EFFECTS ON NEOPLASTIC GROWTH 265 



tate, and has been found in preliminary tests to induce some turaor re- 

 gression in patients, with occasional marked palliative improvement. 



Effects of lodoacetate on Susceptibility to Radiation 



Attempts have been made to increase or decrease the susceptibility of 

 cells to radiations, depending on whether one wishes to kill or protect the 

 cells. Anaerobiosis decreases and cyanide increases the susceptibility of tu- 

 mor cells to X-radiation, but Crabtree and Cramer (1933 b) could observe 

 no effects of either iodoacetate or fluoride. Franks et al. (1934) postulated 

 that radiation damages oxidative systems in cells and therefore that ra- 

 diated cells may be more dependent on glycolysis, which led them to deter- 

 mine regressions in two types of tumor (see accompanying tabulation). It 



may be that exposure to radiation increases the sensitivity of tumor C-180 

 to iodoacetate, but the effect is not marked. The aerobic glycolysis of tu- 

 mor C-180 is greater than that of the other tumor, which may account for 

 the effect. If E. coli cells are irradiated with ultraviolet light and then 

 treated with 0.2 mM iodoacetate for 15 min, the degree of survival is greater 

 than without iodoacetate (Wainwright and Mullaney, 1953). The mean in- 

 crease in viable cells produced by iodoacetate is around 128%. On the other 

 hand, the mortality of mice is increased by a combination of iodoacetate 

 and X-radiation (see accompanying tabulation) (Feinstein et al., 1954). 



Treatment Mortality at 30 days (%) 



X-radiation alone 



lodoacetate alone 10 



X-radiation, then iodoacetate 60 



lodoacetate, then X-radiation 90 



The dose of iodoacetate was 20 mg/kg. Quintiliani et al. (1961) found that 

 iodoacetate can sensitize mice and rats to ionizing radiations when given 

 intravenously at 40 mg/kg. The iodoacetate was also found to inhibit the 



