Volume 57, Issue 9 pp. 566-571

Increased wild-type p53-induced phosphatase 1 (Wip1 or PPM1D) expression correlated with downregulation of checkpoint kinase 2 in human gastric carcinoma

Takeichi Fuku

Takeichi Fuku

Division of Pathology, Department of Pathology and Microbiology, Kobe University Graduate School of Medicine, Kobe, Japan

Search for more papers by this author
Shuho Semba

Shuho Semba

Division of Pathology, Department of Pathology and Microbiology, Kobe University Graduate School of Medicine, Kobe, Japan

Search for more papers by this author
Hirokazu Yutori

Hirokazu Yutori

Division of Pathology, Department of Pathology and Microbiology, Kobe University Graduate School of Medicine, Kobe, Japan

Search for more papers by this author
Hiroshi Yokozaki

Hiroshi Yokozaki

Division of Pathology, Department of Pathology and Microbiology, Kobe University Graduate School of Medicine, Kobe, Japan

Search for more papers by this author
First published: 06 August 2007
Citations: 49
Shuho Semba, MD, PhD, Division of Pathology, Department of Pathology and Microbiology, Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan. Email: [email protected]

Abstract

Phosphorylation of checkpoint kinase 2 (Chk2) at Thr68 (pChk2) induced by DNA double-strand breaks is required for inhibition of cell cycle progression in the G2 phase. The purpose of the present paper was to investigate the expression of wild-type p53-induced phosphatase 1 (Wip1 or PPM1D), a negative regulator of Chk2, to better understand its role in human gastric cancer. In non-neoplastic gastric mucosa, most epithelial cells exhibited Wip1-positive and pChk2-negative immunoreactivity, whereas an inverse pattern of protein expression was detected at the surface of the foveolar epithelium. In tumor tissues, 74% of 53 gastric cancers had intense Wip1 immunoreactivity and close correlation with both tumor size (P = 0.0497) and Chk2 dephosphorylation (P = 0.0213). In MKN-74 gastric cancer cells, ionizing radiation (IR)-induced Wip1 upregulation was detected at protein levels, but the Chk2-mediated cell cycle regulatory mechanism was disrupted. In addition, protease inhibitor Z-Leu-Leu-Leu (ZLLL) effectively upregulated Wip1 levels in the presence or absence of IR, suggesting that Wip1 expression can be modulated post-transcriptionally. Understanding the Wip1-mediated signaling pathway in gastric cancer may provide useful information for the development of new chemo- and radiotherapies.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.