Abstract LB-296: Small RNA profiling of human testicular germ cell tumor tissue samples shows abundant tRNA fragments and global loss of piRNA

Abstract

Abstract Small non-coding RNAs play essential roles in tumorigenesis. However, their role in testicular germ cell tumor (TGCT), the most common malignancy in young males in most western countries, is largely unknown. In particular, a comprehensive analysis of the small RNA composition, including microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), and tRNA-derived small RNAs and their interactions, are lacking. tRNA-derived small RNAs have been shown to bind to the piRNA-associated protein HIWI2, indicating crosstalk between small RNA pathways. We have employed small RNA sequencing on 22 human TGCT samples from 5 histological subtypes, 3 carcinoma in situ, and 12 normal testis samples. The sequences from each sample group were analyzed according to sequence length, base composition, and their association with repeats, exons, tRNAs, piRNAs, and miRNAs. Most sequences 24-32 nucleotides in length, displayed piRNA characteristics. Expression analyses of the small RNA contigs demonstrated global loss of small RNAs in TGCT compared to normal testis. A large proportion of the 33-36 nt RNA sequences derives from mature tRNAs, predominantly from the 5′ end. We did not identify differences in the expression of 5′ tRNA halves between normal and cancer tissue samples; however, 3 shorter 5′ tRNA fragments showed differential expression. Although components of the same pathways might be involved in piRNA and tRNA-derived small RNAs biogenesis, expression differences in TGCT samples suggest independent regulation of key components in response to the carcinogenic process. Our results show subtype-specific microRNA expression, as well as a global loss of piRNAs in all TGCT histological subtypes when compared to normal testicular tissue. In addition, we document the presence of large amounts of tRNA-derived sequences in both TGCT and normal samples, which may provide new insight into the association between the tRNA fragments and piRNA biogenesis. These results may be valuable in the identification of new biomarkers for TGCT. Citation Format: Trine B. Rounge, Kari Furu, Rolf Skotheim, Trine B. Haugen, Espen Enerly, Tom Grotmol. Small RNA profiling of human testicular germ cell tumor tissue samples shows abundant tRNA fragments and global loss of piRNA. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-296. doi:10.1158/1538-7445.AM2015-LB-296