To evaluate if the canonical Ras/MAPK and PI3/Akt pathways are constitutively activated in SCLC cells, cells were cultured for 24 h either in the presence or absence of serum, or for 24 h in the absence of serum and finally for 20 min in the presence of serum and then analyzed for the expression of phosphorylated ERK1/2 (pERK1/2) or Akt (pAkt) (Fig. 6A). Here, MAPK3 is linked to small cell lung carcinoma.