|Budget Amount *help
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥2,900,000 (Direct Cost: ¥2,900,000)
To explore the role of tumor suppressor genes in the leukemic transformation of myelodysplastic syndromes (MDS), we investigated the immunohistochemical expression of p14, p16 and p18 gene products (proteins), inhibitors of cyclin-dependent kinases which regulate cell cycle at G_1/S boundary, in 29 MDS cases [Refractory anemia (RA) 16, RA with ringed sidereblast (RARS) 3, and RA with excess of blasts (RAEB) 10], acute myeloid leukemia (AML) 23 (MDS-derived AML 10 and de novo AML 13) and 6 normal control. We also examined the methylation status (epigenetic change) of p14, p15 and p16 promoter genes and elucidated their relationships to the leukemic transformation in MDS. The frequencies of positive reaction for p16 protein on hematopoietic cell in bone marrow were disclosed 1.87% (mean) in control, 2.63% in RA, 2.09% in RARS, 8.68% in RAEB, 18.03% in MDS-derived AML and 30.64% in de novo AML. The frequencies of positive reaction for p14 protein and p18 protein were as follows respectively: 0.2% and 0.86% in control, 0.21% and 0.83% in RA, 0.29% and 1.09% in RARS, 0.45% and 2.68% in RAEB, 0.82% and 29.86% in MDS-derived AML, and 0.72% and 50.02% in de novo AML. Methylation -specific PCR (MSP) demonstrated the hypermethylation status of p16 promoter gene in only 1 of 5 RAEB cases. However, MSP for p14 promoter gene showed the hypermethylation in 2 of 7 RA, 5 of 5 RAEB, 5 of 5 MDS-derived AML and 1 of 5 de novo AML cases, all of which showed negative or low expression of the p14 protein. And MSP for p15 promoter gene also disclosed the hypermethylation in 5 of 5 RAEB and 4 of 5 MDS-derived AML cases. These results indicated that hypermethylation of tumor suppressor genes, especially p14 and p15, may be involved in the pathogenesis of MDS and the early stage of MDS with the developing of leukemic transformation.