Vasculogenic mimicry is a marker of poor prognosis in prostate cancer

Vascular mimicry in zebrafish fin regeneration: how macrophages build new blood vessels

Vascular mimicry has been thoroughly investigated in tumor angiogenesis. In this study, we demonstrate for the first time that a process closely resembling tumor vascular mimicry is present during physiological blood vessel formation in tissue regeneration using the zebrafish fin regeneration assay. At the fin-regenerating front, vasculature is formed by mosaic blood vessels with endothelial-like cells possessing the morphological phenotype of a macrophage and co-expressing both endothelial and macrophage markers within single cells. Our data demonstrate that the vascular segments of the regenerating tissue expand, in part, through the transformation of adjacent macrophages into endothelial-like cells, forming functional, perfused channels and contributing to the de novo formation of microvasculature. Inhibiting the formation of tubular vascular-like structures by CVM-1118 prevents vascular mimicry and network formation resulting in a 70% shorter regeneration area with 60% reduced vessel growth and a complete absence of any signs of regeneration in half of the fin area. Additionally, this is associated with a significant reduction in macrophages. Furthermore, depleting macrophages using macrophage inhibitor PLX-3397, results in impaired tissue regeneration and blood vessel formation, namely a reduction in the regeneration area and vessel network by 75% in comparison to controls.

Hypomethylation-associated LINC00987 downregulation induced lung adenocarcinoma progression by inhibiting the phosphorylation-mediated degradation of SND1

DNA methylation, an epigenetic regulatory mechanism dictating gene transcription, plays a critical role in the occurrence and development of cancer. However, the molecular underpinnings of LINC00987 methylation in the regulation of lung adenocarcinoma (LUAD) remain elusive. This study investigated LINC00987 expression in LUAD patients through analysis of The Cancer Genome Atlas data sets. Quantitative real-time polymerase chain reaction (RT-qPCR) and fluorescence in situ hybridization assays were used to assess LINC00987 expression in LUAD. The bisulfite genomic sequence PCR (BSP) assay was used to determine the methylation levels of the LINC00987 promoter. The interaction between LINC00987 and SND1 was elucidated via immunoprecipitation and RNA pull-down assays. The functional significance of LINC00987 and SND1 in Calu-3 and NCI-H1688 cells was evaluated in vitro through CCK-8, EdU, Transwell, flow cytometry, and vasculogenic mimicry (VM) tube formation assays. LINC00987 expression decreased in LUAD concomitant with hypermethylation of the promoter region, while hypomethylation of the LINC00987 promoter in LUAD tissues correlated with tumor progression. Treatment with 5-Aza-CdR augmented LINC00987 expression and inhibited tumor growth. Mechanistically, LINC00987 overexpression impeded LUAD progression and VM through direct binding with SND1, thereby facilitating its phosphorylation and subsequent degradation. Additionally, overexpression of SND1 counteracted the adverse effects of LINC00987 downregulation on cell proliferation, apoptosis, cell migration, invasion, and VM in LUAD in vitro. In conclusion, this pioneering study focuses on the expression and function of LINC00987 and reveals that hypermethylation of the LINC00987 gene may contribute to LUAD progression. LINC00987 has emerged as a potential tumor suppressor gene in tumorigenesis through its binding with SND1 to facilitate its phosphorylation and subsequent degradation.

HSP27 promotes vasculogenic mimicry formation in human salivary adenoid cystic carcinoma via the AKT-MMP-2/9 pathway

PURPOSE

To explore the role and mechanism of heat shock protein 27 (HSP27) in SACC VM formation.

STUDY DESIGN

Immunohistochemistry and double staining with cluster of differentiation 31 (CD31) and periodic acid-Schiff (PAS) were used to detect HSP27 expression and VM in 70 SACC tissue samples separately. Quantitative real-time polymerase chain reaction (qRT-PCR), western blot analysis, and immunofluorescence were used to detect gene and protein expression. HSP27 in SACC cells were overexpression or downregulated by transfecting HSP27 or short hairpin RNA target HSP27 (sh-HSP27). The migration and invasion abilities of SACC cells were detected using wound healing and Transwell invasion assays. The VM formation ability of the cells in vitro was detected using a Matrigel 3-dimensional culture.

RESULTS

HSP27 expression was positively correlated with VM formation and affected the prognosis of patients. In vitro, HSP27 upregulation engendered VM formation and the invasion and migration of SACC cells. Mechanistically, HSP27 upregulation increased Akt phosphorylation and subsequently increased downstream matrix metalloproteinase 2 and 9 expressions.

CONCLUSION

HSP27 may plays an important role in VM formation in SACC via the AKT-MMP-2/9 signalling pathway.

Vascular mimicry as a facilitator of melanoma brain metastasis

Melanoma has the highest propensity among solid tumors to metastasize to the brain. Melanoma brain metastases (MBM) are a leading cause of death in melanoma and affect 40-60% of patients with late-stage disease. Therefore, uncovering the molecular mechanisms behind MBM is necessary to enhance therapeutic interventions. Vascular mimicry (VM) is a form of neovascularization linked to invasion, increased risk of metastasis, and poor prognosis in many tumor types, but its significance in MBM remains poorly understood. We found that VM density is elevated in MBM compared to paired extracranial specimens and is associated with tumor volume and CNS edema. In addition, our studies indicate a relevant role of YAP and TAZ, two transcriptional co-factors scarcely studied in melanoma, in tumor cell-vasculogenesis and in brain metastasis. We recently demonstrated activation of the Hippo tumor suppressor pathway and increased degradation of its downstream targets YAP and TAZ in a metastasis impaired cell line model. In the current study we establish the utility of anti-YAP/TAZ therapy in mouse models of metastatic melanoma whereby treatment effectively inhibits VM and prolongs survival of mice with MBM. The data presented herein suggest that VM may be an important and targetable mechanism in melanoma and that VM inhibition might be useful for treating MBM, an area of high unmet clinical need, thus having important implications for future treatment regimens for these patients.

Development of a novel vasculogenic mimicry-associated gene signature for the prognostic assessment of osteosarcoma patients

BACKGROUND

Osteosarcoma (OS) is a form of primary bone malignancy associated with poor prognostic outcomes. Recent work has highlighted vasculogenic mimicry (VM) as a key mechanism that supports aggressive tumor growth. The patterns of VM-associated gene expression in OS and the relationship between these genes and patient outcomes, however, have yet to be defined.

METHODS

Here, 48 VM-related genes were systematically assessed to examine correlations between the expression of these genes and OS patient prognosis in the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) cohort. Patients were classified into three OS subtypes. Differentially expressed genes for these three OS subtypes were then compared with hub genes detected in a weighted gene co-expression network analysis, leading to the identification of 163 overlapping genes that were subject to further biological activity analyses. A three-gene signature (CGREF1, CORT, and GALNT14) was ultimately constructed through a least absolute shrinkage and selection operator Cox regression analysis, and this signature was used to separate patients into low- and high-risk groups. The K-M survival analysis, receiver operating characteristic analysis, and decision curve analysis were adopted to evaluate the prognostic prediction performance of the signature. Furthermore, the expression patterns of three genes derived from the prognostic model were validated by quantitative real-time polymerase chain reaction (RT-qPCR).

RESULTS

VM-associated gene expression patterns were successfully established, and three VM subtypes of OS that were associated with patient prognosis and copy number variants were defined. The developed three-gene signature was constructed, which served as independent prognostic markers and prediction factors for the clinicopathological features of OS. Finally, lastly, the signature may also have a guiding effect on the sensitivity of different chemotherapeutic drugs.

CONCLUSION

Overall, these analyses facilitated the development of a prognostic VM-associated gene signature capable of predicting OS patient outcomes. This signature may be of value for both studies of the mechanistic basis for VM and clinical decision-making in the context of OS patient management.

