Summary: Circulating nucleic acids have been shown to have potential as non‐invasive diagnostic markers in cancer. We therefore investigated whether microRNAs also have diagnostic utility by comparing levels of tumour‐associated MIRN155 (miR‐155), MIRN210 (miR‐210) and MIRN21 (miR‐21) in serum from diffuse large B‐cell lymphoma (DLBCL) patients (n = 60) with healthy controls (n = 43). Levels were higher in patient than control sera (P = 0·009, 0·02 and 0·04 respectively). Moreover, high MIRN21 expression was associated with relapse‐free survival (P = 0·05). This is the first description of circulating microRNAs and suggests that microRNAs have potential as non‐invasive diagnostic markers for DLBCL and possibly other cancers.

Jessica Okosun, Csaba Bödör and colleagues performed whole-genome or whole-exome sequencing on 10 follicular lymphoma and transformed follicular lymphoma pairs, followed by deep sequencing of 28 target genes in an additional 122 cases. They identify recurrent mutations in linker histone genes and genes involved in JAK-STAT signaling, NF-κB signaling and B cell development. Follicular lymphoma is an incurable malignancy1, with transformation to an aggressive subtype representing a critical event during disease progression. Here we performed whole-genome or whole-exome sequencing on 10 follicular lymphoma–transformed follicular lymphoma pairs followed by deep sequencing of 28 genes in an extension cohort, and we report the key events and evolutionary processes governing tumor initiation and transformation. Tumor evolution occurred through either a 'rich' or 'sparse' ancestral common progenitor clone (CPC). We identified recurrent mutations in linker histone, JAK-STAT signaling, NF-κB signaling and B cell developmental genes. Longitudinal analyses identified early driver mutations in chromatin regulator genes (CREBBP, EZH2 and KMT2D (MLL2)), whereas mutations in EBF1 and regulators of NF-κB signaling (MYD88 and TNFAIP3) were gained at transformation. Collectively, this study provides new insights into the genetic basis of follicular lymphoma and the clonal dynamics of transformation and suggests that personalizing therapies to target key genetic alterations in the CPC represents an attractive therapeutic strategy.

Diffuse large B cell lymphoma (DLBCL) is an aggressive malignancy that accounts for nearly 40% of all lymphoid tumors. This heterogeneous disease can be divided into germinal center B cell‐like (GCB) and activated B cell‐like (ABC) subtypes by gene expression and immunohistochemical profiling. Using microarray analysis on prototypic cell lines, we identified microRNAs (miR‐155, miR‐21 and miR‐221) that were more highly expressed in ABC‐type than GCB‐type cell lines. These microRNAs were over‐expressed in de novo DLBCL (n = 35), transformed DLBCL (n = 14) and follicular center lymphoma cases (n = 27) compared to normal B cells. Consistent with the cell line model, expression levels were higher in DLBCL cases with an ABC‐type immunophenotype than those that were GCB‐type (p < 0.05). Moreover, using multivariate analysis we found that expression of miR‐21 was an independent prognostic indicator in de novo DLBCL (p < 0.05). Interestingly, expression levels of both miR‐155 and miR‐21 were also higher in nonmalignant ABC than in GCB cells. As we also demonstrate that expression of microRNAs can be measured reliably from routine paraffin‐embedded biopsies of more than 8‐years‐old (p < 0.001), we suggest that microRNAs could be clinically useful molecular markers for DLBCL as well as other cancers.

The effective and efficient management of cancer patients relies upon early diagnosis and/or the monitoring of treatment, something that is often difficult to achieve using standard tissue biopsy techniques. Biological fluids such as blood hold great possibilities as a source of non-invasive cancer biomarkers that can act as surrogate markers to biopsy-based sampling. The non-invasive nature of these “liquid biopsies” ultimately means that cancer detection may be earlier and that the ability to monitor disease progression and/or treatment response represents a paradigm shift in the treatment of cancer patients. Below, we review one of the most promising classes of circulating cancer biomarkers: microRNAs (miRNAs). In particular, we will consider their history, the controversy surrounding their origin and biology, and, most importantly, the hurdles that remain to be overcome if they are really to become part of future clinical practice.

Research over the last few years has demonstrated the increasing role of microRNAs (miRNAs) as major regulators of gene expression in diverse cellular processes and diseases. Several viruses, particularly herpesviruses, also use the miRNA pathway of gene regulation by encoding their own miRNAs. Marek's disease (MD) is a widespread lymphomatous neoplastic disease of poultry caused by the highly contagious Marek's disease virus type 1 (MDV-1). Recent studies using virus-infected chicken embryo fibroblasts have identified at least eight miRNAs that map to the R _L /R _S region of the MDV genome. Since MDV is a lymphotropic virus that induces T-cell lymphomas, analysis of the miRNA profile in T-cell lymphoma would be more relevant for examining their role in oncogenesis. We determined the viral and host miRNAs expressed in MSB-1, a lymphoblastoid cell line established from an MDV-induced lymphoma of the spleen. In this paper, we report the identification of 13 MDV-1-encoded miRNAs (12 by direct cloning and 1 by Northern blotting) from MSB-1 cells. These miRNAs, five of which are novel MDV-1 miRNAs, map to the Meq and latency-associated transcript regions of the MDV genome. Furthermore, we show that miRNAs encoded by MDV-1 and the coinfected MDV-2 accounted for >60% of the 5,099 sequences of the MSB-1 “miRNAome.” Several chicken miRNAs, some of which are known to be associated with cancer, were also cloned from MSB-1 cells. High levels of expression of MDV-1-encoded miRNAs and potentially oncogenic host miRNAs suggest that miRNAs may have major roles in MDV pathogenesis and neoplastic transformation.