Leptin and prostate: implications for cancer prevention--overview of genetics and molecular interactions

Periprostatic adipose tissue inhibits tumor progression by secreting apoptotic factors: A natural barrier induced by the immune response during the early stages of prostate cancer

Prostate cancer (PCa) is the second most prevalent malignancy in men worldwide. The risk factors for PCa include obesity, age and family history. Increased visceral fat has been associated with high PCa risk, which has prompted previous researchers to investigate the influence of body composition and fat distribution on PCa prognosis. However, there is a lack of studies focusing on the mechanisms and interactions between periprostatic adipose tissue (PPAT) and PCa cells. The present study investigated the association between the composition of pelvic adipose tissue and PCa aggressiveness to understand the role played by this tissue in PCa progression. Moreover, PPAT-conditioned medium (CM) was prepared to assess the influence of the PPAT secretome on the pathophysiology of PCa. The present study included 50 patients with localized PCa who received robot-assisted radical prostatectomy. Medical records were collected, magnetic resonance imaging scans were analyzed and body compositions were calculated to identify the associations between adipose tissue volume and clinical PCa aggressiveness. In addition, CM was prepared from PPAT and perivesical adipose tissue (PVAT) collected from 25 patients during surgery, and its effects on the PCa cell lines C4-2 and LNCaP, and the prostate epithelial cell line PZ-HPV-7, were investigated using a cell proliferation assay and RNA sequencing (RNA-seq). The results revealed that the initial prostate-specific antigen level was significantly correlated with pelvic and periprostatic adipose tissue volumes. In addition, PPAT volume was significantly higher in patients with extracapsular tumor extension. PCa cell proliferation was significantly reduced when the cells were cultured in PPAT-CM compared with when they were cultured in control- and PVAT-CM. RNA-seq revealed that immune responses, and the cell death and apoptosis pathways were enriched in PPAT-CM-cultured cells indicating that the cytokines or other factors secreted from PPAT-CM induced PCa cell apoptosis. These findings revealed that the PPAT secretome may inhibit PCa cell proliferation by activating immune responses and promoting cancer cell apoptosis. This mechanism may act as a first-line defense during the early stages of PCa.

Association Between Diabetes and Risk of Prostate Cancer: A Systematic Review and Meta-Analysis of Observational Studies

PURPOSE

Metabolic diseases such as diabetes mellitus may play a role in the development and progression of prostate cancer (PC); however, this association remains to be explored in the context of specific PC stages. The objective of this study was to systematically review the evidence for an association between diabetes and overall, early, or advanced PC risk.

MATERIALS AND METHODS

A systematic review with meta-analysis was performed (MEDLINE, EMBASE, and CINAHL) from inception until September 2023. Cohort and case-control studies that assessed PC risk in adult males (≥18 years) associated with type 2 diabetes mellitus or diabetes (if there was no distinction between diabetes type) were included. The Newcastle-Ottawa Scale (NOS) was used to assess study bias; those with NOS<7 were excluded. Evidence certainty was assessed with the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) method.

RESULTS

Thirty-four studies (n=26 cohorts and n=8 case-controls) were included. Of these, 32 assessed diabetes and all PC stages combined, 12 included early PC stages, and 15 included advanced PC stages. Our meta-analysis showed diabetes had a protective effect against early PC development (n=11, risk ratio [RR]=0.71; 95% confidence interval [CI]=0.61-0.83, I²=84%) but no association was found for combined (n=21, RR=0.95; 95% CI=0.79-1.13, I²=99%) or advanced PC stages (n=15, RR=0.96; 95% CI=0.77-1.18, I²=98%) at diagnosis. According to GRADE, the evidence certainty was very low.

CONCLUSIONS

Diabetes may be protective against early PC stages, yet evidence linking diabetes to risk across all stages, and advanced PC specifically, is less conclusive. High heterogeneity may partially explain discrepancy in findings and was mostly associated with study design, method used for PC diagnosis, and risk measures. Our results may aid risk stratification of males with diabetes and inform new approaches for PC screening in this group, especially considering the reduced sensitivity of prostate-specific antigen values for those with diabetes.

Regulatory role of local tissue signal Del-1 in cancer and inflammation: a review

Developmental endothelial locus-1 (Del-1) is a secretory, multifunctional domain protein. It can bind to integrins and phosphatidylserine. As a local tissue signal, it plays a regulatory role in the cancer microenvironment and inflammation. Del-1 has destructive effects in most cancers and is associated with the progression and invasion of some cancers. In contrast, Del-1 also plays a protective role in inflammation. Del-1 regulates inflammation by regulating the generation of neutrophils in bone marrow, inhibiting the recruitment and migration of neutrophils and accelerating the clearance of neutrophils by macrophages. Del-1 and IL-17 are reciprocally regulated, and their balance maintains immune system homeostasis. Del-1 is expected to become a new therapeutic target for inflammatory disorders such as multiple sclerosis.

