Sahar Soliman

Anticancer Efficacy of Simvastatin on Prostate Cancer Cells and Tumor Xenografts Is Associated with Inhibition of Akt and Reduced Prostate-Specific Antigen Expression

Prostate cancer is the second-leading cause of cancer-associated death among men in the United States. There has been renewed interest in the potential therapeutic benefits of statins for cancer. Simvastatin, a widely used generic drug for preventing cardiovascular events, is well known for its effects on cellular proliferation and inflammation, two key processes that also determine the rate of tumor growth. Although a growing body of evidence suggests that statins have the potential to reduce the risk of many cancers, there are discrepancies over the pro- and anticancer effects of statins. In the current study, we sought to investigate the effects of simvastatin on the Akt pathway in prostate cancer cells with respect to the regulation of various cell functions in vitro and tumor growth in vivo. Time- and dose-dependent effects of simvastatin on LNCaP (androgen-dependent) and PC3 (androgen-independent) cells indicate that treatment with simvastatin at concentrations as low as 25 μM was sufficient to inhibit serum-stimulated Akt activity. Akin to this, treatment with simvastatin significantly inhibited serum-induced cell migration, invasion, colony formation, and proliferation. Simvastatin-mediated effects on colony formation were rescued by adenovirus-mediated expression of constitutively active Akt (myristoylated Akt) in PC3 cell lines. A PC3 xenograft model performed in nude mice exhibited reduced tumor growth with simvastatin treatment associated with decreased Akt activity and reduced prostate-specific antigen (PSA) levels. Our findings demonstrate the therapeutic benefits of simvastatin for prostate cancer and suggest a link between simvastatin, regulation of Akt activity, and PSA expression in prostate tumors.

Vascular Protection by Angiotensin Receptor Antagonism Involves Differential VEGF Expression in Both Hemispheres after Experimental Stroke

We identified that the angiotensin receptor antagonist, candesartan, has profound neurovascular protective properties when administered after ischemic stroke and was associated with a proangiogenic state at least partly explained by vascular endothelial growth factor A (VEGFA). However, the spatial distribution of vascular endothelial growth factor (VEGF) isoforms and their receptors remained unknown. Protein analysis identified a significant increase in vascular endothelial grow factor B (VEGFB) in the cerebrospinal fluid (CSF) and the ischemic hemispheres (with increased VEGF receptor 1 activation) of treated animals (p<0.05) which was co-occurring with an increase in protein kinase B (Akt) phosphorylation (p<0.05). An increase in VEGFA protein in the contralesional hemisphere corresponded to a significant increase in vascular density at seven days (p<0.01) after stroke onset. Vascular restoration by candesartan after stroke maybe related to differential regional upregulation of VEGFB and VEGFA, promoting a “prosurvival state” in the ischemic hemisphere and angiogenesis in the contralesional side, respectively. These vascular changes in both hemispheres after effective treatment are likely to contribute to enhanced recovery after stroke.

Compound 21 is pro-angiogenic in the brain and results in sustained recovery after ischemic stroke.

Introduction: Angiotensin II type 2 receptor (AT2R) stimulation is neuroprotective after experimental stroke. However, the therapeutic utility of AT2R stimulation has been hampered by the lack of a specific agonist with favourable bioavailability. Compound 21 (C21) – the first non-peptide AT2R agonist – offers a potential option to enhance stroke recovery. This study aimed to investigate the effect of C21 administration on early and late stroke outcomes, and the molecular mediators involved. Methods: Rats were subjected to 3 h or 90 min of middle cerebral artery occlusion (MCAO) and randomized to intraperitoneal C21 (0.03 mg/kg) or saline at reperfusion. Animals were sacrificed at 24 h or 7 days and brains were collected for molecular analysis and immunostaining, respectively. Functional outcome at days 1, 4 and 7 was assessed blindly. C21 angiogenic potential was assessed in vitro. Results: After 3 h of MCAO, C21 treatment reduced infarct size and improved behavioural outcome at 24 h without affecting blood pressure. Co-administration of the AT2R antagonist (PD123319) blocked these effects. On the molecular level, C21 decreased brain haemoglobin content, down-regulated apoptotic and oxidative markers, and increased pro-survival molecules in the brain. After 90 min of MCAO, C21 treatment resulted in sustained functional improvement at 7 days, together with increased vascular density in the ischemic penumbra. In vitro, C21 showed a pro-angiogenic effect that was blocked with brain-derived neurotrophic factor neutralization. Conclusion: These findings demonstrate that a single dose of C21 is neurovascular-protective and improves stroke outcome possibly through increasing neurotrophin activity, mitigating brain inflammation, and promoting antioxidant and pro-angiogenic effects.

