Similarly, tumor cell-derived lipid glucoceramides polarize macrophages toward a pro-tumor phenotype by inducing an ER stress response in macrophages, leading to the activation of STAT3 and the production of XBP1 mediated by IRE1 splicing, both acting synergistically to polarize macrophages toward a pro-tumor phenotype56. Here, XBP1 is linked to neoplasm.