Prostate Cancer Microvascular Routes: Exploration and Measurement Strategies

Angiogenesis is acknowledged as a pivotal feature in the pathology of human cancer. Despite the absence of universally accepted markers for gauging the comprehensive angiogenic activity in prostate cancer (PCa) that could steer the formulation of focused anti-angiogenic treatments, the scrutiny of diverse facets of tumoral blood vessel development may furnish significant understanding of angiogenic processes. Malignant neoplasms, encompassing PCa, deploy a myriad of strategies to secure an adequate blood supply. These modalities range from sprouting angiogenesis and vasculogenesis to intussusceptive angiogenesis, vascular co-option, the formation of mosaic vessels, vasculogenic mimicry, the conversion of cancer stem-like cells into tumor endothelial cells, and vascular pruning. Here we provide a thorough review of these angiogenic mechanisms as they relate to PCa, discuss their prospective relevance for predictive and prognostic evaluations, and outline the prevailing obstacles in quantitatively evaluating neovascularization via histopathological examinations.

Update on Radiotherapy Changes of Nasopharyngeal Carcinoma Tumor Microenvironment

The utilization of radiotherapy (RT) serves as the principal approach for managing nasopharyngeal carcinoma (NPC). Consequently, it is imperative to investigate the correlation between the radiation microenvironment and radiation resistance in NPC. PubMed and China National Knowledge Infrastructure (CNKI) databases were accessed to perform a search utilizing the English keywords "nasopharyngeal cancer", "radiotherapy", and "microenvironment". The search time spanned from the establishment of the database until January 20, 2023. A total of 82 articles were included. The post-radiation tumor microenvironment (TME), or the radiation microenvironment, includes several components, such as the radiation-immune microenvironment and the radiation-hypoxic microenvironment. The radiation-immune microenvironment includes various factors like immune cells, signaling molecules, and extracellular matrix. RT can reshape the TME, leading to immune responses with both cytotoxic effects (T cells, B cells, natural killer (NK) cells) and immune escape mechanisms (regulatory T cells (Tregs), macrophages). RT enhances immune responses through DNA release, type I interferons, and immune cell recruitment. Radiation-hypoxic microenvironment affects metabolism and molecular changes. RT-induced hypoxia causes vascular changes, fibrosis, and vessel compression, leading to tissue hypoxia. Hypoxia activates hypoxia-inducible factor (HIF)-1α/2α, promoting angiogenesis and glycolysis in tumor cells. TME changes due to hypoxia also involve immune suppressive cells like myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and Tregs. The radiation microenvironment is involved in radiation resistance and holds a significant effect on the prognosis of patients with NPC. Exploring the radiation microenvironment provides new insights into RT and NPC research.

Therapeutic potential of vasculogenic mimicry in urological tumors

Angiogenesis is an essential process in the growth and metastasis of cancer cells, which can be hampered by an anti-angiogenesis mechanism, thereby delaying the progression of tumors. However, the benefit of this treatment modality could be restricted, as most patients tend to develop acquired resistance during treatment. Vasculogenic mimicry (VM) is regarded as a critical alternative mechanism of tumor angiogenesis, where studies have demonstrated that patients with tumors supplemented with VM generally have a shorter survival period and a poorer prognosis. Inhibiting VM may be an effective therapeutic strategy to prevent cancer progression, which could prove helpful in impeding the limitations of lone use of anti-angiogenic therapy when performed concurrently with other anti-tumor therapies. This review summarizes the mechanism of VM signaling pathways in urological tumors, i.e., prostate cancer, clear cell renal cell carcinoma, and bladder cancer. Furthermore, it also summarizes the potential of VM as a therapeutic strategy for urological tumors.

Microbiota-Derived Natural Products Targeting Cancer Stem Cells: Inside the Gut Pharma Factory

Cancer stem cells (CSCs) have drawn much attention as important tumour-initiating cells that may also be crucial for recurrence after chemotherapy. Although the activity of CSCs in various forms of cancer is complex and yet to be fully elucidated, opportunities for therapies targeting CSCs exist. CSCs are molecularly distinct from bulk tumour cells, so they can be targeted by exploiting their signature molecular pathways. Inhibiting stemness has the potential to reduce the risk posed by CSCs by limiting or eliminating their capacity for tumorigenesis, proliferation, metastasis, and recurrence. Here, we briefly described the role of CSCs in tumour biology, the mechanisms involved in CSC therapy resistance, and the role of the gut microbiota in cancer development and treatment, to then review and discuss the current advances in the discovery of microbiota-derived natural compounds targeting CSCs. Collectively, our overview suggests that dietary intervention, toward the production of those identified microbial metabolites capable of suppressing CSC properties, is a promising approach to support standard chemotherapy.

Resveratrol suppresses serum-induced vasculogenic mimicry through impairing the EphA2/twist-VE-cadherin/AKT pathway in human prostate cancer PC-3 cells

Vasculogenic mimicry (VM) is closely related to cancer progression and metastasis, contributing to poor prognosis in patients with cancer. Resveratrol (RES) is well known to possess anti-cancer activity. This study explored the new role of RES in VM incidence in human prostate cancer (PCa) PC-3 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, transwell invasion, and three-dimensional culture VM tube formation assays were performed to check the cell viability, invasive ability, and vessel-like networks formation, respectively. VM-related proteins were detected by Western blots. The activity of metalloproteinase-2 (MMP-2) was identified by gelatin zymography. Vascular endothelial cadherin (VE-cadherin) mRNA was assessed by reverse transcriptase-polymerase chain reaction. Nuclear twist expression was observed by immunofluorescence assay. RES reduced serum-induced invasion and VM formation. Serum-induced phosphorylation of erythropoiethin-producing hepatoceullular A2 (EphA2) and the expression of VE-cadherin at the protein and mRNA levels were decreased after RES treatment. RES inhibited serum-induced expression and nuclear localization of twist. Serum-activated AKT signaling pathway, including MMP-2 and laminin subunit 5 gamma-2, was impaired by RES. These results suggested that RES may have an anti-VM effect through suppressing the EphA2/twist-VE-cadherin/AKT signaling cascade in PCa PC-3 cells.

Oberley-Deegan R. CT vs. bioluminescence: A comparison of imaging techniques for orthotopic prostate tumors in mice

Prostate cancer is one of the most diagnosed cancers in men in the United States. In mouse models, orthotopic tumors are favored for their biological relevance and simulation of growth in a microenvironment akin to that found in humans. However, to monitor the disease course, animal models require consistent and noninvasive surveillance. In vivo bioluminescent imaging has become a mainstay imaging modality due to its flexibility and ease of use. However, with some orthotopic prostate tumor models, bioluminescence fails to describe disease progression due to optical scattering and signal attenuation. CT scanning, in addition to its utility in human cancer diagnosis and surveillance, can be applied to mouse models with improved results. However, CT imaging has poor definition when imaging soft tissues and is not routinely used in prostate cancer models. Using an orthotopic prostate cancer model, our results demonstrate that, when compared to bioluminescent imaging, CT imaging correlates more closely to orthotopic prostate tumor growth in mice. Based on the data from this study, we conclude that CT imaging can be used as an alternative to the more commonly used bioluminescent imaging for measuring orthotopic prostate cancer growth over time.

Vandetanib alters the tumoricidal capacity of human breast cancer stem cells via inhibiting vasculogenic capacity

Introduction

The inhibition of vascularization into tumor stroma as well as dynamic cell growth is the center of attention. Here, we aimed to examine the role of vandetanib on angiogenesis capacity of breast cancer stem cell (CSCs).

Methods

MDA-MB-231 cells were exposed to different doses of vandetanib and survival rate was monitored. Stimulatory effects of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and epidermal growth factor (EGF) were evaluated in vandetanib-treated MDA-MB-231 cells. In vitro tubulogenesis capacity was studied on the Matrigel surface. The synergistic effects of vandetanib on cell survival were also assessed after PI3K and/or Wnt3a inhibition. Vascular endothelial (VE)-cadherin, matrix metalloproteinase-2 (MMP-2), -9, Wnt3a, and p-Akt/Akt ratio were measured using western blotting.

