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

Leptin Promotes the Proliferation and Neuronal Differentiation of Neural Stem Cells through the Cooperative Action of MAPK/ERK1/2, JAK2/STAT3 and PI3K/AKT Signaling Pathways

The potential of neural stem cells (NSCs) for neurological disorders the treatment has relied in large part upon identifying the NSCs fate decision. The hormone leptin has been reported to be a crucial regulator of brain development, able to influence the glial and neural development, yet, the underlying mechanism of leptin acting on NSCs' biological characteristics is still poorly understood. This study aims to investigate the role of leptin in the biological properties of NSCs. In this study, we investigate the possibility that leptin may regulate the NSCs' fate decision, which may promote the proliferation and neuronal differentiation of NSCs and thus act positively in neurological disorders. NSCs from the embryonic cerebral cortex were used in this study. We used CCK-8 assay, ki67 immunostaining, and FACS analysis to confirm that 25-100 ng/mL leptin promotes the proliferation of NSCs in a concentration-dependent pattern. This change was accompanied by the upregulation of p-AKT and p-ERK1/2, which are the classical downstream signaling pathways of leptin receptors b (LepRb). Inhibition of PI3K/AKT or MAPK/ERK signaling pathways both abolished the effect of leptin-induced proliferation. Moreover, leptin also enhanced the directed neuronal differentiation of NSCs. A blockade of the PI3K/AKT pathway reversed leptin-stimulated neurogenesis, while a blockade of JAK2/STAT3 had no effect on it. Taken together, our results support a role for leptin in regulating the fate of NSCs differentiation and promoting NSCs proliferation, which could be a promising approach for brain repair via regulating the biological characteristics of NSCs.

Role of Leptin and Adiponectin in Carcinogenesis

Hormones produced by adipocytes, leptin and adiponectin, are associated with the process of carcinogenesis. Both of these adipokines have well-proven oncologic potential and can affect many aspects of tumorigenesis, from initiation and primary tumor growth to metastatic progression. Involvement in the formation of cancer includes interactions with the tumor microenvironment and its components, such as tumor-associated macrophages, cancer-associated fibroblasts, extracellular matrix and matrix metalloproteinases. Furthermore, these adipokines participate in the epithelial-mesenchymal transition and connect to angiogenesis, which is critical for cancer invasiveness and cancer cell migration. In addition, an enormous amount of evidence has demonstrated that altered concentrations of these adipocyte-derived hormones and the expression of their receptors in tumors are associated with poor prognosis in various types of cancer. Therefore, leptin and adiponectin dysfunction play a prominent role in cancer and impact tumor invasion and metastasis in different ways. This review clearly and comprehensively summarizes the recent findings and presents the role of leptin and adiponectin in cancer initiation, promotion and progression, focusing on associations with the tumor microenvironment and its components as well as roles in the epithelial-mesenchymal transition and angiogenesis.

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.

TNF-α Antagonizes the Effect of Leptin on Insulin Secretion through FOXO1-Dependent Transcriptional Suppression of LepRb in INS-1 Cells

Proinflammatory cytokines play a causal role in the development of hyperinsulinemia and T2MD. FOXO1, a transcription factor which is known to enhance proinflammation, was recently shown to be involved in obesity-induced β cell dysfunction. However, molecular mechanisms for the association remained elusive. In this study, we first found that both leptin (10 nM) and TNF-α (20 ng/ml) significantly inhibited glucose-stimulated insulin secretion (GSIS) of INS-1E cells. When in combination, the GSIS function of INS-1E cells was significantly increased compared with that of the leptin alone treatment, indicating that TNF-α attenuated the inhibiting effect of leptin on GSIS of INS-1E cells. Similarly, we found that TNF-α has the same inhibitory effect on leptin in regulating insulin synthesis and secretion, and the survival and apoptosis of insulin cells. Further studies showed that TNF-α blocks leptin pathway by reducing the expression of leptin receptor (LepRb, also called OBRb) and inhibiting the activation of STAT3, a key molecule involved in the leptin signaling pathway in INS-1E cells. Besides, the downregulated expression of phosphorylated FOXO1 was found to be involved in the possible mechanism of TNF-α. Overexpression of constitutively active FOXO1 markedly aggravated the LepRb reduction by TNF-α treatment of INS-1E cells, and the endogenous FOXO1 knockdown abolished the effect of TNF-α on INS-1E cells. Furthermore, we have proved that FOXO1 could directly bind to the promoter of LepRb as a negative transcription regulator. Taken together, the results of this study reveal that TNF-α-induced LepRb downregulated in pancreatic β cells and demonstrate that transcriptional reduction of FOXO1 might be the primary mechanism underlying TNF-α promoting INS-1E leptin resistance and β cell dysfunction. Conclusions. Our current studies based on INS-1E cells in vitro indicate that the inflammatory factor TNF-α plays an important role in the development of INS-1E leptin resistance and glucose metabolism disorders, probably through FOXO1-induced transcription reduction of LepRb promoter in pancreatic β cells, and FOXO1 may be a novel target for treating β cell dysfunction in obesity-induced hyperinsulinemia and T2DM.

