) and the androgen receptor, an emerging marker in breast cancer. The identification and understanding of interactions among adipokines and the androgen receptor in cancer cells are necessary to guide the development of new therapeutic approaches in order to prevent and cure obesity and breast cancer.

Anti-Proliferative Activity of Glucagon-Like Peptide-1 Receptor Agonist on Obesity-Associated Breast Cancer: The Impact on Modulating Adipokines' Expression in Adipocytes and Cancer Cells

Obesity is associated with high risk and poor prognosis of breast cancer (BC). Obesity promotes BC cells proliferation via modulating the production of adipokines, including adiponectin (anti-neoplastic adipokine), leptin (carcinogenic adipokine) and inflammatory mediators. In the present study we investigated the anti-proliferative effects of liraglutide (LG; anti-diabetic and weight reducing drug) on MCF-7 human BC cells cultured in obese adipose tissue-derived stem cells-conditioned medium (ADSCs-CM) and whether this effect is mediated via modulating the adipokines in ADSCs and cancer cells. Proliferation was investigated using AlamarBlue viability test, colony forming assay and cell cycle analysis. Levels and expression of adipokines and their receptors were assayed using ELISA and RT-PCR. LG caused 48% inhibition of MCF-7 proliferation in obese ADSCs-CM, reduced the colony formation and induced G0/G1 phase arrest. LG also decreased the levels of inflammatory mediators, suppressed the expression of leptin, while increased mRNA levels of adiponectin and their receptors in obese ADSCs and cancer cells cultured in obese ADCSs-CM. In conclusion, LG could mitigate BC cell growth in obese subjects; therefore it could be used for clinical prevention and/or treatment of BC in obese subjects. It may assist to improve treatment outcomes and, reduce the mortality rate in obese patients with BC.

Another Weapon against Cancer and Metastasis: Physical-Activity-Dependent Effects on Adiposity and Adipokines

Physically active behavior has been associated with a reduced risk of developing certain types of cancer and improved psychological conditions for patients by reducing anxiety and depression, in turn improving the quality of life of cancer patients. On the other hand, the correlations between inactivity, sedentary behavior, and overweight and obesity with the risk of development and progression of various cancers are well studied, mainly in middle-aged and elderly subjects. In this article, we have revised the evidence on the effects of physical activity on the expression and release of the adipose-tissue-derived mediators of low-grade chronic inflammation, i.e., adipokines, as well as the adipokine-mediated impacts of physical activity on tumor development, growth, and metastasis. Importantly, exercise training may be effective in mitigating the side effects related to anti-cancer treatment, thereby underlining the importance of encouraging cancer patients to engage in moderate-intensity activities. However, the strong need to customize and adapt exercises to a patient’s abilities is apparent. Besides the preventive effects of physically active behavior against the adipokine-stimulated cancer risk, it remains poorly understood how physical activity, through its actions as an adipokine, can actually influence the onset and development of metastases.

Leptin, Leptin Receptor, KHDRBS1 (KH RNA Binding Domain Containing, Signal Transduction Associated 1), and Adiponectin in Bone Metastasis from Breast Carcinoma: An Immunohistochemical Study

Breast cancer patients are at a high risk of complications from bone metastasis. Molecular characterization of bone metastases is essential for the discovery of new therapeutic targets. Here, we investigated the expression and the intracellular distribution of KH RNA binding domain containing, signal transduction associated 1 (KHDRBS1), leptin, leptin receptor (LEPR), and adiponectin in bone metastasis from breast carcinoma and looked for correlations between the data. The expression of these proteins is known in breast carcinoma, but it has not been investigated in bone metastatic tissue to date. Immunohistochemical analysis was carried out on bone metastasis specimens, then semiquantitative evaluation of the results and the Pearson test were performed to determine eventual correlations. KHDRBS1 expression was significantly higher in the nuclei than in the cytosol of metastatic cells; LEPR was prevalently observed in the cytosol and the nuclei; leptin and adiponectin were found in metastatic cells and stromal cells; the strongest positive correlation was between nuclear KHDRBS1 and nuclear LEPR expression. Taken together, our findings support the importance of the leptin/LEPR/KHDRBS1 axis and of adiponectin in the progression of bone metastasis and suggest their potential application in pharmacological interventions.

