Abstract 2530: Validation and pathway analysis of a metastasis-specific microRNA signature in primary colon cancer
Authors: Braak Robert R. Coebergh van den , Sieuwerts Anieta M. , Lalmahomed Zarina S. , Smid Marcel , Weerd Vanja de , Daane Michelle van der Vlugt - , Galen Anne van , Xiang Shanshan , Biermann Katharina , Foekens John A. , Martens John W. , IJzermans Jan N. 
Published: July 2017

Abstract
Introduction: In lymph node negative (LNN) colon cancer 20% of the patients develops disease recurrence. Identification of these patients is needed. MicroRNAs (MiRNAs), a group of short non-coding RNAs, can function as tumor suppressors or oncogenes. Hur et al recently found 6 differentially expressed MiRNAs when comparing primary colorectal cancer and matched liver metastasis (MiR-320, MiR-221, MiR-30b, MiR-10b, MiR-885-5p, Let-7i). The expression of 2 MiRNAs was significantly correlated with distant metastasis (low Let-7i expression and high MiR-10b) in primary colorectal cancers. When split at the median and combined into a signature (Let-7i high and MiR-10b low [n=22] vs. Let-7i low and/or MiR-10b high[n=122]), the first group showed 100% metastasis free survival (MFS). We assessed the prognostic value of these MiRNAs and the signature in a clinically well-defined cohort of primary colon cancers.
Methods: Expression of the 6 MiRNAs were measured using RT-qPCR in a cohort of 232 colon cancer patients (n=155 untreated LNN and n=77 adjuvant treated lymph node positive [LNP] patients) selected from the MATCH-cohort. Expression levels were related to microsatellite instability (MSI), and MFS, hepatic metastasis free (HFS) and overall survival (OS).
Results: MiR-221, Mir-30b, Mir-10b and MiR-885-5p levels were significantly associated with MSI. In univariate Cox regression analysis, MiR-30b was significantly associated with MFS (HR=1.23 p=0.004), and MiR-30b and Let-7i were associated with HFS (HR=2.52 p=0.005 and HR=0.40 p&lt;0.001, respectively) in the total group. In the LNN group results were similar for MiR-30b (MFS HR=2.07 p=0.008 and HFS HR=2.94 p=0.005) and Let-7i (HFS HR=0.28 p&lt;0.001), but did not reach significance in the LNP group. These associations remained significant when correcting for MSI. Pathway analysis for MiR-30b and Let-7i with the GSEA hallmark gene sets between the 50 samples with the highest and 50 samples with lowest expression revealed a significantly higher expression of the TGF-beta pathway in the MiR-30b high group, and a significantly higher expression of the EMT pathway in the Let-7i high group. MiR-30b and Let-7i expression was split at the median level and combined into two groups (‘Let-7i high and MiR-30b low’ vs. ‘Let-7i low and/or MiR-30b high’). The ‘Let-7i high and MiR-30b low’ group in the total group (n=74) had a significantly better 5-yr HFS (100% vs 87.4% p=0.002), and had a significantly better 5-yr MFS (91.7% vs 78% p=0.036) and HFS (100% vs 87.8% p=0.01) in the LNN group (n=52).
Conclusion: in our cohort and more specifically the LNN group, we confirmed Let-7i and identified MiR-30b as a prognostic factor for MFS and HFS. We did not confirm the prognostic value of Mir-10b. The combination of Let-7i and MiR-30b identified a group with a 100% HFS. Pathway analysis showed higher expression of the TGF-beta pathway in the MiR-30b high group, and higher expression of the EMT pathway in the Let-7i high group.
Citation Format: Robert R. Coebergh van den Braak, Anieta M. Sieuwerts, Zarina S. Lalmahomed, Marcel Smid, Vanja de Weerd, Michelle van der Vlugt - Daane, Anne van Galen, Shanshan Xiang, Katharina Biermann, John A. Foekens, John W. Martens, Jan N. IJzermans. Validation and pathway analysis of a metastasis-specific microRNA signature in primary colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2530. doi:10.1158/1538-7445.AM2017-2530