Two factors may explain this decrease: (1) in this group, the mice were not treated with the multi-peptide vaccine, i.e., Her-2/neu was not targeted, and therefore the tumor cells may have continued expressing the receptor, which is in direct correlation with increased RNA levels; (2) as mentioned above, it has been shown that Her-2/neu-targeting therapy with trastuzumab increases the PD-L1 expression. The gene discussed is ERBB2; the disease is neoplasm.