Apelin beyond kidney failure and hyponatremia: a useful biomarker for cancer disease progression evaluation

Apelin/APJ: Another Player in the Cancer Biology Network

The apelinergic system exerts multiple biological activities in human pathologies, including cancer. Overactivation of apelin/APJ, which has been detected in many malignant tumors, and the strong correlation with progression-free and overall survival, suggested the role of an oncogene for the apelin gene. Emerging evidence sheds new light on the effects of apelin on cellular functions and homeostasis in cancer cells and supports a direct role for this pathway on different hallmarks of cancer: "sustaining proliferative signaling", "resisting cell death", "activating invasion and metastasis", "inducing/accessing vasculature", "reprogramming cellular metabolism", "avoiding immune destruction" and "tumor-promoting inflammation", and "enabling replicative immortality". This article reviews the currently available literature on the intracellular processes regulated by apelin/APJ, focusing on those pathways correlated with tumor development and progression. Furthermore, the association between the activity of the apelinergic axis and the resistance of cancer cells to oncologic treatments (chemotherapy, immunotherapy, radiation) suggests apelin/APJ as a possible target to potentiate traditional therapies, as well as to develop diagnostic and prognostic applications. This issue will be also covered in the review.

Modified elastic intramedullary nail internal fixation for distal tibial metaphyseal junction fracture

Objective

To investigate the application of modified elastic intramedullary nail and the outcomes between modified elastic stable intramedullary nailing and traditional elastic stable intramedullary nailing in children with distal tibial metaphyseal junction fracture.

Methods

A retrospective study was conducted. From January 2018 to January 2021, a total of 36 children with distal tibial metaphyseal junction fracture were treated in our hospital. All of them were treated with closed reduction and elastic stable intramedullary nailing internal fixation. A total of 18 children were treated by modified elastic stable intramedullary nailing and 18 children were treated by traditional elastic stable intramedullary nailing. Postoperative imaging, clinical efficacy, and complications were analyzed.

Results

The mean follow-up time was 20 (15-36) months in modified group and 22 (16-33) months in traditional group. There were no complications such as infection, loss of reduction, and unequal length of lower limbs in modified group while loss of reduction occurred in two cases in traditional group. In these two cases of loss of reduction, we preformed manual reduction and replacement of long leg casts, and there was no loss of reduction, and the patient achieved a good prognosis. In the last follow-up, American Orthopaedic Foot & Ankle Society score was used. In modified group, excellent outcome achieved in 17 cases, good outcome achieved in 1 case, and satisfactory therapeutic effect was achieved. In traditional elastic stable intramedullary nailing group, excellent outcome achieved in 14 cases, and good outcome achieved in 4 cases. There was no statistical difference in the scores between the two groups.

Conclusion

It was concluded that modified elastic stable intramedullary nailing fixation is a safe and effective treatment.

Left Ventricular Mass Index Predicts Renal Function Decline in Patients with Chronic Kidney Disease

Background and Objectives: Several studies revealed a relation between abnormal cardiac remodeling and glomerular filtration rate (GFR) decline, but there are limited data regarding echocardiographic changes in chronic kidney disease (CKD). This study evaluated the abnormal cardiac structures characterizing patients with CKD, assessing the independent association between echocardiographic parameters and the risk of decline in renal function. Materials and Methods: In total, 160 patients with CKD were studied. All patients underwent an echocardiographic exam and 99mTc-DTPA renal scintigraphy to measure the GFR. After the baseline assessments, patients were followed prospectively for 12 months, or until the endpoint achievement, defined as a worsening in renal function (doubling of baseline serum creatinine, GFR decline ≥25%, the start of dialysis). Results: Patients with GFR values of 34.8 ± 15 mL/min, identifying stages III-IV of CKD, were associated with high levels of left ventricular mass index (LVMi) (101.9 ± 12.2 g/m2), which was related to proteinuria, systolic blood pressure, and pulmonary artery systolic pressure in a multiple regression model. During the observational period, 26% of patients reached the endpoint. Regression analysis revealed LVMi as a predictor of change in renal function after adjusting for kidney and cardiac risk factors. Multiple Cox regression indicated that an increase in LVMi was associated with a 12% increased risk of kidney disease progression (HR: 1.12; 95% CI: 1.04-1.16; p = 0.001). Conclusions: In patients with CKD, high LVMi represents an independent predictor of the progressive decline of the renal function, until the start of renal replacement therapy. Echocardiography can help identify patients at high risk for renal disease worsening in patients with CKD independently of clinical cardiac involvement.

The Modulation of Adipokines, Adipomyokines, and Sleep Disorders on Carcinogenesis

Obesity and sarcopenia, i.e., decreased skeletal muscle mass and function, are global health challenges. Moreover, people with obesity and sedentary lifestyles often have sleep disorders. Despite the potential associations, metabolic disturbances linking obesity, sarcopenia, and sleep disorders with cancer are neither well-defined nor understood fully. Abnormal levels of adipokines and adipomyokines originating from both adipose tissue and skeletal muscles are observed in some patients with obesity, sarcopenia and sleep disorders, as well as in cancer patients. This warrants investigation with respect to carcinogenesis. Adipokines and adipomyokines may exert either pro-carcinogenic or anti-carcinogenic effects. These factors, acting independently or together, may significantly modulate the incidence and progression of cancer. This review indicates that one of the possible pathways influencing the development of cancer may be the mutual relationship between obesity and/or sarcopenia, sleep quantity and quality, and adipokines/adipomyokines excretion. Taking into account the high proportion of persons with obesity and sedentary lifestyles, as well as the associations of these conditions with sleep disturbances, more attention should be paid to the individual and combined effects on cancer pathophysiology.

