A Ras homologue member I directly inhibits signal transducers and activators of transcription 3 translocation and activity in human breast and ovarian cancer cells

Arata Nishimoto, Yinhua Yu, Zhen Lu, Xiang Mao, Zhiyong Ren, Stephanie S. Watowich, Gordon Mills, Warren S.L. Liao, Xiaomin Chen, Robert C. Bast, Robert Z. Luo

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

A Ras homologue member I (ARHI) is a novel imprinted tumor suppressor gene whose expression is frequently lost in breast and ovarian cancers. This small GTP-binding protein is a member of the Ras superfamily with significant homology to both Ras and Rap. Unlike the Ras oncogene, however, ARHI inhibits tumor cell growth. To elucidate the mechanisms by which ARHI inhibits cancer growth, we screened a human breast epithelial cell cDNA library using a yeast two-hybrid system for ARHI-interacting proteins. ARHI was found to interact with signal transducers and activators of transcription (STAT) 3, a latent transcription factor that transduces signals from the cell surface to the nucleus and activates gene transcription. STAT3 is frequently phosphorylated and activated in breast and ovarian cancers, where cytokines and growth factors up-regulate STAT3 and stimulate proliferation. The ARHI-STAT3 interaction was confirmed by coimmunoprecipitation in mammalian cells and shown to be specific for STAT3 but not STAT1 or STAT5a. When ARHI and STAT3 were coexpressed in SKOv3 cells, ARHI formed a complex with STAT3 in the cytoplasm and prevented interleukln-6-induced STAT3 accumulation in the nucleus. ARHI markedly reduced STAT3 binding to DNA and STAT3-dependent promoter activity while only moderately affecting STAT3 phosphorylation. Deletion of the NH2 terminus of ARHI significantly compromised its inhibitory activity, suggesting that this unique NH 2-terminal extension contributes to ARHI's inhibition of STAT3-mediated transcriptional activity. Thus, the physical association between STAT3 and ARHI as well as the functional inhibition of STAT3 transcriptional activity by ARHI suggests a novel mechanism through which a putative tumor suppressor gene can inhibit STAT3 activity in breast and ovarian cancers.

Original languageEnglish (US)
Pages (from-to)6701-6710
Number of pages10
JournalCancer Research
Volume65
Issue number15
DOIs
StatePublished - Aug 1 2005
Externally publishedYes

Fingerprint

STAT3 Transcription Factor
Human Activities
Ovarian Neoplasms
Breast Neoplasms
Tumor Suppressor Genes
Two-Hybrid System Techniques
ras Genes
Growth
Gene Library
GTP-Binding Proteins
Neoplasms
Intercellular Signaling Peptides and Proteins
Cytoplasm
Breast
Transcription Factors
Up-Regulation
Epithelial Cells
Phosphorylation
Cytokines
Gene Expression

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

Cite this

A Ras homologue member I directly inhibits signal transducers and activators of transcription 3 translocation and activity in human breast and ovarian cancer cells. / Nishimoto, Arata; Yu, Yinhua; Lu, Zhen; Mao, Xiang; Ren, Zhiyong; Watowich, Stephanie S.; Mills, Gordon; Liao, Warren S.L.; Chen, Xiaomin; Bast, Robert C.; Luo, Robert Z.

In: Cancer Research, Vol. 65, No. 15, 01.08.2005, p. 6701-6710.

Research output: Contribution to journalArticle

Nishimoto, Arata ; Yu, Yinhua ; Lu, Zhen ; Mao, Xiang ; Ren, Zhiyong ; Watowich, Stephanie S. ; Mills, Gordon ; Liao, Warren S.L. ; Chen, Xiaomin ; Bast, Robert C. ; Luo, Robert Z. / A Ras homologue member I directly inhibits signal transducers and activators of transcription 3 translocation and activity in human breast and ovarian cancer cells. In: Cancer Research. 2005 ; Vol. 65, No. 15. pp. 6701-6710.
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T1 - A Ras homologue member I directly inhibits signal transducers and activators of transcription 3 translocation and activity in human breast and ovarian cancer cells

AU - Nishimoto, Arata

AU - Yu, Yinhua

AU - Lu, Zhen

AU - Mao, Xiang

AU - Ren, Zhiyong

AU - Watowich, Stephanie S.

