LTB and cancer: Importantly, our study provided evidence that MAM polarization is directly linked to the molecular characteristics that cancer cells acquire upon site-specific metastasis by (i) demonstrating an increased potential for M2 macrophage polarization by cancer cells that have metastasized to the brain parenchyma compared to the parental cancer cell line, and (ii) by demonstrating that the cancer cell-associated LTβ is functionally implicated in the polarization of parenchymal MAMs.