Anti-angiogenic therapy in ovarian cancer: Current understandings and prospects of precision medicine

Ovarian cancer (OC) remains the most fatal disease of gynecologic malignant tumors. Angiogenesis refers to the development of new vessels from pre-existing ones, which is responsible for supplying nutrients and removing metabolic waste. Although not yet completely understood, tumor vascularization is orchestrated by multiple secreted factors and signaling pathways. The most central proangiogenic signal, vascular endothelial growth factor (VEGF)/VEGFR signaling, is also the primary target of initial clinical anti-angiogenic effort. However, the efficiency of therapy has so far been modest due to the low response rate and rapidly emerging acquiring resistance. This review focused on the current understanding of the in-depth mechanisms of tumor angiogenesis, together with the newest reports of clinical trial outcomes and resistance mechanism of anti-angiogenic agents in OC. We also emphatically summarized and analyzed previously reported biomarkers and predictive models to describe the prospect of precision therapy of anti-angiogenic drugs in OC.

Apelin triggers macrophage polarization to M2 type in head and neck cancer

Cancer comes after cardiovascular diseases in terms of mortality rate in the world. Chemotherapy, radiotherapy and surgical interventions are the current cancer treatment. Recently, it has been observed that immunotherapeutic approaches provide a significant improvement when used along with these interventions. The mononuclear system mainly consists of macrophages that play an active role in the pathology of many diseases because of having high plasticity capacities. Previous research suggested that they can be used as an alternative to cancer treatment. Aim was to investigate the effect of apelin on macrophage polarization in the tumor microenvironment. Mouse macrophage cell line RAW264.7 cells and head and were chosen for this study. The apelin expression was knockdown in neck cell carcinoma cell line SCCL MT1 cells using shRNA technique. SCCL MT1 cells having normal or suppressed apelin expression were co-cultured with mouse macrophage RAW264.7 cells. The effect of co-culturing on the expression of inflammatory genes in RAW264.7 cells was investigated. Suppressed apelin expression in SCCL MT1 cells resulted in elevated pro-inflammatory response in co-cultured macrophages. Expression of the IL1β, IL6, and TNFα genes significantly increased, however anti-inflammatory cytokine levels were significantly decreased. However, in the control group, a downregulation was determined in pro-inflammatory genes, while an increase was observed in anti-inflammatory genes. The protein levels of these cytokines in concordance with the RT-PCR analysis. As a result of this study, apelin released from cancer cells was found to affect macrophage polarization. These results indicated that the apelin peptide may cause the intense presence of M2-type macrophages in the tumor niche, and the therapeutic approaches targeting of apelin in cancer cells may have a potential role in macrophage polarization.

TFEB Rearranged Renal Cell Carcinoma: Pathological and Molecular Characterization of 10 Cases, with Novel Clinical Implications: A Single Center 10-Year Experience

To report our experience with the cases of TFEB rearranged RCC, with particular attention to the clinicopathological, immunohistochemical and molecular features of these tumors and to their predictive markers of response to therapy. We have retrieved the archives of 9749 renal cell carcinomas in the Institute of Urology, Peking University and found 96 rearranged RCCs between 2013 and 2022. Among these renal tumors, ten cases meet the morphologic, immunohistochemical and FISH characterization for TFEB rearranged RCC. The 10 patients' mean and median age is 34.9 and 34 years, respectively (range 23-55 years old), and the male to female ratio is 1:1.5. Macroscopically, these tumors generally have a round shape and clear boundary. They present with variegated, grayish yellow and grayish brown cut surface. The average maximum diameter of the tumor is 8.5 cm and the median 7.7 (ranged from 3.4 to 16) cm. Microscopically, the tumor is surrounded by a thick local discontinuous pseudocapsule. All tumors exhibit two types of cells: voluminous, clear and eosinophilic cytoplasm cells arranged in solid sheet, tubular growth pattern with local cystic changes, and papillary, pseudopapillary and compact nested structures are also seen in a few cases. Non-neoplastic renal tubules are entrapped in the tumor. A biphasic "rosette-like" pattern, psammomatous calcifications, cytoplasmic vacuolization, multinucleated giant cells and rhabdomyoid phenotype can be observed in some tumors. A few tumors may be accompanied by significant pigmentation or hemorrhage and necrosis. The nucleoli are equivalent to the WHO/ISUP grades 2-4. All tumors are moderately to strongly positive for Melan-A, TFEB, Vimentin and SDHB, and negative for CK7, CAIX, CD117, EMA, SMA, Desmin and Actin. CK20 and CK8/18 are weakly positive. In addition, AE1/AE3, P504s, HMB45 and CD10 are weakly moderately positive. TFE3 is moderately expressed in half of the cases. PAX8 can be negative, weakly positive or moderately-strongly positive. The therapy predictive marker for PD-L1 (SP263) is moderately to strongly positive membranous staining in all cases. All ten tumors demonstrate a medium frequency of split TFEB fluorescent signals ranging from 30 to 50% (mean 38%). In two tumors, the coincidence of the TFEB gene copy number gains are observed (3-5 fluorescent signals per neoplastic nuclei). Follow-up is available for all patients, ranging from 4 to 108 months (mean 44.8 and median 43.4 months). All patients are alive, without tumor recurrences or metastases. We described a group of TFEB rearranged RCC identified retrospectively in a large comprehensive Grade III hospital in China. The incidence rate was about 10.4% of rearranged RCCs and 0.1% of all the RCCs that were received in our lab during the ten-year period. The gross morphology, histological features, and immunohistochemistry of TFEB rearranged RCC overlapped with other types of RCC such as TFE3 rearranged RCC, eosinophilic cystic solid RCC, or epithelioid angiomyolipoma, making the differential diagnosis challenging. The diagnosis was based on TFEB fluorescence in situ hybridization. At present, most of the cases reported in the literature have an indolent clinical behavior, and only a small number of reported cases are aggressive. For this small subset of aggressive cases, it is not clear how to plan treatment strategies, or which predictive markers could be used to assess upfront responses to therapies. Between the possible options, immunotherapy currently seems a promising strategy, worthy of further exploration. In conclusion, we described a group of TFEB rearranged RCC identified in a large, comprehensive Grade III hospital in China, in the last 10 years.

