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CNK1 is a novel Akt interaction partner that promotes cell proliferation through the Akt-FoxO signalling axis.


Fritz, R D; Varga, Z; Radziwill, G (2010). CNK1 is a novel Akt interaction partner that promotes cell proliferation through the Akt-FoxO signalling axis. Oncogene, 29(24):3575-3582.

Abstract

The scaffold proteins connector enhancer of KSR (CNK) participate in Raf-, Rho- and NF-kappaB-dependent signalling and promote cell differentiation and invasion. In this study, we demonstrate that CNK1 downregulation inhibits, whereas CNK1 overexpression stimulates the proliferation of breast cancer cells and human embryonic kidney cells, respectively. This stimulatory effect depends on a functional phosphatidylinositol-3 kinase (PI3K) pathway because treatment of cells with the PI3K inhibitor, LY294002, abrogates CNK1-induced proliferation. CNK1 interacts with the PI3K effector Akt and knockdown of CNK1 decreases Akt activity in breast cancer cells. CNK1 controls Akt-dependent phosphorylation and transcriptional activity of FoxO, which is a negative regulator of proliferation. Consistent with this, CNK1-induced cell proliferation is blocked by FoxO overexpression. Moreover, CNK1 regulates anchorage-independent proliferation and focus formation of breast cancer cells. CNK1 is predominantly localized at the plasma membrane of breast cancer cells, whereas in non-transformed mammary epithelial cells, CNK1 is cytoplasmatic. Accordingly, CNK1 is found preferentially at the plasma membrane in carcinoma in situ and invasive breast cancer tumours compared with normal breast tissue sections. Analysis of multiple breast cancer samples reveals that CNK1-negative tumours show less Akt activity. Thus, CNK1 promotes oncogenic signalling through Akt in breast cancer cell lines and tumours.

Abstract

The scaffold proteins connector enhancer of KSR (CNK) participate in Raf-, Rho- and NF-kappaB-dependent signalling and promote cell differentiation and invasion. In this study, we demonstrate that CNK1 downregulation inhibits, whereas CNK1 overexpression stimulates the proliferation of breast cancer cells and human embryonic kidney cells, respectively. This stimulatory effect depends on a functional phosphatidylinositol-3 kinase (PI3K) pathway because treatment of cells with the PI3K inhibitor, LY294002, abrogates CNK1-induced proliferation. CNK1 interacts with the PI3K effector Akt and knockdown of CNK1 decreases Akt activity in breast cancer cells. CNK1 controls Akt-dependent phosphorylation and transcriptional activity of FoxO, which is a negative regulator of proliferation. Consistent with this, CNK1-induced cell proliferation is blocked by FoxO overexpression. Moreover, CNK1 regulates anchorage-independent proliferation and focus formation of breast cancer cells. CNK1 is predominantly localized at the plasma membrane of breast cancer cells, whereas in non-transformed mammary epithelial cells, CNK1 is cytoplasmatic. Accordingly, CNK1 is found preferentially at the plasma membrane in carcinoma in situ and invasive breast cancer tumours compared with normal breast tissue sections. Analysis of multiple breast cancer samples reveals that CNK1-negative tumours show less Akt activity. Thus, CNK1 promotes oncogenic signalling through Akt in breast cancer cell lines and tumours.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Medical Virology
04 Faculty of Medicine > University Hospital Zurich > Institute of Pathology and Molecular Pathology
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:June 2010
Deposited On:14 May 2010 23:06
Last Modified:07 Dec 2017 02:10
Publisher:Nature Publishing Group
ISSN:0950-9232
Publisher DOI:https://doi.org/10.1038/onc.2010.104
PubMed ID:20383191

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