Escape of metastasizing clonal tumor cell variants from tumor-specific cytolytic T lymphocytes.

A metastasizing variant of a chemically induced lymphoma from a DBA/2 mouse is shown to carry a distinct tumor-associated transplantation antigen (TATA), which can be recognized by syngeneic secondary anti-tumor cytolytic T lymphocytes (CTL). During metastasis of twice-cloned cell lines of this tumor, variants develop that are specifically immunoresistant to lysis by anti-tumor CTL. The variants are detected in the spleen of normal syngeneic mice. They remain stable over long-term passage in tissue culture. The high frequency with which these immunoresistant metastatic variants develop was found to explain the relative ineffectiveness of specific immunization against this metastatic tumor. Compared with organ-selective metastatic variants, the immunoresistant tumor variants seem to arise with a much higher frequency. The change in TATA expression described here differs from antibody-induced antigenic modulation in that it is more stable and genetically transmitted.