Efficacy and Safety of Cabozantinib in Patients with Advanced or Metastatic Renal Cell Carcinoma: A Multicenter Retrospective Cohort Study

A multicenter retrospective study was conducted to evaluate the efficacy and safety of cabozantinib in patients with advanced or metastatic renal cell carcinoma (mRCC). We enrolled 53 patients with mRCC who received cabozantinib at eight institutions in Japan. The primary endpoint was overall survival (OS). The secondary endpoints were objective response rate (ORR), disease control rate (DCR), and progression-free survival (PFS). In addition, we analyzed prognostic factors in patients with mRCC treated with cabozantinib. The median follow-up period was 8 months, and the median OS was 20.0 months. The ORR and DCR were 39.6% and 83.0%, respectively. The median PFS was 11.0 months. PFS was significantly shorter in patients previously treated with at least two tyrosine kinase inhibitors and in those with C-reactive protein (CRP) ≥ 1.27 mg/dL (p = 0.021 and p = 0.029, respectively). Adverse events of any grade and grades ≥3 occurred in 42 (79.2%) and 10 (18.9%) patients, respectively. Cabozantinib is a useful treatment option for patients with mRCC and may benefit from earlier use. In this study, CRP ≥ 1.27 mg/dL is a poor prognostic factor in patients treated with cabozantinib, and careful follow-up may be required in treating patients with high CRP.

Potential Value of Visfatin, Omentin-1, Nesfatin-1 and Apelin in Renal Cell Carcinoma (RCC): A Systematic Review and Meta-Analysis

Renal cell carcinoma (RCC) is the most lethal genitourinary malignancy. Obesity is a risk factor for RCC development. The role of adipokines in the relationship between obesity and RCC requires confirmatory evidence in the form of a systematic review and meta-analysis, specifically for visfatin, omentin-1, nesfatin-1 and apelin. A search of databases up to July 2022 (PubMed, Web of Science and Scopus) for studies reporting the association of these selected adipokines with RCC was conducted. A total of 13 studies fulfilled the selection criteria. Only visfatin (p < 0.05) and nesfatin-1 (p < 0.05) had a significant association with RCC. Meanwhile, apelin and omentin-1 showed no association with RCC. The meta-analysis results of nesfatin-1 showed no association with early-stage (OR = 0.09, 95% CI = −0.12−0.29, p = 0.41), late-stage (OR = 0.36, 95% CI = 0.07−1.89, p = 0.23) and low-grade (OR = 1.75, 95% CI = 0.37−8.27, p = 0.48) RCC. However, nesfatin-1 showed an association with a high grade of the disease (OR = 0.29, 95% CI = 0.13−0.61, p = 0.001) and poorer overall survival (OS) (HR = 3.86, 95% CI = 2.18−6.85; p < 0.01). Apelin showed no association with the risk of RCC development (mean difference = 21.15, 95% CI = −23.69−65.99, p = 0.36) and OS (HR = 1.04, 95% Cl = 0.45−2.41; p = 0.92). Although the number of studies evaluated was limited, analysis from this systematic review and meta-analysis indicate that visfatin and nesfatin-1 were elevated. In summary, these adipokines may play a role in the development and progression of RCC and hence may have potential diagnostic and prognostic capabilities for RCC.

Apelin, a Circulating Biomarker in Cancer Evaluation: A Systematic Review

Apelin is a promising biomarker for the detection and prognosis of cancer. This review aims to synthesize current knowledge on associations of circulating apelin with cancer, illustrate knowledge gaps, and discuss future research. Following PRISMA guidelines, CINAHL, EMBASE, and PubMed were searched using terms “cancer AND apelin” between 2011 and 2021, full text, and English language. Inclusion criteria: measured circulating apelin in adults 18 years or older with cancer, and observational, cross-sectional, longitudinal, case–control, cohort, quasi-experimental, or randomized control trials. Excluded were studies with animal models, tissue samples only, secondary data analyses, systematic reviews, literature reviews, grey literature, and conference abstracts. 16 articles were included. There were significant variations in measurement methods between studies. Comparison of circulating apelin between cases and controls and associations of circulating apelin with clinicopathological characteristics were inconsistent. Variations in results suggest that the relationship between circulating apelin and cancer differs among cancer types. Differences in measurement methods between studies highlight the need for consistency in future research to draw meaningful conclusions. Future research should seek to standardize methods of detecting circulating apelin and examine its associations with specific cancer types to determine what role that circulating apelin may play in cancer development and progression.

