?-Tocopherol inhibits the development of prostate adenocarcinoma in prostate specific Pten-/- mice.
ABSTRACT: The PTEN/PI3K/AKT axis plays a critical role in regulating cell growth, differentiation and survival. Activation of this signaling pathway is frequently found in human cancers. Our previous studies demonstrated that ?-tocopherol (?-T) attenuates the activation of AKT by growth factor in prostate cancer cell lines, leading to inhibition of proliferation and induction of apoptosis. Herein, we investigated whether ?-T inhibits the development of prostate adenocarcinoma in prostate-specific Pten-/- (Ptenp-/-) mice in which the activation of AKT is the major driving force for tumorigenesis. By feeding Ptenp-/- mice with AIN93M or 0.2% ?-T supplemented diet starting at the age of 6 or 12 weeks, we found that ?-T treatment reduced prostate adenocarcinoma multiplicity at the age of 40 weeks by 53.3 and 42.7%, respectively. Immunohistochemical (IHC) analysis demonstrated that the phosphorylation of AKT (T308) was reduced in the prostate of the mice administered the ?-T diet. Consistently, proliferation was reduced and apoptosis was increased in prostate lesions of mice on the ?-T diet. Oxidative stress, as determined by IHC staining of 8-OH-dG, was not altered during prostate tumorigenesis, nor was it affected by administration of ?-T. In contrast, ?-tocopherol (?-T) at 0.2% in the diet did not affect prostate adenocarcinoma multiplicity in the Ptenp-/- mice. This finding is consistent with data from our previous study that ?-T, but not ?-T, inhibits the activation of AKT and the growth of prostate cancer cells. Together, these results demonstrate that ?-T inhibits the development of prostate adenocarcinoma in Ptenp-/- mice, mainly through inhibition of AKT activation.
Project description:Vitamin E is a fat-soluble vitamin with antioxidant properties. Tocopherols are the predominant form of vitamin E found in the diet and in supplements and have garnered interest for their potential cancer therapeutic and preventive effects, such as the dephosphorylation of Akt, a serine/threonine kinase with a pivotal role in cell growth, survival, and metabolism. Dephosphorylation of Akt at Ser473 substantially reduces its catalytic activity and inhibits downstream signaling. We found that the mechanism by which ?-tocopherol and ?-tocopherol facilitate this site-specific dephosphorylation of Akt was mediated through the pleckstrin homology (PH) domain-dependent recruitment of Akt and PHLPP1 (PH domain leucine-rich repeat protein phosphatase, isoform 1) to the plasma membrane. We structurally optimized these tocopherols to obtain derivatives with greater in vitro potency and in vivo tumor-suppressive activity in two prostate xenograft tumor models. Binding affinities for the PH domains of Akt and PHLPP1 were greater than for other PH domain-containing proteins, which may underlie the preferential recruitment of these proteins to membranes containing tocopherols. Molecular modeling revealed the structural determinants of the interaction with the PH domain of Akt that may inform strategies for continued structural optimization. By describing a mechanism by which tocopherols facilitate the dephosphorylation of Akt at Ser473, we provide insights into the mode of antitumor action of tocopherols and a rationale for the translational development of tocopherols into novel PH domain-targeted Akt inhibitors.
Project description:This study evaluated the effect of dietary fat on prostate cancer development by using the Hi-Myc mouse transgenic prostate cancer model. Hi-Myc mice develop murine prostatic intraepithelial neoplasia (mPIN) as early as 2 to 4 weeks and invasive adenocarcinoma between 6 and 9 months due to the overexpression of human c-Myc in the mouse prostate. Three-week-old male Hi-Myc mice were placed on high-fat (HF; 42% Kcal) or low-fat (LF; 12% Kcal) diets, and equal caloric intake was maintained until euthanasia at 7 months. The number of mice that developed invasive adenocarcinoma at 7 months was 27% less in the LF diet group (12/28) compared with the HF diet group (23/33, P < 0.05). Epithelial cells in mPIN lesions in the LF group had a significantly lower proliferative index compared with epithelial cells in the HF group (21.7% versus 28.9%, P < 0.05). During the mPIN phase of carcinogenesis (4 months), the LF group had higher serum insulin-like growth factor (IGF) binding protein-1 levels (21.0 +/- 8.9 ng/mL versus 3.2 +/- 0.8 ng/mL, P < 0.05) relative to the HF group. Akt (Ser(473)) phosphorylation, Akt kinase activity, and phosphorylation of downstream targets of Akt in prostates were significantly reduced in the LF diet group compared with the HF group. We conclude that dietary fat reduction delays transition from mPIN to invasive cancer in this Myc-driven transgenic mouse model, possibly through suppression of the IGF-Akt pathway and decreased proliferation of mPIN epithelial cells.
