Biological role of fructose in the male reproductive system: Potential implications for prostate cancer.

BACKGROUND: Over the last 20 years, fructose has gradually emerged as a potential metabolic substrate capable of promoting the growth and progression of various cancers, including prostate cancer (PCa). The biological and molecular mechanisms that underlie the effects of fructose on cancer are beginning to be elucidated. METHODS: This review summarizes the biological function of fructose as a potential carbon source for PCa cells and its role in the functionality of the male reproductive tract under normal conditions. RESULTS: The most recent biological advances related to fructose transport and metabolism as well as their implications in PCa growth and progression suggest that fructose represent a potential carbon source for PCa cells. Consequently, fructose derivatives may represent efficient radiotracers for obtaining PCa images via positron emission tomography and fructose transporters/fructose-metabolizing enzymes could be utilized as potential diagnostic and/or predictive biomarkers for PCa. CONCLUSION: The existing data suggest that restriction of fructose from the diet could be a useful therapeutic strategy for patients with PCa.

Active Surveillance in Prostate Cancer: Current and Potentially Emerging Biomarkers for Patient Selection Criteria.

BACKGROUND: Prostate cancer (PCa) represents one of the most frequent malignancies and the fifth leading cause of cancer death in adult men worldwide. PCa mortality rates have been declining in several Western countries; one of the possible reasons may be related to the application of prostate-specific antigen early detection policies. These early detection protocols increase PCa-specific patient survival; however, a high percentage of these cases corresponds to low-risk PCa that grows very slowly and is unlikely to metastasize to threaten survival. Many low-risk PCa patients receive aggressive therapies, such as radical prostatectomy and radiotherapy, that are costly for patients and/or health systems and generate side effects that affect the quality of life. An alternative to surgery and radiotherapy treatments for low-risk PCa is active surveillance (AS), a strategy based on close disease monitoring and intervention only if the disease progresses. However, proper identification of low-risk PCa patients at the time of diagnosis is essential for the effectiveness AS. The selection of AS candidates remains challenging; thus, effective prognostic biomarkers are needed. SUMMARY: This review article addresses the characteristics of the current and emerging PCa prognostic biomarkers, including tests available for tissue, blood, and urine analyses, for the appropriate selection of PCa patients for AS. In addition, and based on published literature, we performed a selection of potential new biomarkers that can distinguish low-risk PCa. KEY MESSAGES: The literature search yielded four tissue-based tests, two blood-based tests, and six urine-based tests that can be used to determine PCa risk classification. However, most available tests are expensive; thus, cost-effective analyses are needed in order to obtain the approval of government agencies and to be financed by the health systems. Available prognostic urine tests have shown great progress over the last years, and they have the advantage of being minimally invasive; therefore, they may become a routine disease progression test for patients under AS. In addition, new research conducted in the last decade has shown promising biomarkers, including mRNA, miRNA, long noncoding RNA, and metabolites, that could improve existing tests or allow the development of new tools for AS patient selection.

Exercise and prostate cancer: From basic science to clinical applications.

Prostate cancer (PCa) is a disease of increasing medical significance worldwide. In developed countries, PCa is the most common non-skin cancer in men, and one of the leading causes of cancer-related deaths. Exercise is one of the environmental factors that have been shown to influence cancer risk. Moreover, systemic reviews and meta-analysis have suggested that total physical activity is related to a decrease in the risk of developing PCa. In addition, epidemiological studies have shown that exercise, after diagnosis, has benefits regarding PCa development, and positive outcome in patients under treatment. The standard treatment for locally advanced or metastatic PCa is Androgen deprivation therapy (ADT). ADT produces diverse side effects, including loss of libido, changes in body composition (increase abdominal fat), and reduced muscle mass, and muscle tone. Analysis of numerous research publications showed that aerobic and/or resistance training improve patient's physical condition, such us, cardiorespiratory fitness, muscle strength, physical function, body composition, and fatigue. Therefore, exercise might counteract several ADT treatment-induced side effects. In addition of the aforementioned benefits, epidemiological, and in vitro studies have shown that exercise might decrease PCa development. Thus, physical activity might attenuate the risk of PCa and supervised exercise intervention might improve deleterious effects of cancer treatment, such as ADT side effects. This review article provides evidence indicating that exercise could complement, and potentiate, the current standard treatments for advanced PCa, probably by creating an unfavorable microenvironment that can negatively affect tumor development, and progression.

