Androgen deprivation in LNCaP prostate tumour xenografts induces vascular changes and hypoxic stress, resulting in promotion of epithelial-to-mesenchymal transition.

When single-agent androgen deprivation therapy (ADT) is administered for locally advanced prostate cancer, men usually relapse within 1-2 years with more malignant castrate-resistant disease. The reason for this is currently unknown. We now hypothesise that an initial treatment response that increases tumour hypoxia drives selection of more malignant tumours.

The LNCaP prostate tumour xenografts were analysed for physiological (oxygen and vasculature) and genetic (PCR array) changes during longitudinal treatment with ADT (bicalutamide, 6 or 2 mg kg(-1) daily for 28 days).

Bicalutamide caused an immediate (within 24 h) dose-dependent fall in oxygenation in LNCaP-luc prostate tumours with a nadir of ≤0.1% oxygen within 3-7 days; this was attributed to a significant loss of tumour microvessels (window chamber study). The hypoxic nadir persisted for 10-14 days. During the next 7 days, tumours regrew, oxygenation improved and the vasculature recovered; this was inhibited by the VEGF inhibitor B20.4.1.1. Gene expression over 28 days showed marked fluctuations consistent with the physiological changes. Accompanying the angiogenic burst (day 21) was a particularly striking increase in expression of genes associated with epithelial-to-mesenchymal transition (EMT). In particular, insulin-like growth factor 1 (IGF-1) showed increases in mRNA and protein expression.

Hypoxic stress caused by ADT promotes EMT, providing a mechanism for the cause of malignant progression in prostate cancer.British Journal of Cancer advance online publication, 8 March 2016; doi:10.1038/bjc.2016.29 www.bjcancer.com.

British journal of cancer. 2016 Mar 08 [Epub ahead of print]

N M Byrne, H Nesbitt, L Ming, S R McKeown, J Worthington, D J McKenna

Biomedical Science Research Institute, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK., Biomedical Science Research Institute, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK., Biomedical Science Research Institute, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK., Biomedical Science Research Institute, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK., Axis Bioservices Ltd, Research Laboratory, Castleroe Road, Coleraine BT51 3RP, Northern Ireland, UK., Biomedical Science Research Institute, University of Ulster, Cromore Road, Coleraine, BT52 1SA Northern Ireland, UK.