CCR9 and cancer: Considering the individual cancer-specific proteins, the highest number of HIV peptides homologous to TAAs (six) were predicted for the CCR9 (breast ca) and EPCAM (colon ca) proteins, covering the two most frequent HLA-A alleles in the world population (02:01 and 24:02) (Fig. 2 C; Additional file 1: Fig. S3B).