Overexpression of leptin receptor in human glioblastoma: Correlation with vasculogenic mimicry and poor prognosis

Leptin Promotes Vasculogenic Mimicry in Breast Cancer Cells by Regulating Aquaporin-1

Leptin is an obesity-related hormone that plays an important role in breast cancer progression. Vasculogenic mimicry (VM) refers to the formation of vascular channels lined by tumor cells. This study aimed to investigate the relationship between leptin and VM in human breast cancer cells. VM was measured by a 3D culture assay. Signal transducers and activators of transcription 3 (STAT3) signaling, aquaporin-1 (AQP1), and the expression of VM-related proteins, including vascular endothelial cadherin (VE-cadherin), twist, matrix metalloproteinase-2 (MMP-2), and laminin subunit 5 gamma-2 (LAMC2), were examined by Western blot. AQP1 mRNA was analyzed by a reverse transcriptase-polymerase chain reaction (RT-PCR). Leptin increased VM and upregulated phospho-STAT3, VE-cadherin, twist, MMP-2, and LAMC2. These effects were inhibited by the leptin receptor-blocking peptide, Ob-R BP, and the STAT3 inhibitor, AG490. A positive correlation between leptin and AQP1 mRNA was observed and was confirmed by RT-PCR. Leptin upregulated AQP1 expression, which was blocked by Ob-R BP and AG490. AQP1 overexpression increased VM and the expression of VM-related proteins. AQP1 silencing inhibited leptin-induced VM and the expression of VM-related proteins. Thus, these results showed that leptin facilitates VM in breast cancer cells via the Ob-R/STAT3 pathway and that AQP1 is a key mediator in leptin-induced VM.

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.

Leptin: A Heavyweight Player in Obesity-Related Cancers

Obesity, defined as the abnormal or excessive expansion of white adipose tissue, has reached pandemic proportions and is recognized as an important health concern since it is a common root for several comorbidities, including malignancies. Indeed, the current knowledge of the white adipose tissue, which shifts its role from an energy storage tissue to an important endocrine and metabolic organ, has opened up new avenues for the discovery of obesity's effects on tumor biology. In this review, we will report the epidemiological studies concerning the strong impact of obesity in several types of cancer and describe the mechanisms underlying the heterotypic signals between cancer cell lines and adipocytes, with particular emphasis on inflammation, the insulin/IGF-1 axis, and adipokines. Among the adipokines, we will further describe the in vitro, in vivo, and clinical data concerning the role of leptin, recognized as one of the most important mediators of obesity-associated cancers. In fact, leptin physiologically regulates energy metabolism, appetite, and reproduction, and several studies have also described the role of leptin in affecting cancer development and progression. Finally, we will summarize the newest pharmacological strategies aimed at mitigating the protumorigenic effects of leptin, underlining their mechanisms of action.

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

Pro-angiogenic activity and vasculogenic mimicry in the tumor microenvironment by leptin in cancer

The acquired ability to induce the formation of a functional vasculature is a hallmark of cancer. Blood vessels in tumors are formed through various mechanisms, among the most important in cancer biology, angiogenesis, and vasculogenic mimicry have been described. Leptin is one of the main adipokines secreted by adipocytes in normal breast tissue and the tumor microenvironment. Here, we provide information on the relationship between leptin and the development of angiogenesis and vasculogenic mimicry in different types of cancer. Here, we report that leptin activates different pathways such as JAK-STAT3, MAPK/ERK, PKC, JNK, p38, and PI3K-Akt to induce the expression of various angiogenic factors and vasculogenic mimicry. In vivo models, leptin induces blood vessel formation through the PI3K-Akt-mTOR pathway. Interestingly, the relationship between leptin and vasculogenic mimicry was more significant in breast cancer. The information obtained suggests that leptin could be playing an essential role in tumor survival and metastasis through the induction of vascular mechanisms such as angiogenesis and vasculogenic mimicry; thus, leptin-induced pathways could be suggested as a promising therapeutic target.

