Sulforaphane Inhibits Prostate Carcinogenesis and Pulmonary Metastasis in TRAMP Mice in Association with Increased Cytotoxicity of Natural Killer Cells

¹Department of Pharmacology and Chemical Biology, ²University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine; ³Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, Pittsburgh, Pennsylvania and ⁴Department of Pharmacology, Penn State Milton S. Hershey Medical Center, Hershey, Pennsylvania

^* To whom correspondence should be addressed. E-mail: singhs{at}upmc.edu.

	Abstract

The present study shows that oral gavage of 6 µmol D,L-sulforaphane (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 23% to 28% lower (P < 0.05 compared with control by Mann-Whitney test) in the dorsolateral prostate (DLP) of SFN-treated mice compared with controls, which was not due to the suppression of T-antigen expression. The area occupied by the WD carcinoma was also 44% lower in the DLP of SFN-treated mice relative to that of control mice (P = 0.0011 by Mann Whitney test). Strikingly, the SFN-treated mice exhibited 50% 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. [Cancer Res 2009;69(5):2117–25]

Key Words: sulforaphane, prostate cancer, chemoprevention

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