Carcinoembryonic Antigen-Related Cell Adhesion Molecule 5 as a Biomarker for Predicting Response to Erlotinib and Gefitinib in Lung Adenocarcinoma: An Integrative Analysis of Transcriptomic Data of PC-9 and Drug-Resistant PC-9 Cell Lines

Erlotinib (ER) and gefitinib (GB) are frequently prescribed for patients with advanced lung adenocarcinoma (ADC). Although both ER and GB significantly extend median survival, several patients experience early disease relapse due to treatment resistance. This study aimed to identify common genes associated with acquired resistance to ER or GB. This integrative analysis of transcriptomic data identified differentially expressed genes by comparing sensitive PC-9 cells with ER-resistant (PC-9/ER) or GB-resistant (PC-9/GB) cell lines. A Venn diagram was used to identify common genes. Candidate genes were confirmed in our generated drug-resistant cell lines. After six months, the PC-9/ER and PC-9/GB cell lines exhibited 40.7-fold and 109.2-fold increases in resistance to ER and GB, respectively. Flow cytometric analysis demonstrated that both resistant cell lines were resistant to cell cycle arrest and apoptosis induced by ER or GB. Through integrated analysis, we found that two genes, KRT13 and CEACAM5, were up-regulated in both the PC-9/ER and PC-9/GB cell lines. The expression patterns of these two genes did not align with the transcriptome, with only CEACAM5 exhibiting consistent gene and protein expressions. Our findings indicate that CEACAM5 serves as a biomarker for predicting the response of patients to ER and GB treatments.