Methylation and myelodysplastic syndromes: When and where?

Comparison between decitabine and azacitidine for the treatment of myelodysplastic syndrome: a meta-analysis with 1,392 participants

The hypomethylating agents decitabine and azacitidine have been found to improve the outcome of patients with myelodysplastic syndrome (MDS); however, the clinical choice between them is controversial. Therefore, this meta-analysis was performed to compare the efficacy, toxicity, and survival advantage of decitabine and azacitidine in patients with MDS. Eleven trials with a total of 1392 patients with MDS (decitabine, n = 768; azacitidine, n = 624) were included for analysis. The pooled estimates of partial response, hematologic improvement, and overall response rates for azacitidine were significantly higher than for decitabine. There were no differences between these 2 drugs regarding complete response, red blood cell transfusion-independent rates, and grade 3 or 4 hematologic toxicity. When compared with best supportive care, azacitidine significantly improved overall survival (hazard ratio [HR], 0.69; 95% CI, 0.54-0.87) and time to acute myeloid leukemia transformation (HR, 0.51; 95% CI, 0.35-0.74). But these benefits were not found with decitabine. Among patients with higher risk (International Prognostic Scoring System value of 3) or older than 75 years, treatment with azacitidine was a favorable factor, whereas decitabine showed no advantage. Therefore, with higher overall response rates and better survival benefits, azacitidine is recommended as the first-line hypomethylating agent for MDS, especially in elderly patients or those with high risk.

Loss of the tumor suppressor p15Ink4b enhances myeloid progenitor formation from common myeloid progenitors

OBJECTIVE

The tumor suppressor p15Ink4b (Ink4b) is a cell-cycle inhibitor that is inactivated in a high percentage of acute myeloid leukemia and myeloid dysplasia syndrome cases. Despite this, the role of Ink4b in hematopoiesis remains unclear. Here we examined the role of Ink4b in blood cell formation using Ink4b-deficient (Ink4b(-/-)) mice.

METHODS

We compared the bone marrow (BM) of Ink4b(-/-) and wild-type mice using flow cytometric, colony-forming unit and competitive repopulating assays (CRA). The proliferation, differentiation, self-renewal, and apoptosis of progenitor cells were further compared by in vitro and in vivo methods.

RESULTS

BM from Ink4b(-/-) mice contained increased numbers of granulocyte-monocyte progenitors and Gr-1(+) cells and showed a competitive advantage over wild-type cells in myeloid cell formation by CRA. Ink4b(-/-) progenitors did not demonstrate increased proliferation, self-renewing potential, or reduced apoptosis. Instead, Ink4b(-/-) common myeloid progenitors (CMPs) showed increased myeloid progenitor formation concomitant with reduced erythroid potential.

CONCLUSIONS

This work establishes a role for Ink4b in regulating the differentiation of CMPs and indicates that loss of Ink4b enhances the formation of myeloid progenitors.