Multifarious Targets and Recent Developments in the Therapeutics for the Management of Bone Cancer Pain

Bone cancer pain (BCP) is a distinct pain state showing characteristics of both neuropathic and inflammatory pain. On average, almost 46% of cancer patients exhibit BCP with numbers flaring up to as high as 76% for terminally ill patients. Patients suffering from BCP experience a compromised quality of life, and the unavailability of effective therapeutics makes this a more devastating condition. In every individual cancer patient, the pain is driven by different mechanisms at different sites. The mechanisms behind the manifestation of BCP are very complex and poorly understood, which creates a substantial barrier to drug development. Nevertheless, some of the key mechanisms involved have been identified and are being explored further to develop targeted molecules. Developing a multitarget approach might be beneficial in this case as the underlying mechanism is not fixed and usually a number of these pathways are simultaneously dysregulated. In this review, we have discussed the role of recently identified novel modulators and mechanisms involved in the development of BCP. They include ion channels and receptors involved in sensing alteration of temperature and acidic microenvironment, immune system activation, sodium channels, endothelins, protease-activated receptors, neurotrophins, motor proteins mediated trafficking of glutamate receptor, and some bone-specific mechanisms. Apart from this, we have also discussed some of the novel approaches under preclinical and clinical development for the treatment of bone cancer pain.

Leptin attenuates hypoxia-induced apoptosis in human periodontal ligament cells via the reactive oxygen species-hypoxia-inducible factor-1α pathway

NEW FINDINGS

What is the central question of this study? Does leptin have an effect on hypoxia-induced apoptosis in human periodontal ligament cells (hPDLCs), and what is the potential underlying mechanism? What is the main finding and its importance? Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of hypoxia-inducible factor-1α and accumulation of reactive oxygen species (ROS). Leptin shows feedback inhibition on hypoxia-induced ROS-mediated apoptosis in hPDLCs, suggesting a new application of leptin for hypoxic damage in periodontal diseases.

ABSTRACT

Hypoxia-induced apoptosis of human periodontal ligament cells (hPDLCs) is an important contributor to the progression of various periodontal diseases. Although leptin has been shown to protect connective tissue cells against hypoxia-induced injury, whether it might do so by attenuating hypoxia-induced apoptosis in hPDLCs remains unclear. Here, using CoCl₂ treatment, we simulated hypoxic conditions in hPDLCs and explored whether apoptosis and reactive oxygen species (ROS) levels were related to hypoxia. After small interfering RNA (siRNA) inhibition of leptin and hypoxia-inducible factor-1α (HIF-1α), the levels of apoptosis, ROS and leptin expression were measured. We showed that in CoCl₂ -treated hPDLCs, significantly higher cell apoptosis rates and ROS accumulation were observed. Cobalt chloride also increased leptin and HIF-1α expression in hPDLCs. Further investigation of the pathway demonstrated that inhibition of ROS attenuated hypoxia-induced cell apoptosis and leptin expression, whereas siRNA inhibition of leptin aggravated hypoxia-induced cell apoptosis and ROS accumulation. Hypoxia induces cell apoptosis and leptin expression in hPDLCs through the induction of ROS and HIF-1α pathways, and leptin shows feedback inhibition on ROS-mediated apoptosis in hPDLCs. These findings suggest a new application of leptin for hypoxic damage in periodontal diseases.

Sauchinone inhibits hypoxia-induced epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma cells through the Wnt/β-catenin pathway

The hypoxic microenvironment is commonly found in various solid tumors including pancreatic ductal adenocarcinoma (PDAC). Saururus chinensis is a medicinal Chinese herb widely used because of documented anti-inflammatory and anti-angiogenic properties. Sauchinone is special active lignin extracted from S. chinensis and its biological functions have been extensively explored. Recent studies have found that sauchinone could affect tumor initiation, metastasis and progression of some cancers. However, the specific role of sauchinone in PDAC remains to be elucidated. The main aim of this study was to elucidate the involvement of sauchinone in the progression of PDAC under the hypoxic condition. The human PDAC cell lines PANC-1 and BxPC-3 were exposed to hypoxia and various concentrations of sauchinone. The CCK-8 assay was performed to detect cytotoxic effects of sauchinone on PDAC cells. The levels of vascular endothelial growth factor, hypoxia-inducible factor-1α, E-cadherin, N-cadherin, Wnt3a and β-catenin were examined by the western blot analysis. Wound healing and transwell assays were used to assess cell migration and invasion. The results showed that the migratory and invasive abilities of PDAC cells were enhanced after exposure to hypoxia and the expression of epithelial-mesenchymal transition markers was also significantly regulated by hypoxia. All these effects induced under the hypoxic condition were terminated by sauchinone treatment. In addition, sauchinone suppressed hypoxia-induced activation of the Wnt/β-catenin signaling pathway. Our study provided important insight into understanding the mechanisms of the anti-cancer effect of sauchinone. Taken together, we suggested that sauchinone may be considered a new therapeutic agent for PDAC treatment.

VHH212 nanobody targeting the hypoxia-inducible factor 1α suppresses angiogenesis and potentiates gemcitabine therapy in pancreatic cancer in vivo

OBJECTIVE

We aimed to develop a novel anti-HIF-1α intrabody to decrease gemcitabine resistance in pancreatic cancer patients.

METHODS

Surface plasmon resonance and glutathione S-transferase pull-down assays were conducted to identify the binding affinity and specificity of anti-HIF-1α VHH212 [a single-domain antibody (nanobody)]. Molecular dynamics simulation was used to determine the protein-protein interactions between hypoxia-inducible factor-1α (HIF-1α) and VHH212. The real-time polymerase chain reaction (PCR) and Western blot analyses were performed to identify the expressions of HIF-1α and VEGF-A in pancreatic ductal adenocarcinoma cell lines. The efficiency of the VHH212 nanobody in inhibiting the HIF-1 signaling pathway was measured using a dual-luciferase reporter assay. Finally, a PANC-1 xenograft model was developed to evaluate the anti-tumor efficiency of combined treatment. Immunohistochemistry analysis was conducted to detect the expressions of HIF-1α and VEGF-A in tumor tissues.