Androgens modulate male-derived endothelial cell homeostasis using androgen receptor-dependent and receptor-independent mechanisms.

BACKGROUND: Sex-related differences in the role of androgen have been reported in cardiovascular diseases and angiogenesis. Moreover, androgen receptor (AR) has been causally involved in the homeostasis of human prostate endothelial cells. However, levels of expression, functionality and biological role of AR in male- and female-derived human endothelial cells (ECs) remain poorly characterized. The objectives of this work were (1) to characterize the functional expression of AR in male- and female-derived human umbilical vein endothelial cell (HUVEC), and (2) to specifically analyze the biological effects of DHT, and the role of AR on these effects, in male-derived HUVECs (mHUVECs). RESULTS: Immunohistochemical analyses of tissue microarrays from benign human tissues confirmed expression of AR in ECs from several androgen-regulated and non-androgen-regulated human organs. Functional expression of AR was validated in vitro in male- and female-derived HUVECs using quantitative RT-PCR, immunoblotting and AR-mediated transcriptional activity assays. Our results indicated that functional expression of AR in male- and female-derived HUVECs was heterogeneous, but not sex dependent. In parallel, we analyzed in depth the biological effects of DHT, and the role of AR on these effects, on proliferation, survival and tube formation capacity in mHUVECs. Our results indicated that DHT did not affect mHUVEC survival; however, DHT stimulated mHUVEC proliferation and suppressed mHUVEC tube formation capacity. While the effect of DHT on proliferation was mediated through AR, the effect of DHT on tube formation did not depend on the presence of a functional AR, but rather depended on the ability of mHUVECs to further metabolize DHT. CONCLUSIONS: (1) Heterogeneous expression of AR in male- and female-derived HUVEC could define the presence of functionally different subpopulations of ECs that may be affected differentially by androgens, which could explain, at least in part, the pleiotropic effects of androgen on vascular biology, and (2) DHT, and metabolites of DHT, generally thought to represent progressively more hydrophilic products along the path to elimination, may have differential roles in modulating the biology of human ECs through AR-dependent and AR-independent mechanisms, respectively.

HDAC 1 and 6 modulate cell invasion and migration in clear cell renal cell carcinoma.

BACKGROUND: Class I histone deacetylases (HDACs) have been reported to be overexpressed in clear cell renal cell carcinoma (ccRCC), whereas the expression of class II HDACs is unknown. METHODS: Four isogenic cell lines C2/C2VHL and 786-O/786-OVHL with differential VHL expression are used in our studies. Cobalt chloride is used to mimic hypoxia in vitro. HIF-2α knockdowns in C2 and 786-O cells is used to evaluate the effect on HDAC 1 expression and activity. Invasion and migration assays are used to investigate the role of HDAC 1 and HDAC 6 expression in ccRCC cells. Comparisons are made between experimental groups using the paired T-test, the two-sample Student's T-test or one-way ANOVA, as appropriate. ccRCC and the TCGA dataset are used to observe the clinical correlation between HDAC 1 and HDAC 6 overexpression and overall and progression free survival. RESULTS: Our analysis of tumor and matched non-tumor tissues from radical nephrectomies showed overexpression of class I and II HDACs (HDAC6 only in a subset of patients). In vitro, both HDAC1 and HDAC6 over-expression increased cell invasion and motility, respectively, in ccRCC cells. HDAC1 regulated invasiveness by increasing matrix metalloproteinase (MMP) expression. Furthermore, hypoxia stimulation in VHL-reconstituted cell lines increased HIF isoforms and HDAC1 expression. Presence of hypoxia response elements in the HDAC1 promoter along with chromatin immunoprecipitation data suggests that HIF-2α is a transcriptional regulator of HDAC1 gene. Conversely, HDAC6 and estrogen receptor alpha (ERα) were co-localized in cytoplasm of ccRCC cells and HDAC6 enhanced cell motility by decreasing acetylated α-tubulin expression, and this biological effect was attenuated by either biochemical or pharmacological inhibition. Finally, analysis of human ccRCC specimens revealed positive correlation between HIF isoforms and HDAC. HDAC1 mRNA upregulation was associated with worse overall survival in the TCGA dataset. CONCLUSIONS: Taking together, these results suggest that HDAC1 and HDAC6 may play a role in ccRCC biology and could represent rational therapeutic targets.