Results

Vandetanib reduced survival rate in a dose-dependent manner (P<0.05). Proliferative effects associated with VEGF, FGF, and EGF were blunted in these cells pre-exposed to vandetanib (P<0.05). The microcirculation pattern's triple-negative breast cancer (TNBC) was suppressed by 1, 5 µM of vandetanib (P<0.05). Hence 1, 5 µM of vandetanib potentially decreased the population of CD24- cells. 1 and 5 µM of vandetanib inhibited cell proliferation by blocking PI3K and Wnt3a pathways and decreased the p-Akt/Akt ratio, Wnta3 protein levels (P<0.05). 1 and 5 µM vandetanib combined with PI3K inhibitor diminished metastatic markers including, MMP-2, and MMP-9. The concurrent treatment (PI3K, inhibitor+ 1, 5 µM vandetanib) also considerably reduced epithelial-mesenchymal transition (EMT) markers such as VE-cadherin (P<0.05).

Conclusion

Vandetanib suppressed vasculogenic mimicry (VM) networking through blunting stemness properties, coincided with suppression of VE-cadherin in CSCs.

SPHK/HIF-1α Signaling Pathway Has a Critical Role in Chrysin-Induced Anticancer Activity in Hypoxia-Induced PC-3 Cells

Hypoxia, a typical feature of locally advanced solid tumors including prostate cancer, is a critical contributor to tumor progression and causes resistance to therapy. In this study, we investigated the effects of chrysin on tumor progression in hypoxic PC-3 cells. Chrysin exerted a significant inhibitory effect on 3D cell growth under normoxic and hypoxic conditions. It also decreased the hypoxia-induced vasculogenic mimicry and attenuated the expression of HIF-1α and VE-cadherin. Chrysin inhibited HIF-1α accumulation in a concentration- and time-dependent manner in hypoxic PC-3 cells, while also suppressing the expression of HIF-1α by inhibiting SPHK-1 in both CoCl₂ and hypoxic PC-3 cells. At high concentrations of chrysin, there was a greater increase in apoptosis in the hypoxic cells compared to that in normoxic cells, which was accompanied by sub-G1 phase arrest. Chrysin-induced apoptosis inhibited VEGF and Bcl-2 and induced the cleavage of PARP and caspase-3. SPHK-1 knockdown induced apoptosis and inhibited epithelial–mesenchymal transition. Consistent with the in vitro data, 50 mg/kg of chrysin suppressed the tumor growth of PC-3 xenografts by 80.4% compared to that in the untreated control group. The immunohistochemistry of tumor tissues revealed decreased Ki-67, HIF-1α, and VEGF expression in the chrysin-treated group compared to an untreated control. Western blotting data for tumor tissues showed that chrysin treatment decreased SPHK-1, HIF-1α, and PARP expression while inducing caspase-3 cleavage. Overall, our findings suggest that chrysin exerts anti-tumor activity by inhibiting SPHK-1/HIF-1α signaling and thus represents a potent chemotherapeutic agent for hypoxia, which promotes cancer progression and is related to poor prognoses in prostate cancer patients.

Reassessing vascular endothelial growth factor (VEGF) in anti-angiogenic cancer therapy

Vascularization is fundamental to the growth and spread of tumor cells to distant sites. As a consequence, angiogenesis, the sprouting of new blood vessels from existing ones, is a characteristic trait of cancer. In 1971, Judah Folkman postulated that tumour growth is angiogenesis dependent and that by cutting off blood supply, a neoplastic lesion could be potentially starved into remission. Decades of research have been devoted to understanding the role that vascular endothelial growth factor (VEGF) plays in tumor angiogenesis, and it has been identified as a significant pro-angiogenic factor that is frequently overexpressed within a tumor mass. Today, anti-VEGF drugs such as Sunitinib, Sorafenib, Axitinib, Tanibirumab, and Ramucirumab have been approved for the treatment of advanced and metastatic cancers. However, anti-angiogenic therapy has turned out to be more complex than originally thought. The failure of this therapeutic option calls for a reevaluation of VEGF as the major target in anti-angiogenic cancer therapy. The call for reassessment is based on two rationales: first, tumour blood vessels are abnormal, disorganized, and leaky; this not only prevents optimal drug delivery but it also promotes hypoxia and metastasis; secondly, tumour growth or regrowth might be blood vessel dependent and not angiogenesis dependent as tumour cells can acquire blood vessels via non-angiogenic mechanisms. Therefore, a critical assessment of VEGF, VEGFRs, and their inhibitors could glean newer options such as repurposing anti-VEGF drugs as vascular normalizing agents to enhance drug delivery of immune checkpoint inhibitors.

EBV-Induced CXCL8 Upregulation Promotes Vasculogenic Mimicry in Gastric Carcinoma via NF-κB Signaling

Epstein–Barr virus (EBV)-associated gastric carcinoma (EBVaGC) is a distinct entity with a conspicuous tumor microenvironment compared with EBV-negative gastric carcinoma. However, the exact role of EBV in gastric carcinogenesis remains elusive. In the present study, we found that EBV upregulated CXCL8 expression, and CXCL8 significantly promoted vasculogenic mimicry (VM) formation of gastric carcinoma (GC) cells. In accordance with these observations, overexpression of CXCL8 increased cell proliferation and migration of AGS and BGC823 cells, while knockdown of CXCL8 with siRNA inhibited cell proliferation and migration of AGS-EBV cells. In addition, activation of NF-κB signaling was involved in VM formation induced by CXCL8, which was blocked by NF-κB inhibitors BAY 11-7082 and BMS345541. Furthermore, EBV-encoded lncRNA RPMS1 activated the NF-κB signaling cascade, which is responsible for EBV-induced VM formation. Both xenografts and clinical samples of EBVaGC exhibit VM histologically, which are correlated with CXCL8 overexpression. Finally, CXCL8 is positively correlated with overall survival in GC patients. In conclusion, EBV-upregulated CXCL8 expression promotes VM formation in GC via NF-κB signaling, and CXCL8 might serve as a novel anti-tumor target for EBVaGC.

Orchestrated expression of vasculogenic mimicry and laminin-5γ2 is an independent prognostic marker in oral squamous cell carcinoma

Vasculogenic mimicry (VM), an endothelial cell-independent alternative mechanism of blood supply to the malignant tumour, has long been considered as an adverse prognostic factor in many cancers. The correlation of VM with laminin-5γ2 and the assessment of their harmonized expression as an independent risk factor have not been elucidated yet in oral squamous cell carcinoma (OSCC). CD31/PAS staining stratified 116 clinically diagnosed OSCC specimens into VM+ and VM- cohorts. The expression pattern of laminin-5γ2 and its upstream modulator MMP2 was evaluated by immunohistochemistry and Western blot. The Kaplan-Meier and Cox regression analyses were performed to assess the survival and prognostic implications. The presence of VM demonstrated a significant correlation with the expression of laminin-5γ2 (p < .001) and MMP2 (p < .001). This pattern was mirrored by the significant upregulation of laminin-5γ2 and MMP2 in VM+ cohorts compared with the VM- ones. Furthermore, co-expression of VM and laminin-5γ2 was significantly associated with tumour grade (p = .010), primary tumour size (p < .001), lymph node metastasis (p = .001) and TNM stages (p < .001) but not with patients' age, gender, tobacco and alcohol consumption habit. Vasculogenic mimicry and laminin-5γ2 double-positive cohort displayed a significantly poorer disease-free survival (DFS) and overall survival (OS). Vasculogenic mimicry, laminin-5γ2 and their subsequent dual expression underlie a significant prognostic value for DFS [hazard ratio (HR) = 9.896, p = .028] and OS [HR = 21.401, p = .033] in OSCC patients. Together, our findings imply that VM along with laminin-5γ2 is strongly linked to the malignant progression in OSCC and VM and laminin-5γ2 coordination emerges as a critical prognostic biomarker for OSCC.

