MGMT and glioma: Both glioma cell lines used did not express this enzyme, confirmed by quantitative PCR (Figure S2) and also reported in the literature.30, 31 For that reason, we decided to include another cell line from human astrocytes: the hTERT/E6/E7 HOXA9 cell line, transfected with the HOXA9 gene, described as presenting an aggressive behaviour and treatment resistance.27 This cell line showed a higher expression of MGMT gene compared to glioma cell lines (U251 and SW1088).