RESULTS

VHH212 was stably expressed in tumor cells with low cytotoxicity, high affinity, specific subcellular localization, and neutralization of HIF-1α in the cytoplasm or nucleus. The binding affinity between VHH212 and the HIF-1α PAS-B domain was 42.7 nM. Intrabody competitive inhibition of the HIF-1α heterodimer with an aryl hydrocarbon receptor nuclear translocator was used to inhibit the HIF-1/VEGF pathway in vitro. Compared with single agent gemcitabine, co-treatment with gemcitabine and a VHH212-encoding adenovirus significantly suppressed tumor growth in the xenograft model with 80.44% tumor inhibition.

CONCLUSIONS

We developed an anti-HIF-1α nanobody and showed the function of VHH212 in a preclinical murine model of PANC-1 pancreatic cancer. The combination of VHH212 and gemcitabine significantly inhibited tumor development. These results suggested that combined use of anti-HIF-1α nanobodies with first-line treatment may in the future be an effective treatment for pancreatic cancer.

The hypoxia response and nutritional peptides

Hypoxia controls metabolism at several levels, e.g., via mitochondrial ATP production, glucose uptake and glycolysis. Hence it is likely that hypoxia also affects the action and/or production of many peptide hormones linked to food intake and appetite control. Many of those are produced in the gastrointestinal tract, endocrine pancreas, adipose tissue, and selective areas in the brain which modulate and concert their actions. However, the complexity of the hypoxia response and the links to peptides/hormones involved in food intake and appetite control in the different organs are not well known. This review summarizes the role of the hypoxia response and its effects on major peptides linked to appetite regulation, nutrition and metabolism.

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.

Pancreatic Tumorigenesis: Oncogenic KRAS and the Vulnerability of the Pancreas to Obesity

Simple Summary

Pancreatic cancer is a devastating disease with a poor survival rate, and oncogenic mutant KRAS is a major driver of its initiation and progression; however, effective strategies/drugs targeting major forms of mutant KRAS have not been forthcoming. Of note, obesity is known to worsen mutant KRAS-mediated pathologies, leading to PDAC with high penetrance; however, the mechanistic link between obesity and pancreatic cancer remains elusive. The recent discovery of FGF21 as an anti-obesity and anti-inflammation factor and as a downstream target of KRAS has shed new light on the problem.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies and KRAS (Kirsten rat sarcoma 2 viral oncogene homolog) mutations have been considered a critical driver of PDAC initiation and progression. However, the effects of mutant KRAS alone do not recapitulate the full spectrum of pancreatic pathologies associated with PDAC development in adults. Historically, mutant KRAS was regarded as constitutively active; however, recent studies have shown that endogenous levels of mutant KRAS are not constitutively fully active and its activity is still subject to up-regulation by upstream stimuli. Obesity is a metabolic disease that induces a chronic, low-grade inflammation called meta-inflammation and has long been recognized clinically as a major modifiable risk factor for pancreatic cancer. It has been shown in different animal models that obesogenic high-fat diet (HFD) and pancreatic inflammation promote the rapid development of mutant KRAS-mediated PDAC with high penetrance. However, it is not clear why the pancreas with endogenous levels of mutant KRAS is vulnerable to chronic HFD and inflammatory challenges. Recently, the discovery of fibroblast growth factor 21 (FGF21) as a novel anti-obesity and anti-inflammatory factor and as a downstream target of mutant KRAS has shed new light on this problem. This review is intended to provide an update on our knowledge of the vulnerability of the pancreas to KRAS-mediated invasive PDAC in the context of challenges engendered by obesity and associated inflammation.

The Role of Dysfunctional Adipose Tissue in Pancreatic Cancer: A Molecular Perspective

Pancreatic cancer (PC) is a lethal malignancy with rising incidence and limited therapeutic options. Obesity is a well-established risk factor for PC development. Moreover, it negatively affects outcome in PC patients. Excessive fat accumulation in obese, over- and normal-weight individuals induces metabolic and inflammatory changes of adipose tissue microenvironment leading to a dysfunctional adipose “organ”. This may drive the association between abnormal fat accumulation and pancreatic cancer. In this review, we describe several molecular mechanisms that underpin this association at both local and systemic levels. We focus on the role of adipose tissue-derived circulating factors including adipokines, hormones and pro-inflammatory cytokines, as well as on the impact of the local adipose tissue in promoting PC. A discussion on potential therapeutic interventions, interfering with pro-tumorigenic effects of dysfunctional adipose tissue in PC, is included. Considering the raise of global obesity, research efforts to uncover the molecular basis of the relationship between pancreatic cancer and adipose tissue dysfunction may provide novel insights for the prevention of this deadly disease. In addition, these efforts may uncover novel targets for personalized interventional strategies aimed at improving the currently unsatisfactory PC therapeutic options.

RETRACTED: HIF-1α mediates tumor-nerve interactions through the up-regulation of GM-CSF in pancreatic ductal adenocarcinoma

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Authors. Following concerns raised in the public domain, the authors contacted the journal to request the retraction of the article. Sections of panels from various figures appear similar to each other, particularly panels from Figures 3G and 5B, 3G and 5F, 3F, S4D, S5D, S5C and S10C, as well as S10E.

