Common genetic variations in the LEP and LEPR genes, obesity and breast cancer incidence and survival

Urine exosome biomarkers of obesity after Lekhana Basti treatment - Report of a pilot study

BACKGROUND

Obesity is a rising risk factor for various diseases including cardiovascular diseases and Cancer. The limitations of targeted obesity-treatment approaches employed in the clinic presently underscore the importance of developing integrative management strategies for identification of specific biomarkers of obesity.

OBJECTIVES

Given the specificity of exosome/extracellular vesicle (EV) biomarkers, we aimed here to identify the EV biomarkers of Ayurveda treatment - Lekhana Basti - for Obesity.

METHODOLOGY

A total of eighteen 24-h urine samples from 6 participants with BMI>30 kg/m2 were used in this study, collected over 3 time-points during the Lekhana basti (medicated enema for obesity) treatment. Urine EV were isolated using Polyethylene Glycol (PEG). The proteins were resolved by 1-d gel electrophoresis and identified using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and quantified by label-free methods. Significant Protein-Protein Interactions, KEGG pathway analysis and enrichment, functional gene ontology (GO) annotation were identified and shortlisted in comparison to Obesity reference genes from DisGeNET.

RESULTS

With UniProt as a reference subsequent to LC-MS/MS-identification, a total of 210 exosome proteins were identified. Seventy-three proteins were overexpressed in pathway enrichment analysis. Further, GO functional annotation identified 15 common proteins involved. Finally, the 8 hub proteins associated with obesity were identified and their differential expression profile compared between three different time-points during Lekhana Basti treatment. Six protein markers overexpressed during obesity were downregulated post Lekhana Basti treatment, while 2 markers increased in abundance post-treatment.

CONCLUSION

To our knowledge, this is the first study to isolate and identify urine EV protein abundance profiles from obese female participants of India. The study results indicate significant changes in the differential expression profile of 8 hub proteins involved in obesity, after Lekhana Basti treatment. The biomarker signature of the pilot study indicates the role of Ayurveda treatment and the possible pathways involved in the treatment of Obesity. Further, this study underlines the specificity of urine exosomes/EV as diagnostic markers as well as the potential of Ayurveda treatment in effective management of obesity.

Leptin Receptor Gln223Arg Polymorphism of Human Spermatozoa Associated with Male Infertility in a Chinese Population

Background

Leptin (LEP) is believed to play a crucial role in male reproduction, while the molecular mechanisms through which LEP affects the male reproductive system are unclear. LEP acts by binding to a leptin receptor (LEPR) which mediates its physiological action, but there are only limited studies on the function of LEPR in human sperm.

Purpose

This study aimed to determine the Gln223Arg polymorphisms of the LEPR gene in human spermatozoa and evaluate their possible relationship with semen variables.

Methods

The study was performed on Chinese men: 115 healthy subjects and 108 patients with primary and 98 with secondary infertility. Semen samples were obtained from all patients, and semen variables were analyzed. The genotypic and allelic frequencies of Gln223Arg polymorphism in spermatozoa were determined by PCR and restriction fragment length polymorphism (RFLP) analyses. Statistical analyses were performed using the chi-square test, the Kruskal-Wallis test, and the Mann-Whitney test.

Results

There were no significant differences in genotypic or allelic frequency distributions of Gln223Arg polymorphism among men with primary infertility, secondary infertility, and controls. Similarly, semen volume and sperm concentration did not differ with the different genotypes in all groups of men. The percentages of motile sperm for AA + AG genotypes in men with primary infertility (31.98%) were significantly lower than those in secondary infertility, and control men with GG genotypes were 34.41% and 59.36%, respectively. At the same time, the percentages of normal morphology sperm for AA + AG genotypes in men with primary infertility (2.93%) were significantly lower than those in secondary infertility and control men with GG genotypes 3.71% and 6.54%, respectively.

Conclusion

This study reveals a possible association between the Gln223Arg polymorphism of the LEPR gene in spermatozoa affecting spermatozoal membrane integrity and having a direct role in sperm motility.

Genetic alterations in LEP and ADIPOQ genes and risk for breast cancer: a meta-analysis

Introduction

Breast cancer has a strong genetic predisposition, and its genetic architecture is not fully understood thus far. In this study, we aimed to perform a meta-analysis to evaluate the association of genetic alterations in LEP and ADIPOQ genes, as well as their receptor-encoded genes with risk for breast cancer.

Methods

Only published studies conducted in humans and written in English were identified by searching PubMed, SCOPUS, CINAHIL and Embase from their inception to October 2022. Eligibility assessment and data collection were completed independently by two researchers. Statistical analyses were done using the STATA software.

Results

After literature search, 33 publications were eligible for inclusion. Overall, LEP gene rs7799039-G allele (odds ratio [OR]: 0.78, 95% confidence interval [CI]: 0.62 to 0.98) and ADIPOQ gene rs1501299-T allele (OR: 1.41, 95% CI: 1.06 to 1.88) were associated with the significant risk of breast cancer. In subgroup analyses, differences in menopausal status, obesity, race, study design, diagnosis of breast cancer, genotyping method and sample size might account for the divergent observations of individual studies. Circulating leptin levels were comparable across genotypes of LEP gene rs7799039, as well as that of LEPR gene rs1137101 (P>0.05). Begg's funnel plots seemed symmetrical, with the exception of LEPR gene rs1137100 and ADIPOQ gene rs1501299.

Discussion

Taken together, we found, in this meta-analysis, that LEP gene rs7799039 and ADIPOQ gene rs1501299 were two promising candidate loci in predisposition to breast cancer risk.

Leptin and leptin receptor expression as biomarkers for breast cancer: a retrospective study

BACKGROUND

Effective screening and treatment have reduced the number of women dying from breast cancer (BC). However, the long-term sequelae of BC treatment and psychosocial factors seriously affect the life quality of BC patients and survivors. Therefore, the discovery and application of targeted biomarkers to improve the functional outcome and life quality of BC patients is necessary.

AIMS

To explore the impact of leptin (LEP)/ leptin receptor (LEPR) expression on occurrence and survival of BC.

METHODS

Totally 132 primary BC and 66 non-BC patients who underwent surgery in department of breast surgery in Shanxi Cancer Hospital from January to October in 2009 were enrolled in this retrospective study. LEP and LEPR were examined in BC tissues, benign breast tissues, para-carcinoma tissues using immunohistochemical staining. Kaplan-Meier curve was generated to test survival time.

RESULTS

The high level expression of LEP and LEPR in BC tissues were significantly higher than that in benign breast tissues and in para-carcinoma tissues (all P < 0.05). The LEP expression in patients with lymph node metastases was significantly higher than that in patients without lymph nodes metastases (P = 0.002). LEPR expression was correlated with higher Ki-67 rate (P = 0.002). LEP and LEPR both had no impact on survival (all P > 0.05).