Escaping Antiangiogenic Therapy: Strategies Employed by Cancer Cells.

Tumor angiogenesis is widely recognized as one of the "hallmarks of cancer". Consequently, during the last decades the development and testing of commercial angiogenic inhibitors has been a central focus for both basic and clinical cancer research. While antiangiogenic drugs are now incorporated into standard clinical practice, as with all cancer therapies, tumors can eventually become resistant by employing a variety of strategies to receive nutrients and oxygen in the event of therapeutic assault. Herein, we concentrate and review in detail three of the principal mechanisms of antiangiogenic therapy escape: (1) upregulation of compensatory/alternative pathways for angiogenesis; (2) vasculogenic mimicry; and (3) vessel co-option. We suggest that an understanding of how a cancer cell adapts to antiangiogenic therapy may also parallel the mechanisms employed in the bourgeoning tumor and isolated metastatic cells delivering responsible for residual disease. Finally, we speculate on strategies to adapt antiangiogenic therapy for future clinical uses.

Anti-Inflammatory Chilean Endemic Plants.

Medicinal plants have been used since prehistoric times and continue to treat several diseases as a fundamental part of the healing process. Inflammation is a condition characterized by redness, pain, and swelling. This process is a hard response by living tissue to any injury. Furthermore, inflammation is produced by various diseases such as rheumatic and immune-mediated conditions, cancer, cardiovascular diseases, obesity, and diabetes. Hence, anti-inflammatory-based treatments could emerge as a novel and exciting approach to treating these diseases. Medicinal plants and their secondary metabolites are known for their anti-inflammatory properties, and this review introduces various native Chilean plants whose anti-inflammatory effects have been evaluated in experimental studies. Fragaria chiloensis, Ugni molinae, Buddleja globosa, Aristotelia chilensis, Berberis microphylla, and Quillaja saponaria are some native species analyzed in this review. Since inflammation treatment is not a one-dimensional solution, this review seeks a multidimensional therapeutic approach to inflammation with plant extracts based on scientific and ancestral knowledge.

Cellular distribution of Glut-1 and Glut-5 in benign and malignant human prostate tissue.

Over-expression of hexose transporters (Gluts), specifically Glut-1, is a common event in human malignancies. In prostate cancer (CaP), however, expression of Gluts has been characterized poorly. In this study, expression and distribution of Glut-1 and Glut-5 proteins were characterized using immunohistochemistry in 76 specimens of benign prostate, 10 specimens of high-grade intraepithelial neoplasia (HGPIN), and 28 specimens of CaP. In addition, mRNA expression of Glut-2, Glut-7, Glut-9, and Glut-11 was analyzed in a set of five specimens of benign prostate and CaP. In benign prostate, Glut-1 localized to the basal cells and to the basolateral membrane of secretory/luminal epithelial cells. Glut-5, however, localized to the apical membrane of secretory/luminal epithelial cells. In HGPIN, Glut-1 was immunohistochemically undetectable. Glut-5, however, localized to the apical membrane of the neoplastic epithelial cells. In CaP, Glut-1 and Glut-5, were immunohistochemically undetectable. However, over-expression of GLUT1 was observed in some specimens of highly proliferative intraductal CaP. Glut-7, Glut-9, and Glut-11 mRNAs were detected in benign prostate and CaP, however, only Glut-11 mRNA was consistently up-regulated in CaP compared to benign prostate. Low levels of expression of Glut-1 protein in the majority of CaP could explain, at least in part, the limited clinical applicability of positron emission tomography using 2-[18F]-fluoro-2-deoxy-D-glucose for imaging CaP. Moreover, expression of Glut-5 in HGPIN suggested that fructose could be utilized as potential metabolic substrate in HGPIN. Understanding the molecular mechanisms involved in regulation/dysregulation of Gluts in CaP could provide insight in the understanding of hexose metabolism in CaP.

