Induction of apoptosis in prostate cancer cells by the novel ceramidase inhibitor ceranib-2.

Abstract

Ceramidases are key enzymes that decrease ceramide levels in cells. A reduction in ceramide concentration impairs ceramide signalling, and results in apoptosis resistance in cancer cells. This study investigates the potential for ceranib-2, a novel ceramidase inhibitor, to affect the survival and/or promote apoptosis of prostate cancer cells (LNCaP and DU145) in vitro. Cell viability was determined using MTT, and apoptosis assessed via flow cytometry. We examined structural changes with both confocal and transmission electron microscopes. Ceranib-2 concentrations of 0.1, 1, 5, 10, 25 and 50μM were applied to LNCaP and DU145 cell lines. The corresponding reduction in LNCaP cell viability (against the control) was 84%, 80%, 64%, 56%, 40% and 15% after 24h, and 81%, 74%, 60%, 55%, 27% and 11% after 48h. For DU145 cells, viability was reduced to 84%, 82%, 63%, 50%, 41% and 18% after 24h, and 64%, 42%, 30%, 20%, 8% and 5% after 48h. Following treatment with 25 and 50μM ceranib-2, the respective observed rates of early apoptosis in LNCaP cells were 23% and 36% after 24h and 27% and 58% after 48h. The morphological and ultrastructural signs of apoptosis detected were fragmented nuclei, chromatin condensations and cytoskeleton laceration. The inhibitory effects of ceranib-2 on prostate cancer cell survival are dose and time dependent. For LNCaP cells, ceranib-2 toxicity was predominately apoptotic in nature, while for DU145 cells, cell death may be related to non-apoptotic mechanisms.