RESUMO
In 1999, The American Journal of Pathology published an article entitled "Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry," by Maniotis and colleagues, which ignited a spirited debate for several years and earned distinction as a citation classic. Tumor cell vasculogenic mimicry (VM) refers to the plasticity of aggressive cancer cells forming de novo vascular networks, which thereby contribute to perfusion of rapidly growing tumors, transporting fluid from leaky vessels, and/or connecting with the constitutional endothelial-lined vasculature. The tumor cells capable of VM share a plastic, transendothelial phenotype, which may be induced by hypoxia. Since VM was introduced as a novel paradigm for melanoma tumor perfusion, many studies have contributed new findings illuminating the underlying molecular pathways supporting VM in a variety of tumors, including carcinomas, sarcomas, glioblastomas, astrocytomas, and melanomas. Facilitating the functional plasticity of tumor cell VM are key proteins associated with vascular, stem cell, and hypoxia-related signaling pathways, each deserving serious consideration as potential therapeutic targets and diagnostic indicators of the aggressive, metastatic phenotype.
Assuntos
Mimetismo Molecular , Neoplasias/irrigação sanguínea , Neoplasias/terapia , Pesquisa Translacional Biomédica , Animais , Humanos , Metástase Neoplásica , Neoplasias/patologia , Células-Tronco Neoplásicas/patologia , Transdução de Sinais , Microambiente TumoralRESUMO
The greatest health threat from malignant melanoma is death due to metastatic disease. Consequently, the identification of markers predictive of metastatic disease is essential for identifying new therapeutic targets. EphA2, a protein tyrosine kinase receptor commonly expressed in epithelial cells, has been found to be overexpressed and constitutively active in melanoma tumor cells having a metastatic phenotype as characterized by increased invasion, proliferation and vasculogenic mimicry (VM). Based on this observation, we hypothesized that increased expression of EphA2 by melanoma tumor cells could promote these characteristics of a metastatic phenotype in addition to promoting tumorigenicity as a whole. We analyzed a panel of human melanoma tumor cell lines derived from patient tissues classified as primary (either radial growth phase or vertical growth phase) and/or metastatic for the expression of EphA2 and found a correlation between increased EphA2 expression and metastatic potential. Experiments using the most metastatic of the human melanoma cell lines demonstrated that downregulation of EphA2 results in a significant decrease in invasion, proliferation, clonogenicity and VM in vitro, in addition to suppressed tumorigenicity in an orthotopic mouse model. Lastly, utilization of a human phospho-kinase array revealed increased phosphorylation of several different protein kinases involved in mediating various aspects of cellular proliferation. To the best of our knowledge these results provide the first direct in vivo evidence demonstrating a role for EphA2 in promoting melanoma tumorigenicity and suggest EphA2 as a significant molecular target for the therapeutic intervention of malignant melanoma.
Assuntos
Melanoma/patologia , Metástase Neoplásica , Receptor EphA2 , Animais , Biomarcadores Tumorais , Linhagem Celular Tumoral , Proliferação de Células , Regulação para Baixo , Regulação Neoplásica da Expressão Gênica , Humanos , Melanoma/genética , Melanoma/metabolismo , Camundongos , Invasividade Neoplásica , Fosforilação , Análise Serial de Proteínas , Receptor EphA2/genética , Receptor EphA2/metabolismoRESUMO
During embryogenesis, the primordial microcirculation is formed through a process known as vasculogenesis. The term "vasculogenic mimicry" has been used to describe the manner in which highly aggressive, but not poorly aggressive melanoma tumor cells express endothelial and epithelial markers and form vasculogenic-like networks similar to embryonic vasculogenesis. Vasculogenic mimicry is one example of the remarkable plasticity demonstrated by aggressive melanoma cells and suggests that these cells have acquired an embryonic-like phenotype. Since the initial discovery of tumor cell vasculogenic mimicry by our laboratory, we have been focusing on understanding the molecular mechanisms that regulate this process. This review will highlight recent findings identifying key signal transduction events that regulate melanoma vasculogenic mimicry and their similarity to the signal transduction events responsible for promoting embryonic vasculogenesis and angiogenesis. Specifically, this review will focus on the role of the Eph receptors and ligands in embryonic vasculogenesis, angiogenesis, and vasculogenic mimicry.
