Abstract
Azacytidine (5-AZA) is the standard first-choice treatment for high-risk myelodysplasia (MDS) patients. However, the clinical outcome for those patients who interrupt treatment or whose disease failed to respond is very poor. In order to identify the cellular pathways that are modified by long-term exposure to 5-AZA, we evaluated key proteins associated with the autophagy pathway by reverse-phase microarray (RPPA). Comparing bone marrow mononucleated cells (BMMCs) obtained from 20 newly-diagnosed patients and after four 5-AZA cycles we found an increased autophagy signaling. We then evaluated ex-vivo the effect of the combination of 5-AZA with autophagy inhibitors chloroquine (CQ) and leupeptin. Since 5-AZA and CQ showed synergism due to an increase of basal autophagy after 5-AZA exposure, we adopted a sequential treatment treating BMMCs with 5 μM 5-AZA for 72 h followed by 10 μM CQ for 24 h and found increased apoptosis, associated to a reduction of G2M phase and increase in G0-G1 phase. Long-term exposure to 5-AZA induced the reduction of the autophagic marker SQSTM1/p62, reversible by CQ or leupeptin exposure. In conclusion, we identified autophagy as a compensatory pathway occurring in MDS-BM after long-term exposure to 5-AZA and we provided evidences that a sequential treatment of 5-AZA followed by CQ could improve 5-AZA efficacy, providing novel insight for tailored therapy in MDS patients progressing after 5-AZA therapy.
Highlights
Myelodysplastic Syndromes (MDS) are a heterogeneous group of bone marrow (BM) diseases characterized by peripheral cytopenias due to ineffective hematopoiesis and susceptibility to leukemic transformation
Our study revealed autophagy as a pro-survival pathway in MDS-bone marrow mononucleated cells (BMMCs) elicited by long-term treatment with 5-AZA, that could be triggered in those patients who failed to respond after initial clinical benefit
To investigate survival pathways elicited by long-term exposure to 5-AZA in vivo BMMCs were collected from newly-diagnosed MDS patients (Table 1) before (T0) and after first four 5-AZA cycles (T1)
Summary
Myelodysplastic Syndromes (MDS) are a heterogeneous group of bone marrow (BM) diseases characterized by peripheral cytopenias due to ineffective hematopoiesis and susceptibility to leukemic transformation. MDS are characterized by an uncoupling of proliferation and differentiation at the level of the hematopoietic stem cells (HSCs). According to the International Prognostic Scoring System (IPSS), MDS are distinguished into low- and high-risk subtypes based on the number of hematopoietic deficits, the percentage of marrow blasts, and cytogenetic pattern. One third of patients present with high-risk disease (Int-2 and High IPSS scores), associated with a significant probability of leukemia transformation with a corresponding lower apoptotic index and higher percentage of marrow blasts. In IPSS high-risk MDS patients, several therapeutic approaches have been used to kill abnormal blasts, including intensive conventional chemotherapy and low-dose cytarabine (Valent et al, 2007; Greenberg, 2011). Patients can sometimes achieve long-term remission or cure with allogeneic hematopoietic stem cell transplantation, but only those who are healthy enough to undergo the procedure can benefit from this type of therapy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
