CXCR2 and glioblastoma: Altogether our results demonstrate 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, at least in part mediated by the paracrine activation of CXCR2 by its ligands GROs and IL-8, which emerged as main mediators of the indirect activation of cell proliferation.