Sp1 Plays a Key Role in Vasculogenic Mimicry of Human Prostate Cancer Cells

Sp1 transcription factor regulates genes involved in various phenomena of tumor progression. Vasculogenic mimicry (VM) is the alternative neovascularization by aggressive tumor cells. However, there is no evidence of the relationship between Sp1 and VM. This study investigated whether and how Sp1 plays a crucial role in the process of VM in human prostate cancer (PCa) cell lines, PC-3 and DU145. A cell viability assay and three-dimensional culture VM tube formation assay were performed. Protein and mRNA expression levels were detected by Western blot and reverse transcriptase-polymerase chain reaction, respectively. The nuclear twist expression was observed by immunofluorescence assay. A co-immunoprecipitation assay was performed. Mithramycin A (MiA) and Sp1 siRNA significantly decreased serum-induced VM, whereas Sp1 overexpression caused a significant induction of VM. Serum-upregulated vascular endothelial cadherin (VE-cadherin) protein and mRNA expression levels were decreased after MiA treatment or Sp1 silencing. The protein expression and the nuclear localization of twist were increased by serum, which was effectively inhibited after MiA treatment or Sp1 silencing. The interaction between Sp1 and twist was reduced by MiA. On the contrary, Sp1 overexpression enhanced VE-cadherin and twist expressions. Serum phosphorylated AKT and raised matrix metalloproteinase-2 (MMP-2) and laminin subunit 5 gamma-2 (LAMC2) expressions. MiA or Sp1 silencing impaired these effects. However, Sp1 overexpression upregulated phosphor-AKT, MMP-2 and LAMC2 expressions. Serum-upregulated Sp1 was significantly reduced by an AKT inhibitor, wortmannin. These results demonstrate that Sp1 mediates VM formation through interacting with the twist/VE-cadherin/AKT pathway in human PCa cells.

Evaluation of Pharmaceutical Inhibition of Vasculogenic Mimicry In Vitro

Vasculogenic mimicry formation is generally assessed using three-dimensional (3D) cultures of aggressive tumor cells grown over an extended incubation period. Test agents can be introduced during growth of the 3D cultures to determine their effect on vasculogenic mimicry formation. Here, we describe the protocol for evaluation of the inhibitory effect of drugs on vasculogenic mimicry in vitro using bright-field and fluorescence microscopy on 3D cultures of tumor cells grown in Matrigel.

Histochemical Staining of Vasculogenic Mimicry

Vasculogenic mimicry (VM) describes a new tumor microvascular paradigm of non-endothelial cells, where aggressive cancer cells independent of angiogenesis acquire the ability to fluid-conducting vessels. VM shows worse 5-year overall survival in cancer that suggesting that VM could be a promising surgical and effective adjuvant therapy strategy in prognostics of metastatic cancer patients. The current chapter is a comprehensive review on "Main Staining Methods and Protocols in Vasculogenic Mimicry." Here, we provide most up-to-date and detailed information upon microscopy and histology protocols for the identification and understanding of VM process in both in vitro and in vivo.

Novel Pathways for Targeting Tumor Angiogenesis in Metastatic Breast Cancer

Breast cancer is the most common cancer affecting women and is the second leading cause of cancer related death worldwide. Angiogenesis, the process of new blood vessel development from pre-existing vasculature, has been implicated in the growth, progression, and metastasis of cancer. Tumor angiogenesis has been explored as a key therapeutic target for decades, as the blockade of this process holds the potential to reduce the oxygen and nutrient supplies that are required for tumor growth. However, many existing anti-angiogenic approaches, such as those targeting Vascular Endothelial Growth Factor, Notch, and Angiopoietin signaling, have been associated with severe side-effects, limited survival advantage, and enhanced cancer regrowth rates. To address these setbacks, alternative pathways involved in the regulation of tumor angiogenesis are being explored, including those involving Bone Morphogenetic Protein-9 signaling, the Sonic Hedgehog pathway, Cyclooxygenase-2, p38-mitogen-activated protein kinase, and Chemokine Ligand 18. This review article will introduce the concept of tumor angiogenesis in the context of breast cancer, followed by an overview of current anti-angiogenic therapies, associated resistance mechanisms and novel therapeutic targets.

The emerging roles of circular RNAs in vessel co-option and vasculogenic mimicry: clinical insights for anti-angiogenic therapy in cancers

Unexpected resistance to anti-angiogenic treatment prompted the investigation of non-angiogenic tumor processes. Vessel co-option (VC) and vasculogenic mimicry (VM) are recognized as primary non-angiogenic mechanisms. In VC, cancer cells utilize pre-existing blood vessels for support, whereas in VM, cancer cells channel and provide blood flow to rapidly growing tumors. Both processes have been implicated in the development of tumor and resistance to anti-angiogenic drugs in many tumor types. The morphology, but rare molecular alterations have been investigated in VC and VM. There is a pressing need to better understand the underlying cellular and molecular mechanisms. Here, we review the emerging circular RNA (circRNA)-mediated regulation of non-angiogenic processes, VC and VM.

An Update on Molecular Pathways Regulating Vasculogenic Mimicry in Human Osteosarcoma and Their Role in Canine Oncology

Canine tumors are valuable comparative models for human counterparts, especially to explore novel biomarkers and to understand pathways and processes involved in metastasis. Vasculogenic mimicry (VM) is a unique property of malignant cancer cells which promote metastasis. Thus, it represents an opportunity to investigate both the molecular mechanisms and the therapeutic targets of a crucial phenotypic malignant switch. Although this biological process has been largely investigated in different human cancer types, including osteosarcoma, it is still largely unknown in veterinary pathology, where it has been mainly explored in canine mammary tumors. The presence of VM in human osteosarcoma is associated with poor clinical outcome, reduced patient survival, and increased risk of metastasis and it shares the main pathways involved in other type of human tumors. This review illustrates the main findings concerning the VM process in human osteosarcoma, search for the related current knowledge in canine pathology and oncology, and potential involvement of multiple pathways in VM formation, in order to provide a basis for future investigations on VM in canine tumors.

Molecular and clinical insights of matrix metalloproteinases into cancer spread and potential therapeutic interventions

Matrix metalloproteinases (MMPs) are the group of enzymes that belong to the family of zinc dependent endopeptidases. These proteases degrade collagen and other important proteins in extracellular matrix (ECM) and regulate cytoskeletal proteins, growth factors, chemokines and cytokines, thereby play significant role during organogenesis and normal tissue turnover. Recent studies highlight the tumorigenic functions of MMPs by modulating tumor microenvironment. Dysregulated MMPs/TIMPs cause an imbalance in crucial cell signals, and lead to serious pathological conditions related to inflammation, uncontrolled cell growth, ECM degradation, increased cell migration, cell death resistance, replicative immortality and the establishment of metastatic niche at secondary sites. Recently established correlation between the higher expression of active MMPs and cancer aggressiveness makes them probable target candidate of cancer diagnosis, prognosis and therapy. The present review focuses on the tumourigenic functions of MMPs and recent advancements in the development of MMP inhibitors of therapeutic potential in cancer treatment.

Grading Evolution and Contemporary Prognostic Biomarkers of Clinically Significant Prostate Cancer

Simple Summary

Prostate cancer treatment decisions are based on clinical stage and histological diagnosis, including Gleason grading assessed by a pathologist, in biopsies. Prior to staging and grading, serum or blood prostate-specific antigen (PSA) levels are measured and often trigger diagnostic examinations. However, PSA is best suited as a marker of cancer relapse after initial treatment. In this review, we first narratively describe the evolution of histological grading, the current status of Gleason pattern-based diagnostics and glance into future methodology of risk assessment by histological examination. In the second part, we systematically review the biomarkers that have been shown, independent from clinical characteristics, to correlate with clinically relevant end-points, i.e., occurrence of metastases, disease-specific mortality and overall survival after initial treatment of localized prostate cancer.

