Mirna EXPRESSION SIGNATURES as PROGNOSTIC Markers IN ADVANCED Classical HODGKIN LYMPHOMA

Abstract 4157

In spite of the progress in the therapy of advanced stage classic Hodgkin lymphoma (cHL), still a significant proportion of patients fail to respond or relapse after complete remission. MicroRNAs (miRNA) are essential regulators of cell differentiation, emerging as robust predictor and prognostic markers. Specific miRNA signatures from the Hodgkin and Reed Sternberg cells (HRS) cells and their microenvironment have been proposed, but the potential prognostic role of them remains unclear. Here, we investigated whether miRNA signatures can allow to a better understanding of cHL pathogenesis and being applied in patient outcome prognostication.We have used mirRNA gene expression data from 32 samples of advanced cHL patients and 5 cHL derived cell lines (L540, L1236, L428, HDLM2, and KHMZ) to identify specific miRNA profiles from the tumoral cells and their non-tumoral microenvironment. A miRNA signature was identified in the cHL cell lines, probably reflecting functional properties of the HRS, whereas the others informed from properties of the reactive infiltrate. Selected miRNAs were further validated by performing laser capture microdissection using frozen samples in order to look for specific miRNAS preferentially expressed for either HRS cells and their surrounding microenvironment.

In addition, logistic regression and Cox analysis allowed us to identify a set of 102 miRNAs differentially expressed (p<0.05) among patients with favourable and unfavourable outcome that included members of the miR-17-92 cluster such us mir-17, mir-92a and mir-92b* and other miRNAs known to be involved in cancerogenesis. A restricted group of 32 miRNAS with better prognostic capacity was further selected to set up a quantitative RT-PCR assay and explore the potential diagnostic application of their expression in an independent series of 96 formalin-fixed paraffin-embedded (FFPE) cHL samples.

Bioinformatics target prediction (miRBase and TargetScan) and the web based computational tool DIANA-mirPath, were used in the identification of molecular pathways and target genes potentially regulated by the expression of these mirRNAs. Combined analysis of miRNAs, paired with bioinformatic target prediction, revealed a series of genes and pathways targeted by a small number of miRNAs, including essential pathways for lymphoma survival like MAPK signaling pathway, cell cycle, Jak-STAT signaling pathway and others.

In conclusion, specific miRNA signatures for the HRS cells and their microenvironment can be identified in cHL samples, and improve our understanding in cHL pathogenesis. Selected miRNAs can be used in paraffin-embedded tissue for prognosis of advanced cHL cases, and can be incorporated in an RT-PCR assay with potential clinical application in advanced cHL.