N‑methyladenosine reader YTHDF2‑mediated AC026691.1 degradation promotes gastric cancer cell proliferation, migration and M2 macrophage polarization

The present study aimed to explore the effects of key N6‑methyladenosine (m6A)‑related long non‑coding RNAs (lncRNAs) on the malignant behavior and macrophage polarization of gastric cancer cells, and their preliminary mechanisms. Gastric cancer‑related lncRNA datasets were downloaded from The Cancer Genome Atlas database, and m6A‑related differentially expressed lncRNAs (DElncRNAs) were analyzed. Subsequently, Cox regression and lasso regression analyses were used to screen the m6A‑related DElncRNAs associated with the prognosis of patients with gastric cancer. Additionally, reverse transcription‑quantitative polymerase chain reaction (qPCR) was employed to detect the expression levels of m6A‑related lncRNAs in normal gastric epithelial cells (GES‑1) and human gastric cancer cells (AGS and MKN‑45). In addition, the methylation levels of lncRNAs were measured using a methylated RNA immunoprecipitation qPCR assay kit, and the interaction between m6A‑related lncRNAs and m6A‑related proteins was observed by RNA pull‑down assay. Subsequently, m6A‑related lncRNAs and proteins were knocked down separately or simultaneously in gastric cancer cell lines. Bioinformatics analysis revealed that m6A‑related AC026691.1 was significantly associated with the prognosis of patients with gastric cancer and had a potential binding site for YT521‑B homology domain family member 2 (YTHDF2). The RNA pull‑down assay indicated that YTHDF2 not only had binding sites with AC026691.1 but could also markedly promote the degradation of m6A‑related AC026691.1. Furthermore, AC026691.1 was lowly expressed in gastric cancer cells, whereas YTHDF2 was highly expressed. Knockdown of YTHDF2 inhibited the proliferation, migration and epithelial‑mesenchymal transition of gastric cancer cells, and reduced M2 macrophage polarization. By contrast, knocking down AC026691.1 showed the opposite trend. Knockdown of YTHDF2 and AC026691.1 further confirmed the stable impact of YTHDF2 on AC026691.1. In conclusion, the degradation of AC026691.1 modified by YTHDF2‑mediated m6A may promote gastric cancer cell proliferation, migration, epithelial‑mesenchymal transition and M2 macrophage polarization.