Apelin Effects Migration and Invasion Abilities of Colon Cancer Cells

Mutual impact of adipocytes and colorectal cancer cells growing in co-culture conditions

BACKGROUND

Colorectal cancer (CRC) is the third most common malignancy worldwide. CRC cells are situated in an adipocyte-rich microenvironment, which leads to interactions between adipocytes and CRC cells. Upon exposure to cancer cells, adipocytes transform into cancer-associated adipocytes (CAAs), and as a result, they gain features that promote tumor progression. The aim of this research was to shed more light on the detailed role of interactions between adipocytes and CRC cells associated with cancer progression in the context of these alterations.

METHODS

To implement adipocyte-CRC cell interaction, a co-culture model was applied. The analyses mainly focused on the metabolic modifications within CAAs and CRC cells, as well as the proliferation and migration potential of CRC cells. The impact of CRC on adipocytes was investigated by qRT-PCR analysis and Oil Red O staining. Proliferation and migration of CRC cells upon co-culture were tested with videomicroscopy, XTT, and a wound healing assay. Metabolic changes within CAAs and CRC cells were investigated based on lipid droplet formation, cell cycle analysis, gene and protein expression by qRT-PCR, and western blotting techniques.

RESULTS

CRC cells induced reprogramming of adipocytes into CAAs, which was connected with downregulation of lipid droplet formation in CAAs and alteration in adipocyte features. CAAs showed decreased metabolism-related gene expression, phosphorylation of Akt, ERK kinases, STAT3, and lactate secretion in comparison to the control. CAAs also promoted the migration, proliferation, and lipid droplet accumulation of CRC cells. After co-culturing with adipocytes, there was a shift to the G2/M phase of the cell cycle according to the differences in cyclin expression.

CONCLUSION

There are complex bidirectional interactions between adipocytes and CRC cells that may be connected with the induction of CRC cell progression. Video Abstract.

Apelin receptor antagonist boosts dendritic cell vaccine efficacy in controlling angiogenic, metastatic and apoptotic-related factors in 4T1 breast tumor-bearing mice

Apelin/APJ axis plays a critical role in cancer progression, thus its targeting inhibits tumor growth. However, blocking of Apelin/APJ axis in combination with immunotherapeutic approaches may be more effective. This study aimed to investigate the effects of APJ antagonist ML221 in combination with a DC vaccine on angiogenic, metastatic and apoptotic-related factors in a breast cancer (BC) model. Four groups of female BALB/c mice with 4T1-induced BC were treated with PBS, APJ antagonist ML221, DC vaccine, and "ML221 + DC vaccine". After completion of the treatment, the mice were sacrificed and the serum levels of IL-9 and IL-35 as well as the mRNA expression of angiogenesis (including VEGF, FGF-2, and TGF-β), metastasis (including MMP-2, MMP-9, CXCR4) and apoptosis-related markers (Bcl-2, Bax, Caspase-3) in tumor tissues were determined using ELISA and real-time PCR, respectively. Angiogenesis was also evaluated by co-immunostaining of tumor tissues with CD31 and DAPI. Primary tumor metastasis to the liver was analyzed using hematoxylin-eosin staining. The efficiency of combination therapy with "ML221 + DC vaccine" was remarkably higher than single therapies in preventing liver metastasis compared to the control group. In comparison with the control group, combination therapy could significantly reduce the expression of MMP-2, MMP-9, CXCR4, VEGF, FGF-2, and TGF-β in tumor tissues (P < 0.05). It also decreased the serum level of IL-9 and IL-35 compared with the control group (P < 0.0001). Moreover, vascular density and vessel diameter were significantly reduced in the combination therapy group compared with the control group (P < 0.0001). Overall, our findings demonstrate that combination therapy using a blocker of the apelin/APJ axis and DC vaccine can be considered a promising therapeutic program in cancers.

Structure-function relationship and physiological role of apelin and its G protein coupled receptor

Apelin receptor (APJR) is a class A peptide (apelin) binding G protein-coupled receptor (GPCR) that plays a significant role in regulating blood pressure, cardiac output, and maintenance of fluid homeostasis. It is activated by a wide range of endogenous peptide isoforms of apelin and elabela. The apelin peptide isoforms contain distinct structural features that aid in ligand recognition and activation of the receptor. Site-directed mutagenesis and structure-based studies have revealed the involvement of extracellular and transmembrane regions of the receptor in binding to the peptide isoforms. The structural features of APJR activation of the receptor as well as mediating G-protein and β-arrestin-mediated signaling are delineated by multiple mutagenesis studies. There is increasing evidence that the structural requirements of APJR to activate G-proteins and β-arrestins are different, leading to biased signaling. APJR also responds to mechanical stimuli in a ligand-independent manner. A multitude of studies has focused on developing both peptide and non-peptide agonists and antagonists specific to APJR. Apelin/elabela-activated APJR orchestrates major signaling pathways such as extracellular signal-regulated kinase (ERKs), protein kinase B (PKB/Akt), and p70S. This review focuses on the structural and functional characteristics of apelin, elabela, APJR, and their interactions involved in the binding and activation of the downstream signaling cascade. We also focus on the diverse signaling profile of APJR and its ligands and their involvement in various physiological systems.

