Targeting Leptin as a Therapeutic Strategy against Ovarian Cancer Peritoneal Metastasis

Epigenetic modifications in obesity-associated diseases

The global prevalence of obesity has reached epidemic levels, significantly elevating the susceptibility to various cardiometabolic conditions and certain types of cancer. In addition to causing metabolic abnormalities such as insulin resistance (IR), elevated blood glucose and lipids, and ectopic fat deposition, obesity can also damage pancreatic islet cells, endothelial cells, and cardiomyocytes through chronic inflammation, and even promote the development of a microenvironment conducive to cancer initiation. Improper dietary habits and lack of physical exercise are important behavioral factors that increase the risk of obesity, which can affect gene expression through epigenetic modifications. Epigenetic alterations can occur in early stage of obesity, some of which are reversible, while others persist over time and lead to obesity-related complications. Therefore, the dynamic adjustability of epigenetic modifications can be leveraged to reverse the development of obesity-associated diseases through behavioral interventions, drugs, and bariatric surgery. This review provides a comprehensive summary of the impact of epigenetic regulation on the initiation and development of obesity-associated cancers, type 2 diabetes, and cardiovascular diseases, establishing a theoretical basis for prevention, diagnosis, and treatment of these conditions.

Progress in the treatment of malignant ascites

Malignant ascites occurs as a symptom of the terminal stage of cancer, affecting the quality of life through abdominal distension, pain, nausea, anorexia, dyspnea and other symptoms. We describe the current main drug treatments in addition to surgery according to the traditional and new strategies. Traditional treatments were based on anti-tumor chemotherapy and traditional Chinese medicine treatments, as well as diuretics to relieve the patient's symptoms. New treatments mainly involve photothermal therapy, intestinal therapy and targeted immunity. This study emphasizes that both traditional and new therapies have certain advantages and disadvantages, and medication should be adjusted according to different periods of use and different patients. In conclusion, this article reviews the literature to systematically describe the primary treatment modalities for malignant ascites.

Adipokines and epithelial-mesenchymal transition (EMT) in cancer

Obesity is a significant risk factor for cancer development. Within the tumor microenvironment, adipocytes interact with cancer cells, immune cells, fibroblasts and endothelial cells, and orchestrate several signaling pathways by secreting bioactive molecules, including adipokines. Adipokines or adipocytokines are produced predominantly by adipocytes and function as autocrine, paracrine and endocrine mediators. Adipokines can exert pro- and anti-inflammatory functions, and they play a pivotal role in the state of chronic low-grade inflammation that characterizes obesity. Epithelial-mesenchymal transition (EMT), a complex biological process whereby epithelial cells acquire the invasive, migratory mesenchymal phenotype is well-known to be implicated in cancer progression and metastasis. Emerging evidence suggests that there is a link between adipokines and EMT. This may contribute to the correlation that has been documented between obesity and cancer progression. This review summarizes the existing body of evidence supporting an association between the process of EMT in cancer and the adipokines leptin, adiponectin, resistin, visfatin/NAMPT, lipocalin-2/NGAL, as well as other newly discovered adipokines including chemerin, nesfatin-1/nucleobindin-2, AZGP1, SFRP5 and FABP4.

Leptin induces leiomyoma cell proliferation and extracellular matrix deposition via JAK2/STAT3 and MAPK/ERK pathways

OBJECTIVE

To investigate the molecular effects of leptin on uterine leiomyoma cells.

DESIGN

Experimental study using in vitro culture of immortalized human leiomyoma (HuLM) cells.

SETTING

Academic university center.

PATIENT(S)

Women with uterine fibroids who underwent a hysterectomy or myomectomy.

INTERVENTION(S)

Administration of human recombinant leptin to the media of cultured HuLM cells separately or in combination with pharmacologic Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) inhibitors.

MAIN OUTCOME MEASURE(S)

We examined HuLM tissues and cells for the expression of the leptin receptor, termed OB-R. Cellular proliferation was measured at 6, 24, and 48 hours using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay. Protein expression levels of proliferating cell nuclear antigen, collagen 1, phosphorylated STAT3/total STAT3, and phosphorylated ERK1/2 and total ERK1/2 were quantified using immunoblotting. Pharmacologic inhibitors were employed to further assess the role of the JAK2/STAT3 and MAPK/ERK pathways in the proliferative response.