Hypothalamic leptin gene therapy reduces body weight without accelerating age-related bone loss

Excessive weight gain in adults is associated with a variety of negative health outcomes. Unfortunately, dieting, exercise, and pharmacological interventions have had limited long-term success in weight control and can result in detrimental side effects, including accelerating age-related cancellous bone loss. We investigated the efficacy of using hypothalamic leptin gene therapy as an alternative method for reducing weight in skeletally-mature (9 months old) female rats and determined the impact of leptin-induced weight loss on bone mass, density, and microarchitecture, and serum biomarkers of bone turnover (CTx and osteocalcin). Rats were implanted with cannulae in the 3rd ventricle of the hypothalamus and injected with either recombinant adeno-associated virus encoding the gene for rat leptin (rAAV-Leptin, n=7) or a control vector encoding green fluorescent protein (rAAV-GFP, n=10) and sacrificed 18 weeks later. A baseline control group (n=7) was sacrificed at vector administration. rAAV-Leptin-treated rats lost weight (-4±2%) while rAAV-GFP-treated rats gained weight (14±2%) during the study. At study termination, rAAV-Leptin-treated rats weighed 17% less than rAAV-GFP-treated rats and had lower abdominal white adipose tissue weight (-80%), serum leptin (-77%), and serum IGF1 (-34%). Cancellous bone volume fraction in distal femur metaphysis and epiphysis, and in lumbar vertebra tended to be lower (P<0.1) in rAAV-GFP-treated rats (13.5 months old) compared to baseline control rats (9 months old). Significant differences in cancellous bone or biomarkers of bone turnover were not detected between rAAV-Leptin and rAAV-GFP rats. In summary, rAAV-Leptin-treated rats maintained a lower body weight compared to baseline and rAAV-GFP-treated rats with minimal effects on bone mass, density, microarchitecture, or biochemical markers of bone turnover.

Leptin signaling molecular actions and drug target in hepatocellular carcinoma

Previous reports indicate that over 13 different tumors, including hepatocellular carcinoma (HCC), are related to obesity. Obesity-associated inflammatory, metabolic, and endocrine mediators, as well as the functioning of the gut microbiota, are suspected to contribute to tumorigenesis. In obese people, proinflammatory cytokines/chemokines including tumor necrosis factor-alpha, interleukin (IL)-1 and IL-6, insulin and insulin-like growth factors, adipokines, plasminogen activator inhibitor-1, adiponectin, and leptin are found to play crucial roles in the initiation and development of cancer. The cytokines induced by leptin in adipose tissue or tumor cells have been intensely studied. Leptin-induced signaling pathways are critical for biological functions such as adiposity, energy balance, endocrine function, immune reaction, and angiogenesis as well as oncogenesis. Leptin is an activator of cell proliferation and anti-apoptosis in several cell types, and an inducer of cancer stem cells; its critical roles in tumorigenesis are based on its oncogenic, mitogenic, proinflammatory, and pro-angiogenic actions. This review provides an update of the pathological effects of leptin signaling with special emphasis on potential molecular mechanisms and therapeutic targeting, which could potentially be used in future clinical settings. In addition, leptin-induced angiogenic ability and molecular mechanisms in HCC are discussed. The stringent binding affinity of leptin and its receptor Ob-R, as well as the highly upregulated expression of both leptin and Ob-R in cancer cells compared to normal cells, makes leptin an ideal drug target for the prevention and treatment of HCC, especially in obese patients.

Oncogenic role and therapeutic target of leptin signaling in colorectal cancer

INTRODUCTION

Obesity is characterized by high secretion of several cytokines from adipose tissue and is a recognized risk factor for many cancers. Among these cytokines, leptin mainly produced by adipose tissue and cancer cells is the most studied adipokine. Leptin is an activator of cell proliferation, an antiapoptotic molecule and inducer of cancer stem cells in many cell types, and its critical roles in obesity-related tumorigenesis are based on its oncogenic, mitogenic, pro-inflammatory and pro-angiogenic actions.

AREAS COVERED

These leptin-induced signals and action are critical for their biological effects on energy balance, adiposity, endocrine systems, immunity, angiogenesis as well as oncogenesis. This review focuses on the up-to-date knowledge on the oncogenic role of leptin signaling, clinical significance and specific drug target development in colorectal cancer (CRC). Additionally, leptin-induced angiogenic ability and molecular mechanisms in CRC cells are discussed.

EXPERT OPINION

Stringent binding affinity of leptin/Ob-R and overexpression of leptin/Ob-R and their targets in cancer cells make it a unique drug target for prevention and treatment of CRC, particularly in obesity colorectal patients.

