The present study shows that oral gavage of 6 Mmol D,Lsulforaphane (SFN), a synthetic analogue of cruciferous vegetable-derived L isomer, thrice per week beginning at 6 weeks of age, significantly inhibits prostate carcinogenesis and pulmonary metastasis in TRAMP mice without causing any side effects. The incidence of the prostatic intraepithelial neoplasia and well-differentiated (WD) carcinoma were f23% to 28% lower (P < 0.05 compared with control by MannWhitney test) in the dorsolateral prostate (DLP) of SFNtreated mice compared with controls, which was not due to the suppression of T-antigen expression. The area occupied by the WD carcinoma was also f44% lower in the DLP of SFNtreated mice relative to that of control mice (P = 0.0011 by Mann Whitney test). Strikingly, the SFN-treated mice exhibited f50% and 63% decrease, respectively, in pulmonary metastasis incidence and multiplicity compared with control mice (P < 0.05 by t test). The DLP from SFN-treated mice showed decreased cellular proliferation and increased apoptosis when compared with that from control mice. Additionally, SFN administration enhanced cytotoxicity of cocultures of natural killer (NK) cells and dendritic cells (DC) against TRAMP-C1 target cells, which correlated with infiltration of T cells in the neoplastic lesions and increased levels of interleukin-12 production by the DC. In conclusion, the results of the present study indicate that SFN administration inhibits prostate cancer progression and pulmonary metastasis in TRAMP mice by reducing cell proliferation and augmenting NK cell lytic activity.

In this transgenic model, dietary PEITC suppressed prostate cancer progression by induction of autophagic cell death. Potential biomarkers to assess the response to PEITC treatment in plasma were identified.

Phenethyl isothiocyanate (PEITC) is a promising cancer chemopreventive agent but the mechanism of its anticancer effect is not fully understood. We now show, for the first time, that PEITC treatment triggers Atg5-dependent autophagic and apoptotic cell death in human prostate cancer cells. Exposure of PC-3 (androgen independent, p53 null) and LNCaP (androgen responsive, wild-type p53) human prostate cancer cells to PEITC resulted in several specific features characteristic of autophagy, including appearance of membranous vacuoles, formation of acidic vesicular organelles, and cleavage and recruitment of microtubule-associated protein 1 light chain 3 (LC3) to autophagosomes. A normal human prostate epithelial cell line (PrEC) was markedly more resistant toward PEITC-mediated cleavage and recruitment of LC3 compared with prostate cancer cells. Although PEITC treatment suppressed activating phosphorylations of Akt and mammalian target of rapamycin (mTOR), which are implicated in regulation of autophagy by different stimuli, processing and recruitment of LC3 was only partially/marginally reversed by ectopic expression of constitutively active Akt or overexpression of mTOR-positive regulator Rheb. The PEITCmediated apoptotic DNA fragmentation was significantly attenuated in the presence of a pharmacologic inhibitor of autophagy (3-methyl adenine). Transient transfection of LNCaP and PC-3 cells with Atg5-specific small interfering RNA conferred significant protection against PEITC-mediated autophagy as well as apoptotic DNA fragmentation. A xenograft model using PC-3 cells and Caenorhabditis elegans expressing a lgg-1:GFP fusion protein provided evidence for occurrence of PEITC-induced autophagy in vivo. In conclusion, the present study indicates that Atg5 plays an important role in regulation of PEITC-induced autophagic and apoptotic cell death.

Purpose-Present study was undertaken to elucidate the mechanism of cellular responses to D,Lsulforaphane (SFN), a highly promising cancer chemopreventive agent.Methods-Mitochondrial DNA deficient Rho-0 variants of LNCaP and PC-3 cells were generated by culture in the presence of ethidium bromide. Apoptosis was assessed by analysis of cytoplasmic histone-associated DNA fragmentation and activation of caspase-3. Immunoblotting was performed to determine the expression of apoptosis-and cell cycle-regulating proteins. Generation of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and cell cycle distribution were measured by flow cytometry.Results-The Rho-0 variants of LNCaP and PC-3 cells were significantly more resistant to SFNinduced ROS generation, apoptotic DNA fragmentation, disruption of MMP, cytosolic release of cytochrome c, and G2/M phase cell cycle arrest compared with corresponding wild-type cells. SFNinduced autophagy, which serves to protect against apoptotic cell death in PC-3 and LNCaP cells, was also partially but markedly suppressed in Rho-0 variants compared with wild-type cells. SFN statistically significant inhibited activities of mitochondrial respiratory chain enzymes in LNCaP and PC-3 cells.Conclusion-These results indicate, for the first time, that mitochondria-derived ROS serve to initiate diverse cellular responses to SFN exposure in human prostate cancer cells.