898 



METABOLISM OF THE CANCER CELL 



12 



10 



Whole plasma 



Globul 



^5 



r,2 



a 1 



injection) tumor — 10.6; liver — 7.7; kidney — 5.5; lung — 5.4, covints per min/mg. 

 These findings indicate that the tumor does utilize the labeled plasma albumin 

 more effectively than most normal tissues. The globulin was utilized by the tumor 

 and also by several normal tissues to approximately the same extent. 



Babson and Winnick (1954) have also 

 demonstrated that tumors may utilize 

 plasma protein for the synthesis of tumor 

 protein. They believe that the liver hyper- 

 trophy in rats bearing transplanted tumors 

 is a result of the tumors' requirement 

 for protein (Babson, 1954). Radioactive 

 plasma or labeled albumin or globulin was 

 infused into normal rats or rats with Walker 

 256 carcinoma and the animals were sacri- 

 ficed at intervals up to 20 hours (Babson, 

 1956). The specific activity of plasma pro- 

 tein fractions is illustrated in Figure 3. 

 These findings indicate that the albumin 

 and globulin disappeared from the plasma 

 of the tumor bearing rats at a rate almost 

 twice that of the controls. Campbell et al. 

 (1956) also obtained evidence that the 

 plasma protein may serve as a precursor of 

 the proteins of hepatoma. The above obser- 

 vations all point strongly to an extensive 

 utilization of plasma albumin by some ma- 

 lignant tissues. Campbell ( 1 958) has written 

 an excellent review on protein composition 

 and synthesis in normal and abnormal 

 growth. 



Transplants of Flexner-Jobling carci- 

 noma grew as rapidly in fasting as in fed 

 rats, according to LePage et al. (1952). 

 After administration of radioactive glycine 

 it was found that the radioactivity in the 

 normal tissues of the fasting animals di- 

 minished with time, whereas that of tumor tissue increased. These investigators 

 concluded that the proteins of the tumor were not available to the fasted animal 

 for its metabolic requirements. 



Several references have been made in previous sections to the relation between 

 glucose and protein metabolism. Campbell (1955) incubated rat liver and also 

 hepatoma in the presence of uniformly labeled glucose. After four hours the radio- 

 activity of the hepatoma proteins was from five to ten times greater than that of 

 the proteins from liver tissue. Glucose proved to be more effectively utilized for 

 synthesis of proteins in hepatoma than in normal liver tissues. From studies in- 

 volving the carbohydrate and protein metabolism in rat liver and hepatoma. 



5 10 15 20 



Time in hours 



Fig. 3. The disappearance of infused *'*C- 

 labeled plasma, globulins and albumin 

 from the circulation of normal and 

 tumorbearing rats. The circles represent 

 normal rats, and the triangles, tumor- 

 bearing rats. The radioactivity is express- 

 ed as the ratio of the radioactivity of the 

 plasma to the radioactivity of the corre- 

 sponding infusion X io~^. 



