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MicroRNAs (miRNAs) are small RNA molecules which control the expression of many target messenger RNAs involved in cell differentiation, proliferation and apoptosis. Circulating microRNAs are potential biomarkers of diagnostic and prognostic impact in various inflammatory and malignant diseases. Unlike all other malignancies, studies of the prognostic implication of miRNA-21 expression in diffuse large B-cell lymphoma (DLBCL) patients have been a matter of debate. To our knowledge, there are no existing data up to date on the expression of miRNA-21 in hepatitis C virus (HCV) associated DLBCL.

MiRNA-21 expression was measured using Taq-Man quantitative RT-PCR in sera of 30 newly diagnosed DLBCL patients (HCV positive (n = 10), HCV negative (n = 20)) and 20 controls (HCV positive (n = 10), HCV negative (n = 10)). The diagnosis of DLBCL and its sub-classification in GCB and ABC subtypes were done by applying the criteria of the WHO classification of tumors of the hematopoietic and lymphoid tissues 2008 and revised in 2016 and were confirmed by Immunohistochemistry using antibodies to CD10, BCL-6, MUM-1 and BCL-2. HCV was diagnosed by detection of anti-HCV antibodies in sera of patients and controls by Enzyme-Linked Immunosorbent Assay (ELISA) technique and HCV genetic detection and quantification by polymerase chain reaction (PCR). All the patients received CHOP chemotherapy and were followed up for an average of 24 months.

MiRNA-21 expression was significantly higher in DLBCL patients than in controls (p = 0.00). Significant positive correlations between miRNA-21 and LDH, IPI and disease stage were detected (p < 0.05). Significantly higher miRNA-21 levels were detected in ABC subtype compared to GCB subtype (p = 0.00). Significantly higher miRNA-21 expression levels were detected in BCL6 negative, CD10 negative, MUM1 positive DLBCL cases compared to its levels in BCL6 positive, CD10 positive and MUM1 negative cases, (p = 0.018, 0.002 and 0.001 respectively). Higher miRNA-21 was associated with worse response (p = 0.016), 2-year overall (p = 0.017) and 2-year progression free survival with statistical significance (p= 0.003). Significantly higher miRNA-21 levels were detected in HCV positive DLBCL patients compared to HCV-negative patients (p = 0.00). Higher miRNA-21 levels were detected in HCV positive ABC subtype than GCB subtype (p = 0.05). Significantly higher levels were also detected in HCV positive controls compared to HCV-negative controls.

Our study showed that miRNA-21 was overexpressed in DLBCL patients, displaying higher levels in ABC than in GCB subtypes. MiRNA-21 was associated with poor response to treatment and survival in DLBCL. According to our results, miRNA-21 is a potential marker of necro-inflammation independent of its role in tumorigenesis, showing higher expression in HCV positive DLBCL patients compared to none hepatitis patients.