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J Urol. 2004 Aug;172(2):723-7.

Inhibition of MKP-1 expression potentiates JNK related apoptosis in renal cancer cells.

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1
Department of Urology, Keio University School of Medicine, Tokyo, Japan.

Abstract

PURPOSE:

Mitogen-activated protein kinases (MAPKs) comprise 3 subgroups, that is extracellular signal-regulated protein kinase, c-Jun N-terminal kinase (JNK) and p38 MAPK (p38). In this study we analyzed the role of JNK as well as the expression of MAPK phosphatase-1 (MKP-1) in renal cancers.

MATERIALS AND METHODS:

Four renal cell carcinoma (RCC) cell lines were used. The effects of anisomycin (JNK activator) and Ro-318220 (MKP-1 expression inhibitor) were analyzed by alamar blue assay. Apoptosis was determined by flow cytometric TUNEL analysis, nuclear morphological alternations and the detection of DNA fragmentation. Changes in MKP-1 expression as well as the activation of extracellular signal-regulated protein kinases and JNK were analyzed by Western blotting.

RESULTS:

All cell lines treated with anisomycin resulted in a transient activation of JNK without inducing apoptosis. Since we hypothesized that elevated MKP-1 expression could possibly prevent persistent JNK activation, Ro-318220 was used. When cells were treated with Ro-318220, MKP-1 expression decreased in Caki-1 and KU 20-01 cells but not in ACHN or 769P cells. Combined treatment of Caki-1 and KU 20-01 cells with anisomycin and Ro-318220 resulted in a decrease in MKP-1 expression concomitant with persistent JNK activation. Apoptosis was induced in each cell line.

CONCLUSIONS:

These results suggest that prevalent MKP-1 expression in RCC contributes to cancer cell survival by attenuating an apoptosis inducing signal cascade via JNK. Since Ro-318220 potentiated JNK related apoptosis, JNK activation by blocking MKP-1 expression may be an effective therapeutic approach to RCC.

[Indexed for MEDLINE]

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