We have investigated the effects of
desmopressin (
DDAVP), a synthetic analog of the natural
hormone vasopressin, on experimental lung colonization of mammary
tumor cells using a syngeneic BALB/c mouse model. Coinjection of
DDAVP (1-2 microg/kg
body weight) at the time of i.v. inoculation of F3II
carcinoma cells or LM3
adenocarcinoma cells significantly inhibited the formation of experimental lung
metastases. In both cases, the number of pulmonary nodules was reduced about 70%. Inhibition of
metastasis was also obtained with i.v. administration of
DDAVP 24 h after
tumor cell inoculation. Interestingly, the inhibition of lung
metastasis was not due to direct cytotoxic effects of
DDAVP on mammary
tumor cells. The in vitro formation of multicellular aggregates in the presence of citrated plasma from control and
DDAVP-treated mice was also examined. Control plasma rapidly induced a significant
tumor cell aggregation. In contrast, in the presence of plasma from
DDAVP-treated mice,
tumor cells remained as a single cell
suspension.
DDAVP may help to dissolve the protective
fibrin shield of
circulating tumor cells. Our data suggest, for the first time, that adjuvant
DDAVP therapy may impair successful implantation of circulating mammary
tumor cells.