Anaplastic large cell lymphoma (ALCL) is a rare, aggressive, non-Hodgkin's lymphoma that is characterized by CD30 expression and disease onset in young patients. About half of ALCL patients bear the t(2;5)(p23;q35) translocation, which results in the formation of the nucleophosmin-anaplastic lymphoma tyrosine kinase (NPM–ALK) fusion protein (ALCL ALK+). However, little is known about the molecular features and tumour drivers in ALK-negative ALCL (ALCL ALK−), which is characterized by a worse prognosis. We found that ALCL ALK−, in contrast to ALCL ALK+, lymphomas display high miR-155 expression. Consistent with this, we observed an inverse correlation between miR-155 promoter methylation and miR-155 expression in ALCL. However, no direct effect of the ALK kinase on miR-155 levels was observed. Ago2 immunoprecipitation revealed miR-155 as the most abundant miRNA, and enrichment of target mRNAs C/EBPβ and SOCS1. To investigate its function, we over-expressed miR-155 in ALCL ALK+ cell lines and demonstrated reduced levels of C/EBPβ and SOCS1. In murine engraftment models of ALCL ALK−, we showed that anti-miR-155 mimics are able to reduce tumour growth. This goes hand-in-hand with increased levels of cleaved caspase-3 and high SOCS1 in these tumours, which leads to suppression of STAT3 signalling. Moreover, miR-155 induces IL-22 expression and suppresses the C/EBPβ target IL-8. These data suggest that miR-155 can act as a tumour driver in ALCL ALK− and blocking miR-155 could be therapeutically relevant. Original miRNA array data are to be found in the supplementary material (Table S1). © 2015 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Anaplastic large-cell lymphoma (ALCL) is a mature T-cell malignancy that is subdivided further into two distinct disease entities based on the presence or absence of the anaplastic lymphoma kinase (ALK) fusion protein. ALK+ ALCL bears the t(2;5) (p23;q35) translocation in greater than 80% of cases, which results in the expression of the chimeric nucleophosmin (NPM)-ALK. This leads to the activation of many different growth-promoting and anti-apoptotic pathways, including PI3K/Akt1/mTOR, Jak/Stat and AP-1. Recently, micro-RNAs (miRNAs) have emerged as tiny but potent molecules to regulate cell differentiation and proliferation. In a recent publication we have reported that miR-155 is up-regulated in ALK+ and down-regulated in ALK- ALCL. We have now identified an additional miRNA, miR-146a, that is significantly higher expressed in ALK- ALCL. Both miRNAs are strongly induced by T-cell activation. We report here that in ALCL cell lines that highly express miR-155 (like ALK- Mac1 and Mac2a) its target protein CCAAT-enhancer-binding protein ≤ (C/EBPβ) is suppressed and moreover reintroduction of miR-155 in cell lines that have low miR-155 levels (Karpas-299, SR786, SU-DHL-1, SUP-M2) can actively down-regulate C/EBPβ. Conversely, high expression of miR-146a in primary ALK- ALCL FFPE specimens corresponds to low expression of its target protein IL1 receptor-associated kinase 1 in ALK - cell lines. Due to the known roles of miR-155 and miR-146a we assessed cytokine release in a set of ALCL cell lines with and without the ALK translocation. Interestingly, we found expression of cytokines including IL-6, IL-10, IL-21 and IL-22 in ALCL cell lines. Inflammatory cytokines IL-6, IL-21 and IL-22 were 4 to 10-fold higher in ALK- cell lines, whereas anti-inflammatory IL-10 levels were not related to ALK status. Reintroduction of miR-155 into the ALK+ cell lines Karpas-299 and SR786 was able to enhance expression of IL-22. To test the influence of miR-155 on ALK- ALCL tumor growth in vivo we injected 5x10^6 Mac1 cells with low (transfected with anti-miR) or high miR-155 (transfected with pre-miR) into the flanks of BALB/c mice. High miR-155 led to a significantly enhanced tumor growth and increased IL-22 in the serum, suggesting miR-155 as tumor driver and potential therapeutic target in ALK- ALCL. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1108. doi:1538-7445.AM2012-1108

In the future a close collaboration of geneticists, biochemists, and clinicians together with new technologies such as deep sequencing will allow the refinement of treatment strategies in many diseases including PTCLs and NHLs. This refinement will allow treatments to be prepared according to the need of the individual patient.