Upregulated Apelin Signaling in Pancreatic Cancer Activates Oncogenic Signaling Pathways to Promote Tumor Development

Despite decades of effort in understanding pancreatic ductal adenocarcinoma (PDAC), there is still a lack of innovative targeted therapies for this devastating disease. Herein, we report the expression of apelin and its receptor, APJ, in human pancreatic adenocarcinoma and its protumoral function. Apelin and APJ protein expression in tumor tissues from patients with PDAC and their spatiotemporal pattern of expression in engineered mouse models of PDAC were investigated by immunohistochemistry. Apelin signaling function in tumor cells was characterized in pancreatic tumor cell lines by Western blot as well as proliferation, migration assays and in murine orthotopic xenograft experiments. In premalignant lesions, apelin was expressed in epithelial lesions whereas APJ was found in isolated cells tightly attached to premalignant lesions. However, in the invasive stage, apelin and APJ were co-expressed by tumor cells. In human tumor cells, apelin induced a long-lasting activation of PI3K/Akt, upregulated β-catenin and the oncogenes c-myc and cyclin D1 and promoted proliferation, migration and glucose uptake. Apelin receptor blockades reduced cancer cell proliferation along with a reduction in pancreatic tumor burden. These findings identify the apelin signaling pathway as a new actor for PDAC development and a novel therapeutic target for this incurable disease.

Tumor apelin and obesity are associated with reduced neoadjuvant chemotherapy response in a cohort of breast cancer patients

Obesity is a known factor increasing the risk of developing breast cancer and reducing disease free survival. In addition to these well-documented effects, recent studies have shown that obesity is also affecting response to chemotherapy. Among the multiple dysregulations associated with obesity, increased level of the apelin adipokine has been recently shown to be directly involved in the association between obesity and increased breast cancer progression. In this study, we analyzed in a retrospective cohort of 62 breast cancer patients the impact of obesity and tumoral apelin expression on response to neoadjuvant chemotherapy. In the multivariate logistic regression, obesity and high tumoral apelin expression were associated with a reduced response to NAC in our cohort. However, obesity and high tumoral apelin expression were not correlated, suggesting that those two parameters could be independently associated with reduced NAC response. These findings should be confirmed in independent cohorts.

Study Progression of Apelin/APJ Signaling and Apela in Different Types of Cancer

Apelin is an endogenous ligand that binds to the G protein-coupled receptor angiotensin-like-receptor 1 (APJ). Apelin and APJ are widely distributed in organs and tissues and are involved in multiple physiological and pathological processes including cardiovascular regulation, neuroendocrine stress response, energy metabolism, etc. Additionally, apelin/APJ axis was found to play an important role in cancer development and progression. Apela is a newly identified endogenous ligand for APJ. Several studies have revealed the potential role of Apela in cancers. In this article, we review the current studies focusing on the role of apelin/APJ signaling and Apela in different cancers. Potential mechanisms by which apelin/APJ and Apela mediate the regulation of cancer development and progression were also mentioned. The Apelin/APJ signaling and Apela may serve as potential therapeutic candidates for treatment of cancer.

Apelin promotes blood and lymph vessel formation and the growth of melanoma lung metastasis

Apelin, a ligand of the APJ receptor, is overexpressed in several human cancers and plays an important role in tumor angiogenesis and growth in various experimental systems. We investigated the role of apelin signaling in the malignant behavior of cutaneous melanoma. Murine B16 and human A375 melanoma cell lines were stably transfected with apelin encoding or control vectors. Apelin overexpression significantly increased melanoma cell migration and invasion in vitro, but it had no impact on its proliferation. In our in vivo experiments, apelin significantly increased the number and size of lung metastases of murine melanoma cells. Melanoma cell proliferation rates and lymph and blood microvessel densities were significantly higher in the apelin-overexpressing pulmonary metastases. APJ inhibition by the competitive APJ antagonist MM54 significantly attenuated the in vivo pro-tumorigenic effects of apelin. Additionally, we detected significantly elevated circulating apelin and VEGF levels in patients with melanoma compared to healthy controls. Our results show that apelin promotes blood and lymphatic vascularization and the growth of pulmonary metastases of skin melanoma. Further studies are warranted to validate apelin signaling as a new potential therapeutic target in this malignancy.

Association between clinicopathological features of breast cancer with adipocytokine levels and oxidative stress markers before and after chemotherapy

Adipocytokines and markers of oxidative stress have been shown to exhibit potential for detection of advanced stage, HER2/neu status and lymph node metastases in patients with breast cancer, as well as in determining the efficiency of anti-cancer treatments. In the present study, blood concentrations of apelin (APLN), retinol-binding protein 4 (RBP4), 8-hydroxydeoxyguanosine (8-oxo-dG) and total antioxidant capacity (TAC) in women with breast cancer with different clinicopathological features were measured prior to and following adjuvant chemotherapy. The study included 60 women with breast cancer stratified according to tumor grade and size, HER-2/neu expression, and lymph node and hormone receptor status. Blood samples were taken before and after two cycles of adjuvant chemotherapy. None of the clinicopathological features were associated with the baseline concentrations of RBP4, 8-oxo-dG or TAC. An increased baseline concentration of APLN was observed in HER-2/neu positive patients. Moreover, through multivariate logistical regression analysis, APLN was shown to be independently associated with a positive HER/neu status. Chemotherapy treatment did not affect the levels of RBP4 or APLN, or TAC values when assessing all the patients, and when assessing the stratified groups of patients. Only 8-oxo-dG was found to be significantly decreased following drug administration (P=0.0009). This preliminary study demonstrated that APLN is a significant and independent predictor of HER-2/neu positive breast cancer. A significant reduction in 8-oxo-dG levels following chemotherapy may indicate its potential clinical utility in monitoring the effects of chemotherapy in breast cancer patients.

