Demonstrating circulation in vasculogenic mimicry patterns of uveal melanoma by confocal indocyanine green angiography

N-myc downstream-regulated gene 1 can promote vasculogenic mimicry and angiogenesis in urothelial carcinoma

Urothelial carcinoma (UC) of the bladder is a common cause of cancer-related death worldwide. Vasculogenic mimicry (VM) is a process by which the malignant cells can generate vascular-like structures formed of periodic acid-Schiff (PAS) positive/CD31 negative extracellular matrix independent of angiogenesis and thus promotes tumor progression. N-myc downstream-regulated gene 1 (NDRG1) is a protein that can modulate tumor angiogenesis; however, its role in regulating tumor angiogenesis and VM formation has not been previously investigated in UC. This study aims to evaluate the role of intra-tumor microvessel density (MVD) (as a surrogate measure of angiogenesis), VM, and NDRG1 in UC and their correlation with different clinicopathologic features, then assess the correlation between them in UC. Sixty specimens of UC of the bladder were included. PAS-CD31 immunohistochemical double staining method was used to evaluate the intra-tumor MVD and VM. Immunohistochemical expression of NDRG1 was also examined. VM and NDRG1 expression were detected in 41.7% and 83.3% of UC specimens respectively. The mean of intra-tumor MVD, VM area, and NDRG1 was significantly higher in tumors with higher grade, lymphovascular invasion, and higher T stage. NDRG1 expression was positively correlated with MVD and VM. We can suggest that MVD, VM, and NDRG1 may serve as poor prognostic markers for UC. The positive correlation between NDRG1 and both MVD and VM may provide the first evidence that NDRG1 can induce tumor angiogenesis and VM in UC which may offer a novel pathway for further therapeutic strategies.

The driving mechanism and targeting value of mimicry between vascular endothelial cells and tumor cells in tumor progression

The difficulty and poor prognosis of malignant tumor have always been a difficult problem to be solved. The internal components of solid tumor are complex, including tumor cells, stromal cells and immune cells, which play an important role in tumor proliferation, migration, metastasis and drug resistance. Hence, targeting of only the tumor cells will not likely improve survival. Various studies have reported that tumor cells and endothelial cells have high plasticity, which is reflected in the fact that they can simulate each other's characteristics by endothelial-mesenchymal transition (EndMT) and vasculogenic mimicry (VM). In this paper, this mutual mimicry concept was integrated and reviewed for the first time, and their similarities and implications for tumor development are discussed. At the same time, possible therapeutic methods are proposed to provide new directions and ideas for clinical targeted therapy and immunotherapy of tumor.

Nano-composite hydrogels of Cu-Apa micelles for anti-vasculogenic mimicry

Vasculogenic mimicry (VM) describes the phenomenon whereby fluid-conducting vessels are formed by highly invasive tumour cells, which supply blood to tumours during their early growth stages. Single antiangiogenic agents have limited inhibitory effects on VM, therefore, a multi-pathway anti-VM strategy is required. In this study, Apatinib (Apa) was coordinated with Cu²⁺ to form a Cu-Apa copper complex. The latter was loaded into oligo-hyaluronic acid (HA) polymeric micelles (HA-Chol) and subsequently embedded in Astragalus polysaccharide-based in situ hydrogels (APsGels) to generate Cu-Apa/HA-Chol@APsGels. In this system, Cu-Apa exerts the combined effects of Cu²⁺ and Apa to inhibit VM; HA-Chol micelles achieve targeted drug delivery and enhance endocytosis efficiency; APsGels realise sustained release of the drugs to ensure an anti-VM effect. This system demonstrated improved VM inhibition with low cytotoxicity and high biocompatibility, wound healing, and transwell invasion in three-dimensional cell cultured VM. Moreover, this system significantly inhibited VM formation and melanoma growth in a mouse tumour transplantation model. This study provides an effective strategy for inhibiting VM.

Glioblastoma-Specific Strategies of Vascularization: Implications in Anti-Angiogenic Therapy Resistance

Angiogenesis has long been implicated as a crucial process in GBM growth and progression. GBM can adopt several strategies to build up its abundant and aberrant vasculature. Targeting GBM angiogenesis has gained more and more attention in anti-cancer therapy, and many strategies have been developed to interfere with this hallmark. However, recent findings reveal that the effects of anti-angiogenic treatments are temporally limited and that tumors become refractory to therapy and more aggressive. In this review, we summarize the GBM-associated neovascularization processes and their implication in drug resistance mechanisms underlying the transient efficacy of current anti-angiogenic therapies. Moreover, we describe potential strategies and perspectives to overcome the mechanisms adopted by GBM to develop resistance to anti-angiogenic therapy as new potential therapeutic approaches.

Targeting myeloid-derived suppressor cells to attenuate vasculogenic mimicry and synergistically enhance the anti-tumor effect of PD-1 inhibitor

Myeloid-derived suppressor cells (MDSCs) enhance the proliferation of endothelial cells to stimulate angiogenesis. However, many aggressive malignant tumors do not have endothelial cell-dependent blood vessels in the early stage and instead generate microcirculation by forming vasculogenic mimicry (VM). To date, the relationship between MDSCs and tumor cells remains the focus of ongoing studies. In this work, MDSCs were co-cultured with mouse melanoma cells and can enhance proliferation and VM formation of melanoma cells. For MDSCs targeting, doxycycline (DOX) was found to selectively suppress PMN-MDSCs but has no influence on T cells. In addition, DOX pretreatment substantially reduced the promoting ability of MDSCs for the VM formation of B16-F10 cells. DOX also inhibited tumor growth and enhanced the antitumor activity of PD-1 inhibitors in C57BL6 and BALB/c mice subcutaneously inoculated with B16-F10 and 4T1 cells, respectively. In conclusion, the combination of DOX and PD-1 inhibitor could be an anticancer strategy.

