Changes in tumor-specific antigen expression during passage in vitro and in vivo of newly derived methylcholanthrene-induced sarcomas of BALB/C mice.

The characteristics of tumor antigens of the transplantation type, TATA, were studied in a series of methylcholanthrene-induced sarcomas in pedigreed BALB/cAN mice. Each of the six sarcomas exhibited unique TATA when assayed for tumor rejection in syngeneic hosts. In three instances, however, in sarcomas CI-I, CII-5 and CII-7, TATA activity was lost during early in vivo passages. This activity was reestablished invivo from the in vitro-passaged lines in CI-I and CII-7 and these sarcomas along with CI-3, CI-4 and CII-10 maintained a stable TATA phenotype throughout the 50 transplant passages; TATA was lost permanently, however, in CII-5. These results indicate a dimorphic nature of early-passage neoplasms. No cross-reacting antigens were detected among these sarcomas, including also Meth A, a sarcoma well characterized as to its membrane antigens; nor was any evidence obtained for the existence of alien (inappropriate) H-2 antigens employing tumor rejection assays in F1 hybrids of BALB/c with strains bearing several haplotypes and also with studies of H-2 serology. In three sarcomas, some evidence was obtained for the existence of alloantigens of the non-H-2 type since it was found that (BALB/c X DBA/2)F1 hybrids could not be immunized by respective sarcomas. These findings suggest the existence on these sarcomas of a tumor antigen that is expressed normally in DBA/2 mice, although no definitive evidence has been obtained. Assays for MuLV, for the viral structural proteins gp70 and p30 and for reverse transcriptase showed that three sarcomas were positive and three others, as well as Meth A, were negative. MuLV and its antigens had no influence on tumor rejection activity nor could the cross-reactivity observed in the radioisotopic footpad assay (IFP) be related to MuLV.