RESULT(S)

The presence of OB-R was confirmed in clinical leiomyoma and myometrial tissue obtained from 3 separate human subjects using immunofluorescence staining, and the expression of OB-R in HuLM cells was identified using immunoblotting. There was no significant difference in the expression of the leptin receptor in the myometrium compared with that in the leiomyoma tissue. Leptin stimulated cell proliferation and extracellular matrix (ECM) deposition at 24 hours after treatment. Pretreatment with a JAK2/STAT3 inhibitor attenuated ECM deposition, and pretreatment with a MAPK/ERK inhibitor significantly decreased leptin's stimulatory effect on cell proliferation and ECM deposition.

CONCLUSION(S)

Leptin induces a proliferative response and ECM deposition in HuLM cells. These findings suggest that leptin, acting through the JAK2/STAT3 and MAPK/ERK pathways, is involved in the development of uterine leiomyomas, which may partly explain their increased incidence in obese women.

Leptin hormone and its effectiveness in reproduction, metabolism, immunity, diabetes, hopes and ambitions

Leptin is a hormone derived from adipose tissue and the small intestine, mainly in enterocytes; it helps regulate the energy balance by suppressing hunger, resulting in decreased fat mass in adipocytes. Leptin has specific receptors in the ventromedial and arcuate nuclei and other parts of the hypothalamus and the feeding center in the ventral tegmental area. It also plays a role in regulatory aspects other than fat cells, such as obesity, which is linked to a loss of sensitivity of leptin receptors, resulting in an inability to produce satiety and an increase in food intake. Moreover, leptin plays a part in lactation, bone density, the immune system, diabetes treatments, and hypertriglyceridemia. The latest studies in leptin suggest that an analog of leptin may treat DM and hypertriglyceridemia. Further research should be conducted on the effectiveness of leptin on other related diseases.

Mesenchymal Stem Cells in Adipose Tissue and Extracellular Vesicles in Ovarian Cancer Patients: A Bridge toward Metastatic Diffusion or a New Therapeutic Opportunity?

Ovarian cancer is one of the deadliest malignancies among women. Approximately 75% of the patients with ovarian cancer are diagnosed with advanced disease that already has metastasis, particularly to the omentum. The omentum constitutes the ideal soil for ovarian cancer metastasis due to a complex intraperitoneal milieu that favors and supports the whole metastatic process. Adipose-derived stem/stromal cells (ADSCs) are part of this microenvironment and foster tumor progression via sustained paracrine secretion, including extracellular vesicles (EVs). Nonetheless, the preferential relationship between ADSCs, ADSC-derived EVs, and ovarian cancer cells could be exploited to use ADSCs and EVs as a vehicle for anti-cancer therapies. This review will analyze the strict relations between tumor progression, metastatic disease, and adipose tissue with its staminal components. In addition, we will describe the crosstalk and biologic relationship between ADSCs and tumor cells, the role of EVs in intercellular communication, the establishment of drug resistance, metastatic capacity, and ovarian cancer progression. We will analyze the new therapeutic opportunities in treating ovarian cancer offered by ADSCs and EVs as a vehicle for therapeutic molecules to target precisely tumor cells and limit the systemic adverse effects. Finally, we will discuss the limitations of these therapeutic approaches.

Obesity and Energy Substrate Transporters in Ovarian Cancer-Review

Ovarian cancer is the seventh most common cancer in women. It is characterized by a high mortality rate because of its aggressiveness and advanced stage at the time of diagnosis. It is a nonhomogenous group of neoplasms and, of which the molecular basics are still being investigated. Nowadays, the golden standard in the treatment is debulking cytoreductive surgery combined with platinum-based chemotherapy. We have presented the interactions and the resulting perspectives between fatty acid transporters, glucose transporters and ovarian cancer cells. Studies have shown the association between a lipid-rich environment and cancer progression, which suggests the use of correspondent transporter inhibitors as promising chemotherapeutic agents. This review summarizes preclinical and clinical studies highlighting the role of fatty acid transport proteins and glucose transporters in development, growth, metastasizing and its potential use in targeted therapies of ovarian cancer.

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.

Adipocytes: active facilitators in epithelial ovarian cancer progression?

