Significance of dialysis against enzymes to the specific therapy of cancer and genetic deficiency diseases

Theoretical and practical considerations in the use of hemodialysis for the therapeutic removal of asparagine and other amino acids

The endogenous asparagine influx in mice undergoing asparaginase therapy can be neutralized by asparaginase activity equivalent to less than one IU/ml of plasma, as determined with a new, highly sensitive micro assay for asparaginase. It appears feasible that an asparagine influx of this magnitude may be cleared from the blood plasma by hemodialysis employing an artificial kidney apparatus with a clearance capacity somewhat greater than that routinely employed by renal patients. Application of this method for removing asparagine or other amino acids from the blood as an approach to cancer therapy ultimately depends upon the specific amino acid influx rates of the subject and upon the ability of the dialyzer to deplete the free amino acids in the blood plasma at a sufficiently high rate to lower specific amino acid concentrations in malignant tissues, or in adjoining interstitial spaces, to therapeutic levels. Based upon the data available, hemodialysis has potential therapeutic application as a means to control the removal of various free amino acids or other metabolic substrates from blood plasma.

Concentrations of free amino acids and other blood components in a lymphoma patient during intensive hemodialysis

l-Asparaginase is used as a therapeutic enzyme to selectively destroy asparagine-dependent cancer cells. This study explores alternate means for depriving cancer tissues of l-asparagine and other specific amino acids or vital substrates required by normal and cancer cells. Hemodialysis, employing an artificial kidney, was used to remove free amino acids from the blood of a patient with lymphoblastic lymphosarcoma. Approximately 1200 mg, the equivalent of the patient's total amino acid pool, was removed every 100 minutes while the patient was on the artificial kidney. Despite this impressive clearance capacity, the dialyzer was not able to completely overcome the endogenous amino acid influx of the patient. The combined data indicate that hemodialysis is theoretically capable of removing specific amino acids to a therapeutic level, but that the clearance efficiency of the artificial kidney must be significantly increased or the endogeneous amino acid influx must be effectively blocked before hemodialysis can be successfully applied to cancer patients. An unexpected finding was strikingly increased during dialysis but returned to the original levels when dialysis was temporarily discontinued. The presence of a nonprotein inhibiting factor capable of suppressing an increase in the peripheral malignant lymphocyte population could be an explanation. This postulated factor behaved during dialysis as though its molecular weight was relatively low, possibly less than 500.