Association between biomarkers of obesity and risk of high-grade prostatic intraepithelial neoplasia and prostate cancer--evidence of effect modification by prostate size

Prostate enlargement is common with aging and obesity. We investigated the association between obesity and prostate cancer controlling for differential detection related to prostate enlargement. In an analysis of 500 men, we found body mass index, waist-hip ratio, and blood leptin levels were significantly associated with high-grade PC, but only among men without prostate enlargement. Leptin was also significantly associated with high-grade prostatic intraepithelial neoplasia (HGPIN) in the absence of prostate enlargement. Our results suggest obesity advances prostate carcinogenesis, and that detection biases at prostate biopsy may explain past inconsistencies in the association between obesity and PC.

The adipocyte-derived hormone leptin has proliferative actions on androgen-resistant prostate cancer cells linking obesity to advanced stages of prostate cancer

Background. Because obesity may be a risk factor for prostate cancer, we investigated proliferative effects of adipocytes-derived hormone leptin on human prostate cancer cells and assessed the role of mitogen-activated protein kinase (MAPK) signaling pathway in mediating these actions. Material and Methods. Three human prostate cancer cell lines were treated with increasing doses of recombinant leptin. Cell growth was measured under serum-free conditions using a spectrophotometric assay. Further, Western blotting was applied to detect the phosphorylation of an ERK1/2, and a specific inhibitor of MAPK (PD98059; 40 μM) was used. Results. In both androgen-resistant cell lines DU145 and PC-3, cell growth was dose-dependently increased by leptin after 24 hrs and 48 hrs of incubation, whereas leptin's proliferative effects on androgen-sensitive cell line LNCaP was less pronounced. Further, leptin caused dose-dependent ERK1/2 phosphorylation in both androgen-resistant cell lines, and pretreatment of these cells with PD98059 inhibited these responses. Conclusions. Leptin may be a potential link between obesity and risk of progression of prostate cancer. Thus, studies on leptin and obesity association to prostate cancer should differentiate patients according to androgen sensitivity.

Oncogenic role and therapeutic target of leptin signaling in breast cancer and cancer stem cells

Significant correlations between obesity and incidence of various cancers have been reported. Obesity, considered a mild inflammatory process, is characterized by a high level of secretion of several cytokines from adipose tissue. These molecules have disparate effects, which could be relevant to cancer development. Among the inflammatory molecules, leptin, mainly produced by adipose tissue and overexpressed with its receptor (Ob-R) in cancer cells is the most studied adipokine. Mutations of leptin or Ob-R genes associated with obesity or cancer are rarely found. However, leptin is an anti-apoptotic molecule in many cell types, and its central roles in obesity-related cancers are based on its pro-angiogenic, pro-inflammatory and mitogenic actions. Notably, these leptin actions are commonly reinforced through entangled crosstalk with multiple oncogenes, cytokines and growth factors. Leptin-induced signals comprise several pathways commonly triggered by many cytokines (i.e., canonical: JAK2/STAT; MAPK/ERK1/2 and PI-3K/AKT1 and, non-canonical signaling pathways: PKC, JNK and p38 MAP kinase). Each of these leptin-induced signals is essential to its biological effects on food intake, energy balance, adiposity, immune and endocrine systems, as well as oncogenesis. This review is mainly focused on the current knowledge of the oncogenic role of leptin in breast cancer. Additionally, leptin pro-angiogenic molecular mechanisms and its potential role in breast cancer stem cells will be reviewed. Strict biunivocal binding-affinity and activation of leptin/Ob-R complex makes it a unique molecular target for prevention and treatment of breast cancer, particularly in obesity contexts.

Oncogenic role and therapeutic target of leptin signaling in breast cancer and cancer stem cells

Significant correlations between obesity and incidence of various cancers have been reported. Obesity, considered a mild inflammatory process, is characterized by a high level of secretion of several cytokines from adipose tissue. These molecules have disparate effects, which could be relevant to cancer development. Among the inflammatory molecules, leptin, mainly produced by adipose tissue and overexpressed with its receptor (Ob-R) in cancer cells is the most studied adipokine. Mutations of leptin or Ob-R genes associated with obesity or cancer are rarely found. However, leptin is an anti-apoptotic molecule in many cell types, and its central roles in obesity-related cancers are based on its pro-angiogenic, pro-inflammatory and mitogenic actions. Notably, these leptin actions are commonly reinforced through entangled crosstalk with multiple oncogenes, cytokines and growth factors. Leptin-induced signals comprise several pathways commonly triggered by many cytokines (i.e., canonical: JAK2/STAT; MAPK/ERK1/2 and PI-3K/AKT1 and, non-canonical signaling pathways: PKC, JNK and p38 MAP kinase). Each of these leptin-induced signals is essential to its biological effects on food intake, energy balance, adiposity, immune and endocrine systems, as well as oncogenesis. This review is mainly focused on the current knowledge of the oncogenic role of leptin in breast cancer. Additionally, leptin pro-angiogenic molecular mechanisms and its potential role in breast cancer stem cells will be reviewed. Strict biunivocal binding-affinity and activation of leptin/Ob-R complex makes it a unique molecular target for prevention and treatment of breast cancer, particularly in obesity contexts.

