The purpose of this study was to determine whether the therapeutic efficacy of fenretinide (4‐HPR), a ceramide‐generating anticancer agent, could be enhanced in prostate cancer cells by inclusion of a novel synthetic acid ceramidase (AC) inhibitor, DM102, a pivaloylamide of a 2‐substituted aminoethanol. In prostate cancer, AC plays a role in progression and resistance to chemotherapy.

PC‐3 and DU 145 hormone‐refractory human prostate cancer cell lines were used. Cells were exposed to 4‐HPR, DM102, and combinations; viability, apoptosis, cell migration, ceramide metabolism, and levels of reactive oxygen species (ROS) were assessed.

Single agent 4‐HPR and DM102 (2.5–10 µM) were weakly cytotoxic; however, combinations synergistically decreased cell viably to as low as 1.5% of control. N‐oleoylethanolamine (NOE), a frequently employed AC inhibitor, was not effective in producing synergy. The 4‐HPR/DM102 regimen enhanced caspase activity and increased [³H](dihydro)ceramide and ROS levels 6‐ and 30‐fold over control, respectively. The antioxidant vitamin E, but not the de novo ceramide synthesis inhibitor myriocin, partially rescued cells from 4‐HPR/DM102 cytotoxicity. The 4‐HPR/DM102 combination also elicited synergistic cytotoxicity in DU 145 cells, another human hormone‐refractory prostate cancer cell line.

This study shows that 4‐HPR cytotoxicity is enhanced in a synergistic fashion by inclusion of the AC inhibitor DM102, by a mechanism that enlists generation of ROS, and thus provides a system to raise 4‐HPR therapeutic potential. The role of ceramide however in the cytotoxic response is not clear, as blocking ceramide generation failed to rescue PC‐3 cells from 4‐HPR/DM102 cytotoxicity. Prostate 71:1064–1073, 2011. © 2010 Wiley‐Liss, Inc.