Tumour-bearing mouse models have shown that activation of the IRE1α and ATF6α pathways induces the development of polymorphonuclear MDSCs (PMNMDSCs) and promotes the immunosuppressive activity of PMNMDSCs (Fig. 3), thus leading to inhibition of the tumour-specific immune response and an increase in tumour progression [195]. Here, ATF6 is linked to neoplasm.