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MDSCs accumulated in the B16-F10 tumor-bearing mice

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MDSCs promote the formation of vasculogenic mimicry

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Doxycycline selectively suppressed PMN-MDSCs

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Doxycycline combined with PD-1 inhibitor significantly inhibited tumor growth

[Results of optical coherence tomography angiography in choroidal melanoma]

Blood supply is known to be required for tumor growth and metastasis, and the formation of the tumor's own vasculature plays a critical role in the development of solid neoplasms. The method of optical coherence tomography angiography (OCTA) is considered promising for the study of angioarchitectonics.

PURPOSE

To evaluate the OCTA signs of choroidal melanoma (CM) depending on its sizes.

MATERIAL AND METHODS

The study included 24 patients with CM (24 eyes, of them with small CM - 22 eyes) aged 55.0±12.08 years (37 to 80 years old) with mean prominence of 2.35±0.87 mm (1.0 to 4.7 mm).

RESULTS AND DISCUSSION

Retinal vascular attenuation in the tumor area was observed in 21 eyes. Changes in angioarchitectonics in the area of CM localization can be detected at a thickness of 1 mm, and the tumor's own vasculature - starting with a thickness of 1.4 mm. The development of vascular changes in CM can be represented as follows: initially, with CM prominence of up to 1.4 mm, indirect signs of increased blood flow in the overlaying choriocapillaris layer are visualized, most likely due to its compression; as the tumor grows and its thickness increases in its most dominant part, the choriocapillaris layer is completely destroyed, which leads to reactive expansion of the choroidal capillaries along the layer's edges. This is manifested as attenuation of the vascular signal in the central part of the tumor and its intensification along its edges. In the meantime, collaterals begin to form in the deep vascular plexus of the retina. Later on, chaotic vascular arches begin to form in the inner layers of the choroid along the tumor edge; as the tumor grows, they anastomose with the retinal vessels. Identification of the tumor's own vessels in the deeper-lying layers is possible with tumor prominence of at least 1.4 mm. At the level of the deep choroidal layers, the tumor's vascular pattern is more consistent with the angiographic data and patterns of vasculogenic mimicry described in literature.

CONCLUSION

Changes in angioarchitectonics in the area of CM localization can be detected at a thickness of 1 mm, and the tumor's own vasculature - starting with a thickness of 1.4 mm. The vascular pattern at the level of the deep choroidal layers best corresponds to the reported angiographic picture and patterns of vasculogenic mimicry.

Regulatory mechanisms and therapeutic targeting of vasculogenic mimicry in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a typical hyper-vascular solid tumor; aberrantly rich in tumor vascular network contributes to its malignancy. Conventional anti-angiogenic therapies seem promising but transitory and incomplete efficacy on HCC. Vasculogenic mimicry (VM) is one of functional microcirculation patterns independent of endothelial vessels which describes the plasticity of highly aggressive tumor cells to form vasculogenic-like networks providing sufficient blood supply for tumor growth and metastasis. As a pivotal alternative mechanism for tumor vascularization when tumor cells undergo lack of oxygen and nutrients, VM has an association with the malignant phenotype and poor clinical outcome for HCC, and may challenge the classic anti-angiogenic treatment of HCC. Current studies have contributed numerous findings illustrating the underlying molecular mechanisms and signaling pathways supporting VM in HCC. In this review, we summarize the correlation between epithelial-mesenchymal transition (EMT), cancer stem cells (CSCs) and VM, the role of hypoxia and extracellular matrix remodeling in VM, the involvement of adjacent non-cancerous cells, cytokines and growth factors in VM, as well as the regulatory influence of non-coding RNAs on VM in HCC. Moreover, we discuss the clinical significance of VM in practice and the potential therapeutic strategies targeting VM for HCC. A better understanding of the mechanism underlying VM formation in HCC may optimize anti-angiogenic treatment modalities for HCC.

[Indocyanine green angiography in the diagnostics of choroidal tumors]

PURPOSE

To study the use of ultrasound color Doppler imaging and indocyanine green (ICG) angiography for identification of malignant vasculature of choroidal tumors.

MATERIAL AND METHODS

The study included 46 patients (46 eyes) with tumors of the choroid: 19 men and 26 women aged 22 to 89 years, average age 53.2±17.1 years. All patients underwent indocyanine green angiography and Doppler ultrasound imaging. At the time of examination, thickness of the tumors ranged from 1.1 mm to 3.0 mm, and the base diameter from 4.0 mm to 13.0 mm. Choroidal melanoma was diagnosed in 27 patients, choroidal nevus in 10, choroidal hemangioma in 5, and choroidal metastasis in 4 patients.

