Exosomal L1CAM Stimulates Glioblastoma Cell Motility, Proliferation, and Invasiveness.

Karma R Pace,Deni S Galileo,Reetika Dutt

doi:10.3390/ijms20163982

Karma R Pace, Deni S Galileo + Show 1 more

Open Access

https://doi.org/10.3390/ijms20163982

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Abstract

Immunoglobulin superfamily protein L1CAM (L1, CD171) normally facilitates neuronal migration, differentiation, and axon guidance during development. Many types of cancers, including glioblastoma (GBM), also abnormally express L1, and this has been associated with poor prognosis due to increased cell proliferation, invasiveness, or metastasis. We showed previously that the soluble L1 ectodomain, which is proteolyzed from the transmembrane form, can stimulate proliferation and motility of GBM cells in vitro by acting through integrins and fibroblast growth factor receptors (FGFRs). Minute L1-decorated exosomal vesicles also are released by GBM cells and potentially could stimulate cell motility, proliferation, and invasiveness, but this needed to be demonstrated. In the present study, we aimed to determine if minute L1-decorated extracellular vesicles (exosomes) were capable of stimulating GBM cell motility, proliferation, and invasiveness. L1-decorated exosomes were isolated from the conditioned media of the human T98G GBM cell line and were evaluated for their effects on the behavior of glioma cell lines and primary tumor cells. L1-decorated exosomes significantly increased cell velocity in the three human glioma cells tested (T98G/shL1, U-118 MG, and primary GBM cells) in a highly quantitative SuperScratch assay compared to L1-reduced exosomes from L1-attenuated T98G/shL1 cells. They also caused a marked increase in cell proliferation as determined by DNA cell cycle analysis and cell counting. In addition, L1-decorated exosomes facilitated initial GBM cell invasion when mixed with non-invasive T98G/shL1 cells in our chick embryo brain tumor model, whereas mixing with L1-reduced exosomes did not. Chemical inhibitors against focal adhesion kinase (FAK) and fibroblast growth factor receptor (FGFR) decreased L1-mediated motility and proliferation to varying degrees. These novel data show that L1-decoratred exosomes stimulate motility, proliferation and invasion to influence GBM cell behavior, which adds to the complexity of how L1 stimulates cancer cells through not only soluble ectodomain but also through exosomes.

Highlights

IntroductionOf the 17,000 primary brain tumors diagnosed each year, approximately 60% are gliomas [1], which arise in the brain from the supporting glial cells or their precursors [2]
Tumors of the central nervous system (CNS) are a devastating disease
We previously showed that glioma cells released exosomes decorated with L1 [12], which raised the possibility that this, too, may be a source of L1 that could autocrine/paracrine stimulate glioma cell proliferation, motility, and invasion

Summary

Introduction

Of the 17,000 primary brain tumors diagnosed each year, approximately 60% are gliomas [1], which arise in the brain from the supporting glial cells or their precursors [2]. Low grade gliomas are characterized by cellular morphology and cause local effects that do not spread in the brain. High grade gliomas are malignant and can spread throughout the brain tissue. Glioblastoma multiforme, or glioblastoma, (GBM; grade IV) account for 15% of all brain tumors and are classified as such due to their extensive differentiation, high invasiveness, and high malignancy of the tumor [2,3,4]. The mean survival time of a patient from initial GBM diagnosis is approximately 15 months [5] due to their highly invasive nature and late diagnosis after a patient experiences headaches, seizures, memory loss, vision changes, and personality changes. Current treatments for GBM include surgery, radiation, and chemotherapy [3,5] but these are practically ineffective

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