The "in vivo" effect of protein A on tumor growth

The antitumor effect of two purified preparations of protein A obtained from Staphylococcus aureus strain Cowan 1 or the mutant strain A676 was investigated. This study using different doses of SpA (5 or 10 mg/animal) i.p. administered was performed in lymphosarcoma bearing rats at certain intervals of time after tumor transplantation. The treatment with SpA deriving from A676 strain which was started at the same time with the tumor transplantation led to a significant increase in the latency period of tumor growth and the prolongation of survival time of tumor bearing rats. Attempts to use a higher dose of SpA and also a smaller tumor inoculum did not improve the results with regard to inhibition of lymphosarcoma growth in inbred R rats.