MUC1, also known as cancer antigen 15–3 (CA 15–3), is a large transmembrane glycoprotein, expressed on the apical surfaces of most simple secretory epithelial cells, that undergoes auto-cleavage into two subunits (MUC1-N and MUC1-C)34, and is overexpressed in a variety of carcinomas including that of the lung35. This evidence concerns the gene MUC1 and carcinoma.