Identification and characterization of a colon-cancer-associated antigen expressed on leukemia-lymphoma cell lines

A total of 72 human leukemia-lymphoma cell lines were studied for reactivity with the monoclonal antibody (MAb) A7, an anti-human colon-cancer-cell-associated antigen reagent, by indirect membrane immunofluorescence. Nine of the 72 cell lines expressed the antigen recognized by A7 MAb. Five of the 34 T-cell lines, 2 of the 21 B-cell lines, and 2 of the 3 non-lymphoid-non-myeloid cell lines were reactive with A7 MAb. By means of SDS-PAGE and immunoblotting, the antigens isolated from both colon cancer cell lines (WiDr, SW1116 and LoVo) and leukemia cell lines (A3/KAWAKAMI, H9, RPMI 8226 and SPI-801) showed an identical MW of 42-43 kDa. The non-glycosylated antigen recognized by A7 MAb, which was expressed on both the colon cancer line (SW1116) and the leukemia line (H9) in the presence of tunicamycin, also showed an identical MW of 36 kDa. However, the quantity of the antigen in the leukemia cells was significantly lower than in the colon cancer cells. Although expression of this colon-cancer-associated antigen in the non-colon cancer cells is real, the significant expression of this antigen in colon-cancer cells makes it useful for clinical monitoring of colon cancer patients.