LINC00261 Suppresses Epithelial-Mesenchymal Transition and Metastatic Potential of Colorectal Cancer by Down-regulating the MeCP2-ZEB1 Feedback Loop

Accumulating evidence suggests that epithelial-mesenchymal transition (EMT) contributes to metastasis, a major cause of death in patients with colorectal cancer (CRC). MeCP2 (methyl CpG binding protein 2), a key modulator for initiating gene transcription, plays a pivotal role in EMT, but its upstream signaling pathways are poorly understood. We collected 137 colorectal cancer patients’ samples, including tumor tissues (n=137), adjacent normal tissues (n=137) and liver metastases (n=11). Three pairs of colorectal cancer cell lines were sequenced to identify high abundance of lincRNAs in primary tumor tissues. Two independent experiments (electrophoretic mobility shift assay and RNA immunoprecipitation assay) were used to characterize the interaction between LINC00261 and MeCP2. Subsequently, the effects of LINC00261 on phosphorylation of MeCP2 and promotion of the MeCP2-ZEB1 feedback were examined. Consequently long intergenic non-protein coding RNA 261 (LINC00261) was down-regulated in highly metastatic CRC cells and liver metastases from patients with CRC. Down-regulating LINC00261 promoted the expression of EMT markers and increased the invasive and migratory properties of multiple CRC cell lines. Furthermore, knocking down LINC00261 increased colon-derived liver metastasis in an orthotopic CRC model and promoted distant metastatic colonization in a lung metastasis model. Mechanistic studies revealed that LINC00261 interacted with MeCP2 and stabilized it in the nucleus by inhibiting Ser80 phosphorylation Interestingly, ZEB1 could re-modulate MeCP2 expression by binding to the MeCP2 promoter, and they formed a positive feedback loop consequently. In contrast, the lower LINC00261 expression in CRC samples correlated with reduced E-cadherin and membrane β-catenin levels, and was associated with shorter overall survival. Taken together, LINC00261 suppresses EMT and CRC cells’ metastatic potential by negatively regulating the MeCP2-ZEB1 feedback loop; LINC00261’s loss in metastatic tissues may be a potential prognostic marker of aggressive disease.