In another patient with chemo-refractory breast cancer treated with an HLA-A*02–restricted TCR specific for the p53R175H mutation, the vast majority of the tumor cells in the progressing lesion did not express HLA-A*02:01, although high expression of HLA-A*02:01 was observed in the tumor cells during the pretreatment biopsy (45). The gene discussed is HLA-A; the disease is breast cancer.