EFEMP1 suppresses malignant glioma growth and exerts its action within the tumor extracellular compartment

Yuanjie Hu,Marlon S Mathews,Kenneth R Hess,Mark E Linskey,Jodi Nelson,Mark Hamamura,Yi-Hong Zhou,Eric Siegel,Liping Yu,Daniel I Ro,Abhishek Chaturbedi,Nelson Hsu,Qinghua Zhang,Peter Dion Pioli,Bruce J Tromberg,Selma Alkafeef

doi:10.1186/1476-4598-10-123

Abstract

PurposeThere are conflicting reports regarding the function of EFEMP1 in different cancer types. In this study, we sought to evaluate the role of EFEMP1 in malignant glioma biology.Experimental DesignReal-time qRT-PCR was used to quantify EFEMP1 expression in 95 glioblastoma multiforme (GBM). Human high-grade glioma cell lines and primary cultures were engineered to express ectopic EFEMP1, a small hairpin RNA of EFEMP1, or treated with exogenous recombinant EFEMP1 protein. Following treatment, growth was assayed both in vitro and in vivo (subcutaneous (s.c.) and intracranial (i.c.) xenograft model systems).ResultsCox regression revealed that EFEMP1 is a favorable prognostic marker for patients with GBM. Over-expression of EFEMP1 eliminated tumor development and suppressed angiogenesis, cell proliferation, and VEGFA expression, while the converse was true with knock-down of endogenous EFEMP1 expression. The EFEMP1 suppression of tumor onset time was nearly restored by ectopic VEGFA expression; however, overall tumor growth rate remained suppressed. This suggested that inhibition of angiogenesis was only partly responsible for EFEMP1's impact on glioma development. In glioma cells that were treated by exogenous EFEMP1 protein or over-expressed endogenous EFEMP1, the EGFR level was reduced and AKT signaling activity attenuated. Mixing of EFEMP1 protein with cells prior to s.c. and i.c. implantations or injection of the protein around the established s.c. xenografts, both significantly suppressed tumorigenicity.ConclusionsOverall, our data reveals that EEFEMP1 suppresses glioma growth in vivo, both by modulating the tumor extracellular microenvironment and by altering critical intracellular oncogenic signaling pathways.

Highlights

Fibulins are a seven-member family of secreted glycoproteins, which are characterized by repeated epidermal growth-factor-like domains and a unique C-terminal structure [1]
Overexpression of EGF-containing fibulin-like extracellular matrix protein 1 (EFEMP1) eliminated tumor development and suppressed angiogenesis, cell proliferation, and VEGFA expression, while the converse was true with knock-down of endogenous EFEMP1 expression
Overall, our data reveals that EEFEMP1 suppresses glioma growth in vivo, both by modulating the tumor extracellular microenvironment and by altering critical intracellular oncogenic signaling pathways

Summary

Introduction

Fibulins are a seven-member family of secreted glycoproteins, which are characterized by repeated epidermal growth-factor-like domains and a unique C-terminal structure [1]. Different members of the fibulin family have been shown to demonstrate either tumor-suppressive or oncogenic activity [2]. In support of a possible tumor-suppression role, EFEMP1 was discovered to have an anti-angiogenic function via suppression of endothelial cell sprouting [3]. A potential cancer-promoting function of EFEMP1 was implied in two clinical studies; in one study, the level of EFEMP1 expression was correlated to poor prognosis for cervical cancer [10], while the other study demonstrated EFEMP1 over-expression in breast carcinoma [11]. The potentially variable tissuespecific effects of EFEMP1 on cancer patient prognosis are reflected in the corresponding tissue-derived cancer in vitro assays, revealing the ability of EFEMP1 to either activate [13] or suppress [9] AKT signaling activity in pancreatic or nasopharyngeal carcinoma cell lines, respectively

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