A research of regulation of glycosphingolipids gene expression and anticancer drug sensitivity in human oral cancer cell lines

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To clarify the relation between the amount of ganglioside GM3 on the surface of the cell membrane and the anti-cancer drug sensitivity, this research was done with 14 human oral squamous cell carcinoma cell lines which were obtained from JCRB (Ca9-22,HSC-2,HSC-3,HSC-4,Ho-1-N-1,Ho-1-U-1,KON, KOSC2-c13,SAT, SAS, SCC-4,SKN-3,OSC-19,OSC-20). The ganglioside contents were detected by thin layer chromatography for the cell lines. The expression of GM3 synthesis enzyme (SAT-1) gene of each cell line was measured by the Real time PCR. A quantitative difference was seen by the cell lines as for the amount of GM3 and the SAT-1 expression. The 50% effective doses (Ic50) of cisplatin were calculated from the dose-response curves which were derived from MTT assay. The Ic50 of the cisplatin showed positive correlation with SAT-1 expression (R=0.717) in 14 cell lines. Next, the cisplatin sensitivity was examined after controlling the expression of GM3 in the cell line Ca9-22. The Ca9-22 cell line was selected to transfect SAT-1 gene, because it has rich LacCer which is the precursor of GM3 and little amount of GM3. However, the SAT-1 transfected clone did not increase GM3 than a wild type, but GM2 which was made of GM3 had increased. The difference of the cisplatin sensitivity was not seen between the SAT-1 gene transfected clone and a wild type. Inhibitors of glucosylceramide synthase, such as D-PDMP, PBPP and P4 were used to detect the role of ganglioside on Ca9-22, 0SC-20 and SCC-4 cell lines, which showed no definite effect on sensitivity of cisplatin and etoposide. It was suspected that GM3 alone do not have a relation with the cisplatin sensitivity, and more factors may take part in. Further investigation should be done to detect the mechanism of ganglioside on the cell signaling which induce apoptosis by anti-cancer drug.