Updated project metadata. Immunotherapy has shown great therapeutic potential for cancers with high tumor mutational burden (TMB), but much less promise for cancers with low TMB. One primary approach for adoptive lymphocyte transfer-based immunotherapy is to target the somatic mutated peptide neoantigens and cancer testis (CT) antigens recognized by cytotoxic T cells. Here, we employed mass spectrometry (MS)-based proteogenomic large-scale profiling to identify potential immunogenic human leukocyte antigen (HLA) Class ǀ- associated peptides in both melanoma, a “hot tumor”, and EGFR mutant lung adenocarcinoma, a “cold tumor”. We uncovered 19 common driver oncogene-derived peptides and more than 1000 post-translationally modified peptides (PTM) representing 58 different PTMs. We constructed a CT antigen database with 286 antigens by compiling reputed CT antigen resources and “in-house” genomic data and used this to identify 45 CT antigen-derived peptides from the identified HLA peptidome. Using integrated next generation sequencing data, we discovered 12 neopeptides in EGFR mutant lung cancer cell lines. Finally, we report a novel approach for non-canonical peptide discovery, whereby we leveraged a deep learning-based de novo search and a high confidence annotated long noncoding RNA (LncRNA) database to identify 44 lncRNA-derived peptides. Findings of this study, for the first time, provide evidence for a large pool of actionable cancer antigen-derived peptides for use in mutant EGFR lung cancer immunotherapy.