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

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

Leptin, Adiponectin, and Sam68 in Bone Metastasis from Breast Cancer

The most serious aspect of neoplastic disease is the spread of cancer cells to secondary sites. Skeletal metastases can escape detection long after treatment of the primary tumour and follow-up. Bone tissue is a breeding ground for many types of cancer cells, especially those derived from the breast, prostate, and lung. Despite advances in diagnosis and therapeutic strategies, bone metastases still have a profound impact on quality of life and survival and are often responsible for the fatal outcome of the disease. Bone and the bone marrow environment contain a wide variety of cells. No longer considered a passive filler, bone marrow adipocytes have emerged as critical contributors to cancer progression. Released by adipocytes, adipokines are soluble factors with hormone-like functions and are currently believed to affect tumour development. Src-associated in mitosis of 68 kDa (Sam68), originally discovered as a protein physically associated with and phosphorylated by c-Src during mitosis, is now recognised as an important RNA-binding protein linked to tumour onset and progression of disease. Sam68 also regulates splicing events and recent evidence reports that dysregulation of these events is a key step in neoplastic transformation and tumour progression. The present review reports recent findings on adipokines and Sam68 and their role in breast cancer progression and metastasis.

Adiponectin inhibits the differentiation and maturation of osteoclasts via the mTOR pathway in multiple myeloma

The present study sought to investigate the correlation between adipose cytokines (visfatin, leptin and adiponectin) and markers of multiple myeloma bone disease, and to determine the effects and mechanism of action of adiponectin on the differentiation and maturation of osteoclasts in multiple myeloma (MM). The levels of visfatin, leptin and adiponectin were measured. Their association with the indices of myeloma tumor load and bone disease were analyzed. Reverse transcription-quantitative PCR was used to detect the expression of receptor activator of nuclear factor-κB ligand (RANKL), osteoclast associated Ig-like receptor (OSCAR), tartrate-resistant acid phosphatase (TRAP) and Cathepsin K genes. Flow cytometry was used to detect the expression of adiponectin receptor 1 (AdipoR1) and the phosphorylation of the mechanistic target of rapamycin kinase (mTOR) pathway-associated proteins mTOR and eukaryotic translation initiation factor 4E-binding protein (4EBP1). There were no significant correlations among leptin, visfatin and the indexes of myeloma tumor load and bone disease. Serum adiponectin levels were significantly lower in patients with newly diagnosed multiple myeloma compared with healthy volunteers (12.37±3.13 vs. 13.80±0.95; P<0.05). The number of mature osteoclasts in the adiponectin group was lower compared with in the control group. Adiponectin also inhibited the mRNA expression of the osteoclast-associated factors RANKL, OSCAR, TRAP and Cathepsin K. Comparison between the non-adiponectin group and the adiponectin group revealed that adiponectin increased the expression of AdipoR1 on the surface of osteoclast precursor cells (26.21±4.27% vs. 29.86±6.23%; P<0.05) and reduced the expression of phosphorylated (p-)mTOR (7.89±1.00% vs. 5.91±1.26%; P<0.05) and p-4EBP1 (26.78±5.00% vs. 22.49±4.24%; P<0.05). The p-mTOR and p-4EBP1 levels in the adiponectin + MHY1485 (an mTOR signaling pathway-specific agonist) group were significantly higher compared with those in the adiponectin group. It was revealed that adiponectin may inhibit osteoclast differentiation and maturation via the mTOR pathway. In conclusion, adiponectin inhibits the differentiation and maturation of osteoclasts by increasing the expression of AdipoR1 and reducing the phosphorylation levels of mTOR and 4EBP1 in patients with MM.

AdipoRon Affects Cell Cycle Progression and Inhibits Proliferation in Human Osteosarcoma Cells

AdipoRon (AdipoR) is the first synthetic molecule acting as a selective and potent adiponectin receptor agonist. Recently, the possible pharmacological use of AdipoR in different pathological conditions has been addressed. Interestingly, initial evidence suggests that AdipoR may have anticancer properties in different preclinical models, such as pancreatic and ovarian cancer. To our knowledge, so far no research has been directed at determining the impact of AdipoR on osteosarcoma, the most aggressive and metastatic bone malignancy occurring in childhood and adolescence age. Here, we investigate the possible antitumor effects of AdipoR in osteosarcoma cell lines. MTT and cell growth curve assays clearly indicate that AdipoR inhibits, at different extents, proliferation in both U2OS and Saos-2 osteosarcoma cell lines, the latter being more sensitive. Moreover, flow cytometry-based assays point out a significant G0/G1 phase accumulation and a contemporary S phase decrease in response to AdipoR. Consistent with the different sensitivity, a strong subG1 appearance in Saos-2 after 48 and 72 hours of treatment is also observed. The investigation of the molecular mechanisms highlights a common and initial ERK1/2 activation in response to AdipoR in both Saos-2 and U2OS cells. Interestingly, a simultaneous and dramatic downregulation of p70S6K phosphorylation, one of the main targets of mTORC1 pathway, has also been observed in AdipoR-treated Saos-2, but not in U2OS cells. Importantly, a strengthening of AdipoR-induced effects was reported upon everolimus-mediated mTORC1 perturbation in U2OS cells. In conclusion, our findings provide initial evidence of AdipoR as an anticancer molecule differently affecting various signaling pathways involved in cell cycle and cell death in osteosarcoma cells and encourage the design of future studies to further understand its pattern of activities.

