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Rb1 and Trp53 cooperate to suppress prostate cancer lineage plasticity, metastasis, and antiandrogen resistance

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Science  06 Jan 2017:
Vol. 355, Issue 6320, pp. 78-83
DOI: 10.1126/science.aah4199

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Evading cancer drugs by identity fraud

Prostate cancer growth is fueled by male hormones called androgens. Drugs targeting the androgen receptor (AR) are initially efficacious, but most tumors eventually become resistant (see the Perspective by Kelly and Balk). Mu et al. found that prostate cancer cells escaped the effects of androgen deprivation therapy through a change in lineage identity. Functional loss of the tumor suppressors TP53 and RB1 promoted a shift from AR-dependent luminal epithelial cells to AR-independent basal-like cells. In related work, Ku et al. found that prostate cancer metastasis, lineage switching, and drug resistance were driven by the combined loss of the same tumor suppressors and were accompanied by increased expression of the epigenetic regulator Ezh2. Ezh2 inhibitors reversed the lineage switch and restored sensitivity to androgen deprivation therapy in experimental models.

Science, this issue p. 84, p. 78; see also p. 29

Abstract

Prostate cancer relapsing from antiandrogen therapies can exhibit variant histology with altered lineage marker expression, suggesting that lineage plasticity facilitates therapeutic resistance. The mechanisms underlying prostate cancer lineage plasticity are incompletely understood. Studying mouse models, we demonstrate that Rb1 loss facilitates lineage plasticity and metastasis of prostate adenocarcinoma initiated by Pten mutation. Additional loss of Trp53 causes resistance to antiandrogen therapy. Gene expression profiling indicates that mouse tumors resemble human prostate cancer neuroendocrine variants; both mouse and human tumors exhibit increased expression of epigenetic reprogramming factors such as Ezh2 and Sox2. Clinically relevant Ezh2 inhibitors restore androgen receptor expression and sensitivity to antiandrogen therapy. These findings uncover genetic mutations that enable prostate cancer progression; identify mouse models for studying prostate cancer lineage plasticity; and suggest an epigenetic approach for extending clinical responses to antiandrogen therapy.

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