GABA CONTENT AND GAD ACTIVITY IN COLON TUMORS TAKEN FROM PATIENTS WITH COLON-CANCER OR FROM XENOGRAFTED HUMAN COLON-CANCER CELLS GROWING ASS.C. TUMORS IN ATHYMIC NU NU MICE/

A significantly high GABA level and GAD activity was found in human co lon cancer tissue as compared with normal macroscopically unchanged hu man colon wall taken from the same patients. Similarly in athymic nu/n u mice transplanted with human colon adenocarcinoma cells established in in vitro culture (line CX-2) the high level of GABA accompanied by high GAD activity was found in subcutaneously growing tumors as compar ed with the unchanged colon wall and unchanged skin tissue from the sa me tumor bearing mice. Interestingly, the level of GAD activity in the macroscopically unchanged colon tissue of mice tranplanted with tumor cells were increased in comparison with normal colon of healthy contr ol mice. For the skin, only GAD activity was higher in the material co ming from tumor bearing mice than in the material from normal control mice, whereas GABA level was even lower in the skin of tumor inoculate d mice compared with control group.An increase in GABA level and in GA D activity can perhaps reflect a local immune response to the neoplast ic process. The observed direction of GABA metabolism in tumor of the colon indicates a possibility to interfere in this process using the a gonists of the GABA-ergic system.