| Summary: | Androgen ablation therapy using bicalutamide (BCA) is a first line treatment for advanced localised prostate cancer; patients treated with this drug have an improved quality of life over 1- 2 years, however they frequently develop treatment resistant, metastatic tumours. Evidence from our laboratory has shown that treatment of LNCaP prostate tumour xenografts with BCA causes a significant reduction in intra-tumour oxygenation and vascular collapse over the first 14 days, followed by reoxygenation and reappearance of blood vessels. The current study investigated LNCaP xenografts treated with BCA or vehicle for 28 days. Tumours excised from the dorsum of SCID mice treated with 2mg/kg of BCA or vehicle (day 0 - 28) were fixed and paraffin- embedded. CD34, Ki-67, eNOS, bcl-2, yH2AX, Rad51, Ku70, E-cadherin, Runx-2, and LC3 were evaluated by immunohistochemistry. In addition, the effect of hypoxia on Runx2 and bcl-2 expression was evaluated in LNCaP cells. BCA treatment resulted in significant reduction in MVD and Ki-67 over the first 14 days (P < 0.01), which was followed by a second phase marked by significant increase in both. The autophagic marker LC3 was highest at the time of lowest oxygenation. In addition, the expression of the protein involved in homologous recombination, Rad51, decreased significantly while the non-homologous end joining protein, Ku 70 remained the same in all tumours. Expression of yH2AX showed that DSBs were repaired from day 21 to 28 of BCA treatment. Furthermore, E-cadherin decreased over 28 days; Runx-2 and bcl-2 were significantly increased from day 21 - 28 while eNOS expression was reduced. QPCR showed that hypoxia selected for cells which over-expressed Runx2 and bcl-2. This study has shown that hypoxia-inducing treatment with BCA caused a number of changes including an immediate decrease in MVD and this selected for cells with a more malignant phenotype.
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