Several genes known to be downstream of p53 pathway, namely btg1, btg2, and stk17al53–55, were downregulated to an indistinguishable level with that in tumor cells with p53 mutation (Fig. 6A, top; Fig. 6B), suggesting that p53 activity might be lost during tumorigenesis even in the wild-type setting. This evidence concerns the gene BTG1 and neoplasm.