Knockdown of GLI1 decreases proliferation of claudin-low cell lines. (A) Western blot of cells infected with retrovirus expressing either non-targeting shRNA (NT), or shRNA targeted against GLI1 (#1, #2). Cells were infected, and selected for three days prior to blotting. GAPDH serves as a loading control. Quantification is relative to NT for each cell line. Blot is representative of three independent experiments. (B) Plot of GLI1 transcript levels in response to the shRNAs and treatment described in A). Error bars represent the standard error between three independent experiments. (C) Light microscopy images of MDA.MB.157 cells infected with either non-targeting (NT) or GLI1 -directed shRNA. Scale bars indicate 100 μm. (D, E) Plot detailing the proliferation of MDA.MB.436 cells (D) or BT549 cells (E) infected with the indicated retroviruses and grown in selection media. GAPDH, glyceraldehyde phosphate dehydrogenase; GLI1, glioma-associated oncogene 1; sh, short hairpin.