Leptin and gastro-intestinal malignancies

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Importance of circulating leptin and adiponectin in the causal pathways between obesity and the development of colorectal cancer in Japanese men

BACKGROUND

The mechanistic associations between obesity and risk of colorectal cancer (CRC) remain unclear. Here, using body mass index (BMI) as an obesity indicator, we decomposed the total effects of obesity on the risk of CRC into: (1) direct effects, which are possibly mediated by unmeasured or currently unknown factors; (2) indirect effects mediated by circulating leptin and adiponectin; and (3) indirect effects that are not mediated by circulating leptin and adiponectin but by hyperinsulinemia and chronic inflammation (assessed via circulating connecting peptide and C-reactive protein, respectively).

METHODS

We adopted a causal mediation framework, using data from a large prospective cohort study of 44,271 Japanese men.

RESULTS

BMI was not associated with the risk of CRC due to direct and indirect effects that were not mediated by circulating leptin and adiponectin. By contrast, individuals with BMIs of 25.0-27.4 kg/m2 (risk ratio, 1.29; 95% confidence interval, 0.98-1.69) and ≥27.5 kg/m2 (risk ratio, 1.28; 95% confidence interval, 0.98-1.68) had a higher risk of CRC due to indirect effects of circulating leptin and adiponectin.

CONCLUSIONS

Our mediation analyses suggest that the association between BMI and CRC risk may be largely mediated by a pathway involving circulating leptin and adiponectin.

Assessment of the Role of Leptin and Adiponectinas Biomarkers in Pancreatic Neuroendocrine Neoplasms

Data on the possible connection between circulating adipokines and PanNENs are limited. This novel study aimed to assess the serum levels of leptin and adiponectin and their ratio in patients with PanNENs and to evaluate the possible relationship between them and PanNEN's grade or stage, including the presence of metastases. The study group consisted of PanNENs (n = 83), and healthy controls (n = 39). Leptin and adiponectin measurement by an ELISA assay was undertaken in the entire cohort. The serum concentration of adiponectin was significantly higher in the control group compared to the study group (p < 0.001). The concentration of leptin and adiponectin was significantly higher in females than in males (p < 0.01). Anincreased leptin-adiponectin ratio was observed in well-differentiated PanNENs (G1) vs. moderatelydifferentiated PanNENs (G2) (p < 0.05). An increased leptin-adiponectin ratio was found in PanNENs with Ki-67 < 3% vs. Ki-67 ≥ 3% (p < 0.05). PanNENs with distal disease presented lower leptin levels (p < 0.001) and a decreased leptin-adiponectin ratio (p < 0.01) compared with the localized disease group. Leptin, adiponectin, and the leptin-adiponectin ratio may serve as potential diagnostic, prognostic, and predictive biomarkers for PanNENs. Leptin levels and the leptin-adiponectin ratio may play an important role as predictors of malignancy and metastasis in PanNENs.

The Rise of Gastrointestinal Cancers as a Global Phenomenon: Unhealthy Behavior or Progress?

The overall burden of cancer is rapidly increasing worldwide, reflecting not only population growth and aging, but also the prevalence and spread of risk factors. Gastrointestinal (GI) cancers, including stomach, liver, esophageal, pancreatic, and colorectal cancers, represent more than a quarter of all cancers. While smoking and alcohol use are the risk factors most commonly associated with cancer development, a growing consensus also includes dietary habits as relevant risk factors for GI cancers. Current evidence suggests that socioeconomic development results in several lifestyle modifications, including shifts in dietary habits from local traditional diets to less-healthy Western diets. Moreover, recent data indicate that increased production and consumption of processed foods underlies the current pandemics of obesity and related metabolic disorders, which are directly or indirectly associated with the emergence of various chronic noncommunicable conditions and GI cancers. However, environmental changes are not restricted to dietary patterns, and unhealthy behavioral features should be analyzed with a holistic view of lifestyle. In this review, we discussed the epidemiological aspects, gut dysbiosis, and cellular and molecular characteristics of GI cancers and explored the impact of unhealthy behaviors, diet, and physical activity on developing GI cancers in the context of progressive societal changes.

Visceral adipose tissue secretome from early and late-stage oesophageal cancer patients differentially affects effector and regulatory T cells

AIM

Visceral obesity is a key risk factor in the development of oesophagogastric junctional adenocarcinoma (OGJ), predominantly via generation of systemic low grade inflammation. Obesity-induced inflammation promotes resistance to current standards of care, enhancing tumour cell growth and survival. This study investigates the effect of the visceral adipose tissue secretome from OGJ patients with early versus advanced tumours on T-cell immunity and the role of immune checkpoint blockade in enhancing anti-tumour immunity.

METHODS AND RESULTS

Visceral adipose conditioned media (ACM) from both early and late-stage OGJ patients significantly altered T cell activation status, upregulating co-stimulatory marker CD27 on T cells. ACM from both early and late-stage OGJ patients significantly altered immune checkpoint expression profiles downregulating immune checkpoints (ICs) on the surface of dual Th1/17-like and Th17-like cells and upregulating ICs on the surface of Th1-like cells and Treg cells. ACM derived from early-stage OGJ patients but not late-stage OGJ patients increased IFN-γ production by T cells. The addition of immune checkpoint blockers (ICBs) did not increase IFN-γ production by T cells in the presence of late-stage ACM, collectively highlighting the dichotomous immunostimulatory effect of early-stage ACM and immune-inhibitory effect of late-stage ACM. Interestingly, ACM from early-stage OGJ patients was more pro-inflammatory than ACM from late-stage patients, reflected by decreased levels of IL-17A/F, TNF-α, IL-1RA and IL-5.

CONCLUSION

The ACM-induced upregulation of ICs on T cells highlights a therapeutic vulnerability that could be exploited by ICBs to harness anti-cancer immunity and improve clinical outcomes for OGJ patients. Schematic workflow - (A) visceral adipose tissue was taken from OAC patients at time of surgery and cultured for 72 h in media. (B) The harvested ACM was co-cultured with healthy donor PBMCs that were concurrently activated with anti-CD3/28 for 48 h and T cell immunophenotyping was carried out by flow cytometry. Key findings - (A) Early and late stage ACM enhanced a Th1-like phenotype and upregulated CTLA-4 on Th1-like cells. A Th17-like phenotype was also enhanced in addition with a Treg-like phenotype. CTLA-4 and PD-L1 were upregulated on the surface of Treg-like cells. (B) ICB-attenuated IL-17 production by T cells. However, ACM attenuated ICB-mediated reduction in IL-10 production by T cells. Higher levels of pro-inflammatory factors were found in early stage ACM compared with late stage ACM.

