Potential Influence of ADAM9 Genetic Variants and Expression Levels on the EGFR Mutation Status and Disease Progression in Patients with Lung Adenocarcinoma

Lung adenocarcinoma (LUAD) is driven by epidermal growth factor receptor (EGFR) mutations, making it a key therapeutic target. ADAM9, a member of the A disintegrin and metalloproteinase (ADAM) family, facilitates the release of growth factors and was implicated in activating the EGFR-mediated progression in several cancer types. In this study, we explored potential associations among ADAM9 single-nucleotide polymorphisms (SNPs), the EGFR mutation status, and the clinicopathological progression of LUAD in a Taiwanese population. In total, 535 LUAD patients with various EGFR statuses were enrolled, and allelic distributions of ADAM9 SNPs—located in promoter and intron regions, including rs78451751 (T/C), rs6474526 (T/G), rs7006414 (T/C), and rs10105311 (C/T)—were analyzed using a TaqMan allelic discrimination assay. We found that LUAD patients with at least one polymorphic G allele in ADAM9 rs6474526 had a lower risk of developing EGFR mutations compared to those with the wild-type (WT) TT genotype. Furthermore, G-allele carriers (TG + GG) of rs6474526 were associated with an increased likelihood of developing larger tumors (T3 or T4), particularly among patients with mutant EGFR. Conversely, in patients with WT EGFR, carriers of the T allele in rs10105311 had a lower risk of progressing to advanced stages (stage III or IV). Among females or non-smokers, G-allele carriers of rs6474526 demonstrated a higher risk of advanced tumor stages and distant metastases. In clinical data from the Genotype-Tissue Expression (GTEx) database, individuals with the polymorphic T allele in rs6474526 showed reduced ADAM9 expression in lung and whole blood tissues. Screening the genotype of rs6474526 in a set of LUAD cell lines revealed that cells carrying at least one minor G allele exhibited higher ADAM9 levels compared to those with the TT genotype. Additionally, analyses using TCGA and CPTAC databases revealed elevated ADAM9 expression in LUAD specimens compared to normal tissues. Elevated protein levels were correlated with advanced T stages, pathological stages, and worse prognoses. In summary, our results suggest that ADAM9 genetic variants of rs6474526 may affect ADAM9 expression and are associated with the EGFR mutation status. Both rs6474526 and rs10105311 were correlated with disease progression in LUAD patients. These variants could serve as potential biomarkers for predicting clinical outcomes.