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Background: Allogeneic stem-cell transplantation (HSCT) is the only curative treatment in myelodysplastic syndromes (MDS). Azacitidine (AZA) is increasingly used prior to HSCT, however in Europe it is only approved for patients who are not eligible for HSCT., Patients and Methods: We conducted a phase II multicenter study to prospectively evaluate the feasibility of HSCT after treatment with AZA in 70 patients with a myelodysplastic syndrome (MDS), 19 with acute myeloid leukemia (AML), and 8 with chronic myelomonocytic leukemia (CMML). After a median of four cycles (range 1-11): 24% of patients achieved complete remission, 14% partial remission, 8% hematologic improvement, 32% had stable and 22% progressive disease. Ten patients discontinued treatment before the planned four cycles, due to an adverse event in nine cases., Results: A HSC donor was identified in 73 patients, and HSCT was performed in 54 patients (74% of patients with a donor). Main reasons for turning down HSCT were lack of a donor, an adverse event, or progressive disease (9, 12, and 16 patients, respectively). At a median follow-up of 20.5 months from enrolment, response to AZA was the only independent prognostic factor for survival. Compared to baseline assessment, AZA treatment did not affect patients' comorbidities at HSCT: the HCT-CI remained stable in 62% patients, and worsened or improved in 23% and 15% of patients, respectively., Conclusions: Our study shows that HSCT is feasible in the majority of patients with HR-MDS/AML/CMML-2 after AZA treatment. As matched unrelated donor was the most frequent source of donor cells, the time between diagnosis and HSCT needed for donor search could be 'bridged' using azacitidine. These data show that AZA prior to HSCT could be a better option than intensive chemotherapy in higher-risk MDS. The trial has been registered with the EudraCT number 2010-019673-1., (© The Author 2017. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

The nucleoside analog azacitidine (AZA) is used in the treatment of myelodysplastic syndromes (MDS), but 30-40% of patients fail to respond or relapse after treatment. Hence, to identify new molecular alterations that allow for identification of patients unlikely to respond to AZA could impact the utility of this therapy. We determined the expression levels of genes involved in AZA metabolism: UCK1, UCK2, DCK, hENT1, RRM1 and RRM2 using quantitative PCR in samples from 57 patients with MDS who received AZA. Lower expression of UCK1 was seen in patients without a response to AZA (median 0.2 vs 0.49 for patients with response to AZA, P=0.07). This difference in UCK1 expression was not influenced by aberrant methylation of the UCK1 promoter. In addition, the seven polymorphic loci found in the coding sequence were not associated with UCK1 gene expression nor AZA response. Silencing of UCK1 by siRNA leads to blunted response to AZA in vitro. The univariate analysis revealed that patients expressing lower than median levels of UCK1 had a shorter overall survival (P=0.049). Our results suggest that expression level of UCK1 is correlated with clinical outcome and may influence the clinical response to AZA treatment in patients with MDS.

A combination of demethylating agents and histone deacetylase inhibitors (HDACi) has been proposed as a novel therapy in leukemia and myelodysplasia. In HL-60 cells azacytidine (AZA) and Metacept-1 (MCT-1), a novel HDACi augmented inhibition of cell growth and increased apoptosis. In identifying a molecular mechanism responsible for these effects MCT-1 alone and in combination with AZA induced p15INK4b, p21WAF1/CIP1 and Caspase-3 whilst attenuating Bcl-XL expression. Interestingly, MCT-1 in combination with AZA significantly induced the recently identified suppressor of leukemogenesis Nur77 and attenuated AZA-induced MMP-9 expression. The combination of MCT-1 and AZA is more effective in inhibiting leukemic cell growth and induction of apoptosis. Regulation of a recently identified tumour suppressor gene together with cell cycle, apoptosis and matrix degrading proteases may underpin the molecular mechanism responsible for these effects.