Obesity and triple-negative-breast-cancer: Is apelin a new key target?

Epidemiological studies have shown that obese subjects have an increased risk of developing triple‐negative breast cancer (TNBC) and an overall reduced survival. However, the relation between obesity and TNBC remains difficult to understand. We hypothesize that apelin, an adipokine whose levels are increased in obesity, could be a major factor contributing to both tumour growth and metastatization in TNBC obese patients. We observed that development of obesity under high‐fat diet in TNBC tumour‐bearing mice significantly increased tumour growth. By showing no effect of high‐fat diet in obesity‐resistant mice, we demonstrated the necessity to develop obesity‐related disorders to increase tumour growth. Apelin mRNA expression was also increased in the subcutaneous adipose tissue and tumours of obese mice. We further highlighted that the reproduction of obesity‐related levels of apelin in lean mice led to an increased TNBC growth and brain metastases formation. Finally, injections of the apelinergic antagonist F13A to obese mice significantly reduced TNBC growth, suggesting that apelinergic system interference could be an interesting therapeutic strategy in the context of obesity and TNBC.

The effects of apoptosis and apelin on lymph node metastasis in invasive breast carcinomas

This study aimed to evaluate the biological and clinical significance of apelin-36 in breast cancer and to compare apelin-36 expression and apoptotic index in both breast tissue and metastatic lymph nodes in patients with invasive breast carcinoma. In this study, both tumor tissue and metastatic lymph nodes of the same patient were collected from 60 cases of invasive breast carcinoma patients (IDC, ILC) and 20 cases of normal breast tissue with no tumor from mammoplasty were used as the control group. The expression of apelin was examined with immunohistochemically, and the apoptotic index was examined with TUNEL methods. According to Kruskal-Wallis analysis, there was a significant difference between IDC and the control group when the apelin expression was compared between the breast tissues (p = 0.001). There were significant differences between the three groups when comparing relationships with apoptotic index (p < 0.001). According to the Mann-Whitney U test, both tumor size and expression of apelin in lymph nodes in ILCs were significantly higher than IDCs. (p = 0.026, p = 0.024, respectively). According to correlation analysis, there was a good correlation between the expression of apelin in breast tissue and apelin expression in lymph nodes (p = 0.000). It is also found a similar relationship in terms of the apoptotic index (p = 0.000). In addition, the negative correlation was found between apelin expression and the apoptotic index in breast tissues (p = 0.003). Based on these results, apelin-36 can be used as a marker for determining the metastasis potential in invasive breast cancer.

circ-NOTCH1 acts as a sponge of miR-637 and affects the expression of its target gene Apelin to regulate gastric cancer cell growth

Gastric cancer (GC) is a major cause of cancer-related deaths worldwide, and has a low survival rate, low cure rate, high recurrence rate, and poor prognosis. Recent studies have indicated that circular RNAs (circRNAs) have important functions in the occurrence and progression of GC. Studies on circ-NOTCH1, which was shown to be highly expressed in GC, have indicated that miR-637 binds to circ-NOTCH1 at multiple sites, and a dual-luciferase reporter gene assay further confirmed that miR-637 indeed targeted circ-NOTCH1 and Apelin. Circ-NOTCH1 and Apelin are highly expressed in GC cells and tissues, whereas the expression of miR-637 is reduced. Circ-NOTCH1 and miR-637 do not regulate each other’s expression levels, but circ-NOTCH1significantly upregulates the expression of the miR-637 target gene Apelin, whereas miR-637 inhibites the expression of Apelin. Examination of GC cells showed that circ-NOTCH1 enhances cell proliferation and invasiveness, and reduces cell apoptosis; these effects were reversed by miR-637, which could terminate the above effects of circ-NOTCH1. When co-transfected with the circ-NOTCH1 overexpression plasmid and Apelin siRNAs, there were no obvious changes to the levels of cell proliferation, apoptosis, or invasiveness. Therefore, in GC cells, circ-NOTCH1 inhibits the transcriptional activity of miR-637, thereby upregulating the expression of its target gene Apelin and regulating cell proliferation, apoptosis, and invasiveness. This finding provides more experimental evidence for the function of circRNA in GC.

Role of Apelin/APJ axis in cancer development and progression

Apelin is an endogenous peptide, which is expressed in a vast board of organs such as the brain, placenta, heart, lungs, kidneys, pancreas, testis, prostate and adipose tissues. The apelin receptor, called angiotensin-like-receptor 1 (APJ), is also expressed in the brain, spleen, placenta, heart, liver, intestine, prostate, thymus, testis, ovary, lungs, kidneys, stomach, and adipose tissue. The apelin/APJ axis is involved in a number of physiological and pathological processes. The apelin expression is increased in various kinds of cancer and the apelin/APJ axis plays a key role in the development of tumors through enhancing angiogenesis, metastasis, cell proliferation and also through the development of cancer stem cells and drug resistance. The apelin also stops the apoptosis of cancer cells. The apelin/APJ axis was considered in this review as an attractive therapeutic target for cancer treatment.