Knockdown of hypoxia-inducible factor-1 alpha by tumor targeted delivery of CRISPR/Cas9 system suppressed the metastasis of pancreatic cancer

The hypoxic tumor microenvironment of pancreatic cancer contributes to the progression and metastasis of tumor cells. Downregulation of hypoxia-inducible factor-1α (HIF-1α) with CRISPR/Cas9 is a promising approach to modulate tumor microenvironment and inhibit tumor metastasis. However, the in vivo delivery of CRISPR/Cas9 system remains a challenge. In the present manuscript, a tumor targeted lipid-based CRISPR/Cas9 delivery system was developed to suppress HIF-1α. Plasmids encoding Cas9 and HIF-1α-targeting sgRNA were successfully constructed and coencapsulated in R8-dGR peptide modified cationic liposome with PTX. R8-dGR-Lip exhibited enhanced BxPC-3 cell targeting and deep penetration into tumor spheroids. R8-dGR-Lip/PTX/pHIF-1α successfully downregulated HIF-1α and its downstream molecules VEGF and MMP-9, leading to enhanced antimetastatic effects. Besides, the blockade of HIF-1α also promoted the cytotoxicity of PTX on BxPC-3 cell lines. Compared with pegylated liposomes, R8-dGR-Lip enhanced the distribution in tumor tissues. The targeted delivery of CRISPR/Cas9-HIF-1α system and PTX significantly inhibited tumor growth. More importantly, inhibition of HIF-1α suppressed the metastasis of pancreatic cancer and prolonged survival time. Since CRISPR/Cas 9-HIF-1α hardly affected HIF-1α expression in normal hepatic cells, the designed R8-dGR-Lip/PTX/pHIF-1α did not induce severe toxicity in vivo. This strategy broadened the in vivo application of CRISPR/Cas9 system. Downregulation of HIF-1α may be a feasible approach for antimetastatic therapy.

LOX and ACSL5 as potential relapse markers for pancreatic cancer patients

Pancreatic cancer is one of the most malignant diseases and has a poor prognosis. The screening and validation of biomarkers with predictive value for prognosis and treatment efficacy are important. To identify potential prognostic markers of pancreatic cancer patients, we conducted a study that included 99 pancreatic cancer patients. Three patients with PFS>18 months were enrolled in the treat group, and three patients with PFS<12 months were enrolled in the control group. Differentially expressed genes (DEGs) between these two groups were analyzed by whole-genome expression microarray. A total of 178 DEGs were identified, including 110 up-regulated and 68 down-regulated genes. Next, 24 candidate genes were selected for validation by qPCR based on fold change and previous studies. The results showed that the mRNA levels of four candidate genes, including ACSL5, SLC44A4, LOX, and TOX3, were correlated with PFS. Immunohistochemical staining was performed to validate the protein expression levels of these four markers. The results showed that patients with LOX ^high, ACSL5 ^low and TOX3 ^low expression had a significantly shorter PFS than those with LOX ^low, ACSL5 ^high and TOX3 ^high expression. Multivariable analysis revealed differentiation, tumor stage, LOX expression, and ACSL5 expression were independent prognostic factors for PFS. Then, we use the TCGA database to explore the underlying mechanism of LOX influence pancreatic cancer progression. Protein-protein interaction network of ACSL5 was established by STRING to uncover the potential regulation mechanism. Our findings reveal that LOX and ACSL5 are potential prognostic markers for the prognosis of pancreatic cancer patients.

Pancreatic cancer associated with obesity and diabetes: an alternative approach for its targeting

BACKGROUND

Pancreatic cancer (PC) is among foremost causes of cancer related deaths worldwide due to generic symptoms, lack of effective screening strategies and resistance to chemo- and radiotherapies. The risk factors associated with PC include several metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus (T2DM). Studies have shown that obesity and T2DM are associated with PC pathogenesis; however, their role in PC initiation and development remains obscure.

MAIN BODY

Several biochemical and physiological factors associated with obesity and/or T2DM including adipokines, inflammatory mediators, and altered microbiome are involved in PC progression and metastasis albeit by different molecular mechanisms. Deep understanding of these factors and causal relationship between factors and altered signaling pathways will facilitate deconvolution of disease complexity as well as lead to development of novel therapies. In the present review, we focuses on the interplay between adipocytokines, gut microbiota, adrenomedullin, hyaluronan, vanin and matrix metalloproteinase affected by metabolic alteration and pancreatic tumor progression.

CONCLUSIONS

Metabolic diseases, such as obesity and T2DM, contribute PC development through altered metabolic pathways. Delineating key players in oncogenic development in pancreas due to metabolic disorder could be a beneficial strategy to combat cancers associated with metabolic diseases in particular, PC.

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.

Inflammatory interferon activates HIF-1α-mediated epithelial-to-mesenchymal transition via PI3K/AKT/mTOR pathway

BACKGROUND

Tumor microenvironments (TMEs) activate various axes/pathways, predominantly inflammatory and hypoxic responses, impact tumorigenesis, metastasis and therapeutic resistance significantly. Although molecular pathways of individual TME are extensively studied, evidence showing interaction and crosstalk between hypoxia and inflammation remain unclear. Thus, we examined whether interferon (IFN) could modulate both inflammatory and hypoxic responses under normoxia and its relation with cancer development.

METHODS

IFN was used to induce inflammation response and HIF-1α expression in various cancer cell lines. Corresponding signaling pathways were then analyzed by a combination of pharmacological inhibitors, immunoblotting, GST-Raf pull-down assays, dominant-negative and short-hairpin RNA-mediated knockdown approaches. Specifically, roles of functional HIF-1α in the IFN-induced epithelial-mesenchymal transition (EMT) and other tumorigenic propensities were examined by knockdown, pharmacological inhibition, luciferase reporter, clonogenic, anchorage-independent growth, wound-healing, vasculogenic mimicry, invasion and sphere-formation assays as well as cellular morphology observation.

