Methylseleninic acid elevates REDD1 and inhibits prostate cancer cell growth despite AKT activation and mTOR dysregulation in hypoxia.
Bottom Line: Methylseleninic acid (MSeA) is a monomethylated selenium metabolite theoretically derived from subsequent β-lyase or transamination reactions of dietary Se-methylselenocysteine that has potent antitumor activity by inhibiting cell proliferation of several cancers.We have now extended these studies to evaluate the impact of MSeA on REDD1 (an mTOR inhibitor) in inducing cell death of invasive prostate cancer cells in hypoxia.Our data suggest that MSeA induces REDD1 and inhibits prostate cancer cell growth in hypoxia despite activation of AKT and dysregulation of mTOR.
Affiliation: Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Penn State Hershey Cancer Institute, Hershey, Pennsylvania.Show MeSH
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Mentions: Although, PC3 cells have been used for xenograft model for testing MSeA by oral route for about 49 days 43, our intent was to investigate the efficacy of MSeA against a highly invasive prostate cancer cell line (PC-3M). Therefore, we decided an i.p. route of treatment for a shorter duration. The PC-3M-Luc cells were injected subcutaneously into left flanks of nude mice. Tumor volumes showed a steady growth in control while the MSeA-treated tumors exhibited reduced volumes (P < 0.05) at the end of the experiment (Fig. 5A). Similarly, number of Ki67-positive cells was decreased in the tumors following MSeA treatment (control: 123.5 ± 2.6; MSeA: 62.7 ± 18.4, P < 0.05). Furthermore, tumor burdens in control and MSeA-treated mice were reflected by change (P < 0.05) in total luminescence flux by day 20 post-treatment (Fig. 5B). The BLI of representative mice from control and MSeA-treated groups are shown in Figure 5C. Body weights did not change significantly between control and treated groups during the short-term treatment with MSeA (Fig. 5D). At the end of the experiment, tumor weights were 0.91 ± 0.54 g in control and 0.44 ± 0.23 g in MSeA-treated mice. Despite the apparent changes in the mean values, differences in overall tumor weights were not statistically significant due to large variation between groups. These findings differ slightly from Li et al. 43 who showed that inhibition of tumor growth occurred after oral MSeA treatment for longer duration in xenograft models using LNCaP, DU145, and PC3 cells.
Affiliation: Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Penn State Hershey Cancer Institute, Hershey, Pennsylvania.