rs2431697, a Polymorphism of Mir-146a, Is a Precozing Marker of Progression to Secondary Myelofibrosis: New Epigenetic Regulation of Jak/Stat3 Signaling

Abstract Introduction: Transformation to secondary myelofibrosis (MF) occurs as part of the natural history of polycythemia vera (PV) and essential thrombocythemia (ET), the two more indolent Ph-negative myeloproliferative neoplasms (MPN). Once transformed, survival is remarkably shorted. Chronic inflammation plays a critical role in the progression of MPN, driving clonal expansion toward end stage disease. Importantly, MPN are characterized by the production of inflammatory cytokines, by both malignant and non-malignant clone. Inflammation and cancer share a common pathway, i.e. NF-κB. Interestingly, miR-146a regulates TLR/NF-κB pathway through the inhibition of its targets, IRAK1 and TRAF6, decreasing the production of cytokines. Based on: i) miR-146a-/- mice develop an MF-like phenotype with aging; and ii) miR-146a polymorphism (miRSNPs) rs2431697, influences its expression levels (50% decrease in TT individuals); we hypothesized that lower miR-146a-5p levels associated to this miRSNPs may result in high risk to develop MF. Objective: To evaluate the association of rs2431697 with MF transformation and to study the molecular mechanisms beyond this association. Methods: We genotyped rs2431697 in 938 patients (312 MF, 299 PV, and 327 ET) recruited from 13 tertiary Spanish institutions belonging to GEMFIN and 600 controls. The levels of miR-146a and IRAK1 were evaluated by qRT-PCR in total blood RNA of homozygous patients (TT=30, CC=25) with PV or ET and in healthy subjects (TT=7, CC=7). In miR-146a-/- mice, 2 and 9 months old, we evaluated spleen size and cellularity: degree of fibrosis in bone marrow (HE and STAT3 and pSTAT3 in granulocytic lysates by western blot. Results: Association analysis, taken controls as reference, showed that TT genotype (associated in the literature with low levels of mir-146a) is associated to MF with an OR of 1.36 (1.01-1.82, p=0.04). Among MF patients, the subgroup with the greatest differences was the one of secondary MF (OR = 1.47, CI: 0.98-2.20) (Table 1 a,b). Next, we compared the genetic frequencies of rs2431697 SNPs between the secondary MF patients and the population in risk. Confirming our hypothesis, we observed an enrichment of TT genotype in the post-PV/TE MF group (n=132) compared to the PV+TE group (n=626) (OR=1.51; p Conclusion: rs2431697-TT is an independent marker of early progression to secondary MF. The lower expression of miR-146a that this SNP confers is associated with an increase in JAK-STAT3 signaling. Our findings include, for the first time, miR-146a in the MPN signaling pathways. Thus, miR-146a, modulating the activation of NF-kB-IRAK1, could indirectly regulates JAK-STAT3 signalling. CINC424AES05T Download : Download high-res image (882KB) Download : Download full-size image Disclosures Ferrer Marin: Novartis: Consultancy, Research Funding; Incyte: Consultancy. Hernandez Boluda: Incyte: Consultancy; Novartis: Consultancy. Garcia Gutierrez: Incyte: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Research Funding, Speakers Bureau. Gomez-Casares: Bristol-Myers Squibb: Speakers Bureau; Incyte: Speakers Bureau; Novartis: Speakers Bureau. Besses: Novartis: Honoraria, Research Funding; Shire: Honoraria.