Skip to main content
. 2008 May 5;28(13):4285–4299. doi: 10.1128/MCB.01240-07

FIG. 1.

FIG. 1.

Serum-starved HeLa cells secrete an Akt-activating activity. (A) HeLa cells grown in serum-rich medium (10% FBS in DMEM) overnight were replenished with serum-free medium, and the phospho-Akt (S473) and phospho-Erk (Thr202/Tyr204) from the whole-cell lysates were examined at the indicated time points. (B) HeLa cells grown overnight in serum-rich medium were replenished with serum-free medium or serum-free medium with the indicated amount of IGF-1 for 20 min. The whole-cell lysates were analyzed for phospho-Akt and phospho-Erk. (C) The CM from serum-starved HeLa cells was collected every 12 h. Each CM sample was added to a new batch of HeLa cells that had been serum deprived for 30 min. After cells were incubated for 30 min, the ability of each CM to increase the level of phospho-Akt activity was determined. (D) The serum-free HeLa cell CM (36 h) was heat treated at 65°C for the indicated times, and cooled to room temperature for 30 min. The Akt-activating activity of heat-treated CM was analyzed as described in the legend to panel C. (E) The Akt-activating activity of untreated or heat-treated HeLa cell CM was determined in the presence of the indicated amounts of LY294002 or Akt inhibitor (7.2 μM).