Evaluation of human carcinoembryonic-antigen (CEA)-transduced and non-transduced murine tumors as potential targets for anti-CEA therapies

The MC-38 C57BL/6 mouse colon adenocarcinoma cell line has been transduced with a retroviral construct containing cDNA encoding the human carcinoembryonic antigen (CEA) gene [Robbins PF, Kantor JA, Salgaller M, Horan Hand P, Fernsten PD, Schlom J (1991) Cancer Res 51: 3657]. Two clones, MC-38-ceal and MC-38-cea2, expressed high levels of CEA on their cell surface. A third CEA-expressing cell line, MCA-102-cea3, was similarly derived by transduction of the MCA-102 C57BL/6 mouse fibrosarcoma cell line and is described here. In this study, the three CEA-transduced murine tumor cell lines (MC-38-cea1, MC-38-cea2, MCA-102-cea3) were evaluated for their tumorigenic potential, as well as their ability to serve as in vivo model systems for active and passive immunotherapy studies. Parameters that were investigated include tumor growth rate, the antibody response of the host to CEA, and the CEA content of the tumors. The MC-38-cea2 model appeared to be the most appropriate for immunotherapy studies. Biodistribution studies, using an¹²⁵I-labeled anti-CEA mAb, demonstrated efficient tumor targeting of MC-38-cea2 tumors in C57BL/6 and athymic mice.     

Influence of osmolytes, thin filaments, and solubility state on elasmobranch phosphofructokinase in vitro

Skeletal muscle phosphofructokinase (PFK) purified from the thornback ray is rapidly inactivated by urea concentrations as low as 50 mM at pH values below 7.0. Urea-induced loss of PFK activity is not offset by trimethylamine-N-oxide. Protection against urea-inactivation in vivo, where urea concentration may approach 0.5 M, may be due to two effects. Filamentous (F) actin and muscle thin filaments moderately reduce the urea-induced loss of PFK activity. The binding of PFK to F-actin and to thin filaments is shown by ultracentrifugation experiments. PFK activity in vivo also may be stabilized in this species by the formation of a particulate enzyme form which is totally resistant to inactivation by physiological concentrations of urea.