CONCLUSIONS

High LEP/LEPR expression were risk factors for occurrence of BC, but without impact on survival.

The Effects of BMI and Genetic Variation of Adipokines on Serum Concentrations of Hormones in Untreated Individuals with Breast Cancer; a Pilot Study

Background: Numerous studies have shown an association between hormones secreted by adipose tissues and cancer development. Objectives: This study aimed at investigating the effect of body mass index (BMI) and genetic variation of leptin and adiponectin on serum concentrations of leptin, adiponectin, and estradiol among untreated breast cancer. Methods: This case-control study was performed on 350 women (175 women with breast cancer and 175 healthy controls), who had not taken any medications. Serum levels of estradiol (17-beta estradiol), leptin, and adiponectin were measured, using the ELISA technique. Single-nucleotide polymorphisms of leptin gene (LepG2548A), leptin receptor (Q223, K109R, and K656N), and adiponectin gene (T45G, G276T, C11377G, and 11391A) in blood-isolated DNA were evaluated, using RFLP-PCR technique. Results: Body mass index can affect serum concentrations of hormones and is associated with breast cancer. Also, except for adiponectin C11377G polymorphism, other all genetic variations showed significant relationships with breast cancer. In both groups, BMI was significantly correlated with the mean serum concentrations of hormones, and the risk of breast cancer increased in G2548A, Q223R, K656N, and G276T polymorphisms. The effect of risk allele genotypes on serum concentration of hormones showed that changes in serum concentration of estrogen and leptin in all studied polymorphisms were associated with breast cancer in postmenopausal women. But adiponectin level was only affected by polymorphisms K109R, K656N, and G276 and G11391A. Conclusions: High BMI and genetic variation can affect cancer development by changing the serum concentrations of hormones in different genotypes. Studying various populations’ genetics and lifestyle can help definitive conclusions about genetics and obesity.

Targeting regulation of the tumour microenvironment induces apoptosis of breast cancer cells by an affinity hemoperfusion adsorbent

The cytokine network of tumour microenvironment (TME) plays an important role in cancer growth and progression. The current work aims to provide a new strategy for cancer therapy based on the targeted regulation of cytokines in the TME. Here, heparin-coupled polyvinyl alcohol (PVA-H) microspheres have been developed as an adsorbent for selectively remove tumour-induced immunosuppressive cytokines, such as vascular endothelial growth factor (VEGF) and transforming growth factor-beta (TGF-β), but not tumour necrosis factor-alpha (TNF-α) which has an immune-stimulating effect and can inhibit tumour growth. The proliferation and apoptosis of breast cancer cells after perfusion were tested by cell viability assays, flow cytometry analysis and mRNA microarray assays. Results showed that the PVA-H microspheres efficiently absorbed the majority of VEGF (74.39%) and TGF-β (86.39%), but much less TNF-α (4.16%). The regulation of the cytokines had remarkable anti-proliferative and pro-apoptotic effects on breast cancer cells, which was further confirmed from the change of mRNA expression levels. Thus, targeting regulatory pathways within the TME by an affinity adsorbent that selectively depletes immunosuppressive cytokines is potentially a new and promising strategy for cancer therapy.

Biochemical study on modifying role of variants of leptin gene and its receptor on serum leptin levels in breast cancer

The leptin is discharged from breast adipose tissue and is overexpressed in breast cancer (BC). Conflicting relation of leptin with BC was reported. We investigated this association and its impact on leptin level and disease characteristics. The study included 70 females (40 women with pathological proof of invasive BC patients and 30 controls). LEP and LEPR polymorphisms were evaluated by real-time PCR. Serum leptin was estimated by ELISA. Both LEPR and LEP disturbances increase the danger of BC where GG genotype and G allele frequencies of LEPR were higher in patients vs. control. GG genotype increases BC risk with OR (9.1) while G allele predisposes to disease with OR (3.8). Furthermore, LEP A allele was uniquely elevated in patients than healthy ones with OR (2.06). Precise relation of circulating leptin and its polymorphisms with predicting BC may authorize its utilization in early screening.

Investigation of leptin receptor rs1137101 G>A polymorphism with cancer risk: evidence from 35936 subjects

Leptin receptor (LEPR) signaling may be involved in promoting angiogenesis and proliferation, inhibiting apoptosis and playing a vital role in the progression of carcinogenesis. A number of studies have focused on the association of LEPR rs1137101 variants with susceptibility of cancer, however, the observed results were controversial. We searched literature on the relationship of LEPR rs1137101 G>A polymorphism with cancer risk by using PubMed and Embase databases, covering all publications up to 14 October 2018. In total, 44 case–control studies with 35,936 subjects were included. After combining all eligible studies, we identified null relationship between LEPR gene rs1137101 G>A polymorphism and overall cancer risk [A vs. G: odds ratio (OR ) =  0.97, 95% confidence interval (CI ) =  0.89–1.06, P = 0.547; AA vs. GG: OR  =  0.93, 95% CI  =  0.78–1.13, P = 0.476; AA/GA vs. GG: OR  =  0.99, 95% CI  =  0.91–1.09, P= 0.890 and AA vs. GA/GG: OR  = 0.92, 95% CI  =  0.82–1.04, P= 0.198]. However, in a subgroup analysis, there was an increased susceptibility of oral and oropharyngeal cancer in AA vs. GA/GG genetic model (OR, 1.83; 95% CI, 1.01–3.33; P=0.048). Considering the limited participants were included, the findings might be underpowered. Sensitivity analysis identified that any independent study omitted did not materially influence the pooled ORs and CIs. The results of publication bias detection showed that there was no evidence of bias. In summary, this analysis indicates that no significant association of cancer risk was identified to be correlated with rs1137101 G>A variants, even in stratified analyses.

Leptin rs7799039 (G2548A) polymorphism is associated with cancer risk: a meta-analysis involving 25,799 subjects

Background: Leptin (LEP) is a human analogous form of the mouse obese gene and plays a critical role in energy expenditure as well as the progression of carcinogenesis. Many studies exploring the relationship between the LEP rs7799039 (G2548A) polymorphism and cancer risk have observed controversial results. To extensively evaluate this potential association, we conducted this meta-analysis.

Methods: All eligible studies published up to August 2018 on the relationship between the LEP rs7799039 G>A polymorphism and cancer risk were obtained by searching PubMed, EMBASE, and the China Biology Medicine databases. The association of LEP rs7799039 G>A polymorphism with cancer risk was evaluated by crude ORs together with their 95% CI's.

