Abstract 4926: Clinical significance of SNORA21, an H/ACA box snoRNA, as a metastasis predicting and prognostic biomarker in colorectal cancer
Authors: Yoshida Kazuhiro , Toden Shusuke , Weng Wenhao , Nagasaka Takeshi , Fujiwara Toshiyoshi , Goel Ajay 
Published: July 2016

Background: Colorectal cancer (CRC) remains a prevalent malignancy worldwide with a high mortality rate. Over the last decade, the roles of several types of noncoding RNAs in oncogenesis have been clarified. Emerging evidence indicates that not only microRNAs, but small nucleolar RNAs (snoRNAs) appear to be dysregulated in various malignancies and they play a critical role in modulating cell transformation, tumor progression and metastasis. Functionally, cancer associated snoRNAs are subdivided into four major categories based on their oncogenic functions: 1) an independent function from imprinting gene in cancer initiation and progression 2) Activation of human telomerase 3) Inhibition of ribosomal maturation 4) Act directly as oncogene or tumor suppressor. Despite these exciting evidences, the role of snoRNAs in CRC remains limited and their clinical significance remains largely unexplored in this malignancy.

Aims: We aimed to clarify the clinical relevance of snoRNAs in tumors and evaluate their prognostic potential in CRC. Furthermore, we investigated the functional role of snoRNAs in CRC tumorigenesis.

Methods: Initially, we screened for the most commonly differentially expressed snoRNAs from publicly available microarray and RNA-sequence databases for other malignancies. Three clinical cohorts (a total 345 CRC tissues) were then used to select/validate the candidate snoRNAs. The prognostic potential of the candidate snoRNAs were evaluated and the association with clinicopathological features were assessed. CRISPR/Cas9 system was used to knockdown the target snoRNA in multiple CRC cell lines to determine the functional role of the target snoRNA in a series of in vitro assays.

Results: In the discovery phase, we identified four differentially overexpressed snoRNAs in human cancers. We then confirmed overexpression of three snoRNAs (SNORA21, SNORA34 and SNORD66) in CRC compared to adjacent normal tissues. Of these three snoRNAs, high SNORA21 expression in tumors resulted in poor prognosis (p = 0.0086, Log-rank test). In an independent validation cohort, we confirmed high SNORA21 expression results in poor overall survival (p = 0.0060), especially in stage IV CRC (p = 0.0272). Clinicopathological analysis showed positive association between SNORA21 and vascular invasion and metastasis (p = 0.030 and 0.011, by Kruskal-Wallis test and Mann-Whitney U test, respectively) indicating that SNORA21 could be involved in metastasis. Moreover, multivariate analysis revealed that increased SNORA21 expression was an independent prognostic factor for overall survival. Using CRISPR/Cas9 stable SNORA21 knocked-down cell lines, we demonstrated that SNORA21 suppression resulted in reduced cell proliferation and colony forming capacity.

Conclusion: We firstly identified SNORA21 as a novel oncogene which could also be a potential prognostic marker in patients with CRC.

Citation Format: Kazuhiro Yoshida, Shusuke Toden, Wenhao Weng, Takeshi Nagasaka, Toshiyoshi Fujiwara, Ajay Goel. Clinical significance of SNORA21, an H/ACA box snoRNA, as a metastasis predicting and prognostic biomarker in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4926.