RESULTS

The results of indocyanine green angiography demonstrate that the pathological malignant vasculature was determined: nevi was diagnosed in 7 out of 10 patients, choroidal melanoma in 16 out of 27, metastasis in 2 out of 4, and hemangioma in none of the 5 patients. Pathological malignant vasculature was determined in most patients with choroidal melanoma (77.8%), in all patients with choroidal hemangioma and in 3 patients with choroidal metastases. Ultrasound imaging revealed malignant vasculature in 15 of 27 (56%) patients with choroidal melanoma, it could be identified in all patients with hemangioma in 2 patients and with choroidal metastases, and in none patients with choroidal nevi.

CONCLUSIONS

Indocyanine green angiography helps verify malignant vasculature in 77.8% of patients with small and medium sized choroidal melanomas. Angioarchitecture of choroidal tumors visualized with indocyanine green angiography is characterized by variability of patterns, which should be taken into account in the differential diagnosis of various pathological diseases.

Ocular manifestations in phakomatosis pigmentovascularis: Current concepts on pathogenesis, diagnosis, and management

Phakomatosis pigmentovascularis is a rare congenital multisystemic disease with variable manifestations where a vascular malformation of the skin is associated with a pigmentary nevus. Ocular involvement includes glaucoma, choroidal hemangioma, and pigmentary alterations that predispose to uveal melanoma. Diagnosis is made on clinical grounds, although recent advances in molecular genetics have better clarified the etiopathogenesis of the condition. The advent of improved imaging techniques such as enhanced depth imaging spectral domain optical coherence tomography has provided new insight into the ocular alterations, enabling better follow-up of patients. We review the ophthalmic manifestations of the disease with an update on etiopathogenesis and current management strategies.

Paradigms of vascularization in melanoma: Clinical significance and potential for therapeutic targeting

Melanoma is the most aggressive form of skin cancer. Malignant melanoma in particular has a poor prognosis and although treatment has improved, drug resistance continues to be a challenge. Angiogenesis, the formation of blood vessels from existing microvessels, precedes the progression of melanoma from a radial growth phase to a malignant phenotype. In addition, melanoma cells can form networks of vessel-like fluid conducting channels through vasculogenic mimicry (VM). Both angiogenesis and VM have been postulated to contribute to the development of resistance to treatment and to enable metastasis. Also, the metastatic spread of melanoma is highly dependent on lymphangiogenesis, the formation of lymphatic vessels from pre-existing vessels. Interestingly, the design and clinical testing of drugs that target VM and lymphangiogenesis lag behind that of angiogenesis inhibitors. Despite this, antiangiogenic drugs have not significantly improved the overall survival of melanoma patients, thus necessitating the targeting of alternative mechanisms. In this article, I review the roles of the three paradigms of tissue perfusion, namely, angiogenesis, VM and lymphangiogenesis, in promoting melanoma progression and metastasis. This article also explores the latest development and potential opportunities in the therapeutic targeting of these processes.

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.

Molecular Mechanisms and Anticancer Therapeutic Strategies in Vasculogenic Mimicry

Vasculogenic mimicry (VM) is a vascular formation mechanism used by aggressive tumor cells. VM provides an alternative pathway for adequate blood perfusion and challenges the traditional angiogenesis mechanism that depends only on endothelial cells (ECs), as VM-forming tumor cells express a mixed endothelial/tumor phenotype. VM is closely correlated with tumor invasion, migration, and progression. Hence, anticancer therapeutic strategies targeting VM biogenesis are essential. It is widely acknowledged that the VM formation mechanism involves multiple pathways. The purpose of this review is to describe the potential molecular mechanisms related to different pathways and discuss the involvement of microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) in VM formation. Moreover, we discuss the significance of VM in clinical practice and present new anticancer therapeutic strategies that target VM.

Mechanisms of Vasculogenic Mimicry in Ovarian Cancer

Solid tumors carry out the formation of new vessels providing blood supply for growth, tumor maintenance, and metastasis. Several processes take place during tumor vascularization. In angiogenesis, new vessels are derived from endothelial cells of pre-existing vessels; while in vasculogenesis, new vessels are formed de novo from endothelial progenitor cells, creating an abnormal, immature, and disorganized vascular network. Moreover, highly aggressive tumor cells form structures similar to vessels, providing a pathway for perfusion; this process is named vasculogenic mimicry (VM), where vessel-like channels mimic the function of vessels and transport plasma and blood cells. VM is developed by numerous types of aggressive tumors, including ovarian carcinoma which is the second most common cause of death among gynecological cancers. VM has been associated with poor patient outcome and survival in ovarian cancer, although the involved mechanisms are still under investigation. Several signaling molecules have an important role in VM in ovarian cancer, by regulating the expression of genes related to vascular, embryogenic, and hypoxic signaling pathways. In this review, we provide an overview of the current knowledge of the signaling molecules involved in the promotion and regulation of VM in ovarian cancer. The clinical implications and the potential benefit of identification and targeting of VM related molecules for ovarian cancer treatment are also discussed.

