Invasion, attachment, and proliferation assay of glioblastoma cells. All assays were performed with four different glioblastoma cell lines: U87, U251, U373, and C6 (Top to bottom). Values in (A) and (B) are expressed as a percentage of corresponding parental line data. (A) Invasion: IM-3 subpopulations were compared to their parental lines. (B) Attachment: Cells adherent to Matrigel® after 4 h were stained with hematoxylin QS and counted. (C) Proliferation: The rate of cell proliferation was evaluated with CellTiter 96 Aqueous One Solution (Promega) at five different time points, 4 h, 24 h, 48 h, 72 h and 96 h after seeding cells. Triangles - IM-3 lines, squares - parental. Data are represented as means ± SD (n = 3). P, parental cells; IM3, IM3 cells; IM3, IM3 cell line; **, p < 0.01.