Combination inhibition of PI3K and mTORC1 yields durable remissions in mice bearing orthotopic patient-derived xenografts of HER2-positive breast cancer brain metastases

Jing Ni, Shakti H. Ramkissoon, Shaozhen Xie, Shom Goel, Daniel G. Stover, Hanbing Guo, Victor Luu, Eugenio Marco, Lori A. Ramkissoon, Yun Jee Kang, Marika Hayashi, Quang De Nguyen, Azra H. Ligon, Rose Du, Elizabeth B. Claus, Brian M. Alexander, Guo Cheng Yuan, Zhigang C. Wang, J. Dirk Iglehart, Ian E. KropThomas M. Roberts, Eric P. Winer, Nancy U. Lin, Keith L. Ligon, Jean J. Zhao

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94 Scopus citations

Abstract

Brain metastases represent the greatest clinical challenge in treating HER2-positive breast cancer. We report the development of orthotopic patient-derived xenografts (PDXs) of HER2-expressing breast cancer brain metastases (BCBM), and their use for the identification of targeted combination therapies. Combined inhibition of PI3K and mTOR resulted in durable tumor regressions in three of five PDXs, and therapeutic response was correlated with a reduction in the phosphorylation of 4EBP1, an mTORC1 effector. The two nonresponding PDXs showed hypermutated genomes with enrichment of mutations in DNA-repair genes, which suggests an association of genomic instability with therapeutic resistance. These findings suggest that a biomarker-driven clinical trial of PI3K inhibitor in combination with an mTOR inhibitor should be conducted for patients with HER2-positive BCBM.

Original languageEnglish
Pages (from-to)723-726
Number of pages4
JournalNature Medicine
Volume22
Issue number7
DOIs
StatePublished - 1 Jul 2016
Externally publishedYes

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