The biosynthesis of free glycine and serine by tumors.

When cell suspensions of the Gardner lymphosarcoma were incubated with acetate-2-C14, ap preciable radioactivity was observed in the alpha carbon of free glycine (4). There are described be low experiments showing that the methyl carbon of acetate may also be utilized in the formation of free serine. The incorporation of radioactivity from labeled glucose into both amino acids and of labeled ribose into glycine is also demonstrated (5). The latter conversions take place in tumors other than the Gardner lymphosarcoma. The author proposes the following scheme as a basis for discussion : Tissues and incubation procedure.—TheGardner and Mecca lymphosarcomas, previously transplanted to grow as solid tumors, were transformed into ascites tumors. It was observed that less total radioactivity was found in Gardner ascites tumor glycine after incubations with labeled acetate than in the earlier experiments (4), which were carried out with cell suspensions made from the solid tumors. The preparation of cellular suspensions from the solid tumors involves a rather thorough extraction of soluble proteins and endogenous metabolites. Possibly, the difference is partly attributable to this factor. (Note, in this connection, Table 4 and Table 5, experiment 1.) However, the observed conversion by the ascites cells was deemed adequate for our purposes, so that ascites cells were used thereafter. Tumor-bearing animals were sacrificed 7-10 days after the intraperitoneal inoculation of 0.1-0.2 cc. of ascites fluid.