Genetic variants in the LEPR, CRY1, RNASEL, IL4, and ARVCF genes are prognostic markers of prostate cancer-specific mortality

BACKGROUND

Prostate cancer is the second leading cause of cancer-related deaths in men, accounting for more than 30,000 deaths annually. The purpose of this study was to test whether variation in selected candidate genes in biological pathways of interest for prostate cancer progression could help distinguish patients at higher risk for fatal prostate cancer.

METHODS

In this hypothesis-driven study, we genotyped 937 single nucleotide polymorphisms (SNPs) in 156 candidate genes in a population-based cohort of 1,309 prostate cancer patients. We identified 22 top-ranking SNPs (P ≤ 0.01, FDR ≤ 0.70) associated with prostate cancer-specific mortality (PCSM). A subsequent validation study was completed in an independent population-based cohort of 2,875 prostate cancer patients.

RESULTS

Five SNPs were validated (P ≤ 0.05) as being significantly associated with PCSM, one each in the LEPR, CRY1, RNASEL, IL4, and ARVCF genes. Compared with patients with 0 to 2 of the at-risk genotypes those with 4 to 5 at-risk genotypes had a 50% (95% CI, 1.2-1.9) higher risk of PCSM and risk increased with the number of at-risk genotypes carried (P(trend) = 0.001), adjusting for clinicopathologic factors known to influence prognosis.

CONCLUSION

Five genetic markers were validated to be associated with lethal prostate cancer.

IMPACT

This is the first population-based study to show that germline genetic variants provide prognostic information for prostate cancer-specific survival. The clinical utility of this five-SNP panel to stratify patients at higher risk for adverse outcomes should be evaluated.

Polymorphic variants of DNA repair gene XRCC3 and XRCC7 and risk of prostate cancer: a study from North Indian population

DNA repair gene alterations may cause a reduction in DNA repair capacity and influence an individual's susceptibility to carcinogenesis. We hypothesized that single nucleotide polymorphisms of DNA repair genes may be a risk factor for prostate cancer (PCa) susceptibility, influencing expression of homologous recombination (XRCC3) and nonhomologous end-joining (XRCC7) genes and conferring predisposition to PCa. In a case-control study, genotyping was done in 192 patients with PCa and 224 age matched unrelated healthy controls of similar ethnicity to determine variants in XRCC3 Exon 7 (C18067T, rs861539), IVS5-14 (A17893G, rs1799796), and XRCC7 Intron 8 (G6721T, rs7003908) by polymerase chain reaction-restriction fragment-length polymorphism methods. Variant genotype GG (odds ratio [OR], 2.23; p=0.003) and combined genotype TG+GG (OR, 1.541; p=0.049), G allele of XRCC7 Intron 8 (G>T), demonstrated significant risk for PCa (OR, 1.529; p=0.002). Stratification on bases of Gleason grade and bone metastasis, significant risk with high Gleason grade for CT genotype of XRCC3 Exon 7, and variant genotype GG of XRCC7 Intron 8 were observed. Our results strongly support that common sequence variants (GG) genotype of XRCC7 may increase risk of PCa. G allele being a risk allele in our study also suggests that this polymorphism be used as a marker for the PCa susceptibility.

Adipokine genes and prostate cancer risk

Adiposity and adipocyte-derived cytokines have been implicated in prostate carcinogenesis. However, the relationship of adipokine gene variants with prostate cancer risk has not been thoroughly investigated. We therefore examined common variants of the IL6, LEP, LEPR, TNF and ADIPOQ genes in relation to prostate cancer in a case-control study nested within a large cohort of Finnish men. The study sample consisted of 1,053 cases of prostate cancer, diagnosed over an average 11 years of follow up, and 1,053 controls matched to the cases on age, intervention group and date of baseline blood draw. Logistic regression was used to model the relative odds of prostate cancer. We also examined genotypes in relation to serum insulin, IGF-1 and IGF-1:IGFBP-3 among 196 controls. Variant alleles at three loci (-14858A>G, -13973A>C, -13736C>A) in a potential regulatory region of the LEP gene conferred a statistically significant 20% reduced risk of prostate cancer. For example, at the -14858A>G locus, heterozygotes and homozygotes for the A allele had an odds ratio (OR) of prostate cancer of 0.76 [95% confidence interval (CI) 0.62, 0.93] and 0.79 (95% CI 0.60, 1.04), respectively. At 13288G>A, relative to the GG genotype, the AA genotype was associated with a suggestive increased risk of prostate cancer (OR = 1.29; 95% CI 0.99,1.67; p(trend) = 0.05). Polymorphisms in the IL6, LEPR, TNF and ADIPOQ genes were not associated with prostate cancer. Allelic variants in the LEP gene are related to prostate cancer risk, supporting a role for leptin in prostate carcinogenesis.

