CCI-779 shows an inhibitory effect on cell survival of cisplatin-sensitive and -resistant HNSCC cell lines. (A) HNSCC cell lines were treated with increasing doses of CCI-779 (0.1 to 1000 ng/ml). After 72 h cell survival was determined by the MTT assay. (B) The same cell lines were treated with CCI-779 at 100 ng/ml for 7 days in long-term MTT assays (black bars, left scale). Their IC50 for cisplatin was as well evaluated in MTT assays (grey bars, right scale). Cells were then grouped in CCI-779-resistant (red) and -sensitive (green) lines using a cutoff of 50% cell survival. (A, B) Survival fractions for given treatments were calculated on the basis of the survival of non-treated cells. Each sample was done in triplicate and experiments were performed thrice.