Sphingosine kinase-2 silencing modulates sensitivity of HT-29 human colorectal cancer cells to paclitaxel-induced cell death through altering apoptosis-related proteins

The sphingosine kinase-2 (SphK2), a main component of sphingolipid signal transduction, is reported as an innovative therapeutic candidate for cancer treatment. This study was conducted to investigate the suppression of SphK2 in increasing HT-29 colorectal cancer cells sensitivity to paclitaxel via inducing apoptosis and targeting c-FLIPS, MCL-1, and survivin expressions. Cells were transfected with siRNA against SphK2, PTX, or SphK2 activator. Proliferation and apoptosis were evaluated by MTT assay, and trypan blue staining and ELISA, respectively. SphK2, c-FLIPS, MCL-1, and survivin expression were determined by qRT-PCR and Western blotting. SphK2 siRNA increased cell death induced PTX. SphK2 agonist abolished silencing impact on cell survival. We found down-expression of C-FLIPS, MCL-1, and survivin by SphK2 siRNA transfection either alone or in paclitaxel treated cells, as well as elevation in cell apoptosis. Our results showed that SphK2 suppression may be an effective important modality to enhance cell sensitivity to paclitaxel via the induction of apoptosis in colorectal cancers.