CD8A and breast cancer: While there is clear evidence that T cells do infiltrate BCBMs, comparative analyses of intratumoral CD4+ and CD8+ TILs in BC patients show lower accumulation of TILs in BMs compared to extracranial metastases [57] or primary tumors [58, 59], suggesting that ITs that enhance T cell trafficking to BCBMs may also be a valid strategy for enhancing efficacy.