COMMON TUMOR REJECTION ANTIGENS IN METHYLCHOLANTHRENE-INDUCED SQUAMOUS-CELL CARCINOMAS OF MICE DETECTED BY TUMOR PROTECTION AND A RADIOISOTOPIC FOOTPAD ASSAY
Transplantable lines (7) of squamous cell carcinoma [LSQ-2, LSQ-3, LSQ-6, LSQ-7, LSQ-10, LSQ-12 and LSQ-15] of the skin initiated in BALB/c mice by skin painting with methylcholanthrene were systematically tested for cross-reactivity of their tumor rejection antigens in a 7 .times. 7 matrix. As determined by decreased tumor frequency after tumor cell challenge, each line was immunogenic against and/or immunosensitive to at least 1 and usually more than 1 of the other lines. A radioisotopic footpad assay for delayed hypersensitivity against viable tumor cells confirmed the cross-reactivity shown by tumor rejection. More than 2 antigens appeared to be present in the lines. Tests for C-type viruses were positive in all tumors; those for polyoma virus were negative. Whether the uniform presence of C-type viruses can account for the number and variety of antigens found, or whether the tumor rejection antigens are independent of virus expression, remains an open question. The finding of cross-reacting tumor rejection antigens in methylcholanthrene-induced squamous cell carcinoma encourages prospects for the development of more broadly applicable immunodiagnostic and immunotherapeutic reagents.