Induction of apoptosis in human renal cell carcinoma cells by vitamin E succinate in caspase-independent manner.
OBJECTIVE
Renal cell carcinoma (RCC) is one of the most drug-resistant malignancies, and an effective therapy is lacking for metastatic RCC. Vitamin E (VE) has been intensively studied as a chemopreventive agent for various cancer types. Preclinical investigations have suggested that VE succinate (VES) is the most effective analog of VE in cancer cells; however, no study of VES in RCC has been done. We investigated the anticancer activity of VES against RCC.


METHODS
Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell morphologic changes and cell viability were evaluated using phase-contrast microscopy and the trypan blue dye-exclusion test, respectively. Caspase activity was measured with a quantitative colorimetric assay.


RESULTS
VES exerted dose- and time-dependent cytotoxicities against ACHN, a human RCC cell line, but VE and VE acetate did not. The cytotoxic effect was also observed in 2 other RCC cell lines, Caki-1 and Caki-2, and in primary RCC cells derived from 8 patients. Hoechst 33258 staining and DNA ladder analysis demonstrated that VES induced apoptosis in RCC cells. However, VES did not affect activation of caspase-3, -6, -8, or -9. Furthermore, inhibitors specific to caspase-8, -9, -6, and -3 did not block VES cytotoxicity and neither did the general caspase inhibitor VAD.


CONCLUSIONS
VES might induce apoptosis and cytotoxicity against RCC cells in a caspase-independent manner and has potential in vivo applications in the treatment of drug-and/or immunotherapy-resistant RCC.
Wu
Xiu-Xian
XX
Department of Urology, Kagawa University Faculty of Medicine, Kagawa, Japan.
Kakehi
Yoshiyuki
Y
Jin
Xing-Hua
XH
Inui
Masashi
M
Sugimoto
Mikio
M
D017209:Apoptosis / Q000187:drug effects*; D002292:Carcinoma, Renal Cell / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D020169:Caspases / Q000502:physiology; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007680:Kidney Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D024505:Tocopherols / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured; D014815:Vitamins / Q000627:therapeutic use*
D014815:Vitamins; D020169:Caspases; D024505:Tocopherols