Abstract 2394: tRNA expression and tRFs in multiple myeloma: Progression from monoclonal gammopathies to relapsed/refractory disease
Authors: Rojek Alexandra E. , Katanski Christopher D. , Stefka Andrew , Derman Benjamin A. , Jakubowiak Andrzej , Pan Tao 
Published: July 2021

Abstract
Introduction : tRNA-derived fragments (tRFs) have been postulated to play a significant role in human disease and specifically cancer. tRFs can function as small non-coding RNAs, expressed more highly in conditions of oxidative stress and tissue damage, and are postulated to have a regulatory function. Previous work has identified overexpression of tRNAs in multiple myeloma (MM), but the expression of tRFs in MM has not yet been characterized. In this descriptive study, we set out to apply modern next-generation sequencing tools to describe tRNA and tRF expression in MM.
Methods: Bone marrow aspirate samples from 24 patients, 8 with monoclonal gammopathy of undetermined significance (MGUS) or smoldering MM (SMM), 8 with newly diagnosed MM (NDMM), and 8 with relapsed/refractory MM (RRMM) were selected. Total RNA fraction from mononuclear cell fractions was extracted and used to prepare tRNA sequencing libraries which generated data of different small RNA families such as tRNA, tRF, and 5S rRNA in one library.
Results: We found a trend toward increased total expression of tRFs in NDMM and RRMM patient samples. Analysis of specific classes of tRFs revealed differential expression along the course of disease progression, with specific tRFs increasing in expression from MGUS/SMM to RRMM. Specifically, tRFs from tRNAHis showed a significant increase in expression from MGUS/SMM to NDMM (p&lt;0.01) and from MGUS/SMM to RRMM (p&lt;0.01). Other tRFs also showed increased abundance from MGUS/SMM to RRMM, such as tRNALeu (p=0.04), tRNAPhe (p=0.07), and tRNAVal (p=0.08). Comparing the proportion of tRNA reads that originated from full length tRNAs compared to fragments between patient groups, we further observed decreases in the proportion of full length reads from MGUS/SMM to RRMM for tRNAPro (p&lt;0.05), tRNALeu (p=0.05), tRNAVal (p=0.05), tRNAHis (p=0.08), and tRNAPhe (p=0.06). Fragmentation proportions were distinct among tRNAs which decode different codons for the same amino acid (isoacceptors) suggesting that fragmentation is specific, and not a result of widespread RNase cleavage. Furthermore, fragments predominantly originated from cleavage within the anticodon loop of their cognate tRNA, consistent with known tRF biogenesis pathways.
Conclusions : These preliminary results indicate that tRNA fragment expression has the potential to serve as an objective, quantitative measure of clinical MM progression. While the function of these small RNA species remains unclear, specific cleavage patterns suggest that tRF expression in MM may be regulated during disease progression. Future work should explore potential for miRNA-like function of tRFs in MM, and ongoing work to be presented at the meeting will further explore tRF abundance as well as post-transcriptional modifications of tRNAs which may provide a mechanistic understanding of patterns of tRNA fragmentation.
Citation Format: Alexandra E. Rojek, Christopher D. Katanski, Andrew Stefka, Benjamin A. Derman, Andrzej Jakubowiak, Tao Pan. tRNA expression and tRFs in multiple myeloma: Progression from monoclonal gammopathies to relapsed/refractory disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2394.