[Production of enzymes and enzyme inhibitors in neoplastic tissues]

The mechanisms of ectopic enzyme and enzyme inhibitor-production in neoplastic tissues were investigated. No evidence was obtained to suggest any difference in the structural genes of amylase-producing tumors and normal lymphocytes. mRNA sequence coding for amylase precursor in tumor tissues was identical to that of salivary amylase, suggesting that the amylase in amylase-producing tumors was identical to, or closely resembled the amylase in salivary gland. High incidence of elevation of serum pancreatic secretory trypsin inhibitor (PSTI) was observed in patients with various malignant tumors. PSTI-positive malignant cells were also frequently found in malignant tissues. A comparison of human PSTI mRNA sequence with mouse epidermal growth factor (EGF) mRNA sequence showed that they were 46% homologous. Human PSTI stimulated [3H]thymidine incorporation into DNA in human fibroblasts at concentrations present in human serum.