Interfering Role of ERα on Adiponectin Action in Breast Cancer

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

The Role of Adipokines in Breast Cancer: Current Evidence and Perspectives

PURPOSE

The current review shows evidence for the role of adipokines in breast cancer (BC) pathogenesis summarizing the mechanisms underlying the association between adipokines and breast malignancy. Special emphasis is given also on intriguing insights into the relationship between obesity and BC as well as on the role of novel adipokines in BC development.

RECENT FINDINGS

Recent evidence has underscored the role of the triad of obesity, insulin resistance, and adipokines in postmenopausal BC. Adipokines exert independent and joint effects on activation of major intracellular signal networks implicated in BC cell proliferation, growth, survival, invasion, and metastasis, particularly in the context of obesity, considered a systemic endocrine dysfunction characterized by chronic inflammation. To date, more than 10 adipokines have been linked to BC, and this catalog is continuously increasing. The majority of circulating adipokines, such as leptin, resistin, visfatin, apelin, lipocalin 2, osteopontin, and oncostatin M, is elevated in BC, while some adipokines such as adiponectin and irisin (adipo-myokine) are generally decreased in BC and considered protective against breast carcinogenesis. Further evidence from basic and translational research is necessary to delineate the ontological role of adipokines and their interplay in BC pathogenesis. More large-scale clinical and longitudinal studies are awaited to assess their clinical utility in BC prognosis and follow-up. Finally, novel more effective and safer adipokine-centered therapeutic strategies could pave the way for targeted oncotherapy.

Effects of two types of energy restriction on methylation levels of adiponectin receptor 1 and leptin receptor overlapping transcript in a mouse mammary tumour virus-transforming growth factor-α breast cancer mouse model

The role of adiponectin and leptin signalling pathways has been suggested to play important roles in the protective effects of energy restriction (ER) on mammary tumour (MT) development. To study the effects of ER on the methylation levels in adiponectin receptor 1 (AdipoR1) and leptin receptor overlapping transcript (Leprot) genes using the pyrosequencing method in mammary fat pad tissue, mouse mammary tumour virus-transforming growth factor-α (MMTV-TGF-α) female mice were randomly assigned to ad libitum (AL), chronic ER (CER, 15 % ER) or intermittent ER (3 weeks AL and 1 week 60 % ER in cyclic periods) groups at 10 weeks of age until 82 weeks of age. The methylation levels of AdipoR1 in the CER group were higher than those in the AL group at week 49/50 (P < 0·05), while the levels of methylation for AdipoR1 and Leprot genes were similar among the other groups. Also, the methylation levels at CpG2 and CpG3 regions of the promoter region of the AdipoR1 gene in the CER group were three times higher (P < 0·05), while CpG1 island of Leprot methylation was significantly lower compared with the other groups (P < 0·05). Adiponectin and leptin gene expression levels were consistent with the methylation levels. We also observed a change with ageing in methylation levels of these genes. These results indicate that different types of ER modify methylation levels of AdipoR1 and Leprot in different ways and CER had a more significant effect on methylation levels of both genes. Epigenetic regulation of these genes may play important roles in the preventive effects of ER against MT development and ageing processes.

Expression of adiponectin receptors 1 and 2 and the leptin receptor in human adrenal tumors

INTRODUCTION

The role of adipokines in neoplasms not related to obesity is unclear. The presence of adiponectin receptors 1 and 2 (AdipoR1 and AdipoR2) as well as the leptin receptor (Ob-R) has been recognized in human adrenal tumors. The authors of the present study were the first to compare the expression of these receptors in histopathologically distinct adrenal tumors.

MATERIAL AND METHODS

The study encompassed tissue specimens of 128 patients with adrenal tumors (28 adrenal cortical adenomas (CA), 35 cortical nodular hyperplasia tumors (CNH), 20 cortical carcinomas (CC), 40 pheochromocytomas (PHEO), 5 malignant pheochromocytomas (PHEOM)) operated on at a single clinical center. The expression of the adiponectin receptors AdipoR1 and AdipoR2 as well as the leptin receptor Ob-R was assessed by immunohistochemistry. The results were correlated with body mass index (BMI) and gender of the patients.