Results: Thirty-one case–control studies involving 25,799 subjects were included for meta-analysis. We identify a significant correlation with an overall cancer risk when these eligible case–control studies were pooled for analysis: for AA vs GG: an OR = 1.22, 95% CI = 1.01–1.48, P = 0.042 and for AA/GA vs GG: an OR = 1.16, 95% CI = 1.02–1.33, P = 0.026. A significant association was also detected in Asians, prostate cancer, other cancers, and hematopoietic malignancy subgroups. Sensitivity analysis was conducted by deleting an individual study in turn and calculation of the pooled ORs and CIs of the remainders. The results of sensitivity analyses indicated that no eligible study influenced the pooled ORs and CIs materially. Begg’s and Egger’s tests revealed that there was no evidence of publication bias.

Conclusion: In conclusion, our study suggests that the LEP rs7799039 G>A polymorphism might contribute to the development of cancer. In order to further verify or refute our findings, large and well-designed epidemiological studies are needed.

Association between circulating leptin concentration and G-2548A gene polymorphism in patients with breast cancer: a meta-analysis

INTRODUCTION

The aim of this meta-analysis was to summarize the evidence on the serum/plasma leptin concentrations in breast cancer (BC) patients, as well as the associations between leptin G-2548A gene polymorphisms and susceptibility to BC.

MATERIAL AND METHODS

Potentially relevant studies about serum/plasma leptin levels and leptin G-2548A gene polymorphism were selected using the electronic databases PubMed, EMBASE and The Cochrane Library (from January 1 1995 to Jun 30 2017, no language restrictions). The potential sources of heterogeneity were assessed by the Q statistic and quantified using I² ; publication bias was qualitatively assessed by funnel plot and quantitatively assessed by Egger's linear regression test.

RESULTS

A total of 1141 articles were retrieved after database searches, and 27 studies with 9516 subjects (4542 BC patients/4974 controls) were finally included. The results indicated that BC patients had significantly higher leptin levels compared with healthy controls (SMD = 1.65, 95% CI: 1.21-2.09, p < 0.001), but there was no association between leptin G-2548A polymorphism and BC (OR = 1.05, 95% CI: 0.80-1.39, p = 0.722). Subgroup analyses demonstrated increased leptin levels in BC patients of different region, race, body mass index and waist circumference.

CONCLUSIONS

Our results revealed a significantly higher leptin level in BC patients than in healthy controls, but no association between leptin G-2548A polymorphism and BC susceptibility was found.

Interactions between RASA2, CADM1, HIF1AN gene polymorphisms and body fatness with breast cancer: a population-based case-control study in China

Genome-wide association studies (GWAS) have indicated that gene polymorphisms in alleles of RAS p21 protein activator 2 (RASA2), cell adhesion molecule 1 (CADM1) and hypoxia inducible factor 1 alpha subunit inhibitor (HIF1AN) are associated with the risk of obesity. In this study, we explored the interactions between candidate SNPs of RASA2 (rs16851483), CADM1 (rs12286929) and HIF1AN (rs17094222) and body fatness for breast cancer risk. Unconditional logistic regression models were applied to measure the associations of related factors with breast cancer by odds ratios (ORs) and 95% confidence intervals (CIs). It was observed that cases had a statistically higher body mass index (BMI ≥ 28 kg/m², OR = 1.77), waist circumference (WC ≥ 90cm, OR = 2.89) and waist-to-hip ratio (WHR ≥ 0.9, OR = 3.41) as compared to controls. Significant differences were also found in the genotype distributions of RASA2 rs16851483 T/T homozygote and CADM1 rs12286929 G/A heterozygote between cases and controls, with an OR of 1.68 (95% CI: 1.10-2.56) and 0.80 (95% CI: 0.64-0.99), respectively. Furthermore, significant interactions were observed between polymorphisms of three genes and body fatness for the risk of breast cancer based on both additive and multiplicative scales. These results of our study suggest that body fatness possibly plays an important role in the development of breast cancer and this risk might be modified by specific genotypes of some potential genes, especially for obese women in China.

Association of two obesity-related gene polymorphisms LEPG2548A rs7799039 and LEPRQ223R rs1137101 with the risk of breast cancer

Many studies have been performed to investigate the correlation of leptin (LEP) and leptin receptor (LEPR) polymorphisms with breast cancer (BC) risk, however the results are inconclusive. To obtain a more precise estimation, we conducted this meta-analysis. We searched PubMed, EMBASE, and Web of Science databases to identify qualified studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the association. Eight eligible studies (2,124 cases and 5,476 controls) for LEP G2548A (rs7799039) polymorphism, and thirteen studies (5,282 cases and 6,140 controls) for LEPR Q223R (rs1137101) polymorphism were included in our study. In general, no significant association between LEP G2548A polymorphism and BC susceptibility was found among five genetic models. In the stratified analysis by ethnicity and sources of controls, significant associations were still not detected in all genetic models. For LEPR Q223R polymorphism, we observed that the association was only statistically significant in Asians (G versus A: OR = 0.532, P = 0.009; GG versus AA: OR = 0.233, P = 0.002; GA versus AA: OR =0.294, P = 0.006; GG versus AA+AG: OR =0.635, P = 0; GA+GG versus AA: OR = 0.242, P = 0.003), but not in general populations and Caucasians. In conclusion, LEP G2548A polymorphism has no relationship with BC susceptibility, while LEPR Q223R polymorphism could decrease BC risk in Asians, but not in overall individuals and Caucasians. More multicenter studies with larger sample sizes are required for further investigation.

Circulating leptin, soluble leptin receptor, free leptin index, visfatin and selected leptin and leptin receptor gene polymorphisms in sporadic breast cancer

Leptin and visfatin are implicated in breast cancer risk but studies accounting for bioavailability of leptin are sparse. Reports on the association of leptin gene (LEP) and leptin receptor gene (LEPR) polymorphisms with breast cancer are also inconsistent. Only a very few studies have examined biochemical and genetic variables concomitantly in the same cohort. A matched pairs study was carried out to ascertain whether plasma leptin, soluble leptin receptor, free leptin index (leptin/soluble leptin receptor), serum visfatin and selected LEP and LEPR polymorphisms are risk factors for sporadic breast cancer. Newly diagnosed sporadic breast cancer patients (N=80) were matched for age, body mass index (BMI) and menopausal status with healthy controls. Plasma leptin, soluble leptin receptor and serum visfatin were measured by enzyme-immunoassay. LEP -2548 A/G and LEPR K109R, LEPR Q223R polymorphisms were determined by genotyping. Leptin (p=0.0234), leptin/BMI (p=0.0468), free leptin index (p<0.0001) and visfatin (p=0.0002) were significantly higher and soluble leptin receptor (p<0.0001) was significantly lower in patients. LEPR gene K109R A/G polymorphism increased breast cancer risk (odds ratio: 4.125). Multivariate analysis confirmed that leptin, soluble leptin receptor, free leptin index and G109 (R109) allele of the LEPR gene K109R polymorphism are risk factors for breast cancer. When stratified by menopausal status free leptin index and soluble leptin receptor remained as risk factors irrespective of menopausal status while LEPR gene K109R A/G polymorphism remained as a risk factor only in the postmenopausal group.

