Effect of RA233 alone and combined with radiation on experimental tumour metastasis. Part 1.

The effect of the platelet aggregation inhibitor RA233 alone or in combination with radiation was investigated on the spontaneously metastasizing B16 melanoma and on the Lewis lung carcinoma. The effect of this, agent on intravenously injected cells from these tumours was also studied. When single viable 3LL or B16 melanoma cells were injected intravenously, RA233 significantly increased the number of 3LL lung colonies but decreased significantly the B16 lung colonies. RA233 alone did not influence the number of pulmonary metastases arising spontaneously from the B16 or 3LL tumours either with the primary in situ or following excision. When lungs were irradiated before implantation of the 3LL an increase in the number of metastases resulted. This increase was unaffected by RA233 administration. When the primary B16 was irradiated 14 days after implantation and excised 7 days later, a significant decrease in numbers and distribution of metastases resulted in animals treated with RA233. This was accompanied by a considerable increase in long-term survivors.