CXCR4 and central nervous system cancer: Overexpression of CCR2, CCR4, CXCR1/2, and CXCR4 reportedly improved CAR T cell trafficking to brain tumors in preclinical studies (118, 138–140).CAR T cell pretreatment with metformin/rapamycin also enhanced mitochondrial respiration, leading to improved CAR T cell efficacy in glioma (141).