Tumour-specific transplantation antigen from SV40 transformed cells binds to DNA

Abstract

MUCH work is being directed towards the characterisation of tumour-specific transplantation antigens (TSTA). AL/N strain mouse embryo cells transformed by SV40 virus (SV AL/N cells) are suitable for such studies, because (1) these cells are highly antigenic and are rejected at high dose (>10⁷) by the immunologically competent syngeneic AL/N mouse^1,2, (2) TSTA is common to all SV40 virus-transformed cells tested but specific in that only SV40 transformed cells share a common TSTA³, and (3), the SV40 ‘early’ or A gene is relatively small (∼1.8×10⁶ molecular weight), its mapping and the nucleotide sequences of the restriction endonuclease fragments are under intense study, and the various cellular antigens in the transformed cells—the TSTA, the tumour-specific surface antigen (TSSA) (ref. 4), and the nuclear T antigen—probably represent modifications of products of this early gene^5–7. Using SV AL/N cells and a detergent technique⁸ for solubilisation, we demonstrated that immunisation by a partially purified soluble extract containing 100 µg protein effectively protects mice against tumourigenic doses of SV40 transformed cells⁹. We report here that TSTA activity co-purifies with the T antigen in several steps, that TSTA can be recovered from a DNA column in a fraction which then effectively immunises at the 1-µg level, and that the TSTA, like the T antigen¹⁰, binds to double-stranded mammalian DNA.