Deregulated mRNA translation in cancer is a source of aberrant protein production when tryptophan shortage is induced by anti-tumor immunity (refs). Tryptophan is decoded by only one codon, and currently the consequences of aberrant protein production in conditions of a shortage of amino acids decoded by multiple codons are unknown. Leucine is decoded by six codons, and its levels influence a variety of key processes in cancer, including the control of mTOR signaling (ref) and epithelial to mesenchymal transition (PMID: 28274951). Here, we show that both leucine deprivation and DNA damage elicit ribosomal stalling and subsequent aberrant protein production predominantly at one codon for leucine, UUA. Mechanistically, we found that the leucine tRNA lowest in abundance is causative for ribosomal stalling and aberrant protein production. In addition, UUA-induced aberrant protein production impacts the landscape of neoepitopes presented at the surface of cancer cells, which can elicit T-cell recognition and killing. Altogether, codon-specific induction of neoepitopes by chemotherapy and leucine diet opens up new avenues for the development of adoptive T cell therapies.