The underexplored links between cancer and the internal body climate: Implications for cancer prevention and treatment

In order to effectively manage and cure cancer we should move beyond the general view of cancer as a random process of genetic alterations leading to uncontrolled cell proliferation or simply a predictable evolutionary process involving selection for traits that increase cell fitness. In our view, cancer is a systemic disease that involves multiple interactions not only among cells within tumors or between tumors and surrounding tissues but also with the entire organism and its internal "milieu". We define the internal body climate as an emergent property resulting from spatial and temporal interactions among internal components themselves and with the external environment. The body climate itself can either prevent, promote or support cancer initiation and progression (top-down effect; i.e., body climate-induced effects on cancer), as well as be perturbed by cancer (bottom-up effect; i.e., cancer-induced body climate changes) to further favor cancer progression and spread. This positive feedback loop can move the system towards a "cancerized" organism and ultimately results in its demise. In our view, cancer not only affects the entire system; it is a reflection of an imbalance of the entire system. This model provides an integrated framework to study all aspects of cancer as a systemic disease, and also highlights unexplored links that can be altered to both prevent body climate changes that favor cancer initiation, progression and dissemination as well as manipulate or restore the body internal climate to hinder the success of cancer inception, progression and metastasis or improve therapy outcomes. To do so, we need to (i) identify cancer-relevant factors that affect specific climate components, (ii) develop 'body climate biomarkers', (iii) define 'body climate scores', and (iv) develop strategies to prevent climate changes, stop or slow the changes, or even revert the changes (climate restoration).

Blood and Urinary Biomarkers of Antipsychotic-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Antipsychotic (AP)-induced MetS (AIMetS) is the most common adverse drug reaction (ADR) of psychiatric pharmacotherapy. Herein, we review the results of studies of blood (serum and plasma) and urinary biomarkers as predictors of AIMetS in patients with schizophrenia (Sch). We reviewed 1440 studies examining 38 blood and 19 urinary metabolic biomarkers, including urinary indicators involved in the development of AIMetS. Among the results, only positive associations were revealed. However, at present, it should be recognized that there is no consensus on the role of any particular urinary biomarker of AIMetS. Evaluation of urinary biomarkers of the development of MetS and AIMetS, as one of the most common concomitant pathological conditions in the treatment of patients with psychiatric disorders, may provide a key to the development of strategies for personalized prevention and treatment of the condition, which is considered a complication of AP therapy for Sch in clinical practice.

The pleiotropic roles of leptin in metabolism, immunity, and cancer

The discovery of the archetypal adipocytokine leptin and how it regulates energy homeostasis have represented breakthroughs in our understanding of the endocrine function of the adipose tissue and the biological determinants of human obesity. Investigations on leptin have also been instrumental in identifying physio-pathological connections between metabolic regulation and multiple immunological functions. For example, the description of the promoting activities of leptin on inflammation and cell proliferation have recognized the detrimental effects of leptin in connecting dysmetabolic conditions with cancer and with onset and/or progression of autoimmune disease. Here we review the multiple biological functions and complex framework of operations of leptin, discussing why and how the pleiotropic activities of this adipocytokine still pose major hurdles in the development of effective leptin-based therapeutic opportunities for different clinical conditions.

High fat diet, gut microbiome and gastrointestinal cancer

Gastrointestinal cancer is currently one of the main causes of cancer death, with a large number of cases and a wide range of lesioned sites. A high fat diet, as a public health problem, has been shown to be correlated with various digestive system diseases and tumors, and can accelerate the occurrence of cancer due to inflammation and altered metabolism. The gut microbiome has been the focus of research in recent years, and associated with cell damage or tumor immune microenvironment changes via direct or extra-intestinal effects; this may facilitate the occurrence and development of gastrointestinal tumors. Based on research showing that both a high fat diet and gut microbes can promote the occurrence of gastrointestinal tumors, and that a high fat diet imbalances intestinal microbes, we propose that a high fat diet drives gastrointestinal tumors by changing the composition of intestinal microbes.

Leptin and Cancer: Updated Functional Roles in Carcinogenesis, Therapeutic Niches, and Developments

Leptin is an obesity-associated adipokine that is known to regulate energy metabolism and reproduction and to control appetite via the leptin receptor. Recent work has identified specific cell types other than adipocytes that harbor leptin and leptin receptor expression, particularly in cancers and tumor microenvironments, and characterized the role of this signaling axis in cancer progression. Furthermore, the prognostic significance of leptin in various types of cancer and the ability to noninvasively detect leptin levels in serum samples have attracted attention for potential clinical applications. Emerging findings have demonstrated the direct and indirect biological effects of leptin in regulating cancer proliferation, metastasis, angiogenesis and chemoresistance, warranting the exploration of the underlying molecular mechanisms to develop a novel therapeutic strategy. In this review article, we summarize and integrate transcriptome and clinical data from cancer patients together with the recent findings related to the leptin signaling axis in the aforementioned malignant phenotypes. In addition, a comprehensive analysis of leptin and leptin receptor distribution in a pancancer panel and in individual cell types of specific organs at the single-cell level is presented, identifying those sites that are prone to leptin-mediated tumorigenesis. Our results shed light on the role of leptin in cancer and provide guidance and potential directions for further research for scientists in this field.

Leptin Receptor (LEPR) promotes proliferation, migration, and invasion and inhibits apoptosis in hepatocellular carcinoma by regulating ANXA7

Background

Leptin Receptor (LEPR) has been suggested to have several roles in cancer metastasis. However, the role of LEPR and its underlying mechanisms in lymphatic metastasis of hepatocarcinoma have not yet been studied.

Methods

We performed bioinformatics analysis, qRT-PCR, western blotting, immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent, coimmunoprecipitation assays and a series of functional assays to investigate the roles of LEPR in hepatocellular carcinoma.

Results

We discovered that LEPR was highly expressed in liver cancer tissues, and the expression of LEPR in Hca-F cells was higher than that in Hca-P cells. Furthermore, LEPR promotes the proliferation, migration and invasion and inhibits the apoptosis of hepatocarcinoma lymphatic metastatic cells. Further studies indicated that LEPR interacts with ANXA7. Mechanistically, LEPR regulated ERK1/2 and JAK2/STAT3 expression via ANXA7 regulation.

Conclusions

These findings unveiled a previously unappreciated role of LEPR in the regulation of lymphatic metastatic hepatocellular carcinoma, assigning ANXA7-LEPR as a promising therapeutic target for liver cancer treatments.

Leptin Promotes Prostate Cancer Proliferation and Migration by Stimulating STAT3 Pathway

To better understand the link between obesity and prostate cancer (PC) aggressiveness, we investigate the role of leptin, an obesity associated adipokine, and its receptor (Ob-R) in PC cells migration. The migration assay (Wound-healing) was used to study the leptin impact on DU-145 and PC3 cells lines. STAT3 activation was performed by Western Blot. E-cadherin expression was studied using fluorescence microscopy and Ob-R expression in PC and benign prostatic Hyperplasia (BPH) biopsies was assessed by RT-PCR. In this study we demonstrate that high dose of leptin promotes PC cells migration and EMT transition via the stimulation of STAT3 pathway. In addition, we report that although Ob-R mRNA is expressed by ADK and BPH resections biopsies, significant higher levels were observed for ADK patients. Finally, we found a positive association between Ob-R mRNA expression and worse PC prognosis. A better understanding of the molecular processes of leptin signaling is crucial for identifying appropriate approaches for treatment of obesity-related PC patients.