AU - Mills, Gordon

AU - Liao, Warren S.L.

AU - Chen, Xiaomin

AU - Bast, Robert C.

AU - Luo, Robert Z.

PY - 2005/8/1

Y1 - 2005/8/1

N2 - A Ras homologue member I (ARHI) is a novel imprinted tumor suppressor gene whose expression is frequently lost in breast and ovarian cancers. This small GTP-binding protein is a member of the Ras superfamily with significant homology to both Ras and Rap. Unlike the Ras oncogene, however, ARHI inhibits tumor cell growth. To elucidate the mechanisms by which ARHI inhibits cancer growth, we screened a human breast epithelial cell cDNA library using a yeast two-hybrid system for ARHI-interacting proteins. ARHI was found to interact with signal transducers and activators of transcription (STAT) 3, a latent transcription factor that transduces signals from the cell surface to the nucleus and activates gene transcription. STAT3 is frequently phosphorylated and activated in breast and ovarian cancers, where cytokines and growth factors up-regulate STAT3 and stimulate proliferation. The ARHI-STAT3 interaction was confirmed by coimmunoprecipitation in mammalian cells and shown to be specific for STAT3 but not STAT1 or STAT5a. When ARHI and STAT3 were coexpressed in SKOv3 cells, ARHI formed a complex with STAT3 in the cytoplasm and prevented interleukln-6-induced STAT3 accumulation in the nucleus. ARHI markedly reduced STAT3 binding to DNA and STAT3-dependent promoter activity while only moderately affecting STAT3 phosphorylation. Deletion of the NH2 terminus of ARHI significantly compromised its inhibitory activity, suggesting that this unique NH 2-terminal extension contributes to ARHI's inhibition of STAT3-mediated transcriptional activity. Thus, the physical association between STAT3 and ARHI as well as the functional inhibition of STAT3 transcriptional activity by ARHI suggests a novel mechanism through which a putative tumor suppressor gene can inhibit STAT3 activity in breast and ovarian cancers.

AB - A Ras homologue member I (ARHI) is a novel imprinted tumor suppressor gene whose expression is frequently lost in breast and ovarian cancers. This small GTP-binding protein is a member of the Ras superfamily with significant homology to both Ras and Rap. Unlike the Ras oncogene, however, ARHI inhibits tumor cell growth. To elucidate the mechanisms by which ARHI inhibits cancer growth, we screened a human breast epithelial cell cDNA library using a yeast two-hybrid system for ARHI-interacting proteins. ARHI was found to interact with signal transducers and activators of transcription (STAT) 3, a latent transcription factor that transduces signals from the cell surface to the nucleus and activates gene transcription. STAT3 is frequently phosphorylated and activated in breast and ovarian cancers, where cytokines and growth factors up-regulate STAT3 and stimulate proliferation. The ARHI-STAT3 interaction was confirmed by coimmunoprecipitation in mammalian cells and shown to be specific for STAT3 but not STAT1 or STAT5a. When ARHI and STAT3 were coexpressed in SKOv3 cells, ARHI formed a complex with STAT3 in the cytoplasm and prevented interleukln-6-induced STAT3 accumulation in the nucleus. ARHI markedly reduced STAT3 binding to DNA and STAT3-dependent promoter activity while only moderately affecting STAT3 phosphorylation. Deletion of the NH2 terminus of ARHI significantly compromised its inhibitory activity, suggesting that this unique NH 2-terminal extension contributes to ARHI's inhibition of STAT3-mediated transcriptional activity. Thus, the physical association between STAT3 and ARHI as well as the functional inhibition of STAT3 transcriptional activity by ARHI suggests a novel mechanism through which a putative tumor suppressor gene can inhibit STAT3 activity in breast and ovarian cancers.

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