Page 161 - 2019_05-HaematologicaMondo-web

miRNA in Richter syndrome
miR-150 was downregulated at the time of Richter trans- formation (Figures 2A and 3A). Finally, to further confirm our findings, we analyzed the levels of the differentially expressed human miRNA in an independent set of 58 patients with CLL/RS from Ulm University16 for whom microarray data were available (Online Supplementary Table S4). We confirmed that three miRNA, miR-21, miR-146b and miR-181b, were all upregulated in RS when compared to CLL (Figures 2A and 3B,C). Taken together, miR-21, a well-known oncogene,23 was found by all four analyses to be significantly more highly expressed at the time of Richter transformation than at the time of CLL diagnosis, strongly suggesting a role of this miRNA in the process of transformation to RS. In addition, three miRNA were found to be differentially expressed by three analyses: miR-146b and miR-181b were upregulated and miR-150 was downregulated at the time of Richter transformation. We will refer to this signature of four miRNA as the “restricted signature”. In addition, four miRNA were significantly different in two
analyses: miR-26a was significantly downregulated, while miR-24, miR-146a and miR-181a were significant- ly upregulated at the time of RS diagnosis. This signature of eight miRNA was designated as the “enlarged signa- ture” (Figures 1C and 2A). Of note, miRNA from the same families – miR-181a and miR-181b, and miR-146a and miR-146b - were present in both signatures. Three viral miRNA, the Epstein-Barr virus miRNA BART4 and BART16, and the Kaposi sarcoma herpes virus miRNA kshv-miR-K12-4 were differentially expressed in the Firefly analysis of all samples, but could not be evaluated in a cohort from an independent institution, as the array used to investigate the Ulm University cohort did not contain probes for non-human miRNA.
Genomic alterations may account for microRNA deregulation in a subset of cases of Richter syndrome
miRNA are often located at fragile sites in human and mouse genomes.24,25 To investigate whether the differen-
AC
B
Figure 2. microRNA profiling with the Firefly custom multiplex microRNA assay. (A) Summary of the significantly expressed miRNA in the profiling step of the project. (B) miR-21 and miR-181b are significantly upregulated, and miR-150 is significantly downregulated at the time of Richter transformation (RT) when compared to at chronic lymphocytic leukemia (CLL) diagnosis (Dx) for the paired Richter syndrome (RS) samples, but not for the paired control CLL samples. (C) miR-146b, miR-21 and miR-181b are significantly upregulated, and miR-150 is significantly downregulated at RT time when compared to at CLL diagnosis in the extended set of RS samples, but not in the extended set of control CLL samples. *P<0.05; **P<0.01; ***P<0.001. For additional Information, see Online Supplementary Figure S2.
haematologica | 2019; 104(5)
1007