Pleiotropic function of ezrin in human metastatic melanomas

Abstract

The membrane cytoskeleton cross-linker, ezrin, has recently been depicted as a key regulator in the progression and metastasis of several pediatric tumors. Less defined appears the role of ezrin in human adult tumors, especially melanoma. We therefore addressed ezrin involvement in the metastatic phenotype of human adult metastatic melanoma cells. Our results show that cells resected from melanoma metastatic lesions of patients, display marked metastatic spreading capacity in SCID mice organs. Stable transfection of human melanoma cells with an ezrin deletion mutant comprising only 146 N-terminal aminoacids led to the abolishment of metastatic dissemination. In vitro experiments revealed ezrin direct molecular interactions with molecules related to metastatic functions such as CD44, merlin and Lamp-1, consistent with its participation to the formation of phagocitic vacuoles, vesicular sorting and migration capacities of melanoma cells. Moreover, the ezrin fragment capable of binding to CD44 was shorter than that previously reported, and transfection with the ezrin deletion mutant abrogated plasma membrane Lamp-1 recruitment. This study highlights key involvement of ezrin in a complex machinery, which allows metastatic cancer cells to migrate, invade and survive in very unfavorable conditions. Our in vivo and in vitro data reveal that ezrin is the hub of the metastatic behavior also in human adult tumors. ' UICCKey words: CD44; merlin; Lamp-1; phagocytic vacuole; organelle acidity The molecular events governing progression from a primary tumor to an invasive, malignant tumor remain poorly defined despite intense scientific endeavor mostly due to molecular biology and biochemical data collected from non human models. 1 The metastatic phenomenon is characterized by a cascade of events that assumes the existence of very harmful cells within the primitive tumor mass. These cells must acquire the ability to breach underlying basement membrane, migrate through interstitial stroma, gain access to and migrate through blood or lymphatic vessels, attach, enter, survive and proliferate within metastatic organs.Mounting evidence suggesting that ezrin contributes to tumor metastasis promotion, arose mainly from experiments employing syngeneic implantation models correlated to gene expression profiling performed on pediatric tumors. 1,2 In human tumors, ezrin deregulation or impaired functionality is related to poor prognosis. [3][4][5][6][7][8][9] Ezrin belongs to the MERM family of cytoskeleton-associated proteins 10 and functions as a linker between the actin cortical cytoskeleton and various membrane-bound molecules 11,12 through its C-terminal and N-terminal domains, respectively.ERM proteins are implicated in a wide variety of important cellular processes. 10,13-18 Notably, ezrin is primarily involved in both cell-to-cell adhesion and cell adhesion to the ECM through association with ICAMs, CD44, E-cadherin and b-catenin. 12,19 To this family belongs also the tumor suppressor merlin (NF-2, schwannomin), whose loss is r...

Knockdown of Ezrin by RNA Interference Reverses Malignant Behavior of Human Pancreatic Cancer Cells in Vitro

“…Previous studies have reveal that the level of Ezrin expression is positively related to the degree of malignancy in many tumors (Ilmonen et al, 2005;Li et al, 2008;Federici et al, 2009). And over expression of Ezrin usually correlates with a poor prognosis.…”

“…But aberrant expression of Ezrin, especially over expression, has been found associated closely with malignant tumors (Bruce et al, 2007). Ezrin was over expression in melanoma and the level of expression was parallel with its thickness and invasive ability (Ilmonen et al, 2005;Federici et al, 2009). And there is a positive correlation between Ezrin overexpression and the metastatic potential of human breast cancer cells .…”

Model membranes to shed light on the biochemical and physical properties of ezrin/radixin/moesin

“…Ezrin is also reported to interact with podoplanin, a small membrane mucin induced in oral squamous cell carcinomas, which colocalizes with ezrin [40] and induces an epithelial-mesenchymal transition in an ezrindependent manner [41]. Finally, we can mention that molecular interactions with ezrin were shown to allow membrane localization of Lamp-1 (also known as CD107a) [30], a heavily glycosylated transmembrane protein, involved in adhesion of cancer cells to the extracellular matrix. This membrane localization correlated with a high metastatic potential.…”

“…Clinical studies have shown that ezrin overexpression also correlated with adult tumor metastasis. Ezrin overexpression increased migration of metastatic melanoma [30], pancreatic cancer cells [31], or hepatocellular carcinoma [32]. Conversely, ezrin silencing or inhibition contributed to decreased cell motility [33][34][35][36].…”

FLT3-driven redox-modulation of Ezrin regulates leukaemic cell migration

“…Ezrin is also of interest from a cancer perspective, with an established role in metastasis (Brambilla and Fais, 2009;Fais, 2004;Federici et al, 2009;Zhou et al, 2010a) and an emerging role in proliferative signalling (Gautreau et al, 1999;Heiska et al, 2011;Kishore et al, 2005;Srivastava et al, 2005). Ezrin has been previously shown to be increased in leukaemic cells (Monni et al, 2008) and has been identified as a target of oncogenic signalling from extracellular signalling mediators PDGF, EGF and HGF as well as intracellular oncogenic kinases Src, Lck and Rho (Crepaldi et al, 1997;Fazioli et al, 1993;Monni et al, 2008).…”