Different Effects of Human Umbilical Cord Mesenchymal Stem Cells on Glioblastoma Stem Cells by Direct Cell Interaction or Via Released Soluble Factors.

Adriana Bajetto,Alessandra Pattarozzi,Alessia Bosio,Alessandro Corsaro,Monica Gatti,Antonio Daga,Valerio Pisaturo,Federica Barbieri,Rodolfo Sirito,Tullio Florio

doi:10.3389/fncel.2017.00312

Adriana Bajetto, Alessandra Pattarozzi + Show 8 more

Open Access

https://doi.org/10.3389/fncel.2017.00312

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Abstract

Glioblastoma (GBM), the most common primary brain tumor in adults, is an aggressive, fast-growing and highly vascularized tumor, characterized by extensive invasiveness and local recurrence. In GBM and other malignancies, cancer stem cells (CSCs) are believed to drive invasive tumor growth and recurrence, being responsible for radio- and chemo-therapy resistance. Mesenchymal stem cells (MSCs) are multipotent progenitors that exhibit tropism for tumor microenvironment mediated by cytokines, chemokines and growth factors. Initial studies proposed that MSCs might exert inhibitory effects on tumor development, although, to date, contrasting evidence has been provided. Different studies reported either MSC anti-tumor activity or their support to tumor growth. Here, we examined the effects of umbilical cord (UC)-MSCs on in vitro GBM-derived CSC growth, by direct cell-to-cell interaction or indirect modulation, via the release of soluble factors. We demonstrate that UC-MSCs and CSCs exhibit reciprocal tropism when co-cultured as 3D spheroids and their direct cell interaction reduces the proliferation of both cell types. Contrasting effects were obtained by UC-MSC released factors: CSCs, cultured in the presence of conditioned medium (CM) collected from UC-MSCs, increased proliferation rate through transient ERK1/2 and Akt phosphorylation/activation. Analysis of the profile of the cytokines released by UC-MSCs in the CM revealed a strong production of molecules involved in inflammation, angiogenesis, cell migration and proliferation, such as IL-8, GRO, ENA-78 and IL-6. Since CXC chemokine receptor 2 (CXCR2), a receptor shared by several of these ligands, is expressed in GBM CSCs, we evaluated its involvement in CSC proliferation induced by UC-MSC-CM. Using the CXCR2 antagonist SB225002, we observed a partial but statistically significant inhibition of CSC proliferation and migration induced by the UC-MSC-released cytokines. Conversely, CXCR2 blockade did not reduce the reciprocal tropism between CSCs and UC-MSCs grown as spheroids. In conclusion, we show that direct (cell-to-cell contact) or indirect (via the release of soluble factors) interactions between GBM CSCs and UC-MSCs in co-culture produce divergent effects on cell growth, invasion and migration, with the former mainly causing an inhibitory response and the latter a stimulatory one, involving a paracrine activation of CXCR2.

Highlights

Glioblastoma (GBM, astrocytoma grade IV according to the World Health Organization (WHO) classification) is the most common and aggressive brain tumor, characterized by rapid growth and poor prognosis because of outstanding characteristics of invasiveness and recurrence (Brat et al, 2007; Verhaak et al, 2010)
The morphology of nuclei counterstained with DAPI confirmed the absence of apoptosis in both cell types. These results clearly show that direct cell-to-cell interaction of co-cultured cancer stem cells (CSCs) and umbilical cord (UC)-Mesenchymal stem cells (MSCs) causes a reduction of proliferation rate of both cell types
In vitro studies demonstrated MSCs to possess direct anti-tumor properties, impairing the growth of GBM cell lines and patient-derived primary GBM cultures, while the co-injection of MSCs and GBM cells resulted in a significant reduction of volume and vascularization of the tumor developed in vivo (Ho et al, 2013)

Summary

Introduction

Glioblastoma (GBM, astrocytoma grade IV according to the WHO classification) is the most common and aggressive brain tumor, characterized by rapid growth and poor prognosis because of outstanding characteristics of invasiveness and recurrence (Brat et al, 2007; Verhaak et al, 2010). The benefits of radio- and chemo-therapy are limited by the presence of the blood-brain barrier and high toxicity of these treatments. Small populations of cancer cells, named cancer stem cells (CSCs), play a primary role in the development and recurrence of GBM and most of solid and hematological tumors. The presence of CSCs confers to GBM a great degree of phenotypic and cellular heterogeneity, and the resistance to chemo- and radio-therapy (Singh et al, 2004; Florio and Barbieri, 2012; Tanase et al, 2013; Codrici et al, 2016). When transplanted into immunocompromised mice, CSCs generate tumors that retain the same histological features and cell heterogeneity of the original neoplasia (Singh et al, 2004; Friedmann-Morvinski and Verma, 2014). A growing body of evidence supports CSC plasticity and the de-differentiation ability of non-CSC ‘‘differentiated’’ tumor cells into CSCs in response to microenvironmental factors (Friedmann-Morvinski, 2014; Suva et al, 2014)

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