β4 Integrin signaling induces expansion of prostate tumor progenitors
Toshiaki Yoshioka, … , Charles L. Sawyers, Filippo G. Giancotti
Toshiaki Yoshioka, … , Charles L. Sawyers, Filippo G. Giancotti
Published January 25, 2013
Citation Information: J Clin Invest. 2013;123(2):682-699. https://doi.org/10.1172/JCI60720.
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β4 Integrin signaling induces expansion of prostate tumor progenitors

Abstract

The contextual signals that regulate the expansion of prostate tumor progenitor cells are poorly defined. We found that a significant fraction of advanced human prostate cancers and castration-resistant metastases express high levels of the β4 integrin, which binds to laminin-5. Targeted deletion of the signaling domain of β4 inhibited prostate tumor growth and progression in response to loss of p53 and Rb function in a mouse model of prostate cancer (PB-TAg mice). Additionally, it suppressed Pten loss-driven prostate tumorigenesis in tissue recombination experiments. We traced this defect back to an inability of signaling-defective β4 to sustain self-renewal of putative cancer stem cells in vitro and proliferation of transit-amplifying cells in vivo. Mechanistic studies indicated that mutant β4 fails to promote transactivation of ErbB2 and c-Met in prostate tumor progenitor cells and human cancer cell lines. Pharmacological inhibition of ErbB2 and c-Met reduced the ability of prostate tumor progenitor cells to undergo self-renewal in vitro. Finally, we found that β4 is often coexpressed with c-Met and ErbB2 in human prostate cancers and that combined pharmacological inhibition of these receptor tyrosine kinases exerts antitumor activity in a mouse xenograft model. These findings indicate that the β4 integrin promotes prostate tumorigenesis by amplifying ErbB2 and c-Met signaling in tumor progenitor cells.

Authors

Toshiaki Yoshioka, Javier Otero, Yu Chen, Young-Mi Kim, Jason A. Koutcher, Jaya Satagopan, Victor Reuter, Brett Carver, Elisa de Stanchina, Katsuhiko Enomoto, Norman M. Greenberg, Peter T. Scardino, Howard I. Scher, Charles L. Sawyers, Filippo G. Giancotti

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Figure 5

The β4 integrin amplifies ErbB2 and c-Met signaling in tumor progenitor cells.

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The β4 integrin amplifies ErbB2 and c-Met signaling in tumor progenitor ...
(A) Dissociated total tumor cells and the indicated subpopulations from 4.5-month-old PB-TAg; β4-WT mice were subjected to semiquantitative RT-PCR to assess expression of the indicated mRNAs. (B) Adjacent sections of high-grade PIN lesions from PB-TAg; β4-WT mice were stained with H&E and antibodies to β4, followed by counterstaining with DAPI, and anti-Ki-67, followed by counterstaining with hematoxylin, anti-ErbB2, or anti-c-Met. Basal tumor cells in high-grade PIN lesions (arrows) express elevated levels of β4 and ErbB2 as compared with normal basal cells (asterisk). The levels of c-Met are increased in both basal and suprabasal tumor cells (arrows). Scale bar: 50 μm. (C) DP cells from 3 tumors arising in 4.5-month-old PB-TAg; β4-WT mice were subjected to semiquantitative RT-PCR to assess expression of the indicated mRNAs. Total tumor cells served as positive controls. (D) β4-positive cells were sorted from 4.5-month-old PB-TAg; β4-WT and 6.5-month-old PB-TAg; β4-1355T mice after gating for Lin– cells, plated on laminin-5–coated plates, and stimulated or not with HGF or NRG-1 for 20 minutes. Equal amounts of total protein were subjected to immunoblotting. (E) DU145 cells were treated with varying concentrations of lapatinib (EGFR/HER2 inhibitor) or PHA665752 (c-Met inhibitor) and subjected to immunoblotting. (F) DP cells from PB-TAg; β4-WT mice were assayed for sphere-forming capability in the presence of 100 nM PHA665752, 100 nM lapatinib, or both. The graph shows the mean (± SEM) number of spheres per 10,000 cells after 12 days of culture.