Abstract

Gleason grading remains the strongest prognostic parameter in localized prostate adenocarcinoma. We have here outlined the evolution and contemporary practices in pathological evaluation of prostate tissue samples for Gleason score and Grade group. The state of more observer-independent grading methods with the aid of artificial intelligence is also reviewed. Additionally, we conducted a systematic review of biomarkers that hold promise in adding independent prognostic or predictive value on top of clinical parameters, Grade group and PSA. We especially focused on hard end points during the follow-up, i.e., occurrence of metastasis, disease-specific mortality and overall mortality. In peripheral blood, biopsy-detected prostate cancer or in surgical specimens, we can conclude that there are more than sixty biomarkers that have been shown to have independent prognostic significance when adjusted to conventional risk assessment or grouping. Our search brought up some known putative markers and panels, as expected. Also, the synthesis in the systematic review indicated markers that ought to be further studied as part of prospective trials and in well characterized patient cohorts in order to increase the resolution of the current clinico-pathological prognostic factors.

Oncometabolite L-2-hydroxyglurate directly induces vasculogenic mimicry through PHLDB2 in renal cell carcinoma

Metabolism reprograming is a hallmark of cancer and plays an important role in tumor progression. The aberrant metabolism in renal cell carcinoma (RCC) leads to accumulation of the oncometabolite l‐2‐hydroxyglurate (L‐2HG). L‐2HG has been reported to inhibit the activity of some α‐ketoglutarate‐dependent dioxygenases such as TET enzymes, which mediate epigenetic alteration, including DNA and histone demethylation. However, the detailed functions of L‐2HG in renal cell carcinoma have not been investigated thoroughly. In our study, we found that L‐2HG was significantly elevated in tumor tissues compared to adjacent tissues. Furthermore, we demonstrated that L‐2HG promoted vasculogenic mimicry (VM) in renal cancer cell lines through reducing the expression of PHLDB2. A mechanism study revealed that activation of the ERK1/2 pathway was involved in L‐2HG‐induced VM formation. In conclusion, these findings highlighted the pathogenic link between L‐2HG and VM and suggested a novel therapeutic target for RCC.

What's new?

Metabolic reprograming, a hallmark of cancer, influences tumor progression. In the case of renal cell carcinoma (RCC) specifically, progression appears to be facilitated by the oncometabolite L‐2‐hydroxyglurate (L‐2HG), though underlying mechanisms remain enigmatic. Here, the authors investigated the ability of L‐2HG in RCC to promote vasculogenic mimicry (VM), in which aggressive cancer cells form vessel‐like networks that support tumor growth. Analyses of RCC patient tissues revealed elevated L‐2HG levels, wherein tumor cells with greater L‐2HG levels exhibited more VM structures. TCGA data and high‐throughput sequencing analyses further show that L‐2HG contributes to VM formation via reduction of PHLDB2 levels.

Vascular mimicry: Triggers, molecular interactions and in vivo models

Vascular mimicry is induced by a wide array of genes with functions related to cancer stemness, hypoxia, angiogenesis and autophagy. Vascular mimicry competent (VM-competent) cells that form de novo blood vessels are common in solid tumors facilitating tumor cell survival and metastasis. VM-competent cells display increased levels of vascular mimicry selecting for stem-like cells in an O₂-gradient-dependent manner in deeply hypoxic tumor regions, while also aiding in maintaining tumor cell metabolism and stemness. Three of the principal drivers of vascular mimicry are EphA2, Nodal and HIF-1α, however, directly or indirectly many of these molecules affect VE-Cadherin (VE-Cad), which forms gap-junctions to bind angiogenic blood vessels together. During vascular mimicry, the endothelial-like functions of VM-competent cancer stem cells co-opt VE-Cad to bind cancer cells together to create cancer cell-derived blood conducting vessels. This process potentially compensates for the lack of access to blood and nutrient in avascular tumors, simultaneously providing nutrients and enhancing cancer invasion and metastasis. Current evidence also supports that vascular mimicry promotes cancer malignancy and metastasis due to the cooperation of oncogenic signaling molecules driving cancer stemness and autophagy. While a number of currently used cancer therapeutics are effective inhibitors of vascular mimicry, developing a new class of vascular mimicry specific inhibitors could allow for the treatment of angiogenesis-resistant tumors, inhibit cancer metastasis and improve patient survival. In this review, we describe the principal vascular mimicry pathways in addition to emphasizing the roles of hypoxia, autophagy and select proangiogenic oncogenes in this process.

Vascular mimicry: changing the therapeutic paradigms in cancer

Cancer is a major problem in the health system, and despite many efforts to effectively treat it, none has yet been fully successful. Angiogenesis and metastasis are considered as major challenges in the treatment of various cancers. Researchers have struggled to succeed with anti-angiogenesis drugs for the effective treatment of cancer, although new challenges have emerged in the treatment with the emergence of resistance to anti-angiogenesis and anti-metastatic drugs. Numerous studies have shown that different cancers can resist anti-angiogenesis drugs in a new process called vascular mimicry (VM). The studies have revealed that cells resistant to anti-angiogenesis cancer therapies are more capable of forming VMs in the in vivo and in vitro environment, although there is a link between the presence of VM and poor clinical outcomes. Given the importance of the VM in the challenges facing cancer treatment, researchers are trying to identify factors that prevent the formation of these structures. In this review article, it is attempted to provide a comprehensive overview of the molecules and main signaling pathways involved in VM phenomena, as well as the agents currently being identified as anti-VM and the role of VM in response to treatment and prognosis of cancer patients.

Vasculogenic mimicry in carcinogenesis and clinical applications

Distinct from classical tumor angiogenesis, vasculogenic mimicry (VM) provides a blood supply for tumor cells independent of endothelial cells. VM has two distinct types, namely tubular type and patterned matrix type. VM is associated with high tumor grade, tumor progression, invasion, metastasis, and poor prognosis in patients with malignant tumors. Herein, we discuss the recent studies on the role of VM in tumor progression and the diverse mechanisms and signaling pathways that regulate VM in tumors. Furthermore, we also summarize the latest findings of non-coding RNAs, such as lncRNAs and miRNAs in VM formation. In addition, we review application of molecular imaging technologies in detection of VM in malignant tumors. Increasing evidence suggests that VM is significantly associated with poor overall survival in patients with malignant tumors and could be a potential therapeutic target.

Epigallocatechin-3-Gallate Suppresses Vasculogenic Mimicry through Inhibiting the Twist/VE-Cadherin/AKT Pathway in Human Prostate Cancer PC-3 Cells

Vasculogenic mimicry (VM) is the alternative process of forming vessel-like networks by aggressive tumor cells, and it has an important role in tumor survival, growth, and metastasis. Epigallocatechin-3-gallate (EGCG) is well known to have diverse bioactivities including anti-cancer effects. However, the efficacy of EGCG on VM is elusive. In this study, we explored whether and how EGCG affects VM in human prostate cancer (PCa) PC-3 cells. Cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Invasive and VM formation abilities were assessed by an invasion assay and a three-dimensional (3D) culture VM tube formation assay, respectively. Western blots were carried out. An immunofluorescence assay was performed to detect nuclear twist expression. EGCG effectively inhibited the invasive ability, as well as tubular channel formation, without affecting cell viability. EGCG significantly downregulated the expression of vascular endothelial cadherin (VE-cadherin) and its transcription factor, twist, N-cadherin, vimentin, phosphor-AKT, and AKT, but not phospho-erythropoietin-producing hepatocellular receptor A2 (EphA2) and EphA2. In addition, EGCG diminished the nuclear localization of twist. Treatment with SC79, an AKT activator, effectively rescued EGCG-inhibited VM formation. These results demonstrated for the first time that EGCG causes marked suppression of VM through inhibiting the twist/VE-cadherin/AKT pathway in human PCa PC-3 cells.

