The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 19 No. 7 • December 2016


SELENITE REACTIVATES PTEN,
A TUMOR SUPPRESSOR PROTEIN

RESTORES SILENCED GENE BY MODIFYING DNA METHYLATION

An important new trick performed by sodium selenite is reported in two fairly recent papers. It adds to the data we’ve already written about showing that sodium selenite is a powerful protectant against cancer.

Here, the papers describe how sodium selenite is able to reactivate a major tumor suppressor gene that has been silenced by methylation of DNA, preventing it from carrying out its important anticancer function. The silencing of tumor suppressor genes and, indeed, many other genes, are “turned off” during aging. Scientists have learned recently how some of this works and how to restore silenced genes.

The silencing of PTEN is an important mechanism in many forms of cancer, such as prostate cancer (Berggren, 2009). In one study (Berggren, 2009), the authors showed that selenite increased the activity of a kinase, casein kinase-2 (CK2), involved in PTEN phosphorylation and the regulation of the tumor suppressor’s activity in these cells. DU-145 prostate cancer cells were reported to express PTEN and had decreased activity of the kinase CK2. The researchers found that sodium selenite upregulated CK2 activity, thus increasing the stability and activity of PTEN. “...the novel finding that Se [selenite] increases CK2 activity, which in turn can affect PTEN activity, is of interest for the treatment of prostate cancer.” (Berggren, 2009)

A second paper (Xiang, 2008) provides data on how selenite reactivates silenced genes by modifying DNA methylation and histones in prostate cancer cells. Hypermethylation of DNA prevents genes from being expressed, which silences them. Methylation or demethylation is an important way that genes are turned off or turned on, the epigenetic process. It is a way that DNA can be made to function in a different way without having to alter the DNA code (create a mutation).

“Cancer is a disease associated with both genetic and epigenetic changes. Epigenetic gene regulation has been recognized to play a role in the etiology of cancer.” This paper describes how selenium “may have epigenetic effects on gene expression involved in prostate carcinogenesis.” (Xiang, 2008) Here, the authors explain how selenium “can restore the expression of the hypermethylation-silenced genes ... in human prostate cancer cells ...”

References

  • Berggren et al. Sodium selenite increases the activity of the tumor suppressor protein, PTEN, in DU-145 prostate cancer cells. Nutr Cancer. 61(3):322-31 (2009).
  • Xiang et al. Selenite reactivates silenced genes by modifying DNA methylation and histones in prostate cancer cells. Carcinogenesis. 29(11):2175-81 (2008).

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