Studies to identify circulating miRNAs as non-invasive tool predictor of poor outcome and therapy response in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a clinically and genetically heterogeneous neoplasm with aggressive clinical course. Primary refractory patients to R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) standard treatment present a dismal clinical outcome with a low survival expectancy despite the current salvage treatment strategies. To date, none of the available prognostic factors is able to properly catch the DLBCL complexity and early recognize primary refractoriness. Thus, the identification of new non-invasive prognostic/predictive biomarkers, easily detected in the peripheral blood, is of vital importance to approach refractory patients with alternative treatments. MicroRNAs (miRNAs) are small RNAs which play a critical regulatory role in many physiological and pathological processes. They are frequently deregulated in cancer and they circulate in biofluids in a very stable form, making them interesting candidates as non-invasive biomarkers in cancer diagnosis, prognosis and therapeutic response. Recently, in a pilot study on miRNA profiles in DLBCL patient’s serum, circulating miR-22-3p was found to be significantly correlated with a worse progressionfree survival (PFS), suggesting its role as predictor of poor clinical outcome. However, it is recognized that single miRNAs may provide a low accuracy as cancer biomarkers, due to the multifactorial nature of tumours and the variety of targets for a single miRNA. In this thesis work through a serum miR-22 profiling in a validation cohort of DLBCL patients, we confirmed a significant correlation of miR-22 levels at diagnosis with 2-year PFS. Moreover, its expression in serum is inversely correlated to that in paired tumor tissue, suggesting a role as tumor suppressor. Supporting these results, we found that miR-22 expression and release from DLBCL cells are related to therapy response and adversely affects cell proliferation. Lastly, a small RNA-seq analysis in serum samples of responsive to R-CHOP versus refractory patients showed 5 differentially expressed serum miRNAs as highly sensitive and specific predictive non-invasive biomarker for DLBCL management. We also found that the selected miRNA signature targets are significantly enriched in potentially druggable biological processes. These data suggest that circulating miRNAs may represent a source of information complementary to the techniques currently adopted in clinical practice and a key element in the “Bench to Bedside” research to translate scientific findings into therapeutic interventions.