Biomarkers of Response to PI3K Inhibitors Figure 1. In vitro sensitivity of the NCI-60 tumor cell line collection to GDC-0941. A, GI50 (in mM) of GDC-0941 for 60 cell lines are ordered from lowest to highest, with PIK3CA mutation status indicated with orange box underneath name of cell line. B, z-scores of cell line sensitivity are ordered from lowest to highest. z-scores of 0.8 and 20.8 are indicated by dashed orange line. C, GI50 (in mM) of GDC-0941 for 16 sensitive and resistant cell lines of epithelia origin are ordered from lowest to highest. D, z-scores of cell line sensitivity for 16 sensitive and resistant cell lines of epithelia origin are ordered from lowest to highest. z-scores of 0.8 and 20.8 are indicated by dashed orange line. doi:10.1371/journal.pone.0046518.g001 versus drug treated cell lines in which OGT or DDN were knocked down by siRNA treatment was performed using the F-test to determine if the fitted midpoint (log IC50) of the curves were statistically significant, with a significance cutoff of P,0.05 sufficient to reject the hypothesis. siRNA knockdown after 72 hours was validated by Western Blotting using primary antibodies to OGT (Sigma) or qRT-PCR using the Roche LightCycler480 as described previously [23] using the following primers to DDN (59-TGAACAGTGGTAGCGACAGC-39 (for- ward), 59-GGAGCTATCTCGGTGCCTG-39 (reverse), 59-FAM- ATCCCCAAGCCAAAGCTACAGGGA-39-BHQ (probe)) and to the endogenous control, ACTB (59-CAGCAGATGTGGAT- CAGCAAG-39 (forward), 59-GCATTTGCGGTGGACGAT-39 PLOS ONE | www.plosone.org 3 September 2012 | Volume 7 | Issue 9 | e46518