Two murine
monoclonal antibodies (MAbs) 5G8 and 2H6 were generated by fusing spleen cells obtained from mice immunized with human fetal tissue extract (14 weeks,
Nonidet P-40 membrane fraction) from the early first trimester, followed by a booster injection of a
lung cancer cell line. The MAb 5G8 recognized
antigens with a molecular weight of 90, 50, 20 kDa, was
neuraminidase-resistant and showed cross-reactivity with both
carcinoembryonic antigen and non-specific cross-reacting
antigen. The MAb 2H6 reacted with a
sialomucin whose molecular weight was more than 1000 kDa and was different from previously known
tumor associated-
marker antigens. The distribution of the MAb-recognizing
antigens in various tissues was investigated immunohistochemically. In
malignant epithelial tumors of the lung, acinar
adenocarcinoma and
bronchioloalveolar carcinoma were positive for both MAbs;
papillary adenocarcinoma,
squamous cell carcinoma, and
adenoid cystic carcinoma were positive only for MAb 5G8; solid
carcinoma with
mucin formation,
small cell carcinoma, and
large cell carcinoma were positive only for MAb 2H6. The combination of the two MAbs covered almost all histological types of lung
carcinomas (23 of 24 cases) except
carcinoid tumors. MAbs 5G8 and 2H6 reacted also with a restricted number of
adenocarcinomas of the other organs. MAb 5G8 did not react with normal fetal or adult tissues, except for metaplastic gastric mucosa, acinar cells of the breast and leucocytes, whereas MAb 2H6 reacted with the surface epithelium of the stomach and colon, the Brunner gland of the duodenum and uterine cervix as well as the epithelium of the fetal digestive tract. Thus, MAb 2H6 which recognized oncofetal
sialomucin, played a complementary role to MAb 5G8 as a CEA-related MAb in the immunohistochemical diagnosis of lung
carcinomas.