Reflecting the inability of idelalisib to suppress MCC-21 cell proliferation (Fig. 2A), we found that idelalisib had little effect on AKT and mTOR activation in this cell line at both 5 nM and 50 nM concentrations after treatment for 3 and 24 hours (lower panel in Fig. 4B). This evidence concerns the gene AKT1 and Merkel cell skin cancer.