We have identified and quantitated a
tumor protein complex,
TSP-180, on murine
carcinomas with two
monoclonal antibodies (MoAbs) (
Cancer Res., 46: 707-712, 1986). One of the two MoAbs, 135-13C, recognizes a TSP-180-like
protein complex on several human
carcinomas in culture. MoAb 135-13C has been used to purify the human
TSP-180 complex from A431 cells and the purified material used to immunize F344 rats to produce another MoAb, 439-9B, to the human
TSP-180 complex. This MoAb does not precipitate the murine
TSP-180 or bind to murine cells. Both MoAb 135-13C and 439-9B precipitated the same
proteins from A431 cells but did not compete with each other for binding sites, indicating that they recognize different
epitopes on the same
protein. The two MoAbs have been used in a two-site assay to quantitate
TSP-180 proteins on human cells and tissues.
Carcinoma cell lines A431, SW948, and A549 all give high values (46 to 443 ng/mg of
protein) while murine
tumors, a human
melanoma, and human fibroblasts are negative (less than 10 ng/mg of
protein). Most tissues from autopsy of 2 normal individuals are negative for human
TSP-180 at the levels tested (less than 10 ng/mg of
protein). Some organs have intermediate range expression: spleen, 5 to 111 ng/ml of
protein; colon, 24 to 111; and small intestine, 39 to 99. One primary colon and one larynx
tumor were positive (144 to 372 ng/mg of
protein) while 5
breast carcinomas, a stomach
tumor, a metastatic
melanoma, and a kidney
tumor were negative. These data indicate that human
TSP-180 may be preferentially expressed in certain malignant
carcinomas of diverse origin. The potential for
TSP-180 as a
tumor marker requires further study.