Ob-R Expression Research Articles

Abstract 2911: Leptin Notch VEGFR-2 axis influences cancer stromal cell behavior

Abstract PURPOSE: Breast cancer cells induce changes in the stromal environment during malignancy. These changes promote growth, angiogenesis, invasion, and metastasis. The secretion of the adipokine, leptin, from adipose tissue has been shown to contribute to cell proliferation, migration and survival. We previously reported that leptin induces Notch, a pro-survival factor and contributor to the VEGF/VEGFR-2 pro-angiogenic system. We hypothesize that the leptin Notch axis induces activation of fibroblast cells and leads to endothelial cell proliferation, tubule formation, and survival. These effects could be related to leptin-induced Notch expression and VEGFR-2 transactivation, independent of VEGF. METHODS: Mouse Embryo Fibroblast cells (NIH/3T3), human umbilical vein endothelial cells (HUVEC) and porcine aorta endothelial cells (PAEC) were challenged with leptin (dose and time-response), and inhibitors of Notch (DAPT) and VEGFR-2 (SU5416 kinase inhibitor). Expression of Notch, VEGFR-2, Ob-R and phosphorylation of VEGFR-2 were determined. The impact of treatment on angiogenic features of endothelial cells was determined. To determine whether leptin-Notch axis activates fibroblast cells, leptin doses 0.6, 1.2, and 6.2 were used. RESULTS: Leptin induced phosphorylation of VEGFR-2 at intracellular site Y1175 and tubule formation in HUVEC. Leptin induced phosphorylation of VEGFR-2 at sites Y951, Y996, Y1059, and Y1175 in PAEC VEGFR2. Protein expression of Notch4 and Jagged1 was induced by leptin treatment in NIH/3t3 cells. CONCLUSION: Leptin secreted by fibroblast cells and/or adipose tissue may contribute to tumor angiogenesis by acting directly on stromal cells and inducing a VEGFR-2/Notch crosstalk. Novel therapies that target leptin signaling could be a new strategy for the prevention and treatment of breast cancer. These therapies could be more relevant for obese cancer patients with high circulating amounts of leptin. Citation Format: Viola Lanier, Merle Jeffers, Johannes Walterberger, Leonard Anderson, Ruben Gonzalez. Leptin Notch VEGFR-2 axis influences cancer stromal cell behavior. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2911. doi:10.1158/1538-7445.AM2015-2911

Upregulated Leptin in Periodontitis Promotes Inflammatory Cytokine Expression in Periodontal Ligament Cells.

Imbalance or disruption in the expression of inflammatory mediators contributes greatly to the breakdown of the periodontal supporting tissues. Leptin, through binding to its receptor (obesity-related leptin and leptin receptor [OBR]), has potent effects on immunity and inflammation. However, to date, researchers only indicated a role of leptin in periodontitis. No direct or valid evidence exists about how leptin and its receptor are regulated by local inflammation, what effects they have, and the underlying mechanisms. Experimental periodontitis was induced by ligation of mandibular second molars in beagle dogs. The expression of leptin, OBR, and interleukin (IL)-1β was examined by immunohistochemistry. Meanwhile, recombinant human IL-1β was used to stimulate human periodontal ligament cells (hPDLCs) in vitro, and mRNA and protein levels of leptin were measured using real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Then, mRNA and protein levels of IL-6 and IL-8 were measured using real-time PCR and ELISA, after stimulation with various concentrations of leptin, knocking down all or only the long form of OBR (OBRb) by small interfering RNA and incubation with multiple intracellular signaling pathway inhibitors, respectively. Leptin and OBR increased substantially in inflammatory periodontal tissues, which correlated well with the extent of inflammatory infiltration, and was a result of the upregulation in resident cells themselves. A high dose of leptin could induce the expression of mRNA and protein of IL-6 and IL-8 in hPDLCs through binding with OBRb and activating different intracellular signaling pathways. Upregulated leptin and OBR in periodontitis stimulated proinflammatory cytokine expression in PDL cells to additionally promote local inflammation.

