Production of tumor-associated antigen, TA-4, by the CaSki cervical carcinoma cell line

Previous Japanese studies described the purification of TA-4 from homogenates of tumor tissues excised from squamous cell carcinomas of the uterine cervix, and the development of a radioimmunoassay to detect TA-4 in sera of patients with this disease. The aim of the present investigation was to determine if TA-4 was produced by the CaSki cell line, established in culture ten years ago from epidermoid carcinoma of the uterine cervix. The radioimmunoassay detected the TA-4 antigen in the CaSki cells, but not in cell lines derived from either choriocarcinoma or breast carcinoma. The TA-4 concentration in the CaSki cell lysate exceeded that in the CaSki culture fluid by more than twentyfold, and exceeded the concentration of human chorionic gonadotropin beta-like immunoreactive material by nearly two orders of magnitude. Antiserum to TA-4 was used to immunoprecipitate biosynthetically labeled TA-4 from CaSki cultures that had been incubated with [3H]leucine. After electrophoresis and autoradiography, the immunoprecipitated material showed a major band corresponding in apparent molecular weight (48,000 daltons) to TA-4 originally isolated from squamous cell carcinoma tumors. It is concluded that the CaSki cell line constitutes an ideal model with which to investigate the biosynthesis and regulation of TA-4, and a source for large-scale production of TA-4 for characterization studies as well as development of clinical diagnostic reagents.