Altered corepressor SMRT expression and recruitment to target genes as a mechanism that change the response to androgens in prostate cancer progression.

Androgen receptor (AR) is required for the development and progression of prostate cancer (CaP) from androgen-dependence to androgen-resistance. Both corepressors and coactivators regulate AR-mediated transcriptional activity, and aberrant expression or activity due to mutation(s) contributes to changes in AR function in the progression to androgen resistance acquired during hormonal ablation therapies. Primary culture of epithelial cells from androgen-dependent CWR22 and androgen-resistant CWR22R xenograft tumors were used to evaluate the effect of androgens on AR function, and the association with coactivators (SRC-1 and TIF-2) and corepressors (SMRT and NCoR). Both androgen-dependent CWR22 and androgen-resistant CWR22R cells expressed functional AR as the receptor bind ligand with high affinity and increased trafficking to the nuclei in the presence of androgens. However, in the presence of androgens, AR-mediated transcriptional activity in androgen-sensitive CWR22 cells was limited to a 2-fold increase, as compared to a 6-fold increase in androgen-resistance CWR22R cells. In androgen-sensitive CWR22 cells, immunoblot, confocal microscopy, and chromatin immunoprecipitation assays indicated that the androgen bound AR transcriptional initiation complex in the PSA promoter contained corepressor SMRT, resulting in limited receptor transcriptional activity. In contrast, increased AR-mediated transcriptional activity in the CWR22R cells was consistent with decreased expression and recruitment of the corepressors SMRT/NCoR, as well as increased recruitment of the coactivator TIF-2 to the receptor complex. Similar changes in the response to androgens were observed in the LNCaP/C4-2 model of androgen resistance prostate cancer. Thus, altered recruitment and loss of corepressors SMRT/NCoR may provide a mechanism that changes the response of AR function to ligands and contributes to the progression of the advanced stages of human prostate cancer.

Characterization of iNOS(+) Neutrophil-like ring cell in tumor-bearing mice.

BACKGROUND: Myeloid-derived Suppressor Cells (MDSC) have been identified as tumor-induced immature myeloid cells (IMC) with potent immune suppressive activity in cancer. Whereas strict phenotypic classification of MDSC has been challenging due to the highly heterogeneous nature of cell surface marker expression, use of functional markers such as Arginase and inducible nitric oxide synthase (iNOS) may represent a better categorization strategy. In this study we investigated whether iNOS could be utilized as a specific marker for the identification of a more informative homogenous MDSC subset. METHODS: Single-cell suspensions from tumors and other organs were prepared essentially by enzymatic digestion. Flow cytometric analysis was performed on a four-color flow cytometer. Morphology, intracellular structure and localization of iNOS(+) ring cells in the tumor were determined by cytospin analysis, immunofluorescence microscopy and immunohistochemistry, respectively. For functional analysis, iNOS(+) ring subset were sorted and tested in vitro cell culture experiments. Pharmacologic inhibition of iNOS was performed both in vivo and in vitro. RESULTS: The results showed that intracellular iNOS staining distinguished a granular iNOS(+) SSC(hi) CD11b(+) Gr-1(dim) F4/80(+) subset with ring-shaped nuclei (ring cells) among the CD11b(+) Gr-1(+) cell populations found in tumors. The intensity of the ring cell infiltrate correlated with tumor size and these cells constituted the second major tumor-infiltrating leukocyte subset found in established tumors. Although phenotypic analysis demonstrated that ring cells shared characteristics with tumor-associated macrophages (TAM), morphological analysis revealed a neutrophil-like appearance as detected by cytospin and immunofluorescence microscopy analysis. The presence of distinct iNOS filled granule-like structures located next to the cell membrane suggested that iNOS was stored in pre-formed vesicles and available for rapid release upon activation. Tumor biopsies showed large areas with infiltrating ring cells primarily surrounding necrotic areas. Importantly, these cells significantly impaired CD8(+) T-cell proliferation and induced apoptotic death. The intratumoral accumulation and suppressive activity of ring cells could be blocked through pharmacologic inhibition of iNOS, demonstrating the critical role of this enzyme in mediating both the differentiation and the activity of these cells. CONCLUSIONS: In this study, iNOS expression was linked to a homogeneous subset; ring cells with a particular phenotype and immune suppressive function, in a common and well-established murine tumor model; 4T-1. Since the absence of a Gr-1 homolog in humans has made the identification of MDSC much more challenging, use of iNOS as a functional marker of MDSC may also have clinical importance.