A longitudinal study of prediagnostic metabolic biomarkers and the risk of molecular subtypes of colorectal cancer

Body fatness increases the risk of colorectal cancer (CRC). Insulin resistance and altered adipokines are potential mechanisms, but previous biomarker studies have been inconsistent. Intertumoral heterogeneity might provide an explanation. We investigated insulin, C-peptide, adiponectin, and leptin in relation to CRC molecular subtypes using a nested case-control design (1010 cases, 1010 matched controls, median 12.3 years from baseline to CRC diagnosis) from the population-based Northern Sweden Health and Disease Study. Repeated samples were available from 518 participants. Risks of CRC and subtypes, defined by tumor BRAF and KRAS mutations and microsatellite instability (MSI) status, were estimated using conditional logistic regression and linear mixed models. Higher C-peptide and lower adiponectin were associated with increased CRC risk (odds ratios per standard deviation increase (95% CI): 1.11 (1.01, 1.23) and 0.91 (0.83, 1.00), respectively), though weakened when adjusted for body mass index. Insulin and leptin were not associated with CRC risk. Within-individual time trajectories were similar in cases and controls, and no subtype-specific relationships were identified (all P_{heterogeneity} > 0.1). Adiponectin was weakly inversely associated with the risk of KRAS-mutated (P = 0.08) but not BRAF-mutated or KRAS/BRAF-wildtype CRC, consistent with the one previous study. These findings contribute to an increased understanding of the complex role of body size in CRC.

Circulating obesity-driven biomarkers are associated with risk of clear cell renal cell carcinoma: a two-stage, case-control study

Obesity is one of modifiable risk factors for clear cell renal cell cancer (ccRCC). We aim to identify the association between obesity-driven biomarkers and ccRCC risk. This is a retrospective, two-phase, case-control study involving 682 cases and 733 controls. Obesity-driven biomarkers [gastric inhibitory polypeptide (GIP), C-peptide, insulin, resistin, adipsin, peptide YY, pancreatic polypeptide, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), plasminogen activator inhibitor-1, monocyte chemoattractant protein 1, lipocalin2, leptin, adiponectin] were measured using the Milliplex method. Multivariate logistic regression was used to assess the associations between biomarkers and ccRCC risk. Results revealed that GIP, C-peptide, IL-6 and TNF-α levels were consistently distinct between cases and controls. These markers were significantly associated with ccRCC risk in both phases (except C-peptide). In the combined population, compared with individuals with low levels of the biomarkers, individuals with high level of GIP [odds ratio (OR) = 0.52, 95% confidence interval (CI): 0.40-0.67] had lower risk, whereas individuals with high levels of C-peptide (OR = 1.46, 95% CI: 1.15-1.87), IL-6 (OR = 2.20, 95% CI: 1.50-3.22), TNF-α (OR = 1.90, 95% CI: 1.49-2.43) had significantly higher risk. Stratified analysis showed consistent associations with ccRCC risk in most subgroups (P < 0.05). The risk score based on the IL-6, TNF-α and GIP was positively associated with ccRCC risk in a dose-response manner (P for trend = 2.18E-13). Data from The Cancer Genome Atlas indicate that insulin signaling, IL-6 signaling and TNF-α signaling were enhanced in tumors. Collectively, our study demonstrates the integrative effect of insulin resistance and inflammation in ccRCC development, which may elucidate the basis of association between obesity and carcinogenesis. Further confirmation in prospective cohort studies are warranted for clinical applications in prevention and precision medicine of ccRCC.

Dietary Fat-Accelerating Leptin Signaling Promotes Protumorigenic Gastric Environment in Mice

Excess of fat intake leads to obesity and causes a variety of metabolic diseases and cancer. We previously demonstrated that high-lard diet induces intestinal metaplasia, a precancerous lesion of the stomach mediated by leptin signaling. This study aims to investigate which kinds of dietary fat cause the intestinal metaplasia onset. We fed eight kinds of high-fat diets (HFDs) of animal or plant origin to mice evaluated their effect on gastric pathogenesis. Five types of dietary fat were divided according to their observed effects: Obese with high metaplasia (group I; beef tallow, lard, and hydrogenated coconut oil), non-obese with high metaplasia (group II; linseed oil), obese without metaplasia (group III; corn oil and olive oil), non-obese without metaplasia (group IV, soybean oil) and lean without metaplasia (group V; cocoa butter). The group I and II diets induced leptin, phosphorylated leptin receptor (ObR), signal transducer and activator 3 (STAT3), and increased intracellular β-catenin accumulation in the stomach. Moreover, mice fed these HFDs with 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), a gastric carcinogen, and further accelerated dysplasia in the stomach. Lactobacillus occupancy in the stomach increased in all HFDs except hydrogenated coconut oil. Our findings suggest that HFDs inducing leptin signaling accelerate the enhancement of protumorigenic gastric microenvironment independent of body mass gain or microbiome changes.

High-fat-diet-induced modulations of leptin signaling and gastric microbiota drive precancerous lesions in the stomach

OBJECTIVES

Obesity is a risk factor for malignancy in various tissues, and has been associated with gut microbiota alterations. However, the link between obesity-associated microbiota and gastric pathogenesis has not been clarified. We demonstrated that high-fat-diet (HFD) feeding causes intestinal metaplasia, which are precancerous lesions of the stomach, with augmented gastric leptin signaling. The aim of this study was to investigate the precise role of leptin signaling in the altered microbiota composition and pathogenesis in the stomach during diet-induced obesity.

METHODS

Male C57 BL/6 J, leptin receptor (Lepr)-mutated db/db, and gastrointestinal epithelium-specific Lepr conditional knockout (T3 b-Lepr cKO) mice were fed a HFD or control diet. Gastrointestinal microbiota was analyzed by 16 S rRNA gene sequences and quantitative polymerase chain reaction. Transplantation of gastric microbiota of HFD-fed mice was performed to evaluate metaplasia onset in recipient mice.

RESULTS

One week of HFD caused severe microbial dysbiosis in the stomach. The microbiota changes were accompanied by increased gastric leptin, leading to the consequent development of intestinal metaplasia. Transplantation of gastric microbiota from HFD-fed mice induced intestinal metaplasia in recipient mice; however, only a limited effect on pathogenesis was noted. HFD-fed db/db mice did not show a decrease in microbial abundance. Moreover, T3 b-Lepr cKO mice failed spontaneous obesity, and suppressed decreased abundance of gastric microbiota and occurrence of intestinal metaplasia during HFD feeding similar to db/db mice.

CONCLUSIONS

Gastric leptin signaling modulates the gastric microbiota community and regulates the pathogenesis in the gastric mucosa.

How the association between obesity and inflammation may lead to insulin resistance and cancer

BACKGROUND AND OBJECTIVES

Obesity is associated with metabolic dysfunction and over nutrition. Increased body mass index and obesity are strongly amalgamated with changes in the physiological function of adipose tissue, leading to altered secretion of adipocytokines, inflammatory mediators release as well as chronic inflammation and insulin resistance. The purposes of this study were to review the evidence of how obesity and inflammation may lead to insulin resistance and cancer.

SUMMARY

Recent findings suggested that increased level of inflammatory mediators in obesity, plays an introductory and cabalistic role in the development of different types of inflammatory disorders including type 2 diabetes mellitus. Link between elevated body mass index and type 2 diabetes mellitus (T2DM). Several of the factors-such as increased levels of leptin, plasminogen activator inhibitor-1, decreased levels of adiponectin, insulin resistance, chronic inflammation etc. consequently result in carcinogenesis and carcinogenic progression too.

CONCLUSION

This review summarizes how cytokine production in adipose tissue of obese subject creates a chronic inflammatory environment that favors tumor cell motility and invasion to enhance the metastatic potential of tumor cells. High levels of cytokine in the circulation of affected individuals have been associated with a significantly worse outcome. This article also reconnoiters the mechanisms that link obesity to numerous disorders such as inflammation, diabetes, cancers and most specifically combine these processes in a single image. Understanding these mechanisms may assist to understand the consequences of obesity.

