Purpose: Although most prostate cancers regress after androgen deprivation therapy is given at diagnosis, they eventually regrow in a castration resistant manner, spread systemically and end fatally. Thus, novel therapeutic compounds are needed for prostate cancer. We previously reported that methylation at histone H3 lysine 9 was increased in prostate cancer. In this study we examined the effects of the methyltransferase inhibitor adenosine dialdehyde (Sigma®) on the methylation state of histone H3 lysine 9 and AR gene expression as well as its possible usefulness for prostate cancer. Materials and Methods: The effect of adenosine dialdehyde on the methylation state of histone H3 lysine 9 and AR gene expression was examined by quantitative real-time polymerase chain reaction and Western blot. We compared methylation at histone H3 lysine 9 at the AR promoter region between androgen dependent and castration resistant prostate cancer by chromatin immunoprecipitation assay. The cytotoxic effect of adenosine dialdehyde on prostate cancer was also evaluated in vitro and in vivo. Results: Adenosine dialdehyde suppressed the monomethylation and dimethylation of histone H3 lysine 9 and inhibited Twist1 as well as androgen receptor expression, which are critical for the survival and growth of androgen dependent, androgen sensitive and castration resistant prostate cancer cells in which monomethylated histone H3 lysine 9 increased at the 5′ untranslated region of the AR gene. As a result, adenosine dialdehyde had a cytotoxic effect on androgen dependent, androgen sensitive and castration resistant prostate cancer cells in vitro. Adenosine dialdehyde also suppressed prostate cancer growth in vivo in a mouse xenograft model. Conclusions: Results indicate that the methyltransferase inhibitor adenosine dialdehyde is a promising, novel therapeutic compound for prostate cancer.
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