Inhibition of Dimethylarginine Dimethylaminohydrolase (DDAH) Enzymes as an Emerging Therapeutic Strategy to Target Angiogenesis and Vasculogenic Mimicry in Cancer

The small free radical gas nitric oxide (NO) plays a key role in various physiological and pathological processes through enhancement of endothelial cell survival and proliferation. In particular, NO has emerged as a molecule of interest in carcinogenesis and tumor progression due to its crucial role in various cancer-related events including cell invasion, metastasis, and angiogenesis. The dimethylarginine dimethylaminohydrolase (DDAH) family of enzymes metabolize the endogenous nitric oxide synthase (NOS) inhibitors, asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA), and are thus key for maintaining homeostatic control of NO. Dysregulation of the DDAH/ADMA/NO pathway resulting in increased local NO availability often promotes tumor growth, angiogenesis, and vasculogenic mimicry. Recent literature has demonstrated increased DDAH expression in tumors of different origins and has also suggested a potential ADMA-independent role for DDAH enzymes in addition to their well-studied ADMA-mediated influence on NO. Inhibition of DDAH expression and/or activity in cell culture models and in vivo studies has indicated the potential therapeutic benefit of this pathway through inhibition of both angiogenesis and vasculogenic mimicry, and strategies for manipulating DDAH function in cancer are currently being actively pursued by several research groups. This review will thus provide a timely discussion on the expression, regulation, and function of DDAH enzymes in regard to angiogenesis and vasculogenic mimicry, and will offer insight into the therapeutic potential of DDAH inhibition in cancer based on preclinical studies.

Androgen receptor suppresses prostate cancer metastasis but promotes bladder cancer metastasis via differentially altering miRNA525-5p/SLPI-mediated vasculogenic mimicry formation

Early studies suggest that the androgen receptor (AR) may play differential roles in influencing prostate cancer (PCa) and bladder cancer (BCa) metastasis, but the underlying mechanisms remain unclear. Here, we found that the AR might function via differentially altering vasculogenic mimicry (VM) formation to either decrease PCa metastasis or increase BCa metastasis. Mechanism dissection showed that the AR could differentially alter the expression of the VM marker SLPI through miR-525-5p to regulate SLPI; moreover, it could either increase miR-525-5p transcription in PCa or decrease it in BCa via binding to different androgen-response-elements (AREs) located at different positions in the miR-525 precursor promoter. Further, results from liquid chromatography-mass spectrometry (LC-MS) showed that the co-factors of AR in PCa and BCa are NFIX and HDAC2, respectively. Together, these results provide the first detailed mechanism of how the AR can differentially alter PCa and BCa metastasis; thus, targeting the newly identified AR-miR-525-5p-SLPI axis may help suppress metastasis.

Kaempferol Promotes Apoptosis While Inhibiting Cell Proliferation via Androgen-Dependent Pathway and Suppressing Vasculogenic Mimicry and Invasion in Prostate Cancer

Kaempferol is a well-known natural flavonol reported to be a potential treatment for multiple cancers. In this study, we demonstrated that cell growth of androgen-sensitive LNCaP cells could be inhibited 33% by 5 μM kaempferol, around 60% by 10 μM kaempferol, and almost 100% by 15 μM kaempferol. Also, kaempferol showed relatively limited effect on PC-3 cells and nonmalignant RWPE-1 cells. In the presence of DHT, the IC₅₀ for kaempferol was 28.8 ± 1.5 μM in LNCaP cells, 58.3 ± 3.5 μM in PC-3 cells, and 69.1 ± 1.2 μM in RWPE-1 cells, respectively. Kaempferol promotes apoptosis of LNCaP cells in a dose-dependent manner in the presence of dihydrotestosterone (DHT). Then, luciferase assay data showed that kaempferol could inhibit the activation of androgen receptors induced by DHT significantly. The downstream targets of androgen receptors, such as PSA, TMPRSS2, and TMEPA1, were found decreased in the presence of kaempferol in qPCR data. It was then confirmed that the protein level of PSA was decreased. Kaempferol inhibits AR protein expression and nuclear accumulation. Kaempferol suppressed vasculogenic mimicry of PC-3 cells in an in vitro study. In conclusion, kaempferol is a promising therapeutic candidate for treatment of prostate cancer, where the androgen signaling pathway as well as vasculogenic mimicry are involved.

Phosphorylation of EphA2 receptor and vasculogenic mimicry is an indicator of poor prognosis in invasive carcinoma of the breast

PURPOSE

The occurrence of vasculogenic mimicry (VM) and EphA2-mediated tumour progression are associated with poor prognosis in various solid tumours. Here, we aimed to investigate the prognostic implications of VM and its association with phosphorylated EphA2 receptor in invasive carcinoma of the breast.

METHODS

The patients were stratified based on CD-31/PAS dual staining and subsequently the expression status of phospho-EphA2 (S897), FAK, phospho-ERK1/2 and Laminin 5Ƴ2 was analysed by immunohistochemistry. Survival of patients was correlated within the stratified cohort.

RESULTS

The pathologically defined VM phenotype and phospho-EphA2 (S897) expression status were significantly associated with lower disease-free survival (DFS) and overall survival (OS). Both the features were also found to be significantly associated with higher nodal status, poor Nottingham Prognostic Index (NPI) and were more prevalent in the triple-negative breast cancer (TNBC) group. Incidentally, there were no significant association between age of the patient, grade and size of the tumour with VM and phospho-EphA2 (S897). The effector molecules of phospho-EphA2 (S897) viz., Focal Adhesion Kinase (FAK), phospho-ERK1/2 and Laminin 5Ƴ2 were significantly upregulated in the VM-positive cohort. Survival analysis revealed that the VM and phospho-EphA2 (S897) dual-positive cohort had poorest DFS [mean time = 48.313 (39.992-56.633) months] and OS [mean time = 56.692 (49.055-64.328) months]. Individually, VM-positive [Hazard Ratio (HR) 6.005; 95% confidence interval (CI) 2.002-18.018; P = 0.001 for DFS and HR 11.654; 95% CI 3.195-42.508; P < 0.0001 for OS] and phospho-EphA2 (S897)-positive (HR 4.342; 95% CI 1.717-10.983; P = 0.002 for DFS and HR 5.853; 95% CI 1.663-20.602; P = 0.006 for OS) expression proved to be independent indicators of prognosis.

CONCLUSION

This study evaluated tumour dependency on oncogenic EphA2 receptor regulation and VM in invasive carcinoma of the breast and their prognostic significance. Significant correlations between VM, phospho-EphA2 and several clinicopathologic parameters of breast cancer were found. Subsequently, the occurrence of VM or phospho-EphA2 expression proved to be major contributors for poor prognosis in patients with breast cancer but their simultaneous expression failed to be an independent risk factor.

Correlations between quantitative parameters of contrast-enhanced ultrasound and vasculogenic mimicry in murine tumor model: a novel noninvasive technique for assessment?

Objective

Vasculogenic mimicry (VM) is a novel mechanism of tumor blood supply distinct from endothelial vessel (EV). VM is associated with malignancy, invasion, metastasis, and poor prognosis. Hitherto a noninvasive method for the assessment of VM in vivo has been lacking.

Methods

Contrast-enhanced ultrasound (CEUS) was performed to evaluate the quantitative parameters of tumors in mice. CD31 immunohistochemistry-Periodic Acid-Schiff double staining was conducted to identify the VM or EV in tumor tissues. Correlations between perfusion parameters and VM density was analyzed by Pearson correlation test.

Results

By the 15th day after tumor inoculation, the EV and VM density was 31.15 ± 7.14 and 14.11 ± 2.99 per 200× field. The maximal intensity (IMAX) was 301.19 ± 191.56%, and the rise time (RT), time to peak (TTP) and mean transit time (mTT) were 17.38 ± 7.82 s, 20.27 ± 9.61 s and 58.09 ± 26.44 s, respectively. VM density positively correlated to RT (r = 0.3598, P = 0.0226), TTP (r = 0.3733, P = 0.0177) and mTT(r = 0.6483, P <  0.0001), whereas EV density positively correlated to IMAX (r = 0.4519, P = 0.0034). The vascular diameter of VM was substantially larger than that of EV (43.81 ± 5.88 μm vs 11.21 ± 4.13 μm).

