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

Proliferation of each of 5 individual A549 cell clonal populations before (Panel A) and after (Panel 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. White bars: A549 clones transfected with scrambled, non-targeting control shRNA. Gray bars: A549 cells transfected with anti-IDO shRNA. Each bar represents the mean of 3 values (n = 3) ± SD. Results are normalized to control cells not treated with pemetrexed, without (panel A) or with (panel B) IFNγ treatment. Panel C: 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 t-test, p