Interestingly, in 4T1 tumors, ppM1 treatment selectively enhanced the expression of PD-1 on leukocytes (CD45+) (Figure S8H) but not the expression of PD-L1 on tumor cells (CD45−) (Figure S8I), suggesting that there would some benefits from ppM1 in combination with PD-1 antibody. Here, CD274 is linked to neoplasm.