P-059: miRNA profiling of CD138+ plasma cells identifies miR-181a-5p overexpression as independent predictor of short-term progression and poor treatment outcome in multiple myeloma

Background The considerable progress made in multiple myeloma (MM) treatment nowadays resulted in significantly prolonged survival. However, the high heterogeneity of patients’ response to treatment outlines the need for novel prognostic molecular markers able to support individualized treatment. microRNAs (miRNAs) have emerged as powerful post-transcriptional regulators of gene expression with a crucial role in cancer, while recent advances in high-throughput techniques have unveiled their prognostic utility. Herein, using a miRNA-seq approach we investigated miRNA profiles in association with MM and its precursor states, aiming to reveal potential MM-related miRNAs able to improve patients’ risk stratification. Methods Bone marrow aspiration (BMA) samples were collected from 138 MM, 30 smoldering MM (sMM) and 25 monoclonal gammopathy of undetermined significance (MGUS) patients at diagnosis. Mononuclear cells were isolated using Ficoll-Paque, while CD138+ plasma cells were positively selected using magnetic beads with anti-CD138 mAbs. Next, miRNA-seq was performed in CD138+ plasma cells from MGUS (n=4), sMM (n=4) and MM (n=20) patients. Based on miRNA-seq, target prediction and Gene Ontology (GO) enrichment analysis, miR-181a-5p was further evaluated for the first time in CD138+ plasma cells from the total study population. Following RNA extraction and 3’-end polyadenylation, miR-181a-5p levels were quantified using RT-qPCR. Disease progression and patients’ death were assessed as clinical endpoint events. Internal validation was performed by bootstrap analysis, while decision curve analysis was utilized to evaluate clinical benefit. Kruykov et al. 2016 served as an external validation cohort (n=151). Results miRNA-seq revealed miR-181a-5p to be concurrently upregulated in MM vs. MGUS/sMM as well as R-ISS III vs. R-ISS I patients. Hematopoietic cell differentiation and apoptosis were significantly enriched following GO analysis. In our screening cohort, miR-181a-5p overexpression was associated with a significantly higher risk of short-term disease progression (HR=2.524; p=0.006) and poor overall survival following treatment (HR=2.629; p=0.027) of MM patients. Consistent with our results, Kryukov et al. validation cohort confirmed the inferior survival outcome of the MM patients with elevated miR-181a-5p levels. Finally, multivariate prognostic models incorporating miR-181a-5p with established disease markers, including R-ISS stage and high-risk cytogenetics offered superior risk-stratification specificity and clinical benefit in MM prognosis. More specifically, Kaplan-Meier analysis showed that the combination of R-ISS stage with miR-181a-5p overexpression could provide a better stratification of MM patients’ OS (p=0.001) as well as PFS (p=0.016). Conclusions We identified miR-181a-5p overexpression in CD138+ plasma cells as a powerful independent predictor of adverse disease outcome and higher risk for post-treatment progression.