The canonical ERK1/2 and PI3/Akt pathways are most likely not involved in SSP-induced neuron-like differentiation because (i) in some cell lines the ERK1/2 pathways is not activated, but SSP still provokes the formation of neurite-like extensions, (ii) pharmacological inhibition of the constitutively activated PI3/Akt pathway in SCLC cells does not prevent neurite-like outgrowth. This evidence concerns the gene MAPK3 and small cell lung carcinoma.