The role of adhesion molecules, alpha v beta 3, alpha v beta 5 and their ligands in the tumor cell and endothelial cell adhesion

Tumor metastasis is a complex process involving the interaction between tumor cells and endothelial cells in which some adhesion molecules play an important role. It was our aim to investigate the role of the adhesion molecules, alpha v beta 3 and alpha v beta 5 and their ligands, developmental endothelial locus-1 (Del-1) and L1, in tumor cell adhesion to endothelial cells in vitro. In this study, the expression and regulation of alpha v beta 3, alpha v beta 5 and intercellular adhesion molecule -1 on liver sinusoidal endothelial cells and liver cancer endothelial cells (T3A) were analyzed by real-time PCR and fluorescent-activated cell sorter. The expression and regulation of the integrin ligands, Del-1 and L1, in six tumor cell lines were analyzed by real-time PCR and western blot. We found the expressions of alpha v beta 3 and alpha v beta 5 were higher on T3A than that on liver sinusoidal endothelial cells, whereas expression of intercellular adhesion molecule-1 was lower on T3A than that on liver sinusoidal endothelial cells. After 24 h hypoxia, the expressions of alpha v beta 3 and alpha v beta 5 were upregulated on T3A and liver sinusoidal endothelial cells; the expression of intercellular adhesion molecule-1 was increased on liver sinusoidal endothelial cells, but remained unchanged on T3A. Del-1 and L1 expression levels were obviously diverse in various tumor cell lines and differentially modulated after 12 h hypoxia. The adhesion of tumor cells with Del-1 and L1 expression was higher in T3A than that in liver sinusoidal endothelial cells, and was significantly increased under hypoxic conditions. Interestingly, the tumor cell adherence could be inhibited by antibodies against alpha v beta 5 and alpha v beta 5, but not by an antibody against intercellular adhesion molecule-1. The adhesion of tumor cells without Del-1 and L1 expression was also higher on T3A than that on liver sinusoidal endothelial cells, but the adhesion could not be inhibited by antibodies against alpha v beta 5, alpha v beta 5 or intercellular adhesion molecule-1, suggesting that other receptors are involved. In conclusion, alpha v beta 5, alpha v beta 5 and their ligands Del-1 and L1 play an important role in the process of tumor cells moving from the original place.

The CYP3A4∗1B polymorphism and prostate cancer susceptibility in a Portuguese population

Testosterone exposure has been implicated in prostate carcinogenesis, and genes that alter its metabolism, such as CYP3A4, have been associated with prostate cancer susceptibility. The aim of our study was to assess the relationship between the CYP3A4 *1B polymorphism and its possible role in the development of prostate cancer. DNA samples obtained from the peripheral blood cells of 414 individuals diagnosed with prostate cancer and 337 healthy male donors were used in this case-control study. The CYP3A4*1B polymorphism was analyzed by polymerase chain reaction-restriction fragment length polymorphism methodology. We found no statistically significant differences in the distribution of the CYP3A4*1B genotypes between cases and controls (P = 0.470; odds ratio = 1.191; 95% confidence interval=0.740-1.918), as well as after the stratification of our analysis, according to important clinicopathologic parameters of prostate cancer. Our results suggest that the CYP3A4*1B polymorphism is not associated with prostate cancer risk within the Portuguese population.

Association between FAS polymorphism and prostate cancer development

The role of FAS polymorphisms in prostate cancer has not been studied. Using the PCR-based restriction fragment-length polymorphism methodology, we evaluated FAS gene locus -670 genotypes in DNA from 904 men: 657 prostate cancer patients and 247 healthy controls. We found that carriers of AG or GG genotypes have a statistically significant protection (odds ratio (OR)=0.30; confidence interval (CI): 0.20-0.44 and OR=0.22; CI: 0.12-0.74, respectively) for disease with extra-capsular invasion. Taken together, a 72% protection was found for G allele carriers (OR=0.28; CI: 0.19-0.41). Fas exist as membrane-bound and soluble forms and with opposite roles. They derive from the same gene by alternative splicing. Membrane Fas receptors trigger apoptosis whereas, on the other hand, soluble Fas (sFas) bind to Fas ligand antagonizing Fas-Fas ligand apoptotic pathway. Our results suggest that G allele may reduce sFas levels preventing the apoptotic inhibition caused by the soluble form.