Assuntos
Células-Tronco Embrionárias/citologia , Melanoma/irrigação sanguínea , Células-Tronco Neoplásicas/patologia , Receptores da Família Eph/fisiologia , Animais , Células-Tronco Embrionárias/fisiologia , Humanos , Ligantes , Melanoma/patologia , Melanoma/fisiopatologia , Modelos Biológicos , Células-Tronco Neoplásicas/fisiologia , Neovascularização Patológica , Transdução de SinaisRESUMO
Bidirectional cellular communication is integral to both cancer progression and embryological development. In addition, aggressive tumor cells are phenotypically plastic, sharing many properties with embryonic cells. Owing to the similarities between these two types of cells, the developing zebrafish can be used as a biosensor for tumor-derived signals. Using this system, we show that aggressive melanoma cells secrete Nodal (a potent embryonic morphogen) and consequently can induce ectopic formation of the embryonic axis. We further show that Nodal is present in human metastatic tumors, but not in normal skin, and thus may be involved in melanoma pathogenesis. Inhibition of Nodal signaling reduces melanoma cell invasiveness, colony formation and tumorigenicity. Nodal inhibition also promotes the reversion of melanoma cells toward a melanocytic phenotype. These data suggest that Nodal signaling has a key role in melanoma cell plasticity and tumorigenicity, thereby providing a previously unknown molecular target for regulating tumor progression.
Assuntos
Melanoma/patologia , Proteínas de Membrana/metabolismo , Neoplasias/metabolismo , Transdução de Sinais , Proteínas de Peixe-Zebra/metabolismo , Peixe-Zebra/embriologia , Animais , Blástula/transplante , Linhagem Celular Tumoral , Embrião não Mamífero , Proteínas de Fluorescência Verde/metabolismo , Humanos , Imuno-Histoquímica , Melanócitos/metabolismo , Melanócitos/patologia , Proteínas de Membrana/antagonistas & inibidores , Invasividade Neoplásica , Metástase Neoplásica , Transplante de Neoplasias , Oligonucleotídeos Antissenso/farmacologia , Transplante Heterólogo , Proteínas de Peixe-Zebra/antagonistas & inibidoresRESUMO
Focal adhesion kinase (FAK) mediates myriad cellular functions and has been found to be overexpressed in numerous human cancers. We recently explored the role of FAK in promoting the aggressive phenotype of melanoma cells, characterized by increased invasion, migration, and vasculogenic mimicry (VM) potential. We found FAK to be phosphorylated on its key tyrosine residues (397 and 576) in aggressive melanoma cells cultured on a three-dimensional type 1 collagen matrix in vitro, as well as in radial and vertical growth phase melanomas in situ. Furthermore, expressing FAK-related non-kinase (FRNK) in melanoma cells directly resulted in the inhibition of the aggressive phenotype, as demonstrated by decreased invasion, migration and VM potential, in part by blocking an Erk1/2 mediated signaling pathway. Additional data indicated that increased FAK activity may promote cellular proliferation and anchorage independent growth of aggressive melanoma. Together these observations implicate FAK as a promoter of the aggressive melanoma phenotype, thereby identifying a rational target for therapeutic intervention of malignant melanoma.
Assuntos
Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Melanoma/enzimologia , Melanoma/patologia , Transdução de Sinais , Proliferação de Células , Expressão Gênica , Humanos , Fenótipo , Proteínas Tirosina Quinases/genéticaRESUMO
The formation of matrix-rich, vasculogenic-like networks, termed vasculogenic mimicry (VM), is a unique process characteristic of highly aggressive melanoma cells found to express genes previously thought to be exclusively associated with endothelial and epithelial cells. This study contributes new observations demonstrating that VE-cadherin can regulate the expression of EphA2 at the cell membrane by mediating its ability to become phosphorylated through interactions with its membrane bound ligand, ephrin-A1. VE-cadherin and EphA2 were also found to be colocalized in cell-cell adhesion junctions, both in vitro and in vivo. Immunoprecipitation studies revealed that EphA2 and VE-cadherin could interact, directly and/or indirectly, during VM. Furthermore, there was no change in the colocalization of EphA2 and VE-cadherin at cell-cell adhesion sites when EphA2 was phosphorylated on tyrosine residues. Although transient knockout of EphA2 expression did not alter VE-cadherin localization, transient knockout of VE-cadherin expression resulted in the reorganization of EphA2 on the cells' surface, an accumulation of EphA2 in the cytoplasm, and subsequent dephosphorylation of EphA2. Collectively, these results suggest that VE-cadherin and EphA2 act in a coordinated manner as a key regulatory element in the process of melanoma VM and illuminate a novel signaling pathway that could be potentially exploited for therapeutic intervention.
