Despite a high number of HLA class I peptides in DDA-MS/MS (HCC025 malignant: 5063; HCC025 non-malignant: 1497; HCC026 malignant: 3678; >HCC026 non-malignant: 3197), PRM tMS2 could not corroborate any of the PNEprot (Fig. 4) as naturally presented HLA ligands in HCC (Additional file 1: Table S8 & Table S9). This evidence concerns the gene SERINC1 and hepatocellular carcinoma.