Partial purification of C-C36 tumor rejection antigen molecules commonly expressed on syngeneic murine colon tumors, C-C36 and C-C26.

The tumor-specific transplantation antigens (TSTAs) of BALB/c mouse colon tumor C-C36 were characterized by gel filtration (TKS-gel FPLC), ion exchange chromatography (Mono Q FPLC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The cell surface antigens were solubilized noncytolytically with 2.5% n-butanol. It was demonstrated that the C-C36 antigens responsible for tumor rejection activity against C-C36 cells had a molecular weight of less than 200,000, and were eluted at 0.4-0.5M NaCl. On the other hand, the cross TSTAs expressed on C-C26 cells were eluted 0.2M NaCl. SDS-PAGE analysis of the partially purified antigens showed that the C-C36 TSTAs had four bands corresponding to molecular weights of 75,000, 68,000, 60,000 and 40,000. In contrast, the cross TSTAs expressed on C-C26 cells gave several major bands corresponding to 110,000, 94,000, 60,000 and 38,000, in addition to faint bands of 75,000 and 68,000. These results indicate that, although the partially purified C-C36 and C-C26 colon tumor antigens inducing rejection of C-C36 tumor challenge in syngeneic hosts showed differences in the ionic strength at which they were eluted, there are three common molecules with molecular weights of 75,000, 68,000 and 60,000, suggesting that these common molecules might be the tumor antigens responsible for the C-C36 colon tumor rejection.