Candesartan Induces a Prolonged Proangiogenic Effect and Augments Endothelium-Mediated Neuroprotection after Oxygen and Glucose Deprivation: Role of Vascular Endothelial Growth Factors A and B

Angiogenesis is a key component of recovery after stroke. Angiotensin II receptor blocker (ARB) treatment improves neurobehavioral outcome and is associated with enhanced angiogenesis after stroke. The purpose of this study is to investigate the temporal pattern of the ARB proangiogenic effect in the ischemic brain and its association with vascular endothelial growth factors VEGF-A and VEGF-B. Wistar rats were exposed to 90-minute middle cerebral artery occlusion and treated with candesartan (1 mg/kg) at reperfusion. The proangiogenic potential of the cerebrospinal fluid was determined at 8, 24, 48, and 72 hours using an in vitro Matrigel tube formation assay. In addition, the expression of VEGF-A and VEGF-B was measured in brain homogenates using Western blotting at the same time points. A single candesartan dose induced a prolonged proangiogenic effect and a prolonged upregulation of VEGF-A and VEGF-B in vivo. In the ischemic hemisphere, candesartan treatment was associated with stabilization of hypoxia-inducible factor-1α and preservation of angiopoietin-1. The effect of ARB treatment on endothelial cells was studied in vitro. Our results identified brain endothelial cells as one target for the action of ARBs and a source of the upregulated VEGF-A and VEGF-B, which exerted an autocrine angiogenic response, in addition to a paracrine neuroprotective effect. Taken together, this study highlights the potential usefulness of augmenting the endogenous restorative capacity of the brain through the administration of ARBs.

Abstract B47: Pleiotropic effects of simvastatin on prostate tumor growth and metastasis

Background: Statins are a class of drugs that inhibits HMG-CoA reductase, a rate liming enzyme in cholesterol synthesis. Simvastatin, a widely used generic drug for preventing cardiovascular events inhibit inflammation and stabilize atherosclerotic plaques. Growing body of evidences suggest that statins have the potential to reduce the risk of many cancer types. Objectives and Hypothesis: Our long-term goal is to enable the development of new and innovative therapeutics for prostate cancer through better understanding of the molecular mechanisms regulating prostate cancer growth and bone metastasis. In prostate cancer cells, simvastatin is known to induce apoptosis. Akt, a multitask signaling molecule, is the major survival kinase activated in cancer cells. Our central hypothesis is that treatment with simvastatin will inhibit Akt affecting prostate cancer cell function, tumor growth and metastasis. The rationale for the proposed research is that, once it is known mechanistically how simvastatin regulates prostate cancer cell function, it is likely that prostate tumor growth and metastasis can be downregulated therapeutically utilizing simvastatin using a novel drug-repurposing strategy. This would be of singular importance in the management of this disease. Experimental Design and Results: In the current study, we sought to investigate the pleiotropic effects of simvastatin on major signaling pathways in prostate cancer cells with respect to the regulation of cellular functions such as migration, proliferation, colony/foci formation and invasion, along with its already known effects on apoptosis. Time- and dose-effects of simvastatin on LNCaP (androgen-dependent) and PC-3 (androgen-independent) cells indicated that treatment with as low as 25µM simvastatin was sufficient to inhibit serum-stimulated activation of Akt-mTOR and cRaf-ERK pathways. Akin to this, treatment with 25µM simvastatin significantly inhibited serum- and EGF-induced cell migration, invasion, colony formation and proliferation. Simvastatin-mediated effects on cell migration and colony formation was rescued by adenovirus-mediated expression of constitutively active Akt (myristoylated Akt) in androgen-independent prostate cancer cells lines such as PC3 and LnCAP C4-2. A xenograft model performed in nude mice exhibited reduced PC3 prostate tumor growth with simvastatin treatment (2mg/kg body weight/day for 2 weeks) demonstrating the therapeutic potential of simvastatin for prostate cancer therapy. Conclusions and Future Directions: Our findings suggest a link between simvastatin and Akt/ERK signaling in the regulation of prostate cancer growth and metastasis. Further investigation is currently underway in our laboratory to unravel the molecular mechanisms on simvastatin-mediated effects on prostate cancer leading to tumor growth and bone metastasis in vivo using transgenic mouse models such as AKt+ and TRAMP+ mice. We also plan to undertake a clinical study on patients with prostate cancer who were on statin treatment prior to and after diagnosis and analyze biopsy specimen from these patients. A prospective study will look at the role statins in prostate cancer prevention and/or on management. Our ultimate aim is to investigate if statins can be used as an adjuvant drug in the treatment of patients already diagnosed with prostate cancer. Citation Information: Clin Cancer Res 2010;16(14 Suppl):B47.