Expression of EREG in human glioma cell lines. (a) EREG immunoreactivity was measured by ELISA in culture media conditioned by glioblastoma cell lines (U87, SF126, SF188), immortalized/non-tumorigenic human astrocytes (NHA/TS) and the NHA/TS tumor variant expressing the Hras oncogene (NHA/TSR). The dotted line represents the limit of detection of the measure. The tumorigenic potential of each cell type was evaluated by immunohistochemistry after intracranial implantation of 250 000 cells and analysis of tumor progression at days 10, 20, 30 and 60 post-implantation. (+) tumorigenic, (−) not tumorigenic. (b) EREG mRNA expression was represented as fold induction in glioma cells vs. NHATS cells. qPCR was performed using HPRT1 as reference gene.