RESULTS

We showed for the first time that IFN induced functional HIF-1α expression in a time- and dose- dependent manner in various cancer cell lines under both hypoxic and normoxic conditions, and then leading to an activated HIF-1α pathway in an IFN-mediated pro-inflammatory TME. IFN regulates anti-apoptosis activity, cellular metastasis, EMT and vasculogenic mimicry by a novel mechanism through mainly the activation of PI3K/AKT/mTOR axis. Subsequently, pharmacological and genetic modulations of HIF-1α, JAK, PI3K/AKT/mTOR or p38 pathways efficiently abrogate above IFN-induced tumorigenic propensities. Moreover, HIF-1α is required for the IFN-induced invasiveness, tumorigenesis and vasculogenic mimicry. Further supports for the HIF-1α-dependent tumorigenesis were obtained from results of xenograft mouse model and sphere-formation assay.

CONCLUSIONS

Our mechanistic study showed an induction of HIF-1α and EMT ability in an IFN-mediated inflammatory TME and thus demonstrating a novel interaction between inflammatory and hypoxic TMEs. Moreover, targeting HIF-1α may be a potential target for inhibiting tumor tumorigenesis and EMT by decreasing cancer cells wound healing and anchorage-independent colony growth. Our results also lead to rationale guidance for developing new therapeutic strategies to prevent relapse via targeting TME-providing IFN signaling and HIF-1α programming.

Gallic acid modulates phenotypic behavior and gene expression in oral squamous cell carcinoma cells by interfering with leptin pathway

Gallic acid is a polyphenolic compost appointed to interfere with neoplastic cells behavior. Evidence suggests an important role of leptin in carcinogenesis pathways, inducing a proliferative phenotype. We investigated the potential of gallic acid to modulate leptin-induced cell proliferation and migration of oral squamous cell carcinoma cell lines. The gallic acid effect on leptin secretion by oral squamous cell carcinoma cells, as well as the underlying molecular mechanisms, was also assessed. For this, we performed proliferation, migration, immunocytochemical and qPCR assays. The expression levels of cell migration-related genes (MMP2, MMP9, Col1A1, and E-cadherin), angiogenesis (HIF-1α, mir210), leptin signaling (LepR, p44/42 MAPK), apoptosis (casp-3), and secreted leptin levels by oral squamous cell carcinoma cells were also measured. Gallic acid decreased proliferation and migration of leptin-treated oral squamous cell carcinoma cells, and reduced mRNA expression of MMP2, MMP9, Col1A1, mir210, but did not change HIF-1α. Gallic acid decreased levels of leptin secreted by oral squamous cell carcinoma cells, accordingly with downregulation of p44/42 MAPK expression. Thus, gallic acid appears to break down neoplastic phenotype of oral squamous cell carcinoma cells by interfering with leptin pathway.

The potential role of leptin in tumor invasion and metastasis

The adipocyte-released hormone-like cytokine/adipokine leptin behaves differently in obesity compared to its functions in the normal healthy state. In obese individuals, elevated leptin levels act as a pro-inflammatory adipokine and are associated with certain types of cancers. Further, a growing body of evidence suggests that higher circulating leptin concentrations and/or elevated expression of leptin receptors (Ob-R) in tumors may be poor prognostic factors. Although the underlying pathological mechanisms of leptin's association with poor prognosis are not clear, leptin can impact the tumor microenvironment in several ways. For example, leptin is associated with a number of biological components that could lead to tumor cell invasion and distant metastasis. This includes interactions with carcinoma-associated fibroblasts, tumor promoting effects of infiltrating macrophages, activation of matrix metalloproteinases, transforming growth factor-β signaling, etc. Recent studies also have shown that leptin plays a role in the epithelial-mesenchymal transition, an important phenomenon for cancer cell migration and/or metastasis. Furthermore, leptin's potentiating effects on insulin-like growth factor-I, epidermal growth factor receptor and HER2/neu have been reported. Regarding unfavorable prognosis, leptin has been shown to influence both adenocarcinomas and squamous cell carcinomas. Features of poor prognosis such as tumor invasion, lymph node involvement and distant metastasis have been recorded in several cancer types with higher levels of leptin and/or Ob-R. This review will describe the current scenario in a precise manner. In general, obesity indicates poor prognosis in cancer patients.

Leptin acts on neoplastic behavior and expression levels of genes related to hypoxia, angiogenesis, and invasiveness in oral squamous cell carcinoma

Leptin, one of the main hormones controlling energy homeostasis, has been associated with different cancer types. In oral cancer, its effect is not well understood. We investigated, through in vitro and in vivo assays, whether leptin can affect the neoplastic behavior of oral squamous cell carcinoma. Expression of genes possibly linked to the leptin pathway was assessed in leptin-treated oral squamous cell carcinoma cells and also in tissue samples of oral squamous cell carcinoma and oral mucosa, including leptin, leptin receptor, hypoxia-inducible factor 1-alpha, E-cadherin, matrix metalloproteinase-2, matrix metalloproteinase-9, Col1A1, Ki67, and mir-210. Leptin treatment favored higher rates of cell proliferation and migration, and reduced apoptosis. Accordingly, leptin-treated oral squamous cell carcinoma cells show decreased messenger RNA caspase-3 expression, and increased levels of E-cadherin, Col1A1, matrix metalloproteinase-2, matrix metalloproteinase-9, and mir-210. In tissue samples, hypoxia-inducible factor 1-alpha messenger RNA and protein expression of leptin and leptin receptor were high in oral squamous cell carcinoma cases. Serum leptin levels were increased in first clinical stages of the disease. In animal model, oral squamous cell carcinoma-induced mice show higher leptin receptor expression, and serum leptin level was increased in dysplasia group. Our findings suggest that leptin seems to exert an effect on oral squamous cell carcinoma cells behavior and also on molecular markers related to cell proliferation, migration, and tumor angiogenesis.

