MKC8866 is a salicylaldehyde analogue that has been proven to inhibit the activity of IRE1α to reduce the secretion of various tumor‐promoting factors, including IL‐6, IL‐8, chemokine ligand 1 (CXCL1), transforming growth factor β2 (TGFβ2), and GM‐CSF, to inhibit breast cancer cell proliferation. This evidence concerns the gene ERN1 and neoplasm.