Methylation of CpG island in promoter region of RUNX2 gene and its expression in HOX11(+) acute T lymphoblastic leukemia

Abstract

This study was purposed to detect the methylation status in promoter region of RUNX2 gene and its expression in cell lines and patients with HOX11(+) T-cell acute lymphoblastic leukemia (T-ALL) and to explore the relationship between the expression level of RUNX2 gene and methylation of CpG island in its promoter region. The methylation pattem in promoter region of RUNX2 gene was detected with bisulfite sequencing PCR, DNA methylation immunoprecipitation technique and promoter oligonucleotide microarray analysis and the expression levels of RUNX2 mRNA was detected with RT-PCR in 3 T-ALL cell lines (sil-ALL, DND41 and RPMI), as well as in 75 clinic bone marrow samples including 38 de novo T-ALL patients, 29 complete remission T-ALL patients and 8 normal samples. The results showed that there were hypermethylation of CpG island in promoter region of RUNX2 gene in patients with highly expressing HOX11(+) T-ALL. The methylation rate of the promoter CpG islands of RUNX2 gene in HOX11(+) T-ALL (78.9%) was significantly higher than that in HOX11(-) T-ALL (36.8%) (P < 0.01). The expression of RUNX2 in HOX11(+) cell lines was significantly lower than that in HOX11(-) cell lines, and the expression level of RUNX2 in the HOX11(+) T-ALL patients (0.581 ± 0.257) was significantly lower than that in HOX11(-) T-ALL patients (0.835 ± 0.317). The relationship between RUNX2 and HOX11 mRNA expression level showed a negative correlation (rs = -0.378, P < 0.01). The expression levels of RUNX2 gene negatively correlated with the methylation of CpG island in its promoter region (rs = -0.419, P < 0.01). It is concluded that HOX11 is a negative regulator of RUNX2 gene and the expression of RUNX2 is down regulated or even lost by promoter methylation in T-ALL, which demonstrate a better event-free survival and a marked trend for longer overall survival for HOX11-high T-ALLs. The expression and methylation level of RUNX2 gene may have some significance in evaluating the curative effect of T-ALL. The abnormal expression of RUNX2 may be a prognostic marker in T-ALL patients.