Infectious Knockdown of CREB and HIF-1 for the Treatment of Metastatic Uveal Melanoma

Uveal melanoma (UM) is the most prevalent primary intraocular cancer in adults. Up to half the patients develop metastases that are currently incurable, and most patients die within two years following the diagnosis of metastases. Therefore, novel therapeutic approaches are required. It has been established that tumor cells are more resistant to the hypoxia cue than non-malignant cells and can remain viable in hypoxia. Oxygen absence in hypoxic tumor areas means the absence of chemotherapeutics and the absence of the effector for radiotherapy (free oxygen radicals). To overcome this treatment resistance, we constructed MuLV-based replication-competent retroviral (RCR) vectors expressing shRNA targeting the hypoxia-response regulating genes CREB and HIF-1. These RCRs express shRNAs either against a single exon or against an exon and the poly-A signal to minimize the point-mutation resistance. These RCRs that only infect replicating cells will preferentially infect tumor cells. Pre-infected Mel270 UM subcutaneous xenografts in SCID mice were monitored weekly in vivo via bioluminescence. Here, we demonstrate that the knockdown of CREB or HIF-1 in UM cells dramatically decreases UM tumor progression. The reduction of the expression of Glut-1, which is a major glucose transporter in cancer cells, within tumors that are infected with the armed viruses may indicate UM's dependence on glycolysis for tumor progression.

Uveal Melanoma, Angiogenesis and Immunotherapy, Is There Any Hope?

Uveal melanoma is considered a rare disease but it is the most common intraocular malignancy in adults. Local treatments are effective, but the systemic recurrence rate is unacceptably high. Moreover, once metastasis have developed the prognosis is poor, with a 5-year survival rate of less than 5%, and systemic therapies, including immunotherapy, have rendered poor results. The tumour biology is complex, but angiogenesis is a highly important pathway in these tumours. Vasculogenic mimicry, the ability of melanomas to generate vascular channels independently of endothelial cells, could play an important role, but no effective therapy targeting this process has been developed so far. Angiogenesis modulates the tumour microenvironment of melanomas, and a close interplay is established between them. Therefore, combining immune strategies with drugs targeting angiogenesis offers a new therapeutic paradigm. In preclinical studies, these approaches effectively target these tumours, and a phase I clinical study has shown encouraging results in cutaneous melanomas. In this review, we will discuss the importance of angiogenesis in uveal melanoma, with a special focus on vasculogenic mimicry, and describe the interplay between angiogenesis and the tumour microenvironment. In addition, we will suggest future therapeutic approaches based on these observations and mention ways in which to potentially enhance current treatments.

Cancer-associated fibroblast regulation of tumor neo-angiogenesis as a therapeutic target in cancer

Adequate blood supply is essential for tumor survival, growth and metastasis. The tumor microenvironment (TME) is dynamic and complex, comprising cancer cells, cancer-associated stromal cells and their extracellular products. The TME serves an important role in tumor progression. Cancer-associated fibroblasts (CAFs) are the principal component of stromal cells within the TME, and contribute to tumor neo-angiogenesis by altering the proteome and degradome. The present paper reviews previous studies of the molecular signaling pathways by which CAFs promote tumor neo-angiogenesis and highlights therapeutic response targets. Also discussed are potential strategies for antitumor neo-angiogenesis to improve tumor treatment efficacy.

Overview of advances in vasculogenic mimicry - a potential target for tumor therapy

Vasculogenic mimicry (VM) describes the process utilized by highly aggressive cancer cells to generate vascular-like structures without the presence of endothelial cells. VM has been vividly described in various tumors and participates in cancer progression dissemination and metastasis. Diverse molecular mechanisms and signaling pathways are involved in VM formation. Furthermore, the patterning characteristics of VM, detected with molecular imaging, are being investigated for use as a tool to aid clinical practice. This review explores the most recent studies investigating the role of VM in tumor induction. Indeed, the recognition of these advances will increasingly affect the development of novel therapeutic target strategies for VM in human cancer.

In vitro and in vivo apatinib inhibits vasculogenic mimicry in melanoma MUM-2B cells

The effect of apatinib on the formation of vasculogenic mimicry (VM) was studied in a malignant melanoma cell line. MUM-2B cells cultured in three-dimensional Matrigel were treated with varying concentrations (0, 0.01, 0.05, 0.1, 0.5 μmol/L) of apatinib to test its effect on VM in vitro, followed by MTT proliferation and transwell invasion assays to determine the effect of apatinib on cell proliferation and invasion of MUM-2B cells. In vivo, we used a melanoma cancer model to test the effect of short-term apatinib (100, 200, 300 mg/kg) treatment on VM. Western blotting, immunohistochemistry staining, and CD31-PAS dual staining were performed to assess the expression of VEGFR-2, ERK-1/2, PI3K, and MMP-2, and formation of VM. The results showed apatinib-treated groups formed a lesser number of VM in 3D matrigel, while the cell viability in MTT proliferation assay and the number of migration cells in transwell invasion assay were significantly lower in apatinib-treated groups. In addition, short-term apatinib treatment inhibited angiogenesis, VM formation, and tumor growth in models of melanoma cancer. Mice in apatinib-treated groups showed a markedly reduced expression of VEGFR-2, ERK-1/2, PI3K, and MMP-2. In summary, apatinib could inhibit the expression of VEGFR-2, and downregulate the ERK1/2/PI3K/MMP-2 signaling cascade, which may be one of the underlying mechanisms by which apatinib inhibits angiogenesis and the development of VM in models of melanoma cancer, and restrains the formation of VM by MUM-2B cells. Apatinib shows inhibitory effects on cell proliferation and invasion of MUM-2B cells, which is a close relationship with the VM.