Diabetes and the risk of prostate cancer: the role of diabetes treatment and complications

Epidemiologic evidence suggests diabetic men have a slightly lower prostate cancer risk than non-diabetic men. We examined this association in a prospective cohort study of 35 239 men, 50-76 years old, in Washington State who completed a baseline questionnaire between 2000 and 2002. Incident prostate cancers as of 31 December 2004 were identified through the SEER registry. Diabetic men had a slightly lower risk of prostate cancer than non-diabetic men (hazard ratio (HR) 0.83, 95% confidence interval (CI) 0.64-1.07). Insulin users overall and insulin users with diabetic complications had decreased risks, compared to non-diabetic men (HR 0.49, 95% CI 0.26-0.92) and (HR 0.36, 95% CI 0.15-0.87), respectively. Oral medication use for diabetes was not associated with prostate cancer. Insulin is likely a marker of severity of diabetes. Future studies of this association should consider diabetes type, treatment, severity, complications and biomarkers.

Molecular Interactions of Leptin and Prostate Cancer

BACKGROUND

Epidemiological studies have found obesity to be a risk factor for prostate cancer. Our prior independent studies in women have reported a strong relationship between variants of OB (leptin) gene, body mass index, and age at menarche and sporadic breast cancer. The current study investigates an association between genetic variants of the human obesity gene, serum leptin levels, and body mass index in subjects with prostate carcinoma and in age- and gender-matched normal subjects.

METHODS

Blood samples from 69 patients with prostate cancer and 137 age-matched control subjects were collected. Serum leptin level was investigated by radioimmunoassay, and body mass index was calculated. Allele sizes were determined via standard polymerase chain reaction. Statistical analysis was performed using SPSS10.0 computer software.

RESULTS

There was a strong association with significantly elevated serum leptin levels, high body mass index, and higher frequency of LEPR longer alleles in patients with prostate cancer than in control subjects. By contrast, a modest but not significant increase in the frequency of LEP short alleles was found in patients with prostate cancer as compared with control subjects. Analysis within groups 1 (low leptin level and low body mass index) and 2 (other) showed a significant association only in group 2, with high frequency of OB gene variants (LEPR long alleles and LEP short alleles) in patients with prostate cancer but not in control subjects.

CONCLUSIONS

These results represent the first report of a significant association between specific leptin gene alleles, serum leptin levels, and body mass index in subjects with prostate cancer. Consistent with prior reports, we also report a significantly elevated serum leptin level in patients with prostate cancer, suggesting a strong link with obesity as an increased risk factor.

The link between obesity and prostate cancer: the leptin pathway and therapeutic perspectives

Obesity-associated prostate cancer (PCa) remains controversial, although most studies rely on body mass index evaluation, which is an indirect measure of fatness. Studies using body fat measurement and disease stratification according to PCa stage found stronger associations between obesity and PCa. Leptin is a pleiotrophic hormone mainly synthesized by adipocytes that acts in peripheral organs such as the prostate. This article reviews obesity-associated leptin's pathophysiological role in PCa progression. PCa development results from some known risk factors. Currently, there is enough evidence suggesting that leptin is an additional factor involved in advanced PCa occurrence, and obesity association with high-grade disease. Life-long exposure to genetic and/or environmental susceptibility factors that predispose to obesity and higher leptin levels may increase the risk for advanced PCa.

A functional polymorphism in the promoter region of leptin gene increases susceptibility for non-small cell lung cancer

Leptin hormone and receptor have been associated to cancer development and were identified in lung tissue. In this study, a functional polymorphism in the 5' flanking region of the leptin gene (LEP -2548 G/A) was found to increase susceptibility for non-small cell lung cancer [odds ratio (OR), 1.97; 95% confidence interval (CI), 1.13-3.43]. Age-adjusted logistic regression analysis in men indicated an association of AA genotype with adenocarcinoma (OR, 4.29; CI, 1.64-11.72) and squamous cell carcinoma (OR, 3.19; CI, 1.26-8.13). Logistic regression analysis confirmed the AA genotype as an independent risk factor for lung cancer after adjustment for age and gender (OR, 2.57; CI, 1.34-4.92). The AA genotype was overrepresented only in patients with non-metastatic disease (OR, 1.86; CI, 1.13-3.04). Kaplan-Meier analysis demonstrated an earlier age of onset for lung cancer in AA carriers (P=0.023). Results suggest the existence of genetic susceptibility for lung cancer in carriers of this LEP functional polymorphism. Further studies are warranted to extend knowledge of leptin involvement in lung cancer.

