The Importance of MicroRNA Deregulation in the Molecular Pathogenesis and Histological Transformation of Follicular Lymphoma
Abstract
Background: Molecular pathogenesis of follicular lymphoma (FL) is characterized by substantial dysregulation of epigenetic regulators. Many cases of FL are associated with the aberrant expression of non-coding regulatory RNAs, namely microRNAs (miRNA).
Here we studied changes in miRNA expression and their association with histological transformation of FL to diffuse large B-cell lymphoma (DLBCL). Material and Methods: To identify changes in miRNA levels during FL transformation we performed a global expression analysis of 377 miRNAs in 16 samples (8 pairs) from FL patients vs. transformed FL (tFL) (TLDA miRNA cards; Thermo Fisher Scientific).
The association of miRNA expression with clinical-biological characteristics and target proteins were further analyzed in a cohort of 89 FL patients. Results: The miRNA expression profiling of paired FL-tFL samples revealed statistically significant changes in the expression of five miRNAs (p 20%), higher FLIPI score (>= 3) and shorter overall survival of FL patients.
Furthermore, we found that this miRNA regulates the levels of FOXP1 protein in FL. The patients with high-level FOXP1 expression (> 70% positive cells) had significantly shorter overall survival in comparison to those with low-level FOXP1 expression (< 30% positive cells).
Moreover, FOXP1 protein levels were higher in most tFL samples compared to FL before transformation. Conclusion: We found miRNAs associated with the transformation of FL to a more aggressive DLBCL, and described that one of them could serve as a prognostic marker.
We found that reduced expression of this tFL-associated miRNA results in increased levels of FOXP1 protein and we assume that the increased activity of FOXP1 proto-oncogene contributes to the histological transformation of FL.