V-ATPase inhibition decreases mutant androgen receptor activity in castrate-resistant prostate cancer

Prostate cancer is critically dependent on androgen receptor (AR) signaling. Despite initial responsiveness to androgen deprivation, most patients with advanced prostate cancer subsequently progress to a clinically aggressive castrate-resistant prostate cancer (CRPC) phenotype, typically associated with expression of splice-variant or mutant AR forms. Although current evidence suggests that the vacuolar-ATPase (V-ATPase), a multiprotein complex that catalyzes proton transport across intracellular and plasma membranes, influences wild-type AR function, the effect of V-ATPase inhibition on variant AR function is unknown. Inhibition of V-ATPase reduced AR function in wild-type and mutant AR luciferase reporter models. In hormone-sensitive prostate cancer cell lines (LNCaP, DuCaP) and mutant AR CRPC cell lines (22Rv1, LNCaP-F877L/T878A), V-ATPase inhibition using bafilomycin-A1 and concanamycin-A reduced AR expression, and expression of AR target genes, at mRNA and protein levels. Furthermore, combining chemical V-ATPase inhibition with the AR antagonist enzalutamide resulted in a greater reduction in AR downstream target expression than enzalutamide alone in LNCaP cells. To investigate the role of individual subunit isoforms, siRNA and CRISPR-Cas9 were used to target the V ₁C1 subunit in 22Rv1 cells. Whereas transfection with ATP6V1C1-targeted siRNA significantly reduced AR protein levels and function, CRISPR-Cas9–mediated V ₁C1 knockout showed no substantial change in AR expression, but a compensatory increase in protein levels of the alternate V ₁C2 isoform. Overall, these results indicate that V-ATPase dysregulation is directly linked to both hormone-responsive prostate cancer and CRPC via impact on AR function. In particular, V-ATPase inhibition can reduce AR signaling regardless of mutant AR expression.

10.1158/1535-7163.MCT-20-0662

1535-7163

739-748

Whitton, Bradleigh

352554cc-cbf8-4d58-8c8f-51721abfe743

Okamoto, Haruko

cea35380-7618-44c8-a268-47b0198cc7f9

Rose-Zerilli, Matthew

29603401-e310-4054-b818-8a542c361b9a

Packham, Graham

fdabe56f-2c58-469c-aadf-38878f233394

Crabb, Simon J

bcd1b566-7677-4f81-8429-3ab0e85f8373

1 April 2021

Whitton, Bradleigh

352554cc-cbf8-4d58-8c8f-51721abfe743

Okamoto, Haruko

cea35380-7618-44c8-a268-47b0198cc7f9

Rose-Zerilli, Matthew

29603401-e310-4054-b818-8a542c361b9a

Packham, Graham

fdabe56f-2c58-469c-aadf-38878f233394

Crabb, Simon J

bcd1b566-7677-4f81-8429-3ab0e85f8373

Whitton, Bradleigh, Okamoto, Haruko, Rose-Zerilli, Matthew, Packham, Graham and Crabb, Simon J (2021) V-ATPase inhibition decreases mutant androgen receptor activity in castrate-resistant prostate cancer. Molecular Cancer Therapeutics, 20 (4), 739-748. (doi:10.1158/1535-7163.MCT-20-0662).

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Accepted/In Press date: 5 February 2021

e-pub ahead of print date: 9 February 2021

Published date: 1 April 2021

Additional Information: Funding Information: B. Whitton was funded by a doctoral studentship from The Urology Foundation, Wessex Medical Research, and The Gerald Kerkut Charitable Trust. This work was also supported by grants from Cancer Research UK (C2750/A23669). Funding Information: G. Packham reports grants from The Urology Foundation, Wessex Medical Research, The Gerald Kerkut Charitable Trust, and Cancer Research UK during the conduct of the study. S.J. Crabb reports personal fees from Roche, Janssen Cilag, MSD, Pfizer, and Bayer; grants and personal fees from AstraZeneca; and grants from Astex Pharmaceuticals and Clovis Oncology outside the submitted work. No potential conflicts of interest were disclosed by the other authors. Publisher Copyright: © 2021 American Association for Cancer Research.