2-2-bis(hydroxymethyl)-1-azabicyclo(2-2-2-)octan-3-one and Thyroid-Neoplasms

3-Deazaneplanocin A (DZNep) depletes enhancer of zeste homolog 2 (EZH2), a core component of polycomb repressive complex 2 (PRC2), which is frequently overexpressed in human cancers. DZNep exhibits promising antitumor activity, and its responsiveness in cancer cells is determined by certain genetic factors.. Our aims were (1) to test the therapeutic potential of DZNep and explore the genetic determinants affecting the DZNep response in thyroid cancer cells and (2) to test the combined therapeutic effect of DZNep and PRIMA-1, a mutant p53 reactivator, in thyroid cancer.. We evaluated the phenotypic effects of DZNep in thyroid cancer cells and examined the effects of DZNep alone or in combination with PRIMA-1 on cell proliferation, the cell cycle, apoptosis, and xenograft tumor growth.. DZNep induced enhancer of zeste homolog 2 depletion and trimethylated lysine 27 in H3 histone (H3K27me3) mark reduction in all thyroid cancer cells; however, only TP53 wild-type cells exhibited growth inhibition with DZNep treatment. In these cells, DZNep caused p53 protein accumulation through up-regulation of USP10 expression, resulting in activation of the p53 pathway, contributing to inhibition of cell growth. Conversely, TP53 mutant-type cells were resistant to DZNep. Strikingly, the combination of DZNep with PRIMA-1 restored the sensitivity of TP53 mutant-type cells to DZNep. A similar antitumor effect of DZNep and PRIMA-1 alone or in combination was also seen in xenograft tumor models.. Our data demonstrated that DZNep responsiveness was strongly associated with TP53 genomic status in thyroid cancer cells. Reactivation of p53 restored the sensitivity of TP53 mutant-type cells to DZNep. Thus, a combined therapeutic strategy may be effective in treating thyroid cancer cells (or patients) harboring mutant p53.

Topics: Adenosine; Animals; Apoptosis; Aza Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cell Cycle; Cell Line, Tumor; Drug Resistance, Neoplasm; Drug Synergism; Humans; Mice; Mice, Nude; Mutant Proteins; Thyroid Neoplasms; Tumor Suppressor Protein p53; Xenograft Model Antitumor Assays

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