The ubiquitin ligase CHIP acts as an upstream regulator of oncogenic pathways

• Published in: Nature cell biology Vol. 11; no. 3; pp. 312 - 319
• Main Authors: Yanagisawa, Junn, Kajiro, Masashi, Hirota, Ryuichi, Nakajima, Yuka, Kawanowa, Kaori, So-ma, Kae, Ito, Ichiaki, Yamaguchi, Yuri, Ohie, Sho-hei, Kobayashi, Yasuhito, Seino, Yuko, Kawano, Miwako, Kawabe, Yoh-ichi, Takei, Hiroyuki, Hayashi, Shin-ichi, Kurosumi, Masafumi, Murayama, Akiko, Kimura, Keiji
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2009; Nature Publishing Group
• Subjects: Animals; Biomedical and Life Sciences; Breast cancer; Breast Neoplasms - enzymology; Breast Neoplasms - genetics; Breast Neoplasms - pathology; Cancer Research; Cell Biology; Cell Transformation, Neoplastic; Developmental Biology; Down-Regulation; Female; Gene Expression Regulation, Neoplastic; Histone Acetyltransferases - metabolism; Humans; Invasiveness; letter; Life Sciences; Ligases; Lung Neoplasms - secondary; Messenger RNA; Mice; Nuclear Receptor Coactivator 3; Physiological aspects; Protein Processing, Post-Translational; Proteins; Stem Cells; Trans-Activators - metabolism; Tumor proteins; Tumors; Ubiquitin-Protein Ligases - metabolism; Ubiquitination; Xenograft Model Antitumor Assays; Japan
• ISSN: 1465-7392; 1476-4679
• DOI: 10.1038/ncb1839

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.