Understanding the mechanistic basis for transition to late stage aggressive disease is vital for both assigning patient risk status in the localised setting and also identifying novel treatment strategies to prevent progression. Sub-regions of intratumoral hypoxia are found in all solid tumours and are associated with many biologic drivers of tumour progression. Crucially, more recent findings show the co-presence of hypoxia and genomic instability can confer a uniquely adverse prognosis in prostate cancer. In-depth informatic and functional studies suggests a role for hypoxia in co-operating with oncogenic drivers (e.g. loss of PTEN) and suppressing DNA repair capacity. To delineate a direct relationship between hypoxia and PTEN loss, we interrogated the impact of chronic hypoxia (1% O2, 0.2% O2; 72 h) on PTEN oncogenic signalling and chromosome instability. Quantitative immunofluorescence of centrosome aberrations, using antibodies to phospho-Histone H3 and Centrin-1, show significant increases in centriole numbers (p < 0.05) in mitotic cells under chronic hypoxic conditions and an increase in the incidence of micronuclei (p < 0.005) specifically in chronic hypoxic cells with PTEN loss. Hypoxic suppression of homologous recombination represents a "contextual lethal" vulnerability in hypoxic prostate tumours which could extend the application of existing DNA repair targeting agents such as poly-ADP ribose polymerase inhibitors. Additional mechanistic studies using hTERT-immortalized, primary prostate epithelial cells isogenic for c-MYC, BRCA2, or TP53/RB (SV40-transduced) were studied as to the relationship between hypoxia, inherent versus acquired genetic instability and DNA repair capacity in-vitro and in-situ. Chronic hypoxia (20 generation doublings at 0.2% O2) was sufficient to drive increased copy number alterations (CNAs) in selected clones by up to 30% in TP53/RB null cells. This finding is now being quantitated with a clonal evolution model and genotype-phenotype associations are being validated using functional transformation and invasion assays. Further investigation is now required to assess this relationship on the background of existing genomic alterations relevant to prostate and other cancers and also characterise the role of hypoxia in driving early metastatic spread. Supported by core funding from Cancer Research UK Manchester Institute and grants within the Cancer Research UK Manchester RadNet Unit, NIHR Manchester Biomedical Research Centre and a Prostate Cancer UK-Movember Centre of Excellence award.

Citation Format: Robert G. Bristow. Genomic instability and hypoxia as co-drivers of prostate cancer aggression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr SY37-01.