Abstract B122: Hypoxia-inducible factor (HIF)-1α directly activates the leptin receptor (Ob-R) in pancreatic cancer cells

Abstract The aim of this study is to investigate the regulatory mechanism of Ob-R in pancreatic cancer cells. we found that HIF-1α expression was correlated with Ob-R in both pancreatic cancer cell lines and tissues. Overexpression of HIF-1α and hypoxia upregulated the expression of Ob-R in pancreatic cancer cells. When hypoxia-inducible factor (HIF)-1α gene was silenced in vitro, the expression of Ob-R was significantly decreased. Furthermore, HIF-1α directly bound to the hypoxia-responsive element (HRE) located in Ob-R gene promoter (-828/-832) and activated the transcription. Finally, we demonstrated that silence of HIF-1α gene reversed the inhibitory effect of leptin/ObR in pancreatic cancer cells. Taken together, our results indicated that HIF-1α directly regulated Ob-R expression in pancreatic cancer, which might be a valuable therapeutic target to pancreatic cancer. Note: This abstract was not presented at the conference. Citation Format: He Ren, Lingling Jia, Jihui Hao. Hypoxia-inducible factor (HIF)-1α directly activates the leptin receptor (Ob-R) in pancreatic cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr B122.

Activation of IL-8 via PI3K/Akt-dependent pathway is involved in leptin-mediated epithelial-mesenchymal transition in human breast cancer cells

Background Information: Previous studies have revealed that leptin may be involved in epithelial-mesenchymal transition (EMT), a crucial initiator of cancer progression to facilitate metastatic cascade, increase tumor recurrence, and ultimately cause poor prognosis. However, the underlying mechanism remains unclear. The aim of our present study was to investigate the effect of leptin on EMT of breast cancer cells and the underlying mechanism. Results: Our data demonstrated that leptin significantly increased the phosphorylation of STAT3, Akt, and ERK1/2, elevated the expression of IL-8, and induced breast cancer cells to undergo EMT. The effect of leptin on IL-8 could visibly abolished by the inhibitor of PI3K LY294002. In addition, leptin-induced EMT of breast cancer cells was blocked by anti-IL-8 antibodies. Examination of the expression of ObR, leptin, IL-8 and EMT-related biomarkers in patient specimens demonstrated that malignant breast carcinoma with lymph node metastases (LNM), which represents poor prognosis, expressed higher levels of ObR, leptin, IL-8 than other types of breast cancer, and displayed more obvious EMT transversion. In vivo xenograft experiment revealed that leptin signally promoted tumor growth and metastasis and increased the expressions of IL-8 and EMT-related biomarkers. Conclusions: Our results support that leptin-induced EMT in breast cancer cells requires IL-8 activation via the PI3K/Akt signal pathway.

Leptin Receptor (OBR) Resistance On Immune Cells From People With Obesity

Leptin hormone controls food intake and has important immune functions. People with obesity show hypothalamic OBR resistance leading to high serum leptin levels. The increased risk to infections in people with obesity could be related to OBR resistance on immune cells. Few studies have compared the immune response between people with obesity matched with normal controls. This study compared the expression and response of the OBR on peripheral blood mononuclear cells (PBMCs) isolated from people with obesity and healthy controls. Fifteen subjects with obesity and age and sex matched normal weight controls participated in the study. Peripheral blood mononuclear cells were isolated from control and people with obesity after overnight fasting and were cultured with or without leptin or LPS for 24 hours. At the end of the treatment period, IL‐1β, IL‐6, and TNF‐α were measured by ELISA from culture supernatants. Also the expression of OBR on the surface of freshly isolated PBMCs was measured by flow cytometry. Data indicate that there was lower expression of OBR on PBMCs from subjects with obesity than from normal controls. Down‐regulation on the expression of OBR could indicate resistance to leptin stimulation. Also, there was lower production of IL‐1β, IL‐6, and TNF‐α in the supernatants of cultured PBMCs from subjects with obesity after leptin and LPS treatment than from normal controls. A lower cytokine production after leptin stimulation could also indicate OBR resistance due to lower expression and faulty activity of the receptor. Together these data are consistent with partial resistance of OBR on PBMCs from patients with obesity.

Long‑term exposure to leptin enhances the growth of prostate cancer cells.

