Cholinesterase Activity and Acetylcholinesterase Glycosylation are Altered in Human Breast Cancer

Abstract

Increasing evidence supports the involvement of cholinesterases in tumorigenesis. Several tumour cells show ChE activity, while the acetyl- (AChE) and butyrylcholinesterase (BuChE) genes are amplified in leukemias, ovarian carcinoma and other cancers. ChE activity was measured in 31 samples of tumoral breast (TB) and 20 of normal breast (NB). Despite the wide variations observed, BuChE predominated over AChE both in TB and NB. The mean AChE activity in NB was 1.61 nmol of the substrate hydrolysed per minute and per miligram protein (mU/mg), which rose to 3.09 mU/mg in TB (p = 0.041). The BuChE activity dropped from 5.24 mU/mg in NB to 3.39 mU/mg in TB (p = 0.002). Glycolipid-linked AChE dimers and monomers and hydrophilic BuChE tetramers and monomers were identified in NB and TB, and their proportions were unmodified by the neoplasia. The amount of AChE forms reacting with wheat germ agglutinin (WGA) decreased in TB while that of BuChE species was unaffected, demonstrating that the glycosylation of AChE was altered in TB. The binding of AChE and BuChE with antibodies was unaffected by the neoplasia. The difference in lectin reactivity between erythrocyte and breast AChE, the lack of AChE in blood plasma, and the finding of monomeric BuChE in breast but not in plasma suggest that breast epithelial cells produce AChE for membrane attachment and hydrophilic BuChE for secretion. Several reasons are provided to explain the altered expression of ChEs in breast cancer.

Acetylcholinesterase supports anchorage independence in colon cancer

“…The level of cell-substratum adhesion by neuronal cells directly correlates with the level of AChE expression [25]. Further, it has been suggested that breast epithelial cells may produce AChE for membrane attachment and hydrophilic BuChE for secretion [34]. Here we have shown the increased adhesion to Fibronectin of colon tumor cells overexpressing AChE.…”

Cholinesterases are down-expressed in human colorectal carcinoma

“…The percentage of each AChE form was estimated by comparing the AChE activity under each peak area and under the entire profile. The distinct migration of ChE components depending on the detergent (Brij 96 or Triton X-100) added to sucrose gradients showed their amphiphilic properties, which were further confirmed using hydrophobic chromatography in phenyl-agarose [18,19]. The asymmetric structure of 16.2S AChE was assessed by cleaving its ColQ tail with collagenase [20].…”

“…If the overexpression of AChE in Caco-2 cells is associated with differentiation, the under-expression may reflect the shifting of gut mucosal cells to a less differentiated state. The down-regulation of AChE and BuChE in colorectal carcinoma, the increase in AChE besides the drop in BuChE activity in breast cancer [18], the fall of AChE but not of BuChE activity in metastasized lymph nodes [20], and the variation of both activities in lung tumors depending on their histological features [15] indicate that the change in ChE activity depends on the kind of cell from which the tumor originates. This view agrees with the variable expression of AChE in proliferating cell systems, so that cell division is associated with up-regulation of AChE in mouse hematopoiesis (after transient blockade of its expression) [36], but with down-regulation in human hematopoiesis [37], megakaryocytopoiesis [38], and osteogenesis [8].…”

“…Extraction of HG and CG in two steps, the first with a detergent-free saline buffer (SB; 1 M NaCl, 50 mM MgCl 2 , 10 mM Tris, pH 7.0) and anti-proteinases [18], and the second with 1% Brij 96 in SB and anti-proteinases, allowed us to separately obtain loosely bound ChEs in the S1 supernatant and tightly bound ChEs in S2. ChE activity in homogenates and S1 and S2 extracts was assayed by the Ellman method, using suitable substrate and inhibitors to distinguish AChE and BuChE activities [18]. ChE activity is given in nmol of substrate split per min at 37 °C (mU).…”

“…AChE and BuChE molecules were separated by centrifugation analyses in sucrose gradient and characterized by their sedimentation coefficients [18]. Overlapping peaks in the sedimentation profiles were resolved by using the PEAK-FIT program from SPSS Inc.…”