Expression of p53 Enhances Selenite-Induced Superoxide Production and Apoptosis in Human Prostate Cancer Cells

Abstract

Although the anticancer effects of selenium have been shown in clinical, preclinical, and laboratory studies, the underlying mechanism(s) remains unclear. Our previous study showed that sodium selenite induced LNCaP human prostate cancer cell apoptosis in association with production of reactive oxygen species, alteration of cell redox state, and mitochondrial damage. In the present study, we showed that selenite-induced apoptosis was superoxide mediated and p53 dependent via mitochondrial pathways. In addition, we also showed that superoxide production by selenite was p53 dependent. Our study showed that wild-type p53-expressing LNCaP cells were more sensitive to selenite-induced apoptosis than p53-null PC3 cells. Selenite treatment resulted in high levels of superoxide production in LNCaP cells but only low levels in PC3 cells. LNCaP cells also showed sequential increases in levels of phosphorylated p53 (serine 15), total p53, Bax, and p21Waf1 proteins following selenite treatment. The effects of selenite were suppressed by pretreatment with a synthetic superoxide dismutase mimic or by knockdown of p53 via RNA interference. LNCaP cells treated with selenite also showed p53 translocation to mitochondria, cytochrome c release into the cytosol, and activation of caspase-9. On the other hand, restoration of wild-type p53 expression in PC3 cells increased cellular sensitivity to selenite and resulted in increased superoxide production, caspase-9 activation, and apoptosis following selenite treatment. These results suggest that selenite induces apoptosis by producing superoxide to activate p53 and to induce p53 mitochondrial translocation. Activation of p53 in turn synergistically enhances superoxide production and apoptosis induced by selenite. (Cancer Res 2006; 66(4): 2296-304)

Apoptosis induced by selenomethionine and methioninase is superoxide mediated and p53 dependent in human prostate cancer cells

“…5A, transfection of p53 siRNA suppressed SeMet-plus METase-induced elevation of superoxide, although p53 siRNA transfection alone also increased levels of superoxide compared with the control. The latter was most likely due to superoxide production from RNAiFect and siRNA transfection, which was observed in our previous study (8). Conversely, reexpression of wt p53 in PC3 cells significantly increased superoxide production following SeMet and METase treatment (Fig.…”

“…Flow Cytometric Analysis Cell samples were prepared and analyzed as described previously (8). After trypsinization, 1 Â 10 6 cells were washed with PBS/EDTA/bovine serum albumin buffer (PBS, 1 mmol/L EDTA, 0.1% bovine serum albumin) and fixed in 100 AL of PBS/EDTA/bovine serum albumin buffer plus 900 AL of 70% ethanol for 30 min at À20jC.…”

“…Both selenite and SeMet have anticancer activity, but SeMet is less effective than selenite, particularly in vitro (2,14). Our previous studies showed that selenite-induced apoptosis of human prostate cancer cells was superoxide mediated and p53 dependent via mitochondrial pathways (7,8). Several studies have shown that selenite-induced apoptosis was mediated by ROS production (14, 17 -19).…”

The subcellular distribution of MnSOD alters during sodium selenite-induced apoptosis

“…Previous studies have demonstrated that the superoxide production in mitochondria is a key event during selenite-induced apoptosis process (18)(19)(20)(21). However, the molecular mechanism of how sodium selenite triggers the accumulation of superoxide remains to be determined.…”

Molecular targets of selenium in prostate cancer prevention (Review)

“…This phenomenon leads to a decrease in the Bcl-2:Bax ratio, a release of cytochrome-c and the activation of mitochondrial apoptosis (107)(108)(109)(110)(111). Furthermore, two methylselenol precursors, mSeA and Semet, have also been found to decrease the ratio of these pro-apoptotic and anti-apoptotic protein expression levels.…”