Dopamine induces apoptosis in murine tumor cells in vivo

Effect of dopamine (DA) on apoptosis of malignant tumor cells was evaluated in vivo in Swiss mice bearing Sarcoma-180 (S-180) and Ehrlich ascites carc inoma (EAC) transplantable tumors. DA was injected i.p. in two dose schedul es: i) 50mg/kg body wt/day for seven consecutive days beginning day 4 after transplantation and ii) 350mg/kg body wt, single dose, on day 10 of tumor bearing. Apoptotic cells were detected by in situ nick -end labeling (TUNEL ) method 24 hr after completion of treatment. Administration of DA resulted in significant increase (p<0.05) in the number of apoptotic tumor cells bo th in S-180 and EAC-bearing mice when compared with their matched controls. Single high dose of DA (350mg/kgx1) was found to be more effective in this regard than fractionated dose of equivalent amount of DA(50mg/kgx7). Unlik e tumor cells, there was little change in apoptotic index of bone marrow an d spleen cells following Da administration in fractionated doses. Single hi gh dose of DA, however, induced marked apoptosis (p<0.05) in marrow and spl een cells of tumor-bearing mice. The results suggest that DA induces apopto sis in murine tumor cells in vivo and this could be an important mechanism of tumor inhibition by this catecholamine.