Although castration-resistant prostate cancers no longer respond to anti-androgen therapies, the androgen receptor (AR) is still required to promote tumor survival. However, the signaling pathways downstream of AR that promote this survival are not well known. We recently identified an AR-dependent survival pathway whereby AR induction of integrin α6β1 and adhesion to laminin activates NF-κB/RelA signaling and Bcl-xL. This pathway acts in parallel with the PI3K/Akt pathway in Pten-null tumor cells such that combined inhibition of both PI3K and integrin α6β1 is required to effectively kill tumor cells adherent to laminin. However, PTEN-null castration-resistant tumors were not effectively killed by this combination. I discovered that BNIP3, a hypoxia-induced BH3-only, pro-mitophagic Bcl-2 family member, is induced by androgen in castration-resistant cells through integrin α6β1 and HIF1α. Furthermore, castration-resistant cells adherent to laminin were much more efficient at inducing autophagy in response to androgen. Androgen blocked the ability of the PI3K inhibitor PX866 to kill castration-resistant tumors, but this was reversed by loss of BNIP3. Although BNIP3 was dispensable for androgen-induced autophagy, its mitophagy function was required for BNIP3 to promote resistance to PX866. Thus, enhanced hypoxia signaling in cooperation with AR/α6β1/HIF1α signaling on laminin in castration-resistant cells drives the expression of BNIP3 and enhances autophagy, both of which contribute to PX866 resistance through induction of mitophagy.
|Commitee:||Cress, Anne, MacKeigan, Jeff, Tindall, Donald, Williams, Bart|
|School:||Van Andel Research Institute|
|School Location:||United States -- Michigan|
|Source:||DAI-B 78/11(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Cellular biology, Oncology|
|Keywords:||Alpha6, Cancer, Castration-Resistant, Integrin, Prostate, Resistant|
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