Bone Marrow Adipocyte: An Intimate Partner With Tumor Cells in Bone Metastasis

The high incidences of bone metastasis in patients with breast cancer, prostate cancer and lung cancer still remains a puzzling issue. The "seeds and soil" hypothesis suggested that bone marrow (soil) may provide a favorable "niche" for tumor cells (seed). When seeking for effective ways to prevent and treat tumor bone metastasis, most researchers focus on tumor cells (seed) but not the bone marrow microenvironment (soil). In reality, only a fraction of circulating tumor cells (CTCs) could survive and colonize in bone. Thus, the bone marrow microenvironment could ultimately determine the fate of tumor cells that have migrated to bone. Bone marrow adipocytes (BMAs) are abundant in the bone marrow microenvironment. Mounting evidence suggests that BMAs may play a dominant role in bone metastasis. BMAs could directly provide energy for tumor cells, enhance the tumor cell proliferation, and resistance to chemotherapy and radiotherapy. BMAs are also known for releasing some inflammatory factors and adipocytokines to promote or inhibit bone metastasis. In this review, we made a comprehensive summary for the interaction between BMAs and bone metastasis. More importantly, we discussed the potentially promising methods for the prevention and treatment of bone metastasis. Genetic disruption and pharmaceutical inhibition may be effective in inhibiting the formation and pro-tumor functions of BMAs.

High-fat diet feeding promotes stemness and precancerous changes in murine gastric mucosa mediated by leptin receptor signaling pathway

Obesity increases the risk for gastric cancers. However, the occurrence and mechanisms of precancerous atrophic gastritis induced by high-fat diet (HFD) remain unclear. Here, we show that HFD-associated lipotoxicity induces precancerous lesions that are accompanied by the disruption of organelle homeostasis, tissue integrity, and deregulated expression of stemness genes in the gastric epithelium mediated by leptin receptor (ObR) signaling. Following HFD feeding, ectopic fat accumulated and expression of LAMP2A in lysosome and COX IV in mitochondria increased in the gastric mucosa. HFD feeding also led to enhanced expression of activated-Notch1 and stem cell markers Lgr5, CD44, and EpCAM. In addition, HFD-fed mice showed intracellular β-catenin accumulation in the gastric mucosa with increased expression of its target genes, Nanog, Oct4, and c-Myc. These observations were abrogated in the leptin-deficient ob/ob mice and ObR-mutated db/db mice, indicating that these HFD-induced changes were responsible for effects downstream of the ObR. Consistent with this, the expression of the Class IA and III PI3Ks was increased following ObR activation in the gastric mucosa of HFD-fed mice. Together, these results suggest that HFD-induced lipotoxicity and deregulated organelle biosynthesis confer cancer stem cell-like properties to the gastric mucosa via signaling pathway mediated by leptin, PI3K and β-catenin.

Interaction between Esophageal Squamous Cell Carcinoma and Adipose Tissue in Vitro

Esophageal squamous cell carcinoma (ESCC) develops within the squamous epithelial layer and invades the submucosa to the subadventitia that has adipose tissue (AT). AT seems critical to ESCC progression, but the underlying mechanism is unknown. We aimed to address the association between ESCC and AT in vitro. ESCC cells were cultured on rat or human subcutaneous AT-embedded or -non-embedded collagen gel. AT promoted the growth of ESCC cells and inhibited their apoptosis. AT promoted the expression of the squamous differentiation marker involucrin in ESCC cells. AT accelerated the expression of invasion-related factors in poorly differentiated ESCC cells only. AT promoted the expression of phosphorylated-insulin-like growth factor-1 receptor in ESCC cells, whereas it inhibited that of the human epidermal growth factor receptor 2. Insulin-like growth factor-1, but not leptin, adiponectin, or resistin, promoted and inhibited the growth and apoptosis of ESCC cells, respectively. In turn, ESCC cells decreased the production of these adipokines in AT and the number of preadipocytes and mesenchymal stem cell-like cells, which developed from AT. These results suggest that i) AT may influence the progression of ESCC with increased growth or invasion and decreased apoptosis through insulin-like growth factor-1/insulin-like growth factor-1 receptor signaling, ii) AT may affect human epidermal growth factor receptor 2-targeted therapy; and iii) the cancer cells may affect adipokine production in AT.

Esophageal adenocarcinoma and obesity: peritumoral adipose tissue plays a role in lymph node invasion

Obesity is associated with cancer risk in esophageal adenocarcinoma (EAC). Adipose tissue directly stimulates tumor progression independently from body mass index (BMI), but the mechanisms are not fully understood. We studied the morphological, histological and molecular characteristics of peritumoral and distal adipose tissue of 60 patients with EAC, to investigate whether depot-specific differences affect tumor behavior. We observed that increased adipocyte size (a hallmark of obesity) was directly associated with leptin expression, angiogenesis (CD31) and lymphangiogenesis (podoplanin); however, these parameters were associated with nodal metastasis only in peritumoral but not distal adipose tissue of patients. We treated OE33 cells with conditioned media (CM) collected from cultured biopsies of adipose tissue and we observed increased mRNA levels of leptin and adiponectin receptors, as well as two key regulator genes of epithelial-to-mesenchymal transition (EMT): alpha-smooth muscle actin (α-SMA) and E-cadherin. This effect was greater in cells treated with CM from peritumoral adipose tissue of patients with nodal metastasis and was partially blunted by a leptin antagonist. Therefore, peritumoral adipose tissue may exert a direct effect on the progression of EAC by secreting depot-specific paracrine factors, and leptin is a key player in this crosstalk.

Leptin receptor signaling is required for high-fat diet-induced atrophic gastritis in mice

Background

Obesity increases the risk for malignancies in various tissues including the stomach. Atrophic gastritis with precancerous lesions is an obesity-associated disease; however, the mechanisms that underlie the development of obesity-associated atrophic gastritis are unknown. Leptin is a hormone derived from stomach as well as adipose tissue and gastric leptin is involved in the development of gastric cancer. The aim of the current study is to investigate the involvement of leptin receptor signaling in the development of atrophic gastritis during diet-induced obesity.

Methods

Male C57BL/6, ob/ob and db/db mice were fed a high-fat diet (HFD) or a control diet (CD) from 1 week to 5 months. Pathological changes of the gastric mucosa and the expression of molecules associated with atrophic gastritis were evaluated in these mice.

Results

HFD feeding induced gastric mucosal hyperplasia with increased gastric leptin expression. Mucosal hyperplasia was accompanied by a higher frequency of Ki67-positive proliferating cells and atrophy of the gastric glands in the presence of inflammation, which increased following HFD feeding. Activation of ObR signaling-associated molecules such as ObR, STAT3, Akt, and ERK was detected in the gastric mucosa of mice fed the HFD for 1 week. The morphological alterations associated with gastric mucosal atrophy and the expression of Muc2 and Cdx2 resemble those associated with human intestinal metaplasia. In contrast to wild-type mice, leptin-deficient ob/ob mice and leptin receptor-mutated db/db mice did not show increased Cdx2 expression in response to HFD feeding.