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.

Inhibition of apelin/APJ axis enhances the potential of dendritic cell-based vaccination to modulate TH1 and TH2 cell-related immune responses in an animal model of metastatic breast cancer

PURPOSE

The immunosuppressive microenvironment of tumors reduces the effectiveness of immunotherapies. Apelin as an immunosuppressor peptide is expressed in the microenvironment of many tumors. Thus, inhibition of apelin-related protumor activities can promote the effectiveness of cancer immunotherapy. Here, we investigated the efficacy of a dendritic cell (DC) vaccine in combination with an apelin receptor antagonist, ML221, to modulate Th1 and Th2 cell-related responses in breast cancer-bearing mice.

MATERIALS AND METHODS

Tumor was induced in female BALB/c mice by injecting 7 ​× ​10⁵ 4T1 cells in the right flank. Tumor-bearing mice were then given PBS, ML221, DC vaccine and "ML221 + DC vaccine" for 21 days. On day 37, mice were sacrificed and the frequency of Th1/Th2 cells in spleen and serum levels of IFN-γ/IL-10 were determined using flow cytometry and ELISA, respectively. Lung metastasis was evaluated in lung tissues stained with hematoxylin and eosin. Finally, the obtained data were analyzed using appropriate statistical tests.

RESULTS

Combination therapy with ML221 + DC vaccination was more effective in reducing tumor growth (P ​< ​0.0001), preventing lung metastasis (P ​< ​0.0001) and increasing survival rate (P ​< ​0.01) compared to the control group. Moreover, combination treatment substantially increased the frequency of Th1 cells while decreasing the frequency of Th2 cells in the spleen compared to the control group (P ​< ​0.01). It also reduced serum levels of IL-10 compared with the control group (P ​< ​0.05).

CONCLUSION

Our findings showed that combination therapy using ML221 + DC vaccine can be considered as an effective cancer therapeutic program to potentiate anti-tumor immune responses.

Brain and Breast Cancer Cells with PTEN Loss of Function Reveal Enhanced Durotaxis and RHOB Dependent Amoeboid Migration Utilizing 3D Scaffolds and Aligned Microfiber Tracts

BACKGROUND

Glioblastoma multiforme (GBM) and metastatic triple-negative breast cancer (TNBC) with PTEN mutations often lead to brain dissemination with poor patient outcome, thus new therapeutic targets are needed. To understand signaling, controlling the dynamics and mechanics of brain tumor cell migration, we implemented GBM and TNBC cell lines and designed 3D aligned microfibers and scaffolds mimicking brain structures.

METHODS

3D microfibers and scaffolds were printed using melt electrowriting. GBM and TNBC cell lines with opposing PTEN genotypes were analyzed with RHO-ROCK-PTEN inhibitors and PTEN rescue using live-cell imaging. RNA-sequencing and qPCR of tumor cells in 3D with microfibers were performed, while scanning electron microscopy and confocal microscopy addressed cell morphology.

RESULTS

In contrast to the PTEN wildtype, GBM and TNBC cells with PTEN loss of function yielded enhanced durotaxis, topotaxis, adhesion, amoeboid migration on 3D microfibers and significant high RHOB expression. Functional studies concerning RHOB-ROCK-PTEN signaling confirmed the essential role for the above cellular processes.

CONCLUSIONS

This study demonstrates a significant role of the PTEN genotype and RHOB expression for durotaxis, adhesion and migration dependent on 3D. GBM and TNBC cells with PTEN loss of function have an affinity for stiff brain structures promoting metastasis. 3D microfibers represent an important tool to model brain metastasizing tumor cells, where RHO-inhibitors could play an essential role for improved therapy.

Melanoma Progression under Obesity: Focus on Adipokines

Simple Summary

Obesity is a rapidly growing public health problem and the reason for numerous diseases in the human body, including cancer. This article reviews the current knowledge of the effect of molecules secreted by adipose tissue-adipokines on melanoma progression. We also discuss the role of these factors as markers of incidence, metastasis, and melanoma patient survival. Understanding the functions of adipokines will lead to knowledge of whether and how obesity promotes melanoma growth.

Abstract

Obesity is a growing problem in the world and is one of the risk factors of various cancers. Among these cancers is melanoma, which accounts for the majority of skin tumor deaths. Current studies are looking for a correlation between obesity and melanoma. They suspect that a potential cause of its development is connected to the biology of adipokines, active molecules secreted by adipose tissue. Under physiological conditions, adipokines control many processes, including lipid and glucose homeostasis, insulin sensitivity, angiogenesis, and inflammations. However, when there is an increased amount of fat in the body, their secretion is dysregulated. This article reviews the current knowledge of the effect of adipokines on melanoma growth. This work focuses on the molecular pathways by which adipose tissue secreted molecules modify the angiogenesis, migration, invasion, proliferation, and death of melanoma cells. We also discuss the role of these factors as markers of incidence, metastasis, and melanoma patient survival. Understanding the functions of adipokines will lead to knowledge of whether and how obesity promotes melanoma growth. Further studies may contribute to the innovations of therapies and the use of adipokines as predictive and/or prognostic biomarkers.

