Oleocanthal Attenuates Metastatic Castration-Resistant Prostate Cancer Progression and Recurrence by Targeting SMYD2

Simple Summary The Mediterranean, extra-virgin-olive-oil-rich diet ingredient S-(-)-oleocanthal (OC) has emerged as a potential inhibitor for the growth and relapse of the most aggressive prostate cancer type. This effect is mediated through suppression of important enzyme, SMYD2, that drives the activation of several downstream protein effectors. OC treatments reduced SMYD2 downstream substrates, which are critical for prostate cancer growth and relapse. OC is more advantageous than other reported SMYD2 inhibitors because it has shown potent anticancer activity in animal models. OC's anti-prostate-cancer effect was prominent compared with some standard drugs currently used to control prostate cancer. OC is a potential, novel natural compound appropriate for immediate use by prostate cancer patients and survivors as a nutraceutical or dietary supplement product. Metastatic castration-resistant prostate cancer (mCRPC) is the most aggressive prostate cancer (PC) phenotype. Cellular lysine methylation is driven by protein lysine methyltransferases (PKMTs), such as those in the SET- and MYND-containing protein (SMYD) family, including SMYD2 methylate, and several histone and non-histone proteins. SMYD2 is dysregulated in metastatic PC patients with high Gleason score and shorter survival. The Mediterranean, extra-virgin-olive-oil-rich diet ingredient S-(-)-oleocanthal (OC) inhibited SMYD2 in biochemical assays and suppressed viability, migration, invasion, and colony formation of PC-3, CWR-R1ca, PC-3M, and DU-145 PC cell lines with IC50 range from high nM to low mu M. OC's in vitro antiproliferative effect was comparable to standard anti-PC chemotherapies or hormone therapies. A daily, oral 10 mg/kg dose of OC for 11 days effectively suppressed the progression of the mCRPC CWR-R1ca cells engrafted into male nude mice. Daily, oral OC treatment for 30 days suppressed tumor locoregional and distant recurrences after the primary tumors' surgical excision. Collected OC-treated animal tumors showed marked SMYD2 reduction. OC-treated mice showed significant serum PSA reduction. For the first time, this study showed SMYD2 as novel molecular target in mCRPC, and OC emerged as a specific SMYD2 lead inhibitor. OC prevailed over previously reported SMYD2 inhibitors, with validated in vivo potency and high safety profile, and, therefore, is proposed as a novel nutraceutical for mCRPC progression and recurrence control.