Leptin signaling and cancer chemoresistance: Perspectives

Obesity is a major health problem and currently is endemic around the world. Obesity is a risk factor for several different types of cancer, significantly promoting cancer incidence, progression, poor prognosis and resistance to anti-cancer therapies. The study of this resistance is critical as development of chemoresistance is a serious drawback for the successful and effective drug-based treatments of cancer. There is increasing evidence that augmented adiposity can impact on chemotherapeutic treatment of cancer and the development of resistance to these treatments, particularly through one of its signature mediators, the adipokine leptin. Leptin is a pro-inflammatory, pro-angiogenic and pro-tumorigenic adipokine that has been implicated in many cancers promoting processes such as angiogenesis, metastasis, tumorigenesis and survival/resistance to apoptosis. Several possible mechanisms that could potentially be developed by cancer cells to elicit drug resistance have been suggested in the literature. Here, we summarize and discuss the current state of the literature on the role of obesity and leptin on chemoresistance, particularly as it relates to breast and pancreatic cancers. We focus on the role of leptin and its significance in possibly driving these proposed chemoresistance mechanisms, and examine its effects on cancer cell survival signals and expansion of the cancer stem cell sub-populations.

Leptin sustains spontaneous remyelination in the adult central nervous system

Demyelination is a common feature of many central nervous system (CNS) diseases and is associated with neurological impairment. Demyelinated axons are spontaneously remyelinated depending on oligodendrocyte development, which mainly involves molecules expressed in the CNS environment. In this study, we found that leptin, a peripheral hormone secreted from adipocytes, promoted the proliferation of oligodendrocyte precursor cells (OPCs). Leptin increased the OPC proliferation via in vitro phosphorylation of extracellular signal regulated kinase (ERK); whereas leptin neutralization inhibited OPC proliferation and remyelination in a mouse model of toxin-induced demyelination. The OPC-specific leptin receptor long isoform (LepRb) deletion in mice inhibited both OPC proliferation and remyelination in the response to demyelination. Intrathecal leptin administration increased OPC proliferation. These results demonstrated a novel molecular mechanism by which leptin sustained OPC proliferation and remyelination in a pathological CNS.

Hypoxia Promotes Gastric Cancer Malignancy Partly through the HIF-1α Dependent Transcriptional Activation of the Long Non-coding RNA GAPLINC

Hypoxia-inducible factor (HIF) activates the transcription of genes involved in cancer progression. Recently, HIF was reported to regulate the transcription of non-coding RNAs. Here, we show that the transcription of a long non-coding RNA (lncRNA), Gastric Adenocarcinoma Associated, Positive CD44 Regulator, Long Intergenic Non-Coding RNA (GAPLINC), is directly activated by HIF-1α in gastric cancer (GC). GAPLINC was overexpressed in GC tissues and promoted tumor migration and invasive behavior. GAPLINC overexpression was associated with poor prognosis in GC patients. Luciferase reporter assays and chromatin immunoprecipitation assays confirmed that HIF-1α binds to the promoter region of GAPLINC and activates its transcription. GAPLINC knockdown inhibited hypoxia-induced tumor proliferation in vivo. Taken together, our results identified a novel role for HIF transcriptional pathways in GC tumorigenesis mediated by the regulation of the lncRNA GAPLINC, and suggest GAPLINC as a novel therapeutic target for reversing chemoradioresistance and prolonging survival.

MiR-186 inhibited aerobic glycolysis in gastric cancer via HIF-1α regulation

Deregulation of microRNAs in human malignancies has been well documented, among which microRNA-186 (miR-186) has an antiproliferative role in some carcinomas. Here we demonstrate that low expression of miR-186 facilitates aerobic glycolysis in gastric cancer. MiR-186 suppresses cell proliferation induced by hypoxia inducible factor 1 alpha (HIF-1α) in gastric cancer cell lines MKN45 and SGC7901. Cellular glycolysis, including cellular glucose uptake, lactate, ATP/ADP and NAD+/NADH ratios, are also inhibited by miR-186. The negative regulation of miR-186 on HIF-1α effects its downstream targets, including programmed death ligand 1 and two glycolytic key enzymes, hexokinase 2 and platelet-type phosphofructokinase. The antioncogenic effects of miR-186 are proved by in vivo xenograft tumor experiment. The results demonstrate that the miR-186/HIF-1α axis has an antioncogenic role in gastric cancer.

Leptin signaling enhances cell invasion and promotes the metastasis of human pancreatic cancer via increasing MMP-13 production

Emerging evidence has suggested that leptin, an adipokine related to energy homeostasis, plays a role in cancer growth and metastasis. However, its impact on pancreatic cancer is rarely studied. In this study, we found that leptin's functional receptor Ob-Rb was expressed in pancreatic cancer cell lines. Treatment with leptin enhanced the migration and invasion of pancreatic cancer cells but did not affect the proliferation of human pancreatic cancer cells. Leptin up-regulated the expression of matrix metalloproteinase-13 (MMP-13) via the JAK2/STAT3 signaling pathway. The overexpression of leptin was shown to significantly promote tumor growth and lymph node metastasis in a subcutaneous model and an orthotopic model of human pancreatic cancer, respectively. Furthermore, in human pancreatic cancer tissues, the expression of Ob-Rb was positively correlated with the MMP-13 level. The increased expression of either Ob-Rb or MMP-13 was significantly associated with lymph node metastasis and tended to be associated with the TNM stage in patients with pancreatic cancer. Our findings suggest that leptin enhances the invasion of pancreatic cancer through the increase in MMP-13 production, and targeting the leptin/MMP-13 axis could be an attractive therapeutic strategy for pancreatic cancer.

