Combined SFK/MEK inhibition prevents metastatic outgrowth of dormant tumor cells
Lara H. El Touny, … , Mark J. Hoenerhoff, Jeffrey E. Green
Lara H. El Touny, … , Mark J. Hoenerhoff, Jeffrey E. Green
Published December 9, 2013
Citation Information: J Clin Invest. 2014;124(1):156-168. https://doi.org/10.1172/JCI70259.
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Research Article Oncology

Combined SFK/MEK inhibition prevents metastatic outgrowth of dormant tumor cells

Abstract

Breast cancer (BC) can recur as metastatic disease many years after primary tumor removal, suggesting that disseminated tumor cells survive for extended periods in a dormant state that is refractory to conventional therapies. We have previously shown that altering the tumor microenvironment through fibrosis with collagen and fibronectin deposition can trigger tumor cells to switch from a dormant to a proliferative state. Here, we used an in vivo preclinical model and a 3D in vitro model of dormancy to evaluate the role of Src family kinase (SFK) in regulating this dormant-to-proliferative switch. We found that pharmacological inhibition of SFK signaling or Src knockdown results in the nuclear localization of cyclin-dependent kinase inhibitor p27 and prevents the proliferative outbreak of dormant BC cells and metastatic lesion formation; however, SFK inhibition did not kill dormant cells. Dormant cell proliferation also required ERK1/2 activation. Combination treatment of cells undergoing the dormant-to-proliferative switch with the Src inhibitor (AZD0530) and MEK1/2 inhibitor (AZD6244) induced apoptosis in a large fraction of the dormant cells and delayed metastatic outgrowth, neither of which was observed with either inhibitor alone. Thus, targeting Src prevents the proliferative response of dormant cells to external stimuli, but requires MEK1/2 inhibition to suppress their survival. These data indicate that treatments targeting Src in combination with MEK1/2 may prevent BC recurrence.

Authors

Lara H. El Touny, Anthony Vieira, Arnulfo Mendoza, Chand Khanna, Mark J. Hoenerhoff, Jeffrey E. Green

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Figure 4

Src inhibition induces an upregulation of nuclear p27 that is reduced and primarily cytoplasmic in D2.0R cells on BME plus COL1. p27 expression determined by quantitative PCR (A), Western blotting (B), and immunofluorescence staining (C) of D2.0R cells seeded on BME or BME plus COL1 treated with AZD0530 or vehicle, and shNT and shSrc D2.0R cells seeded on BME plus COL1 for 72 hours.

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Src inhibition induces an upregulation of nuclear p27 that is reduced an...
Scale bar: 25 μm. ***P = 0.001 compared with BME. (D) p27 levels by Western blot analysis in parental, shLuc, and shp27-1 and shp27-2 D2.0R cells. (E) MTS assay of cells from D on BME plus COL1 treated with 250 nM AZD0530 or vehicle for 72 hours.