LEP rs7799039, LEPR rs1137101, and ADIPOQ rs2241766 and 1501299 Polymorphisms Are Associated With Obesity and Chemotherapy Response in Mexican Women With Breast Cancer

BACKGROUND

Obesity plays a major role in the pathogenesis of breast cancer. Leptin (LEP) and adiponectin (ADIPOQ) are important in the regulation of adipose tissue. The response to cancer treatment depends on the histological and molecular tumor type, clinical stage, and genetic variability that might promote carcinogenic development. The aim of this study was to investigate the association between overweight/obesity and polymorphisms in the LEP (rs7799039), LEP receptor (LEPR; rs1137101), and ADIPOQ genes (rs2241766, rs1501299) with the response to breast cancer treatment in Mexican women.

PATIENTS AND METHODS

A sample of 177 patients with primary breast cancer (stage I-III) and who received neoadjuvant therapy were included. Polymorphisms were genotyped and their serum LEP concentrations (n = 59) were quantified.

RESULTS

The patients' median age was 53.1 years, the frequency of overweight and obesity was 57 and 84 patients, respectively, 117 were postmenopausal, and 64 of the patients did not respond to chemotherapy. An association of the LEP rs7799039, LEPR rs1137101, and ADIPOQ rs1501299 polymorphisms with overweight/obesity was found. The patients who did not respond to treatment were more frequently obese, at clinical stage III, had metastases, and high levels of glucose. Moreover, in samples that were positive for estrogen receptor, higher levels of LEP were found, and in wild type genotypes for LEP rs7799039 and LEPR rs1137101.

CONCLUSION

There was a direct association between the polymorphisms in LEP rs7799039 and ADIPOQ rs1501299 with overweight/obesity, and these genotypes affected the response to chemotherapeutic treatment, suggesting that an obesogenic microenvironment is more favorable for tumoral progression.

Energy homeostasis genes and survival after breast cancer diagnosis: the Breast Cancer Health Disparities Study

PURPOSE

The leptin-signaling pathway and other genes involved in energy homeostasis (EH) have been examined in relation to breast cancer risk as well as to obesity. We test the hypothesis that genetic variation in EH genes influences survival after diagnosis with breast cancer and that body mass index (BMI) will modify that risk.

METHODS

We evaluated associations between 10 EH genes and survival among 1,186 non-Hispanic white and 1,155 Hispanic/Native American women diagnosed with breast cancer. Percent Native American (NA) ancestry was determined from 104 ancestry-informative markers. Adaptive rank truncation product (ARTP) was used to determine gene and pathway significance.

RESULTS

The overall EH pathway was marginally significant for all-cause mortality among women with low NA ancestry (P(ARTP) = 0.057). Within the pathway, ghrelin(GHRL) and leptin receptor (LEPR) were significantly associated with all-cause mortality (P(ARTP) = 0.035 and 0.007, respectively). The EH pathway was significantly associated with breast cancer-specific mortality among women with low NA ancestry (P(ARTP) = 0.038). Three genes cholecystokinin (CCK), GHRL, and LEPR were significantly associated with breast cancer-specific mortality among women with low NA ancestry (P(ARTP) = 0.046,0.015, and 0.046, respectively), while neuropeptide Y (NPY) was significantly associated with breast cancer-specific mortality among women with higher NA ancestry(P(ARTP) = 0.038). BMI did not modify these associations.

CONCLUSIONS

Our data support our hypothesis that certain EH genes influence survival after diagnosis with breast cancer; associations appear to be most important among women with low NA ancestry.

Analysis of the Relationship between Estradiol and Follicle-Stimulating Hormone Concentrations and Polymorphisms of Apolipoprotein E and LeptinGenes in Women Post-Menopause

Background: Menopause is the permanent cessation of menstruation due to loss of ovarian follicular activity. A review of the available literature indicates that correlations between the changes that take place in a woman’s body after menopause and different genetic variants are still being sought. Methods: The study was conducted in 252 women who had completed physiological menopause. The women were divided into groups according to the time elapsed since menopause. The total concentrations of estradiol and follicle-stimulating hormone were determined by means of electrochemiluminescence. The apolipoprotein E (APOE) and lepitn (LEP) genotypes were determined by real-time PCR and polymerase chain reaction–restriction fragment length polymorphism, respectively. Results: We observed that people with the APOE3/E3 genotype entered menopause insignificantly later compared to other genotypes. Additionally, in the group of patients with the APOE3/E3 genotypes, differences in the E2 concentration were significantly related to the time since their last menstruation. There is no association found in the literature between these polymorphisms of the LEP gene and hormones. Conclusions: To date, attempts to formulate a model describing the association between E2 and FSH concentration with the polymorphisms of various genes of menopause in women have not been successful. This relationship is difficult to study because of the number of nongenetic factors. Environmental factors can explain variation in postmenopausal changes in hormone levels.

Obesity and Breast Cancer: Molecular Interconnections and Potential Clinical Applications

Obesity is an important risk factor for breast cancer (BC) in postmenopausal women; interlinked molecular mechanisms might be involved in the pathogenesis. Increased levels of estrogens due to aromatization of the adipose tissue, inflammatory cytokines such as tumor necrosis factor-α, interleukin-6, and prostaglandin E2, insulin resistance and hyperactivation of insulin-like growth factors pathways, adipokines, and oxidative stress are all abnormally regulated in obese women and contribute to cancerogenesis. These molecular factors interfere with intracellular signaling in the mitogen-activated protein kinase and phosphatydilinositol-3-phosphate/mammalian target of rapamycin (mTOR) pathways, which regulate the progression of the cell cycle, apoptosis, and protein synthesis. In this context, structural defects of typical genes related to both BC and obesity, such as leptin, leptin receptor, serum paraoxonase/arylesterase 1, the fat mass and obesity-associated gene and melanocortin receptor 4, have been associated with a high or low risk of BC development. The early detection of these gene alterations might be useful as risk predictors in obese women, and targeting these pathways involved in the BC pathogenesis in obese women is a potential therapeutic tool. In particular, mTOR pathway deregulation concurs in both obesity and BC, and inhibition of this might disrupt the molecular interlinks in a similar manner to that of metformin, which exerts definite anticancer activity and is currently used as an antidiabetic drug with a weight-reducing property. The identification of both genetic and pharmacological implications on the prevention and management of BC is the ultimate aim of these studies.