Conclusion

Three quantitative parameters related to VM were obtained and the relationships between CEUS and VM were established. CEUS might thus provide a novel noninvasive method to assess VM in vivo.

Morphological characteristics of vasculogenic mimicry and its correlation with EphA2 expression in gastric adenocarcinoma

Genetically deregulated tumor cells generate vascular channels by vasculogenic mimicry (VM) that is independent of endothelial blood vessels. The morphological characteristics of VM and the role of EphA2 in the formation of VM were evaluated in 144 clinical samples of gastric adenocarcinoma and AGS gastric cancer cell line. It has long been believed that VM consists of PAS-positive basement membrane and CD31/CD34-negative cells. Interestingly, we found that the luminal surface of gastric tumor cells that form VM channels showed PAS-positive reaction, and that the involvement of CD31/CD34-positive tumor cells in the formation of VM channels. Highly aggressive tumor cells that formed VM were found to express CD31 or CD34, implicating the angiogenic and vasculogenic potential of the genetically deregulated tumor cells. VM occurrence was positively correlated with high expression of EphA2 in our patient cohort, and the indispensable role of EphA2 in VM formation was identified by gene silencing in AGS cells. We also report that Epstein–Barr virus (EBV)-positive tumor cells were involved in the formation of VM channels in EBV-associated gastric cancer samples. Overall, our results suggest that EphA2 signaling promotes tumor metastasis by inducing VM formation during gastric tumorigenesis.

Serum promotes vasculogenic mimicry through the EphA2/VE-cadherin/AKT pathway in PC-3 human prostate cancer cells

AIMS

Serum is widely used for in vitro cell culture of eukaryotic cells. Although serum is well known to affect various biological activities in cancer cells, its effect in vasculogenic mimicry (VM) is not yet fully defined. Thus, this study investigated the role of serum in VM in human prostate cancer (PCa) PC-3 cells.

MAIN METHODS

Invasion assay and 3D culture VM tube formation assay are performed. VM-related molecules are checked by western blot and reverse transcriptase-polymerase chain reaction. Nuclear twist is detected by confocal after twist-FITC/DAPI double staining.

KEY FINDINGS

Serum dramatically induced not only invasion but also VM. Serum increased the phosphorylation of erythropoietin-producing hepatocellular A2 (EphA2) without affecting EphA2 expression. Both the protein and mRNA expression levels of vascular endothelial cadherin (VE-cadherin) are up-regulated by serum. Twist expression was increased in the nucleus by serum. Serum activated AKT through phosphorylation, despite the unchanged AKT expression. Serum caused an increase in matrix metalloproteinase-2 (MMP-2) and laminin subunit 5 gamma-2 (LAMC2) protein expressions. Wortmannin, a phosphoinositide-3-kinase inhibitor, significantly decreased serum-induced invasion and VM.

SIGNIFICANCE

These results demonstrated that serum activates EphA2 and up-regulates twist/VE-cadherin, which in turn activate AKT that up-regulates MMP-2 and LAMC2, thereby inducing the invasion and VM of human PCa PC-3 cells.

Vasculogenic mimicry formation in EBV-associated epithelial malignancies

Epstein-Barr virus (EBV)-associated epithelial cancers, including nasopharyngeal carcinoma (NPC) and approximately 10% of gastric cancers, termed EBVaGC, represent 80% of all EBV-related malignancies. However, the exact role of EBV in epithelial cancers remains elusive. Here, we report that EBV functions in vasculogenic mimicry (VM). Epithelial cancer cells infected with EBV develop tumor vascular networks that correlate with tumor growth, which is different from endothelial-derived angiogenic vessels and is VEGF-independent. Mechanistically, activation of the PI3K/AKT/mTOR/HIF-1α signaling cascade, which is partly mediated by LMP2A, is responsible for EBV-induced VM formation. Both xenografts and clinical samples of NPC and EBVaGC exhibit VM histologically, which are correlated with AKT and HIF-1α activation. Furthermore, although anti-VEGF monotherapy shows limited effects, potent synergistic antitumor activities are achieved by combination therapy with VEGF and HIF-1α-targeted agents. Our findings suggest that EBV creates plasticity in epithelial cells to express endothelial phenotype and provides a novel EBV-targeted antitumor strategy.

EBV latent infection contributes to the pathogenesis of epithelial malignancies by inducing angiogenesis. Here, the authors show EBV promotes vasculogenic mimicry in EBV associated epithelial cancers via AKT/HIF-1α pathway and combination therapy of HIF-1α and VEGF reduces tumour growth.

Protease-activated receptor-1 (PAR1) promotes epithelial-endothelial transition through Twist1 in hepatocellular carcinoma

Background

Tumor cells transfer into endothelial cells by epithelial–endothelial transition (EET), which is characterized by vasculagenic mimicry (VM) in morphology. VM can change tumor microcirculation, progression, and metastasis. However, the molecular mechanisms of endothelial-like transition remain unclear. EET is a subtype of epithelial–mesenchymal transition (EMT). Twist1, a transcriptional regulatory factor of EMT, is an important factor that induces EET in hepatocellular carcinoma(HCC), but the upstream signal of Twist1 is unclear.

Methods

Expression plasmids, Ca mobilization, and three-dimensional cultures were evaluated. Western blot assay, reporter gene assay, and immunofluorescence staining were conducted. A murine xenograft model was established. Analyses of immunohistochemistry, patient samples, and complementary DNA (cDNA) microarrays were also performed.

Results

This study demonstrated that protease-activated receptor-1 (PAR1) can increase the expression of endothelial markers and enhance VM formation by upregulating Twist1 both in vitro and in vivo through thrombin binding. Thrombin not only activates PAR1 but also promotes PAR1 internalization in a time-dependent manner. Clinical pathological analysis further confirms that PAR1 expression is directly correlated with the endothelial marker expression, VM formation, and metastasis and indicates poor survival rate of patients with tumors.

Conclusion

PAR1 promotes EET through Twist1 in HCC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0858-4) contains supplementary material, which is available to authorized users.

ZEB1-mediated vasculogenic mimicry formation associates with epithelial-mesenchymal transition and cancer stem cell phenotypes in prostate cancer

The zinc finger E‐box‐binding homeobox 1 (ZEB1) induced the epithelial–mesenchymal transition (EMT) and altered ZEB1 expression could lead to aggressive and cancer stem cell (CSC) phenotypes in various cancers. Tissue specimens from 96 prostate cancer patients were collected for immunohistochemistry and CD34/periodic acid–Schiff double staining. Prostate cancer cells were subjected to ZEB1 knockdown or overexpression and assessment of the effects on vasculogenic mimicry formation in vitro and in vivo. The underlying molecular events of ZEB1‐induced vasculogenic mimicry formation in prostate cancer were then explored. The data showed that the presence of VM and high ZEB1 expression was associated with higher Gleason score, TNM stage, and lymph node and distant metastases as well as with the expression of vimentin and CD133 in prostate cancer tissues. Furthermore, ZEB1 was required for VM formation and altered expression of EMT‐related and CSC‐associated proteins in prostate cancer cells in vitro and in vivo. ZEB1 also facilitated tumour cell migration, invasion and clonogenicity. In addition, the effects of ZEB1 in prostate cancer cells were mediated by Src signalling; that is PP2, a specific inhibitor of the Src signalling, dose dependently reduced the p‐Src⁵²⁷ level but not p‐Src⁴¹⁶ level, while ZEB1 knockdown also down‐regulated the level of p‐Src⁵²⁷ in PC3 and DU‐145 cells. PP2 treatment also significantly reduced the expression of VE‐cadherin, vimentin and CD133 in these prostate cancer cells. Src signalling mediated the effects of ZEB1 on VM formation and gene expression.

