Gene Polymorphisms of m6A Erasers FTO and ALKBH1 Associated with Susceptibility to Gastric Cancer

The biological function of demethylase ALKBH1 and its role in human diseases

AlkB homolog 1 (ALKBH1) is a member of the AlkB family of dioxygenases that are dependent on Fe(II) and α-ketoglutarate. Mounting evidence demonstrates that ALKBH1 exhibits enzymatic activity against various substrates, including N6-methyladenosine (m6A), N1-methyladenosine (m1A), N3-methylcytidine (m3C), 5-methylcytosine (m5C), N6-methyladenine (N6-mA, 6mA), and H2A, indicating its dual roles in different biological processes and involvement in human diseases. Up to the present, there is ongoing debate regarding ALKBH1's enzymatic activity. In this review, we present a comprehensive summary of recent research on ALKBH1, including its substrate diversity and pathological roles in a wide range of human disorders, the underlying mechanisms of its functions, and its dysregulation. We also explored the potential of ALKBH1 as a prognostic target.

The regulatory mechanism of m6A modification in gastric cancer

To the best of our knowledge, N6-Methyladenosine (m6A) exerts a significant role in the occurrence and development of various tumors. Gastric cancer (GC), originating from the mucosal epithelium in the digestive tract, is the fifth most common cancer and the third most common cause of cancer death around the world. Therefore, it is urgent to explore the specific mechanism of tumorigenesis of GC. As we all know, m6A modification as the most common RNA modification, is involved in the modification of mRNA and ncRNA at the post-transcriptional level, which played a regulatory role in various biological processes. As identified by numerous studies, the m6A modification are able to influence the proliferation, apoptosis, migration, and invasion of GC. What's more, m6A modification are associated with EMT, drug resistance, and aerobic glycolysis in GC. m6A related-ncRNAs may be a valuable biomarker used by the prediction of GC diagnosis in the future. This review summarizes the role of m6A modification in the mechanism of gastric cancer, with the aim of identifying biological progress.

Epigenetic targeting of autophagy for cancer: DNA and RNA methylation

Autophagy, a crucial cellular mechanism responsible for degradation and recycling of intracellular components, is modulated by an intricate network of molecular signals. Its paradoxical involvement in oncogenesis, acting as both a tumor suppressor and promoter, has been underscored in recent studies. Central to this regulatory network are the epigenetic modifications of DNA and RNA methylation, notably the presence of N6-methyldeoxyadenosine (6mA) in genomic DNA and N6-methyladenosine (m6A) in eukaryotic mRNA. The 6mA modification in genomic DNA adds an extra dimension of epigenetic regulation, potentially impacting the transcriptional dynamics of genes linked to autophagy and, especially, cancer. Conversely, m6A modification, governed by methyltransferases and demethylases, influences mRNA stability, processing, and translation, affecting genes central to autophagic pathways. As we delve deeper into the complexities of autophagy regulation, the importance of these methylation modifications grows more evident. The interplay of 6mA, m6A, and autophagy points to a layered regulatory mechanism, illuminating cellular reactions to a range of conditions. This review delves into the nexus between DNA 6mA and RNA m6A methylation and their influence on autophagy in cancer contexts. By closely examining these epigenetic markers, we underscore their promise as therapeutic avenues, suggesting novel approaches for cancer intervention through autophagy modulation.

Implication of KDR Polymorphism rs2071559 on Therapeutic Outcomes and Safety of Postoperative Patients with Gastric Cancer Who Received S-1-Based Adjuvant Chemotherapy: A Real-World Exploratory Study

Objective

Regimens of S-1-based adjuvant chemotherapy are of great significance in attenuating recurrence risk in postoperative patients with gastric cancer (GC). Kinase insert-domain receptor (KDR) gene plays an essential role in tumor growth and metastasis. This study aimed to investigate the implication of KDR genotyping on the therapeutic outcomes of patients with gastric cancer (GC) who received S-1-based adjuvant chemotherapy.

Methods

A total of 169 postoperative GC with pathological staging of II and III and no metastasis who received S-1-based adjuvant chemotherapy were included retrospectively. Peripheral blood specimens were collected and prepared for KDR genotyping and KDR mRNA expression. Correlation between KDR genotype status and prognosis was performed using Kaplan-Meier survival analysis, and multivariate analysis was ultimately adopted using Cox regression analysis.

Results

Median disease-free survival (DFS) of the 169 patients with GC was 5.1 years [95% confidence interval (CI): 4.25-5.95] and median overall survival (OS) was 6.7 years (95% CI: 5.44-7.96). Rs2071559 was located at the upstream region, and the prevalence among 169 patients with GC was as follows: AA genotype in 104 cases (61.5%), AG genotype in 57 cases (33.7%), and GG genotype in 8 cases (4.7%), yielding a minor allele frequency of 0.22, which was consistent with Hardy-Weinberg equilibrium (P=0.958). Median DFS of patients with AA and AG/GG genotypes was 6.0 years and 4.0 years, respectively (P=0.002). Additionally, patients with the AA genotype had longer OS than those with the AG/GG genotype [median OS: not reached (NR) vs 5.5 years, P=0.011]. Additionally, KDR mRNA expression was significantly higher in patients with the AG/GG genotype than that in those with the AA genotype (P<0.001).

Conclusion

Rs2071559 in KDR gene might be a promising biomarker for evaluating the recurrence risk and OS of patients with GC who received S-1-based adjuvant chemotherapy. This conclusion should be confirmed in randomized clinical trials.

Impact of m6A demethylase (ALKBH5, FTO) genetic polymorphism and expression levels on the development of pulmonary tuberculosis

Objective

The m6A methylation was involved in the pathogenesis of pulmonary tuberculosis (PTB), and our study aimed to reveal the potential association of m6A demethylase (ALKBH5, FTO) genes variation, expression levels and PTB.

Methods

Eight SNPs (ALKBH5 gene rs8400, rs9913266, rs12936694, rs4925144 and FTO gene rs6499640, rs8047395, rs1121980, rs9939609) were selected for genotyping by SNPscan technique in 449 PTB patients and 463 healthy controls.

Results

The mRNA expression levels of ALKBH5, FTO were detected by qRT-PCR. There were no significant differences in genotype, allele distributions of all SNPs between PTB patients and healthy controls. Haplotype analysis demonstrated that the frequency of FTO gene GAAA haplotype was significantly reduced in PTB patients when compared to controls. ALKBH5 rs8400 AA genotype, A allele frequencies were associated with the decreased risk of sputum smear-positive, while AA genotype frequency was related to the increased risk of hypoproteinemia in PTB patients. In addition, rs9913266 variant was linked to the occurrence of drug-induced liver injury, sputum smear-positive, and rs4925144 variant was associated with leukopenia among PTB patients. In FTO gene, rs8047395 GG genotype and G allele frequencies were significantly higher in the PTB patients with drug resistance than that in the PTB patients without drug resistance. The ALKBH5, FTO expression levels were significantly decreased in PTB patients in comparison to controls. Moreover, ALKBH5 level was increased in PTB patients with drug resistance, and FTO level was decreased in PTB patients with sputum smear-positive.

Conclusion

FTO gene polymorphisms might be associated with PTB susceptibility, and ALKBH5, FTO levels were decreased in PTB patients, suggesting that these m6A demethylase played important roles in PTB.