In addition, p15(INK4B) methylation was significantly higher in advanced MDS than in early MDS (OR, 4.70; P < .001) and was linked to an unfavorable overall survival (multivariate analysis: HR, 1.78; 95% CI, 1.23-2.71).
However, animal model experiments over the last several years have produced a very different picture of how p15Ink4b functions in hematopoietic cells and how its loss contributes to myelodysplastic syndrome and myeloid leukemia.
The re-expression of p15 in PC-MDS cell line evaluated by qRT-PCR makes this novel cell line a suitable model for the studies of pharmacologic demethylation as a plausible mechanism resulting in hematologic response in myelodysplastic syndrome (MDS).
Recent exciting data suggest that methylation of p15 INK4b and of CTNNA1 (in 5q-), high level of methylation of other genes, absence of the TET2 mutation, down regulation of the lymphoid enhancer binding factor 1 (LEF1), mutation of the polycomb-associated gene ASXL1 and a specific 6-gene signature in gene expression profiling - are all associated with poor prognosis in MDS.
In this study, we examined the P15(INK4B) gene promoter methylation in patients with myelodysplastic syndrome and acute leukemia and its possible relationship with parvovirus B19 and Epstein-Barr virus infections.
Extensive statistical analyses of the whole CpG island revealed for the first time disease-specific methylation patterns of the CDKN2B gene in myeloid malignancies and small regions of differential methylation with high discriminatory power that enabled differentiation of even low-grade myelodysplastic syndrome samples from the controls, a result that was confirmed in an independent group of 9 control and 36 patient samples.
Since the function of cell cycle control genes including the cyclin-dependent kinase inhibitors known as p15(INK4b) and p16(INK4a), as well as p14(ARF) which blocks MDM-2 (an inhibitor of p53), the retinoblastoma (RB1) protein and the mismatch repair gene MGMT is critical for hematopoietic proliferation and differentiation, we performed methylation specific polymerase chain reaction (MSP) in low-density, non-adherent bone marrow cells from 49 patients with MDS.
Concurrent hypermethylation of > or = 3 genes was more frequent in advanced compared with early-stage MDS (P < or = 0.05), and hypermethylation of p15INK4B was associated with leukemic transformation in early MDS (P < or = 0.05).
Although FHIT and p15(INK4B) methylations were not correlated in MDS and AML, increased FHIT methylation at the relapse in AML was associated with p15(INK4B) methylation.
Progression of diseases such as MDS to secondary AML occur as a result of changes in the balance between cell proliferation and apoptosis and we will review targets in both these areas, including reversal of epigenetic silencing of genes such as p15(INK4B).
Nevertheless, some genes like p15INK4B in myelodysplastic syndrome (MDS) and p16INK4A in some lung cancer subtypes have been shown to confer a certain prognosis.
Methylation of p15INK4B is common, is associated with deletion of genes on chromosome arm 7q and predicts a poor prognosis in therapy-related myelodysplasia and acute myeloid leukemia.
The emergence of partially demethylated epigenotypes and re-establishment of normal p15 protein expression following the initial decitabine courses implicate pharmacologic demethylation as a possible mechanism resulting in hematologic response in MDS.