MicroRNA expression profiles in BCR-ABL-negative primary myelofibrosis with chromosome 7q defects

BCR-ABL-negative primary myelofibrosis (PMF) shows non-specific karyotype abnormalities in up to 30 % of patients, e.g. chromosome 7 defects, which are associated with an adverse prognosis. The impact of chromosome 7 aberrations on cell pathobiology is not yet known. We speculated that chromosome 7q-encoded regulatory microRNA might be one possible basis of instable disease. JAK2^V617F-positive cases of PMF with 7q defects (n = 4) were compared with PMF with non-7 aberrations (n = 3), PMF without karyotype aberrations (n = 3) and with a pool of three non-neoplastic controls. The microRNA expression profile of bone marrow cells was analysed with real-time PCR arrays. No 7q-related profile was found but, independent of the underlying karyotype, PMF cases show higher levels of 10q-encoded miR-146b. Re-evaluation in a second cohort (n = 50) confirmed miR-146b overexpression in fibrotic stage PMF. On the transcript level, no negative regulation of potential miR-146b targets could be found. In summary, no link between cytogenetic alterations and microRNA expression could be verified in PMF with 7q defects but 10q-encoded miR-146b overexpression was found to be associated with fibrosis.