THE DEVELOPMENT OF RESISTANCE TO 6-MERCAPTOPURINE IN A SUBLINE OF THE EHRLICH ASCITES CARCINOMA

Abstract

A subline of the Ehrlich ascites carcinoma has been developed which grows under 6-mercaptopurine (6-MP) therapy at approximately five times the rate of the parent line. Cells of the resistant subline were almost completely incapable of converting 6-MP to 6-MP nucleotide in contrast to those of the parent tumor line. A relationship between resistance to 6-MP and the capacity of the tumor cells to synthesize 6-MP nucleotide was indicated by a long-term study of these properties in branches of the resistant tumor subline which were maintained with and without exposure to 6-MP.