Tsuboi M, et al. - Considering their previous genome-wide screening revealing hypermethylated CpG islands around glutamate decarboxylase 1 (GAD1) in lung adenocarcinoma (LADC), researchers examined the methylation and expression status of GAD1 and its prognostic value in patients with LADC. they analyzed GAD1 methylation and mRNA expression status using 33 tumorous and paired non-tumorous LADC samples and publicly available datasets. LADC tumors vs paired non-tumorous tissues had significantly higher methylation and mRNA expression levels of GAD1. As per the multivariate analysis, there was an independent prognostic value of GAD1 protein overexpression for disease-free survival. Higher GAD1 mRNA expression in LADC patients was noted to be significantly correlated with a poorer prognosis for overall survival in publicly available datasets. The pathological stage, pleural invasion, lymph vessel invasion, and poorer prognosis for cancer-specific and disease-free survival were noted to be significantly correlated with higher immunoreactivity of GAD1. These findings support the utility of GAD1 mRNA and protein expression levels as biomarkers to stratify patients with worse clinical outcomes after resection.