Futscher, B., Oshiro, M. M., Watts, G. S., Wozniak, R. J., Junk, D. J., Munoz-Rodriguez, J. L., Domann, F. E., & Futscher, B. W. (2003). Mutant p53 and aberrant cytosine methylation cooperate to silence gene expression. Oncogene, 22(23).
p53 is an important transcriptional regulator that is frequently mutated in cancer. Gene-profiling experiments of breast cancer cells infected with wt p53 revealed both MASPIN and desmocollin 3 (DSC3) to be p53-target genes, even though both genes are silenced in association with aberrant cytosine methylation of their promoters. Despite the transcriptional repression of these genes by aberrant DNA methylation, restoration of p53 resulted in the partial reactivation of both genes. This reactivation is a result of wt p53 binding to its consensus DNA-binding sites within the MASPIN and DSC3 promoters, stimulating histone acetylation, and enhancing chromatin accessibility of their promoters. Interestingly, wt p53 alone did not affect the methylation status of either promoter, suggesting that p53 itself can partially overcome the repressive barrier of DNA methylation. Pharmacologic inhibition of DNA methylation with 5-aza-2'-deoxycytidine in combination with restoration of wt p53 status resulted in a synergistic reactivation of these genes to near-normal levels. These results suggest that cancer treatments that target both genetic and epigenetic facets of gene regulation may be a useful strategy towards the therapeutic transcriptional reprogramming of cancer cells.
Wang, H., Jiang, Z., Wong, Y. W., Dalton, W. S., Futscher, B. W., & Chan, V. T. (1997). Decreased CP-1 (NF-Y) activity results in transcriptional down-regulation of topoisomerase IIα in a doxorubicin-resistant variant of human multiple myeloma RPMI 8226. Biochemical and Biophysical Research Communications, 237(2), 217-224.
PMID: 9268689;Abstract:
Decreased topoisomerase II (Topo II) activity results in resistance to antineoplastic agents targeting this enzyme. Dox1V derived from human multiple myeloma RPMI 8226 demonstrated a 4-fold resistance to doxorubicin in the absence of MDR1 overexpression or topo II mutations. Consistent with its drug resistant phenotype, a 2- to 3-fold decrease in topo II expression was identified. To investigate the molecular basis for decreased topo II expression in Dox1V, a semi-quantitative analysis of Topo II activity, protein level and mRNA transcript were performed. The results demonstrated that reduced Topo II activity is due to a decreased mRNA level. Southern blot and sequencing experiments revealed wild-type sequence of the topo II promoter in the drug resistant cells. Transient gene expression assays demonstrated that topo II is transcriptionally down-regulated in Dox1V independent of the promoter sequence of the endogenous alleles. Instead, the activity of a ubiquitous transcription factor CP-1 (NF-Y) interacting with the topo II promoter is decreased. The decrease in CP-1/NF-Y activity in Dox1V is correlated well with the decrease in topo II transcriptional activity, transcript level, Topo II protein and enzyme activity. Therefore, transcriptional down-regulation resulted from a reduced CP-1/NF-Y activity is responsible for decreased topo II expression in Dox1V cells.
Futscher, B., Vrba, L., Jensen, T. J., Garbe, J. C., Heimark, R. L., Cress, A. E., Dickinson, S., Stampfer, M. R., & Futscher, B. W. (2010). Role for DNA methylation in the regulation of miR-200c and miR-141 expression in normal and cancer cells. PloS one, 5(1).
The microRNA-200 family participates in the maintenance of an epithelial phenotype and loss of its expression can result in epithelial to mesenchymal transition (EMT). Furthermore, the loss of expression of miR-200 family members is linked to an aggressive cancer phenotype. Regulation of the miR-200 family expression in normal and cancer cells is not fully understood.
Fitzgerald, M., Oshiro, M., Holtan, N., Krager, K., Cullen, J. J., Futscher, B. W., & Domann, F. E. (2003). Human Pancreatic Carcinoma Cells Activate Maspin Expression Through Loss of Epigenetic Control. Neoplasia, 5(5), 427-436.
PMID: 14670180;PMCID: PMC1502613;Abstract:
The maspin gene is not expressed in normal human pancreas, but its expression is acquired during human pancreatic carcinogenesis. In other normal human cells and their malignant counterparts, maspin expression is controlled through the epigenetic state of its promoter. In studies presented herein, we used bisulfite genomic sequencing and chromatin immunoprecipitation studies to show that maspin-negative pancreas cells have a methylated maspin promoter, and that the associated H3 and H4 histones are hypoacetylated. In contrast to normal pancreas, four of six human pancreatic carcinoma cell lines investigated displayed activation of maspin expression. This activation of maspin expression in pancreatic carcinoma cells was linked to demethylated promoters and hyperacetylation of the associated H3 and H4 histones. In addition, 5-aza-2′-deoxycytidine treatments activated maspin expression in the two maspin-negative pancreatic carcinoma cell lines, suggesting a causal role for cytosine methylation in the maintenance of a transcriptionally silent maspin gene. Thus, human pancreatic carcinoma cells acquire maspin expression through epigenetic derepression of the maspin locus, and in so doing appear to co-opt a normal cellular mechanism for the regulation of this gene.
Pieper, R. O., Costello, J. F., Kroes, R. A., Futscher, B. W., Marathi, U., & Erickson, L. C. (1991). Direct correlation between methylation status and expression of the human O-6-methylguanine DNA methyltransferase gene. Cancer Communications, 3(8), 241-253.
