Increasing evidence suggests long non-coding RNAs (lncRNAs) are frequently aberrantly expressed in cancers, however, few related lncRNA signatures have been established for prediction of cancer prognosis. We aimed to develop a lncRNA signature to improve prognosis prediction of colorectal cancer (CRC). Using a lncRNA-mining approach, we performed lncRNA expression profiling in large CRC cohorts from Gene Expression Ominus (GEO), including GSE39582 test series(N=436), internal validation series (N=117); and two independent validation series GSE14333 (N=197) and GSE17536(N=145). We established a set of six lncRNAs that were significantly correlated with the disease free survival (DFS) in the test series. Based on this six-lncRNA signature, the test series patients could be classified into high-risk and low-risk subgroups with significantly different DFS (HR=2.670; P<0.0001). The prognostic value of this six-lncRNA signature was confirmed in the internal validation series and another two independent CRC sets. Gene set enrichment analysis (GSEA) analysis suggested that risk score positively correlated with several cancer metastasis related pathways. Functional experiments demonstrated three dysregulated lncRNAs, AK123657, BX648207 and BX649059 were required for efficient invasion and proliferation suppression in CRC cell lines. Our results might provide an efficient classification tool for clinical prognosis evaluation of CRC.

The polycomb group protein enhancer of zeste homologue 2 (EZH2), which has histone methyltransferase (HMT) activity, is overexpressed in malignant tumours. However, the role of EZH2 in colorectal cancer (CRC) invasion is little known. Here we investigated the clinical significance, biological effects, and mechanisms of EZH2 signalling. Knockdown of EZH2 significantly reduced cell invasion and secretion of matrix metalloproteinases 2/9 (MMP2/9) in in vitro studies. Knockdown of EZH2 dramatically increased overall survival and decreased metastasis of lung in in vivo studies. Conversely, overexpression of EZH2 significantly increased lung metastasis and shortened overall survival when compared with control tumours. EZH2-induced CRC cell invasion may depend on down-regulation of vitamin D receptor (VDR), which is considered to be a marker of CRC invasion. EZH2 regulates the histone trimethylation of lysine 27 (H3K27me3) in the VDR promoter. Moreover, we found that STAT3 directly binds to the EZH2 promoter and regulates VDR down-regulation in CRC cells. Significant inverse correlations were observed between the expression of EZH2 and pSTAT3 and that of VDR in CRC tissues compared with normal tissue in patients. We show the role of EZH2 in CRC metastasis and identify VDR as a target gene of EZH2. EZH2 expression may be directly regulated by STAT3, and STAT3 may play an important role in EZH2-mediated VDR down-regulation in CRC. This pathway may provide potential targets in aggressive CRC.