RESULTS

AdipoR1 expression was significantly higher in cortical cancers (p < 0.001) and pheochromocytomas (p < 0.001) as compared to benign cortical tumors. AdipoR2 expression was significantly higher in cortical carcinomas as compared to cortical adenomas and hyperplasia tumors (p = 0.01), and also significantly higher in pheochromocytomas in comparison to adrenocortical cancers (p = 0.004). Leptin receptor expression was absent or minimal in half of nodular hyperplasia tumors and adrenal cortex adenomas. This receptor's expression was significantly higher in adrenocortical cancers (p = 0.038). In pheochromocytomas this receptor was expressed more abundantly than in adrenocortical cancers (p = 0.004).

CONCLUSIONS

These novel findings suggest that adiponectin and leptin receptors could play a regulatory role in human adrenal neoplasms.

Adipose Tissue, Obesity and Adiponectin: Role in Endocrine Cancer Risk

Adipose tissue has been recognized as a complex organ with endocrine and metabolic roles. The excess of fat mass, as occurs during overweight and obesity states, alters the regulation of adipose tissue, contributing to the development of obesity-related disorders. In this regard, many epidemiological studies shown an association between obesity and numerous types of malignancies, comprising those linked to the endocrine system (e.g., breast, endometrial, ovarian, thyroid and prostate cancers). Multiple factors may contribute to this phenomenon, such as hyperinsulinemia, dyslipidemia, oxidative stress, inflammation, abnormal adipokines secretion and metabolism. Among adipokines, growing interest has been placed in recent years on adiponectin (APN) and on its role in carcinogenesis. APN is secreted by adipose tissue and exerts both anti-inflammatory and anti-proliferative actions. It has been demonstrated that APN is drastically decreased in obese individuals and that it can play a crucial role in tumor growth. Although literature data on the impact of APN on carcinogenesis are sometimes conflicting, the most accredited hypothesis is that it has a protective action, preventing cancer development and progression. The aim of the present review is to summarize the currently available evidence on the involvement of APN and its signaling in the etiology of cancer, focusing on endocrine malignancies.

The Emerging Role of Adiponectin in Female Malignancies

Obesity, characterized by excess body weight, is now accepted as a hazardous health condition and an oncogenic factor. In different epidemiological studies obesity has been described as a risk factor in several malignancies. Some biological mechanisms that orchestrate obesity-cancer interaction have been discovered, although others are still not completely understood. The unbalanced secretion of biomolecules, called "adipokines", released by adipocytes strongly influences obesity-related cancer development. Among these adipokines, adiponectin exerts a critical role. Physiologically adiponectin governs glucose levels and lipid metabolism and is fundamental in the reproductive system. Low adiponectin circulating levels have been found in obese patients, in which its protective effects were lost. In this review, we summarize the epidemiological, in vivo and in vitro data in order to highlight how adiponectin may affect obesity-associated female cancers.

Obesity, Leptin and Breast Cancer: Epidemiological Evidence and Proposed Mechanisms

The prevalence of obesity has been steadily increasing over the past few decades in several developed and developing countries, with resultant hazardous health implications. Substantial epidemiological evidence has shown that excessive adiposity strongly influences risk, prognosis, and progression of various malignancies, including breast cancer. Indeed, it is now well recognized that obesity is a complex physiologic state associated with multiple molecular changes capable of modulating the behavior of breast tumor cells as well of the surrounding microenvironment. Particularly, insulin resistance, hyperactivation of insulin-like growth factor pathways, and increased levels of estrogen due to aromatization by the adipose tissue, inflammatory cytokines, and adipokines contribute to breast cancerogenesis. Among adipokines, leptin, whose circulating levels increase proportionally to total adipose tissue mass, has been identified as a key member of the molecular network in obesity. This review summarizes the current knowledge on the epidemiological link existing between obesity and breast cancer and outlines the molecular mechanisms underlying this connection. The multifaceted role of the obesity adipokine leptin in this respect is also discussed.

Adipokines as therapeutic targets in breast cancer treatment

INTRODUCTION

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

Obesity and Cancer: Existing and New Hypotheses for a Causal Connection

Existing explanations of obesity-associated cancer emphasise direct mutagenic effects of dietary components or hormonal imbalance. Some of these hypotheses are reviewed briefly, but recent evidence suggests a major role for chronic inflammation in cancer risk, possibly involving dietary content. These ideas include the inflammation-induced activation of the kynurenine pathway and its role in feeding and metabolism by activation of the aryl hydrocarbon receptor (AHR) and by modulating synaptic transmission in the brain. Evidence for a role of the kynurenine pathway in carcinogenesis then provides a potentially major link between obesity and cancer. A second new hypothesis is based on evidence that serine proteases can deplete cells of the tumour suppressors Deleted in Colorectal Cancer (DCC) and neogenin. These enzymes include mammalian chymotryptic proteases released by pro-inflammatory neutrophils and macrophages. Blood levels of chymotrypsin itself increase in parallel with food intake. The mechanistically similar bacterial enzyme subtilisin is widespread in the environment, animal probiotics, meat processing and cleaning products. Simple public health schemes in these areas, with selective serine protease inhibitors and AHR antagonists and could prevent a range of intestinal and other cancers.

