Abstract
Overexpression and/or overactivation of sphingosine kinase 1/2 (SphK1/2) is important for tumorigenesis and progression of cervical cancer. The current study examined the potential activity and signaling mechanisms of SKI-V, a non-lipid small molecule SphK inhibitor, against cervical cancer cells. In different primary and immortalized cervical cancer cells, SKI-V exerted significant anti-cancer activity by inhibiting cell viability, colony formation, proliferation, cell cycle progression and cell migration. Significant apoptosis activation was detected in SKI-V-treated cervical cancer cells. Significantly, SKI-V also provoked programmed necrosis cascade in cervical cancer cells, as it induced mitochondrial p53-cyclophilin-D-adenine nucleotide translocator-1 (ANT1) complexation, mitochondrial membrane potential collapse, reactive oxygen species production and the release of lactate dehydrogenase into the medium. Further, SKI-V blocked SphK activation and induced ceramide accumulation in primary cervical cancer cells, without affecting SphK1/2 expression. SKI-V-induced cytotoxicity in cervical cancer cells was largely inhibited by sphingosine-1-phosphate or the SphK1 activator K6PC-5, but was sensitized by adding the short-chain ceramide C6. Moreover, SKI-V inhibited Akt-mTOR (mammalian target of rapamycin) activation in primary cervical cancer cells, and its cytotoxicity was mitigated by a constitutively-active Akt. In vivo, daily intraperitoneal injection of SKI-V significantly inhibited subcutaneous primary cervical cancer xenograft growth in nude mice. Together, the SphK inhibitor SKI-V suppresses cervical cancer growth in vitro and in vivo.