RÉSUMÉ
In recent years the role of sphingosine kinase 2 (SphK2), a key enzyme in the sphingolipid pathway, in the process of tumorigenesis has gradually been elucidated. Recent research has shown that SphK2 inhibitors can be used as anticancer drugs alone or in combination with existing drugs to increase the therapeutic sensitivity of drug-resistant tumors. Among them, one selective SphK2 inhibitor, ABC294640, shows excellent oral bioavailability and biodistribution in vivo and has now entered Phase II clinical research. Therefore, developing innovative drugs based on SphK2 is of great interest. Herein, we discuss progress in understanding the role of SphK2 in tumorigenesis and review the recent development of inhibitors of SphK2.
RÉSUMÉ
Objective To explore the role of sphingosine kinase 2 (SphK2) in 5-fluorouradl (5-FU)-induced apoptosis in human colon cancer HCT116 cells. Methods Hoechst33342 staining was used to examine the apoptosis morphological changes of HCT116 cells 48 h after treatment with 5-FU; flow cytometry was used to detect the apoptotic ratio of HCT116 cells and the effects of SphK2 (down-regulation and over-expression) on 5-FU-induced apoptosis were analyzed. Western blotting analysis was used to examine the changes in the activated forms of SphK2 and apoptotic marker protein in HCT116 cells after exposure to 5-FU. Results 5-FU induced significant apoptosis in HCT116 cels as reflected by apoptosis characteristics-condensation and fragmentation of chromatin. Interference of SphK2 significantly increased 5-FU-induced apoptosis in HCT116 cells compared with non-interfered group (P < 0.01), accompanied by increased apoptotic marker protein. On the contrary, the apoptosis ratio of the cells with SphK2 over-expression was significantly decreased compared with vehicle plasmid-transfected group (P< 0.01), accompanied by decreased apoptotic marker protein. Moreover, 5-FU greatly increased activated SphK2. Conclusion SphK2 negatively regulates 5-FU-induced apoptosis in HCT116 cells.
RÉSUMÉ
<p><b>OBJECTIVE</b>To investigate the role of extracellular signal-regulated kinase (ERK) in apoptosis of human colon cancer (HCT116) cells.</p><p><b>METHODS</b>After the HCT116 cells were pretreated with specific ERK inhibitor (U0126) or specific siRNA and exposed to 10 mmol/L sodium butyrate (NaBT) for 24 h, their apoptosis was detected by flow cytometry, levels of SphK2 and ERK protein were measured by Western blot, and translocation of SphK2 was assayed by immunofluorescence microscopy.</p><p><b>RESULTS</b>The U0126 and siRNAs specific for SphK2 blocked the export of SphK2 from nuclei to cytoplasm and increased the apoptosis of HCT116 cells following NaBT exposure. Over-expression of PKD decreased NaBT-induced apoptosis of HCT116 cells, which was reversed by U0126. Furthermore, transfection of HCT116 cells with constitutively activated PKD plasmids recovered the U0126-blocked export of SphK2.</p><p><b>CONCLUSION</b>ERK regulates the export of SphK2 and apoptosis of HCT116 cells by modulating PKD. Modulation of these molecules may help increase the sensitivity of colon cancer cells to the physiologic anti-colon cancer agent, NaBT.</p>