Cicaprost, a stable
prostacyclin analog has been shown to be antimetastatically active in a series of metastasizing rodent
tumors. Whereas starting treatment with
Cicaprost on the day of
tumor implantation was a characteristic feature of our previous investigations, the present study focused on the antimetastatic potency of
Cicaprost in animals with established
tumor growth. We have previously reported that, in Wistar-Furth rats bearing subcutaneously implanted SMT2A mammary
carcinoma,
Cicaprost in daily oral doses of 0.1 to 1.0 mg/kg given from the day of
tumor implantation to the end of the experiment led to a strong decrease in the number of lung
metastases. The 1.0 mg/kg doses reduced the number of lung
metastases by about 95% compared with the control. In the present study, we have examined the effect of delaying the start of treatment in animals with established
tumor growth,
Cicaprost in daily oral doses of 0.1 mg/kg given from Day 10 until Day 32 reduced the number of lung
metastases by about 80% compared with the control. In contrast, surgical removal of palpable primary
tumors had no effect on lung
metastasis. We conclude that
Cicaprost exhibits strong antimetastatic activity in the SMT2A rat mammary
carcinoma model and interferes not only with mechanisms of
tumor cell-blood cell interaction,
tumor cell adhesion, and extravasation, but also with steps following extravasation.