Project description:Male Hi-Myc mice were placed on three dietary regimens [30% calorie restriction (CR), overweight control (modified AIN76A with 10 kcal% fat), and a diet-induced obesity regimen (DIO) 60 kcal% fat]. All diet groups had approximately similar incidence of hyperplasia and low-grade prostatic intraepithelial neoplasia in the ventral prostate at 3 and 6 months of age. However, 30% CR significantly reduced the incidence of in situ adenocarcinomas at 3 months compared with the DIO group and at 6 months compared with both the overweight control and DIO groups. Furthermore, the DIO regimen significantly increased the incidence of adenocarcinoma with aggressive stromal invasion, as compared with the overweight control group (96% vs. 65%, respectively; P = 0.02) at the 6-month time point. In addition, at both 3 and 6 months, only in situ carcinomas were observed in mice maintained on the 30% CR diet. Relative to overweight control, DIO increased whereas 30% CR reduced activation of Akt, mTORC1, STAT3, and NF?B (p65) in ventral prostate. DIO also significantly increased (and 30% CR decreased) numbers of T-lymphocytes and macrophages in the ventral prostate compared with overweight control. The mRNA levels for interleukin (IL) 1?, IL1?, IL6, IL7, IL23, IL27, NF?B1 (p50), TNF?, and VEGF family members were significantly increased in the ventral prostate of the DIO group compared with both the overweight control and 30% CR diet groups. Collectively, these findings suggest that enhanced growth factor (Akt/mTORC1 and STAT3) and inflammatory (NF?B and cytokines) signaling may play a role in dietary energy balance effects on prostate cancer progression in Hi-Myc mice.
Project description:BACKGROUND:Previously, we showed that carbohydrate restriction with calorie restriction slowed tumor growth in xenograft mouse prostate cancer models. Herein, we examined the impact of carbohydrate restriction without calorie restriction on tumor development within the context of diet-induced obesity in the Hi-Myc transgenic mouse model of prostate cancer. METHODS:Mice were randomized at 5 weeks of age to ad libitum western diet (WD; 40% fat, 42% carbohydrate; n=39) or ad libitum no carbohydrate ketogenic diet (NCKD; 82% fat, 1% carbohydrate; n=44). At age 3 or 6 months, mice were killed, prostates weighed and prostate histology, proliferation, apoptosis and macrophage infiltration evaluated by hematoxylin and eosin, Ki67, TUNEL and F4/80 staining, respectively. Body composition was assessed by DEXA, serum cytokines measured using multiplex, and Akt/mTOR signaling assessed by Western. RESULTS:Caloric intake was higher in the NCKD group, resulting in elevated body weights at 6 months of age, relative to the WD group (45?g vs 38g; P=0.008). Despite elevated body weights, serum monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-1? levels were lower in NCKD versus WD mice (P=0.046 and P=0.118, respectively), and macrophage infiltration was reduced in prostates of NCKD versus WD mice (P=0.028). Relative Akt phosphorylation and phospho-S6 ribosomal protein levels were reduced in prostates of NCKD versus WD mice. However, while mice randomized to NCKD had smaller prostates after adjustment for body weight at 3 and 6 months (P=0.004 and P=0.002, respectively), NCKD mice had higher rates of adenocarcinoma at 6 months compared to WD mice (100 vs 80%, P=0.04). CONCLUSIONS:Despite higher caloric intake and elevated body weights, carbohydrate restriction lowered serum MCP-1 levels, reduced prostate macrophage infiltration, reduced prostate weight, but failed to slow adenocarcinoma development. Together, these data suggest that although carbohydrate restriction within the context of obesity may reduce obesity-associated systemic inflammation and perhaps slow tumor growth, it is not sufficient to counteract obesity-associated tumor development.
