1273 A MECHANISM OF HYPOXIA-INDUCED IMMUNE ESCAPE IN PROSTATE CANCER CELLS

You have accessJournal of UrologyProstate Cancer: Basic Research1 Apr 20111273 A MECHANISM OF HYPOXIA-INDUCED IMMUNE ESCAPE IN PROSTATE CANCER CELLS D. Robert Siemens, Tom Hamilton, Ivraym Barsoum, Xin Li, Ellen Miles, and Charles Graham D. Robert SiemensD. Robert Siemens Kingston, Canada More articles by this author , Tom HamiltonTom Hamilton Kingston, Canada More articles by this author , Ivraym BarsoumIvraym Barsoum Kingston, Canada More articles by this author , Xin LiXin Li Kingston, Canada More articles by this author , Ellen MilesEllen Miles Kingston, Canada More articles by this author , and Charles GrahamCharles Graham Kingston, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.959AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES We previously showed that hypoxia induces resistance to NK cell-mediated lysis in tumour cells through a mechanism that involves the shedding of NK cell-activating ligands (MICA) from the cell surface. Furthermore, we were able to block this hypoxia-induced shedding of MICA, as well as resistance to NK-mediated lysis, by activating NO signalling in the cancer cells. Here we explore the mechanisms of this hypoxia-mediated prostate cancer immune escape. METHODS To determine whether tumour cell resistance to lysis by NK cells is dependent on HIF-1transcriptional activity we knocked down HIF-1a using validated siRNA. We investigated hypoxic regulation of the metalloproteinase disintegrins ADAM 10 and 17 utilizing Western blot, qPCR and confocal immunofluorescence and their role in hypoxia-induced shedding of MICA (on flow cytometry) with siRNA knockdown experiments. Standard 4-hour chromium release assays were used to determine effects on NK-mediated lysis. Finally, we examined whether endogenous nitric oxide signalling regulates the hypoxia-induced up-regulation of the ADAMs and HIF-1a using nitroglycerin or 8-bromo-cGMP. RESULTS Knockdown of HIF-1a in DU145 prostate cancer cells and MDA-MB-231 breast cancer cells abrogated the hypoxia-induced down-regulation of surface MICA levels (P < 0.001 (ANOVA) as well as hypoxia-induced resistance to NK cell-mediated lysis. ADAM17 expression decreased in hypoxic conditions but ADAM10 increased and was confirmed by confocal immunofluorescence and qPCR (P < 0.05). Down-regulation of ADAM10 expression significantly attenuated the hypoxia-induced release of MICA on flow cytometry and forced down-regulation of HIF-1a expression prevented the hypoxia-induced increase of ADAM10 transcript levels (P<0.01). Activation of nitric oxide signalling with either nitroglycerin (1 μM) or 8-bromo-cGMP (10 nM) effectively attenuated the hypoxia-induced increases in ADAM10 transcript levels. Also, Western blot analysis revealed that nitroglycerin (1 μM) was able to block the accumulation of HIF-1a in DU145 cells incubated in hypoxia. CONCLUSIONS Taken together, our findings demonstrate a novel mechanism by which hypoxia contributes to immune escape in prostate cancer cells. Furthermore, they reveal that activation of nitric oxide signalling interferes with this pathway. These findings are important because they indicate that nitric oxide mimetics could potentially be used as immunosensitisers in the treatment and/or prevention of cancer. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e509-e510 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information D. Robert Siemens Kingston, Canada More articles by this author Tom Hamilton Kingston, Canada More articles by this author Ivraym Barsoum Kingston, Canada More articles by this author Xin Li Kingston, Canada More articles by this author Ellen Miles Kingston, Canada More articles by this author Charles Graham Kingston, Canada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...