Equal number of cells were grown on matrigel coated plates and incubated at 37uC for 7 days

MTA1-knockdown and treatment with compounds, we allowed tumors to colonize and develop for 14 days prior to randomization. Tumor development was monitored by BL imaging weekly. Mice that developed tumors were randomized by the size of images in three subgroups and treated with vehicle control, resveratrol or PTER, i.p., at the same 50 mg/kg/ day dose. Pterostilbene dose was kept identical to resveratrol’s to determine potency differences. While vehicle-treated mice showed rapid tumor progression in EV xenografts, resveratrol and PTER caused noticeable delay in tumor growth. Resveratrol, but more so PTER, showed tumor inhibitory effects, order R-7128 although statistical significance was not reached due to small number of mice. Xenografts expressing MTA1shRNA exhibited markedly reduced tumor growth at week 5 post-transplantation with marginal significance versus EV-Ctrl. Moreover, MTA1-knockdown tumors treated with compounds had further response, and the differences versus EV-Ctrl became highly significant. Therefore, MTA1-knockdown sensitized cells to resveratrol and particularly to PTER. Consistent with the potent antitumor effects, resveratrol- and PTER-treated tumors showed reduced mitotic activity compared to vehicle-treated EV-tumors as shown by Ki-67 IHC. Importantly, consistent with reduced MTA1 activity in tumors, downstream acetyl-target of MTA1, Acp53, 9726632 had significantly increased levels upon treatments, best seen with PTER. Accordingly, M30 staining revealed a large increase in apoptosis in tumors from EV compound-treated mice and MTA1-knockdown group. Additionally, microvessel area, as assessed by CD31 immunostaining, decreased by,59% in EV-compound treated tumors and by,67% in MTA1knockdown group compared to EV-Ctrl. Few preclinical PCa xenograft 7925608 models progress to metastasis, making it difficult to study the functional significance of MTA1 in metastasis. Our previous study with LNCaP-Luc cells showed no metastasis when orthotopically injected into mice. Because of the more aggressive phenotype of Du145 cells, we considered the possibility of spontaneous metastasis in orthotopic Du145 xenografts. At the beginning of week 7, we detected BL signals distinct from the primary source in sham EV-Ctrl group. Ex vivo BL images of metastasis were detected at necropsy in the liver, kidneys and lung/heart, and histology was confirmed by a certified pathologist . The highest incidence of metastasis was observed in the EV group, whereas the MTA1shRNA group showed only 5075% and with high degree of heterogeneity. Extensive macrometastases in all organs observed in EVCtrl were inhibited by resveratrol and PTER. MTA1-knockdown tumors developed smaller metastases, and in fewer organs. Notably, MTA1shRNA tumors treated with compounds either did not develop any kidney metastasis or had small lesions in one kidney. The inhibition of metastasis in response to MTA1-targeting agents and MTA1 silencing indicates MTA1 contribution to local invasion, dissemination and metastasis. Together these data suggest that the MTA1 signaling plays an essential role in the development and progression of metastatic prostate cancer and that targeting MTA1 pathway by dietary polyphenols may be effective in slowing down tumor progression and preventing metastasis. We next measured steady-state serum levels of resveratrol and PTER following 5 weeks of continuous treatment and found that serum accumulation of PTER was always higher than resveratrol. Interestingly, it appeared tha