RT Journal Article SR Electronic T1 MGMT Hypermethylation and MDR System in Glioblastoma Cancer Stem Cells JF Cancer Genomics - Proteomics JO Cancer Genomics Proteomics FD International Institute of Anticancer Research SP 171 OP 178 VO 9 IS 4 A1 VALENTINA CALDERA A1 MARTA MELLAI A1 LAURA ANNOVAZZI A1 ORIANA MONZEGLIO A1 ANGELA PIAZZI A1 DAVIDE SCHIFFER YR 2012 UL http://cgp.iiarjournals.org/content/9/4/171.abstract AB Background: Cancer stem cells (CSCs) in gliomas are associated with resistance to radio- and chemotherapy, based on O6-methylguanine-DNA methyltransferase (MGMT) hypermethylation and the Multidrug resistance (MDR) system activation. Materials and Methods: Samples from 21 glioblastomas (GBMs) were put in culture with growth factors or serum in order to obtain neurospheres or adherent cells. Both were genetically and immunohistochemically characterized for ATP-binding cassette, sub-family B (MDR/TAP), member 1 (ABCB1), ATP-binding cassette, sub-family C (CFTR/MRP), member 1 (ABCC1) and MGMT expression together with primary tumors. Results: ABCB1 expression was positive in endothelial cells of primary tumors. ABCC1 expression was variably positive in tumor cells and positive in neurospheres, and less expressed in adherent cells. MGMT was methylated and unmethylated in primary tumors and in neurospheres, respectively, and unmethylated in adherent cells. Conclusion: Methylation is an epigenetic event affecting progenitors before the separation of the two glia lineages and maximally the future initiating cells. ABCB1 expression is limited to endothelial cells, whereas ABCC1 expression could mark a minority of tumor cells approaching a stem-like status.