CEACAM5 and cancer: CEACAM5, also known as CD66e, is a glycoprotein encoded by the carcinoembryonic antigen gene and is expressed at low levels in normal tissues but at moderate to high levels in multiple cancers, including NSCLC: 20% of nonsquamous NSCLCs exhibit high expression (> 50%), and 25% exhibit moderate expression (1–49%) [213].