2-2-bis(hydroxymethyl)-1-azabicyclo(2-2-2-)octan-3-one and 5-hydroxymethylcytosine

The p53 tumor suppressor pathway blocks carcinogenesis by triggering apoptosis and cellular senescence in response to oncogenic stress. Over 50% of human cancers including thyroid cancer carry loss-of-function mutations in the p53 gene. Recently, the identification of mutant p53-reactivating small molecules such as PRIMA-1 (p53 reactivation and induction of massive apoptosis) renders possibilities for the development of more efficient anticancer drugs. Although PRIMA-1 has been widely used for cancer therapy and exhibits a promising anticancer activity, its biological effect, particularly the epigenetic aspect, remains to be well elucidated. The present study attempts to explore the effect of PRIMA-1 on DNA methylation in a panel of thyroid cancer cell lines using luminometric methylation assay (LUMA). Our results showed that only p53 mutant-type cells were inhibited upon PRIMA-1 treatment. Conversely, p53 wild-type cells were non-sensitive to PRIMA-1. Moreover, our data demonstrated that PRIMA-1 selectively induced significant global DNA demethylation in p53 mutant-type cells. Mechanically, PRIMA-1 induced global DNA demethylation in these cells mainly through inhibiting the expression of DNA methyltransferase (DNMT) 1, 3a and 3b, and upregulating the expression of GADD45a. Notably, PRIMA-1 dramatically increased the expression of the ten-eleven translocation (TET) family of 5mC-hydroxylases, particularly TET1, in p53 mutant-type cells, further contributing to DNA demethylation. Thus, this study uncovered a previously unrecognized and prominent biological effect of PRIMA-1 through which it can cause global DNA demethylation in p53 mutant-type cancer cells mainly by rescuing the function of mutant p53 protein.

Topics: 5-Methylcytosine; Aza Compounds; bcl-2-Associated X Protein; Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p21; Cytosine; DNA (Cytosine-5-)-Methyltransferases; DNA Methylation; DNA-Binding Proteins; Down-Regulation; Gene Expression Regulation, Neoplastic; Humans; Mixed Function Oxygenases; Models, Biological; Mutation; Nuclear Proteins; Proto-Oncogene Proteins; Thyroid Neoplasms; Tumor Suppressor Protein p53; Up-Regulation