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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Research Article

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 6

Silencing of β4 suppresses ErbB2 and c-Met signaling and inhibits the oncogenic behavior of castration-resistant human prostate cancer cells.

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Silencing of β4 suppresses ErbB2 and c-Met signaling and inhibits the on...
(A) Total proteins from the indicated cells lines were subjected to immunoblotting. The asterisk indicates the c-Met precursor. (B) FACS analysis of CD44 and Trop2 in LNCaP and DU145 cells. (C) DU145 cells were transduced with a control shRNA (Co) or 2 shRNAs targeting β4 (no. 1 and no. 2). Lysates were subjected to immunoblotting (top) or immunoprecipitated with control or anti-β4 antibodies followed by immunoblotting (bottom). Vinc, Vinculin. (D) Control and β4-silenced DU145 cells were treated with NRG or HGF for 30 minutes and subjected to immunoblotting. (E) The indicated cells were synchronized by a double block with 1 mM hydroxyurea; deprived of growth factors; treated with serum-free medium (–), 10% FBS, 10 ng/ml HGF, or 10 ng/ml NRG for 10 hours; and subjected to BrdU incorporation assay. The graph represents (mean ± SD) the percentage of BrdU+ cells. **P < 0.01. (F) The indicated cells were subjected to Matrigel invasion assay. 10% FBS, 10 or 100 ng/ml NRG, and 10 or 100 ng/ml HGF were used as chemoattractants. The graph shows the mean fold invasion (± SD) over control. *P < 0.05; **P < 0.01. (G) The indicated cells were injected subcutaneously in nude mice. The graph shows the average tumor weight (indicated by horizontal lines) 32 days after injection. Symbols on the baseline indicate injections that did not generate tumors. The inset shows the mean percentage of Ki-67+ tumor cells (± SD) in the indicated xenografts. Numbers in columns represent the number of mice.