Abstract
Castration-resistant prostate cancer (CRPC) is characterized by reactivation of androgen receptor (AR) signaling, in part by elevated expression of AR splice variants (ARv) including ARv7, a constitutively active, ligand binding domain (LBD)-deficient variant whose expression has been correlated with therapeutic resistance and poor prognosis. In a screen to identify small-molecule dual inhibitors of both androgen-dependent and androgen-independent AR gene signatures, we identified the chalcone C86. Binding studies using purified proteins and CRPC cell lysates revealed C86 to interact with Hsp40. Pull-down studies using biotinylated-C86 found Hsp40 present in a multiprotein complex with full-length (FL-) AR, ARv7, and Hsp70 in CRPC cells. Treatment of CRPC cells with C86 or the allosteric Hsp70 inhibitor JG98 resulted in rapid protein destabilization of both FL-AR and ARv, including ARv7, concomitant with reduced FL-AR- and ARv7-mediated transcriptional activity. The glucocorticoid receptor, whose elevated expression in a subset of CRPC also leads to androgen-independent AR target gene transcription, was also destabilized by inhibition of Hsp40 or Hsp70. In vivo, Hsp40 or Hsp70 inhibition demonstrated single-agent and combinatorial activity in a 22Rv1 CRPC xenograft model. These data reveal that, in addition to recognized roles of Hsp40 and Hsp70 in FL-AR LBD remodeling, ARv lacking the LBD remain dependent on molecular chaperones for stability and function. Our findings highlight the feasibility and potential benefit of targeting the Hsp40/Hsp70 chaperone axis to treat prostate cancer that has become resistant to standard antiandrogen therapy. Significance: These findings highlight the feasibility of targeting the Hsp40/Hsp70 chaperone axis to treat CRPC that has become resistant to standard antiandrogen therapy.
Original language | English (US) |
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Pages (from-to) | 4022-4035 |
Number of pages | 14 |
Journal | Cancer Research |
Volume | 78 |
Issue number | 14 |
DOIs | |
State | Published - Jul 15 2018 |
Externally published | Yes |
ASJC Scopus subject areas
- Oncology
- Cancer Research