Oncotarget

Research Papers:

KLF4α stimulates breast cancer cell proliferation by acting as a KLF4 antagonist

Jacqueline Ferralli, Ruth Chiquet-Ehrismann and Martin Degen _

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Oncotarget. 2016; 7:45608-45621. https://doi.org/10.18632/oncotarget.10058

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Abstract

Jacqueline Ferralli1, Ruth Chiquet-Ehrismann1,2, Martin Degen1,3

1Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, Basel, Switzerland

2Faculty of Science, University of Basel, Basel, Switzerland

3Department of Orthodontics and Dentofacial Orthopedics, School of Dental Medicine, University of Bern, Bern, Switzerland

Correspondence to:

Martin Degen, email: martin.degen@zmk.unibe.ch

Keywords: alternative splicing, KLF4, KLF4α/KLF4(FL) ratio, proliferation, tumors

Received: March 29, 2016     Accepted: June 03, 2016     Published: June 15, 2016

ABSTRACT

Krüppel-like factor 4 (KLF4), a transcription factor involved in both tumor suppression and oncogenesis in various human tumors, is subject to alternative splicing that produces KLF4α. KLF4α is primarily expressed in the cytoplasm because it lacks exon 3 of KLF4, which contains the nuclear localization signal. The role of KLF4 in breast cancer remains unclear and nothing is known yet about the expression and function of the isoform KLF4α. Here, we show that KLF4α is expressed in normal and tumoral tissue of the breast and provide evidence that the KLF4α/KLF4(full-length) (FL) ratio is increased in tumors compared to corresponding normal tissue. Forced increase of the KLF4α/KLF4(FL) ratio in the metastatic breast cancer cell line MDA-MB-231 decreases the levels of E-Cadherin, p21Cip1, and p27Kip1, three known KLF4(FL) target genes, and stimulates cell proliferation. We suggest that cytoplasmic KLF4α binds to KLF4(FL) and retains it in the cytoplasm thereby antagonizing the gene regulatory activities of KLF4(FL) in the nucleus. Our results establish KLF4α as a KLF4 isoform that opposes the function of KLF4(FL) and as an important factor in the complex and unresolved role of KLF4(FL) in breast carcinogenesis.


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