Single nucleotide polymorphism in the microRNA-199a binding site of HIF1A gene is associated with pancreatic ductal adenocarcinoma risk and worse clinical outcomes

Hypoxia-inducible factor-1 alpha (HIF-1α) is over-expressed in many cancers including pancreatic ductal adenocarcinoma (PDAC) and correlated with poor prognosis. We aim to determine the effect of germline genetic variants on the regulation of the homeostasis of the miRNA-gene regulatory loop in HIF1A gene and PDAC risk. HIF1A rs2057482 single nucleotide polymorphism (SNP) was genotyped in 410 PDAC cases and 490 healthy controls. The CC genotype SNP HIF1A is significantly correlated with PDAC risk (OR = 1.719, 95% CI: 1.293-2.286) and shorter overall survival (OS, P<0.0001) compared with the CT/TT alleles group. The C/T variants of rs2057482, a SNP located near the miR-199a binding site in HIF1A, could lead to differential regulation of HIF1A by miR-199a. Specifically, the C allele of rs2057482 weakened miR-199a-induced repression of HIF-1α expression on both mRNA and protein levels. In the PDAC tissue, individuals with the rs2057482-CC genotype expressed significantly higher levels of HIF-1α protein than those with the rs2057482-CT/TT genotype (P<0.0001). Both the CC genotype of SNP HIF1A and increased HIF-1α expression are significantly associated with shorter OS of patients with PDAC. After adjusted by TNM staging, differentiation grade, and the levels of CA19-9, both SNP HIF1A and HIF-1α expression retained highly significance on OS (P<0.0001). Taken together, our study demonstrates that host genetic variants could disturb the regulation of the miR-199a/HIF1A regulatory loop and alter PDAC risk and poor prognosis. In conclusion, the rs2057482-CC genotype increases the susceptibility to PDAC and associated with cancer progression.

Peroxisome proliferator activated receptors at the crossroad of obesity, diabetes, and pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth cause of cancer death with an overall survival of 5% at five years. The development of PDAC is characteristically associated to the accumulation of distinctive genetic mutations and is preceded by the exposure to several risk factors. Epidemiology has demonstrated that PDAC risk factors may be non-modifiable risks (sex, age, presence of genetic mutations, ethnicity) and modifiable and co-morbidity factors related to the specific habits and lifestyle. Recently it has become evident that obesity and diabetes are two important modifiable risk factors for PDAC. Obesity and diabetes are complex systemic and intertwined diseases and, over the years, experimental evidence indicate that insulin-resistance, alteration of adipokines, especially leptin and adiponectin, oxidative stress and inflammation may play a role in PDAC. Peroxisome proliferator activated receptor-γ (PPARγ) is a nuclear receptor transcription factor that is implicated in the regulation of metabolism, differentiation and inflammation. PPARγ is a key regulator of adipocytes differentiation, regulates insulin and adipokines production and secretion, may modulate inflammation, and it is implicated in PDAC. PPARγ agonists are used in the treatment of diabetes and oxidative stress-associated diseases and have been evaluated for the treatment of PDAC. PPARγ is at the cross-road of diabetes, obesity, and PDAC and it is an interesting target to pharmacologically prevent PDAC in obese and diabetic patients.

Influential Factors and Synergies for Radiation-Gene Therapy on Cancer

Radiation-gene therapy, a dual anticancer strategy of radiation therapy and gene therapy through connecting radiation-inducible regulatory sequence to therapeutic gene, leading to the gene being induced to express by radiation while radiotherapy is performed and finally resulting in a double synergistic antitumor effect of radiation and gene, has become one of hotspots in the field of cancer treatment in recent years. But under routine dose of radiation, especially in the hypoxia environment of solid tumor, it is difficult for this therapy to achieve desired effect because of low activity of radiation-inducible regulatory elements, low level and transient expression of target gene induced by radiation, inferior target specificity and poor biosecurity, and so on. Based on the problems existing in radiation-gene therapy, many efforts have been devoted to the curative effect improvement of radiation-gene therapy by various means to increase radiation sensitivity or enhance target gene expression and the expression's controllability. Among these synergistic techniques, gene circuit, hypoxic sensitization, and optimization of radiation-induced sequence exhibit a good application potential. This review provides the main influential factors to radiation-gene therapy on cancer and the synergistic techniques to improve the anticancer effect of radiation-gene therapy.

PRL-3 promotes gastric cancer migration and invasion through a NF-κB-HIF-1α-miR-210 axis

Phosphatase of regenerating liver-3 (PRL-3) has been implicated in controlling cancer cell invasiveness. Deregulated expression of PRL-3 is involved in cancer progression and predicts poor overall survival. Recent studies have revealed critical roles for microRNAs in various cellular processes, including tumorigenic development. In this study, we aimed to explore the linkage between PRL-3 and microRNAs in gastric cancer. We found that PRL-3 transcript levels were positively correlated with miR-210 levels in gastric cancer tissues. In gastric cancer cells, PRL-3 upregulated miR-210 expression in a HIF-1α-dependent fashion under normoxia and hypoxia. In addition, PRL-3 activated NF-κB signaling and promoted HIF-1α expression through modulating phosphorylation of p65. NF-κB signaling, HIF-1α, and miR-210 partially contributed to PRL-3-induced migration and invasion. Furthermore, the levels of PRL-3, HIF-1α, and miR-210 transcripts inversely affected the overall survival of gastric cancer patients. Our work identified the existence of a PRL-3-NF-κB-HIF-1α-miR-210 axis, thus providing new insight into the role of PRL-3 in promoting gastric cancer invasiveness.