Assuntos
Caderinas/metabolismo , Melanoma/irrigação sanguínea , Neovascularização Patológica/metabolismo , Receptor EphA2/metabolismo , Neoplasias Cutâneas/irrigação sanguínea , Antígenos CD , Caderinas/análise , Adesão Celular , Membrana Celular/química , Membrana Celular/metabolismo , Citoplasma/química , Citoplasma/metabolismo , Efrina-A1/metabolismo , Humanos , Junções Intercelulares/química , Junções Intercelulares/metabolismo , Melanoma/metabolismo , Oligonucleotídeos Antissenso/genética , Oligonucleotídeos Antissenso/farmacologia , Fosforilação , Receptor EphA2/análise , Receptor EphA2/genética , Transdução de Sinais , Neoplasias Cutâneas/metabolismo , Células Tumorais Cultivadas , Tirosina/metabolismoRESUMO
We have previously shown that lysyl oxidase (LOX) mRNA is up-regulated in invasive breast cancer cells and that catalytically active LOX facilitates in vitro cell invasion. Here we validate our in vitro studies by showing that LOX expression is up-regulated in distant metastatic breast cancer tissues compared with primary cancer tissues. To elucidate the mechanism by which LOX facilitates cell invasion, we show that catalytically active LOX regulates in vitro motility/migration and cell-matrix adhesion formation. Treatment of the invasive breast cancer cell lines, Hs578T and MDA-MB-231, with beta-aminopropionitrile (betaAPN), an irreversible inhibitor of LOX catalytic activity, leads to a significant decrease in cell motility/migration and adhesion formation. Conversely, poorly invasive MCF-7 cells expressing LOX (MCF-7/LOX32-His) showed an increase in migration and adhesion that was reversible with the addition of betaAPN. Moreover, a decrease in activated focal adhesion kinase (FAK) and Src kinase, key proteins involved in adhesion complex turnover, was observed when invasive breast cancer cells were treated with betaAPN. Additionally, FAK and Src activation was increased in MCF-7/LOX32-His cells, which was reversible on betaAPN treatment. Hydrogen peroxide was produced as a by-product of LOX activity and the removal of hydrogen peroxide by catalase treatment in invasive breast cancer cells led to a dose-dependent loss in Src activation. These results suggest that LOX facilitates migration and cell-matrix adhesion formation in invasive breast cancer cells through a hydrogen peroxide-mediated mechanism involving the FAK/Src signaling pathway. These data show the need to target LOX for treatment of aggressive breast cancer.
Assuntos
Neoplasias da Mama/patologia , Adesão Celular , Movimento Celular , Peróxido de Hidrogênio/metabolismo , Proteína-Lisina 6-Oxidase/fisiologia , Aminopropionitrilo/farmacologia , Neoplasias da Mama/enzimologia , Neoplasias da Mama/secundário , Catalase/farmacologia , Ativação Enzimática/efeitos dos fármacos , Feminino , Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Humanos , Invasividade Neoplásica , Recidiva Local de Neoplasia , Proteínas Proto-Oncogênicas pp60(c-src)/metabolismo , Transdução de Sinais , Células Tumorais CultivadasRESUMO
Malignant melanoma continues to remain a significant health threat, with death often occurring as a result of metastasis. The metastatic phenotype typically is characterized by augmented tumor cell invasion and migration in addition to tumor cell plasticity as shown by vasculogenic mimicry. Therefore, understanding the molecular mechanisms that promote an aggressive phenotype is essential to predicting the likelihood of metastasis at a stage when intervention may be possible. This study focuses on the role of focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase important for many cellular processes, including cell survival, invasion, and migration. We found FAK to be phosphorylated on its key tyrosine residues, Tyr397 and Tyr576, in only aggressive uveal and cutaneous melanoma cells, which correlates with their increased invasion, migration, and vasculogenic mimicry plasticity. Additionally, we confirmed the presence of FAK phosphorylated on Tyr397 and Tyr576 in both cutaneous and uveal melanoma tumors in situ. Examination of a functional role for FAK in aggressive melanoma revealed that disruption of FAK-mediated signal transduction pathways, through the expression of FAK-related nonkinase (FRNK), results in a decrease in melanoma cell invasion, migration, and inhibition of vasculogenic mimicry. Moreover, we found that FRNK expression resulted in a down-regulation of Erk1/2 phosphorylation resulting in a decrease in urokinase activity. Collectively, these data suggest a new mechanism involved in promoting the aggressive melanoma phenotype through FAK-mediated signal transduction pathways, thus providing new insights into possible therapeutic intervention strategies.