IMPLICATIONS FOR PRACTICE

Obese women are at risk of breast cancer, but clinicians lack concrete tools for the prevention or early diagnosis of this risk. The present study, starting from the biology and the molecular defects characterizing both obesity and breast cancer, analyzed the potential molecules and genetic defects whose early identification could delineate a risk profile. Three steps are proposed that are potentially achievable in the clinical assessment of obese women, namely the evaluation of altered levels of serum molecules, the identification of genetic polymorphisms, and the study of the transcriptomic profile of premalignant lesions. Finally, the therapeutic implications of this molecular assessment were evaluated.

Association Between Leptin (-2548G/A) Genes Polymorphism and Breast Cancer Susceptibility: A Meta-Analysis

Leptin is a confirmed breast cancer susceptibility gene. However, published studies reported mixed results. This meta-analysis was conducted to systematically get a more accurate estimation of the association between the Leptin (-2548G/A) gene polymorphism and breast cancer risk. To assess the effect of Leptin (-2548G/A) gene polymorphism on breast cancer susceptibility, we searched PUBMED, ISI Web of Knowledge, EMBASE, Chinese National Knowledge Infrastructure (CNKI) databases until September 2015 to identify eligible studies, without restriction. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the susceptibility to breast cancer. Separate analyses were conducted on features of the population such as ethnicity, source of controls, and country. A total of 9 case-control studies on Leptin (-2548G/A) gene polymorphism and breast cancer risk, including 3725 cases and 3093 case-free controls were identified. The results revealed that compared with the G allele, the A allele was associated with modestly increased risk of overall breast cancer (A vs G: OR = 1.12, 95%CI = 1.04-1.20, P = 0.002, Phet P < 0.00001). Following further stratified analyses, in the subgroup analyses by ethnicity, a significantly increased risk was observed among Caucasian (A vs G: OR = 1.11, 95%CI = 1.03-1.20, P = 0.006, Phet = 0.00001). No publication bias was found in the present study. In conclusion, our meta-analysis suggests that the Leptin (-2548G/A) gene polymorphism plays an important role in breast cancer susceptibility, especially in Caucasian.

Energy homeostasis genes and breast cancer risk: The influence of ancestry, body size, and menopausal status, the breast cancer health disparities study

BACKGROUND

Obesity and breast cancer risk is multifaceted and genes associated with energy homeostasis may modify this relationship.

METHODS

We evaluated 10 genes that have been associated with obesity and energy homeostasis to determine their association with breast cancer risk in Hispanic/Native American (2111 cases, 2597 controls) and non-Hispanic white (1481 cases, 1585 controls) women.

RESULTS

Cholecystokinin (CCK) rs747455 and proopiomelanocortin (POMC) rs6713532 and rs7565877 (for low Indigenous American (IA) ancestry); CCK rs8192472 and neuropeptide Y (NYP) rs16141 and rs14129 (intermediate IA ancestry); and leptin receptor (LEPR) rs11585329 (high IA ancestry) were strongly associated with multiple indicators of body size. There were no significant associations with breast cancer risk between genes and SNPs overall. However, LEPR was significantly associated with breast cancer risk among women with low IA ancestry (PARTP=0.024); POMC was significantly associated with breast cancer risk among women with intermediate (PARTP=0.015) and high (PARTP=0.012) IA ancestry. The overall pathway was statistically significant for pre-menopausal women with low IA ancestry (PARTP=0.05), as was cocaine and amphetamine regulated transcript protein (CARTPT) (PARTP=0.014) and ghrelin (GHRL) (PARTP=0.007). POMC was significantly associated with breast cancer risk among post-menopausal women with higher IA ancestry (PARTP=0.005). Three SNPs in LEPR (rs6704167, rs17412175, and rs7626141), and adiponectin (ADIPOQ); rs822391) showed significant 4-way interactions (GxExMenopausexAncestry) for multiple indicators of body size among pre-menopausal women.

CONCLUSIONS

Energy homeostasis genes were associated with breast cancer risk; menopausal status, body size, and genetic ancestry influenced this relationship.

Genetic association between leptin-2548G/A polymorphism and risk of cancer: a meta analysis

OBJECTIVE

Abundance of evidence implicated that leptin may play a decisive role in cancer occurrence, but the reported results varied across the individually published studies. The objective of this study is to access to what extent the extensively studied -2548G/A polymorphism of LEP gene acts on the onset of multiple cancers.

METHODS

Eligible studies included in this meta-analysis were identified electronically in PubMed and Embase, and manually in relevant literature. Crude odds ratio (OR) with corresponding 95% confidence interval (CI) was calculated to estimate the risk of cancer associated with the -2548G/A polymorphism.

RESULTS

12 association studies with a total of 5,618 cancer cases and 6,509 healthy controls were pooled into this meta-analysis. The results revealed that compared with the G allele, the A allele was associated with modestly increased risk of overall cancer (OR, 1.21; 95% CI, 1.02-1.44). Following further stratified analyses, a borderline association was indicated in prostate cancer (OR, 1.18; 95% CI, 1.00-1.39), breast cancer (OR, 1.11; 95% CI, 1.00-1.22) and Caucasians (OR, 1.19; 95% CI, 1.00-1.41).

CONCLUSIONS

This meta-analysis reveals that the A allele of -2548G/A polymorphism may be a determinant of cancer development.

The Relationship between -2548 G/A Leptin Gene Polymorphism and Risk of Breast Cancer and Serum Leptin Levels in Ahvazian Women

BACKGROUND

Potential association of leptin (LEP) gene polymorphisms has been suggested in the processes leading to breast cancer initiation and progression. We investigated whether genetic variations in the LEP -2548G/A gene are associated with risk of breast cancer.

METHODS

This case-control study consisted of 100 breast cancer cases and 100 control subjects without breast cancer that matched for age and body mass index (BMI). Genotyping of LEP -2548G/A polymorphism was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Serum leptin level was determined by ELISA in all study subjects.

RESULTS

The genotype distributions (AA, AG, and GG) were 36, 55, and 9% in breast cancer cases and 52, 45, and 3% in control group, respectively. The frequency of LEP -2548 GG genotype was significantly elevated in breast cancer cases as compared to controls (χ2=6.90, p=0.032). Similar difference was also found in allele frequencies between two groups (χ2=5.65, p=0.017). A markedly increase risk of breast cancer was associated with the LEP -2548GG genotype when compared to the LEP -2548 AA genotype (OR=4.33, 95% CI=1.09-17.22). In addition, postmenopausal women who bear at least one LEP -2548 G allele were at a markedly increased risk of breast cancer after adjusting for age and BMI confounders (OR=12.24, 95% CI=1.13-131.73).

CONCLUSION

The LEP -2548 G/A polymorphism is associated with markedly increased risk of breast cancer especially in postmenopausal Ahvazian women and supported the hypothesis that leptin is involved in breast cancer.

