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


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.
Mizuno
Ryuichi
R
Department of Urology, Keio University School of Medicine, Tokyo, Japan.
Oya
Mototsugu
M
Shiomi
Takayuki
T
Marumo
Ken
K
Okada
Yasunori
Y
Murai
Masaru
M
D000841:Anisomycin / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology; D002292:Carcinoma, Renal Cell / Q000378:metabolism* / Q000473:pathology; D018797:Cell Cycle Proteins; D054638:Dual Specificity Phosphatase 1; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D007211:Indoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D054645:Protein Phosphatase 1; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured
D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D007211:Indoles; D011500:Protein Synthesis Inhibitors; D000841:Anisomycin; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases; C064758:Ro 31-8220