Fig 1. MGMT activity measured by 6 methods in 7 cell lines.

A) MGMT activity reported as femtomoles of cleaved ³²P labeled O⁶-MeG containing oligonucleotide per microgram of protein in cell lysates. B) MGMT transcript levels normalized to TK6+MGMT. C) MGMT activity measured by FM-HCR, reported as the inverse of reporter expression. D) MGMT protein levels in cell lysates measured by quantitative western blotting and normalized to GAPDH protein levels. E) MGMT activity in cell lysates measured using the NR-1 fluorescent probe and reported in arbitrary units of fluorescence. F) Results of methylation specific PCR assays for MGMT promoter methylation; a value of 1 was assigned to the three cell lines in which promoter methylation was detected. Cell lines were ranked in ascending order of MGMT activity measured by the biochemical assay in panel A; the order and color scheme is preserved in each panel. Error bars represent the standard deviation of at least 3 measurements, and “ND” indicates that the 95% confidence interval for the measured parameter included zero. Data have been log transformed for optimal data visualization.