A549 clone sensitivity to pemetrexed (200 nM) before and after IDO induction.

<p>Proliferation of each of 5 individual A549 cell clonal populations before <b>(Panel A)</b> and after <b>(Panel B)</b> IDO induction with IFNγ. A549 clonal populations were cultured with or without IFNγ (25 ng/ml) for 48 h, then with pemetrexed (200 nM), and enumerated 72 h later. <b>White bars</b>: A549 clones transfected with scrambled, non-targeting control shRNA. <b>Gray bars</b>: A549 cells transfected with anti-IDO shRNA. Each bar represents the mean of 3 values (<i>n</i> = 3) ± SD. Results are normalized to control cells not treated with pemetrexed, without (panel A) or with (panel B) IFNγ treatment. <b>Panel C</b>: Induction of IDO in A549 clonal cell induces resistance to pemetrexed (200 nM). Results were obtained from 3 or 2 independent clonal cell populations with scrambled, non-targeting control shRNA or anti-IDO shRNA, respectively. Each bar represents a mean of 9 (white bars) or 6 (black bars) values ± SEM. *Significant difference, Student's <i>t</i>-test, <i>p</i><0.05.