EGFR regulates tumorsphere formation in HNSCC cell lines and in a putative cancer stem cell culture.

<p>(A) EGF increased the rate of sphere formation in a dose-dependent fashion in 22B and HN-1 cells, while addition of 2 µM gefitinib significantly decreased sphere formation. (B) EGF increased the rate of sphere formation in JLO-1, a putative cancer stem cell culture. Error bars represent SEM. Gefitinib (0 to 2 µM) reduced sphere formation in a dose-dependent fashion in JLO-1. (C) Brightfield micrographs showing sphere formation in 22B and HN-1 after treatment with Gefitinib or EGF. (D) Brightfield micrographs showing sphere formation in JLO-1 after treatment with Gefitinib or EGF. (E) MTS cell viability assay demonstrating negligible effect of Gefitinib (Iressa) on cell viability at doses of up to 2 µM, showing that the observed decrease in sphere formation is not due to lower cell viability.