Adiponectin Reverses the Proliferative Effects of Estradiol and IGF-1 in Human Epithelial Ovarian Cancer Cells by Downregulating the Expression of Their Receptors

The expression of adiponectin receptors AdipoR1 and AdipoR2 has been reported in the human ovary and ovarian cancer tissues. Moreover, adiponectin has been reported to act as an anti-tumor factor by inhibiting cancer cell proliferation. Thus, we investigate whether adiponectin and its receptors influence ovarian cancer development. In the present study, we found that adiponectin was not expressed in the granulosa cell line (COV434), and epithelial ovarian cancer cell lines (OVCAR-3, SKOV-3, and Caov-3). Additionally, we found that AdipoR1 and AdipoR2 expression is lower in epithelial ovarian cancer cells than in granulosa tumor cells. Endogenous 17β-estradiol as well as exogenous estrogens, such as bisphenol A and its chlorinated and brominated analogs do not affect adiponectin receptor expression. We found that adiponectin inhibited the growth of OVCAR-3 and SKOV-3 cells, and that this effect was independent of apoptosis. Moreover, adiponectin reverses the stimulatory effects of 17β-estradiol and insulin-like growth factor 1 on cell proliferation by downregulating the expression of their receptors, whereas progesterone increased the sensitivity of cancer cells to adiponectin by upregulating AdipoR1 and AdipoR2 expression. These results suggest interactions between adiponectin and various ovarian steroid hormone and growth factor pathways in ovarian cancer cells.

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

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

Voluntary physical activity counteracts the proliferative tumor growth microenvironment created by adipose tissue via high-fat diet feeding in female rats

The adipokine secretion profile created from adipose tissue may represent the molecular mechanism behind the obesity‐breast cancer association. Two adipokines, adiponectin (ADIPO), and leptin (LEP), are altered with obesity and exert antagonistic effects on breast cancer proliferation. We set out to determine whether the adipose‐dependent tumor promoting growth environment created by a high‐fat diet (HFD) in female Sprague‐Dawley rats is altered compared to established responses in male rats and whether voluntary physical activity (PA) ameliorates any HFD‐dependent effects. We found that conditioned media (CM) created from the adipose tissue of female HFD‐fed rats increased the proliferation of MCF7 cells compared to those cells grown in CM prepared from lean adipose tissue. HFD‐CM inhibited AMPK and activated Akt signaling, decreased p27 phosphorylation at T198, reduced total p27 and AdiporR1 protein levels and promoted cell‐cycle entry. PA reversed the proliferative effects of HFD‐CM on MCF7 cells by preventing the effects of HFD on AMPK, Akt, p27 and AdipoR1, ultimately resulting in cell‐cycle withdrawal. Overexpressing AdipoR1 abolished the proliferative effects of the HFD‐CM on MCF7 cells and enhanced the anti‐proliferative effects PA on the HFD‐CM. Thus, PA represents a means to prevent deleterious obesity‐related alterations in tumor growth environment which are brought about by changes in adipokine secretion profile from adipose tissue in the presence of estrogen. Furthermore, although adipose produces hundreds of adipokines, the ADIPO:LEP ratio may serve to indicate the contribution of adipose in creating a tumor growth microenvironment.

Obesity-associated Breast Cancer: Analysis of risk factors

Several studies show that a significantly stronger association is obvious between increased body mass index (BMI) and higher breast cancer incidence. Furthermore, obese women are at higher risk of all-cause and breast cancer specific mortality when compared to non-obese women with breast cancer. In this context, increased levels of estrogens due to excessive aromatization activity of the adipose tissue, overexpression of pro-inflammatory cytokines, insulin resistance, hyperactivation of insulin-like growth factors (IGFs) pathways, adipocyte-derived adipokines, hypercholesterolemia and excessive oxidative stress contribute to the development of breast cancer in obese women. While higher breast cancer risk with hormone replacement therapy is particularly evident among lean women, in postmenopausal women who are not taking exogenous hormones, general obesity is a significant predictor for breast cancer. Moreover, increased plasma cholesterol leads to accelerated tumor formation and exacerbates their aggressiveness. In contrast to postmenopausal women, premenopausal women with high BMI are inversely associated with breast cancer risk. Nevertheless, life-style of women for breast cancer risk is regulated by avoiding the overweight and a high-fat diet. Estrogen-plus-progestin hormone therapy users for more than 5 years have elevated risks of both invasive ductal and lobular breast cancer. Additionally, these cases are more commonly node-positive and have a higher cancer-related mortality. Collectively, in this chapter, the impacts of obesity-related estrogen, cholesterol, saturated fatty acid, leptin and adiponectin concentrations, aromatase activity, leptin and insulin resistance on breast cancer patients are evaluated. Obesity-related prognostic factors of breast cancer also are discussed at molecular basis.