Unraveling the Role of Angiogenesis in Cancer Ecosystems

Activation of the tumor and stromal cell-driven angiogenic program is one of the first requirements in the tumor ecosystem for growth and dissemination. The understanding of the dynamic angiogenic tumor ecosystem has rapidly evolved over the last decades. Beginning with the canonical sprouting angiogenesis, followed by vasculogenesis and intussusception, and finishing with vasculogenic mimicry, the need for different neovascularization mechanisms is further explored. In addition, an overview of the orchestration of angiogenesis within the tumor ecosystem cellular and molecular components is provided. Clinical evidence has demonstrated the effectiveness of traditional vessel-directed antiangiogenics, stressing on the important role of angiogenesis in tumor establishment, dissemination, and growth. Particular focus is placed on the interaction between tumor cells and their surrounding ecosystem, which is now regarded as a promising target for the development of new antiangiogenics.

Vasculogenic mimicry and expression of slug and vimentin correlate with metastasis and prognosis in non-small cell lung cancer

Background: Non-small cell lung cancer (NSCLC) has been the leading cause of cancer death in recent years, its morbidity and mortality were increasing yearly. The presence of vasculogenic mimicry (VM) is associated with a high tumor grade, short survival, invasion, and metastasis. Slug is a key regulating factor in the process of EMT. Vimentin is one of the cytoskeleton proteins that plays an important role in EMT. However, associations among VM, Slug and vimentin and their clinicopathologic significance in NSCLC are unclear. In this study, we analyzed associations among VM, Slug and vimentin in NSCLC, and their respective associations with clinicopathologic characteristics and survival in NSCLC. Methods: Positive expression of VM, Slug and vimentin in 198 whole NSCLC tissue samples were detected by immunohistochemical staining. Patients' clinical data were also collected. Results: Levels of VM, Slug and vimentin were significantly higher in NSCLC tissues than in normal lung tissues. Levels of VM, Slug and vimentin were positively associated with tumor grade, distant metastasis (DM), lymph node metastasis (LNM), and tumor-node metastasis (TNM) stage, and inversely with patients overall survival time (OST). In multivariate analysis, high expression of VM, Slug, vimentin, and tumor grade, DM, LNM, TNM stage, were potential to be independent prognostic factors for OST in patients with NSCLC. Conclusion: VM, Slug and vimentin affect NSCLC evolution; and the combined detection of VM, Slug and vimentin are valuable factors for metastasis and prognosis in NSCLC patients.

Osteopontin and vasculogenic mimicry formation are associated with response to neoadjuvant chemotherapy in advanced breast cancer

Introduction

Osteopontin (OPN), a multifunctional phosphoprotein, has been implicated in a series of important physiologic and pathophysiologic processes. In breast cancer, OPN functionally contributes to the tumorigenicity of spheroid-forming cells. It also plays a critical role in enhancing the proliferation, tumorigenicity, and ability to display vasculogenic mimicry (VM) of spheroid-forming cells in breast cancer. However, the role of OPN in breast cancer is not clear.

Patients and methods

This study investigated OPN expression and VM in breast cancer patients before neoadjuvant chemotherapy (NACT). Their association with clinicopathologic factors was first analyzed by immunohistochemistry. Then, the response of breast cancer patients to NACT was evaluated. The correlation between the clinicopathologic factors, including the molecular subtype, and the response to NACT was analyzed.

Results

Immunohistochemical analysis showed positive staining of OPN in 40% of the breast cancer patients, whereas VM, which was related to tumor stage, was observed in 30% of cases. OPN expression was found to have a significant correlation with VM (P<0.05). The results also indicated that the clinicopathologic factors were not related to the response to NACT, including the molecular subtype. The multivariate analysis of clinicopathologic features correlated with pathological complete response (pCR) indicated that OPN(+)VM(+) was correlated with pCR (P<0.001).

Conclusion

Our findings underlined that the concurrence of OPN-positive expression and VM can predict the pCR to NACT in breast cancer. The efficiency of NACT in certain patients can be easily predicted by detecting the expression of OPN and VM.

Endothelium-Independent Primitive Myxoid Vascularization Creates Invertebrate-Like Channels to Maintain Blood Supply in Optic Gliomas

Optic gliomas are brain tumors characterized by slow growth, progressive loss of vision, and limited therapeutic options. Optic gliomas contain various amounts of myxoid matrix, which can represent most of the tumor mass. We sought to investigate biological function and protein structure of the myxoid matrix in optic gliomas to identify novel therapeutic targets. We reviewed histological features and clinical imaging properties, analyzed vasculature by immunohistochemistry and electron microscopy, and performed liquid chromatography-mass spectrometry on optic gliomas, which varied in the amount of myxoid matrix. We found that although subtypes of optic gliomas are indistinguishable on imaging, the microvascular network of pilomyxoid astrocytoma, a subtype of optic glioma with abundant myxoid matrix, is characterized by the presence of endothelium-free channels in the myxoid matrix. These tumors show normal perfusion by clinical imaging and lack histological evidence of hemorrhage organization or thrombosis. The myxoid matrix is composed predominantly of the proteoglycan versican and its linking protein, a vertebrate hyaluronan and proteoglycan link protein 1. We propose that pediatric optic gliomas can maintain blood supply without endothelial cells by using invertebrate-like channels, which we termed primitive myxoid vascularization. Enzymatic targeting of the proteoglycan versican/hyaluronan and proteoglycan link protein 1 rich myxoid matrix, which is in direct contact with circulating blood, can provide novel therapeutic avenues for optic gliomas of childhood.

