The ubiquitin ligase CHIP acts as an upstream regulator of oncogenic pathways.
CHIP is a U-box-type ubiquitin ligase that induces ubiquitylation and degradation of its substrates, which include several oncogenic proteins. The relationship between CHIP and tumour progression, however, has not been elucidated. Here, we show that CHIP suppresses tumour progression in human breast cancer by inhibiting oncogenic pathways. CHIP levels were negatively correlated with the malignancy of human breast tumour tissues. In a nude mouse xenograft model, tumour growth and metastasis were significantly inhibited by CHIP expression. In contrast, knockdown of CHIP (shCHIP) in breast cancer cells resulted in rapid tumour growth and metastastic phenotypes in mice. In cell-based experiments, anchorage-independent growth and invasiveness of shCHIP cells was significantly elevated due to increased expression of Bcl2, Akt1, Smad and Twist. Proteomic analysis identified the transcriptional co-activator SRC-3 (refs 13, 14, 15, 16, 17, 18, 19) as a direct target for ubiquitylation and degradation by CHIP. Knocking down SRC-3 in shCHIP cells reduced the expression of Smad and Twist, and suppressed tumour metastasis in vivo. Conversely, SRC-3 co-expression prevented CHIP-induced suppression of metastasis formation. These observations demonstrate that CHIP inhibits anchorage-independent cell growth and metastatic potential by degrading oncogenic proteins including SRC-3.
Kajiro
Masashi
M
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba Science City, Ibaraki 305-8572, Japan.
Hirota
Ryuichi
R
Nakajima
Yuka
Y
Kawanowa
Kaori
K
So-ma
Kae
K
Ito
Ichiaki
I
Yamaguchi
Yuri
Y
Ohie
Sho-hei
SH
Kobayashi
Yasuhito
Y
Seino
Yuko
Y
Kawano
Miwako
M
Kawabe
Yoh-ichi
Y
Takei
Hiroyuki
H
Hayashi
Shin-ichi
S
Kurosumi
Masafumi
M
Murayama
Akiko
A
Kimura
Keiji
K
Yanagisawa
Junn
J
D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002471:Cell Transformation, Neoplastic; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D051548:Histone Acetyltransferases / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000556:secondary; D051379:Mice; D056921:Nuclear Receptor Coactivator 3; D011499:Protein Processing, Post-Translational; D015534:Trans-Activators / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination; D023041:Xenograft Model Antitumor Assays
D015534:Trans-Activators; D051548:Histone Acetyltransferases; C538866:NCOA3 protein, human; C538867:Ncoa3 protein, mouse; D056921:Nuclear Receptor Coactivator 3; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases