Ill PROTEINS AND AMINO ACIDS 897 



tumor was similar to that of other ascites tumors and tumors undergoing regression. 

 Human tumors contained more total free amino acids than normal tissues, and 

 Kotake and Ohsuka (1953) indicated that this difference was probably due to 

 the presence of trypsin-like enzymes of higher activity in the tumor tissues. 



Several attempts have been made to resolve the extractable proteins of normal 

 and neoplastic tissues by electrophoresis and in the ultra centrifuge (Greenstein, 

 1956). Thus far the results have been difficult to interpret because of the complex- 

 ity of the mixtures involved, though, some indication of differences have been 

 obtained. Miller et al. (1950), in screening the electrophoretic patterns of mouse 

 muscle and rhabdomyosarcoma, fovmd three major components in the muscle 

 and seven in the tumor extract. The individual components of the tumor extract 

 all appeared to be quite distinct from the muscle components. Toennies (1952) has 

 also pointed out that there is a definite difference between the electrophoretic 

 behavior of proteins of normal and tumor tissues. Transplantation of tumors 

 did not change protein composition (Gigante et al., 1954). 



It is apparent that the experimental findings up to the present time have not 

 revealed any characteristic compositional pattern in tumors with respect to amino 

 acids or proteins. However, differences have been noted that may be of significance 

 in the overall problem. New techniques for the isolation and purification of indi- 

 vidual proteins should greatly increase the potential for future success in this area. 

 By the use of column chromatography, gel electrophoresis and other methods, 

 it is now possible to obtain workable quantities of highly purified protein fractions. 

 These individual components may then be subjected to further rigid character- 

 ization by various physical methods and by amino acid composition and possible 

 differences in protein composition or behavior of normal and tumor tissue may 

 then be firmly established. 



{b) Protein metabolism 



It is obviously very difficult to discuss protein and amino acid metabolism sepa- 

 rately. An attempt has been made to include under protein metabolism those studies 

 in which the effort is directed towards the formation or biosynthesis of proteins. 



An uptake of the lower peptides, glycylgiycine, glycylglycylglycine and a-L- 

 glutamyl-L -glutamic acid was observed by Christensen and Rafn (1952) in sus- 

 pensions of cells of ascites carcinoma, but not by erythrocytes. Busch and Greene 

 (1955) injected into normal and tumor-bearing rats, glycine-2-''*C, DL-lysine- 

 2-'''C or plasma proteins containing the same radioactive amino acids. They 

 found that the uptake of the labeled amino acids by the tumor proteins was not 

 significantly different from that of the normal tissues. The important observation 

 was made, however, that the rate of increase of '"^C in tumor proteins was two to 

 ten times that of the proteins of normal tissues following the injection of labeled 

 plasma. In a subsecjuent study, Busch et al. (1956) isolated the radioactive plasma 

 albumin and globulin from rats injected with ^'*C-lysine. These protein fractions 

 were injected into rats with Walker 256 carcinoma and three hours later the 

 following specific activities of proteins in various tissue homogenates were re- 

 corded: (Albumin injections) tumor — 10.5; liver — 3.4; kidney — 3.8; spleen 

 — 3.6; testes — 3.6; brain — 0.7; and lungs — 8.9, counts/min/mg. (Globulin 



Literature p. gig 



