DICER1 and Merkel cell skin cancer: We transfected codon-optimized LT (LTco), tumor-derived truncated LT (LT339), and codon-optimized sT (sTco) into MCPyV− MCC cell lines and evaluated the effect on expression levels of DROSHA, DGCR8, DICER1, and TARBP2 using western blotting (Figures 1A and S1).