Periodic acid-Schiff-positive loops and networks as a prognostic factor in oral mucosal melanoma

The prognostic factors of oral mucosal melanoma (OMM), a rare and aggressive neoplasm, remain to be determined. The aim of this study is to investigate the prognostic significance of vasculogenic mimicry in OMM. The clinical data of 62 patients with primary OMM treated in Shanghai Ninth People's Hospital from April 2007 to April 2012 were retrieved and analyzed retrospectively. Staining of periodic acid-Schiff (PAS) and CD31 immunohistochemistry were performed to evaluate the prognostic value of PAS-positive patterns, blood lakes, and microvascular density. PAS-positive loops and networks (P<0.001) as well as blood lakes (P=0.040) were found to be predictors of overall survival (OS). The presence of PAS-positive loops and networks was an independent prognostic factor of poor OS in multivariate analysis (P=0.002). Although the presence of PAS-positive loops and networks was associated with hematogenous metastasis (P=0.041) and lymphogenous metastasis (P=0.041), it was not an independent predictor of both types of metastasis in multivariate analysis. Microvascular density was not associated with OS (P=0.627) and metastasis of OMM patients. PAS-positive loops and networks have a significant prognostic value in OMM. Detection of PAS-positive patterns may lead to better staging and serve as a prognostic parameter of OMM.

The relationship between vasculogenic mimicry and epithelial-mesenchymal transitions

Vasculogenic mimicry (VM) is a vascular‐like structure which can mimic the embryonic vascular network pattern to nourish the tumour tissue. As a unique perfusion way, VM is correlated with tumour progression, invasion, metastasis and lower 5‐year survival rate. Notably, epithelial‐mesenchymal transition (EMT) regulators and EMT‐related transcription factors are highly up‐regulated in VM‐forming tumour cells, which demonstrated that EMT may play a crucial role in VM formation. Therefore, the up‐regulation of EMT‐associated adhesion molecules and other factors can also make a contribution in VM‐forming process. Depending on these discoveries, VM and EMT can be utilized as therapeutic target strategies for anticancer therapy. The purpose of this article is to explore the advance research in the relationship of EMT and VM and their corresponding mechanisms in tumorigenesis effect.

Wnt3a Promotes the Vasculogenic Mimicry Formation of Colon Cancer via Wnt/β-Catenin Signaling

Our previous study provided evidence that non-canonical Wnt signaling is involved in regulating vasculogenic mimicry (VM) formation. However, the functions of canonical Wnt signaling in VM formation have not yet been explored. In this study, we found the presence of VM was related to colon cancer histological differentiation (p < 0.001), the clinical stage (p < 0.001), and presence of metastasis and recurrence (p < 0.001). VM-positive colon cancer samples showed increased Wnt3a expression (p < 0.001) and β-catenin nuclear expression (p < 0.001) compared with the VM-negative samples. In vitro, over-regulated Wnt3a expression in HT29 colon cancer cells promoted the capacity to form tube-like structures in the three-dimensional (3-D) culture together with increased expression of endothelial phenotype-associated proteins such as VEGFR2 and VE-cadherin. The mouse xenograft model showed that Wnt3a-overexpressing cells grew into larger tumor masses and formed more VM than the control cells. In addition, the Wnt/β-catenin signaling antagonist Dickkopf-1(Dkk1) can reverse the capacity to form tube-like structures and can decrease the expressions of VEGFR2 and VE-cadherin in Wnt3a-overexpressing cells. Taken together, our results suggest that Wnt/β-catenin signaling is involved in VM formation in colon cancer and might contribute to the development of more accurate treatment modalities aimed at VM.

Glioblastoma vasculogenic mimicry: signaling pathways progression and potential anti-angiogenesis targets

Glioblastoma (GBM) is a highly angiogenic malignancy that is resistant to standard therapy; neo-formed vessels of this aggressive malignancy are thought to arise by sprouting of pre-existing brain capillaries. However, the conventional anti-angiogenic therapy, which seemed promising initially, shows transitory and incomplete efficacy. The discovery of vasculogenic mimicry (VM) has offered a new horizon for understanding tumor vascularization. VM is a tumor cell-constituted, matrix-embedded fluid-conducting meshwork that is independent of endothelial cells and is positively correlated with poor prognosis. Therefore, a better understanding of GBM vasculature is needed to optimize anti-angiogenic therapy. This review focuses on the signaling molecules and cascades involved in VM in relation to ongoing glioma research, as well as the clinical translational advances in GBM that have been offered by the development of optimized anti-angiogenesis treatment modalities.

Vasculogenic mimicry: a novel target for glioma therapy

Anti-angiogenic therapy has shown promising but insufficient efficacy on gliomas. Recent studies suggest that vasculogenic mimicry (VM), or the formation of non-endothelial, tumor-cell-lined microvascular channels, occurs in aggressive tumors, including gliomas. There is also evidence of a physiological connection between the endothelial-lined vasculature and VM channels. Tumor cells, by virtue of their high plasticity, can form vessel-like structures themselves, which may function as blood supply networks. Our previous study on gliomas showed that microvessel density was comparably less in VM-positive tumors than in VM-negative tumors. Thus, VM may act as a complement to ensure tumor blood supply, especially in regions with less microvessel density. Patients with VM-positive gliomas survived a shorter period of time than did patients with VM-negative gliomas. Although the detailed molecular mechanisms for VM are not fully understood, glioma stem cells might play a key role, since they are involved in tumor tissue remodeling and contribute to neovascularization via transdifferentiation. In the future, successful treatment of gliomas should involve targeting both VM and angiogenesis. In this review, we summarize the progress and challenges of VM in gliomas.

