XBP1 and cancer: CD4 + Tc and CD8 + Th cells isolated from ovarian cancer ascites demonstrate increased X-box binding protein 1 (XBP1) messenger ribonucleic acid (mRNA) splicing compared with peripheral T cells from cancer-free patients [226], reflecting endoplasmic reticulum stress and activation of the unfolded protein response (UPR) that controls mitochondrial respiration and anti-tumor function.