α-Tocopheryl succinate (α-TOS), a mitochondria-targeting agent, induces apoptosis in malignant cells in vitro and in vivo. Selenite is a nutritional supplement that has been shown to stimulate apoptosis in cancer cells. This study was designed to investigate the cytotoxic effect of combined treatment of α-TOS and sodium selenite (SSe) in vitro and in vivo and to explore their effect on apoptosis and autophagy in breast cancer. The type of interaction between α-TOS and SSe was evaluated and levels of oxidative stress and apoptotic and autophagic markers were determined. SSe alone showed varying degrees of cytotoxicity on all the tested cell lines. Its combination with α-TOS was antagonistic in vitro in MCF7 and in vivo in mice bearing Ehrlich tumor compared to α-TOS-treated one. Combination of TOS with 2 μM of SSe increased the level of glutathione without changes in antiapoptotic markers Bcl-2 and Mcl-1 at 16 and 48 hrs. SSe decreased caspase 3 activity and protein level of caspases 7 and 9, while it increased autophagic markers beclin-1 and LC3B protein levels of MCF7 cells treated with α-TOS. In conclusion, SSe antagonizes α-TOS-induced apoptosis via inhibition of oxidative stress and promoting prosurvival machinery of autophagy.

No abstract

Aims: This study investigated the impact of promoter methylation of flouropyrimidine (FP) metabolizing and cyclooxygenase 2 (COX2) genes on their mRNA expression and on the clinical outcome of colorectal cancer (CRC) patients. Methods: Methylation specific-PCR and real time-PCR of thymidylate synthase (TS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD) and COX2 were performed at baseline and after 3 and 6 months of FP therapy. Pairwise comparisons were conducted between the subgroups of CRC patients. The event free survival (EFS) and the hazard of progression were estimated by univariate and multivariate analyses. Results: At baseline CRC patients, both TS and TP were overexpressed, in spite of the unmethylation of TS and the full methylation of TP genes. Significant downexpression of DPD and COX2 were associated their promoter’s methylation. At the end of FP therapy, TS, DPD and COX2 were overexpressed by 7.52, 2.88 and 3.45 folds, respectively, while TP was downexpressed by 0.54 fold. However, no change was observed in the methylation status of genes with FP therapy. Pairwise comparisons revealed significant difference in the expression and the methylation status of genes according to the clinicopathological characters of CRC patients either at baseline or after FP therapy. The overexpression of DPD and COX2 genes were indicators for a poor EFS of CRC patients. Also, the high level of COX2 expression was found to be significantly correlated with the hazard of progression (HR = 1.73, 95% CI = 1.02-3.03). Conclusion: The promoter methylation of FP metabolizing and COX2 genes has significant impact on the expression and the treatment outcome of CRC patients.