The LEP G-2548A gene polymorphism is associated with age at menarche and breast cancer susceptibility

Leptin is an adipocytokine made by fat cells and plays a key role in proliferation, cell survival, migration and immune response. It has a powerful effect on the initiation of puberty and in determining age at menarche. The current study is the first investigation to examine the effect of G-2548A leptin gene polymorphism on the age at menarche and breast cancer susceptibility. This case-control study was performed on 203 patients with breast cancer and 171 healthy women. The leptin genotypes were determined using the PCR-RFLP method and age at menarche was obtained by questionnaires. There was a significant difference between the leptin G-2548A genotypes between case and control groups (P<0.05). AA genotype is significantly higher in patients compared to the controls. Furthermore, women carrying the AA genotype had a significantly younger age at menarche (12.47 years) than women with the AG (12.94 years) and GG (13.47 years) genotypes. Also, we found that the AA genotype frequency in women with age at menarche <13 years was higher than in women with age at menarche ≥13 years (OR: 3.4, 95% CI: 1.7-6.7, P: 0.001). In conclusion, the G-2548A leptin gene polymorphism has an important role in the onset of menarche and breast cancer susceptibility.

Effect of leptin receptor Q223R polymorphism on breast cancer risk

OBJECTIVES

Leptin receptor (LEPR) is a member of the class I cytokine receptor super-family that is known implicated in the initiation and progression of breast cancer. We have investigated the effect of Q223R polymorphism on the breast cancer susceptibly in a sample of Iranian subjects.

MATERIALS AND METHODS

We utilized a polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP) method to investigate the association of LEPR Q223R polymorphism with breast cancer risk in a case control study consisting of 100 breast cancer cases and 100 controls without breast cancer. Serum levels of leptin and soluble leptin receptor (sOB-R) were measured by ELISA method.

RESULTS

The genotype (QQ, QR, and RR) distributions were 25, 56, and 19 % in breast cancer cases and 54, 40, and 6% in controls, respectively. The frequency of 223 RR genotype was significantly elevated in breast cancer cases as compared to controls (χ(2)= 20.072, P<0.001). Similar significance differences were also found in allele frequencies for Q and R between two groups (χ(2)= 19.027, P< 0.001). Additionally, there were significant association between Q223R genotypes and breast cancer risk; homozygotes for RR genotype (OR= 6.840; 95% confidence interval [CI] = 2.434-19.218), heterozygotes for QR (OR=3.024; 95% CI = 1.620-5.644, P = 0.001), and QR+RR genotype (OR= 3.522; 95% CI = 1.934-6.414, P < 0.001), respectively.

CONCLUSION

Our results showed that the LEPR Q223R polymorphism is associated with increased breast cancer risk as well as tumor grade in a sample of Iranian subjects.

Kinetics of leptin binding to the Q223R leptin receptor

Studies in human populations and mouse models of disease have linked the common leptin receptor Q223R mutation to obesity, multiple forms of cancer, adverse drug reactions, and susceptibility to enteric and respiratory infections. Contradictory results cast doubt on the phenotypic consequences of this variant. We set out to determine whether the Q223R substitution affects leptin binding kinetics using surface plasmon resonance (SPR), a technique that allows sensitive real-time monitoring of protein-protein interactions. We measured the binding and dissociation rate constants for leptin to the extracellular domain of WT and Q223R murine leptin receptors expressed as Fc-fusion proteins and found that the mutant receptor does not significantly differ in kinetics of leptin binding from the WT leptin receptor. (WT: k_a 1.76×10⁶±0.193×10⁶ M⁻¹ s⁻¹, k_d 1.21×10⁻⁴±0.707×10⁻⁴ s⁻¹, K_D 6.47×10⁻¹¹±3.30×10⁻¹¹ M; Q223R: k_a 1.75×10⁶±0.0245×10⁶ M⁻¹ s⁻¹, k_d 1.47×10⁻⁴±0.0505×10⁻⁴ s⁻¹, K_D 8.43×10⁻¹¹±0.407×10⁻¹¹ M). Our results support earlier findings that differences in affinity and kinetics of leptin binding are unlikely to explain mechanistically the phenotypes that have been linked to this common genetic variant. Future studies will seek to elucidate the mechanism by which this mutation influences susceptibility to metabolic, infectious, and malignant pathologies.

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.

Association of LEP G2548A and LEPR Q223R polymorphisms with cancer susceptibility: evidence from a meta-analysis

BACKGROUND

Numerous epidemiological studies have examined associations of genetic variations in LEP (G2548A, -2548 nucleotide upstream of the ATG start site) and LEPR (Q223R, nonsynonymous SNP in exon 6) with cancer susceptibility; however, the findings are inconsistent. Therefore, we performed a meta-analysis to comprehensively evaluate such associations.

METHODS

We searched published literature from MEDLINE, EMBASE, Web of Science and CBM for eligible publications. We also assessed genotype-based mRNA expression data from HapMap for rs7799039 (G2548A) and rs1137101 (Q223R) in normal cell lines derived from 270 subjects with different ethnicities.

RESULTS

The final analysis included 16 published studies of 6569 cases and 8405 controls for the LEP G2548A and 19 studies of 7504 cases and 9581 controls for the LEPR Q223R. Overall, LEP G2548A was statistically significantly associated with an increased risk of overall cancer (AA vs. GG: OR=1.27, 95% CI=1.05-1.54; recessive model: OR=1.19, 95% CI=1.00-1.41). Further stratifications by cancer type showed an increased risk for prostate cancer (recessive model: OR=1.26, 95% CI=1.05-1.51) but not for other cancers. For LEPR Q223R, no statistical evidence for an association with risk of cancer was found for all; however, further stratification by ethnicity showed an increased risk for Africans but not for other ethnicities. No significantly differences in LEP and LEPR mRNA expression were found among genotypes or by ethnicity.

CONCLUSIONS

Despite some limitations, this meta-analysis found some statistical evidence for an association between the LEP 2548AA genotype and overall risk of cancer, particularly for prostate cancer, but given this variant did not have an effect on mRNA expression, this association warrants additional validation in large and well-designed studies.

Eicosanoids and adipokines in breast cancer: from molecular mechanisms to clinical considerations

Chronic inflammation is one of the foremost risk factors for different types of malignancies, including breast cancer. Additional risk factors of this pathology in postmenopausal women are weight gain, obesity, estrogen secretion, and an imbalance in the production of adipokines, such as leptin and adiponectin. Various signaling products of transcription factor, nuclear factor-kappaB, in particular inflammatory eicosanoids, reactive oxygen species (ROS), and cytokines, are thought to be involved in chronic inflammation-induced cancer. Together, these key components have an influence on inflammatory reactions in malignant tissue damage when their levels are deregulated endogenously. Prostaglandins (PGs) are well recognized in inflammation and cancer, and they are solely biosynthesized through cyclooxygenases (COXs) from arachidonic acid. Concurrently, ROS give rise to bioactive isoprostanes from arachidonic acid precursors that are also involved in acute and chronic inflammation, but their specific characteristics in breast cancer are less demonstrated. Higher aromatase activity, a cytochrome P-450 enzyme, is intimately connected to tumor growth in the breast through estrogen synthesis, and is interrelated to COXs that catalyze the formation of both inflammatory and anti-inflammatory PGs such as PGE(2), PGF(2α), PGD(2), and PGJ(2) synchronously under the influence of specific mediators and downstream enzymes. Some of the latter compounds upsurge the intracellular cyclic adenosine monophosphate concentration and appear to be associated with estrogen synthesis. This review discusses the role of COX- and ROS-catalyzed eicosanoids and adipokines in breast cancer, and therefore ranges from their molecular mechanisms to clinical aspects to understand the impact of inflammation.