Obesity and cancer: the role of adipose tissue and adipo-cytokines-induced chronic inflammation

Adipose tissue in addition to its ability to keep lipids is now recognized as a real organ with both metabolic and endocrine functions. Recent studies demonstrated that in obese animals is established a status of adipocyte hypoxia and in this hypoxic state interaction between adipocytes and stromal vascular cells contribute to tumor development and progression. In several tumors such as breast, colon, liver and prostate, obesity represents a poor predictor of clinical outcomes. Dysfunctional adipose tissue in obesity releases a disturbed profile of adipokines with elevated levels of pro-inflammatory factors and a consequent alteration of key signaling mediators which may be an active local player in establishing the peritumoral environment promoting tumor growth and progression. Therefore, adipose tissue hypoxia might contribute to cancer risk in the obese population. To date the precise mechanisms behind this obesity-cancer link is not yet fully understood. In the light of information provided in this review that aims to identify the key mechanisms underlying the link between obesity and cancer we support that inflammatory state specific of obesity may be important in obesity-cancer link.

Systemic Correlates of White Adipose Tissue Inflammation in Early-Stage Breast Cancer

PURPOSE

Obesity, insulin resistance, and elevated levels of circulating proinflammatory mediators are associated with poorer prognosis in early-stage breast cancer. To investigate whether white adipose tissue (WAT) inflammation represents a potential unifying mechanism, we examined the relationship between breast WAT inflammation and the metabolic syndrome and its prognostic importance.

EXPERIMENTAL DESIGN

WAT inflammation was defined by the presence of dead/dying adipocytes surrounded by macrophages forming crown-like structures (CLS) of the breast. Two independent groups were examined in cross-sectional (cohort 1) and retrospective (cohort 2) studies. Cohort 1 included 100 women undergoing mastectomy for breast cancer risk reduction (n = 10) or treatment (n = 90). Metabolic syndrome-associated circulating factors were compared by CLS-B status. The association between CLS of the breast and the metabolic syndrome was validated in cohort 2, which included 127 women who developed metastatic breast cancer. Distant recurrence-free survival (dRFS) was compared by CLS-B status.

RESULTS

In cohorts 1 and 2, breast WAT inflammation was detected in 52 of 100 (52%) and 52 of 127 (41%) patients, respectively. Patients with breast WAT inflammation had elevated insulin, glucose, leptin, triglycerides, C-reactive protein, and IL6 and lower high-density lipoprotein cholesterol and adiponectin (P < 0.05) in cohort 1. In cohort 2, breast WAT inflammation was associated with hyperlipidemia, hypertension, and diabetes (P < 0.05). Compared with patients without breast WAT inflammation, the adjusted HR for dRFS was 1.83 (95% CI, 1.07-3.13) for patients with inflammation.

CONCLUSIONS

WAT inflammation, a clinically occult process, helps to explain the relationship between metabolic syndrome and worse breast cancer prognosis. Clin Cancer Res; 22(9); 2283-9. ©2015 AACR.

The role of adiponectin in obesity-associated female-specific carcinogenesis

Adipose tissue is a highly vascularized endocrine organ, and its secretion profiles may vary with obesity. Adiponectin is secreted by adipocytes that make up adipose tissue. Worldwide, obesity has been designated a serious health problem among women and is associated with a variety of metabolic disorders and an increased risk of developing cancer of the cervix, ovaries, uterus (uterine/endometrial), and breast. In this review, the potential link between obesity and female-specific malignancies is comprehensively presented by discussing significant features of the intriguing and complex molecule, adiponectin, with a focus on recent findings highlighting its molecular mechanism of action in female-specific carcinogenesis.

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.

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.

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.

