882 



METABOLISM OF THE CANCER CELL 



12 



TABLE 3 



CRITERION OF MALIGNANCY 



(from Burk, 1939) 



Malignant range 



Normal range 





2-10 

 0-15 



3(0. ^ - Q. ^) / Q. Meyerhof oxidation quotient 3-6 



N 



Q, 2-2(2. (fermentation excess) -5 to + 25 



Q^ I Q_ respiratory quotient 0.75-0.9 



less I with excep- 

 tion noted above 



2-8 

 0.5-2.0 

 -2 to -30 

 over i.o 



( 



rates of most normal and cancer tissues are of approximately the same magnitude, 

 3-20 ml of oxygen per milligram of dry tissue per h. (0,02). A high anaerobic 

 metabolism (usual range of 1 5-40 ml of lactic acid equivalent per milligram dry 

 tissue per h.) is observed in most neoplastic tissues. With the exception ofembry- 

 onicj placental, retinal and brain cortex, most tissues exhibit^an anae robi c glyco- 

 lytic metabolism of 10-20% thaiJxfjLhe-iiancer^tissue^ In the presence of oxygen, 

 glycolysis is reduced in cancer tissues to approximately 50% of that observed 

 anaerobically while in most normal tissues glycolysis is abolished in the presence 

 of oxygen. This difference in oxidative metabolism led Burk to postulate a crite- 

 rion of malignancy (Table 3). 



Thus, in general, it may be observed that tumors as a group do possess a char- 

 acteristic glycolytic metabolism. On the basis of these oxidative differences, Burk 

 and Schade (See Weinhouse et at., 1956) and Burk and Woods (1956) have pro- 

 posed a general test for malignancy. Ten mg. of tissue is inoculated in serum 

 medium in a Warburg flask. Glucose is added to the medium and the reaction 

 is carried out in the presence of 5.5% CO, in oxygen. All tumor tissues w^ill 

 exhibit a positive manometric pressure while all normal and embryonic tissues 

 give a negative pressure. Overlapping between the normal and neoplastic ranges 

 does occur and consequently there has been a tendency to deemphasize the im- 

 portance of the general Warburg concepts. Nevertheless, the convergence of 

 most malignant tissues in the direction of a characteristic and imiform metabolism 

 still constitutes the most consistent metabolic difference yet observed between 

 normal and neoplastic tissues. 



The Warburg school accounts for this aspect of the metabolism of tumors on a 

 basis of a faulty respiration or a respiratory impairment. Many investigators have 

 opposed some of the Warburg concepts. It would appear however, that most 

 scientists are in agreement as to the importance and the validity of the differences 

 that generally exist in the overall oxidative metabolism of normal tissues and 