Metabolic Hormones Modulate Macrophage Inflammatory Responses

Simple Summary

Macrophages are a type of immune cell which play an important role in the development of cancer. Obesity increases the risk of cancer and obesity also causes disruption to the normal levels of hormones that are produced to coordinate metabolism. Recent research now shows that these metabolic hormones also play important roles in macrophage immune responses and so through macrophages, disrupted metabolic hormone levels may promote cancer. This review article aims to highlight and summarise these recent findings so that the scientific community may better understand how important this new area of research is, and how these findings can be capitalised on for future scientific studies.

Abstract

Macrophages are phagocytotic leukocytes that play an important role in the innate immune response and have established roles in metabolic diseases and cancer progression. Increased adiposity in obese individuals leads to dysregulation of many hormones including those whose functions are to coordinate metabolism. Recent evidence suggests additional roles of these metabolic hormones in modulating macrophage inflammatory responses. In this review, we highlight key metabolic hormones and summarise their influence on the inflammatory response of macrophages and consider how, in turn, these hormones may influence the development of different cancer types through the modulation of macrophage functions.

Caveolin-1 promotes tumor cell proliferation and vasculogenic mimicry formation in human glioma

Vasculogenic mimicry (VM) plays an important role in human glioma progression and resistance to antiangiogenic therapy as a compensatory neovascularization mechanism in malignant tumors. Caveolin-1 (Cav-1) has been found to contribute to VM formation. However, it remains largely unknown whether Cav-1 expression correlates with VM in glioma. In this study, we examined CAV-1 expression levels and VM in human glioma cell lines and in 94 human gliomas with different grades of malignancy, and present Cox proportional hazards regression. The molecular role of Cav-1 in glioma cells was investigated using quantitative polymerase chain reaction (qRT-PCR) assays, western blotting, CCK-8 assays, and tubule formation assays. Cav-1 expression and VM formation were positively correlated with each other and both were closely associated with glioma development and progression as evidenced by the presence of cystic tumor, shortened survival time, and advanced-stage glioma in glioma patients with Cav-1 overexpression/increased VM formation. Cav-1 promoted U251 glioma cell proliferation and VM formation in a Matrigel-based 3D culture model. VM-associated factors including hypoxia-inducible factor 1α (HIF-1α) and p-Akt was significantly elevated by Cav-1 overexpression but suppressed by siCav-1 in U251 cells. Collectively, our study identified Cav-1 as an important regulator of glioma cell proliferation and VM formation, contributing to glioma development and progression.

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.

The Diagnostic and Therapeutic Role of Leptin and Its Receptor ObR in Glioblastoma Multiforme

Simple Summary

Despite recent advances in molecular brain tumor therapies, glioblastoma multiforme remains a diagnostic and therapeutic challenge with, in most cases, unfavorable outcome. Leptin and related mediators of immune-metabolic traffic have attracted increased recognition in the past decade in brain tumor biology, in particular potential implications in the diagnosis and treatment of recurrent and newly diagnosed high and low grade gliomas. Randomized controlled trails are on the way to elaborate the role of leptin and its receptor ObR by targeting and using antidiabetic drugs known to interact with distinct pathways associated with leptin signaling. To date, most of the findings in clinical studies remain preliminary and of heterogenous character, although experimental studies have underpinned the relevance of leptin and ObR in the pathophysiology of brain tumors in general.

Abstract

Leptin has been recognized as a potential tumor growth promoter in various cancers including cranial tumor pathologies such as pituitary adenomas, meningiomas and gliomas. Despite recent advances in adjunctive therapy and the established surgical resection, chemo- and radiotherapy regimen, glioblastoma multiforme remains a particular diagnostic and therapeutic challenge among the intracranial tumor pathologies, with a poor long-term prognosis. Systemic inflammation and immune-metabolic signaling through diverse pathways are thought to impact the genesis and recurrence of brain tumors, and glioblastoma multiforme in particular. Among the various circulating mediators, leptin has gained especial diagnostic and therapeutic interest, although the precise relationship between leptin and glioblastoma biology remains largely unknown. In this narrative review (MEDLINE/OVID, SCOPUS, PubMed and manual searches of the bibliographies of known primary and review articles), we discuss the current literature using the following search terms: leptin, glioblastoma multiforme, carcinogenesis, immunometabolism, biomarkers, metformin, antidiabetic medication and metabolic disorders. An increasing body of experimental evidence implicates a relationship between the development and maintenance of gliomas (and brain tumors in general) with a dysregulated central and peripheral immune-metabolic network mediated by circulating adipokines, chemokines and cellular components, and in particular the leptin adipokine. In this review, we summarize the current evidence of the role of leptin in glioblastoma pathophysiology. In addition, we describe the status of alternative diagnostic tools and adjunctive therapeutics targeting leptin, leptin-receptors, antidiabetic drugs and associated pathways. Further experimental and clinical trials are needed to elucidate the mechanism of action and the value of immune-metabolism molecular phenotyping (central and peripheral) in order to develop novel adjunctive diagnostics and therapeutics for newly diagnosed and recurrent glioblastoma patients.