The association between polymorphisms in the leptin receptor gene and risk of breast cancer: a systematic review and pooled analysis

Many epidemiological studies have found that leptin correlates to body fat extent and breast cancer. Leptin exerts its physiological action through the leptin receptor (LEPR). However, published data on the association between LEPR alleles and breast cancer occurrence have led to in contradictory results. A total of 10 studies were identified to the meta-analysis, including 4,644 cases and 5,485 controls for LEPR rs1137101 polymorphism, 5 studies with 2,759 cases and 4,464 controls for rs1137100 polymorphism, and 2 studies for rs8051542, rs8051542, and rs8051542 polymorphisms. The pooled odds ratios (OR) with 95 % confidence intervals (CI) for breast cancer risk associated with LEPR genotypes were estimated. Elevated breast cancer risk was associated with LEPR rs1137101 polymorphism when all studies were pooled in the meta-analysis (allele contrast model: OR = 0.71, 95 % CI = 0.551-0.997). In the stratified analysis by ethnicity, significantly increased risks were also found among Asians for allele contrast model (OR 0.414, 95 % CI 0.312-0.550) and dominant model (OR 0.537, 95 % CI 0.370-0.781); for Africans, significantly increased risks were also found for allele contrast model (OR 0.716, 95 % CI 0.595-0.861), homozygote codominant (OR 0.537, 95 % CI 0.370-0.781) and dominant model (OR 1.595, 95 % CI 1.207-2.108). And significantly elevated breast cancer risk was associated with LEPR rs1137100 polymorphism for allele contrast (OR = 0.666, 95 % CI = 0.603-0.720) and homozygote codominant models (OR = 0.344, 95 % CI = 0.282-0.421). For LEPR rs8179183, rs4655537, and rs3762274 polymorphisms, no significant associations were detected in all comparison models. This pooled analysis suggested that rs1137101 and rs1137100 polymorphisms were significantly correlated with breast cancer risk and the A allele of LEPR rs1137101 variant and the G allele of LEPR rs1137100 variant were low-penetrant risk factors for developing breast cancer. Further, no significant associations existed between LEPR rs8179183, rs4655537, and rs3762274 polymorphisms and risk of breast cancer.

Study of the leptin levels and its gene polymorphisms in patients with idiopathic short stature and growth hormone deficiency

Leptin levels may regulate fat metabolism, skeletal growth, and puberty. Leptin gene variants affect risk of obesity, cancer, but their effect on onset of growth hormone deficiency (GHD) and idiopathic short stature (ISS) is unknown. We tested the hypothesis that the phenotype of GHD and ISS may be associated with polymorphism in the leptin gene. The prevalence of a single nucleotide polymorphism (SNP) in the leptin gene (LEP) promoter at -2548 and the leptin and insulin growth factor-1 (IGF-1) concentrations in GHD and ISS were compared to those of healthy controls. IGF-1 and leptin concentrations were significantly lower in both the GHD and ISS groups than in the control group. The ISS and GHD groups had a significantly different distribution of SNP alleles at the LEP -2548 (P = 0.010). Individuals with LEP -2548A/G or G/G genotype in ISS group (47.5%) showed a significantly lower weight and body mass index (BMI) (but not leptin levels) than individuals carrying the A/A genotype (52.5%). LEP -2548A/A in GHD patients (65.8%) was associated with lower weight, BMI, leptin concentrations than those of individuals carrying the A/G or G/G genotype (34.2%). These data suggest that the LEP -2548A polymorphism may associate with the weight and BMI of the children with ISS and GHD.

Polymorphisms in three obesity-related genes (LEP, LEPR, and PON1) and breast cancer risk: a meta-analysis

Common genetic variations in the leptin (LEP), leptin receptor (LEPR), and paraoxonase 1 (PON1) genes have been considered to be implicated in the development of breast cancer. However, the results were inconsistent. In this study, a meta-analysis was performed to assess the associations of five polymorphisms, including LEP G2548A, LEPR Q223R, LEPR Lys109Arg, PON1 L55M, and PON1 Q192R polymorphisms, with breast cancer risk. Published literature from PubMed, ISI Web of Science, Embase databases, CNKI, and Wanfang Data were retrieved. All studies evaluating the association between LEP G2548A, LEPR Q223R, LEPR Lys109Arg, PON1 L55M, or PON1 Q192R polymorphism and breast cancer risk were included. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects model. Three studies (2,003 cases and 1,967 controls) for LEP G2548A polymorphism, nine studies (4,627 cases and 5,476 controls) for LEPR Q223R polymorphism, five studies (2,759 cases and 2,573 controls) for LEPR Lys109Arg polymorphism, four studies (1,517 cases and 1,379 controls) for PON1 L55M polymorphism, and five studies (1,575 cases and 2,283 controls) for PON1 Q192R polymorphism were included in the meta-analysis. Overall, the results showed null significant association between LEP G2548A, LEPR Q223R, LEPR Lys109Arg, or PON1 Q192R polymorphism and breast cancer risk; however, PON1 L55M was significantly associated with breast cancer risk overall (MM vs. LL: OR = 2.16; 95% CI, 1.76-2.66). For LEPR Q223R polymorphism, further subgroup analysis suggested that the association was only statistically significant in East Asians (OR = 0.50; 95% CI, 0.36-0.70) but not in Caucasians (OR = 1.06; 95% CI, 0.77-1.45) or Africans (OR = 1.30; 95% CI, 0.83-2.03). The present meta-analysis suggested that LEPR Q223R polymorphism might be implicated in the development of breast cancer in East Asians; PON1 L55M might increase breast cancer risk. However, given the limited sample size, the findings warrant further investigation.

Genetic polymorphisms in obesity-related genes and endometrial cancer risk

BACKGROUND

Obesity is associated with circulating levels of adiponectin and leptin and endometrial cancer risk. Little is known about whether single nucleotide polymorphisms (SNPs) in the genes that encode adiponectin (ADIPOQ), leptin (LEP), adiponectin receptor 1 (ADIPOR1), adiponectin receptor 2 (ADIPOR2), and leptin receptor (LEPR) are associated with endometrial cancer.