Conclusion

Together, these results suggest that activation of the leptin signaling pathway in the stomach is required to develop obesity-associated atrophic gastritis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0066-1) contains supplementary material, which is available to authorized users.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

The feasibility of an exercise intervention in males at risk of oesophageal adenocarcinoma: a randomized controlled trial

Objective

To investigate the feasibility and safety of a 24-week exercise intervention, compared to control, in males with Barrett’s oesophagus, and to estimate the effect of the intervention, compared to control, on risk factors associated with oesophageal adenocarcinoma development.

Methods

A randomized controlled trial of an exercise intervention (60 minutes moderate-intensity aerobic and resistance exercise five days/week over 24 weeks; one supervised and four unsupervised sessions) versus attention control (45 minutes stretching five days/week over 24 weeks; one supervised and four unsupervised sessions) in inactive, overweight/obese (25.0–34.9 kg/m²) males with Barrett’s oesophagus, aged 18–70 years. Primary outcomes were obesity-associated hormones relevant to oesophageal adenocarcinoma risk (circulating concentrations of leptin, adiponectin, interleukin-6, tumour necrosis factor-alpha, C-reactive protein, and insulin resistance [HOMA]). Secondary outcomes included waist circumference, body composition, fitness, strength and gastro-oesophageal reflux symptoms. Outcomes were measured at baseline and 24-weeks. Intervention effects were analysed using generalised linear models, adjusting for baseline value.

Results

Recruitment was difficult in this population with a total of 33 participants recruited (target sample size: n = 80); 97% retention at 24-weeks. Adherence to the exercise protocol was moderate. No serious adverse events were reported. A statistically significant intervention effect (exercise minus control) was observed for waist circumference (-4.5 [95% CI -7.5, -1.4] cm; p < 0.01). Effects on primary outcomes were not statistically significant.

Conclusion

This small, exploratory trial provides important information to inform future trial development including recruitment rates and estimates of effect sizes on outcomes related to oesophageal adenocarcinoma risk. Future trials should investigate a combined dietary and exercise intervention to achieve greater weight loss in this population and relax inclusion criteria to maximize recruitment.

Trial Registration

Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12609000401257

Could signal transducer and activator of transcription 3 be a therapeutic target in obesity-related gastrointestinal malignancy?

INTRODUCTION

A large body of evidence has implicated the signal transducer and activator of transcription (STAT) family and particularly the ubiquitously expressed STAT3 protein in the pathogenesis of colorectal, hepatocellular, gastric and pancreatic carcinoma.

DISCUSSION

Concomitantly, an increasing body of epidemiological evidence has linked obesity and its associated pro-inflammatory state with the development of gastrointestinal cancers. Visceral adipose tissue is no longer considered inert and is known to secrete a number of adipocytokines such as leptin, interleukin (IL)-6, IL-8, IL-1β and tumour necrosis factor-alpha (TNF-α) into the surrounding environment. Interestingly, these adipocytokines are strongly linked with the Janus kinase (JAK)/STAT pathway of signal transduction and there is experimental evidence linking IL-1β, IL-8 and TNF-α to JAK/STAT signaling in other tissues. The result is an up-regulation of a wide range of anti-apoptotic, pro-metastatic and pro-angiogenic genes and processes. This is particularly relevant for gastrointestinal malignancy as these factors have the potential to signal adjacent endothelial cells in a paracrine manner.

CONCLUSION

This review examines the potential role of the STAT3 signaling pathway in the pathogenesis of obesity-related gastrointestinal malignancy and the potential therapeutic role of STAT3 blockade given its status as a signaling hub for a number of inflammatory adipocytokines.

The role of inflammation in cancer of the esophagus

Esophageal adenocarcinoma is the eighth most common malignancy worldwide. The overall prognosis is poor, with 5-year survival ranges of approximately 15-25%, and 30-50% for patients who can be treated with curative intent. There has been a marked increase in incidence of esophageal adenocarcinoma over the last 30 years, with chronic and severe reflux, diet and obesity identified as principal factors fuelling this rise in the West. Esophageal adenocarcinoma is an exemplar model of an inflammation-associated cancer. The key molecular pathways driving tumor development and influencing tumor biology are the subject of considerable research efforts, and is the principal focus of this review. In addition, the diverse range of changes occurring in the local immune response, tissue microenvironment, metabolic profile, intracellular signaling mechanisms and microRNA signatures are discussed, as well as novel targeted therapies.

Association between chemotherapy and plasma adipokines in patients with colorectal cancer

BACKGROUND

A link between chemotherapy, the serum level of selected adipokines and clinical outcome in colorectal patients was investigated.

METHODS

Leptin, adiponectin, resistin, visfatin and insulin were measured by ELISA in colorectal cancer patients before and 3 months after the administration of cancer therapy. From August 2012 to August 2013, 34 patients with pathologically documented advanced colorectal cancer (T3/T4 with metastases or nodal status up to N3) and measurable metastatic disease, who required palliative chemotherapy based on the combination of 5-fluorouracil, oxaliplatin and irinotecan, were prospectively recruited in this study. Patients previously underwent curative surgical tumour resection, but the disease was disseminated (metastases in the liver and/or lungs) at the time of admission to the hospital.

RESULTS

Of the 34 patients in this study, 5 accomplished a chemotherapy course with partial response (PR), 23 with SD (stabilisation) and 6 with progression (PD). For further study, only patients with good prognostic outcomes (i.e., PR and SD patients) were included. The mean level of leptin before chemotherapy was 26.39 ± 9.53 ng/ml. After six courses of cancer treatment, the leptin level increased by 118-57.44 ± 27.72 ng/ml (p<0.001). Additionally, the adiponectin level increased considerably (47%) from 9.89 ± 3.96 ng/ml to 14.51 ± 7.79 ng/ml (p<0.001). In contrast to leptin and adiponectin, the resistin and visfatin levels decreased significantly from 7.24 ± 1.17 and 1.98 ± 0.44 to 6.36 ± 1.36 and 1.48 ± 0.34 ng/ml (p<0.001), respectively. Insulin also declined remarkably from 16.20 ± 1.96 to 12.87 ± 1.80 (p<0.001). There were no significant differences the between male and female patients regarding age, BMI, and leptin, adiponectin, resistin, visfatin and insulin serum levels.

CONCLUSIONS

The results of the present study are relevant because we found that chemotherapy in colorectal cancer patients, in addition to its beneficial clinical impact on the course of disease, positively affects cytokine production and release (increases the anti-inflammatory adiponectin and decreases visfatin and resistin, which are proangiogenic and promote cancer cell proliferation). The restoration of adequate adipose tissue function is essential for patients to achieve a good survival prognosis.

Leptin and adiponectin receptor expression in oesophageal cancer

BACKGROUND

Oesophageal adenocarcinoma is an exemplar model of an obesity-associated adenocarcinoma. Altered secretion of adipokines by visceral fat is believed to play a key role in tumorigenesis. This study examined leptin receptor (ObR) and adiponectin receptor (AdipoR1 and AdipoR2) expression in oesophageal cancer, and its relationship with patient obesity status, clinicopathological data and patient survival.

METHODS

Tissue microarrays were constructed from paraffin-embedded oesophagectomy specimens. ObR, AdipoR1 and AdipoR2 expression was quantified by immunohistochemistry. Anthropometric data were measured at the time of diagnosis, and obesity status was assessed using visceral fat area determined by computed tomography and body mass index. Receptor expression was correlated with various clinicopathological and anthropometric variables. Patient survival was estimated using the Kaplan-Meier method, and results compared between those with low versus high receptor expression. A Cox multivariable regression model was used to assess the relationship between survival and a number of co-variables.

