Vitamin E succinate induces ceramide-mediated apoptosis in head and neck squamous cell carcinoma in vitro and in vivo

Purpose: Vitamin E succinate (α-TOS) inhibits the growth of cancer cells without unacceptable side effects. Therefore, the mechanisms associated with the anticancer action of α-TOS, including ceramide-mediated apoptosis, were investigated using head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. Experimental Design: Five different human HNSCC cell lines (JHU-011, JHU-013, JHU-019, JHU-022, and JHU-029) were treated with α-TOS, and its effects on cell proliferation, cell cycle progression, ceramide-mediated apoptosis, and ceramide metabolism were evaluated. The anticancer effect of α-TOS was also examined on JHU-022 solid tumor xenograft growth in immunodeficient mice. Results: α-TOS inhibited the growth of all the HNSCC cell lines in vitro in a dose- and time-dependent manner. Thus, JHU-013 and JHU-022 cell lines were more sensitive to α-TOS than the other cell lines. Cellular levels of ceramide, sphingomyelinase activity, caspase-3, and p53 were elevated with increasing time of exposure to α-TOS. The degradation of poly(ADP-ribose) polymerase protein in JHU-022 cells treated with α-TOS provided evidence for apoptosis. The amounts of nuclear factor κB, Bcl-2, and Bcl-X_L proteins were reduced in the cells treated with α-TOS for 6 hours. The levels of caspase-9, murine double minute-2, and IκB-α proteins were unchanged after α-TOS treatment. I.p. administration of α-TOS slowed tumor growth in immunodeficient mice. Conclusions: α-TOS showed promising anticancer effects to inhibit HNSCC growth and viability in vivo and in vitro. The induction of enzymes involved in ceramide metabolism by α-TOS suggests that ceramide-mediated apoptosis may expand therapeutic strategies in the treatment of carcinoma.