gi4 METABOLISM OF THE CANCER CELL 12 



primary tumor. The enzyme present in normal endocrine tissues which catalyzes 

 the oxidation of A^ unsaturated steroids with a 3-^ alcohol group to the corre- 

 sponding a, [3 unsaturated A-^-4-ketone was also found in tumors arising from 

 mouse adrenal cortex and testicular interstitial cells (Hviseby et al., 1954). 



Rhodanese, the enzyme which catalyzes the conversion of hydrocyanic acid 

 and thiosvilfate into thiocyanate and bisulfite, was present in much lower con- 

 centration in rat hepatoma than in liver. However, the activity was still higher in 

 the tumor than in any other normal tissue (Rosenthal, 1955). It was suggested 

 that the high aerobic glycolysis of normal and neoplastic tissue deficient in rho- 

 danese may be attributed to the inhibition of the Pasteur reaction by the minute 

 quantities of cyanide formed in the intermediary metabolism of the cells. Intact 

 mammalian cells and slices of normal and tumor tissues utilize ribose-5-phosphate 

 to form sedoheptulose, fructose and lactid acid. Fixation of CO, into the 

 carbonyl group of lactic acid occurred during anaerobic conditions suggesting 

 that these tissues may possess phosphoribulokinase and carboxydesmutase (Guzman 

 Barron et al., 1955). Ehrlich ascites tumor cells do not exhibit cholinesterase activ- 

 ity according to Holler and Leonhartsberger (1954). 



Rat hepatomas and normal tissues have the same acid and alkaline ribonu- 

 clease activity when expressed on a fresh weight basis, but different activities when 

 based on the mitochondrial fraction. Mitochondria isolated from the rat liver 

 tumor possessed the same acid phosphatase activity and deoxyribonucleodepoly- 

 merase activity as normal liver mitochondria (Allard, 1955)- An association of 

 acid and alkaline phosphomonesterase with cytoplasmic particles from fowl 

 sarcoma has been noted by Harris (1954). The tissue concentration of acid phos- 

 phatase was the same in benign human tumors and inflammatory lesions. Adenocar- 

 cinoma of the colon had a higher tissue acid phosphatase than was present in the 

 adjacent normal colon. Similar increases of tissue acid phosphatase were found in 

 other types of adenocarcinomas and in some epidermoid and sarcomatous tumors 

 compared to homologous normal tissues of origin (Lemon et al., 1954). A large 

 number of surgical specimens of adenocarcinoma of the colon and rectum were 

 found to have increased contents of adolase (Sibley and Fleisher, 1955). This 

 finding is in agreement with the general tumor pattern of higher levels of the enzyme 

 of glycolysis. 



The phenol-oxidizing system of human melanomas was studied by Kertesz 

 (1954). Dopa and tyrosine oxidase activity of these tumors varied considerably. 

 It was reported that this mammalian enzyme system was bound to the particulate 

 elements of the tumor homogenates and is highly specific for dopa and tyrosine 

 as opposed to the low specificity of the plant polyphenoloxidases. Humm and 

 Clark (1955) investigated the oxidative metabolism of melanomas in platyfish- 

 swordtail hybrids. Some evidence was obtained that the tyrosinase system may 

 be involved in hydrogen transfer in these tissues as an adjunct to the usual respira- 

 tory mechanism. The question as to whether or not the melanin system may be 

 essential to the origin or growth of malignant melanoma has not been definitely 

 answered. While some melanomas are low in tyrosinase activity and also in the 

 degree of pigmentation, this does not provide conclusive proof that tyrosine me- 

 tabolism is completely inhibited. The tyrosine or dopa may proceed through 



