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

Abstract

Background: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.Methods: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).Results: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.Conclusions:Hypoxic stress caused by ADT promotes EMT, providing a mechanism for the cause of malignant progression in prostate cancer.

The unidirectional hypoxia‐activated prodrug OCT1002 inhibits growth and vascular development in castrate‐resistant prostate tumors

“…Having demonstrated the effect of OCT1002 on PC3 cells in vitro, we proceeded to use PC3 cells in murine models in vivo. In our previous work, we measured the oxygen levels in LNCaP and 22Rv1 tumors in SCID mice and found that each untreated tumor type had an intrinsic level of oxygenation that was specific and consistently reproducible . Here, we demonstrated that PC3 tumors grown in nude mice are considerably more hypoxic than LNCaP and 22Rv1 tumors (Figure A).…”

“…We have also shown that single‐modality hormone treatment drives development of more malignant tumors, a consequence of reduced vascularization and oxygenation (days 1‐14) followed by a revascularization and re‐oxygenation over the next 14 days. This was accompanied by a cascade of molecular and phenotypic changes that included evidence of EMT and increased metastasis to the lungs within 4 weeks . The novel analogue OCT1002 caused similar effects in LNCaP xenografts and we also showed that it could block significantly the molecular changes caused by bicalutamide alone, thereby demonstrating that detrimental hypoxia‐induced cellular responses can be effectively blocked.…”

“…LNCaP, 22Rv1, and PC3 xenografts were established on the rear dorsum of nude mice by subcutaneous injection of 2 × 10 6 cells suspended in 100 μL of matrigel with a 21 g needle (Becton Dickinson, Oxford, UK). When tumors reached approximately 200 mm 3 intra‐tumor pO 2 was measured using an OxyLiteTM 2000E system (Oxford Optronix, UK) as previously described . For growth delay studies, tumors were measured every 2 days using Vernier callipers.…”

Chronic hypoxia‐induced slug promotes invasive behavior of prostate cancer cells by activating expression of ephrin‐B1

“…In this study, we demonstrate that chronic hypoxia‐induced slug, an EMT‐driving transcription factor, promotes cell migration and invasion of prostate cancer cells by activating the expression of ephrin‐B1, a ligand of Eph‐related receptor tyrosine kinases. We further show that slug and ephrin‐B1 are coexpressed in chronic hypoxic cells in clinical samples of prostate adenocarcinoma after androgen deprivation therapy (ADT), which causes disruption of tumor blood vessels and results in tumor hypoxia …”

Cellular determinants and microenvironmental regulation of prostate cancer metastasis

“…There is also evidence that androgen deprivation induces EMT in PCa via a ZEB1-AR feedback loop, revealing a potentially important consequence of a standard-of-care for PCa [122]. Hypoxic stress caused by ADT can also promote EMT and drive selection of more malignant PCa tumors [123]. AR splice variants can contribute to PCa aggressiveness through induction of EMT and expression of stem cell marker genes [124].…”