38P - Retinoic acid signaling in human breast cancer cells: A phosphoproteomic approach

Date 07 May 2015
Event IMPAKT 2015
Session Welcome reception and Poster Walk
Topics Breast Cancer
Translational Research
Presenter Marilyn Carrier
Citation Annals of Oncology (2015) 26 (suppl_3): 10-14. 10.1093/annonc/mdv116
Authors M. Carrier1, M. Joint2, R. Lutzing1, A. Page2, C. Rochette-Egly1
  • 1Functional Genomics And Cancer, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67404 - Illkirch/FR
  • 2Proteomic Platform, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67404 - Illkirch/FR



Breast cancer is a heterogeneous disease with ∼30 % of the breast tumors characterized by the overexpression of the receptor tyrosine kinase erbB-2. Most of these erbB-2 tumors depict aberrant kinase signaling activities and are resistant to the anti-proliferative action of retinoic acid (RA). Interestingly, our laboratory has previously shown that the RA-dependent transcriptional activity of the retinoic acid receptors (RARs) is tightly regulated by phosphorylation and that RA itself is involved in the regulation of RARs phosphorylation via the activation of kinase cascades. Moreover, RA induces the degradation of RARs and this mechanism is believed to mark the end of the transcriptional signal. Therefore we addressed whether erbB-2 overexpression affects the general phosphoprotein networks involved in the response to RA, the phosphorylation state of RARs and their degradation in response to the ligand. We compared the phosphoproteome of two different human breast cancer cell lines (the erbB-2 negative MCF7 cell line and the erbB-2 positive BT474 cell line) by high-resolution nano LC/Orbitrap Mass Spectrometry after IMAC enrichment of the phosphopeptides. This highlighted several differences in the basal phosphoproteome of the two cell lines and RA treatment revealed important response discrepancies. As the low abundance of RARα prevented its detection by this method, we performed phosphomapping analysis in MCF7 and BT474 using mass spectrometry approaches coupled to prior large-scale immunoprecipitation of RARα. Intriguingly, we identified two unreported phosphorylation sites and one of them showed a strong induction by RA in the MCF7 cell line, but not in the BT474 cell line. Finally, RA induced a strong RARα degradation in MCF7 cells, but had a weaker effect in BT474 cells. The erbB-2 -targeting drug trastuzumab however restored efficient RA-induced RARα degradation in BT474 cells. Taken together, our results provide new insights into the aberrant RA signaling in the context of erbB-2 -positive breast cancer.

Disclosure: All authors have declared no conflicts of interest.