Assessing the potential value of long interspersed element-1 hypomethylation in colorectal cancer: evidence from retrospective studies

BACKGROUND AND AIMS: Long interspersed element-1 (LINE-1) hypomethylation may play an important role in colorectal cancer (CRC). Studies were identified that investigated LINE-1 methylation levels in CRC compared with normal controls. METHODS: The random-effects model was used to estimate standardized mean difference with 95% confidence intervals according to the heterogeneity between the studies. We explored the relationship between LINE-1 hypomethylation and microsatellite instability (MSI) status, clinical features, and molecular features in CRC patients using a fixed-effects model. RESULTS: A total of 7396 CRC patients were included in the meta-analysis. LINE-1 methylation was significantly lower in CRC patients than in controls (P=0.000). Mean LINE-1 methylation was significantly lower in non-MSI-high than in MSI-high tumors (P=0.000). LINE-1 hypomethylation was found more frequently in patients with a family history compared with those without family history (P=0.002). Patients with left colon cancer had lower LINE-1 methylation than those with right colon cancer (P=0.001). LINE-1 methylation was not associated with body mass index or patient sex. LINE-1 hypomethylation was found in p21 lost tumors (P=0.000). LINE-1 methylation levels were not associated with KRAS or PIK3CA-mutation status. CONCLUSION: LINE-1 hypomethylation is a potential biomarker for risk of CRC and associated with various clinical and molecular features of CRC.