Cholinesterases are down-expressed in human colorectal carcinoma

The aberrations of cholinesterase (ChE) genes and the variation of ChE activity in cancerous tissues prompted us to investigate the expression of ChEs in colorectal carcinoma. The study of 55 paired specimens of healthy (HG) and cancerous gut (CG) showed that acetylcholinesterase (AChE) activity fell by 32% and butyrylcholinesterase (BuChE) activity by 58% in CG. Abundant AChE-H, fewer AChE-T, and even fewer AChE-R and BuChE mRNAs were observed in HG, and their content was greatly diminished in CG. The high level of the AChE-H mRNA explains the abundance of AChE-H subunits in HG, which as glycosylphosphatidylinositol (GPI)-anchored amphiphilic AChE dimers (G(2)(A)) and monomers (G(1)(A)) account for 69% of AChE activity. The identification of AChE-T and BuChE mRNAs justifies the occurrence in gut of A(12), G(4)(H) and PRiMA-containing G(4)(A) AChE forms, besides G(4)(H), G(4)(A) and G(1)(H) BuChE. The down-regulation of ChEs might contribute to gut carcinogenesis by increasing acetylcholine availability and over-stimulating muscarinic receptors.