Obesity correlates with an increased risk of developing prostate cancer (PCa) and leptin plays an important role in PCa progression. Since leptin is produced by adipocytes, the serum leptin level is higher in obese than in non-obese individuals. However, the effects of leptin remain controversial and unclear. The aim of the present study was to investigate the effect of leptin on PCa cell aggressiveness. Three human PCa cell lines (LNCaP, DU145 and PC-3) were treated with recombinant leptin for 28 days. Cell proliferation, migration, and invasion were estimated using the WST assay, a wound-healing assay, and a BD Matrigel invasion assay, respectively. The mechanism underlying the proliferative effect of leptin was investigated by cell transfections with small interfering RNA (siRNA) against the leptin receptor (ObR) or forkhead box O1 (FOXO1), and by immunocytochemistry. Long-term exposure of PCa cells to leptin enhanced their proliferation, migration and invasion. Leptin increased ObR expression and enhanced Akt phosphorylation constitutively. Leptin also increased the phosphorylation of FOXO1 via PI3K signaling and FOXO1 gene silencing enhanced PCa cell proliferation. Leptin induced the translocation of FOXO1 from the nucleus to the cytoplasm. Furthermore, the PI3K inhibitor, LY294002 suppressed this translocation. These results suggested that leptin regulated the subcellular localization of FOXO1 and induced Akt phosphorylation. Additionally, we revealed that leptin increased the expression of cyclin D1 and decreased the expression of p21 protein. In conclusion, long-term exposure to leptin increased the cell proliferation, migration, and invasion of PCa cells through inactivation of FOXO1. This inactivation resulted from exclusion of FOXO1 from the nucleus and its restriction to the cytoplasm through PI3K/Akt signaling. Our findings contribute to an understanding of the association between obesity and PCa aggressiveness.

Obesity, expression of adipocytokines, and macrophage infiltration in canine mammary tumors

Obesity influences the development, progression and prognosis of human breast cancer and canine mammary cancer (MC) but the precise underlying mechanism is not well-documented in the fields of either human or veterinary oncology. In the present study, the expression of major adipocytokines, including leptin, adiponectin, and leptin receptor (ObR) in benign (n = 28) and malignant (n = 70) canine mammary tumors was investigated by immunohistochemistry and on the basis of the subject's body condition score (BCS). To evaluate the relationship between obesity and chronic inflammation of the mammary gland, macrophages infiltrating within and around tumoral areas were counted.The mean age of MC development was lower in overweight or obese dogs (9.0 ± 1.8 years) than in lean dogs or optimal bodyweight (10.2 ± 2.9 years), and the evidence of lymphatic invasion of carcinoma cells was found more frequently in overweight or obese group than in lean or optimal groups. Decreased adiponectin expression and increased macrophage numbers in overweight or obese subjects were significantly correlated with factors related to a poor prognosis, such as high histological grade and lymphatic invasion. Leptin expression was correlated with progesterone receptor status, and ObR expression was correlated with estrogen receptor status of MCs, regardless of BCS. Macrophage infiltration within and around the tumor may play an important role in tumor progression and metastasis in obese female dogs and may represent a prognostic factor for canine MCs.

Chronic sleep fragmentation during the sleep period induces hypothalamic endoplasmic reticulum stress and PTP1b-mediated leptin resistance in male mice.

Sleep fragmentation (SF) is highly prevalent and may constitute an important contributing factor to excessive weight gain and the metabolic syndrome. Increased endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) leading to the attenuation of leptin receptor signaling in the hypothalamus leads to obesity and metabolic dysfunction. Mice were exposed to SF and sleep control (SC) for varying periods of time during which ingestive behaviors were monitored. UPR pathways and leptin receptor signaling were assessed in hypothalami. To further examine the mechanistic role of ER stress, changes in leptin receptor (ObR) signaling were also examined in wild-type mice treated with the ER chaperone tauroursodeoxycholic acid (TUDCA), as well as in CHOP-/+ transgenic mice. Fragmented sleep in male mice induced increased food intake starting day 3 and thereafter, which was preceded by increases in ER stress and activation of all three UPR pathways in the hypothalamus. Although ObR expression was unchanged, signal transducer and activator of transcription 3 (STAT3) phosphorylation was decreased, suggesting reduced ObR signaling. Unchanged suppressor of cytokine signaling-3 (SOCS3) expression and increases in protein-tyrosine phosphatase 1B (PTP1B) expression and activity emerged with SF, along with reduced p-STAT3 responses to exogenous leptin. SF-induced effects were reversed following TUDCA treatment and were absent in CHOP -/+ mice. SF induces hyperphagic behaviors and reduced leptin signaling in hypothalamus that are mediated by activation of ER stress, and ultimately lead to increased PTP1B activity. ER stress pathways are therefore potentially implicated in SF-induced weight gain and metabolic dysfunction, and may represent a viable therapeutic target.

