Faculty Collaboration Database

Reduced expression of Wnt-1 and E-cadherin, and diminished beta-catenin stability in MCF-7 breast cancer cells that overexpress protein kinase C-alpha. Int J Oncol 2001 Dec;19(6):1227-33

Date

11/20/2001

Pubmed ID

11713593

DOI

10.3892/ijo.19.6.1227

Scopus ID

2-s2.0-0035653457 (requires institutional sign-in at Scopus site)   7 Citations

Abstract

MCF-7 breast cancer cells stably overexpressing protein kinase C-alpha (MCF-7-PKC-alpha cells) exhibit reduced cell-cell adhesion and increased tumorigenicity in nude mice. We investigated the possibility that alterations in E-cadherin and catenins contribute to the unique phenotype of MCF-7-PKC-alpha cells. Northern and Western blotting indicated that MCF-7-PKC-alpha cells express abnormally low amounts of plakoglobin mRNA and protein, and undetectable levels of E-cadherin mRNA and protein. In contrast, even though MCF-7-PKC-alpha cells express low levels of beta-catenin mRNA, they express undetectable levels of beta-catenin protein, suggesting that post-transcriptional events further diminish beta-catenin expression in these cells. Pulse-labeling of the cells with [35S]methionine showed that the half-life of beta-catenin is less than 15 min in MCF-7-PKC-alpha cells, compared to over 2 h in MCF-7-Vector cells [MCF-7 cells transfected with pSV2M(2)6 vector only]. Incubation with LiCl to inactivate glycogen synthase kinase-3 (GSK-3) significantly prolonged the half-life of beta-catenin in MCF-7-PKC-alpha cells, suggesting that the GSK-3-dependent degradation of beta-catenin contributes to beta-catenin instability in these cells. Northern and Western blotting indicated that Wnt-1, which also inhibits GSK-3 activity, is expressed by MCF-7-Vector cells, but not by MCF-7-PKC-alpha cells. Transfection of (S37A)beta-catenin, which is resistant to GSK-3-dependent degradation, stimulated TCF/LEF-dependent luciferase expression from the pTOPFLASH reporter plasmid by 753-fold in MCF-7-PKC-alpha cells, and by 268-fold in MCF-7-Vector cells. Inactivation of GSK-3 by LiCl stimulated luciferase expression from the pTOPFLASH reporter plasmid by 12.4-fold in MCF-7-PKC-alpha cells, and by 4.8-fold in MCF-7-Vector cells. These results suggest that degradation of beta-catenin by GSK-3 contributes to beta-catenin instability in MCF-7-PKC-alpha cells, diminishing the ability of -catenin to act as a transcriptional co-activator. Reduced Wnt-1 expression by MCF-7-PKC-alpha cells may promote beta-catenin degradation by enhancing GSK-3 activity. Loss of beta-catenin-dependent cell-cell adhesion and transcription may contribute to the aggressive phenotype of MCF-7-PKC-alpha cells.

Author List

Williams CL, Noti JD

Author

Carol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Blotting, Northern
Breast Neoplasms
Cadherins
Cytoskeletal Proteins
Enzyme Stability
Female
Gene Expression
Humans
Isoenzymes
Luciferases
Luminescent Measurements
Protein Kinase C
Protein Kinase C-alpha
Proto-Oncogene Proteins
RNA, Messenger
Trans-Activators
Transcription, Genetic
Transcriptional Activation
Transfection
Tumor Cells, Cultured
Wnt Proteins
Wnt1 Protein
Zebrafish Proteins
beta Catenin