CDKN1A and central nervous system cancer: However, disturbance in the expression of Waf-1 protein in cells which over-express non-functional wild-type p53 has been reported in gliomas and glioma cell lines (Pykett et al, 1998) and the lack of relationship between the expression of these two proteins has also been reported in colorectal carcinoma (Slebos et al, 1996) and breast carcinoma (Barbareschi et al, 1996).