Mesenchymal stem cells differentially affect the invasion of distinct glioblastoma cell lines

// Barbara Breznik 1, 2 , Helena Motaln 1 , Miloš Vittori 1 , Ana Rotter 1 , Tamara Lah Turnšek 1, 2, 3 1 Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, 1000 Ljubljana, Slovenia 2 International Postgraduate School Jozef Stefan, 1000 Ljubljana, Slovenia 3 Department of Biochemistry, Faculty of Chemistry and Chemical Engineering, University of Ljubljana, 1000 Ljubljana, Slovenia Correspondence to: Tamara Lah Turnšek, email: Tamara.Lah@nib.si Keywords: glioblastoma multiforme, proteases, mesenchymal stem cells, tumor heterogeneity, zebrafish model Received: November 25, 2016 Accepted: February 07, 2017 Published: March 09, 2017 ABSTRACT Glioblastoma multiforme are an aggressive form of brain tumors that are characterized by distinct invasion of single glioblastoma cells, which infiltrate the brain parenchyma. This appears to be stimulated by the communication between cancer and stromal cells. Mesenchymal stem cells (MSCs) are part of the glioblastoma microenvironment, and their ‘cross-talk’ with glioblastoma cells is still poorly understood. Here, we examined the effects of bone marrow-derived MSCs on two different established glioblastoma cell lines U87 and U373. We focused on mutual effects of direct MSC/glioblastoma contact on cellular invasion in three-dimensional invasion assays in vitro and in a zebrafish embryo model in vivo . This is the first demonstration of glioblastoma cell-type-specific responses to MSCs in direct glioblastoma co-cultures, where MSCs inhibited the invasion of U87 cells and enhanced the invasion of U373. Inversely, direct cross-talk between MSCs and both of glioblastoma cell lines enhanced MSC motility. MSC-enhanced invasion of U373 cells was assisted by overexpression of proteases cathepsin B, calpain1, uPA/uPAR, MMP-2, -9 and -14, and increased activities of some of these proteases, as determined by the effects of their selective inhibitors on invasion. In contrast, these proteases had no effect on U87 cell invasion under MSC co-culturing. Finally, we identified differentially expressed genes, in U87 and U373 cells that could explain different response of these cell lines to MSCs. In conclusion, we demonstrated that MSC/glioblastoma cross-talk is different in the two glioblastoma cell phenotypes, which contributes to tumor heterogeneity.