Cholesterol-induced mammary tumorigenesis is enhanced by adiponectin deficiency: role of LDL receptor upregulation

Adiponectin is an adipokine that can suppress the proliferation of various human carcinoma cells. Although its anti-tumor activities have been suggested by many clinical investigations and animal studies, the underlying mechanisms are not fully characterized. In MMTV-polyomavirus middle T antigen (MMTV-PyVT) transgenic mice models, reduced- or complete loss-of-adiponectin expression promotes mammary tumor development. The present study demonstrated that while tumor development in control MMTV-PyVT mice is associated with a progressively decreased circulating cholesterol concentration, adiponectin deficient MMTV-PyVT mice showed significantly elevated total- and low density lipoprotein (LDL)-cholesterol levels. Cholesterol contents in tumors derived from adiponectin deficient mice were dramatically augmented. High fat high cholesterol diet further accelerated the tumor development in adiponectin deficient PyVT mice. The protein levels of LDL receptor (LDLR) were found to be upregulated in adiponectin-deficient tumor cells. In human breast carcinoma cells, treatment with LDL-cholesterol or overexpressing LDLR elevates nuclear beta-catenin activity and facilitates tumor cell proliferation. On the other hand, adiponectin decreased LDLR protein expression in breast cancer cells and inhibited LDL-cholesterol-induced tumor cell proliferation. Both in vivo and in vitro evidence demonstrated a stimulatory effect of adiponectin on autophagy process, which mediated the down-regulation of LDLR. Adiponectin-induced reduction of LDLR was blocked by treatment with a specific inhibitor of autophagy, 3-methyladenine. In conclusion, the study demonstrates that adiponectin elicits tumor suppressive effects by modulating cholesterol homeostasis and LDLR expression in breast cancer cells, which is at least in part attributed to its role in promoting autophagic flux.

New insight into adiponectin role in obesity and obesity-related diseases

Obesity is a major health problem strongly increasing the risk for various severe related complications such as metabolic syndrome, cardiovascular diseases, respiratory disorders, diabetic retinopathy, and cancer. Adipose tissue is an endocrine organ that produces biologically active molecules defined “adipocytokines,” protein hormones with pleiotropic functions involved in the regulation of energy metabolism as well as in appetite, insulin sensitivity, inflammation, atherosclerosis, cell proliferation, and so forth. In obesity, fat accumulation causes dysregulation of adipokine production that strongly contributes to the onset of obesity-related diseases. Several advances have been made in the treatment and prevention of obesity but current medical therapies are often unsuccessful even in compliant patients. Among the adipokines, adiponectin shows protective activity in various processes such as energy metabolism, inflammation, and cell proliferation. In this review, we will focus on the current knowledge regarding the protective properties of adiponectin and its receptors, AdipoRs (“adiponectin system”), on metabolic complications in obesity and obesity-related diseases. Adiponectin, exhibiting antihyperglycemic, antiatherogenic, and anti-inflammatory properties, could have important clinical benefits in terms of development of therapies for the prevention and/or for the treatment of obesity and obesity-related diseases.

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.

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.

[Autologous fat transplantation in the modern reconstructive surgery of breast cancer]

Autologous fat transplantation is often used in aesthetic plastic surgery, and is recently becoming increasingly popular in the reconstruction of soft tissue defects following oncological surgery. A still not standardized technique of fat transplantation for breast cancer reconstruction is rapidly getting popular. The procedure is not a passive volume replacement, but transplantation of biologically active tissue bearing endocrine, paracrine, exocrine functions and containing fat-derived stem cells, which in the tumorous environment raises many questions in relation to the oncological safety and diagnostic follow-up. Although long-term results based on prospective, randomized studies are not yet available, published clinical experience is promising and reveals an effective and surgically safe procedure if used with appropriate indications and techniques. The authors conducted a broad review of the literature, presenting indications, technique, molecular interactions, and potential risks of the clinical results of autologous fat transplantation in the breast cancer reconstructive surgery. The authors initiated that breast and plastic surgeons should promote adequate long term follow-up of breast cancer patients who underwent breast reconstruction with autologous fat transplantation by the establishment of national registries.

Obesity, energy balance, and cancer: new opportunities for prevention

Obesity is associated with increased risk and poor prognosis for many types of cancer. The mechanisms underlying the obesity-cancer link are becoming increasingly clear and provide multiple opportunities for primary to tertiary prevention. Several obesity-related host factors can influence tumor initiation, progression and/or response to therapy, and these have been implicated as key contributors to the complex effects of obesity on cancer incidence and outcomes. These host factors include insulin, insulin-like growth factor-I, leptin, adiponectin, steroid hormones, cytokines, and inflammation-related molecules. Each of these host factors is considered in the context of energy balance and as potential targets for cancer prevention. The possibility of prevention at the systems level, including energy restriction, dietary composition, and exercise is considered as is the importance of the newly emerging field of stem cell research as a model for studying energy balance and cancer prevention.

