Prevalence of Molecular Subtypes of Gastric Cancer in Taiwan and the Impact of High SLC25A22 Expression on Survival: A Single‐Center Experience

ABSTRACT SLC25A22 is a mitochondrial inner membrane glutamate transporter responsible for shuttling glutamate from the cytoplasm into the mitochondrial matrix. Its clinical significance in gastric cancer (GC) remains unclear. GC can be classified into four molecular subtypes: Epstein‐Barr virus (EBV)‐associated, microsatellite instability (MSI), genomic stability (GS), and chromosomal instability (CIN). In this study, we evaluated the distribution of GC molecular subtypes in Taiwan and examined the association between SLC25A22 expression and patient outcomes. A total of 235 patients with gastric adenocarcinoma treated at Changhua Christian Hospital were included. Tumor subtypes were determined using immunohistochemistry and Epstein‐Barr encoding region (EBER) in situ hybridization according to established criteria, and SLC25A22 expression was assessed using an immunohistochemical scoring system. The prevalence of EBV‐associated tumors, MMR deficiency (MSI subtype), CIN, and other subtypes was 8.1%, 6.8%, 70.2%, and 14.9%, respectively. EBV‐associated tumors showed a relatively lower incidence of metastatic disease ( p = 0.014). The median SLC25A22 expression scores were 85 in EBV‐associated tumors, 90 in MMR‐deficient tumors, 90 in CIN tumors, and 100 in other subtypes. Higher SLC25A22 expression (score > 90) was associated with poorer prognosis ( p = 0.014). Our findings indicate that the MSI subtype of GC has a relatively low prevalence in Taiwan and suggest that elevated SLC25A22 expression may serve as a potential biomarker associated with unfavorable prognosis in gastric cancer. Further studies are needed to clarify the biological role of SLC25A22 in tumor progression and therapeutic resistance.