Leucine supplementation improves leptin sensitivity in high-fat diet fed rats

BackgroundSeveral studies have reported the favorable effect of leucine supplementation on insulin resistance or insulin sensitivity. However, whether or not leucine supplementation improves leptin sensitivity remains unclear.DesignForty-eight male Sprague-Dawley rats were fed with either a high-fat diet (HFD) or HFD supplemented with 1.5, 3.0, and 4.5% leucine for 16 weeks. At the end of the experiment, serum leptin level was measured by ELISA, and leptin receptor (ObR) in the hypothalamus was examined by immunohistochemistry. The protein expressions of ObR and leptin-signaling pathway in adipose tissues were detected by western blot.ResultsNo significant differences in body weight and food/energy intake existed among the four groups. Serum leptin levels were significantly lower, and ObR expression in the hypothalamus and adipose tissues was significantly higher in the three leucine groups than in the control group. These phenomena suggested that leptin sensitivity was improved in the leucine groups. Furthermore, the expressions of JAK2 and STAT3 (activated by ObR) were significantly higher, and that of SOCS3 (inhibits leptin signaling) was significantly lower in the three leucine groups than in the control group.ConclusionsLeucine supplementation improves leptin sensitivity in rats on HFD likely by promoting leptin signaling.

Selective glucocorticoid receptor modulator compound A, in contrast to prednisolone, does not induce leptin or the leptin receptor in human osteoarthritis synovial fibroblasts.

Glucocorticoids are powerful anti-inflammatory compounds that also induce the expression of leptin and leptin receptor (Ob-R) in synovial fibroblasts through TGF-βsignalling and Smad1/5 phosphorylation. Compound A (CpdA), a selective glucocorticoid receptor agonist, reduces inflammation in murine arthritis models and does not induce diabetes or osteoporosis, thus offering an improved risk:benefit ratio in comparison with glucocorticoids. Due to the detrimental role of leptin in OA pathogenesis, we sought to determine whether CpdA also induced leptin and Ob-R protein expression as observed with prednisolone. Human synovial fibroblasts and chondrocytes were isolated from the synovium and cartilage of OA patients after joint surgery. The cells were treated with prednisolone, TGF-β1, TNF-α and/or CpdA. Levels of leptin, IL-6, IL-8, MMP-1 and MMP-3 were measured by ELISA and expression levels of Ob-R phospho-Smad1/5, phospho-Smad2, α-tubulin and glyceraldehyde 3-phosphate dehydrogenase were analysed by western blotting. CpdA, unlike prednisolone, did not induce leptin secretion or Ob-R protein expression in OA synovial fibroblasts. Moreover, CpdA decreased endogenous Ob-R expression and down-regulated prednisolone-induced leptin secretion and Ob-R expression. Mechanistically, CpdA, unlike prednisolone, did not induce Smad1/5 phosphorylation. CpdA, similarly to prednisolone, down-regulated endogenous and TNF-α-induced IL-6, IL-8, MMP-1 and MMP-3 protein secretion. The dissociative effect of CpdA was confirmed using chondrocytes with no induction of leptin secretion, but with a significant decrease in IL-6, IL-8, MMP-1 and MMP-3 protein secretion. CpdA, unlike prednisolone, did not induce leptin or Ob-R in human OA synovial fibroblasts, thereby demonstrating an improved risk:benefit ratio.

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.

Expression of leptin and its receptor in thyroid carcinoma: distinctive prognostic significance in different subtypes.

