TP53 and neoplasm: These observations are in complete contradiction with earlier findings which have shown that the cytosolic fraction of β-catenin is degraded by Siah1 and thus, Siah1 act as a tumor suppressor.9, 10, 47 As Siah1 can be upregulated in a p53-dependent manner,20, 48, 49 association of Siah1 with apoptosis is also widely accepted.