Tumor angiogenesis: causes, consequences, challenges and opportunities

Tumor vascularization occurs through several distinct biological processes, which not only vary between tumor type and anatomic location, but also occur simultaneously within the same cancer tissue. These processes are orchestrated by a range of secreted factors and signaling pathways and can involve participation of non-endothelial cells, such as progenitors or cancer stem cells. Anti-angiogenic therapies using either antibodies or tyrosine kinase inhibitors have been approved to treat several types of cancer. However, the benefit of treatment has so far been modest, some patients not responding at all and others acquiring resistance. It is becoming increasingly clear that blocking tumors from accessing the circulation is not an easy task to accomplish. Tumor vessel functionality and gene expression often differ vastly when comparing different cancer subtypes, and vessel phenotype can be markedly heterogeneous within a single tumor. Here, we summarize the current understanding of cellular and molecular mechanisms involved in tumor angiogenesis and discuss challenges and opportunities associated with vascular targeting.

Bioinformatics Study of RNA Interference on the Effect of HIF-1α on Apelin Expression in Nasopharyngeal Carcinoma Cells

Background:

HIF-1α can affect the apelin expression and participates in the developments in cancers but the mechanism need to be explored further.

Objective:

This paper investigates apelin expression in nasopharyngeal carcinoma CNE-2 cells and its regulation by hypoxia inducible factor-1α (HIF-1α) under hypoxic conditions.

Methods:

CoCl2 was used to induce hypoxia in CNE-2 cells for 12h, 24h and 48h. HIF-1α small interference RNA (siRNA) was transfected into CNE-2 cells using a transient transfection method. HIF-1α and apelin mRNA levels were detected by real time PCR. Western blot was used to measure HIF-1α protein expression. The concentration of apelin in cell culture supernatant was determined by enzyme linked immunosorbent assay (ELISA).

Results:

HIF-1α and apelin mRNA levels and protein expression in CNE-2 cells increased gradually with increased duration of hypoxic exposure and were significantly reduced in HIF-1α siRNA transfected cells exposed to the same hypoxic conditions.

Conclusion:

Apelin expression is induced by hypoxia and regulated by HIF-1α in CNE-2 cells.

Circ-ZNF264 Promotes the Growth of Glioma Cells by Upregulating the Expression of miR-4493 Target Gene Apelin

Glioma is the most common malignant tumor in the brain and nervous system, with high recurrence and high mortality rate. Recent researches have shown that circular RNAs (circRNAs) play key roles in the genesis and progress of glioma. Detection of circRNAs in glioma cells revealed that the expression of circ-ZNF264 was upregulated. At the same time, the expression of miR-4493 was downregulated in glioma cells and had multiple binding sites on the circ-ZNF264 sequence. Dual luciferase reporter gene assay confirmed that miR-4493 could bind to circ-ZNF264 and apelin specifically. MiR-4493 expression was not changed, but its target gene apelin expression could be significantly upregulated by circ-ZNF264. MiR-4493 could inhibit the expression of circ-ZNF264 and apelin. Biological behaviors of glioma cells were detected; circ-ZNF264 promoted cell proliferation and invasion and inhibited apoptosis. MiR-4493 had the opposite effects and could terminate the above effects of circ-ZNF264. When the expression of apelin was downregulated and that of circ-ZNF264 was upregulated, the changes of the above biological behaviors were not obvious. Therefore, in glioma cells, circ-ZNF264 can inhibit the function of miR-4493 and then upregulate its target gene apelin expression, thus regulating glioma cell proliferation, apoptosis, and invasion. This finding provides more evidence for the role of circRNAs in glioma.

Classic and Novel Adipocytokines at the Intersection of Obesity and Cancer: Diagnostic and Therapeutic Strategies

PURPOSE OF REVIEW

In this review, we investigate the role of classic and novel adipocytokines in cancer pathogenesis synopsizing the mechanisms underlying the association between adipocytokines and malignancy. Special emphasis is given on novel adipocytokines as new evidence is emerging regarding their entanglement in neoplastic development.

RECENT FINDINGS

Recent data have emphasized the role of the triad of overweight/obesity, insulin resistance and adipocytokines in cancer. In the setting of obesity, classic and novel adipocytokines present independent and joint effects on activation of major intracellular signaling pathways implicated in cell proliferation, expansion, survival, adhesion, invasion, and metastasis. Until now, more than 15 adipocytokines have been associated with cancer, and this list continues to expand. While the plethora of circulating pro-inflammatory adipocytokines, such as leptin, resistin, extracellular nicotinamide phosphoribosyl transferase, and chemerin are elevated in malignancies, some adipocytokines such as adiponectin and omentin-1 are generally decreased in cancers and are considered protective against carcinogenesis. Elucidating the intertwining of inflammation, cellular bioenergetics, and adiposopathy is significant for the development of preventive, diagnostic, and therapeutic strategies against cancer. Novel more effective and safe adipocytokine-centered therapeutic interventions may pave the way for targeted oncotherapy.

