CEACAM6 as detected by the AP11 antibody is a marker notable for mucin-producing adenocarcinomas

A new monoclonal antibody recognizing CEACAM6, which we named AP11, was generated by immunizing BALB/c mice with phytohemagglutinin-activated human peripheral blood mononuclear cells. This study aims to evaluate whether CEACAM6 can serve as a tumor marker using AP11. We examined the expression of CEACAM6 with AP11 in 11 human carcinoma cell lines by flow cytometry and 439 human tissues including 282 tumor tissues and 157 normal tissues by immunohistochemistry. CEACAM6 epitope recognized by AP11 was well preserved in formalin-fixed and paraffin-embedded tissues. Adenocarcinomas of the stomach (86%), colorectum (95%), pancreas (100%), and lung (83%), urinary bladder (100%), and mucinous ovarian tumors (88%) had a high rate of CEACAM6 immunoreactivity. We observed a variable expression of CEACAM6 in hepatocellular carcinomas (35%), squamous cell carcinomas of the lung (60%), renal cell carcinomas (14%), urothelial carcinomas (13%), serous carcinomas of the ovary (17%), and breast carcinomas (11%). Small-cell carcinomas of the lung, prostatic adenocarcinomas, papillary thyroid carcinomas, malignant melanomas, giant cell tumors, and osteosarcomas were negative for CEACAM6. All normal tissues of various organs were negative for CEACAM6. In conclusion, CEACAM6 as detected by AP11, may serve as a marker for mucin-producing adenocarcinomas of the gastrointestinal tract and ovary as well as non-small cell lung cancer. Thus, AP11 represents a valuable diagnostic tool for detecting CEACMA6-positive cancers.