Assuntos
Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Melanoma/enzimologia , Melanoma/patologia , Linhagem Celular Tumoral , Movimento Celular/fisiologia , Regulação para Baixo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Humanos , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinases da Matriz Associadas à Membrana , Melanoma/genética , Metaloendopeptidases/metabolismo , Invasividade Neoplásica , Metástase Neoplásica , Fosforilação , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Neoplasias Cutâneas/enzimologia , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Transfecção , Ativador de Plasminogênio Tipo Uroquinase/metabolismo , Neoplasias Uveais/enzimologia , Neoplasias Uveais/genética , Neoplasias Uveais/patologiaRESUMO
Endothelial cells involved in vasculogenesis and angiogenesis are key targets in cancer therapy. Recent evidence suggests that tumor cells can express some genes typically expressed by endothelial cells and form extracellular matrix-rich tubular networks, phenomena known as vasculogenic mimicry. We examined the effects of three angiogenesis inhibitors (i.e., anginex, TNP-470, and endostatin) on vasculogenic mimicry in human melanoma MUM-2B and C8161 cells and compared them with their effects in human endothelial HMEC-1 and HUVEC cells. Anginex, TNP-470, and endostatin markedly inhibited vascular cord and tube formation by HMEC-1 and HUVEC cells in vitro, whereas tubular network formation by MUM-2B and C8161 cells was relatively unaffected. Endothelial cells expressed higher mRNA and protein levels for two putative endostatin receptors, alpha5 integrin and heparin sulfate proteoglycan 2, than melanoma cells, suggesting a mechanistic basis for the differential response of the two cell types to angiogenesis inhibitors. These findings may contribute to the development of new antivascular therapeutic agents that target both angiogenesis and tumor cell vasculogenic mimicry.
Assuntos
Inibidores da Angiogênese/farmacologia , Células Endoteliais , Endotélio Vascular/patologia , Melanoma/patologia , Neovascularização Patológica/tratamento farmacológico , Western Blotting , Cicloexanos , Endostatinas/farmacologia , Citometria de Fluxo , Humanos , Melanoma/irrigação sanguínea , Mimetismo Molecular/efeitos dos fármacos , O-(Cloroacetilcarbamoil)fumagilol , Peptídeos , Proteínas/farmacologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Sesquiterpenos/farmacologia , Células Tumorais CultivadasRESUMO
Vasculogenic mimicry (VM) describes the unique ability of highly aggressive melanoma tumor cells to express endothelial cell-associated genes (such as EphA2 and VE-cadherin) and form vasculogenic-like networks when cultured on a three-dimensional matrix. VM has been described in several types of aggressive tumors, including melanoma, prostate, breast, and ovarian carcinomas. However, the molecular underpinnings of this phenomenon remain somewhat elusive. In this study, we examined key molecular mechanisms underlying VM in aggressive human cutaneous and uveal melanoma. The data reveal that phosphoinositide 3-kinase (PI3K) is an important regulator of VM, specifically affecting membrane type 1 matrix metalloproteinase (MT1-MMP) and matrix metalloproteinase-2 (MMP-2) activity, critical in the formation of vasculogenic-like networks. Using specific inhibitors of PI3K, melanoma VM was abrogated coincident with decreased MMP-2 and MT1-MMP activity. Furthermore, inhibition of PI3K blocked the cleavage of laminin 5 gamma 2 chain, resulting in decreased levels of the gamma 2' and gamma 2x promigratory fragments. Collectively, these results indicate that PI3K is an important regulator of melanoma VM directly affecting the cooperative interactions of MMP-2, MT1-MMP, and laminin 5 gamma 2 chain and, thus, the remodeling of the tumor cell microenvironment. PI3K may represent an excellent target for therapeutic intervention of a novel signaling cascade underlying VM.
