LYN-activating mutations mediate antiestrogen resistance in estrogen receptor-positive breast cancer

• Authors: Luis J. Schwarz, Vanderbilt University; Emily M. Fox, Vanderbilt University; Justin M. Balko, Vanderbilt University; Joan T. Garrett, Vanderbilt University; Maria G. Kuba, Vanderbilt University; Monica V. Estrada, Vanderbilt University; Ana Maria Gonzalez-Angulo, University of Texas MD Anderson Cancer Center; Gordon B. Mills, University of Texas MD Anderson Cancer Center; Monica Red-Brewer, Vanderbilt University; Ingrid A. Mayer, Vanderbilt University; Vandana Abramson, Vanderbilt University; Monica Rizzo, Emory University; Mark C. Kelley, Vanderbilt University; Ingrid M. Meszoely, Vanderbilt University; Carlos L. Arteaga, Vanderbilt University
• Journal Title: Journal of Clinical Investigation
• Volume: Volume 124, Number 12
• Publisher: American Society for Clinical Investigation | 2014-12-01, Pages 5490-5502
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1172/JCI72573
• Subjects: Health Sciences, Immunology; Health Sciences, Oncology
• Keywords: Science & Technology; Life Sciences & Biomedicine; Medicine, Research & Experimental; Research & Experimental Medicine; SRC FAMILY KINASES; PHOSPHATIDYLINOSITOL 3-KINASE; PHOSPHOINOSITIDE 3-KINASE; NEOADJUVANT TREATMENT; AROMATASE INHIBITION; THERAPEUTIC TARGET; ENDOCRINE THERAPY; IN-VIVO; CELLS; TAMOXIFEN

Abstract

Estrogen receptor-positive (ER+) breast cancers adapt to hormone deprivation and become resistant to antiestrogen therapy. Here, we performed deep sequencing on ER+ tumors that remained highly proliferative after treatment with the aromatase inhibitor letrozole and identified a D189Y mutation in the inhibitory SH2 domain of the SRC family kinase (SFK) LYN. Evaluation of 463 breast tumors in The Cancer Genome Atlas revealed four LYN mutations, two of which affected the SH2 domain. In addition, LYN was upregulated in multiple ER+ breast cancer lines resistant to long-term estrogen deprivation (LTED). An RNAi-based kinome screen revealed that LYN is required for growth of ER+ LTED breast cancer cells. Kinase assays and immunoblot analyses of SRC substrates in transfected cells indicated that LYND189Y has higher catalytic activity than WT protein. Further, LYND189Y exhibited reduced phosphorylation at the inhibitory Y507 site compared with LYNWT. Other SH2 domain LYN mutants, E159K and K209N, also exhibited higher catalytic activity and reduced inhibitory site phosphorylation. LYND189Y overexpression abrogated growth inhibition by fulvestrant and/or the PI3K inhibitor BKM120 in 3 ER+ breast cancer cell lines. The SFK inhibitor dasatinib enhanced the antitumor effect of BKM120 and fulvestrant against estrogen-deprived ER+ xenografts but not LYND189Y-expressing xenografts. These results suggest that LYN mutations mediate escape from antiestrogens in a subset of ER+ breast cancers.