Growth Differentiation Factor 15 (GDF15)-Mediated HER2 Phosphorylation Reduces Trastuzumab Sensitivity of HER2-Overexpressing Breast Cancer Cells

• Type of Material: Article
• Authors: Jayashree P. Joshi, Emory University; Nicole E. Brown, Emory University; Samantha E. Griner, Emory University; Rita Nahta, Emory University
• Language: English
• Date: 2011-11-01
• Publisher: Elsevier: 12 months
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2011 Elsevier Inc. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.bcp.2011.07.082
• Title of Journal or Parent Work: Biochemical Pharmacology
• ISSN: 0006-2952
• Volume: 82
• Issue: 9
• Start Page: 1090
• End Page: 1099
• Grant/Funding Information: R. Nahta gratefully acknowledges funding from The Mary Kay Foundation, The Georgia Cancer Coalition Distinguished Cancer Scholars Program, and NIH K01CA118174.
• Keywords: trastuzumab; erbB2; resistance; lapatinib; breast cancer; Herceptin
• Research Categories: Health Sciences, Pharmacology; Health Sciences, Oncology

Abstract

Resistance to the anti-HER2 monoclonal antibody trastuzumab is a major problem in the treatment of HER2-overexpressing metastatic breast cancer. Growth differentiation factor 15 (GDF15), which is structurally similar to TGF beta, has been reported to stimulate phosphorylation of HER2. We tested the hypothesis that GDF15-mediated phosphorylation of HER2 reduces the sensitivity of HER2-overexpressing breast cancer cell lines to trastuzumab. Gene microarray analysis, real-time PCR, and ELISA were used to assess GDF15 expression. Growth inhibition and proliferation assays in response to pharmacologic inhibitors of HER2, TGF beta receptor, or Src were performed on cells stimulated with recombinant human GDF15 or stable GDF15 transfectants. Western blotting was performed to determine effects of GDF15 on HER2 signaling. Cells were infected with lentiviral GDF15 shRNA plasmid to determine effects of GDF15 knockdown on cell survival in response to trastuzumab. Cells with acquired or primary trastuzumab resistance showed increased GDF15 expression. Exposure of trastuzumab-sensitive cells to recombinant human GDF15 or stable transfection of a GDF15 expression plasmid inhibited trastuzumab-mediated growth inhibition. HER2 tyrosine kinase inhibition abrogated GDF15-mediated Akt and Erk1/2 phosphorylation and blocked GDF15-mediated trastuzumab resistance. Pharmacologic inhibition of TGF beta receptor blocked GDF15-mediated phosphorylation of Src. Further, TGF beta receptor inhibition or Src inhibition blocked GDF15-mediated trastuzumab resistance. Finally, lentiviral GDF15 shRNA increased trastuzumab sensitivity in cells with acquired or primary trastuzumab resistance. These results support GDF15-mediated activation of TGF beta receptor-Src-HER2 signaling crosstalk as a novel mechanism of trastuzumab resistance.