There is growing evidence that adipocytes play important roles in the progression of multiple cancers. Moreover, in obesity, adipocytes alter their original functions and contribute to the metabolic and inflammatory changes of adipose tissue microenvironment, which can further enhance tumor development. At present, the roles of adipocytes in the pathogenesis of epithelial ovarian cancer (EOC) are far from being fully elucidated. Herein, we summarized the recent advances in understanding the roles of adipocytes in EOC progression. Adipocytes, close neighbors of EOC tissue, promote EOC growth, invasion, metastasis and angiogenesis through adipokine secretion, metabolic remodeling and immune microenvironment modulation. Moreover, adipocytes are important therapeutic targets and may work as useful anticancer drug delivery depot for EOC treatment. Furthermore, adipocytes also act as a therapeutic obstacle for their involvement in EOC treatment resistance. Hence, better characterization of the adipocytes in EOC microenvironment and the crosstalk between adipocytes and EOC cells may provide insights into EOC progression and suggest novel therapeutic opportunities.

Leptin promotes bone metastasis of breast cancer by activating the SDF-1/CXCR4 axis

Obesity is associated with an increased risk of tumorigenesis, and increased leptin levels can promote tumor metastasis. However, the effects of leptin on bone metastasis in breast cancer are not fully understood. Here, we examined leptin receptor expression and bone metastasis in tissue samples from 96 breast cancer patients. In addition, we investigated the effects of leptin on the metastatic capacity of breast cancer cells in vitro using a transwell assays. The results indicated that higher leptin receptor levels in breast cancer cells are associated with increased incidence of bone metastasis in breast cancer patients. Additionally, leptin promoted migration and invasion of breast cancer cells. The SDF-1/CXCR4 axis activated by leptin also promoted bone metastasis of breast cancer. Finally, increased CXCR4 expression was accompanied by high leptin receptor expression in bone metastatic tissues from breast cancer patients. These results indicate that leptin induces bone metastasis of breast cancer by activating the SDF-1/CXCR4 axis.

Evaluation of the Impact of Cisplatin on Variances in the Expression Pattern of Leptin-Related Genes in Endometrial Cancer Cells

This research aimed to assess the impact of cisplatin, depending on the concentration and exposure time, on the expression pattern of leptin in an endometrial cancer cell line. Ishikawa endometrial cancer cell cultures were incubated with cisplatin, at concentrations of 2.5–10 µM, or leptin in the concentration range 10–40 ng/mL, and for durations of 12, 24 and 48 h compared with the control. The microarray techniques: RTqPCR; ELISA; and RNAi assay were used. Statistical analysis was performed at p < 0.05. Already with the lowest concentration and incubation time, statistically substantial silencing of leptin expression on the mRNA level under the influence of cisplatin after its addition to the culture was observed. On the protein level, the expression for cisplatin at a concentration of 2.5 µM was only noticeable after 48 h of exposure and maintained themselves with consecutively larger concentrations. It was observed that cisplatin at a concentration of 5 µM is IC₅₀ and the drug activated apoptosis via caspases -3 and -9. Cisplatin at a concentration of 5 µM and higher has a significant effect on the concentration of leptin. The effect of cisplatin on the expression profile of genes associated with leptin-dependent signaling pathways and changes in the expression of leptin itself and its receptors was confirmed. It was also confirmed that cisplatin exerted its effect via the leptin pathway.

The untapped potential of ascites in ovarian cancer research and treatment

The build-up of fluid in the peritoneal cavity-ascites-is a hallmark of ovarian cancer, the most lethal of all gynaecological malignancies. This remarkable fluid, which contains a variety of cellular and acellular components, is known to contribute to patient morbidity and mortality by facilitating metastasis and contributing to chemoresistance, but remains largely under-researched. In this review, we will critically analyse the evidence associating ascites with metastasis and chemoresistance in ovarian cancer and provide an update on research in the field. We will argue the case for ascites as a unique and accessible substrate for tracking tumour progression and for translational research that will enhance our understanding of this cancer and lead to improvements in patient outcomes.

