Hypomethylation of PRAME is responsible for its aberrant overexpression in human malignancies

Abstract

The preferentially expressed antigen of melanoma (PRAME) is expressed at high levels in large fractions of human malignancies, e.g., acute myeloid leukemia. Therefore, PRAME is an important marker for diagnosis of various malignant diseases and a relevant parameter for monitoring minimal residual disease. It is supposed to be involved in tumorigenic processes. Because of these important aspects we investigated its transcriptional regulation in detail. Most relevant was a detailed DNA methylation analysis of the PRAME 5' region by genomic sequencing in correlation with PRAME expression in various human patient samples and cell lines. In combination with DNA-truncation/transfection experiments with respect to DNA methylation, we show that changes in the methylation pattern in defined parts of the regulatory regions of PRAME are sufficient for its upregulation in cells usually not expressing the gene.

Methylation pattern of preferentially expressed antigen of melanoma in acute myeloid leukemia and myelodysplastic syndromes

“…In the present study, using the bisulfate sequencing method, it was demonstrated that PRAME expression was associated with the methylation status of specific CpG sites, and that the degree of hypomethylation was generally inversely associated with its transcript levels in AML and MDS. Numerous studies have demonstrated that the hypomethylation of PRAME is correlated with its overexpression (17)(18)(19)(20); however, the results are inconsistent, and certain issues still require clarification. Bisulfate sequencing is a direct and comprehensive but complex method used for methylation studies.…”

“…Bisulfate sequencing is a direct and comprehensive but complex method used for methylation studies. Therefore, previous studies that analyzed PRAME methylation in leukemia performed clone sequencing in 5 cell lines, 2 normal controls and 22 patient samples, but did not include the entire CpG island regions (17)(18)(19)(20). Along with the individual variances between patients, the exact assessment of the methylation effect may be difficult to determine and may produce biased results.…”

“…Subsequent studies confirmed this result in AML and chronic myeloid leukemia (CML) (17)(18)(19)(20)(21)(22). However, despite numerous studies demonstrating an inverse correlation between methylation of specific 5'-C-phosphate-G-3' (CpG) sites and PRAME expression, the CpG island regions studied were different (17)(18)(19)(20). Furthermore, to the best of our knowledge, no studies have analyzed all the CpG sites of the PRAME gene.…”

“…As a result of its complexity, the sample number is typically small (17)(18)(19)(20). Therefore, although a general correlation between the hypomethylation of specific CpG sites of PRAME and its overexpression was revealed (17)(18)(19)(20), whether the degree of hypomethylation is associated with the degree of increase in its expression remains unknown. Furthermore, the association between hypomethylation of CpG sites and PRAME overexpression has not been specifically investigated in AML1-ETO + AML and MDS.…”

PRAME expression in hairy cell leukemia

“…As a nuclear protein, it binds to retinoic acid receptor a, thereby inhibiting retinoic acid induced differentiation, growth arrest, and apoptosis (27,28). Overexpression of PRAME is associated with hypomethylation in its regulatory regions (29), and in pediatric acute leukemias confers a favorable prognosis, possibly by inhibiting tumorigenicity and enhancing apoptosis (28).…”