PDE6D and cancer: Current PDE6Di are still at the hit stage and havevarious problems, such as poor solubility, metabolic instability,and off-target issues.16,17 This makes the interpretationof phenotypic data and validation of PDE6D as a drug target in vivodifficult.7 Together with the broad cargospectrum of PDE6D, which involves far more prenylated proteins thanK-Ras, it is almost impossible to tell in which cancer type PDE6Dishould be applied.