We observed that HLA class I loss was associated in most cases with low transcriptional levels of HLA class I, TAP1/2 and B2M across several tumor types, by RT-qPCR (Taqman assay) using a panel of PDXs, particularly in neuroblastoma, rhabdomyosarcoma, and nephroblastoma. This evidence concerns the gene TAP1 and rhabdomyosarcoma.