Mitochondrial structure alteration in human prostate cancer cells upon initial interaction with a chemopreventive agent phenethyl isothiocyanate

Abstract

BackgroundPhenethyl isothiocyanate (PEITC), present naturally in cruciferous vegetables, is a chemopreventive agent. It blocks initiation and post-initiation progression of carcinogenesis. Mechanism study in human prostate cancer cells revealed that PEITC is a dual inhibitor of aberrant DNA hypermethylation and histone deacetylases, reactivating silenced genes and regulating the androgen-mediated growth of tumor cells. The identity of the cellular organelle that initially interacts with PEITC has not been fully described.MethodsHuman prostate cancer LNCaP cells were exposed to PEITC and the effects on cellular fine structure examined by transmission electron microscopic studies. Alteration of mitochondrial membrane potential and cytochrome c release were evaluated as early events of apoptosis, and the TUNEL method for quantifying apoptotic cells. Mitochondria were isolated for determining their protein expression.ResultsUltrastructural analyses have revealed condensed mitochondria and a perturbed mitochondrial cristae structure, which assumed a rounded and dilated shape within 4-hours of PEITC contact, and became more pronounced with longer PEITC exposure. They presented as the most prominent intracellular alterations in the early hours. Mitochondria structure alterations were demonstrated, for the first time, with the isothiocyanates. An increase in the number of smooth endoplasmic reticulum and vacuoles were also noted that is consistent with the presence of autophagy. Early events of apoptosis were detected, with cytochrome c released along with the appearance of mitochondrial alteration. Mitochondrial membrane potential was disrupted within 18 hours of PEITC exposure, preceding the appearance of apoptotic cells with DNA strand breaks. In parallel, the expression of the mitochondrial class III ß-tubulin in the outer membrane, which associates with the permeability transition pore, was significantly reduced as examined with isolated mitochondria.ConclusionMitochondria may represent the organelle target of the isothiocyanates, indicating that the isothiocyanates may be mitochondria-interacting agents to inhibit carcinogenesis.

Japonicone A inhibits the growth of non-small cell lung cancer cells via mitochondria-mediated pathways

“…Our results showed that japonicone A treatment decreased the ΔΨm in all NSCLC cell lines, which indicates that japonicone A-induced apoptosis in NSCLC cells occurs via the mitochondria-related pathway. The disruption of the ΔΨm is recognized as an early stage of apoptosis, where the release of cytochrome c from mitochondria signals the initiation of apoptosis [15,16]. The mitochondria-dependent pathway is regulated by Bcl-2 family proteins, which are involved in apoptosis involving the pro-apoptotic proteins Bax [17,18].…”

Histone and Non-Histone Targets of Dietary Deacetylase Inhibitors

“…PEITC has been found to affect both promoter demethylation and the chromatin states in prostate cancer cells, re-activating genes such as glutathione S-transferase P1 (GSTP1) 177, 178 . Recently, Chang et al .…”

Roles of Autophagy Induced by Natural Compounds in Prostate Cancer

“…Moreover, PEITC oral administration retarded the growth of PCa xenografts in nude mice, reduced the incidence of poorly differentiated tumors and increased the TUNEL-positive apoptotic bodies in PC-3 xenografts and TRAMP mice [ 44 , 45 , 83 , 84 ]. Hallmarks of autophagy have been characterized in vitro and in vivo : PCa cells (LNCaP and PC-3), but not normal prostate epithelial cell line (PrEC), treated with 2.5–5 μ M PEITC exhibited significant accumulation of AVOs and enhanced processing and punctuate localization of LC3 [ 43 , 44 , 87 ]; increased expression and cleavage of LC3 were also revealed in tumor sections from mice with PC-3 xenografts gavaged with 9 μ M PEITC and from TRAMP mice fed 3 μ mol PEITC/g diet [ 44 , 45 ]. Both PEITC-induced autophagy and apoptosis in LNCaP and PC-3 cell lines were strongly dependent on Atg5 protein level [ 44 ], thus proving an interrelation between the two pathways activated by PEITC treatment.…”