Sphingosine kinase-2 Inhibitor ABC294640 Enhances Doxorubicin-Induced Apoptosis of NSCLC Cells via Altering Survivin Expression.

Background: There is an urgent need to improve efficacy of chemotherapeutics to overcome resistance in cancer treatment. Sphingosine kinase-2 (SphK2) a key regulator of sphingolipid signaling has been rationalized as an important therapeutic target. We evaluated the role of SphK2 in doxorubicin (DOX)-induced apoptosis of NSCLC cells via altering c-FLIPS, MCL-1 and survivin expressions in order to overcome chemoresistance.

Methods: Proliferation and apoptosis were evaluated by MTT assay and DAPI staining, respectively. Cell population in each phase of cell cycle was determined by flow cytometric assay. Gene and protein expression levels were examined by quantitative RT-PCR and western blot analysis, respectively.

Results: Phorbol myristate acetate (PMA), a SphK2 stimulator, decreased cell death induced by IC of DOX (1.1 µM) to around 70% (p<0.01). Cell cycle analysis revealed a significant accumulation of the cells in S phase with a marked decrease in sub G1 phase when we incubated the cells with combined treatment of PMA and DOX (p<0.05). Adding ABC294640 (40 µM), a SphK2 inhibitor, significantly abolished PMA effect on cell survival (p<0.01). Survivin expression was significantly diminished by applying ABC294640 either alone or in DOX treated cells followed by increase in cell death (p<0.05), however, there was no significant change in MCL-1 expression by ABC294640 either alone or in DOX treated cells (p=0.16) and (p=0.06), respectively.

Conclusion: Identifying cancer patients with high SphK2 expression and then inhibiting of SphK2 activity can be considered as an important strategy to increase the efficacy of DOX in the induction of apoptosis.