The effect of hepatocellular carcinoma-associated fibroblasts on hepatoma vasculogenic mimicry

Vasculogenic Mimicry (VM) is the main source of blood supply in the early stage of tumor growth. Carcinoma-associated fibroblasts (CAFs) are one of the most important host cells in the tumor microenvironment. Some studies have found that CAFs can promote tumor angiogenesis, but there are few reports on the relationship between CAFs and VM. Tissue samples were collected from 60 cases of hepatocellular carcinoma (HCC) and 10 persons with normal liver function. The relationship between VM expression and clinicopathologic features was analyzed. Furthermore, the relationship between VM expression and vimentin or α-SMA expression was analyzed. Primary culture of hepatocellular CAFs and the collection of conditioned media were carried out. The effects of hepatocellular CAF conditioned medium on the formation of VM and the levels of VM-related proteins and genes in MHCC-97H cells were studied. The positive rate of VM was 35.0% in HCC tissues. There was no VM expression in normal liver tissues. VM expression was related to tumor diameter, Edmondson grade, clinical stage, and liver cirrhosis. The expression of vimentin and α-SMA in VM-positive patients was higher than in VM-negative patients. Different concentrations of hepatocellular CAF conditioned medium could promote the formation of VM and increase the expression of VM-related genes and proteins (MMP2 and EphA2) in MHCC-97H cells. The results show that there was a significant correlation between VM formation and the expression of vimentin or α-SMA in HCC tissues. The conditioned medium of hepatocellular CAFs may promote VM formation and the expression of VM-related genes and proteins (MMP2 and EphA2) in hepatoma cell line MHCC-97H.

Integration and Comparison of Transcriptomic and Proteomic Data for Meningioma

Meningioma are the most frequent primary intracranial tumour. Management of aggressive meningioma is complex, and development of effective biomarkers or pharmacological interventions is hampered by an incomplete knowledge of molecular landscape. Here, we present an integrated analysis of two complementary omics studies to investigate alterations in the "transcriptome-proteome" profile of high-grade (III) compared to low-grade (I) meningiomas. We identified 3598 common transcripts/proteins and revealed concordant up- and downregulation in grade III vs. grade I meningiomas. Concordantly upregulated genes included FABP7, a fatty acid binding protein and the monoamine oxidase MAOB, the latter of which we validated at the protein level and established an association with Food and Drug Administration (FDA)-approved drugs. Notably, we derived a plasma signature of 21 discordantly expressed genes showing positive changes in protein but negative in transcript levels of high-grade meningiomas, including the validated genes CST3, LAMP2, PACS1 and HTRA1, suggesting the acquisition of these proteins by tumour from plasma. Aggressive meningiomas were enriched in processes such as oxidative phosphorylation and RNA metabolism, whilst concordantly downregulated genes were related to reduced cellular adhesion. Overall, our study provides the first transcriptome-proteome characterisation of meningioma, identifying several novel and previously described transcripts/proteins with potential grade III biomarker and therapeutic significance.

Galectin-1 Promotes Vasculogenic Mimicry in Gastric Cancer by Upregulating EMT Signaling

Background: Galectin-1 (Gal-1) expression was positively associated with vasculogenic mimicry (VM) in primary gastric cancer (GC) tissue, and that both Gal-1 expression and VM in GC tissue are indicators of poor prognosis. However, whether Gal-1 promotes VM, and by what mechanismsremains unknown.