Leptin stimulates the epithelial‑mesenchymal transition and pro‑angiogenic capability of cholangiocarcinoma cells through the miR‑122/PKM2 axis

Leptin is an adipokine minimally known for its activities or underlying mechanisms in cholangiocarcinoma. The present study explored the effects of leptin on the epithelial‑mesenchymal transition (EMT) and pro‑angiogenic capability of cholangiocarcinoma cells, and investigated the underlying mechanisms. Cholangiocarcinoma cells were treated with leptin, and their migration and invasion rates were investigated using Transwell assays. Furthermore, conditioned medium was collected from cholangiocarcinoma cells following leptin treatment and applied to human umbilical vein endothelial cells to assess tube formation. The expression of EMT and pro‑angiogenic factors was examined by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses. Mechanistically, the function of pyruvate kinase muscle isozyme M2 (PKM2) was assessed in leptin‑induced phenotypes using siRNA targeting PKM2 (si‑PKM2). Bioinformatics screening and luciferase reporter assays were used to reveal microRNA (miR)‑122 as the potential mediator between leptin and PKM2. Finally, the associations between leptin and miR‑122 or PKM2 levels in patients with cholangiocarcinoma were assessed by ELISA and RT‑qPCR. Leptin significantly increased the EMT and pro‑angiogenic capability of cholangiocarcinoma cells, visibly inhibited endogenous miR‑122 expression, and upregulated PKM2. Furthermore, si‑PKM2 inhibited leptin‑induced migration, invasion, EMT‑associated marker expression levels and the pro‑angiogenic capability in cholangiocarcinoma cells. In addition, miR‑122 negatively regulated the expression of PKM2. When applied together with leptin, miR‑122 was sufficient to reverse the multiple malignancy‑promoting effects of leptin. Consistently, the serum leptin level positively correlated with that of PKM2, but negatively with that of miR‑122 in patients with cholangiocarcinoma. Leptin, by downregulating miR‑122 and elevating PKM2 expression, acts as a pleiotropic pro‑malignancy cytokine for cholangiocarcinoma. Therefore, increasing miR‑122 expression and inhibiting PKM2 may be future approaches for cholangiocarcinoma treatment.

The influence of leptin on the process of carcinogenesis

Obesity is a new risk factor, to which more and more research is devoted, related to the development of cancer. Many studies of recent years have drawn attention to the role of adipose tissue as an important internal endocrine organ. In the adipose tissue proteins are produced, referred to by the common name as adipokines. In the case of obesity, the neoplasm cells are constantly stimulated by pro-inflammatory cytokines and adipokines, among which leptin dominates. The studies show that leptin can affect the cancer cells through numerous phenomena, e.g. inflammation, cell proliferation, suppression of apoptosis and angiogenesis. In this literature review we examined the role of leptin in the development of the individual cancers: breast cancer, colorectal cancer, prostate cancer, ovarian cancer, endometrial cancer and brain neoplasms: glioma and meningioma. However, leptin has very complicated mechanisms of action which require better understanding in certain types of cancer.

Induction of osteoclast-like cell formation by leptin-induced soluble intercellular adhesion molecule secreted from cancer cells

Background:

Leptin is considered a tumorigenic adipokine, suggested to promote tumorigenesis and progression in many cancers. On the other hand, intercellular adhesion molecule-1 (ICAM-1) shows altered expression in a variety of benign and malignant diseases. Histologically, ICAM-1 expression is reported as proportional to cancer stage and considered as a potential diagnosis biomarker. The altered expressions of ICAM-1 and its soluble form in malignant diseases have gained interests in recent years.

Material and methods:

The expression of ICAM-1 and its regulatory signaling were examined by Western blot or flow cytometry. The effect of soluble ICAM-1 on osteoclast formation was investigated by tartrate-resistance acid phosphatase staining of RAW cells and tumor-induced osteolysis in vivo.

Results:

In our study, we found that leptin enhanced soluble ICAM-1 production but not surface ICAM-1 expression in lung and breast cancer cells, and this effect was regulated through leptin receptor (ObR), while silencing ObR abrogated leptin-induced soluble ICAM-1 expression. In addition, we revealed that leptin administration provoked the JAK1/2, STAT3, FAK, ERK, and GSK3αβ signaling cascade, leading to the elevation of ICAM-1 expression. Moreover, soluble ICAM-1 secreted by leptin-stimulated cancer cells synergize with the receptor activator of nuclear factor kappa-B ligand (RANKL) in inducing osteoclast formation. Soluble ICAM also enhanced tumor-induced osteolysis in vivo.

Conclusion:

These findings suggest that soluble ICAM-1 produced under leptin treatment enhances osteoclast formation and is involved in tumor-induced osteolysis.

