Abstract 3321: Dysregulation of m6A RNA methylation regulators in colorectal cancer: Clinical implication as prognostic biomarkers and potential therapeutic targets
Authors: Kandimalla Raju , Gao Feng , Ruan Chun , Hsieh Michael , Wang Xin , Goel Ajay 
Published: August 2018

Purpose Among more than 100 known post-transcriptional modifications, N6-Methyladenosine (m6A) represents the most prevalent internal modification in mammalian mRNAs. This epigenomic modification is orchestrated by a distinct group of enzymes and cofactors, categorized as writers, erasers and readers. Writers consist of a multicomponent complex consisting of at least three proteins, namely methyltransferase-like 3 (METTL3), METTL14, and Wilms' tumor 1-associating protein (WTAP1). These m6A marks are erased by two RNA demethylases, fat mass and obesity-associated protein (FTO) and alkylated DNA repair protein alkB homolog 5 (ALKBH5). Lastly, YTHDF1/2/3 family genes constitute the ‘readers' that preferentially bind to RNA harboring m6A modification. Accumulating evidence suggests that m6a RNA methylation plays a crucial role in cancer progression. Herein, we for the first time elucidate the role of m6a regulators in colorectal cancer (CRC), in order to gain insights into their functional role and potential clinical significance in this malignancy. Experimental design Two large independent publicly available genome-wide mRNA expression datasets (N=509, TCGA and N=566, CIT) were used to study the expression of m6a RNA methylation regulators and their association with prognosis and gene expression based Consensus Molecular Subtypes (CMS) in CRC. Furthermore, we studied the tumorigenic properties of the RNA demethylase, FTO, by knockdown and overexpression strategies in CRC cells. Results The risk-score derived from a seven gene mRNA expression classifier consisting of METTL3, METTL14, WTAP, YTHDF1, YTHDF2, FTO and ALKBH5 was associated with poor disease-free survival in the training (TCGA) and validation (CIT) cohorts, with corresponding hazard ratios of 1.90 (95% CI: 1.24-2.92, p&lt;0.002) and 1.86 (95% CI: 1.25-2.78, p&lt;0.001) respectively. Furthermore, a high-m6a risk-score was significantly associated with a mesenchymal, CMS4 subtype, with FTO being the most overexpressed gene in CMS4 subtype of CRCs. Functionally, knockdown of the FTO gene in CMS4 cell lines (MDST8 and NCIH716) dramatically inhibited cellular proliferation, invasion and colony formation abilities. In contrast, overexpression of FTO in RKO cells resulted in enhanced proliferation, invasion and colony formation. Conclusions In summary, we for the first time report the dysregulation of m6a RNA methylation regulators in CRC, wherein we discovered their significant association with poor prognosis and a CMS4 CRC subtype, as well as elucidated the functional role of FTO in CRC cell lines. Besides the potential of utilizing this seven gene m6a regulator gene expression classifier to predict prognosis, our data suggest that targeting FTO might represent an attractive strategy for therapeutic intervention in patients with a mesenchymal CRC subtype with poor prognosis.

Citation Format: Raju Kandimalla, Feng Gao, Chun Ruan, Michael Hsieh, Xin Wang, Ajay Goel. Dysregulation of m6A RNA methylation regulators in colorectal cancer: Clinical implication as prognostic biomarkers and potential therapeutic targets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3321.