Sphingosine kinase 1 induces vasculogenic mimicry formation by up-regulating VEGF expression and secretion in human colon cancer cell line HT-29

AIM: To investigate the role of sphingosine kinase 1 (Sphk1) in vasculogenic mimicry (VM) formation in human colon cancer cell line HT-29 in vitro.

METHODS: HT-29 cells were divided into three groups and treated with 100 nm/L of phorbol 12-myristate 13-acetate (PMA, Sphk1 activation group), 50 μmol/L of N,N-dimethyl-D-erythro-sphingosine (DMS, suppression group), and equal volume of culture medium (control group), respectively. After treatment, cell proliferation was determined by MTT assay, and cell invasiveness and migration were assessed by Transwell chamber assays. Cell apoptosis was observed by transmission electron microscopy (TEM). VM formation was observed in a three-dimensional culture system. The mRNA and protein expression of vascular endothelial growth factor (VEGF) was evaluated by QT-PCR and Western blot, respectively. The secretion of VEGF was detected by ELISA.

RESULTS: Treatment with DMS significantly suppressed cell proliferation, invasion and migration, promoted apoptosis, down-regulated VEGF mRNA and protein expression and secretion, and did not induce VM formation. In contrast, treatment with PMA significantly promoted cell proliferation, invasion (112.00 ± 6.25 vs 57.00 ± 8.00, 142.00 ± 5.57, both P < 0.05) and migration (69.33 ± 4.04 vs 42.00 ± 4.16, 111.00 ± 8.03, both P < 0.05), suppressed apoptosis, up-regulated VEGF mRNA (1.000 vs 0.740 ± 0.122, 1.220 ± 0.075, both P < 0.05) and protein (0.39 ± 0.05 vs 0.23 ± 0.02, 0.65 ± 0.06, both P < 0.05) expression and secretion (103.00 ± 8.96 vs 63.89 ± 8.44, 201.01 ± 17.93, both P < 0.05), and induced the formation of tubular VM.

CONCLUSION: Sphk1 promotes cell proliferation, invasion and migration, suppresses cell apoptosis, and induces VM formation possibly by up-regulating VEGF expression and secretion in human HT-29 colon cancer cell line.

Vascular Mimicry: Concepts and Implications for Anti-Angiogenic Therapy

As in normal tissues, solid tumors depend on vascular networks to supply blood, oxygen, and nutrients. Tumor blood vessels are formed by common processes of neovascularization for example endothelial sprouting. However, some tumors have alternative and unexpected mechanisms of neovascularization at their disposal. In a process termed "vascular mimicry," tumors create their own, tumor cell-lined channels for fluid transport independent of typical modes of angiogenesis. These tumor cell-lined conduits may express endothelial-selective markers and anti-coagulant factors which allow for anastamosis with host endothelium. In this review, we explore the current status of vascular mimicry research, highlighting recent evidence which strengthens the hypothesis for this unusual ability of tumor cells. Furthermore, we address the theoretical possibility that vascular mimicry provides a mechanism whereby tumors could escape anti-angiogenic therapies.

Vasculogenic mimicry and its clinical significance in medulloblastoma

Vasculogenic mimicry (VM), a process involving the formation of a tubular structure by highly invasive and genetically dysregulated tumor cells, can supplement the function of blood vessels to transport nutrients and oxygen to maintain the growth of tumor cells in many malignant tumors. We aimed to explore the existence of VM and its clinical significance in medulloblastoma in this study. VM was identified in 9 out of 41 (22%) medulloblastoma tissues. Immunohistochemical studies revealed that the presence of VM was associated with the expression of MMP-2, MMP-14, EphA2 and laminin 5γ2. Tumor tissues with VM were associated with lower microvessel density (MVD), which was indirect evidence of the blood supply function of VM. Survival analysis and log-rank tests showed that patients with VM had shorter overall survival time than those without VM. Multivariate analysis and the Cox proportional hazards model identified VM as independent prognostic factor for overall survival. Our results confirmed the existence of VM for the first time and revealed that VM is a strong independent prognostic factor for survival in patients with medulloblastoma.

A pilot histomorphology and hemodynamic of vasculogenic mimicry in gallbladder carcinomas in vivo and in vitro

Background

Vasculogenic mimicry (VM), as a new blood supply for tumor growth and hematogenous metastases, has been recently described in highly aggressive human melanoma cells, etc. We previously reported VM in human gallbladder carcinomas and its clinical significance. In this study, we further studied histomorphology and hemodynamic of VM in gallbladder carcinomas in vivo and in vitro.

Methods

The invasive potential of human gallbladder carcinoma cell lines GBC-SD and SGC-996 were identified by Transwell membrane. The vasculogenic-like network structures and the signal intensities i.e. hemodynamic in gallbladder carcinomas stimulated via the three-dimensional matrix of GBC-SD or SGC-996 cells in vitro, the nude mouse xenografts of GBC-SD or SGC-996 cells in vivo were observed by immunohistochemistry (H&E staining and CD₃₁-PAS double staining), electron microscopy and micro-MRA with HAS-Gd-DTPA, respectively.

