Elevated Expression of the cdc25A Protein Phosphatase in Colon Cancer

• Published in: Experimental cell research Vol. 240; no. 2; pp. 236 - 243
• Main Authors: Dixon, Dora, Moyana, Terence, King, Martin J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.1998
• Subjects: Animals; cdc25 Phosphatases; cdc25A; colon cancer; Colonic Neoplasms - chemically induced; Colonic Neoplasms - enzymology; Disease Models, Animal; Epithelial Cells - enzymology; mitotic index; nuclei; phosphotyrosyl protein phosphatase; Protein Tyrosine Phosphatases - metabolism; Rats; Rats, Sprague-Dawley; nuclei; cdc25A; mitotic index; phosphotyrosyl protein phosphatase; colon cancer
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1006/excr.1998.3940

The nuclear protein phosphatase cdc25A has been postulated to be a protooncogene. The total nuclear phosphotyrosyl protein phosphatase (PTP) activity and the expression of cdc25A were compared in normal and cancerous colon epithelial tissue. Nuclei derived from normal mucosal epithelium and tumors were analyzed for phosphotyrosyl protein phosphatase activity using the malachite green assay and a synthetic phosphotyrosyl peptide based on the sequence of cdc2, a known cdc25A phosphotyrosyl protein substrate. Tumorigenesis resulted in elevated nuclear PTP activity (343.0 ± 37.0% of normal epithelial PTP activity) in 52% (29 of 56) of colon tumors. In all cases elevated nuclear PTP activity correlated with an increase in the expression of cdc25A. The changes in PTP activity observed were not due to any increase in the rate of growth of the colonic mucosa as no corresponding changes occurred with PTP activity under conditions of rapid mucosal growth.