microRNA-205 Regulates HER3 in Human Breast Cancer

¹Molecular Biology Unit, Department of Experimental Oncology, Fondazione Istituto Di Ricovero e Cura a Carattere Scientifico, Istituto Nazionale Tumori, Milano, Italy and ²Department of Molecular Virology, Immunology and Medical Genetics and Comprehensive Cancer Center, Ohio State University, Columbus, Ohio

^* To whom correspondence should be addressed. E-mail: Carlo.Croce{at}osumc.edu.

	Abstract

An increasing amount of experimental evidence shows that microRNAs can have a causal role in breast cancer tumorigenesis as a novel class of oncogenes or tumor suppressor genes, depending on the targets they regulate. HER2 overexpression is a hallmark of a particularly aggressive subset of breast tumors, and its activation is strictly dependent on the trans-interaction with other members of HER family; in particular, the activation of the PI3K/Akt survival pathway, so critically important in tumorigenesis, is predominantly driven through phosphorylation of the kinase-inactive member HER3. Here, we show that miR-205, down-modulated in breast tumors compared with normal breast tissue, directly targets HER3 receptor, and inhibits the activation of the downstream mediator Akt. The reintroduction of miR-205 in SKBr3 cells inhibits their clonogenic potential and increases the responsiveness to tyrosine-kinase inhibitors Gefitinib and Lapatinib, abrogating the HER3-mediated resistance and restoring a potent proapoptotic activity. Our data describe miR-205 as a new oncosuppressor gene in breast cancer, able to interfere with the proliferative pathway mediated by HER receptor family. Our study also provides experimental evidence suggesting that miR-205 can improve the responsiveness to specific anticancer therapies. [Cancer Res 2009;69(6):2195–200]

Key Words: microRNAs, human breast cancer, HER3 receptor

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