Abstract 1143: Deep sequencing of microRNAs in canine diffuse large B-cell lymphoma

Abstract

Abstract Introduction: MicroRNAs (miRNAs) are small non-coding RNAs 18-24 nucleotides in length that regulate gene expression by targeting the 3’ untranslated region of mRNAs. MiRNAs are often dysregulated in cancer, suggesting they play a role in tumorigenesis. Canine diffuse large B-cell lymphoma (DLBCL) represents one of the most common spontaneously occurring canine cancers. The clinical presentation, histology and biology of canine DLBCL closely parallels the human counterpart of this disease. We hypothesize that canine DLBCL possess a unique miRNA expression signature and that differential microRNA expression contributes to chemoresistance and prognosis. In this study, we sought to determine which miRNAs are differentially expressed in chemotherapy-naïve and relapsed DLBCL and are associated with overall survival. Methods: Total RNA was isolated by the Trizol method from 48 primary DLBCL lymph node biopsies. 24 of these biopsies represented paired chemotherapy-naïve and relapsed DBCL lymph node biopsies from 12 individual dogs. Clinical follow-up data for dogs treated with CHOP-based protocols was available for 24 dogs. Fragmented libraries were prepared for sequencing from RNA from DLBCL lymph node biopsies. Small RNA sequencing was performed using the Applied Biosystems SOLiD 4 Sequencing system. Data alignment, parsing, and normalization were performed using miRBase V16. Genomic coordinates of miRNAs and isomiRNAs were based on C. familiaris CanFam2.0. Results: 41 of 48 samples passed quality control criteria for statistical analysis. Small RNA sequencing of canine DLBCL lymph nodes identified many non-canonical isomiRNAs. In some cases, isomiRNAs were expressed at higher levels than the canonical miRNA according to miRBase. The expression of specific miRNAs was significantly different in paired chemotherapy-naive and relapsed canine DLBCL lymph node biopsies. MiR-21, a miRNA with known importance in human tumorigenesis, was significantly overexpressed in relapsed DLBCL as compared to chemotherapy-naïve DLBCL (p<0.001). Overexpression of cfa-miR-204 in canine DLBCL was predictive of poor overall survival (p<0.008). Conclusion: Our findings suggest that overexpression of cfa-miR-21, contributes to tumor progression in chemotherapy resistant canine DLBCL. Small RNA sequencing revealed that overexpression of cfa-miR-204 in canine DLBCL negatively affects survival. Characterization of miRNA expression in canine DLBCL will facilitate our understanding the biology of this disease and has the potential to identify diagnostic/prognostic factors and targets for therapeutic intervention. Given the clinical and molecular similarities of human and dog lymphoma, this study highlights several miRNA alterations associated with canine lymphoma and suggests that prognostic indicators in dogs may lead to a greater understanding of the genetic events involved in DLBCL initiation and progression in both species. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1143. doi:10.1158/1538-7445.AM2011-1143