The ELF3-regulated lncRNA UBE2CP3 is over-stabilized by RNA–RNA interactions and drives gastric cancer metastasis via miR-138-5p/ITGA2 axis

LncRNAs play essential roles in tumorigenesis and tumor progression. Pseudogene UBE2CP3 is an antisense intronic lncRNA. However, the biological function of UBE2CP3 in gastric cancer (GC) remains unknown. In this study, we revealed that lncRNA UBE2CP3 was aberrantly upregulated in multiple independent gastric cancer cohorts, and its overexpression was clinically associated with poor prognosis in GC. UBE2CP3 was mainly located in cytoplasm and promoted migratory and invasive capacities of GC cells in vitro and in vivo. Mechanismly, a novel dysregulated ceRNA network UB2CP3/miR-138-5p/ITGA2 was identified in GC by transcriptome sequencing. Furthermore, rescue assay further confirmed that UBE2CP3 mainly promoted GC progression through miR-138-5p/ITGA2 axis. More importantly, our data proved that UBE2CP3/IGFBP7 could form an RNA duplex, thereby directly interacting with the ILF3 protein. In turn, this RNA-RNA interaction between IGFBP7 mRNA and UBE2CP3 mediated by ILF3 protein plays an essential role in protecting the mRNA stability of UBE2CP3. In addition, transcription factor ELF3 was identified to be a direct repressor of lncRNA UBE2CP3 in GC. Taken together, overexpression of UBE2CP3 promotes tumor progression via cascade amplification of ITGA2 upregulation in GC. Our finding has revealed that the dysregulation of UBE2CP3 is probably due to the downregulation of ELF3 and/or the overexpression of IGFBP7 mRNA in GC. Our findings reveal, for the first time, that UBE2CP3 plays crucial a role in GC progression by modulating miR-138-5p/ITGA2 axis, suggesting that UBE2CP3 may serve as a potential therapeutic target in GC.