The Role of Apelin in Cardiovascular Diseases, Obesity and Cancer

Apelin is an endogenous peptide identified as a ligand of the G protein-coupled receptor APJ. Apelin belongs to the family of adipokines, which are bioactive mediators released by adipose tissue. Extensive tissue distribution of apelin and its receptor suggests, that it could be involved in many physiological processes including regulation of blood pressure, body fluid homeostasis, endocrine stress response, cardiac contractility, angiogenesis, and energy metabolism. Additionally, this peptide participates in pathological processes, such as heart failure, obesity, diabetes, and cancer. In this article, we review current knowledge about the role of apelin in organ and tissue pathologies. We also summarize the mechanisms by which apelin and its receptor mediate the regulation of physiological and pathological processes. Moreover, we put forward an indication of apelin as a biomarker predicting cardiac diseases and various types of cancer. A better understanding of the function of apelin and its receptor in pathologies might lead to the development of new medical compounds.

Apelin: A putative novel predictive biomarker for bevacizumab response in colorectal cancer

Bevacizumab (bvz) is currently employed as an anti-angiogenic therapy across several cancer indications. Bvz response heterogeneity has been well documented, with only 10-15% of colorectal cancer (CRC) patients benefitting in general. For other patients, clinical efficacy is limited and side effects are significant. This reinforces the need for a robust predictive biomarker of response. To identify such a biomarker, we performed a DNA microarray-based transcriptional profiling screen with primary endothelial cells (ECs) isolated from normal and tumour colon tissues. Thirteen separate populations of tumour-associated ECs and 10 of normal ECs were isolated using fluorescence-activated cell sorting. We hypothesised that VEGF-induced genes were overexpressed in tumour ECs; these genes could relate to bvz response and serve as potential predictive biomarkers. Transcriptional profiling revealed a total of 2,610 differentially expressed genes when tumour and normal ECs were compared. To explore their relation to bvz response, the mRNA expression levels of top-ranked genes were examined using quantitative PCR in 30 independent tumour tissues from CRC patients that received bvz in the adjuvant setting. These analyses revealed that the expression of MMP12 and APLN mRNA was significantly higher in bvz non-responders compared to responders. At the protein level, high APLN expression was correlated with poor progression-free survival in bvz-treated patients. Thus, high APLN expression may represent a novel predictive biomarker for bvz unresponsiveness.

Adipose Tissue Metabolism and Cancer Progression: Novel Insights from Gut Microbiota?

Purpose of Review

Obesity is strongly associated with the development of several types of cancers. This review aims to discuss the recent key mechanisms and actors underlying the link between adipose tissue metabolism and cancer, and the unequivocal common mechanisms connecting gut microbes to adipose tissue and eventually cancer development.

Recent Findings

Complex interactions among systemic and tissue-specific pathways are suggested to link obesity and cancer, involving endocrine hormones, adipokines, fatty acids, inflammation, metabolic alterations, and hypoxia. Emerging evidence also suggests that the gut microbiota, another key environmental factor, may be considered as a converging element. Studies have shown that cancer susceptibility may be induced in germ-free mice colonized with the gut microbiota from high-fat diet-fed mice. Suggested mechanisms may involve inflammation, immunity changes, lipogenic substrates, and adipogenesis.

Summary

Cancer development is a complex process that may be under the control of previously unthought factors such as the gut microbiota. Whether specific intervention targeting the gut microbiota may reduce adipose tissue-driven cancer is an interesting strategy that remains to be proven.

Protamine is an antagonist of apelin receptor, and its activity is reversed by heparin

Apelin signaling plays an important role during embryo development and regulates angiogenesis, cardiovascular activity, and energy metabolism in adulthood. Overexpression and hyperactivity of this signaling pathway is observed in various pathologic states, such as cardiovascular diseases and cancer, which highlights the importance of inhibiting apelin receptor (APJ); therefore, we developed a cell-based screening assay that uses fluorescence microscopy to identify APJ antagonists. This approach led us to identify the U.S. Food and Drug Administration-approved compound protamine-already used clinically after cardiac surgery-as an agent to bind to heparin and thereby reverse its anticlotting activity. Protamine displays a 390-nM affinity for APJ and behaves as a full antagonist with regard to G protein and β-arrestin-dependent intracellular signaling. Ex vivo and in vivo, protamine abolishes well-known apelin effects, such as angiogenesis, glucose tolerance, and vasodilatation. Remarkably, protamine antagonist activity is fully reversed by heparin treatment both in vitro and in vivo Thus, our results demonstrate a new pharmacologic property of protamine-blockade of APJ-that could explain some adverse effects observed in protamine-treated patients. Moreover, our data reveal that the established antiangiogenic activity of protamine would rely on APJ antagonism.-Le Gonidec, S., Chaves-Almagro, C., Bai, Y., Kang, H. J., Smith, A., Wanecq, E., Huang, X.-P., Prats, H., Knibiehler, B., Roth, B. L., Barak, L. S., Caron, M. G., Valet, P., Audigier, Y., Masri, B. Protamine is an antagonist of apelin receptor, and its activity is reversed by heparin.

Tumor apelin, not serum apelin, is associated with the clinical features and prognosis of gastric cancer

BACKGROUND

To study the association between Apelin expression and the clinical features and postoperative prognosis in patients with gastric cancer (Int J Cancer 136:2388-2401, 2015).

METHODS

Tumor samples and matched adjacent normal tissues were collected from 270 patients with GC receiving surgical resection. The tumor and serum Apelin levels were determined by immunohistochemistry and ELISA methods, respectively. GC cell lines were cultured for migration and invasive assays.

