PB2194 DE‐REGULATION OF MIRNAS DURING TREATMENT OF PATIENTS AFFECTED BY MYELOFIBROSIS WITH RUXOLITINIB
Authors: S. Galimberti, C. Baratè, F. Ricci, S. Balducci, F. Guerrini, S. Grassi, E. Ciabatti, S. Barsotti, M. Petrini
Journal: HemaSphere (2019)

Background: MicroRNAs (miRNAs) are a family of small non coding RNAsthathave been associated with control of cell cycle, signal transduction, and many other cell functions in several hematological diseases. In myelofibrosis (MF), it has been reported that 48 miRNAs were expressed in a different way in respect of healthy donors, with particular relevance attributed to miR‐127, miR‐140 and miR‐345 [Liu Y, 2017]. Moreover, hyper‐expression of miR‐494, silencing SOCS6, might contribute to the megakaryocyte hyperplasia commonly observed in MF, thus sustaining a pathogenetic role for these small RNAs [Rontauroli S, 2017]. Nevertheless, it is not yet clear what kind of modulation of miRNAs can occur during treatment with ruxolitinib. Aims: The aim of the present study was to identify eventual changes of miRNAs expression during ruxolitinib therapy in order to try to better understand the action mechanism of this JAK2 inhibitor. Methods miRNAs were extracted from bone marrow and peripheral blood samples harvested in 4 patients with MF before starting ruxolitinib and after 3 months of therapy. As controls, 15 peripheral blood samples from healthy subjects and one sample from a bone marrow donor were employed. The expression of 675 miRNAs was assessed by the TaqMan ® Low Density Arrays kit (ThermoFisher) and miRGator software was used to identify the respective target genes. Results: No differences in terms of miRNAs expression levels were observed between bone marrow and peripheral blood of MF cases, nor between patients and controls. After 3 months of ruxolitinib, 9 miRNAs resulted significantly up‐regulated: miR‐25, miR‐145, miR‐186, miR‐142‐3b, let‐7b, miR‐30d, miR‐188, miR‐942, and miR‐378. Interestingly, among targets genes of these miRNAs, there are JAK2, MPL, TET2, ASXL1, CBL, IDH1, IDH2, IKZF1, EZH2, genes that are either responsible for MF pathogenesis or prognostic in terms of long‐term outcome. Interestingly, miRNA‐145 has been previously reported to be up‐regulated in PV, and let‐7b is inversely correlated with JAK2V617F mutation in MPN [Bruchova H, 2008]. In our series of 20 patients treated by ruxolitinib we did not observe a significant modulation of JAK2 mutational load, but the interaction between let‐7b and JAK2 could be an interesting issue. Moreover, miR‐188 has been reported to suppress macrophage oxidation and plasma expression of pro‐inflammatory factors [Zhang XF, 2018], that could explain the anti‐inflammatory action of ruxolitinib observed in vivo, with a significant improvement of quality of life of MF patients during treatment. This anti‐inflammatory effect could be also sustained by the miR‐186, that has been reported to inhibit HIF‐1alpha factor, involved in the inflammatory processes [Gardner PJ, 2017], and by the up‐regulation of miR‐145, that seems to inhibit TGFBR2 and reduce sepsis in a murine model [Ma F, 2019]. Moreover, the over‐expression of miR‐30d has been associated with a reduced proliferation in colon cancer [Muhammad S, 2019], and miR‐142 high levels play an anti‐oncogenic activity in breast cancer [Mansoori B, 2019]. If it would be true also in MF, we could argue that ruxolitinib could also exert an anti‐proliferative effect. Summary/Conclusion: Even if only preliminary and on a very small number of cases, this study supports the possible role of miRNAs in the modulating the expression of genes involved in pathogenesis and progression of MF during treatment with ruxolitinib. This could help to better understand the action mechanisms of this important drug.