Several preclinical studies have indicated that trastuzumab increases HER2 internalization and cross-presentation by dendritic cells, upregulates PD-1 and PD-L1, induces expression of tumor-infiltrating lymphocytes, and modulates expression of major histocompatibility complex class II, resulting in the enhancement of HER2-specific T-cell responses [59,60,61]. This evidence concerns the gene PDCD1 and neoplasm.