Background: DACH-Ac-Pt [(1R,2R-diaminocyclohexane)-(trans-diacetato)-(dichloro)-platinum(IV)] is a novel cisplatin (CDDP) analog, and we have evaluated its potential activity in human prostate cancers.

Methods: Cytotoxic, biochemical pharmacologic, cell cycle, and Western blot evaluations were conducted with platinum agents to assess the role of p53 genotype and androgen-dependence status on cellular response.

Results: CDDP and DACH-Ac-Pt were equiactive against mutant p53 and androgen-independent DU-145 or PC-3 tumor cells. In wild-type p53 cells, CDDP was threefold more potent against androgen-dependent LNCaP than isogenic androgen-independent LNCaP-LN3 cells. However, the analog was equipotent in these two wild-type p53 tumor models. The greater potency of DACH-Ac-Pt than CDDP in wild-type p53 cells was not due to increased cellular drug uptake or increased adduct levels, but correlated with a lower tolerance to DNA damage. The analog also activated the p53-p21(WAF1/CIP1) signal transduction pathway more efficiently in LNCaP and LNCaP-LN3 cells, and this induced G(1)-phase cell-cycle arrest. CDDP, in contrast, activated this pathway efficiently in LNCaP cells only. In addition, and compared to CDDP, DACH-Ac-Pt was more effective in inducing Bax and increasing the Bax/Bcl-2 ratios in both the tumor models.

Conclusions: DACH-Ac-Pt is highly effective against wild-type p53 LNCaP and its LN3 variant, and this activity is androgen-independent. The differential induction of p21(WAF1/CIP1) and increase in Bax/Bcl-2 ratios with CDDP and DACH-Ac-Pt in LNCaP-LN3 cells appear to be linked to the relative activity of the two agents against this model.

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http://dx.doi.org/10.1002/pros.20114DOI Listing

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