Circulating microRNAs and long non-coding RNAs in gastric cancer diagnosis: An update and review

Figure 1 Classification of RNA transcripts. UTR: Untranslated region; miRNA: MicroRNA.

Figure 2 Mechanisms of long non-coding RNA function. A: Serve as enhancer RNAs (eRNAs) to compete with nascent mRNA for negative elongation factor (NELF) complex binding at the target promoter for transcriptional regulation; B: Serve as a scaffolding base for the coordination of epigenetic or chromatin-modifying complexes; C: Serve as molecular sponges for microRNAs (miRNAs); D: Function as a decoy for miRNAs or translation factors to regulate gene expression; E: Hybridize with their corresponding spliced mRNAs to form dsRNAs, which are cleaved by Dicer to generate endogenous small interfering RNAs (endo-siRNAs) to modulate gene expression; F: Gene expression regulation by direct long non-coding RNA (lncRNA)-mRNA interactions; G: Directly modulate tumor suppressor signaling by either transcriptional regulation of tumor suppressor genes or mediation of tumor suppressor target gene activation.

Figure 3 Flow diagram and schematic summary of circulating miRNA and lncRNA analyses. miRNAs: MicroRNA; lncRNA: Long non-coding RNA; qRT-PCR: Real-time quantitive polymerase chain reaction.