RESULTS

Our data showed that tumor Apelin expression status, instead of serum Apelin level, was closely associated with more advance clinical features including tumor differentiation, lymph node and distant metastases. Moreover, patients with high tumor Apelin level had a significantly shorter overall survival period compared to those with low Apelin expression and those with or negative Apelin staining. Our in vitro study revealed that the Apelin regulated the migration and invasion abilities of GC cell lines, accompanied by up-regulations of a variety of cytokines associated with tumor invasiveness.

CONCLUSION

Our data suggest that tumor Apelin can be used as a marker to evaluate clinical characteristics and predict prognosis in GC patients.

Apelin/APJ system and cancer

Apelin is an endogenous ligand of the apelin receptor (APJ), a seven-transmembrane G protein-coupled receptor. Apelin/APJ system has a wide tissue distribution in the brain as well as in peripheral organs including heart, lung, vessels, and adipose tissue. Apelin/APJ was involved in regulating cardiac and vascular function, heart development, and vascular smooth muscle cell proliferation. In this article, we summarize the role of apelin/APJ system on lung cancer, gastroesophageal and colonic cancer, hepatocellular carcinoma, prostate cancer, endometrial cancer, oral squamous cell carcinoma, brain cancer, and tumor neoangiogenesis. Apelin/APJ may be a potential anticancer therapeutic target.

A role for novel adipose tissue-secreted factors in obesity-related carcinogenesis

Obesity, a pandemic disease, is caused by an excessive accumulation of fat that can have detrimental effects on health. Adipose tissue plays a very important endocrine role, secreting different molecules that affect body physiology. In obesity, this function is altered, leading to a dysfunctional production of several factors, known as adipocytokines. This process has been linked to various comorbidities associated with obesity, such as carcinogenesis. In fact, several classical adipocytokines with increased levels in obesity have been demonstrated to exert a pro-carcinogenic role, including leptin, TNF-α, IL-6 and resistin, whereas others like adiponectin, with decreased levels in obesity, might have an anti-carcinogenic function. In this expanding field, new proteomic techniques and approaches have allowed the identification of novel adipocytokines, a number of which exhibit an altered production in obesity and type 2 diabetes and thus are related to adiposity. Many of these novel adipocytokines have also been identified in various tumour types, such as that of the breast, liver or endometrium, thereby increasing the list of potential contributors to carcinogenesis. This review is focused on the regulation of these novel adipocytokines by obesity, including apelin, endotrophin, FABP4, lipocalin 2, omentin-1, visfatin, chemerin, ANGPTL2 or osteopontin, emphasizing its involvement in tumorigenesis.

Apelin promotes lymphangiogenesis and lymph node metastasis

Whereas the role of the G-protein-coupled APJ receptor and its ligand, apelin, in angiogenesis has been well documented, the ability of the apelin/APJ system to induce lymphangiogenesis and lymphatic metastasis has been largely unexplored. To this end, we first show that APJ is expressed in lymphatic endothelial cells (LECs) and, moreover, that it responds to apelin by activating the apelinergic signaling cascade. We find that although apelin treatment does not influence the proliferation of LECs in vitro, it enhances their migration, protects them against UV irradiation-induced apoptosis, increases their spheroid numbers in 3D culture, stimulates their in vitro capillary-like tube formation and, furthermore, promotes the invasive growth of lymphatic microvessels in vivo in the matrigel plug assay. We also demonstrate that apelin overexpression in malignant cells is associated with accelerated in vivo tumor growth and with increased intratumoral lymphangiogenesis and lymph node metastasis. These results indicate that apelin induces lymphangiogenesis and, accordingly, plays an important role in lymphatic tumor progression. Our study does not only reveal apelin as a novel lymphangiogenic factor but might also open the door for the development of novel anticancer therapies targeting lymphangiogenesis.

Emerging markers of cachexia predict survival in cancer patients

BACKGROUND

Cachexia may occur in 40% of cancer patients, representing the major cause of death in more than 20% of them. The aim of this study was to investigate the role of leptin, ghrelin and obestatin as diagnostic and predictive markers of cachexia in oncologic patients. Their impact on patient survival was also evaluated.

METHODS

140 adults with different cancer diagnoses were recruited. Thirty healthy volunteers served as control. Serum ghrelin, obestatin and leptin were tested at baseline and after a follow-up period of 18 months.

RESULTS

Ghrelin levels were significantly higher in cancer patients than in healthy subjects (573.31 ± 130 vs 320.20 ± 66.48 ng/ml, p < 0.0001), while obestatin (17.42 ± 7.12 vs 24.89 ± 5.54 ng/ml, p < 0.0001) and leptin (38.4 ± 21.2 vs 76.28 ± 17.48 ng/ml, p < 0.0001) values were lower. At ROC analyses the diagnostic profile of ghrelin (AUC 0.962; sensitivity 83%; specificity 98%), obestatin (AUC 0.798; sensitivity 74.5%; specificity 81.5%) and leptin (AUC 0.828; sensitivity 79%; specificity 73%) was superior to that of albumin (AUC 0.547; sensitivity 63%, specificity 69.4%) for detecting cachexia among cancer patients. On Cox multivariate analyses ghrelin (HR 1.02; 95% CI 1.01 - 1.03; p < 0.0001) and leptin (HR 0.94; 95% CI 0.92 - 0.96; p < 0.0001) were significant predictors of death even after correction for other known risk factors such as presence of metastasis and chronic kidney disease.

CONCLUSION

Ghrelin and leptin are promising biomarkers to diagnose cachexia and to predict survival in cancer patients.