METHYLATION CHANGES IN CDKN2B AND CDKN2A GENES IN PATIENTS WITH MYELODYSPLASTIC SYNDROMES AND ACUTE MYELOID LEUKEMIA

Sborník

Background. Epigenetic de novomethylation of CpG islands is thought to be one of the key moments in malignant transformation of the cell. The most frequently tested genes are CDKN2B gene (cyclin-dependent kinase inhibitor gene) and its functional homologue CDKN2A gene. CDKN2A gene generates several transcript variants which differ in their first exons (isoform 1 and isoform 4). Aims. The methylation status of the CDKN2B and CDKN2A genes was studied in DNA samples isolated from bone marrow mononuclear cells (BM)-MNCs in Czech patients with myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) before treatment and during the course of the disease to evaluate its prognostic significance and association with clinical outcomes and disease progression. Methods. In our study methylation of these genes was studied in 63 patients with MDS, 2 with myelodysplastic/myeloproliferative neoplasms (MDS/MPN) and 13 with AML. Five patients were monitored during 5-azacytidine treatment. Twenty- six DNA samples from healthy donors (HD) were used as non-malignant controls. Methylation-specific multiplex ligation-dependent probe amplification (MSMLPA) method with all associated techniques was used for detection. MS-MLPA kit enables simultaneously detect copy number variations and methylation changes of genes located in CDKN2A-CDKN2B region at 9p21. Results. We found that abberant methylation was present in the CDKN2A gene in 38% and in the CDKN2B gene in 77% of the patients in MDS group. The level of methylation was higher in the group of AML patients - 77% in CDKN2A gene and 100% in CDKN2B gene. In MDS patients, an aberrant methylation was associated with a tendency to disease progression towards more advanced forms according to the World Health Organization (WHO) classification and the International Prognostic Scoring System (IPSS). Significant differences in methylation level were observed between early and advanced forms of MDS in CDKN2B gene (P value < 0. 05) but not for CDKN2A gene. The trend of methylation in patients treated with azacitidine was analyzed in CDKN2B gene and correlated with the course of the disease. Increased methylation was connected with disease progression. Summary. We concluded that the methylation level of CDKN2B gene might be used as a marker of leukemic transformation in MDS. Our study indicates the role of hypermethylation as an important event in the progression of MDS to AML.

Supported by the grant of MHCR 00023736.

Haematologica, 2012; 97(s1):  576