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Cleavage of β-Catenin by Calpain in Prostate and Mammary Tumor Cells

2004; American Association for Cancer Research; Volume: 64; Issue: 20 Linguagem: Inglês

10.1158/0008-5472.can-04-1048

1538-7445

Jonathan Rios‐Doria, Rainer Kuefer, Stephen P. Ethier, Mark L. Day,

Hippo pathway signaling and YAP/TAZ

Abstract Mutations in the NH2-terminal regulatory domain of the β-catenin gene lead to aberrant stabilization and accumulation of the protein and increased TCF/LEF-dependent transcription. Although these mutations are common in some cancers, they are infrequent in prostate and breast cancer. We have found that metastatic prostate cancer specimens, obtained through a rapid autopsy tissue procurement program, expressed a novel Mr 75,000 proteolytic fragment of β-catenin (β-cat75). β-Cat75 was also expressed in multiple prostate and breast cancer cell lines and was closely associated with the activity of the calcium-dependent protease, calpain. In a prostate cancer cDNA microarray, m-calpain RNA levels were found to be significantly increased in metastatic disease compared with normal prostate. We showed calpain-dependent generation of β-cat75 in cell culture and in vitro. Molecular mapping revealed that calpain cleavage removed the NH2-terminal regulatory domain of the β-catenin protein. Treatment of MCF-7 cells with ionomycin led to increased accumulation of β-cat75 in the nucleus and TCF-dependent transcriptional activity. Overexpression of a similar β-catenin fragment that lacks the NH2-terminal 132 amino acids and has transforming potential activated TCF-dependent transcription. Given the low frequency of mutation-induced activation of β-catenin in prostate and breast cancers, proteolytic cleavage of β-catenin by calpain may represent a novel mechanism by which the protein is activated during tumorigenesis.