Generation of antigenic variants from a nonantigenic murine tumor cell line by transfection with a gene encoding a novel tumor-specific transplantation antigen.

Tumors induced in mice by UV radiation often express highly immunogenic tumor-specific transplantation antigens (TSTA). The 216 gene, which encodes a TSTA of the C3H tumor UV-1591, has been cloned and characterized as a novel major histocompatibility complex Class I antigen. The purpose of this study was to determine whether the 216 gene-encoded TSTA can function as a tumor rejection antigen when expressed on unrelated, nonantigenic murine tumor cells or whether its function is restricted to UV-induced tumors. A cell line (10T-1) derived from a spontaneous transformant of C3H 10T1/2 cells was cotransfected with DNA from p216 and pSV2-neo plasmids. About 2 wk after transfection, G418-resistant colonies were isolated randomly and tested for cell surface expression of the 216 gene product using a monoclonal antibody specific for 216 gene-encoded TSTA. Of 20 clones tested, four expressed high levels of 216 gene-encoded TSTA. These four clones were highly antigenic in that they were completely rejected in normal mice but grew progressively in nude mice. Furthermore, the 216-positive clones were immunologically cross-reactive with UV-1591, as determined by in vitro cytotoxic T-lymphocyte and in vivo immunization and challenge assays. Surprisingly, 216-positive 10T-1 transfectants also cross-reacted with 10T-1 cells, both in vitro and in vivo. These results demonstrate that the product of a cloned TSTA gene from a UV-induced murine tumor is capable of functioning as a tumor rejection antigen when expressed on unrelated, nonantigenic tumor cells. In addition, these results indicate that this approach could be used to augment the immune response against poorly antigenic tumors.