Project description:Obesity and age are important risk factors for cardiovascular disease. However, the signaling mechanism linking obesity with age-related vascular senescence is unknown. Here we show that mice fed a high-fat diet show increased vascular senescence and vascular dysfunction compared to mice fed standard chow and are more prone to peripheral and cerebral ischemia. All of these changes involve long-term activation of the protein kinase Akt. In contrast, mice with diet-induced obesity that lack Akt1 are resistant to vascular senescence. Rapamycin treatment of diet-induced obese mice or of transgenic mice with long-term activation of endothelial Akt inhibits activation of mammalian target of rapamycin (mTOR)-rictor complex 2 and Akt, prevents vascular senescence without altering body weight, and reduces the severity of limb necrosis and ischemic stroke. These findings indicate that long-term activation of Akt-mTOR signaling links diet-induced obesity with vascular senescence and cardiovascular disease.
Project description:Prostate cancer research has been predominantly focused on adult exposures and risk factors. However, because the prostate develops during gestation and early life, exposure to external factors, such as obesity, during development could affect the prostate cancer progression in adults. Our previous work demonstrated that exposure to a high fat/high sugar (HF/HS) diet during gestation and until weaning stimulated prostate hyperplasia and altered the Pten/Akt pathway in adult mice fed a normal diet after weaning. Here, we asked whether maternal exposure to HF/HS would worsen prostate phenotypes in mice lacking Pten, a widely accepted driver of prostate cancer. We found that, at six weeks of age, both Chow (control)-and HF/HS-exposed Pten knockout mice showed evidence of murine PIN that included ducts with central comedo necrosis but that the HF/HS exposure did not influence murine PIN progression. The Pten knockout mice exposed to HF/HS in utero had significantly more mitotic cells than Pten knockouts exposed to Chow diet. In the Pten null background, the maternal HF/HS diet enhanced proliferation but did not have an additive effect on Akt activation. We observed neuroendocrine differentiation in Pten knockout mice, a phenotype that had not been previously described in this model.
Project description:Prostate cancer is the second leading cause of cancer-related deaths in men. Activation of MAP kinase signaling pathway has been implicated in advanced and androgen-independent prostate cancers, although formal genetic proof has been lacking. In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF(V600E)--a mutation found in approximately 10% of human prostate tumors--was targeted to the epithelial compartment of the prostate gland on the background of Ink4a/Arf deficiency. These GEM mice developed prostate gland hyperplasia with progression to rapidly growing invasive adenocarcinoma without evidence of AKT activation, providing genetic proof that activation of MAP kinase signaling is sufficient to drive prostate tumorigenesis. Importantly, genetic extinction of BRAF(V600E) in established prostate tumors did not lead to tumor regression, indicating that while sufficient to initiate development of invasive prostate adenocarcinoma, BRAF(V600E) is not required for its maintenance.
Project description:Despite recent advances in understanding the biological basis of prostate cancer, management of the disease, especially in the phase resistant to androgen ablation, remains a significant challenge. The long latency and high incidence of prostate carcinogenesis provides the opportunity to intervene with chemoprevention to prevent or eradicate prostate malignancies. In this study, we have used human hormone-resistant prostate cancer cells, DU145 and PC3, as an in vitro model to assess the efficacy of xanthohumol (XN) against cell growth, motility and invasion. We observed that treatment of prostate cancer cells with low micromolar doses of XN inhibits proliferation and modulates focal adhesion kinase (FAK) and AKT phosphorylation leading to reduced cell migration and invasion. Oxidative stress by increased production of reactive oxygen species (ROS) was associated with these effects. Transgenic adenocarcinoma of the mouse prostate (TRAMP) transgenic mice were used as an in vivo model of prostate adenocarcinoma. Oral gavage of XN, three times per week, beginning at 4 wks of age, induced a decrease in the average weight of the urogenital (UG) tract, delayed advanced tumor progression and inhibited the growth of poorly differentiated prostate carcinoma. The ability of XN to inhibit prostate cancer in vitro and in vivo suggests that XN may be a novel agent for the management of prostate cancer.