Thus increased skin tumor formation [6] and the enhanced hematopoietic tumorigenesis in the Δex8 strain [12] as well as the enhanced Ras-induced transformation of Δex8 MEFs [6] might be due to a pro-oncogenic effect of the MK5/PRAK-Δex8 mutant protein rather than a result of lacking the wild type kinase and its postulated tumor suppressive properties. This evidence concerns the gene MAPKAPK5 and neoplasm.