Upregulation of Long Noncoding RNA MALAT1 in Colorectal Cancer Promotes Radioresistance and Aggressive Malignance

Background: Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), a conserved transcript with 8000 nt, is highly associated with malignancy of numerous cancer types. However, the function of MALAT1 plays in regulating the response to radiotherapy in colorectal cancer (CRC) remains unclear. Thus, the object of this study is to investigate the functions of MALAT1 in CRC radioresistance. Methods: First, the expression of MALAT1 in colon adenocarcinoma (COAD) was analyzed through the Cancer Genome Atlas (TCGA) database. Then, we detected the expression level of MALAT1 in tumor tissues and CRC cell lines and analyzed the relevance of MALAT1 and clinicopathological parameters. In the end, the effect of silencing MALAT1 on the radiosensitivity of CRC cells was investigated, and its potential mechanism was preliminarily illustrated. Results: The analysis of TCGA data showed that MALAT1 was closely related to the type of tumor, and high expression of MALAT1 was remarkably relevant to poor outcome. MALAT1 was highly expressed in CRC tissues and cell lines and related to tumor stages. Knockdown of MALAT1 could significantly suppress colony survival, proliferation, and migration and increase apoptosis, G2/M phase arrest, and formation of gamma-H2AX foci in HCT116, whether in combination with X-rays or not. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that the regulated proteins were principally enriched in the glycosaminoglycan degradation pathway after silencing MALAT1. Conclusion: Our results implied that MALAT1 was highly expressed in CRC and associated with tumor stage and prognosis. Silencing MALAT1 can increase HCT116 cell radiosensitivity, which may be potentially influenced by glycosaminoglycan degrada-tion pathway.