SMYD3 and cancer: Cancers defective in PTEN, as prostate cancers, can be sensitive to PARP inhibitors, due to the downregulation of RAD51. Since lysine methylase SMYD3, often overexpressed in tumors, regulates BRCA1/2 and DNA repair, the inhibition of SMYD3 with BCI-121 promotes cancer inhibition by PARP inhibitors such as olaparib [70].