RESULTS

All 125 tumours analysed expressed AdipoR1 and AdipoR2, whereas 96·8 per cent expressed ObR. There was no significant difference in tumour pathological features or patient obesity status between tumours with low versus high ObR expression. A high level of AdipoR1 expression was significantly associated with increased patient age, obesity and less advanced tumour (T) category. Expression of AdipoR2 was inversely associated with T category (P = 0.043). Low AdipoR1 expression was an independent predictor of improved overall survival (hazard ratio 0.56, 95 per cent confidence interval 0.35 to 0.90; P = 0.017).

CONCLUSION

The association between adiponectin receptor expression, obesity status and tumour category and survival suggests a potential mechanism linking obesity and oesophageal cancer.

Leptin-mediated regulation of ICAM-1 is Rho/ROCK dependent and enhances gastric cancer cell migration

Background:

Our previous study indicates that leptin enhances gastric cancer (GC) invasion. However, the exact effect of leptin on GC metastasis and its underlying mechanism remain unclear. Intercellular adhesion molecule-1 (ICAM-1), a major molecule in stabilising cell–cell and cell–extracellular matrix interactions, is overexpressed and has crucial roles in tumour metastasis.

Methods:

Here, we investigated leptin and ICAM-1 expression in GC tissues. Furthermore, we characterised the influence of leptin on ICAM-1 expression in GC cells and elucidated the underlying mechanism.

Results:

Leptin and ICAM-1 were overexpressed in GC tissues, and a strong positive correlation was observed. They were also related with clinical stage or lymph node metastasis. Furthermore, leptin induced GC cell (AGS and MKN-45) migration by upregulating ICAM-1, and knockdown of ICAM-1 by small interference RNA (siRNA) blocked this process. Cell surface ICAM-1, as well as soluble ICAM-1 (sICAM-1), was also enhanced by leptin. Moreover, leptin increased ICAM-1 expression through Rho/ROCK pathway, which was attenuated by pharmacological inhibition of Rho (C3 transferase) or its downstream effector kinase Rho-associated protein kinase (ROCK) (Y-27632).

Conclusions:

Our findings indicate that leptin enhances GC cell migration by increasing ICAM-1 through Rho/ROCK pathway, which might provide new insight into the significance of leptin in GC.

Mechanisms linking excess adiposity and carcinogenesis promotion

Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases.

Multifaceted roles of adiponectin in cancer

Obesity is linked to increased cancer risk. Pathological expansion of adipose tissue impacts adipocyte function and secretion of hormonal factors regulating tissue homeostasis and metabolism. Adiponectin is an adipocyte-secreted, circulating hormone with pleiotropic functions in lipid and glucose metabolism, and beneficial roles in cardiovascular functions and inflammation. In obesity, decreased Adiponectin plasma levels correlate with tumor development and progression. The association of Adiponectin with potential tumor-limiting functions has raised significant interest in exploring this adipokine as a target for cancer-diagnostic and therapeutic applications. Recent studies, however, also implicate Adiponectin in supporting malignancy. This review highlights the evidence that links Adiponectin signaling to either cancer-protective or cancer-supporting functions. In this context, we discuss Adiponectin interactions with its receptors and associated signaling pathways. Despite significant advances in understanding Adiponectin functions and signaling mechanisms, its role in cancer remains multifaceted and subject to controversy.

Circulating leptin levels and risk of colorectal cancer and adenoma: a case-control study and meta-analysis

PURPOSE

Equivocal results regarding the role of leptin in colorectal cancer (CRC) and adenoma (CRA) have been reported. A case-control study investigating the association of leptin with CRC risk and clinicopathological characteristics along with meta-analysis of published data on both CRC and CRA were conducted.

METHODS

Pubmed and Embase were searched for the meta-analysis, comprising 28 case-control studies amounting 3,614 CRC and 1,215 CRA cases, along with 5,220 controls. Meticulous contact with the authors of individual studies was undertaken for the provision of additional data. Pooling of standardized mean differences (SMD), relative risks (RR) and 95 % CI (random effects models), subgroup, sensitivity, and meta-regression analyses were conducted.

RESULTS

The meta-analysis suggested positive association of serum leptin with CRA (RR, 95 % CI 1.35, 1.03 to +1.76), but not CRC either at the pooled analysis on SMDs or RRs (SMD, 95 % CI 0.18, -0.04 to +0.40; RR, 95 % CI 1.04, 0.65 to +1.65). Significant heterogeneity between studies on CRC as well as between studies on CRA providing SMD was noted. Subgroup, meta-regression and sensitivity analyses highlighted potential methodology-, design-, size- and quality-related effect modifiers.

CONCLUSIONS

Meta-analysis of current evidence suggests positive association of serum leptin with CRA but not with CRC risk. Given the case-control nature of available studies, the limited number of studies on serum leptin and CRA, and the heterogeneity of CRC studies, carefully designed, prospective studies preferably reporting RRs adjusted for a variety of confounders may be warranted.

The role of chronic inflammation in obesity-associated cancers

There is a strong relationship between metabolism and immunity, which can become deleterious under conditions of metabolic stress. Obesity, considered a chronic inflammatory disease, is one example of this link. Chronic inflammation is increasingly being recognized as an etiology in several cancers, particularly those of epithelial origin, and therefore a potential link between obesity and cancer. In this review, the connection between the different factors that can lead to the chronic inflammatory state in the obese individual, as well as their effect in tumorigenesis, is addressed. Furthermore, the association between obesity, inflammation, and esophageal, liver, colon, postmenopausal breast, and endometrial cancers is discussed.

Leptin, resistin and visfatin: the missing link between endocrine metabolic disorders and immunity

Adipose tissue is still regarded as a principle site for lipid storage and mobilizing tissue with an important role in the control of energy homeostasis. Additionally, adipose tissue-secreted hormones such as leptin, visfatin, resistin, apelin, omentin, sex steroids, and various growth factors are now regarded as a functional part of the endocrine system. These hormones also play an important role in the immune system. Several in vitro and in vivo studies have suggested the complex role of adipocyte-derived hormones in immune system and inflammation. Adipokines mediate beneficial and detrimental effects in immunity and inflammation. Many of these adipocytokines have a physiological role in metabolism. The uncontrolled secretions of several adipocytokines were associated with the stimulation of inflammatory processes leading to metabolic disorders including obesity, atherosclerosis, insulin resistance and type 2 diabetes. Obesity leads to the dysfunction of adipocytes andcorrelated with the imbalance of adipokines levels. In obese and diabetic conditions, leptin deficiency inhibited the Jak/Stat3/PI3K and insulin pathways. In this review, ample evidence exists to support the recognition of the adipocyte’s role in various tissues and pathologies. New integral insights may add dimensions to translate any potential agents into the future clinical armamentarium of chronic endocrine metabolic and inflammatory diseases. Functional balance of both adipocytes and immune cells is important to exert their effects on endocrine metabolic disorders; furthermore, adipose tissue should be renamed not only as a functional part of the endocrine system but also as a new part of the immune system.

