KRAS and central nervous system cancer: We previously detected that expression of K-ras, a brain-specific isoform of Ras and the most prominent oncogene of the MAPK pathway (Spandidos and Kerr, 1998; Johnson et al, 2001), was downregulated exclusively in the AS-11-treated populations of glioma cell lines (Nickl-Jockschat et al, 2007).