Abstract
A variant of the Yoshida sarcoma which became resistant to methylbis-(beta-chlorethyl)-amine N-oxide (MBAO) upon passage through animals treated with the agent, was demonstrated to be resistant to 3 other alkylating agents, methylbis-(beta-chlorethyl)-amine, tris-(beta-chlorethyl)-amine and tris-ethylenimino-s-triazine. It proved sensitive to another unrelated antitumor agent, colchicine. Resistance to MBAO has remained unchanged following 24 consecutive serial transfers in rats free of the agent.