METHODS

The authors selected 87 tagging SNPs to capture common genetic variants in these 5 genes. These SNPs were evaluated in 1028 endometrial cancer cases and 1932 community controls recruited from Chinese women. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

Three of the 10 SNPs evaluated in the ADIPOQ gene were significantly associated with reduced cancer risk. The OR for women homozygous for the minor allele (A/A) for rs3774262 was 0.68 (95% CI, 0.48-0.97) compared with women homozygous for the major allele (G/G). Similar results were found for SNPs rs1063539 and rs12629945 in ADIPOQ, which were in linkage disequilibrium with rs3774262. These associations became nonsignificant after Bonferroni correction was applied. Controls with the minor allele A at rs3774262 had lower weight, smaller waist and hip circumferences, and lower body mass index than controls with the major allele G (all P < .05). Women homozygous for the minor allele (T/T) of rs2071045 in the LEP gene also had significantly lower risk (OR, 0.70; 95% CI, 0.54-0.90) than women homozygous for the major allele (C/C). No other SNPs in the LEP, ADIPOR1, ADIPOR2, or LEPR genes were found to be associated with cancer risk.

CONCLUSIONS

Although a chance finding cannot be ruled out, the consistency of findings for gene-endometrial cancer risk and gene-obesity measurements suggests that genetic polymorphisms in the ADIPOQ gene may play a role in endometrial cancer development.

Leptin and leptin receptor genes in relation to premenopausal breast cancer incidence and grade in Caucasian women

Body mass is inversely related to breast cancer risk among premenopausal women. Leptin, an essential cytokine regulating food intake, energy expenditure, glucose, and fat metabolism may be part of the mechanistic pathway. We investigated 50 tagging and candidate SNPs in the leptin (LEP) and leptin receptor (LEPR) genes for associations with premenopausal breast cancer incidence using 405 cases and 810 controls nested within the Nurses' Health Study II. We also examined associations between these SNPs and circulating leptin (among 910 women) and breast cancer grade (among 267 patients). Permutation tests were performed to adjust for multiple testing. We did not detect a significant association between SNPs in the LEP or LEPR gene and either breast cancer incidence or plasma leptin levels. Among cases, 14 SNPs of the LEPR gene were significantly associated with cancer grade, and rs1137101 (Q223R) survived multiple testing adjustment (adjusted P = 0.04). The G carriers of rs1137101 were more likely to have poorly differentiated than well-differentiated cancers. Our data suggest that common genetic variation in the LEP or LEPR gene has no strong association with premenopausal breast cancer risk. The LEPR gene might be associated with breast cancer grade.

Common genetic variation in adiponectin, leptin, and leptin receptor and association with breast cancer subtypes

Adipocytokines are produced by visceral fat, and levels may be associated with breast cancer risk. We investigated whether single nucleotide polymorphisms (SNPs) in adipocytokine genes adiponectin (ADIPOQ), leptin (LEP), and the leptin receptor (LEPR) were associated with basal-like or luminal A breast cancer subtypes. 104 candidate and tag SNPs were genotyped in 1776 of 2022 controls and 1972 (200 basal-like, 679 luminal A) of 2311 cases from the Carolina Breast Cancer Study (CBCS), a population-based case-control study of whites and African Americans. Breast cancer molecular subtypes were determined by immunohistochemistry. Genotype odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. Haplotype ORs and 95% CIs were estimated using Hapstat. Interactions with waist-hip ratio were evaluated using a multiplicative interaction term. Ancestry was estimated from 144 ancestry informative markers (AIMs), and included in models to control for population stratification. Candidate SNPs LEPR K109R (rs1137100) and LEPR Q223R (rs1137101) were positively associated with luminal A breast cancer, whereas ADIPOQ +45 T/G (rs2241766), ADIPOQ +276 G/T (rs1501299), and LEPR K656N (rs8129183) were not associated with either subtype. Few patterns were observed among tag SNPs, with the exception of 3 LEPR SNPs (rs17412175, rs9436746, and rs9436748) that were in moderate LD and inversely associated with basal-like breast cancer. However, no SNP associations were statistically significant after adjustment for multiple comparisons. Haplotypes in LEP and LEPR were associated with both basal-like and luminal A subtypes. There was no evidence of interaction with waist-hip ratio. Data suggest associations between LEPR candidate SNPs and luminal A breast cancer in the CBCS and LEPR intron 2 tag SNPs and basal-like breast cancer. Replication in additional studies where breast cancer subtypes have been defined is necessary to confirm these potential associations.

Hormonal mechanisms underlying the relationship between obesity and breast cancer

Given the worldwide epidemic of obesity, it is inevitably an increasingly common comorbidity for women who develop breast cancer; therefore, it is critical to understand its impact on this disease. This review focuses on the influence of obesity on breast cancer development and progression and describes the hormonal factors that may underlie the observations, with particular emphasis on the roles of estrogen, insulin/insulin-like growth factor axis, and adipokines.

Leptin pro-angiogenic signature in breast cancer is linked to IL-1 signalling

BACKGROUND

Leptin and interleukin-1 (IL-1) upregulate vascular endothelial growth factor (VEGF), promote angiogenesis and are related to worse prognosis of breast cancer. However, it is unknown whether leptin regulates IL-1, and whether these effects are related to leptin-induction of VEGF/VEGFR2 in breast cancer.

METHODS

Several genetic and pharmacological approaches were used to determine the mechanisms involved in leptin regulation of IL-1 system (IL-1α, IL-1β, IL-1Ra and IL-1R tI) and the impact of IL-1 signalling on leptin-induced VEGF/VEGFR2 expression in mouse mammary cancer 4T1 cells (a model that resembles invasive and highly metastatic human breast cancer).

RESULTS

Leptin increased protein and mRNA levels of all components of the IL-1 system. IL-1 upregulation involved leptin activation of JAK2/STAT3, MAPK/ERK 1/2, PI-3K/AKT1, PKC, p38 and JNK. Leptin-induced phosphorylation of mTOR/4E-BP1 increased IL-1β and IL-1Ra expression, but downregulated IL-1α. Leptin upregulation of IL-1α promoter was linked to SP1 and NF-κB transcription factors. In addition, leptin receptor (Ob-Rb) was upregulated by leptin. Interestingly, leptin upregulation of VEGF/VEGFR2 was partially mediated by IL-1/IL-1R tI signalling.

CONCLUSIONS

We show for the first time that leptin induces several signalling pathways to upregulate the translational and transcriptional expression of IL-1 system in breast cancer cells. Moreover, leptin upregulation of VEGF/VEGFR2 was impaired by IL-1 signalling blockade. These data suggest that leptin pro-angiogenic signature in breast cancer is linked to, or regulated, in part by IL-1 signalling.