Mechanisms linking obesity and cancer

The incidence of obesity in US adults has been steadily increasing over the past few decades. Many comorbidities associated with obesity have been well-established such as type 2 diabetes and cardiovascular diseases. However, more recently an epidemiological relationship between obesity and the prevalence of a variety of cancers has also been uncovered. The shift of the paradigm surrounding white adipose tissue function from purely an energy storage tissue, to one that has both endocrine and metabolic relevance, has led to several mechanisms implicated in how obesity drives cancer prevalence and cancer deaths. Currently, there are four categories into which these mechanisms fall - increased lipids and lipid signaling, inflammatory responses, insulin resistance, and adipokines. In this review, we examine each of these categories and the mechanisms through which they drive cancer pathogenesis. Understanding the relationship(s) between obesity and cancer and especially the nodal points of control in these cascades will be essential in developing effective therapeutics or interventions for combating this deadly combination. This article is part of a Special Issue entitled Lipid Metabolism in Cancer.

Elevated plasma level of visfatin/pre-b cell colony-enhancing factor in male oral squamous cell carcinoma patients

Objectives: Visfatin, also known as nicotiamide phosphoribosyltransferase or pre-B cell colony enhancing factor, is a pro-inflammatory cytokine whose serum level is increased in various cancers. In this study, we investigated whether plasma visfatin levels were altered in patients with oral squamous cell carcinoma (OSCC). The relationship between plasma visfatin levels and the pretreatment hematologic profile was also explored. Study Design: Plasma visfatin concentrations were measured through ELISA in OSCC patients and control subjects. A total of 51 patients with OSCC and 57 age- and body mass index (BMI)-matched control subjects were studied. All study subjects were male. Results: Plasma visfatin was found to be elevated in patients with OSCC (7.0 ± 4.5 vs. 4.8 ± 1.9 ng/ml, p = 0.002). Multiple logistic regression analysis revealed visfatin as an independent association factor for OSCC, even after full adjustment of known biomarkers. Visfatin level was significantly correlated with white blood cell (WBC) count, neutrophil count, and hematocrit (all p < 0.05). In addition, WBC count, neutrophil count, and visfatin gradually increased with stage progression, and hematocrit gradually decreased with stage progression (all p < 0.05). Conclusion: Increased plasma visfatin levels were associated with OSCC, independent of risk factors, and were correlated with inflammatory biomarkers. These data suggest that visfatin may act through inflammatory reactions to play an important role in the pathogenesis of OSCC.

Key words:Visfatin; oral squamous cell carcinomas; white blood cell count; neutrophil count.

Leptin-mediated regulation of MT1-MMP localization is KIF1B dependent and enhances gastric cancer cell invasion

Leptin overexpression is closely correlated with gastric cancer (GC) invasion, but its exact effect and the underlying mechanism in tumorigenesis remain poorly understood. Membrane type 1-matrix metalloproteinase (MT1-MMP), a surface-anchored 'master switch' proteinase, is overexpressed and plays crucial roles in tumor invasion. Here, we characterized the influence of leptin on the generation and surface localization of MT1-MMP in GC and elucidated its molecular mechanisms. Our results revealed that leptin promoted GC cell invasion in vitro by upregulating MT1-MMP expression. Furthermore, cell surface biotinylation assay and flow cytometry demonstrated that the surface expression of MT1-MMP was also enhanced by leptin, and knockdown of kinesin family member 1B (KIF1B, a microtubule plus end-directed monomeric motor protein) by small interference RNA inhibited this process. Notably, coimmunoprecipitation analysis indicated that leptin enhanced the interaction of MT1-MMP with KIF1B in a time-dependent manner, which consequently contributed to GC cell invasion. Moreover, leptin increased MT1-MMP or KIF1B expression by the protein kinase B (AKT) pathway and extracellular signal-regulated kinase 1/2 partially participated in this process. However, only AKT was implicated in the leptin-mediated membrane localization of MT1-MMP. Immunohistochemistry analysis revealed that leptin, MT1-MMP and KIF1B are overexpressed in GC tissues, and they positively correlated with clinical stage and lymph node metastasis. These observations indicate that this regulatory network exists in vivo. Taken together, our findings suggest that leptin is an effective intracellular stimulator of MT1-MMP and that leptin-enhanced cell surface localization of MT1-MMP is dependent on KIF1B, which consequently plays a critical role in GC invasion.

Adipocytes: impact on tumor growth and potential sites for therapeutic intervention

The prevalence of obesity has increased dramatically in recent decades, reaching epidemic proportions. It is becoming clear that obesity is associated not only with type 2 diabetes mellitus and cardiovascular disease, but also with multiple types of cancer. Obesity is characterized by impaired adipose tissue function, leading to adipocyte hypertrophy, inflammation, hypoxia and induced angiogenesis, extracellular matrix remodeling and fibrosis as well as additional stress responses. While epidemiological data indicate that obesity is a well-established risk factor for certain malignancies, the molecular mechanisms underlying the link between obesity and cancer are still poorly understood. Recent data implicates systemic and paracrine factors secreted from adipose tissue during the obese state, promoting cancer development and progression. Here, we focus on the obesity-associated adipose tissue remodeling that may not only lead to metabolic complications, but also to a permissive pro-tumorigenic environment. Particular attention is given to the local pro-tumorigenic effects derived from adipocytes that present an important part of the tumor microenvironment of at least some cancers, in an attempt to describe the nature of the major players of the adipocyte-cancer cell crosstalk that dictates to a large extent tumor progression.

Overexpression of methionine adenosyltransferase II alpha (MAT2A) in gastric cancer and induction of cell cycle arrest and apoptosis in SGC-7901 cells by shRNA-mediated silencing of MAT2A gene

The aim of this study was to clarify the methionine adenosyltransferase II alpha (MAT2A) expression pattern and to explore its potential role in gastric cancer. Quantitative real-time PCR was performed to examine MAT2A mRNA expression in 20 cases of gastric cancer tissues and corresponding non-tumor tissue samples. Immunohistochemistry was conducted to detect MAT2A protein expression in 91 gastric cancer tissues. Moreover, the stable cell lines transfected with the small hairpin RNA (shRNA) targeting MAT2A mRNA plasmids were established and the biological characteristics of these cells were examined. The expression levels of MAT2A mRNA in gastric cancer tissues were significantly higher than those in corresponding non-tumor tissues. High-level MAT2A expression was observed in 40.7% (37 of 91 cases), and correlated with tumor classification (P=0.012), lymph node metastasis (P=0.001) and poor tumor differentiation (P=0.011) of gastric cancer patients. Additionally, the MAT2A expression level was significantly decreased in the transfected cells with MAT2A specific shRNA expression plasmid pGCsi-H1-792. The stable transfected cancer cells exhibited a decrease in growth ability and an increase in the incidence of spontaneous apoptosis and the percentage of the G1 phase. Our data suggest that MAT2A plays an important role in gastric cancer development and progression.

Gastric cancer after laparoscopic adjustable gastric banding: case report

Gastric cancer in patients who have undergone bariatric surgery is rare. The authors present a case of stomach cancer in a patient 6 years after adjustable silicone gastric band placement. The tumour was located below the band, not in its direct vicinity. Aetiological and risk factors of stomach cancer incidence in obese patients are discussed in this case study.

