2-5A synthetase activity in patients with metastatic carcinoma and its response to interferon treatment.

The interferon-induced enzyme 2-5A synthetase was measured in extracts of ficoll-purified peripheral mononuclear cells from normal healthy volunteers and a large group of patients with metastatic carcinoma. The range of values in both populations was very large and overlapped considerably. On average, individuals with disseminated cancer have a two-fold increase in 2-5A synthetase activity. In addition, several patients have been identified who appear to have fully induced 2-5A synthetase activity with no detectable serum interferon and no history of prior interferon injections. This indicates that the interferon regulated 2-5A system is activated in metastatic carcinoma. Treatment of patients with interferon-alpha caused a dose-dependent increase in enzyme activity. The maximum fold increase varied from individual to individual, as did the dose required for maximum enzyme stimulation. A rigorous attempt must now be made to correlate enzyme induction with the clinical outcome of interferon treatment in order to assess the clinical value of such measurements.