To investigate the potential prognostic significance of leptin and its receptor (Ob-R) in thyroid carcinoma. The study cohort consisted of 173 patients including 93 cases with papillary thyroid carcinoma (PTC), 41 cases with follicular thyroid carcinoma (FTC), 25 cases with medullary thyroid carcinoma (MTC) and 14 cases with anaplastic thyroid carcinoma (ATC). We investigated the correlation between clinicopathological features and leptin or Ob-R. The Kaplan-Meier method was used to analyse the survival rate. There was a strong correlation of leptin expression with Ob-R expression in PTC, FTC and ATC. For PTC, leptin expression was strongly correlated with older age, larger tumour size, nodal metastasis and advanced stage. Ob-R was significantly correlated with larger tumour size, nodal metastasis and advanced stage. The 5-year disease-free survival (DFS) rate in patients with positive leptin or its receptor expression was lower than that in patients without expression (with statistical difference). For FTC, patients with positive leptin or Ob-R expression developed no recurrence or metastasis during the follow-up. For MTC, Ob-R was significantly correlated with nodal metastasis and advanced stage (P<0·05). For ATC, patients with positive Ob-R expression had longer median DFS than those with negative expression (436±185 vs 57±71days), and the difference in the survival rate was statistically significant (P<0·05). There was a strong correlation of leptin expression with Ob-R expression in PTC, FTC and ATC. Leptin and Ob-R had negative prognostic significance in PTC, while Ob-R may play a protective role in ATC.

Carnosic acid suppresses colon tumor formation in association with antiadipogenic activity.

This study determined the efficacy of carnosic acid (CA) for suppressing colon carcinogenesis associated with excess adiposity. Cell growth regulation by CA was evaluated in HT-29 colon adenocarcinoma cells cocultured with 3T3-L1 adipocytes. To determine the in vivo efficacies, male A/J mice were divided into four groups and fed one of the following experimental diets for 11 wk: 15% fat, 45% fat, 45% fat + 0.01% CA, or 45% fat + 0.02% CA. Azoxymethane was administered at the beginning of experimental diet and two cycles of dextran sodium sulfate were supplied 1 wk after the azoxymethane injection. The proliferation of HT-29 cells cocultured with 3T3-L1 cells was significantly higher than proliferation of control cells (p < 0.05). CA treatment suppressed the growth of cocultured HT-29 cells through cell cycle arrest and enhanced apoptosis by inhibiting leptin receptor (Ob-R) signaling, including Akt and extracellular signal-regulated kinase (ERK) phosphorylation. CA supplementation in vivo decreased the number of colon tumors and reduced circulating concentrations of leptin, adiponectin, insulin, and insulin-like growth factor 1. Colonic expression of Ob-R, insulin receptor (IR), p-Akt, p-ERK, B-cell lymphoma extra large (Bcl-xL), and cyclinD1 protein was also suppressed in animals fed CA. CA appears to alleviate adipocity-related acceleration of colon tumor formation.

Abstract 4738: Clinicopathological roles of adiponectin receptor and leptin receptor in endometrial carcinoma

Abstract Objectives: To clarify the roles of adiponectin receptor (AdipoR) and leptin receptor (ObR) in endometrial carcinoma, expressions of AdipoR-1 and -2 and ObR in endometrial cancer were examined immunohistochemically and relationships to clinicopathological implications were also analyzed. Methods: Under the written informed consent, paraffin-embedded tissues were obtained from 77 patients with endometrial carcinoma and were stained immunohistochemically using antibodies against AdipoR-1, AdipoR-2 and ObR. Results: AdipoR-1, AdipoR-2 and ObR were localized predominantly in the cell membrane and cytoplasm of tumor cells and normal endometrial cells. In 77 cases of endometrial cancer, positive expression was observed in 46 cases (59.7%) for AdipoR-1, 47 cases (61.0%) for AdipoR-2 and 33 cases (42.9%) for ObR. Expression of AdipoR-1 was observed more in stage I cases, G1 tumours, tumors with shallow myometrial invasion, tumors negative for lymphovascular space involvement, cases negative for adnexal invasion, and cases with no lymph node metastasis. However, expressions of AdipoR-2 and ObR showed no relationship to any clinicopathological factors. Kaplan-Meier analyses revealed that progression-free and overall survivals were longer in cases with positive AdipoR-1 expression compared with negative AdipoR-1 expression. Conclusion: Poor expression of AdipoR-1 thus appears to be associated with tumour grade, myometrial invasion, adnexal invasion, lymph-vascular space involvement and lymph-node metastasis, as well as poor prognosis in endometrial cancer. Citation Format: Hiromitsu Yabushita, Keita Iwasaki, Taiki Ueno, Akihiko Wakatsuki. Clinicopathological roles of adiponectin receptor and leptin receptor in endometrial carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4738. doi:10.1158/1538-7445.AM2014-4738

