Transcriptome of RA-responsive and RA-resistant breast cancer cell lines

Retinoic acid (RA), the main active vitamin A metabolite, controls multiple biological processes such as cell proliferation and differentiation through genomic programs and kinase cascades activation. Several breast cancer cells respond to the antiproliferative effects of RA, but others are RA-resistant. In several cases resistance has been correlated to the amplification of the erb-b2 receptor tyrosine kinase 2 (ERBB2) gene, but the overall signaling and transcriptional pathways that are altered in such cells have not been elucidated. Here we compared two human breast cancer cell lines, the MCF7 cell line, which responds to the antiproliferative action of RA and the BT474 cell line, which is RA-resistant subsequent to ERBB2 amplification in a large-scale analysis of the phosphoproteins and in a genome-wide analysis of the RA-regulated genes. Using high-resolution nano-LC-LTQ-Orbitrap mass spectrometry associated to phosphopeptide enrichment, we found that several proteins involved in signaling and in transcription, are differentially phosphorylated after RA addition. The paradigm of these proteins is the RA receptor a (RARa), which was phosphorylated in MCF7 cells but not in BT474 cells. The panel of the RA-regulated genes was also different. Overall our results indicate that ERBB2 amplification interferes with the ability of RA to activate kinases with consequences on the phosphorylation of several proteins involved in transcription and thus on gene expression. Overall design: Two human breast cancer cell lines were compared for their repertoire of genes regulated by retinoic acid (RA): the RA sensitive MCF7 cell line and the RA resistant B7474 cell line

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Carrier M, Joint M, Lutzing R, Page A, Rochette-Egly C