KEY MESSAGE

PRL-3 regulates microRNA in gastric cancer. PRL-3 elevates hsa-miR-210 by upregulating HIF-1α. PRL-3 activates a NF-κB-HIF-1α-miR-210 axis by enhancing the phosphorylation of p65. PRL-3 promotes cell migration and invasion via the NF-κB-HIF-1α-miR-210 axis. High levels of PRL-3 and miR-210 are related with poor OS in gastric cancer.

Cancer as a Proinflammatory Environment: Metastasis and Cachexia

The development of the syndrome of cancer cachexia and that of metastasis are related with a poor prognostic for cancer patients. They are considered multifactorial processes associated with a proinflammatory environment, to which tumour microenvironment and other tissues from the tumour bearing individuals contribute. The aim of the present review is to address the role of ghrelin, myostatin, leptin, HIF, IL-6, TNF-α, and ANGPTL-4 in the regulation of energy balance, tumour development, and tumoural cell invasion. Hypoxia induced factor plays a prominent role in tumour macro- and microenvironment, by modulating the release of proinflammatory cytokines.

HIF-1 is a critical target of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal digestive tract malignancies. Hypoxia-inducible factor (HIF-1) is over-expressed in pancreatic cancer and associated with poor prognosis. During the past several years, we focused on identifying the function of HIF-1 and the antitumor effect of HIF-1 inhibitors on PDAC, especially in regards to immunogenic cell death.

Implication of Leptin-Signaling Proteins and Epstein-Barr Virus in Gastric Carcinomas

We investigated the clinicopathological implications of leptin-signaling proteins and Epstein-Barr virus (EBV)-infection status in gastric carcinomas. Immunohistochemistry for leptin signalling-related proteins (leptin, leptin-receptor, pSTAT3, ERK, pAkt, mTOR and HIF-1 alpha), and in situ hybridization for EBV-encoded small RNAs was performed in 343 cases of gastric carcinomas. The siRNA against leptin-receptor was transfected into three stomach cancer cell lines, and western blot for caspase 3 was performed. The TNM stage was a prognostic factor in all 343 patients, and was negatively correlated with expression of leptin, pSTAT3, ERK, pAkt, mTOR and HIF-1 alpha (P < 0.05). Leptin-receptor expression was correlated with poor survival in 207 patients of the advanced gastric cancer (AGC) subgroup, 139 of the Lauren diffuse group, and in 160 patients with lymph node metastasis (P < 0.05, respectively). Additionally, in stomach cancer cells, cleaved caspase 3 level increased by leptin-receptor inhibition, that is, apoptosis increased. Interestingly, EBV-positive AGC (n = 29) tended to show better survival of patients than EBV-negative AGC (n = 178) (P = 0.06). pAkt expression was related with a good survival of 32 patients (9%) in the EBV-positive subgroup, but was not an independent prognostic factor. Among, leptin signaling-related proteins, expressions of leptin-receptor and mTOR were different between EBV-positive subgroup and EBV-negative subgroup (P < 0.05, respectively). In conclusion, leptin-signaling proteins and EBV status show different significance on patient survival, according to subsets of gastric carcinomas. The leptin-receptor may predict poor patient prognosis in the AGC, Lauren diffuse and lymph node metastasis subgroups, while EBV-positive status can show a good prognosis in the AGC. Each leptin signaling-related protein may be differently involved in carcinogenesis of EBV-negative and EBV-positive subsets.

New targeted therapies in pancreatic cancer

Patients with pancreatic cancer have a poor prognosis with a median survival of 4-6 mo and a 5-year survival of less than 5%. Despite therapy with gemcitabine, patient survival does not exceed 6 mo, likely due to natural resistance to gemcitabine. Therefore, it is hoped that more favorable results can be obtained by using guided immunotherapy against molecular targets. This review summarizes the new leading targeted therapies in pancreatic cancers, focusing on passive and specific immunotherapies. Passive immunotherapy may have a role for treatment in combination with radiochemotherapy, which otherwise destroys the immune system along with tumor cells. It includes mainly therapies targeting against kinases, including epidermal growth factor receptor, Ras/Raf/mitogen-activated protein kinase cascade, human epidermal growth factor receptor 2, insulin growth factor-1 receptor, phosphoinositide 3-kinase/Akt/mTOR and hepatocyte growth factor receptor. Therapies against DNA repair genes, histone deacetylases, microRNA, and pancreatic tumor tissue stromal elements (stromal extracellular matric and stromal pathways) are also discussed. Specific immunotherapies, such as vaccines (whole cell recombinant, peptide, and dendritic cell vaccines), adoptive cell therapy and immunotherapy targeting tumor stem cells, have the role of activating antitumor immune responses. In the future, treatments will likely include personalized medicine, tailored for numerous molecular therapeutic targets of multiple pathogenetic pathways.

Possible role of vitamin D3 on the adipocyte/fibroblast trans-differentiation mediated by pancreas cancer

In pancreatic tumors, white adipose tissue and metabolic disorders related to adipocytes, are recently reviewed as important co-factors in pancreas pathology. Cell differentiation in pancreatic cancer might involve therefore adipose tissue and factors released by adipocytes should play a fundamental role both in cancer onset and in its progression. Among these molecules, a great interest has been devoted quite recently to the hormonal role exerted by vitamin D3 in pancreatic cancer, particularly its active 1,25 dihydroxylated form. Despite the wide bulk of evidence reporting the chemopreventive role of vitamin D, the mechanism by which active vitamin D3 is able to counteract cancer progression and malignancy is yet far to be elucidated.