Hypoxia inducible factor (HIF)-1α directly activates leptin receptor (Ob-R) in pancreatic cancer cells

The aim of this study is to investigate the regulatory mechanism of leptin receptors (Ob-R) in pancreatic cancer. We found that the over-expression of hypoxia inducible factor (HIF-1)α and hypoxia up-regulated the expression of Ob-R in pancreatic cancer cells. When HIF-1α gene was silenced in vitro, the expression of Ob-R was significantly decreased. Xenograft mouse models showed that the inhibition of HIF-1α resulted in the concomitant decrease of Ob-R in vivo. In addition, HIF-1α expression was correlated with Ob-R in pancreatic cancer tissues by immunohistochemical staining. Clinical data showed that over-expression of HIF-1 was associated with pathological tumor node metastasis stage, lymph node metastasis and overall survival. HIF-1α directly bound to the hypoxia-responsive element (HRE) located in Ob-R gene promoter (−828/−832) and activated the transcription. Finally, we demonstrated that the silence of HIF-1α gene reversed the inhibitory effect of leptin/Ob-R in pancreatic cancer cells. Taken together, our results indicate that HIF-1α directly regulated Ob-R expression in pancreatic cancer, which might be a valuable therapeutic target for pancreatic cancer.

Leptin Induces a Proliferative Response in Breast Cancer Cells but Not in Normal Breast Cells

Obesity is a risk factor for breast cancer in postmenopausal women. Leptin, a hormone excessively produced during obesity, is suggested to be involved in breast cancer. The aim of the study was to investigate procarcinogenic potential of leptin by evaluating influence of leptin on cell proliferation, cell cycle, apoptosis, and signaling on numerous breast cells lines, including 184B5 normal cells, MCF10A fibrocystic cells and MCF-7, MDA-MB-231, and T47D cancer cells. Expressions of leptin and Ob-R were analyzed using qRT-PCR and immunohistochemistry, proliferation using fluorimetric resazurin reduction test and xCELLigence system, apoptosis and cell cycle by flow cytometry, and effect of leptin on different signalling pathways using qRT-PCR and Western blot. Cells were exposed to increasing concentrations of leptin. All cell lines expressed mRNA and protein of leptin and Ob-R. Leptin stimulated proliferation of all cell lines except for 184B5 and MDA-MB-231 cells. Leptin inhibited apoptosis but didn't alter proportion of cells within cell cycle in MCF7 cells. Leptin induced overexpression of leptin, Ob-R, estrogen receptor, and aromatase mRNA in MCF-7 and T47D cells. Autoregulation induced by leptin, relationship with estrogen pathway, and proliferative and antiapoptic activity in breast cancer cells may explain that obesity-associated hyperleptinemia may be a breast cancer risk factor.

Leptin and adiponectin receptor expression in oesophageal cancer

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

The role of leptin in gastric cancer: Clinicopathologic features and molecular mechanisms

Obesity is associated with certain types of cancer, including gastric cancer. However, it is still unclear whether obesity-related cytokine, leptin, is implicated in gastric cancer. Therefore, we aimed to investigate the role of leptin in gastric cancer. The expression of leptin and its receptor, Ob-R, was assessed by immunohistochemical staining and was compared in patients with gastric adenoma (n=38), early gastric cancer (EGC) (n=38), and advanced gastric cancer (AGC) (n=38), as a function of their clinicopathological characteristics. Gastric cancer cell lines were studied to investigate the effects of leptin on the signal transducer and activator of transcription-3 (STAT3) and extracellular receptor kinase 1/2 (ERK1/2) signaling pathways using MTT assays, immunoblotting, and inhibition studies. Leptin was expressed in gastric adenomas (42.1%), EGCs (47.4%), and AGCs (43.4%). Ob-R expression tended to increase from gastric adenoma (2%), through EGC (8%), to AGC (18%). Leptin induced the proliferation of gastric cancer cells by activating STAT3 and ERK1/2 and up-regulating the expression of vascular endothelial growth factor (VEGF). Blocking Ob-R with pharmacological inhibitors and by RNAi decreased both the leptin-induced activation of STAT3 and ERK1/2 and the leptin-induced expression of VEGF. Leptin plays a role in gastric cancer by stimulating the proliferation of gastric cancer cells via activating the STAT3 and ERK1/2 pathways.