Leptin plays an important role in physiology in health and diseases. Leptin affects immune responses that may induce inflammation and carcinogenesis. Leptin is also considered as a tumorigenic adipokine suggested to promote tumorigenesis and progression in many cancers. On the other hand, intercellular adhesion molecule-1 (ICAM-1) shows altered expression in a variety of benign and malignant diseases. Histologically, ICAM-1 expression is reported to be proportional to cancer stage and considered as a potential diagnosis biomarker. It has been reported that soluble ICAM-1 allows tumor cells to escape from immune recognition and stimulates angiogenesis and tumor growth. The altered expressions of ICAM-1 and its soluble form in malignant diseases have gained interests in recent years. In our study, we found that leptin enhanced soluble ICAM-1 production but not surface ICAM-1 expression in lung and breast cancer cells, and this effect was regulated through leptin receptor (ObR), while silencing ObR abrogated leptin-induced soluble ICAM-1 expression. In addition, we revealed that leptin administration provoked the JAK1/2, STAT3, FAK, ERK, and GSK3αβ signaling cascade, leading to the elevation of ICAM-1 expression. Moreover, soluble ICAM-1 secreted by leptin-stimulated cancer cells synergize with receptor activator of nuclear factor-kappa B ligand in inducing osteoclast formation. Soluble ICAM also enhanced tumor-induced osteolysis in vivo. These findings suggest that soluble ICAM-1 produced under leptin treatment is possibly involved in lung and breast cancer bone metastasis.

Leptin-induced signaling pathways in cancer cell migration and invasion

BACKGROUND

Increasing evidence indicates that obesity is associated with tumor development and progression. Leptin is an adipocyte-related hormone with a key role in energy metabolism and whose circulating levels are elevated in obesity. The effect of leptin on cancer progression and metastasis and its underlying mechanisms are still unclear. Leptin can impact various steps in tumor metastasis, including epithelial-mesenchymal transition, cell adhesion to the extracellular matrix (ECM), and proteolysis of ECM components. To do so, leptin binds to its receptor (OB-Rb) to activate signaling pathways and downstream effectors that participate in tumor cell invasion as well as distant metastasis.

CONCLUSIONS

In this review, we describe metastasis steps in detail and characterize metastasis-related molecules activated by leptin, which may help to develop a roadmap that guides future work. In addition, we conclude that a profound understanding of the fundamental molecular processes that contribute to leptin-induced metastasis may pave the way for the development of new prognostic molecules and appropriate approaches to the treatment of obesity-related cancers.

Linking obesity-induced leptin-signaling pathways to common endocrine-related cancers in women

Obesity is related to many major diseases and cancers. Women have higher rates of obesity and obesity is linked to commonly occurring cancers in women. However, there is a lack of knowledge of the unique mechanism(s) involved in each type of cancer. The objective of this review is to highlight the need for novel experimental approaches and a better understanding of the common and unique pathways to resolve controversies regarding the role of obesity in cancer. In women, there is a link between hormones and obesity-associated genes in cancer development. Leptin is an obesity-associated gene that has been studied extensively in cancers; however, whether the defect is in the leptin gene or in its signaling pathways remains unclear. Both leptin and its receptor have been positively correlated with cancer progression in some endocrine-related cancers in women. This review offers an up-to-date and cohesive review of both upstream and downstream pathways of leptin signaling in cancer and a comprehensive picture of cancer pathogenesis in light of current evidence of leptin effects in several major types of cancer. This work is intended to aid in the design of better therapeutic strategies for obese/overweight women with cancer.

Leptin signaling axis specifically associates with clinical prognosis and is multifunctional in regulating cancer progression

Leptin is a peptide hormone that has been characterized as the ligand of leptin receptor (LEPR). The observation of leptin secretion and leptin receptor expression beyond the normal tissues suggests the potentially critical roles other than its physiological function. In addition to the original function in controlling appetite and energy expenditure, leptin-mediated signaling axis through leptin receptor is multifunctional which plays role in the regulation toward broad types of cancer. Emerging evidences has indicated leptin's function in promoting several processes which are relevant to cancer progression including cell proliferation, metastasis, angiogenesis and drug resistance. We relatively display leptin and leptin receptor expression levels in pan-cancer panel based on the transcriptome analysis via dataset The Cancer Genome Atlas (TCGA), and show the clinical association of the axis in predicting cancer prognosis. The results indicate the pathological impacts of this axis on many types of cancer. This review mainly focuses on leptin-mediated effects and its downstream signaling related to the progression of cancers, and displays the clinical significance of this axis including the impact on cancer patient survival.