Assuntos
Metaloproteinase 2 da Matriz/metabolismo , Melanoma/irrigação sanguínea , Melanoma/enzimologia , Metaloendopeptidases/metabolismo , Fosfatidilinositol 3-Quinases/fisiologia , Humanos , Laminina/metabolismo , Metaloproteinases da Matriz Associadas à Membrana , Melanoma/patologia , Subunidades Proteicas , Células Tumorais CultivadasRESUMO
The molecular analysis of tumors, such as melanoma, has benefited significantly from microarray technology that can facilitate the classification of tumors based on the differential expression of genes. The data summarized in this review describe the molecular profile of aggressive cutaneous and uveal melanoma cells as that of multiple phenotypes similar to a pluripotent, embryonic-like stem cell. A noteworthy example of the plasticity of the aggressive melanoma cell phenotype is demonstrated by the ability of these tumor cells to engage in vasculogenic mimicry and neovascularization. A review of the current evidence demonstrating important cellular and molecular determinants of melanoma vasculogenic mimicry is presented. In addition, novel signaling pathways are discussed, involving VE-cadherin, EphA2, FAK, and PI 3-kinase, which promote cell migration, invasion, and matrix remodeling. The observations summarized in this review describe some of the key molecular events that regulate the process of melanoma vasculogenic mimicry and identify new signal transduction pathways that can serve as putative targets for therapeutic intervention.
Assuntos
Melanoma/irrigação sanguínea , Melanoma/patologia , Antígenos CD , Caderinas/fisiologia , Movimento Celular/fisiologia , Perfilação da Expressão Gênica , Humanos , Laminina/metabolismo , Melanoma/metabolismo , Mimetismo Molecular , Invasividade Neoplásica , Neovascularização Patológica , Receptor EphA2/fisiologia , Transdução de SinaisRESUMO
The gene-expression profile of aggressive cutaneous and uveal melanoma cells resembles that of an undifferentiated, embryonic-like cell. The plasticity of certain types of cancer cell could explain their ability to mimic the activities of endothelial cells and to participate in processes such as neovascularization and the formation of a fluid-conducting, matrix-rich meshwork. This ability has been termed 'vasculogenic mimicry'. How does vasculogenic mimicry contribute to tumour progression, and can it be targeted by therapeutic agents?
Assuntos
Endotélio Vascular/patologia , Melanoma/irrigação sanguínea , Neovascularização Patológica/etiologia , Neoplasias Cutâneas/irrigação sanguínea , Neoplasias Uveais/irrigação sanguínea , Animais , Humanos , Melanoma/patologia , Neoplasias Cutâneas/patologia , Neoplasias Uveais/patologiaRESUMO
Cutaneous melanoma has been increasing at an alarming rate over the past two decades, however, there are no acceptable histopathological markers that classify various stages of melanoma progression. Recently, the molecular analysis of cancer has contributed significantly to our understanding of the cellular and molecular underpinnings of tumor progression. The data summarized in this review describe the molecular signature of aggressive cutaneous melanoma cells as that of multiple phenotypes which may be similar to a pluripotent, embryonic-like phenotype. An example of the plasticity of this phenotype is demonstrated by the ability of aggressive melanoma cells to engage in vasculogenic mimicry and neovascularization. A review of the current data demonstrating important cellular and molecular determinants of human melanoma vasculogenic mimicry is presented. These findings should stimulate additional studies to address the biological relevance of the multiple molecular phenotypes expressed by aggressive melanoma cells which may lead to the development of new diagnostic markers and therapeutic targets for clinical intervention.