Arrest of in vivo proliferation of Zajdela tumor cells by inhibition of mitochondrial protein synthesis.

The proliferation of Zajdela tumor cells, grown in vivo in Wistar rats, is arrested by low amounts of oxytetracycline. Oxytetracycline is administered by means of continuous infusion in such a way that the oxytetracycline concentration in serum and ascitic fluid is maintained at a level at which only mitochondrial protein synthesis is blocked. Under these conditions, Zajdela mitochondrial tumor cells cease dividing after a few cell generations, an event which is preceded by reduction of cytochrome c oxidase activity of the tumor cells. Toxicity to host tissues is limited to the immune system which is apparently suppressed by the drug. Even so, oxytetracycline might have therapeutic potential in human cancer therapy, especially because it does not influence the hemopoietic system.