Akt is constitutively activated in MCL cell lines. Serum-depletion experiments were performed with all 4 MCL cell lines. Cells were grown for 48 hours with (FBS +) or without serum (FBS -). Western blot analysis with p-Akt under serum starvation shows no significant decrease of p-Akt in MCL cell lines (shown are Granta 519, NCEB-1, and Z138C). In contrast, p-Akt levels in the Burkitt cell line BJAB are dramatically decreased under serum-starvation conditions. Total Akt levels are shown as loading control.