The histidine requirement of a normal and a leukaemia cell-line from man: comparative effects on cell growth, metabolism and composition.

The object was to determine whether the depletion of histidine would have a more marked inhibitory effect on human leukaemia cells than on normal human cells, thus indicating a wider use for enzymes in cancer therapy. Studies of the effect of histidine concentration on cell growth, death, metabolism, protein composition, histidine uptake and utilization by cells were carried out. The medium and intracellular concentrations of histidine required for optimum cell growth and metabolism were much lower than for any other amino acid that has been studied. Also, there was very little evidence of cell death occurring in the absence of histidine. The results showed that cells in culture have a very low histidine requirement and that although the leukaemia cells were slightly more dependent upon histidine than normal cells the effect of histidine depletion is not critical enough to show much promise as a method of controlling leukaemia by therapeutic enzymes.