Methods: To investigate the underlying mechanisms,wound healing assay, proliferation assay, invasion assay, and three-dimensional culture were used to evaluate the invasion, metastasis and promoted VM formation effects of the Gal-1. We monitored the expression level of sociated proteins in GC tissues, cell lines in vitro and nude mice tumorigenicity in vivo by immunohistochemistry and western blot.

Results: Gal-1 overexpression significantly promoted the proliferation, invasion, migration, and VM formation of MGC-803 cells. Gal-1 was associated with E-cadherin and vimentin in vitro and in clinical samples. The epithelial-to-mesenchymal transition (EMT) induced in MGC-803 cells by TGF-β1 was accompanied by Gal-1 activation and promotion of VM formation, while knockdown of Gal-1 reduced the response to TGF-β1, suggesting that Gal-1 promotes VM formation by activating EMT signaling. Overexpression of Gal-1 accelerated subcutaneous xenograft growth and facilitated pulmonary metastasis in athymic mice, enhanced the expression of EMT markers, and promoted VM formation in vivo.

Conclusion: Our results indicated that Gal-1 promotes VM in GC by upregulating EMT signaling; thus, Gal-1 and this pathway are potential novel targets to treat VM in GC.

Fact or Fiction, It Is Time for a Verdict on Vasculogenic Mimicry?

The term vasculogenic mimicry (VM) refers to the capacity of certain cancer cells to form fluid-conducting structures within a tumor in an endothelial cell (EC)-free manner. Ever since its first report by Maniotis in 1999, the existence of VM has been an extremely contentious issue. The overwhelming consensus of the literature suggests that VM is frequently observed in highly aggressive tumors and correlates to lower patient survival. While the presence of VM in vivo in animal and patient tumors are claimed upon the strong positive staining for glycoproteins (Periodic Acid Schiff, PAS), it is by no means universally accepted. More controversial still is the existence of an in vitro model of VM that principally divides the scientific community. Original reports demonstrated that channels or tubes occur in cancer cell monolayers in vitro when cultured in matrigel and that these structures may support fluid movement. However, several years later many papers emerged stating that connections formed between cancer cells grown on matrigel represented VM. We speculate that this became accepted by the cancer research community and now the vast majority of the scientific literature reports both presence and mechanisms of VM based on intercellular connections, not the presence of fluid conducting tubes. In this opinion paper, we call upon evidence from an exhaustive review of the literature and original data to argue that the majority of in vitro studies presented as VM do not correspond to this phenomenon. Furthermore, we raise doubts on the validity of concluding the presence of VM in patient samples and animal models based solely on the presence of PAS+ staining. We outline the requirement for new biomarkers of VM and present criteria by which VM should be defined in vitro and in vivo.

The Expression of Leptin and Its Receptor During Tumorigenesis of Diffuse Gliomas such as Astrocytoma and Oligodendroglioma- Grade II, III and IV (NOS)

Background: Leptin, an adipocytokine functions via the leptin receptor, OB-Rb that contains an intact intracellular domain and activates the JAK/STAT signalling cascade. It stimulates growth, migration and invasion of cancer cells in vitro potentiating angiogenesis. Recently, the involvement of leptin in tumor progression is being explored. Gliomas exhibit poor prognosis, low survival rates demanding for novel therapeutic regimens resulting in discovery of many potential biomarkers and pharmaceutical targets. We analysed the potential role of leptin and OB-Rb in carcinogenesis of malignant gliomas. Methods: Sixty fresh tissue samples of diffuse gliomas were collected after tumor excision. Real time PCR, immunohistochemical (IHC) analysis and western blot analysis were carried out to assess the expression of leptin and its receptor. Results: The present study demonstrates the expression of leptin and LepR and their involvement in tumor progression. Of the 60 cases, 57 cases (95%) and 53 cases (88.3%) showed amplification for leptin and OB-Rb respectively. The expression of these proteins were measured semi-quantitatively and correlated with degree of malignancy (p<0.05). The bands were visualised on western blot. Conclusion: Leptin may be valued as a pharmaceutical target and anti-leptin compounds could be developed as drugs in mono- or combined therapies for these tumors.

