RNASEH2B loss and PARP inhibition in advanced prostate cancer
Juliet Carmichael, … , Adam Sharp, Johann de Bono
Juliet Carmichael, … , Adam Sharp, Johann de Bono
Published June 4, 2024
Citation Information: J Clin Invest. 2024;134(21):e178278. https://doi.org/10.1172/JCI178278.
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Clinical Research and Public Health Oncology

RNASEH2B loss and PARP inhibition in advanced prostate cancer

Abstract

BACKGROUND Clinical trials have suggested antitumor activity from PARP inhibition beyond homologous recombination deficiency (HRD). RNASEH2B loss is unrelated to HRD and preclinically sensitizes to PARP inhibition. The current study reports on RNASEH2B protein loss in advanced prostate cancer and its association with RB1 protein loss, clinical outcome, and clonal dynamics during treatment with PARP inhibition in a prospective clinical trial.METHODS Whole tumor biopsies from multiple cohorts of patients with advanced prostate cancer were interrogated using whole-exome sequencing (WES), RNA-Seq (bulk and single nucleus), and IHC for RNASEH2B and RB1. Biopsies from patients treated with olaparib in the TOPARP-A and TOPARP-B clinical trials were used to evaluate RNASEH2B clonal selection during olaparib treatment.RESULTS Shallow codeletion of RNASEH2B and adjacent RB1 — colocated at chromosome 13q14 — was common, deep codeletion infrequent, and gene loss associated with lower mRNA expression. In castration-resistant prostate cancer (CRPC) biopsies, RNASEH2B and RB1 mRNA expression correlated, but single nucleus RNA-Seq indicated discordant loss of expression. IHC studies showed that loss of the 2 proteins often occurred independently, arguably due to stochastic second allele loss. Pre- and posttreatment metastatic CRPC (mCRPC) biopsy studies from BRCA1/2 WT tumors, treated on the TOPARP phase II trial, indicated that olaparib eradicated RNASEH2B-loss tumor subclones.CONCLUSION PARP inhibition may benefit men suffering from mCRPC by eradicating tumor subclones with RNASEH2B loss.TRIAL REGISTRATION Clinicaltrials.gov NCT01682772.FUNDING AstraZeneca; Cancer Research UK; Medical Research Council; Cancer Research UK; Prostate Cancer UK; Movember Foundation; Prostate Cancer Foundation.

Authors

Juliet Carmichael, Ines Figueiredo, Bora Gurel, Nick Beije, Wei Yuan, Jan Rekowski, George Seed, Suzanne Carreira, Claudia Bertan, Maria de Los Dolores Fenor de La Maza, Khobe Chandran, Antje Neeb, Jon Welti, Lewis Gallagher, Denisa Bogdan, Mateus Crespo, Ruth Riisnaes, Ana Ferreira, Susana Miranda, Jinqiu Lu, Michael M. Shen, Emma Hall, Nuria Porta, Daniel Westaby, Christina Guo, Rafael Grochot, Christopher J. Lord, Joaquin Mateo, Adam Sharp, Johann de Bono

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Figure 2

Validation and optimization of a RNASEH2B (RM433) antibody for IHC.

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Validation and optimization of a RNASEH2B (RM433) antibody for IHC. (A) ...
(A) RNASEH2B antibody specificity confirmed by Western blotting of whole-cell lysates from HeLa cells treated with nontargeting control siRNA and pooled RNASEH2B siRNA. (B) IHC was run on HeLa cell pellets being treated with nontargeting control siRNA and pooled RNASEH2B siRNA, as well as HeLa RNASEH2B gene knock-outs and normal human pancreatic tissue. IHC depicted; magnification, × 10; scale bar: 100 μm. (C–E) Scatter plots showing associations between RNASEH2B IHC quantification by visual nuclear H score conducted by blinded pathologist and AI-trained HALO-generated OD, % negative cells and digital nuclear H Score. r and P values were calculated using Spearman correlation (F) Representative micrographs of RNASEH2B detection by IHC. Examples of high, low heterogenous (interspersed and sub-clonal) protein expression are shown. IHC depicted here; magnification × 10; scale bar: 100 μm. IHC, Immunohistochemistry; KO, knock-out; PC, prostate cancer; AI, artificial intelligence; OD, optical density.