LAUSR

In their original research (1), the authors were looking for a potential KRAS epitope for use in targeted cancer immunotherapy in the form of an HLA-presented peptide that would have the following three properties: i) cover the KRAS G12Vmutation; ii) be a result of peptide digestion and splicing in the proteasome; iii) bind to HLA-A*02:01. The authors claim to have found such a peptide (KLVVGAVGV) by in vitro digestion of a mutated KRAS polypeptide by purified proteasomes. However, we suggest that this finding may have been based on misidentification of the peptide. Our analysis and conclusion relied on data deposited by the authors in PRIDE project PXD015580, including mass-spectrometry (MS) raw files and peptide identification results. The authors initially performed 45 MS analyses of the proteasome-digested KRAS polypeptides. These included 3 biological replicates x 3 technical replicates, where each of the 9 replicates was sampled for MS analysis at 5 time points (0, 1, 2, 3 and 4 hours). Several weeks later, the authors