Nodal signaling promotes vasculogenic mimicry formation in breast cancer via the Smad2/3 pathway

Vasculogenic mimicry (VM) is a nonangiogenesis-dependent pathway that promotes tumor growth and disease progression. Nodal signaling has several vital roles in both embryo development and cancer progression. However, the effects of Nodal signaling on VM formation in breast cancer and its underlying mechanisms are ill-defined. We analyzed the relationship between Nodal signaling and VM formation in one hundred human breast cancer cases and the results showed that the expression of Nodal was significantly correlated with VM formation, tumor metastasis, differentiation grade, TNM stage and poor prognosis. Furthermore, up-regulation of Nodal expression promoted VM formation of breast cancer cells in vitro and in vivo. Knockdown of Nodal expression restrained VM formation. In addition, Nodal induced EMT and up-regulated the expression of Slug, Snail and c-Myc. We found that blocking the Smad2/3 pathway by administering SB431542 inhibited VM formation in breast cancer cell lines and xenografts. Taken together, Nodal signaling through the Smad2/3 pathway up-regulated Slug, Snail and c-Myc to induce EMT, thereby promoting VM formation. Our study suggests that the Nodal signaling pathway may serve as a therapeutic target to inhibit VM formation and improve prognosis in breast cancer patients.

Down-regulating Myoferlin inhibits the vasculogenic mimicry of melanoma via decreasing MMP-2 and inducing mesenchymal-to-epithelial transition

Vasculogenic mimicry (VM) constitutes a novel approach for tumour blood supply and contributes to tumour metastasis and poor prognosis in patients with melanoma. Myoferlin (MYOF), a type II membrane protein involved in membrane regeneration and repair, is elevated in several malignant tumours, especially in advanced melanomas. This study aims to investigate the role and mechanism of MYOF in the regulation of VM. VM structures were found in 14 of 52 tested melanoma samples, and high MYOF expression correlated with VM structures. According to Kaplan–Meier survival curves, VM channels and elevated MYOF expression both correlated with poor prognosis in melanoma patients. Down‐regulation of MYOF by siRNA severely impaired the capability of A375 cells to form VM structures in vitro. Further studies demonstrated MYOF knockdown inhibited cell migration and invasion, which is required for VM formation, via decreasing MMP‐2 expression as evidenced by Western blotting, RT‐RCP and ELISA results. SB‐3CT, a specific inhibitor of MMP‐2, showed similar inhibiting effects with siMYOF, further supporting that MYOF down‐regulation inhibits MMP‐2 expression to affect VM formation. Moreover, MYOF knockdown suppress VM formation by A375 cells by inducing mesenchymal‐to‐epithelial transition (MET). After down‐regulating MYOF, focal adhesions were enlarged and A375 cells developed into a clear epithelial morphology. Such cells acquired the expression of E‐cadherin at adherens junctions along with a loss of mesenchymal markers, such as Vimentin and Twist1. In conclusion, MYOF plays an important role in VM and knockdown of MYOF suppresses VM formation via decreasing MMP‐2 and inducing MET in A375 melanoma cells.

Tumor vasculogenic mimicry formation as an unfavorable prognostic indicator in patients with breast cancer

Vasculogenic mimicry (VM), a newly defined pattern of tumor blood perfusion, describes the functional plasticity of aggressive tumor cells forming de novo vascular networks and is associated with the cancer progression and metastasis. However, the VM-positive rate and the impact of VM status on breast cancer patients' clinicopathological parameters and prognosis remain unclear. Thus, we performed a meta-analysis by incorporating all available evidence to clarify these issues. Eight studies that involved 1,238 breast cancer patients were eligible for inclusion in our study. We found the VM-positive rate was 24% (pooled proportion was 0.24, 95% CI= 0.13-0.34), and VM was significantly associated with larger tumor size (>2 cm) (OR=0.49, 95% CI=0.26-0.90, P=0.02) and lymph node metastasis (OR=0.27, 95% CI=0.13-0.57, P=0.0005). A boardline correlation was also identified between VM and poorer differentiation (Grade II-III) (OR=0.07, 95% CI=0.00-1.24, P=0.07). Nevertheless, no statistically significant associations were observed between VM and hormone receptor and human epidermal growth factor receptor 2 status. Moreover, the results showed that breast cancer patients with VM-positive have a shorter overall survival than those with VM-negative (HR=0.23, 95% CI=0.08-0.38,P=0.003). In summary, VM was associated with more aggressive tumor phenotype and poor prognosis in patients with breast cancer. Developing strategies against the VM formation would be a promising therapeutic approach to breast cancer.

Vasculogenic Mimicry in Clinically Non-functioning Pituitary Adenomas: a Histologic Study

The term "vasculogenic mimicry" (VM) refers to the phenomenon in which vascular-like channels, which are not lined by endothelial cells, are formed in tumors. Since its discovery in 1999, it has been observed in several tumor types and is proposed to provide blood perfusion to tumors in absence of co-apted or neo-angiogenic blood vessels. Pituitary tumors are generally slow growing, benign adenomas which are less vascularized than the normal pituitary gland. To date, VM in pituitary adenomas has not been described. In this histological study, we assessed the presence of VM in a series of surgically resected clinically non-functioning pituitary adenomas (NFPAs) using CD34 and Periodic Acid-Schiff (PAS) double staining. To identify VM, slides were assessed for the presence of CD34-negative and PAS-positive channels indicating that they were not lined by endothelial cells. The histological staining pattern suggestive of VM was noted in 22/49 (44.9%) of the specimens studied. VM was observed in both recurring and non-recurring NFPAs. The incidence of VM present varied from case to case and within groups. There was no association between the presence of VM and gender, tumor size, Ki-67 index, recurrence or cavernous sinus invasion. VM was not noted in cases of non-tumorous pituitaries. Our findings suggest the existence of a complementary perfusion system in pituitary adenomas, implying potential clinical implications with respect to response to therapy and clinical course. Further research is warranted to confirm the presence of VM in pituitary adenomas to elucidate its clinical relevance in patients diagnosed with a pituitary adenoma.

Vascular mimicry formation is promoted by paracrine TGF-β and SDF1 of cancer-associated fibroblasts and inhibited by miR-101 in hepatocellular carcinoma

Vascular mimicry (VM) describes the phenomenon that tumor cells but not endothelial cells form vascular-like channels, which provide blood perfusion for tumor tissues. VM is associated with tumor growth, metastasis and worse survival of different cancers. The mechanisms of VM formation remain largely unknown. We showed that the conditioned medium of cancer-associated fibroblast (CM-CAF) promoted tumor cells to form capillary-like structure in vitro. Consistently, co-implantation of CAFs with tumor cells significantly enhanced VM formation in mouse xenografts, and higher amount of CAFs was found in VM⁺ human HCC tissues compared to VM^- ones. However, the CM-CAF-promoted VM formation was attenuated when TGF-β or SDF1 signaling was abrogated. Similar to CM-CAF, recombinant TGF-β1 and SDF1 induced VM formation. We further disclosed that the CAF-secreted TGF-β and SDF1 enhanced the expression of VE-cadherin, MMP2 and laminin5γ2 via TGF-βR1 and CXCR4 in tumor cells, thereby promoted VM formation. Moreover, tumor cells with high activity of self-sustaining TGF-β signaling displayed strong capability of VM formation. Subsequent investigations showed that miR-101, which was down-regulated in both tumor cells and CAFs, suppressed the CAF-promoted VM formation in vitro and in vivo. Gain- and loss-of-function analyses revealed that miR-101 attenuated TGF-β signaling transduction by targeting TGF-βR1 and Smad2 in tumor cells, and simultaneously abrogated SDF1 signaling by suppressing SDF1 expression in CAFs and inhibiting VE-cadherin expression in tumor cells. Our findings suggest that the miR-101-TGF-β/SDF1-VE-cadherin/MMP2/LAMC2 networks regulate VM formation and represent the potential targets for cancer therapy.