
<ArticleTitle>A functional screen for genes inducing <prot>epidermal growth factor</prot> autonomy of human mammary epithelial cells confirms the role of <prot>amphiregulin</prot>.</ArticleTitle>
<AbstractText>To gain better understanding of the molecular alterations responsible for the aggressive growth potential of <prot>epidermal growth factor receptor</prot> (<prot>EGFR</prot>)-positive breast cancers, we utilized an expression cloning strategy to seek gene products that mediate the <prot>EGF</prot>-independent growth of human breast cancer cells. A retroviral cDNA expression library was constructed from the <prot>EGFR</prot>-positive SUM-149PT cell line, and transduced into growth factor-dependent human mammary epithelial (HME) cells. Recipient cells were functionally selected for their ability to proliferate in serum-free, <prot>EGF</prot>-free medium. Library cDNAs were recovered from <prot>EGF</prot>-independent colonies by PCR amplification or by biological rescue. Clone H55a#1 contained a library insert encoding <prot>amphiregulin</prot>. This <prot>EGFR</prot> ligand was able to confer <prot>EGF</prot> independence when transduced into HME cells. SUM-149PT and H55a#1 cells overexpressed <prot>amphiregulin</prot> transcripts, and secreted moderate <prot>EGF</prot>-like activity in conditioned media, indicating a possible autocrine loop. <prot>EGFR</prot> membrane levels and constitutive phosphorylation were consistent with this hypothesis, as well as the sensitivity of the cells to an <prot>ErbB</prot>-specific kinase inhibitor. Expression of the <prot>WT1</prot> Wilms' tumor suppressor gene, a transcriptional activator of <prot>amphiregulin</prot>, did not parallel <prot>amphiregulin</prot> transcript levels, suggesting that another factor regulates <prot>amphiregulin</prot> in SUM-149PT. Our data confirm the importance of <prot>amphiregulin</prot> in the etiology of breast cancer.</AbstractText>
