XBP1 and breast carcinoma: Previous studies have demonstrated how cholesterol metabolism affects the anti‐tumor activity of T cells [25], how cholesterol can act on immune cells to promote breast cancer metastasis and recurrence [25], and how elevated cholesterol levels induce endoplasmic reticulum stress, leading to increased XBP1 expression, which in turn promotes the expression of immune checkpoints and suppresses T cell function [26].