Inhibition of smooth muscle cell proliferation by adiponectin requires proteolytic conversion to its globular form

Accelerated atherosclerosis is the primary cardiovascular manifestation of diabetes and correlates inversely with levels of circulating adiponectin, an anti-atherosclerotic adipokine that declines in diabetes. We therefore initiated a study to examine the mechanisms by which adiponectin, a hormone released from adipose tissue, influences the proliferation of vascular smooth muscle cells (SMCs). Addition of adiponectin to quiescent porcine coronary artery SMCs increased both protein and DNA synthesis and concurrently activated ERK1/2 and Akt. By contrast, globular adiponectin, a truncated form of this protein, exhibited anti-mitogenic properties as indicated by the inhibition of protein and DNA synthesis in SMCs stimulated with platelet-derived growth factor (PDGF). Whereas globular adiponectin did not stimulate growth-related signal transduction pathways, it was able to block the PDGF-dependent phosphorylation of eukaryotic elongation factor 2 kinase, a regulator of protein synthesis. Proteolysis of adiponectin with trypsin, which produces globular adiponectin, reversed the growth-stimulating actions of the undigested protein. As the existence of globular adiponectin remains controversial, western blotting was used to establish its presence in rat serum. We found that globular adiponectin was detectable in rat serum, but this result was not obtained with all antibodies. The contrasting properties of adiponectin and its globular form with respect to SMC proliferation suggest that protection against atherosclerosis may therefore be mediated, in part, by the level of globular adiponectin.

Obesity, but not high-fat diet, promotes murine pancreatic cancer growth

BACKGROUND

Obesity accelerates pancreatic cancer growth; the mechanisms underlying this association are poorly understood. This study evaluated the hypothesis that obesity, rather than high-fat diet, is responsible for accelerated pancreatic cancer growth.

METHODS

Male C57BL/6J mice were studied after 19 weeks of high-fat (60 % fat; n = 20) or low-fat (10 % fat; n = 10) diet and 5 weeks of Pan02 murine pancreatic cancer growth (flank).

RESULTS

By two-way ANOVA, diet did not (p = 0.58), but body weight, significantly influenced tumor weight (p = 0.01). Tumor weight correlated positively with body weight (R (2) = 0.562; p < 0.001). Tumors in overweight mice were twice as large as those growing in lean mice (1.2 ± 0.2 g vs. 0.6 ± .01 g, p < 0.01), had significantly fewer apoptotic cells than those in lean mice (0.8 ± 0.4 vs 2.4 ± 0.5; p < 0.05), and greater adipocyte volume (3.7 vs. 2.2 %, p < 0.05). Apoptosis (R (2) = 0.472; p = 0.008) and serum adiponectin correlated negatively with tumor weight (R = 0.45; p < 0.05).

CONCLUSIONS

These data suggest that body weight, and not high-fat diet, is responsible for accelerated murine pancreatic cancer growth observed in this model of diet-induced obesity. Decreased tumor apoptosis appears to play an important mechanistic role in this process. The concept that decreased apoptosis is potentiated by hypoadiponectinemia (seen in obesity) deserves further investigation.

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.

Inhibitory role of adiponectin peptide I on rat choroidal neovascularization

Age-related macular degeneration (AMD) is a leading cause of central blindness in the elderly population. The wet type of AMD is characterized by extensive growth of new vessels. One of the effective strategies to treat wet AMD is to limit the choroidal neovascularization (CNV). We studied the effects of adiponectin peptide I (APNpI) on new vessel growth in laser-induced rat model of wet AMD and on rat choroidal endothelial cell (CEC) culture. CNV size and vessel density were investigated by microscopy. Immunohistochemical staining (IHC) for von Willebrand Factor (vWF), APN, APN receptors 1 (AdipoR1), 2 (AdipoR2), VEGF, VEGF receptor 2 (VEGF-R2), proliferating cell nuclear antigen (PCNA) was performed in CNV area. The mRNA expression of VEGF and VEGF-R2 in RPE-choroid was investigated by RT-PCR and real-time PCR. APNpI inhibited area of CNV by 4 fold, number of vWF positive vessels by 99% and area of subretinal tissue by 40%. The expression of VEGF and VEGF-R2 at mRNA and protein levels decreased after APNpI treatment in vivo. Proliferative index (PCNA) was 5 folds less in laser spots of APNpI treated rats compared to controls. In conclusion, APNpI inhibited formation of new vessels in rat model of CNV by decreasing VEGF, VEGF-R2 expression and cell proliferation. Thus, APNpI may have potential therapeutic use for AMD treatment since it significantly inhibited CNV.