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.

APLN: A potential novel biomarker for cervical cancer

Apelin (APLN) is recently demonstrated a direct association with many malignant diseases. However, its effects on cervical cancer remain unclear. This study therefore aims to evaluate the association between APLN expression and cervical cancer using publicly available data from The Cancer Genome Atlas (TCGA). The Pearson χ2 test and Fish exact test, as well as logistic regression, were used to evaluate the relationship between clinicopathological factors in cervical cancer and the expression of APLN. Additionally, the Cox regression and Kaplan-Meier methods were conducted to analyze the Overall Survival (OS) of cervical cancer patients in TCGA. Finally, gene set enrichment analysis (GSEA) was performed to establish its biological functions. High expression of APLN in cervical cancer was significantly associated with a more advanced clinical stage (OR = 1.91 (1.21-3.05) for Stage II, Stage III, and Stage IV vs Stage I, p = 0.006). Additionally, it was associated with poor outcome after primary therapy (OR = 2.14 (1.03-4.59) for Progressive Disease (PD), Stable Disease (SD), and Partial Response (PR) vs Complete Remission (CR), p = 0.045) and high histologic grade (OR = 1.67 (1.03-2.72) for G3 and G4 vs G1 and G2, p = 0.037). Moreover, multivariate analysis showed that high expression of APLN was associated with a shorter OS. GSEA demonstrated that six KEGG pathways, including PPAR signaling, ECM-receptor interaction, focal adhesion, MAPK signaling, TGF-beta signaling, and Gap junction pathways were differentially enriched in the high expression APLN phenotype. The recent study suggests that APLN plays an important role in the progression of cervical cancer and might be a promising prognostic biomarker of the disease.

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.

A Fluorescent Gelatin Degradation Assay to Study Melanoma Breakdown of Extracellular Matrix

In order to protrude within a dense tissue, tumor cells have to develop the ability to digest the extracellular matrix (ECM). Melanoma cells, similarly to other types of tumor cells, form invadopodia, membranous invaginations rich in filamentous actin and several other proteins including matrix metalloproteinases (MMPs). MMPs degrade ECM structural proteins such as collagens, fibronectin, or laminin. Here we describe an assay that allows the detection of gelatinase activity exhibited by tumor cells under 2D conditions and methods to present obtained data in both a quantitative and a qualitative manner.

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.

Computational/experimental evaluation of liver metastasis post hepatic injury: interactions with macrophages and transitional ECM

The complex interactions between subclinical changes to hepatic extracellular matrix (ECM) in response to injury and tumor-associated macrophage microenvironmental cues facilitating metastatic cell seeding remain poorly understood. This study implements a combined computational modeling and experimental approach to evaluate tumor growth following hepatic injury, focusing on ECM remodeling and interactions with local macrophages. Experiments were performed to determine ECM density and macrophage-associated cytokine levels. Effects of ECM remodeling along with macrophage polarization on tumor growth were evaluated via computational modeling. For primary or metastatic cells in co-culture with macrophages, TNF-α levels were 5× higher with M1 vs. M2 macrophages. Metastatic cell co-culture exhibited 10× higher TNF-α induction than with primary tumor cells. Although TGFβ1 induction was similar between both co-cultures, levels were slightly higher with primary cells in the presence of M1. Simulated metastatic tumors exhibited decreased growth compared to primary tumors, due to high local M1-induced cytotoxicity, even in a highly vascularized microenvironment. Experimental analysis combined with computational modeling may provide insight into interactions between ECM remodeling, macrophage polarization, and liver tumor growth.

Evaluation of Apelin and Apelin Receptor Level in the Primary Tumor and Serum of Colorectal Cancer Patients

Colorectal cancer is the second deadliest tumor, which has a positive correlation with obesity which led to increasing interest in the relationship between adipokines and cancer progression. Apelin is a secreted peptide involved in regulation of tumor progression and invasiveness. In this study, we examined apelin and apelin receptor expression level in colorectal cancer. Apelin, and its receptor mRNA, and protein expression levels were measured in tumor tissue of 56 surgically treated colorectal adenocarcinoma (CRC) patients. We also analyzed apelin and apelin receptor protein levels in sera of 56 CRC patients and 27 healthy controls. The mRNA and protein level of this peptide and its receptor was higher in tumors than that in control tissue. Serum levels of apelin and apelin receptor were increased in CRC patients in comparison to controls. The concentration of serum apelin level significantly increased in individuals with lymph node and distant metastasis. Obtained results suggest that apelin could be an important factor in progression of colorectal carcinoma.