Association of body mass index and height with risk of prostate cancer among middle-aged Japanese men

In a population-based prospective study of 49 850 Japanese men, body mass index and height were not significantly associated with risk of prostate cancer (311 cases), although small positive effects could not be ruled out in advanced cases (91 cases).

Hyperglycemia and insulin resistance in men with prostate carcinoma who receive androgen-deprivation therapy

BACKGROUND

Prostate carcinoma (PCa) is one of the most common malignancies in men. Androgen-deprivation therapy (ADT) is used frequently in the treatment of recurrent and metastatic PCa, rendering these men hypogonadal. Because male hypogonadism is associated with an unfavorable metabolic profile, and men with PCa have high cardiovascular mortality, the authors evaluated the effects of long-term ADT on fasting glucose levels, insulin levels, and insulin resistance.

METHODS

To evaluate the long-term effects of ADT on fasting glucose and insulin resistance in men with PCa who received ADT and to determine whether these metabolic alterations are a result of hypogonadism, the authors conducted a cross-sectional study at a university-based research institution in the United States. In total, 53 men were evaluated, including 18 men with PCa who received ADT for at least 12 months prior to the onset of the study (the ADT group), 17 age-matched men with nonmetastatic PCa who had undergone prostatectomy and/or received radiotherapy and who were not receiving ADT (the non-ADT group), and 18 age-matched controls (the control group). None of the men had a known history of diabetes mellitus.

RESULTS

The mean age was similar in all 3 groups (P=0.33). Serum total testosterone levels (P<0.0001) and free testosterone levels (P<0.0001) were significantly lower in the ADT group compared with the other groups. Men in the ADT group had a higher BMI compared with the other groups (overall P=0.005). After adjustment for age and BMI, men in the ADT group had significantly higher fasting levels of the following parameters: 1) Glucose levels were 131.0+/-7.43 mg/dL in the ADT group compared with 103.0+/-7.42 mg/dL in the non-ADT group (P=0.01) and 99.0+/-7.58 mg/dL in the control group (P<0.01). 2) Insulin levels were 45.0+/-7.25 uU/mL in the ADT group compared with 24.0+/-7.24 uU/mL in the non-ADT group (P=0.05) and 19.0+/-7.39 uU/mL in the control group (P=0.02). 3) Leptin levels were 25.0+/-2.57 ng/mL in the ADT group compared with 12.0+/-2.56 ng/mL in the non-ADT group (P<0.01) and 6.0+/-2.62 ng/mL in the control group (P<0.01). 4) The homeostatic model assessment for insulin resistance (HOMAIR)=17.0+/-2.78 in the ADT group compared with HOMAIR=6.0+/-2.77 in the non-ADT group (P<0.01) and HOMAIR=5.0+/-2.83 in the control group (P=0.01). There was a significant negative correlation between total and free testosterone levels with fasting glucose, insulin, leptin, and HOMAIR.

CONCLUSIONS

The current data suggested that men with PCa who are receiving long-term ADT are at risk for developing insulin resistance and hyperglycemia, thus leading to their increased risk of cardiovascular disease. This adverse metabolic profile developed independent of age and BMI and appeared to be a direct result of androgen deprivation.

Riesgo oncológico de la obesidad

This article presents an update of scientific evidence about the relation of obesity with the incidence or mortality by cancer. Almost all large epidemiological studies agree about the oncological risk of obesity, especially with regard to some types of cancers. Different physiopathological theories to explain this association have been proposed, from simple mechanical or dietetical causes to genetic or immunologic factors, including a possible role of hormones or adipocyte humoral factors. Moreover, obesity can play a role in the prognosis of certain cancers. Prevention of obesity must be included among the strategies to fight cancer.

Association between serum adiponectin, and pathological stage and grade in men undergoing radical prostatectomy

PURPOSE

Adiponectin is a polypeptide hormone produced by adipocytes that has anti-angiogenic properties. Circulating adiponectin is lower in obese men. Obesity has been associated with advanced stage and a higher risk of biochemical progression following radical prostatectomy (RP) in several series. We examined whether serum adiponectin is associated with advanced disease stage at RP.

MATERIALS AND METHODS

Adiponectin was measured by enzyme-linked immunosorbent assay in the preoperative serum of 236 men treated with RP between 1998 and 1999. The odds ratio (OR) of advanced stage (pT3a or greater) and high grade disease (pathological Gleason sum 7 or greater) associated with quartiles of adiponectin were estimated using multivariate logistic regression models.

