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International Journal of Breast Cancer
Volume 2017 (2017), Article ID 4537532, 6 pages
Research Article

P-Rex1 Expression in Invasive Breast Cancer in relation to Receptor Status and Distant Metastatic Site

1Department of Pathology & Laboratory Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
2Comprehensive Breast Program, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
3Department of Biomedical Data Science, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
4Department of Molecular & Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA

Correspondence should be addressed to Todd W. Miller

Received 17 February 2017; Accepted 7 May 2017; Published 15 June 2017

Academic Editor: Debra A. Tonetti

Copyright © 2017 Jonathan D. Marotti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. Phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-Rex1) has been implicated in cancer growth, metastasis, and response to phosphatidylinositol 3-kinase (PI3K) inhibitor therapy. The aim of this study was to determine whether P-Rex1 expression differs between primary and metastatic human breast tumors and between breast cancer subtypes. Design. P-Rex1 expression was measured in 133 specimens by immunohistochemistry: 40 and 42 primary breast tumors from patients who did versus did not develop metastasis, respectively, and 51 breast-derived tumors from metastatic sites (36 of which had matching primary tumors available for analysis). Results. Primary breast tumors showed significant differences in P-Rex1 expression based on receptor subtype. ER+ and HER2+ primary tumors showed higher P-Rex1 expression than primary triple-negative tumors. HER2+ metastases from all sites showed significantly higher P-Rex1 expression compared to other metastatic receptor subtypes. Solid organ (i.e., brain, lung, and liver) metastases showed higher P-Rex1 expression compared to bone metastases. Conclusions. P-Rex1 expression is increased in ER+ and HER2+ breast cancers compared to triple-negative tumors. P-Rex1 may be differentially expressed in metastatic tumors based on site and receptor status. The role of P-Rex1 in the development of breast cancer metastases and as a predictive biomarker of therapeutic response warrants further investigation.