The effect of exposure to dibutyryl cyclic adenylic acid on the membrane antigenicity of SV40 tumor cells.

When SV40 tumor cells (F5-1) in culture were treated with dibutyryl cyclic adenylic acid (DbcAMP),marked alterations occurred in their growth and morphology. Additionally, the incorporation or uptake of labeled thymidine, uridine, phenylalanine, and choline were reduced by this treatment. These modifications with DbcAMP exposure produced conditions simulating those of a contact-inhibited state. The immunization of hamsters with X-irradiated tumor cells previously cultured in the presence of DbcAMP indicated that the tumor-specific transplantation antigens and/or fetal antigens were altered during short-term expsoure to DbcAMP. Further examination of membrane antigens of SV40 tumor cells using the isotopic antiglobulin technique demonstrated a significant reduction in the tumor membrane antigen on cells cultured with DbcAMP.