RESULTS

Serum adiponectin weakly correlated inversely with body mass index (Spearman r = -0.22, p = 0.01). Serum adiponectin was not associated with cancer stage or grade. However, in normal weight men adiponectin was positively associated with high stage disease (OR 1.14, 95% CI 1.02 to 1.29, p = 0.03), although there was no statistically significant association with high grade disease (OR 1.05, 95% CI 0.94 to 1.18, p = 0.38). In overweight and obese men adiponectin was inversely associated with high grade disease (OR 0.94, 95% CI 0.87 to 1.01, p = 0.09), although there was no statistically significant association with high stage disease (OR 0.97, 95% CI 0.91 to 1.04, p = 0.43). Further adjustments for body mass index had little impact on any ORs.

CONCLUSIONS

These data provide evidence to suggest that adiponectin may be related to prostate cancer aggressiveness, although the direction of the associations may depend on the extent of adiposity and on cancer grade.

Lack of correlation between leptin receptor expression and PI3-K/Akt signaling pathway proteins immunostaining in endometrioid-type endometrial carcinomas

A number of studies published recently focused on the putative role of leptin in the pathogenesis of various primary human malignancies. Current study was aimed at investigating ObR, PI3-kinase, phospho-Akt kinase and PTEN proteins expression in forty-five primary human endometrioid-type endometrial carcinomas (EC). ObR immunostaining was detected in 21 of 45 (47%) ECs, presented in almost 60% of well- and moderately-differentiated tumors compared to only 17% of poorly-differentiated neoplasms (P<0.05). Semi-quantitative histological score (H-score) ObR values were inversely correlated with patients' body mass index (R=-0.35; P=0.019). ObR expression was significantly higher in normal weight compared to overweight and obese patients (P=0.024). All slides displayed intense PI3-kinase immunoreactivity, whereas phospho-Akt kinase expression was reported in 96% (43 out of 45) cases. Fifteen (33%) ECs were negative for PTEN expression, nine (20%) showed heterogeneous immunostaining pattern, whereas 21 (47%) were PTEN-positive. There was a trend towards a higher phospho-Akt kinase intensity immunostaining in PTEN-negative compared to PTEN-positive cases, but the difference was not significant. There was no significant association between each PI3-K/Akt signaling pathway proteins immunostaining in endometrioid-type ECs. In conclusion, ObR expression is associated with histological grading and the weight of women affected by EC. The components of PI3-K/Akt kinase signaling pathway are expressed in most of the primary endometrioid-type endometrial neoplasms.

Genetics of leptin and obesity: a HuGE review

Leptin is an important regulator of the mass of adipose tissue and of body weight; it operates by inhibiting food intake and stimulating energy expenditure. Some polymorphic genes involved in the regulation of leptin-the leptin gene (LEP A19G), the leptin receptor gene (LEPR Q223R, K109R, and K656N), and the peroxisome proliferator-activated receptor-gamma gene (PPARG P12A and C161T)--have been investigated as possible factors associated with obesity. Allelic frequencies of these polymorphisms show ethnic variation. The authors performed a meta-analysis of the available data on the association between these polymorphisms and obesity based on case-control studies. Odds ratios and 95% confidence intervals for obesity associated with leptin polymorphisms were calculated by using both fixed- and random-effects models. Results suggest no evidence of association between the genes under study and obesity. The lack of association could be due to the complex pathogenesis of obesity, which involves a number of genetic and environmental factors. Large studies including testing of multiple genes in both obese and lean subjects, with epidemiologic data on dietary habits in different ethnic groups, are necessary to better understand the role of leptin in regulating weight in human populations.

Serum protein markers for early detection of ovarian cancer

Early diagnosis of epithelial ovarian cancer (EOC) would significantly decrease the morbidity and mortality from this disease but is difficult in the absence of physical symptoms. Here, we report a blood test, based on the simultaneous quantization of four analytes (leptin, prolactin, osteopontin, and insulin-like growth factor-II), that can discriminate between disease-free and EOC patients, including patients diagnosed with stage I and II disease, with high efficiency (95%). Microarray analysis was used initially to determine the levels of 169 proteins in serum from 28 healthy women, 18 women newly diagnosed with EOC, and 40 women with recurrent disease. Evaluation of proteins that showed significant differences in expression between controls and cancer patients by ELISA assays yielded the four analytes. These four proteins then were evaluated in a blind cross-validation study by using an additional 106 healthy females and 100 patients with EOC (24 stage I/II and 76 stage III/IV). Upon sample decoding, the results were analyzed by using three different classification algorithms and a binary code methodology. The four-analyte test was further validated in a blind binary code study by using 40 additional serum samples from normal and EOC cancer patients. No single protein could completely distinguish the cancer group from the healthy controls. However, the combination of the four analytes exhibited the following: sensitivity 95%, positive predictive value (PPV) 95%, specificity 95%, and negative predictive value (NPV) 94%, a considerable improvement on current methodology.