In cancer tissues with high cholesterol levels, cholesterol upregulates IRE1α expression in CD8+ T cells and activates XBP1, increasing inhibitory receptor expression, including PD‐1, lymphocyte‐activation gene 3, T‐cell immunoglobulin domain and mucin domain‐3, 2B4, and CTL antigen 4, leading to the loss of CD8+ T cell functions [133]. Here, ERN1 is linked to cancer.