High expression of lncRNA MALAT1 suggests a biomarker of poor prognosis in colorectal cancer.

Objective: This study sought to investigate the role of the long noncoding RNA MALAT1 in the prognosis of stage II/III colorectal cancer (CRC) patients.

Methods: The expression of MALAT1 was evaluated in cancer tissues from 146 stage II/III CRC patients undergoing radical resection and 23 paired normal colonic mucosa samples using quantitative real-time reverse transcriptase PCR. Differences in the expression of MALAT1 between 23 CRC and paired normal colonic mucosa samples were analysed with the Wilcoxon test. Relationships between the expression level of MALAT1, patient clinicopathological parameters and disease-free survival (DFS) and overall survival (OS) were analysed using the univariate Kaplan-Meier method and the multivariate COX regression model.

Results: The MALAT1 levels in cancerous tissues were 2.26 times higher than those measured in noncancerous tissues, and this difference was statistically significant (P = 0.0004). Based on their expression level of MALAT1, the patients were divided into a high MALAT1 expression group (n = 73) and a low expression group (n = 73). Patients with tumours harbouring higher expression of MALAT1 showed a significantly worse prognosis with a hazard ratio (HR) of 2.863 (95% CI, 1.659 to 4.943; P < 0.001) for DFS and 3.968 (95% CI, 1.665 to 9.456; P = 0.002) for OS. Furthermore, patients with perineural invasion demonstrated significantly worse DFS (HR = 3.459, 95% CI 2.008 to 5.957; P < 0.001) and OS (HR = 3.750, 95% CI 1.743 to 8.069; P = 0.001) than those without perineural invasion. Multivariate analyses indicated that MALAT1 expression and perineural invasion were two independent prognostic risk factors for patients with CRC.

Conclusion: The expression of MALAT1 is upregulated in CRC tissues, and a higher expression level of MALAT1 might serve as a negative prognostic marker in stage II/III CRC patients.