The EGR1-mediated lncRNA TENM3-AS1 potentiates gastric cancer metastasis via reprogramming fatty acid metabolism.

[BACKGROUND] Long non-coding RNAs (lncRNAs) are essential modulators in tumor progression. While fatty acid (FA) metabolism can potentiate tumorigenesis, colonization, and metastasis, the roles of lncRNAs in reprograming FA metabolism and regulating gastric cancer (GC) metastasis remain elusive.

[METHODS] Whole RNA-sequencing and in silico analyses were conducted to identify clinically significant lncRNAs involved in GC metastasis. Among the identified lncRNAs, we focused on the novel lncRNA TENM3-AS1. RT-qPCR and FISH analyses revealed an increased expression of TENM3-AS1 in GC cell lines and patients. In vitro and in vivo functional experiments validated the effects of TENM3-AS1 to GC metastasis and the reprogramming of FA metabolism. ChIP, Biotinylated RNA pull-down, RIP, CHX-chase assay, ubiquitination assay, and RNA stabilization assay were employed to perceive the mechanisms underlying the effects of TENM3-AS1 in GC cells.

[RESULTS] TENM3-AS1 expression was significantly elevated in metastatic tumors and advanced primary tumors of GC patients. This increased expression was also associated with a worsened overall survival and progression-free survival. Functionally, TENM3-AS1 enhanced the migration and invasiveness of GC cells in vitro, promoted tumorigenesis and liver metastasis in vivo, and increased FA biosynthesis in GC cells. Mechanistically, our studies showed that the transcription factor EGR1 activated TENM3-AS1, which in turn upregulated the expression of FASN and hnRNPK. Furthermore, TENM3-AS1 interacted with and stabilized hnRNPK by increasing its deubiquitination. This interaction reprogrammed FA metabolism and promoted GC progression by increasing FASN mRNA stability through hnRNPK.

[CONCLUSIONS] In this study, by comparing lncRNA sequencing data from paired primary and peritoneal metastatic tumors and public transcriptome data from non-metastatic and metastatic samples, we clarified a novel lncRNA, TENM3-AS1. It was found that TENM3-AS1 was aberrantly activated in metastatic and advanced primary tumors, and was strongly correlated with a shorter survival in GC patients. Our study reveals the EGR1/TENM3-AS1/ hnRNPK/FASN axis as a novel curative target in metastatic GC.