Inhibition of 3H-thymidine incorporation into rat liver nuclei by E. coli L-asparaginase

Sensitivity of cultured pancreatic carcinoma cells to Acinetobacter glutaminase-asparaginase

Cultured human pancreatic carcinoma cells (MIA PaCa-2) have been shown previously to be very sensitive to E. coli L-asparaginase (EC II). The present studies have demonstrated that another enzyme, Acinetobacter glutaminase-asparaginase (AGA) is much more effective in inhibiting cell growth. At the concentration of 0.0025 U/ml of AGA activity the enzyme totally inhibited cell growth, whereas the EC II with the same concentration did not show any effect. The inhibition of cell growth correlated well with inhibition of protein and glycoprotein synthesis. The addition of L-glutamine at the concentration of 1 mM completely reversed the inhibition of protein synthesis. Similarly, the addition of L-glutamine at the concentration of 3 mM daily on 3 successive days after adding AGA resulted in significant reversal of growth inhibition. The results of this study indicate that the action of AGA on MIA PaCa-2 is, to a great extent, exerted through its L-glutaminase activity.

Mechanism of sensitivity of cultured pancreatic carcinoma to asparaginase

The effects of E. coli L-asparaginase on cultured human pancreatic carcinoma (MIA PaCa-2) have been studied. The enzyme (1 U/ml) inhibited growth and protein synthesis in both MIA PaCa-2 and PANC-1, another pancreatic carcinoma cell line, but had little or no effect on human breast carcinoma or melanoma cells. The inhibition of protein synthesis by E. coli L-asparaginase was largely reversed by L-glutamine but not by L-asparagine. The growth of both MIA PaCa-2 and PANC-1 showed absolute dependence on L-glutamine. These results indicate that the effect of E. coli L-asparaginase on cultured pancreatic carcinoma cells is exerted at least in part through its L-glutaminase activity. Although the addition of L-glutamine to the culture appeared to prevent cell death caused by L-asparaginase, it did not restore the ability of the cells to proliferate. Asparaginase derived from vibrio succinogenes, which is virtually free of L-glutaminase activity, was equally inhibitory to MIA PaCa-2 cell growth but did not affect protein synthesis. It is concluded that the inhibition of growth of cultured pancreatic carcinoma cells by E. coli asparaginase is a combined function of both its L-asparaginase and L-glutaminase activity.

[On the problem of praetherapeutic sensitivity testing of human tumours based on incorporation studies of nucleic acid precursors in vitro (author's transl)]

Praetherapeutic sensitivity tests of human solid tumours based on incorporation studies of nucleic acid precursors have been described by various authors. This review intends to show that such tests may only be of rather limited value for the design of individual chemotherapeutic regimens. In many drugs, a correlation between biochemical and clinical effects has not yet been established. The reliability of praetherapeutic sensitivity tests is further impaired by general methodological difficulties of short-term cultures, individual pharmacology and toxicology of cytostatic agents as well as pharmacological and biochemical drug interactions in combination chemotherapy. Praetherapeutic testing with individual cytostatic drugs is discussed.