Abstract 2106: Comparing the methylation profiles between lung adenocarcinoma and squamous cell carcinoma

Abstract Background: Lung cancer is a leading cause of death. Despite advancements in early diagnosis and treatment, most patients are diagnosed at later stages, and the average 5-year survival rate is < 30%. Lung adenocarcinoma (LUAD) is the most common non-small cell lung cancer (NSCLC), representing about 40% of cases, followed by lung squamous cell carcinoma (LUSC) at 25%. The biological patterns and molecular characteristics of LUAD and LUSC exhibit differences. Changes in DNA methylation levels of various genes have been observed in lung cancer subtypes, yet research on differences in DNA methylation patterns between LUAD and LUSC is limited. Methods: The methylation microarray dataset (GSE39279, Illumina HumanMethylation450 BeadChip) from Gene Expression Omnibus at the National Center for Biotechnology Information was used. The dataset comprised 444 NSCLC samples derived from tumor tissues, of which 322 were LUAD and 122 were LUSC. We used the Champ (Chip Analysis Methylation Pipeline) package to identify differentially methylated probes (DMPs, Benjamini-Hochberg adjusted p-value < 0.05) and genes representing specific biological pathways between LUAD and LUSC. Singular Value Decomposition regression analysis was used to estimate the impact of age, sex, and smoking status and then adjusted for the covariates with p-values < 0.05. We used the eFORGE TF database to calculate the Find Individual Motif Occurrences (FIMO) p-values for the overlap with transcription factor binding sites. The Gene Expression Profiling Interactive Analysis database was used to measure the gene expression levels of LUAD and LUSC samples in the Genotype-Tissue Expression and the Cancer Genome Atlas Program portals. Results: In total, 223,007 DMPs were identified by comparing LUAD and LUAC, with 130,610 hypomethylated and 92,467 hypermethylated. Using the absolute difference of β values between groups ≥ 0.3, we identified 15 DMPs, 11 hypomethylated and four hypermethylated. The DMPs on promoter regions were all hypomethylated in LUSC compared to LUAD (cg00415665 and cg22997040 in ZHX2, cg27649037 in ST18, cg20691436 in CALML3, and cg24580076 in C7orf20). We also identified DMPs based on the importance scores (> 0.1) from a 5-fold cross-validation random forest analysis. The two DMPs in the ZHX2 gene had the highest importance scores (> 8.0). Among those, cg00415665 was covered by the Zfp161_secondary motif (FIMO p-value: < 10-5). The average expression level of ZHX2 in LUSC (transcripts per million, TPM=9.7) was higher than in LUAD (TPM=8.2). Conclusions: We characterized the methylation landscape of NSCLCs by histological subtypes and identified that the methylation pattern of cg00415665 in ZHX2, a tumor suppressor gene, was significantly associated with the histological subtype of NSCLC. Further investigation of these findings will provide additional insight into the biology and genetics of LUAD and LUSC. Citation Format: Hyeyeun Lim, Christopher I. Amos, Jinyoung Byun, Aaron P. Aaron. Comparing the methylation profiles between lung adenocarcinoma and squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2106.