Role of the MSC-Derived Exosomal and Endogenous JAK2-SET/PP2A-Beta Catenin-Modulator Mir-300 in Leukemic Stem/Progenitor Proliferation and Survival in CML

Konference: 2015 57th ASH Annual Meeting - účast ČR

Kategorie: Maligní lymfomy a leukémie

Téma: 631. Chronic Myeloid Leukemia: Biology and Pathophysiology, excluding Therapy: Targeting Leukemic Stem Cells in Chronic Myeloid Leukemia

Číslo abstraktu: 53

Autoři: Giovannino Silvestri, Ph.D.; Lorenzo Stramucci, Ph.D.; Justin Ellis; Justine Yu; Jason Harb, Ph.D.; Paolo Neviani, Ph.D.; MD Guido Marcucci; Bc. Klára Šrůtová; Mgr. Kateřina Machová (Poláková), Ph.D.; Denis-Claude Roy; MD Peter Hokland; MD Michael W. Deininger, Ph.D.; MD Ravi Bhatia; Prof. Carlo Gambacorti-Passerini; Dragana Milojkovic; Dr. Alistair G. Reid, BSc, PhD; Prof. Jane F. Apperley, MBChB, MD, FRCP, FRCPath; Ferenc Livák, Ph.D.; MD Maria R. Baer; Rossana Trotta, Ph.D.; Prof. Dr. Danilo Perrotti, Ph.D.

MiR-300 is a microRNA predicted to target multiple components of the BCR-ABL1 / JAK2 / hnRNPA1 / SET / PP2A / β-catenin pathway, which is essential for survival/self-renewal of leukemic progenitors and quiescent TKI-resistant Ph+ hematopoietic stem cells (HSCs). Nanostring arrays analysis of bone marrow (BM) cells from healthy individuals (n=5) and CML patients (n=10) showed gradual inhibition of miR-300 expression (CML-CPmiR-300>CML-BCmiR-300).

MiR-300 transduction in CMLCD34+ cells and BCR-ABL1+ cell lines decreased JAK2, β-catenin, hnRNPA1 and SET expression and increased PP2A activity. Targets were confirmed by miR-300 expression in BCR-ABL1+ cells expressing Flag-tagged miR-300-targets lacking or carrying a wild-type or mutated 3’UTR. Restored miR-300 expression in CMLCD34+ cells and/or BCR-ABL1+ cell lines impaired cell cycle progression, proliferation and clonogenic potential, markedly reduced LTC-ICs, and increased TKI sensitivity. Notably, miR-300 expression was inhibited by BCR-ABL1 in proliferating cells. Accordingly, imatinib restored miR-300 expression in CD34+ dividing progenitors and BCR-ABL1+ cell lines without altering miR-300 levels in quiescent (CFSEMAX) CMLCD34+ cells (n=3), consistent with the BCR-ABL1 kinase-dependent activation of the Jak2/SET/PP2A/β-catenin pathway in CML progenitors but not quiescent Ph+ HSCs. Indeed, ectopic SET expression counteracted the negative effects of mir-300 on cell proliferation and survival.  Surprisingly, miR-300 levels were increased in CD34+CD38- compared to CD34+CD38+ CML cells, and >20-fold higher in CFSEMAX compared to dividing CMLCD34+ cells (n=4).  

To determine whether enhanced miR-300 expression in quiescent cells depends on cell autonomous events or is induced by the BM microenvironment, we exposed BCR-ABL+ cells to conditioned medium (CM) of HS-5 or hTERT mesenchymal stem cells (MSC). CM strongly decreased proliferation, induced imatinib but not FTY720 (PP2A activator) resistance, increased miR-300 levels, decreased BCR-ABL1 activity and Jak2 expression but not its activity, and did not alter b-catenin levels or PP2A activity. Interestingly, miR-300 was found in MSC-derived exosomes, and its expression increased in BCR-ABL1+ cells exposed to exosomes. Accordingly, proliferation of CML-BCCD34+and LAMA-84 cells was strongly reduced upon exposure to MSC-derived exosomes. These effects were abolished when we used CM from MSCs transduced with a miR-300 antagomir.

Altogether our results indicate that downregulation of miR-300 appears necessary for the activation of JAK2/SET/PP2A/b-catenin survival signals in CML progenitors. Conversely, increased miR-300 levels (endogenous and MSC-derived) seem to be required for HSC quiescence.

Disclosures: Deininger: Novartis: Other: Consulting or Advisory Role , Research Funding ; BMS: Other: Consulting & Advisory Role , Research Funding ; Celgene: Research Funding ; Genzyme: Research Funding ; Gilead: Research Funding ; ARIAD Pharmaceutical Inc.: Other: Consulting or Advisory Role ; Incyte: Other: Consulting or Advisory Role ; Pfizer: Other: Consulting or Advisory Role . Milojkovic: BMS: Honoraria ; ARIAD Pharmaceuticals Inc.:Honoraria ; Novartis: Honoraria ; Pfizer: Honoraria.

Datum přednesení příspěvku: 5. 12. 2015