The results showed that APOBEC1 was negatively correlated with the infiltration level of many kinds of immunoreactive tumor infiltrating cells, the expression level of most immune promoters, immune score and matrix score, indicating that the high expression of APOBEC1 may inhibit the immune response to PAAD, while the immunomodulatory effects of APOBEC3A/3G/3H are the opposite. Here, APOBEC3A is linked to neoplasm.