CDKN2B methylation status and isolated chromosome 7 abnormalities predict responses to treatment with 5-azacytidine

Abstract

5-Azacytidine, a DNA methyl transferase inhibitor, is effective in patients with myelodysplastic syndromes (MDS). Whether responses to 5-Azacytidine are achieved by demethylation of key genes or by cytotoxicity is unclear. Of 34 patients with MDS or acute myeloid leukaemia (AML) treated with 5-Azacytidine, 7 achieved complete remissions (CR) (21%) and 6 achieved haematological improvement. All six had less than 5% bone marrow (BM) blasts at the time of haematological improvements (HI) (2 had pre-existing refractory anaemia (RA), 4 had refractory anaemia with excess blasts (RAEB)). A further patient with RAEB had blast reduction to less than 5% without HI. Five of the seven (71%) complete responders had chromosome 7 abnormalities. BM CR predicted longer overall survival (OS) (median 23 versus 9 months, P ¼ 0.015). Bisulphite genomic sequencing (BGS) of the CDKN2B (p15 INK4b) promoter showed low level, heterogeneous pretreatment methylation (mean 12.2%) in 14/17 (82%) patients analysed. Lower baseline methylation occurred in responders (9.8% versus 16.2% in non-responders P ¼ 0.07). No response was seen in patients with 424% methylation, in whom p15INK4b mRNA was not expressed. 5-Azacytidine reduced CDKN2B methylation by mean 6.8% in 8/17 (47%) patients, but this did not correlate with response. At 75 mg/m 2 , cell death (reduced BM cellularity (P ¼ 0.001) and increased apoptosis (P ¼ 0.02)) rather than demethylation of CDKN2B correlates with response. Patients with 424% methylation may benefit from alternative dosing or combination strategies.

The DNA methyltransferase inhibitors azacitidine, decitabine and zebularine exert differential effects on cancer gene expression in acute myeloid leukemia cells

“…This is consistent with the clinical observation that MDS/AML patients with monosomy 7 respond remarkably well to 5AC or DAC but not to AraC. 18,40,41 Second, it is conceivable that some patients with MDS or AML refractory to one DNMT inhibitor might still respond to one of the others, as was indeed reported on the basis of a small series of cases. 42 Third, a promising prospect would be the use of DNMT-inhibiting cytosine analogues in combination, with the goal of reciprocally complementing their activity.…”

“…Of note, the marginal extent of CDKN2B hypomethylation under the low-dose 5AC schedule used here is in good agreement with clinical in vivo observations. 18 We next extended the methylation analysis to the promoters of 14 additional genes and to LINE1 sequences, which are unbiased for any particular locus and so provide a global measurement of DNA methylation. MassARRAY technology was used to quantify DNA methylation at the CDKN1C, CDKN2B, CEBPA, CXCR4, DLK1, ID1, ID2, ID3, MPO, NFAT2CIP, PPAP2A, PRG2, RAB13, SMAD7 and TP73 loci and at genomic LINE1 sequences (Figure 3b; Supplementary Figure 1).…”

Nucleoside analogs: molecular mechanisms signaling cell death

“…Conversely, therapeutic response in these trials were associated with a demethylation of initially hypermethylated CpG islands of the p15 gene and re-expression of p15 protein (Kantarjian et al, 2007b). Although such correlations between p15 and treatment response emphasize the potential importance of p15 re-expression to disease treatment, it remains unclear whether remission in patients treated with broad range demethylating agents is a direct result of re-expressing p15 (Raj et al, 2007). Regarding their mechanism of action, the efficacy of azacytidine or decitabine as antineoplastic agents appears to result from two distinct mechanisms: cytotoxicity when administered at high doses and inhibition of DNA methyltransferases when given at low doses.…”

Decitabine improves progression-free survival in older high-risk MDS patients with multiple autosomal monosomies: results of a subgroup analysis of the randomized phase III study 06011 of the EORTC Leukemia Cooperative Group and German MDS Study Group

“…However, it is unclear why these drugs differ from cytarabine and other cytotoxic agents in that regard. Equally notable was the recurrent observation of activity of DAC [13,[15][16][17][18] and azacytidine [10,19] in MDS/AML patients with sole monosomy 7-also a robust clinical result but as yet lacking a mechanistic explanation. A monosomy might be only one of several abnormalities and may not exhibit prognostic impact itself [20,21].…”