Introduction: We aim to understand the role of microRNAs (miRNAs) in the high-grade transformation of follicular lymphoma (FL) to diffuse large B-cell lymphoma (DLBCL). Recently, a number of genomic aberrations associated with transformed FL (tFL) were described, including frequent aberrations activating MYC proto-oncogene. However, precise molecular mechanisms underlying FL transformation are largely unknown. Methods: We performed a global expression analysis of 377 miRNAs in paired samples (N = 16) from FL patients before vs after transformation to DLBCL (TLDA miRNA cards; Thermo Fisher Scientific), and additional 85 FL and 12 tFL samples were utilized in further analyses. Results: The miRNA expression profiling of paired FL-tFL samples (N = 8 pairs) revealed significant changes (P < .05, fold change >2.0) of 5 miRNAs. The most striking change was miR-150 down-regulation (~4 fold, P = .01), which was confirmed in additional cohorts of tFL vs FL. We further analyzed miR-150 expression in a cohort of 85 FL and found significantly lower miR-150 levels in patients with FLIPI score ≥3 (P = .03), with high proliferation rate of cells (Ki67 > 20%; P = .003) and with short survival (N = 85; median, 9.1 y vs not reached; P = .007). We have previously shown that miR-150 directly regulates FOXP1 protein in chronic lymphocytic leukemia, and high FOXP1 levels are known to associate with worse prognosis in DLBCL. Therefore, we assessed the association of miR-150 with FOXP1 in FL and found significantly lower miR-150 levels in patients with strong FOXP1 positivity (>70% cells). Moreover, FOXP1 levels were clearly increased in paired tFL compared to FL. We further examined the association of MYC and miR-150 in FL/tFL and found significantly lower miR-150 levels in MYC-positive FL/tFL vs MYC-negative FL. miR-150 down-modulation (P < .05) was also observed in B cells from transgenic mice heterozygous for MYC over-expression (MYC controlled by an Ig-alpha heavy-chain enhancer) in comparison to wild-type animals. Conclusions: Low-level expression of miR-150 associates with the transformation to DLBCL and shorter survival in FL. Our data suggest that MYC down-modulates miR-150 levels during transformation of FL to DLBCL, and this leads to up-regulation of FOXP1 transcription factor. The increased activity of FOXP1 likely directly contributes to the histological transformation of FL. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project CEITEC 2020 (LQ1601); Czech Science Foundation (project no. 16-13334Y); Ministry of Health of the Czech Republic, grant nos. 16-29622A; MUNI/A/1106/2016; MUNI/H/0865/2016; The research grant TACR (TE02000058/2014-2019); MH CZ - DRO (FNBr, 65269705); Wilmot Foundation. Keywords: follicular lymphoma (FL); microRNA

Agents targeting B-cell receptor (BCR) signaling-associated kinases such as Bruton tyrosine kinase (BTK) or phosphatidylinositol 3-kinase can induce mobilization of neoplastic B cells from the lymphoid tissues into the blood, which makes them potentially ideal to combine with anti-CD20 monoclonal antibodies (such as rituximab, obinutuzumab, or ofatumumab) for treatment of B-cell lymphomas and chronic lymphocytic leukemia (CLL). Here we show that interactions between leukemia cells and stromal cells (HS-5) upregulate CD20 on CLL cells and that administering ibrutinib downmodulates CD20 (MS4A1) expression in vivo. We observed that CLL cells that have recently exited the lymph node microenvironment and moved into the peripheral blood (CXCR4(dim)CD5(bright) subpopulation) have higher cell surface levels of CD20 than the cells circulating in the bloodstream for a longer time (CXCR4(bright)CD5(dim) cells). We found that CD20 is directly upregulated by CXCR4 ligand stromal cell-derived factor 1 (SDF-1α, CXCL12) produced by stromal cells, and BTK-inhibitor ibrutinib and CXCR4-inhibitor plerixafor block SDF-1α-mediated CD20 upregulation. Ibrutinib also downmodulated Mcl1 levels in CLL cells in vivo and in coculture with stromal cells. Overall, our study provides a first detailed mechanistic explanation of CD20 expression regulation in the context of chemokine signaling and microenvironmental interactions, which may have important implications for microenvironment-targeting therapies.

UNLABELLED:The objective of the work was to evaluate the frequency and time of incidence of cytomegaloviral (CMV) infection and disease in patients after allogeneic bone marrow transplantation (BMT). One hundred patients were followed up (70 with a related and 30 with an unrelated donor), who had transplantations during the period between XI/1996-XI/2000.METHODS USED:nested-PCR (MIE-gene) and antigenaemia (antigen pp65). Active CMV infection was proved in antigenaemia > or = 5 positive cells or in two consecutive positive PCR. The CMV syndrome was assessed in confirmed CMV infection and otherwise inexplicable febrile conditions and/or a drop of haemogram values. For the diagnosis of CMV pneumonia the clinical picture was needed, evidence of active CMV infection and on the X-ray of the lungs interstitial pneumonia. In 33 patients both methods were used, in 67 only PCR. The first positive test appeared 6-321 days after BMT (median +/- 49 days). CMV infection was proved in 44% cases, CMV syndrome in 30% and CMV pneumonia in 4%. In patients with a related donor CMV infection was found in 34.3%, CMV syndrome in 22.9%, CMV pneumonia in 1.4%. After unrelated donor BMT CMV infection was recorded in 66.7%, CMV syndrome in 46.7% and CMV pneumonia in 10% patients. Two patients died from CMV pneumonia. CMV pneumonia was diagnosed 57-115 days after BMT (median +/- 68 days. The risk of CMV infection is high in both groups of patients, in particular in patients after unrelated donor BMT (66.7%). As far as the development of CMV pneumonia was concerned, the mortality in the authors' group was 50%.