Clinicopathological roles of adiponectin and leptin receptors in endometrial carcinoma.

To clarify the roles of adiponectin receptor (AdipoR) and leptin receptor (ObR) in endometrial carcinoma, the expression of AdipoR-1 and -2 and ObR in endometrial cancer was examined immunohistochemically, and correlations with clinicopathological implications were also analysed. Paraffin-embedded tissues were obtained from 77 patients with endometrial carcinoma and were stained immunohistochemically using antibodies against AdipoR-1, AdipoR-2 and ObR. AdipoR-1, AdipoR-2 and ObR were localised predominantly in the cell membrane and cytoplasm of tumour cells and normal endometrial cells. In 77 cases of endometrial cancer, positive expression was observed in 46 cases (59.7%) for AdipoR-1, 47 cases (61.0%) for AdipoR-2 and 33 cases (42.9%) for ObR. Expression of AdipoR-1 was observed most in stage I cases, G1 tumours, tumours with shallow myometrial invasion, tumours negative for lymphovascular space involvement, cases negative for adnexal invasion and cases with no lymph node metastasis. However, the expression of AdipoR-2 and ObR showed no correlation with any clinicopathological factors. Kaplan-Meier analyses revealed that progression-free and overall survival times were longer in cases with positive AdipoR-1 expression compared with negative AdipoR-1 expression. Poor expression of AdipoR-1, thus, appears to be associated with tumour grade, myometrial invasion, adnexal invasion, lymph-vascular space involvement and lymph node metastasis, as well as poor prognosis, in endometrial cancer.

Increased expression of the leptin receptor in human ovaries affected by endometrioma and detection of high levels of leptin in the ovarian endometriomal fluid

BackgroundThis study was designed to investigate leptin levels in the fluid in ovarian endometriomas (OEs) and to compare the expression of leptin and its receptors (OBR) in ovarian tissue affected by endometrioma in infertile women to its expression in the normal ovarian tissue of fertile controls without endometriosis.MethodsIn this case–control observational study, ovarian tissue, blood samples and peritoneal fluid were obtained from 20 women (10 fertile controls without endometriosis or any ovarian disease, who were undergoing tubal ligation surgery, and 10 infertile women with severe endometriosis and OE). The ovarian endometriomal fluid (EF) was aspirated, and peritoneal-implant (PI) biopsies were performed. The tissues removed during the surgeries were immediately frozen in liquid nitrogen to determine expression levels by western blot and leptin levels by ELISA.ResultsOBR was expressed at higher levels in the ovarian tissue affected by endometrioma than in the normal ovarian tissue (control = 0.38 ± 0.05, study = 0.60 ± 0.09, p = 0.03), but there was no significant difference in leptin levels between these groups (control = 0.57 ± 0.1, study = 0.35 ± 0.1, p = 0.18). Positive and significant correlations were observed between leptin and OBR in the OE (r = 0.85, p = 0.004) and in the PI (r = 0.87, p = 0.001). ELISA results demonstrate a greater leptin concentration within the EF compared with the serum and the PF (serum = 14.25 ± 1.63, PF = 5.98 ± 2.0, EF = 73.8 ± 16.2, p = 0.0001), but there was no correlation between these variables. A positive, significant and strong correlation was observed between PF leptin levels and the expression of leptin and OBR in PI (leptin: r = 0.78, p = 0.007/OBR: r = 0.68, p = 0.04) and between the EF leptin levels and the expression of leptin and OBR in the OE (leptin: r = 0.88, p = 0.008/OBR: r = 0.89, p = 0.005).ConclusionsThese data suggest that leptin may play an important role in the physiopathology of OE through a modulatory interaction with its active receptor.