Molecular cloning of hMena (ENAH) and its splice variant hMena+11a: epidermal growth factor increases their expression and stimulates hMena+11a phosphorylation in breast cancer cell lines.

Abstract

hMena (ENAH), an actin regulatory protein involved in the control of cell motility and adhesion, is modulated during human breast carcinogenesis. In fact, whereas undetectable in normal mammary epithelium, hMena becomes overexpressed in high-risk benign lesions and primary and metastatic tumors. In vivo, hMena overexpression correlates with the HER-2(+)/ER(-)/Ki67(+) unfavorable prognostic phenotype. In vitro, neuregulin-1 up-regulates whereas Herceptin treatment down-modulates hMena expression, suggesting that it may couple tyrosine kinase receptor signaling to the actin cytoskeleton. Herein, we report the cloning of hMena and of a splice variant, hMena(+11a), which contains an additional exon corresponding to 21 amino acids located in the EVH2 domain, from a breast carcinoma cell line of epithelial phenotype. Whereas hMena overexpression consistently characterizes the transformed phenotype of tumor cells of different lineages, hMena(+11a) isoform is concomitantly present only in epithelial tumor cell lines. In breast cancer cell lines, epidermal growth factor (EGF) treatment promotes concomitant up-regulation of hMena and hMena(+11a), resulting in an increase of the fraction of phosphorylated hMena(+11a) isoform only. hMena(+11a) overexpression and phosphorylation leads to increased p42/44 mitogen-activated protein kinase (MAPK) activation and cell proliferation as evidenced in hMena(+11a)-transfected breast cancer cell lines. On the contrary, hMena knockdown induces reduction of p42/44 MAPK phosphorylation and of the proliferative response to EGF. The present data provide new insight into the relevance of actin cytoskeleton regulatory proteins and, in particular, of hMena isoforms in coupling multiple signaling pathways involved in breast cancer.

• Authors: Francesca Di Modugno, Lucia DeMonte, Michele Balsamo, Giovanna Bronzi, Maria Rita Nicotra, Massimo Alessio, Elke Jager, John S Condeelis, Angela Santoni, Pier Giorgio Natali, Paola Nisticò
• Journal: Cancer research (Cancer Res) Vol. 67 Issue 6 Pg. 2657-65 (Mar 15 2007) ISSN: 0008-5472 [Print] United States
• PMID: 17363586 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Enah protein, human
• Microfilament Proteins
• Protein Isoforms
• Epidermal Growth Factor
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3

Topics

• Amino Acid Sequence
• Breast Neoplasms (enzymology, genetics, metabolism, pathology)
• Cell Growth Processes (physiology)
• Cell Line, Tumor
• Cloning, Molecular
• Enzyme Activation
• Epidermal Growth Factor (pharmacology)
• Humans
• Microfilament Proteins (biosynthesis, genetics, metabolism)
• Mitogen-Activated Protein Kinase 1 (metabolism)
• Mitogen-Activated Protein Kinase 3 (metabolism)
• Molecular Sequence Data
• Phosphorylation (drug effects)
• Protein Isoforms
• Up-Regulation (drug effects)