While both CCR2 inhibition and anti-PD-1 have failed as monotherapies for glioblastoma, preclinical murine models have shown that a CCR2 antagonist improves the efficacy of anti-PD-1 in cancers such as glioblastoma, bladder, and breast cancer (Flores-Toro et al. (2020); Tu et al. (2020)). Here, CCR2 is linked to breast cancer.