Six distinct
cell surface antigens of human trophoblast and
choriocarcinoma were defined with MAbs. The distribution of the
antigens was determined by MHA assays on 150 tumor cell lines and normal cell cultures and by immunofluorescence tests with a wide range of normal adult and fetal tissues and a
tumor panel.
Antigen LK26 is expressed on all cultured
choriocarcinoma,
teratocarcinoma and
renal cancer lines but is absent from most cell lines derived from other
tumor types and from cultures of normal kidney epithelium and fibroblasts. LK26 expression in normal tissues is restricted to the trophoblast. No other adult or fetal tissue was found to express the
antigen, but
choriocarcinoma and
teratocarcinoma tissues were LK26+. SV19 is expressed on cultured
choriocarcinomas and
teratocarcinomas and on subsets of breast and
colon cancer lines, but not on 120 additional cultures tested. In tissues, SV19 is detected in normal placenta, mammary gland and colon epithelium as well as in
tumors of breast, colon and lung. Two
antibodies, AbSV63 and AbK8, react with PLAP and AbSV63 also reacts with the intestinal form of the
enzyme. AbLK24 defines a heat-stable determinant present on
choriocarcinoma and
breast cancer cell lines but absent from most other cultured cells. It is expressed on a small range of normal and malignant epithelial tissues, including normal trophoblast, normal breast epithelium and urothelium and
tumors derived from these tissues. One
antigen, K66, showed a wide distribution on cultured epithelial cells but was not found in any normal or malignant tissue. Finally, S4, a previously described marker of normal and malignant kidney epithelial cells, was also expressed on the
choriocarcinoma cell lines. Four of the
antigens are
glycoproteins that could be immunoprecipitated from radiolabelled extracts of
choriocarcinoma cells: LK26 (Mr 35,000), SV19 (Mr 40,000), PLAP (Mr 68,000) and S4 (Mr 160,000). The highly restricted distribution of LK26, SV19, S4, and PLAP in normal tissues and their expression in
tumors make these
antigens potential diagnostic markers of gestational
choriocarcinoma and
germ-cell tumors and, possibly, targets for
immunotherapy.