Curcumin molecular targets in obesity and obesity-related cancers

Obesity is characterized as an increased BMI, which is associated with the increased risk of several common cancers, including colorectal, breast, endometrial, renal, esophageal, gallbladder, melanoma, multiple myeloma, leukemia, lymphoma and prostate cancer. The increased risk of obesity-related cancers could be mediated by insulin resistance, adipokines, obesity-related inflammatory cytokines, sex hormones, transcription factors and oxidative stress, which disrupt the balance between cell proliferation and apoptosis. The yellowish compound, curcumin (diferuloylmethane), is known to possess multifaceted pharmacological effects. The molecular mechanisms linking obesity to cancer risk, and how curcumin mediates anticancer and obesity activities, have not yet been publicized. Curcumin modulates multiple molecular targets and reverses insulin resistance as well as other symptoms that are associated with obesity-related cancers. In this study, we show that ample evidence exists to support recommendations that curcumin mediates multiple molecular pathways, and is considered to be of therapeutic value in the treatment and prevention of obesity-related cancers.

Metabolic syndrome and leptin are associated with adverse pathological features in male colorectal cancer patients

AIM

Metabolic syndrome (MetS) describes a clustering of factors including central obesity, hypertension and raised plasma glucose, triglycerides and high-density lipoprotein (HDL) cholesterol. Central obesity is associated with a risk for colorectal cancer, but the impact of MetS on colorectal cancer biology and outcomes is unclear.

METHOD

A prospective observational study of colorectal cancer patients was carried out in an Irish population. Patients underwent metabolic and anthropometric assessment before treatment, including measurement of serum hormones and adipokines and CT measurement of visceral fat. MetS was defined according to the International Diabetes Federation definition(3) .

RESULTS

One-hundred and thirty consecutive colorectal cancer patients (66 men and 64 women) were recruited. MetS was diagnosed in 38% patients compared with the population norms reported at 21%(21) . Male patients had a significantly greater visceral fat area compared with female patients. MetS was associated with node-positive disease (P = 0.026), percentage nodal involvement (P = 0.033) and extramural vascular invasion (P = 0.049) in male patients but no significant association was observed in female patients. HDL cholesterol was also significantly associated with a more advanced pathological stage (P = 0.014) and node-positive disease (P = 0.028). Leptin was associated with nodal status (P = 0.036), microvascular invasion (P = 0.054), advanced pathological stage (P = 0.046) and more advanced Dukes stage (P = 0.042).

CONCLUSION

We report a high prevalence of MetS and visceral obesity in a colorectal cancer population. MetS and plasma leptin are associated with a more aggressive tumour phenotype in male patients only.

Multiple signal pathways in obesity-associated cancer

Obesity is increasing worldwide and reaches to a large proportion of the population in developed countries. Thus, obesity-associated cancer has become a major health problem. Multiple cancer risk factors in obesity have been identified including insulin/insulin-like growth factor axis, adipokines and cytokines; and multiple intracellular signal pathways have been studied. However, the role of each signal pathway in obesity-associated cancer is controversial. In this review, the recent studies on signal pathways in obesity-associated cancer are summarized and a unified explanation is provided. Multiple risk factors could initially activate phosphoinositide 3-kinase (PI3K/Akt), mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3) pathways. With increased severity of obesity, mammalian target of rapamycin (mTOR), which is down-stream of both PI3K/Akt and MAPK, is highly activated. Activated mTOR in turn inhibits the PI3K/Akt pathway and further activates the STAT3 pathway. This may explain the activation of the PI3K/Akt pathway at the early stage of obesity and its inhibition at the later stage. mTOR inhibition may be used for cancer therapy, but it may be necessary to be combined with the PI3K/Akt inhibitor as decreased mTOR activity will release its feedback inhibition on the PI3K/Akt pathway, which is under the influence of multiple cancer risk factors in obesity. Thus, dual inhibitors of PI3K and mTOR may provide a novel approach.

Molecular mechanisms of cancer development in obesity

The increasing incidence of obesity and its co-morbid conditions poses a great challenge to global health. In addition to cardiovascular disease and diabetes, epidemiological data demonstrate a link between obesity and multiple types of cancer. The molecular mechanisms underlying how obesity causes an increased risk of cancer are poorly understood. Obesity disrupts the dynamic role of the adipocyte in energy homeostasis, resulting in inflammation and alteration of adipokine (for example, leptin and adiponectin) signalling. Additionally, obesity causes secondary changes that are related to insulin signalling and lipid deregulation that may also foster cancer development. Understanding these molecular links may provide an avenue for preventive and therapeutic strategies to reduce cancer risk and mortality in an increasingly obese population.

Visceral obesity, metabolic syndrome, insulin resistance and cancer

This paper presents emerging evidence linking visceral adiposity and the metabolic syndrome (MetSyn) with carcinogenesis. The link between obesity and cancer has been clearly identified in a multitude of robust epidemiological studies. Research is now focusing on the role of visceral adipose tissue in carcinogenesis; as it is recognised as an important metabolic tissue that secretes factors that systemically alter the immunological, metabolic and endocrine milieu. Excess visceral adipose tissue gives rise to a state of chronic systemic inflammation with associated insulin resistance and dysmetabolism, collectively known as the MetSyn. Prospective cohort studies have shown associations between visceral adiposity, the MetSyn and increased risk of breast cancer, colorectal cancer and oesophageal adenocarcinoma. Furthermore, visceral adiposity and the MetSyn have been associated with increased tumour progression and reduced survival. The mechanisms by which visceral adiposity and the MetSyn are thought to promote tumorigenesis are manifold. These include alterations in adipokine secretion and cell signalling pathways. In addition, hyperinsulinaemia, subsequent insulin resistance and stimulation of the insulin-like growth factor-1 axis have all been linked with visceral adiposity and promote tumour progression. Furthermore, the abundance of inflammatory cells in visceral adipose tissue, including macrophages and T-cells, create systemic inflammation and a pro-tumorigenic environment. It is clear from current research that excess visceral adiposity and associated dysmetabolism play a central role in the pathogenesis of certain cancer types. Further research is required to elucidate the exact mechanisms at play and identify potential targets for intervention.

Cancer chemopreventive effects of lycopene: suppression of MMP-7 expression and cell invasion in human colon cancer cells

Clinical studies indicate that high blood levels of leptin or matrix metalloproteinase-7 (MMP-7; matrilysin) proteins are associated with tumor progression of human colorectal cancer (CRC). Leptin could play an important role in cell migration and invasion of cancer cells. Our previous study indicated that lycopene could inhibit the proliferation of human colon cancer cells in vitro. However, the inhibitory effects of lycopene on the progression of human colon cancer cells have not been demonstrated yet. In this study, we investigated the inhibitory effects of lycopene on tumor progression including cell invasion and MMP-7 expression in leptin-stimulated human colon cancer cells in vitro. Our results demonstrated that lycopene significantly inhibited leptin-mediated cell invasion and MMP-7 expression in human colon cancer HT-29 cells. Lycopene could augment the expression and stability of E-cadherin proteins. Our results showed that MAPK/ERK and PI3K/Akt signaling pathways played important roles in leptin-mediated MMP-7 expression and cell invasion. Lycopene could effectively inhibit the phosphorylation of Akt, glycogen synthase kinase-3β (GSK-3β) and ERK 1/2 proteins. The molecular mechanisms of lycopene were in part through decreases in nuclear levels of AP-1 and β-catenin proteins. These novel findings suggested that lycopene could act as a chemopreventive agent to suppress MMP-7 expression and leptin-mediated cell invasion in human colon cancer HT-29 cells.