Objective: To detect the methylation pattern of the p15(INK4B) gene and to explore its significance in the pathogenesis of acute leukemia (AL) and leukemic transformation of myelodysplastic syndromes (MDS).
Methods: A total of 49 AL cases and 22 MDS cases were analyzed by methylation specific polymerase chain reaction (MSP) for methylation patterns in CpG islands of the p15(INK4B) gene.
Results: Hypermethylation of the p15(INK4B) gene was found in 90% (26/29) of newly diagnosed AL, including 46% with complete methylation and 54% with partial methylation. All 3 evolved AL from MDS and 9 relapsed AL showed a methylated p15(INK4B) gene and the proportion of complete methylation was 67% and 56% respectively. Only 5 of 11 (45%) AL in remission, including 2 in complete remission (CR) and 3 in partial remission (PR), were partially methylated. The frequency of p15(INK4B) gene methylation in newly diagnosed or relapsed AL was significantly higher than that in AL in the remission stage (P = 0.002) p15(INK4B) gene methylation was found in 5 of 13 (38%) low-risk MDS (RA/RAS) patients and 80% of them showed only partial methylation. However, p15(INK4B) gene methylation was found in all 9 cases in the high-risk group (RAEB/RAEB-T), including complete methylation in 56%, significantly different from the low-risk MDS group (P = 0.002).
Conclusions: Hypermethylation of the p15(INK4B) gene occurs frequently in leukemia and high-risk MDS. It is possible that hypermethylation of this gene is related to the pathogenesis and development of AL and MDS. It may be used as a gene marker to detect minimal residual disease, relapse of AL and leukemic transformation in MDS.