Pectin Oligosaccharides Ameliorate Colon Cancer by Regulating Oxidative Stress- and Inflammation-Activated Signaling Pathways

Colon cancer (CC) is the third common neoplasm worldwide, and it is still a big challenge for exploring new effective medicine for treating CC. Natural product promoting human health has become a hot topic and attracted many researchers recently. Pectin, a complex polysaccharide in plant cell wall, mainly consists of four major types of polysaccharides: homogalacturonan, xylogalacturonan, rhamnogalacturonan I and II, all of which can be degraded into various pectin oligosaccharides (POS) and may provide abundant resource for exploring potential anticancer drugs. POS have been regarded as a novel class of potential functional food with multiple health-promoting properties. POS have antibacterial activities against some aggressive and recurrent bacterial infection and exert beneficial immunomodulation for controlling CC risk. However, the molecular functional role of POS in the prevention of CC risk and progression remains doubtful. The review focuses on antioxidant and anti-inflammatory roles of POS for promoting human health by regulating some potential oxidative and inflammation-activated pathways, such as ATP-activated protein kinase (AMPK), nuclear factor erythroid-2-related factor-2 (Nrf2), and nuclear factor-κB (NF-κB) pathways. The activation of these signaling pathways increases the antioxidant and antiinflammatory activities, which will result in the apoptosis of CC cells or in the prevention of CC risk and progression. Thus, POS may inhibit CC development by affecting antioxidant and antiinflammatory signaling pathways AMPK, Nrf2, and NF-κB. However, POS also can activate signal transduction and transcriptional activator 1 and 3 signaling pathway, which will reduce antioxidant and anti-inflammatory properties and promote CC progression. Specific structural and structurally modified POS may be associated with their functions and should be deeply explored in the future. The present review paper lacks the important information for the linkage between the specific structure of POS and its function. To further explore the effects of prebiotic potential of POS and their derivatives on human immunomodulation in the prevention of CC, the specific POS with a certain degree of polymerization or purified polymers are highly demanded to be performed in clinical practice.

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.

Prognostic significance of galectin-1 and vasculogenic mimicry in patients with gastric cancer

INTRODUCTION

We evaluated the expression of galectin-1 (Gal-1) and vasculogenic mimicry (VM) in gastric cancer (GC) and investigated their relationships with the clinicopathological factors and prognostic significance in GC.

MATERIALS AND METHODS

Immunohistochemical (IHC) staining and CD34-periodic acid-Schiff double stain were used to investigate Gal-1 expression and VM in paraffin-embedded sections from 127 patients with GC of all tumor stages. The relationships between Gal-1 expression and VM, clinicopathological variables, and survival were analyzed. P < 0.05 was considered statistically significant.

RESULTS

Among the 127 cases, 86 (67.7%) were positive for Gal-1; VM was detected in 29 cases (22.8%). There was a significant association between VM and the Gal-1 IHC staining; all cases with VM were positive for Gal-1 staining. Gal-1 expression and VM in primary GC tissue were associated with tumor size, differentiation, depth of tumor invasion, stage, lymph node metastases, and tumor emboli in microvessels (all, P < 0.05). Kaplan-Meier analysis revealed that the overall survival time was 52.56 ± 2.44 months (95% confidence interval [CI]: 47.77-57.35) for patients with Gal-1-negative and VM-negative primary GC tissue, 43.83 ± 2.17 months (95% CI: 39.58-48.08) for patients with Gal-1-positive but VM-negative primary GC tissue, and 23.97 ± 2.44 months (95% CI: 19.18-28.76) for patients with Gal-1-positive and VM-positive primary GC tissue (χ² = 60.21, P < 0.01). Gal-1 expression was positively associated with VM in primary GC tissue.

CONCLUSION

Both Gal-1 expression and VM in primary GC tissue are indicators of poor prognosis for GC after gastrectomy, and Gal-1 may be a novel target for treating VM in GC.