Results

Highly aggressive GBC-SD or poorly aggressive SGC-996 cells preconditioned by highly aggressive GBC-SD cells could form patterned networks containing hollow matrix channels. 85.7% (6/7) of GBC-SD nude mouse xenografts existed the evidence of VM, 5.7% (17/300) channels contained red blood cells among these tumor cell-lined vasculatures. GBC-SD xenografts showed multiple high-intensity spots similar with the intensity observed at tumor marginal, a result consistent with pathological VM.

Conclusions

VM existed in gallbladder carcinomas by both three-dimensional matrix of highly aggressive GBC-SD or poorly aggressive SGC-996 cells preconditioned by highly aggressive GBC-SD cells in vitro and GBC-SD nude mouse xenografts in vivo.

Contribution of cancer stem cells to tumor vasculogenic mimicry

Vasculogenic mimicry (VM), a newly-defined pattern of tumor blood supply, provides a special passage without endothelial cells and is conspicuously different from angiogenesis and vasculogenesis. The biological features of the tumor cells that form VM remain unknown. Cancer stem cells (CSCs) are believed to be tumor-initiating cells, capable of self-renewal and multipotent differentiation, which resemble normal stem cells in phenotype and function. Recently CSCs have been shown to contribute to VM formation as well as angiogenesis. These findings challenge the previous understanding of the cellular basis of VM formation. In this review, we present evidence for participation of CSCs in VM formation. We also discuss the potential mechanisms and possible interaction of CSCs with various elements in tumor microenvironment niche. Based on the importance of VM in tumor progression, it constitutes a novel therapeutic target for cancer.

Regulation of cancer aggressive features in melanoma cells by microRNAs

MicroRNAs (miRNAs) are small non-coding RNAs with regulatory roles, which are involved in a broad spectrum of physiological and pathological processes, including cancer. A common strategy for identification of miRNAs involved in cell transformation is to compare malignant cells to normal cells. Here we focus on identification of miRNAs that regulate the aggressive phenotype of melanoma cells. To avoid differences due to genetic background, a comparative high-throughput miRNA profiling was performed on two isogenic human melanoma cell lines that display major differences in their net proliferation, invasion and tube formation activities. This screening revealed two major cohorts of differentially expressed miRNAs. We speculated that miRNAs up-regulated in the more-aggressive cell line contribute oncogenic features, while the down-regulated miRNAs are tumor suppressive. This assumption was further tested experimentally on five candidate tumor suppressive miRNAs (miR-31, -34a, -184, -185 and -204) and on one candidate oncogenic miRNA (miR-17-5p), all of which have never been reported before in cutaneous melanoma. Remarkably, all candidate Suppressive-miRNAs inhibited net proliferation, invasion or tube formation, while miR-17-5p enhanced cell proliferation. miR-34a and miR-185 were further shown to inhibit the growth of melanoma xenografts when implanted in SCID-NOD mice. Finally, all six candidate miRNAs were detected in 15 different metastatic melanoma specimens, attesting for the physiological relevance of our findings. Collectively, these findings may prove instrumental for understanding mechanisms of disease and for development of novel therapeutic and staging technologies for melanoma.

Molecular regulation of vasculogenic mimicry in tumors and potential tumor-target therapy

“Vasculogenic mimicry (VM)”, is a term that describes the unique ability of highly aggressive tumor cells to express a multipotent, stem cell-like phenotype, and form a pattern of vasculogenic-like networks in three-dimensional culture. As an angiogenesis-independent pathway, VM and/or periodic acid-schiff-positive patterns are associated with poor prognosis in tumor patients. Moreover, VM is resistant to angiogenesis inhibitors. Here, we will review the advances in research on biochemical and molecular signaling pathways of VM in tumors and on potential anti-VM therapy strategy.

Vasculogenic mimicry and microcirculation in tumors

Vasculogenic mimicry (VM), a term that describes a novel form of angiogenesis-independent microcirculation pattern recently found in few highly aggressive tumors, is formed by tumor cells, rather than endothelial cells. VM is closely correlated with the invasiveness, metastasis and prognosis of related tumors. The presence of VM is associated with an embryonic like phenotype acquired by tumor cells and the biological effects of many proteins. Furthermore, tumor microenvironment also plays an important role in the development of VM. Here, we will review the advances in research on the characteristic, formative mechanisms and clinical significance of VM.

Tumour vascularization: sprouting angiogenesis and beyond

Tumour angiogenesis is a fast growing domain in tumour biology. Many growth factors and mechanisms have been unravelled. For almost 30 years, the sprouting of new vessels out of existing ones was considered as an exclusive way of tumour vascularisation. However, over the last years several additional mechanisms have been identified. With the discovery of the contribution of intussusceptive angiogenesis, recruitment of endothelial progenitor cells, vessel co-option, vasculogenic mimicry and lymphangiogenesis to tumour growth, anti-tumour targeting strategies will be more complex than initially thought. This review highlights these processes and intervention as a potential application in cancer therapy. It is concluded that future anti-vascular therapies might be most beneficial when based on multimodal anti-angiogenic, anti-vasculogenic mimicry and anti-lymphangiogenic strategies.