PSEN1 and melanoma: Since lower PS-1 expression could translate into increased Wnt activity, we also analyzed the lysates from the aggressive melanoma cells for P-β-catenin and found that Sk-Mel28, A375, and C8161 also expressed 54%, 71%, and 57%, respectively, of the P-β-catenin level detected in lysates from WM1552C (Figure 1D).