KN-93 inhibits androgen receptor activity and induces cell death irrespective of p53 and Akt status in prostate cancer

Abstract

It has been suggested that the downregulation of AR expression should be considered the principal strategy for the treatment of hormone-refractory prostate cancer. We have previously shown that inhibition of AR induced PI3K-independent activation of Akt that was mediated by CaMKII. In this study, we found that the CaMKII inhibitor KN-93 has a broader effect on apoptosis than just inhibition of CaMKII: first, KN-93 inhibits AR activity and induces cell death in PCa cells after androgen deprivation when many other drugs fail to kill prostate cancer cells; second, KN-93 inhibits expression of the anti-apoptotic protein Mcl-1 and induces expression of the pro-apoptotic protein PUMA; third, KN-93-mediated cell death is p53-independent; and fourth, KN-93 induces the generation of ROS. The ROS induction allows KN-93 to circumvent the activation of Akt, which occurs in prostate cancer cells under androgen deprivation, since Akt could not inhibit ROS-mediated apoptosis. KN-93 also synergistically induces cell death in combination with low doses of doxorubicin and converts the phenotype of prostate cancer cells from TRAIL-resistant to -sensitive. These data suggest that KN-93 could be used for novel therapeutic approaches when hormonal therapy has failed.