Skp2 regulates subcellular localization of PPARγ by MEK signaling pathways in human breast cancer.
Nuclear hormone receptor family member PPARγ plays an important role in mammary gland tumorigenesis. Previous studies have shown PPARγ has cytoplasmic activities upon tetradecanoyl phorbol acetate (TPA) stimulation. However, the clinical pathological significance of cytoplasmic PPARγ is not completely understood in human breast cancer. Skp2 is oncogenic, and its frequent amplification and overexpression correlated with the grade of malignancy. In this study, the role of cytoplasmic PPARγ and Skp2 expression was investigated in human breast cancer progression. Therefore, immunohistochemical analysis was performed on formalin-fixed paraffin sections of 70 specimens. Furthermore, Western blot and immunofluorescence microscopy analysis were used to study the relationship between expression of cytoplasmic PPARγ and Skp2 expression in human breast cancer cells in vitro. Results showed that the expression of cytoplasmic PPARγ was positively correlated with Skp2 expression (p < 0.05), and correlated significantly with estrogen receptor (p = 0.026) and pathological grade (p = 0.029), respectively. In addition, Skp2 overexpression can provoke cytoplasmic localization of PPARγ upon MEK1-dependent mechanisms in human breast cancer cells by nuclear-cytosolic fractionation technology and immunofluorescence microscopy analysis. Using RNA interference technology, we also found that down-regulated Skp2 reduced the phosphorylation level of MEK1 and significantly reversed TPA-induced nuclear export of PPARγ in MDA-MB-231 cells. The changes in the subcellular localization of PPARγ may represent a novel target for selective interference in patients with breast cancer.
Department of Laboratory Science, the Fourth Hospital Affiliated to Guangxi Medical University, Liuzhou 545005, Guangxi, China. ge_ge_bu_ru@sina.com
Hongge
H
Cheng
Jie
J
Meng
Guisheng
G
Wang
Yuming
Y
Meng
Yu
Y
Li
Dong
D
Wei
Chunyun
C
Fu
Kaifeng
K
Deng
Aiguo
A
Shen
Huimin
H
Wang
Shengming
S
Dai
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D061986:MCF-7 Cells; D009570:Nitriles / Q000494:pharmacology; D047495:PPAR gamma / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009570:Nitriles; D047495:PPAR gamma; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D044786:S-Phase Kinase-Associated Proteins; C113580:U 0126; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one