Novel AR/AR-V7 and Mnk1/2 Degrader, VNPP433-3β: Molecular Mechanisms of Action and Efficacy in AR-Overexpressing Castration Resistant Prostate Cancer In Vitro and In Vivo Models

Cells. 2022 Aug 30;11(17):2699. doi: 10.3390/cells11172699.

Abstract

Prostate cancer (PCa) relies in part on AR-signaling for disease development and progression. Earlier, we developed drug candidate galeterone, which advanced through phase 2-clinical trials in treating castration-resistant PCa (CRPC). Subsequently, we designed, synthesized, and evaluated next-generation galeterone-analogs including VNPP433-3β which is potently efficacious against pre-clinical models of PCa. This study describes the mechanism of action of VNPP433-3β that promotes degradation of full-length AR (fAR) and its splice variant AR-V7 besides depleting MNK1/2 in in vitro and in vivo CRPC models that stably overexpresses fAR. VNPP433-3β directly engages AR within the cell and promotes proteasomal degradation of fAR and its splice variant AR-V7 by enhancing the interaction of AR with E3 ligases MDM2/CHIP but disrupting AR-HSP90 binding. Next, VNPP433-3β decreases phosphorylation of 4EBP1 and abates binding of eIF4E and eIF4G to 5' cap of mRNA by depleting MNK1/2 with consequent depletion of phosphorylated eIF4E. Finally, RNA-seq demonstrates modulation of multiple pathways that synergistically contribute to PCa inhibition. Therefore, VNPP433-3β exerts its antitumor effect by imposing 1) transcriptional regulation of AR and AR-responsive oncogenes 2) translational regulation by disrupting mRNA-5'cap-dependent translation initiation, 3) reducing AR half-life through enhanced proteasomal degradation in vitro and AR-overexpressing tumor xenografts in vivo.

Keywords: AR/AR-V7 degrader; MNK1/2-eIF4E; VNPP433-3β; androgen receptor; castration-resistant prostate cancer; lead next generation galeterone analog; prostate cancer transcriptome.

MeSH terms

  • Eukaryotic Initiation Factor-4E / genetics
  • Humans
  • Male
  • Prostatic Neoplasms, Castration-Resistant* / drug therapy
  • Prostatic Neoplasms, Castration-Resistant* / genetics
  • Prostatic Neoplasms, Castration-Resistant* / metabolism
  • Protein Isoforms / metabolism
  • RNA, Messenger / therapeutic use
  • Receptors, Androgen / metabolism

Substances

  • Eukaryotic Initiation Factor-4E
  • Protein Isoforms
  • RNA, Messenger
  • Receptors, Androgen