Relationship between epigenetic changes in Wnt antagonists and acute leukemia.

Abstract

The present study was designed to investigate the relationship among epigenetic changes in Wnt antagonists, histone H4K20me1 and the expression of tumor-suppressor genes in acute leukemia (AL) to better understand the pathogenesis of leukemia. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to detect messenger RNA (mRNA) expression levels of Wnt antagonists (Wnt5a, HDPR1, DKK1 and DKK3) in patients with AL and in normal controls; pyrophosphate sequencing was performed to detect the methylation status of the Wnt5a promoter; and western blotting was performed to detect the overall expression levels of Wnt5a protein and histone H4K20me1 in patients with acute myeloid leukemia (AML) and in normal controls. The relationship between Wnt5a protein expression and histone H4K20me1 was analyzed. Chromatin immunoprecipitation-qPCR (ChIP-qPCR) was performed to investigate the recruitment of H4K20me1 and SET8 to the Wnt5a promoter and coding regions. Our results demonstrated that the expression levels of Wnt antagonists were generally low in AML, but showed differential expression in acute lymphocytic leukemia (ALL). In most cases of AML, methylation of the Wnt5a promoter was observed and Wnt5a protein expression was low. In some cases of AML, the overall level of H4K20me1 protein was higher than that in normal controls. In addition, Wnt5a expression was positively correlated with H4K20me1 expression and was unrelated to the methylation status of its promoter. Moreover, H4K20me1 and SET8 were enriched in the Wnt5a promoter region and coding region. By contrast, Wnt5a expression was unrelated to H4K20me1 expression in normal controls. Moreover, we observed that the methylation of Wnt antagonists was often found in patients with AL, particularly those with AML, whereas the extent of methylation was variable in ALL patients. Wnt5a expression was positively correlated with the enrichment of H4K20me1 and SET8 at the Wnt5a promoter and coding regions. H4K20me1 increased Wnt5a expression by promoting transcription initiation and elongation.