Cholinesterase activity and enzyme components in healthy and cancerous human colorectal sections.

The effect of cancer on acetyl- (AChE) and butyrylcholinesterase (BuChE) activities of human gut was investigated. ChE activity was measured in 55 paired samples of healthy and malignant colon, sigmoid colon and rectum. Cancer decreases the mean AChE activity value from 2.17 +/- 1.07 to 1.40 +/- 0.89 mU/mg (p < 0.001), and BuChE activity from 4.16 +/- 2.41 to 1.65 +/- 0.87 mU/mg (p < 0.001). AChE monomers and dimers (light forms), and less asymmetric and tetrameric variants (heavy forms) were identified in gut. The proportions of the heavy species dropped in malignant colon. Since muscarinic stimulation is needed for human colon cancer cell proliferation, the fall of ChE activity in neoplastic colon, with the increased availability of acetylcholine, may increase tumour growth.