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. This evidence concerns the gene CEACAM5 and lung adenocarcinoma.