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.
Source: β4 Integrin signaling induces expansion of prostate tumor progenitors. Yoshioka T, Otero J, Chen Y, Kim YM, Koutcher JA, Satagopan J, Reuter V, Carver B, de Stanchina E, Enomoto K, Greenberg NM, Scardino PT, Scher HI, Sawyers CL, Giancotti FG (firstname.lastname@example.org). J Clin Invest. 2013 Jan 25.
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