Signalling events involved in the anti-MDR tumour effects of Cripto Mab on MDR CEM/A7R cells were examined by comparison of C4 and non-Pgp substrate AraC and their combination on the activation of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) proapoptotic pathways. This evidence concerns the gene MAPK9 and neoplasm.