Inhibition of sphingosine kinase-2 ablates androgen resistant prostate cancer proliferation and survival

Abstract

Background: Endogenous sphingolipid signaling has been shown to play an important role in prostate cancer endocrine resistance.

Methods: The novel SphK2 inhibitor, ABC294640, was used to explore SphK signaling in androgen resistant prostate cancer cell death signaling.

Results: It dose-dependently decreased PC-3 and LNCaP cell viability, IC(50) of 28 ± 6.1 μM (p < 0.05) and 25 ± 4.0 μM (p < 0.05), respectively. ABC294640 was more potent in long-term clonogenic survival assays; IC(50) of 14 ± 0.4 μM (p < 0.05) in PC-3 cells and 12 ± 0.9 μM (p < 0.05) in LNCaP cells. Intrinsic apoptotic assays failed to demonstrate increased caspase-9 activity. Ki-67 staining demonstrated decreased proliferation by 50 ± 8.4% (p < 0.01) in PC-3 cells.

Conclusions: SphK2 inhibition decreases androgen resistant prostate cancer viability, survival, and proliferation independently of the intrinsic apoptotic pathway. Findings are in contrast to recent observations of ABC29460 acting dependently on the intrinsic pathway in other endocrine resistant cancer cell lines.

Keywords: Chemoresistance; Prostate cancer; Sphingolipids; Sphingosine kinase; Sphingosine kinase 2.