Introduction
One of the most common malignancies in the world is gastric cancer (GC). According to statistics, more than 1 million individuals are diagnosed with stomach cancer each year, accounting for 5.7 percent of all cancer diagnoses, and around 700,000 people die from it each year ( Ye et al., 2021 ; Wong et al., 2021 ). GC, which is produced by malignant alterations in gastric gland cells and accounts for 90 percent to 95 percent of GC ( Zhang et al., 2020 ), is the most frequent pathological form of GC. Despite the fact that the prognosis for GC has improved as a result of the advancement of numerous therapeutic options, including as surgery, chemotherapy, radiation and targeted therapy, the patients’ 5-year overall survival rate is still dismal ( Qiu et al., 2020 ). As a result, it is critical to thoroughly comprehend GC’s molecular process and to investigate novel and dependable prognostic indicators.

In RNA, more than 160 chemical changes have been found ( Zhang et al., 2021 ), and the m6A (N6 methyladenine) change in eukaryotic mRNA and lncRNA was detected as early as the 1970s, showing that methylation of RNA is a post-translational regulation mechanism ( Zhou et al., 2020 ). The most frequent methylation modification of mRNA in eukaryotic cells is m6A, which has an impact on all phases of the RNA life cycle ( Roundtree et al., 2017a ). M6A RNA affects splicing ( Tang et al., 2018 ; Yao et al., 2021 ), export ( Roundtree et al., 2017b ), stability and translation of mRNA posttranscriptionally ( Huang et al., 2018 ). Five-methylcytosine (m5C) is found in the mRNA transcript’s untranslated region (UTR), and it has been linked to a variety of gene expression activities such as RNA export, ribosome assembly and translation ( Pan, Huang & Xu, 2021 ). N1-methyladenosine (m1A), a critical posttranscriptional alteration in RNA, was discovered more than five decades ago and has now acquired general acceptance ( Zhao et al., 2019 ). The majority of m1A is found at the translation initiation site of mRNA, which is close to the translation start point of mRNA ( Gao et al., 2021 ). M7G controls mRNA export, translation and splicing by being located at the caps of mRNAs, as well as at particular internal sites in tRNAs and rRNAs ( Pandolfini et al., 2019 ; Zhang et al., 2019 ).

RNA methylation-related proteins include methyltransferase (Writer), demethylase (Eraser), and RNA methylation-specific recognition protein (Reader) ( Zhou et al., 2020 ). RNA methylation-related proteins have been shown to reversibly govern essential biological activities as RNA metabolism, processing and stem cell directed differentiation ( Zhao et al., 2014 ). In recent years, RNA methylation has been linked to tumor genesis, progression and metastasis. For example, According to one study, DNMT1-mediated FOXO3a promoter hypermethylation reduces FOXO3a expression in breast cancer, and FOXO3a decreases breast cancer stem cell characteristics and tumorigenicity through lowering FOXM1/SOX2 signaling ( Liu et al., 2020 ). The RNA-binding protein ALYREF binds to the m5C gene. PKM2 and ALYREF levels have been associated to poor outcomes in bladder cancer patients, suggesting that ALYREF and its target gene PKM2 might be helpful biomarkers for guiding early bladder cancer diagnosis ( Wang et al., 2021 ). WDR4 levels are linked to cancer immunity and may be used as a prognostic biomarker for some cancers ( Zeng et al., 2021 ). However, RNA methylation in GC is infrequently examined, and the overall prediction level in GC is insufficient.

We investigated the expression of RNA methylation regulators in STAD using the The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets, and for the first time looked at the relationship between RNA methylation-related prognostic genes and clinicopathological features. To demonstrate the predictive usefulness of prognostic genes related with RNA methylation for Stomach adenocarcinoma (STAD), we created several tumor subgroup models and risk models. It was also highlighted how these differentially expressed genes relate to cell signaling pathways and the tumor immunological microenvironment.