Figure 2.

Hypoxia inhibits the mTOR pathway in HNSCC cells. (A) Representative serum-deprived HNSCC cell lines were subjected to normoxic (N) or hypoxic (H) conditions for 18 hours. Whole cell extracts were analyzed by Western blot analysis to determine the effects of hypoxia on the mTOR pathway in vitro. Hypoxia-induced mTOR substrate dephosphorylation in the HN13 and HN12 cell lines as judged by the reduction in pS6 expression. In HN6 cells, however, the mTOR pathway remained hyperactivated under both normoxic and hypoxic conditions as demonstrated by the sustained expression of pS6 protein. Increased HIF-1α expression positively validated the response to hypoxia in all three cell lines. Total S6 and α-tubulin expression are shown as sample loading controls. (B) The HNSCC cell lines cultured in the presence or absence of 10% fetal bovine serum were exposed to normoxic or hypoxic conditions for 18 hours. Whole cell extracts were analyzed by Western blot analysis to determine the expression levels of phosphorylated Akt. Total Akt is shown as loading control.