The Differential Paracrine Role of the Endothelium in Prostate Cancer Cells.

The survival of patients with solid tumors, such as prostate cancer (PCa), has been limited and fleeting with anti-angiogenic therapies. It was previously thought that the mechanism by which the vasculature regulates tumor growth was driven by a passive movement of oxygen and nutrients to the tumor tissue. However, previous evidence suggests that endothelial cells have an alternative role in changing the behavior of tumor cells and contributing to cancer progression. Determining the impact of molecular signals/growth factors released by endothelial cells (ECs) on established PCa cell lines in vitro and in vivo could help to explain the mechanism by which ECs regulate tumor growth. Using cell-conditioned media collected from HUVEC (HUVEC-CM), our data show the stimulated proliferation of all the PCa cell lines tested. However, in more aggressive PCa cell lines, HUVEC-CM selectively promoted migration and invasion in vitro and in vivo. Using a PCa-cell-line-derived xenograft model co-injected with HUVEC or preincubated with HUVEC-CM, our results are consistent with the in vitro data, showing enhanced tumor growth, increased tumor microvasculature and promoted metastasis. Gene set enrichment analyses from RNA-Seq gene expression profiles showed that HUVEC-CM induced a differential effect on gene expression when comparing low versus highly aggressive PCa cell lines, demonstrating epigenetic and migratory pathway enrichments in highly aggressive PCa cells. In summary, paracrine stimulation by HUVEC increased PCa cell proliferation and tumor growth and selectively promoted migration and metastatic potential in more aggressive PCa cell lines.

Androgen deprivation induces rapid involution and recovery of human prostate vasculature.

The response of the prostate tissue microenvironment to androgen deprivation (AD) represents a critical component in the treatment of benign prostatic hyperplasia and prostate cancer (CaP). Primary xenografts of human benign and CaP tissue transplanted to immunocompromized SCID mice were used to characterize the response of the prostate vasculature during the initial 14 days of AD. Microvessel density and vascular lumen diameter in the prostate xenografts decreased rapidly after AD, reached a nadir on days 2-4, and recovered between days 4 and 14. The number of apoptotic endothelial cells peaked on day 2 after AD and decreased to precastration levels over days 4-7. Leakage of vascular contents in the interstitial space was apparent between days 1 and 3 after AD; however, the vascular permeability barrier reestablished between days 7 and 14. Expression of vascular endothelial growth factor (VEGF)-A, VEGF receptor-2, and basic fibroblast growth factor protein increased in endothelial cells between days 2 and 4 after AD, which preceded vascular recovery and appeared to be a direct and specific response of the endothelial cells to AD. Lack of comparable upregulation of these genes in primary cultures of human prostate endothelial cells in response to AD suggests a role for paracrine signaling mediated through stromal or epithelial cells. VEGF-A expression by prostate endothelial cells appears to represent a key facilitator of the vascular rebound in human prostate tissue induced by removal of circulating testicular androgens.

Intranasal delivery of interferon-ß-loaded nanoparticles induces control of neuroinflammation in a preclinical model of multiple sclerosis: A promising simple, effective, non-invasive, and low-cost therapy.

Multiple sclerosis (MS) is an autoimmune disease affecting the central nervous system (CNS). Interferon (IFN)-ß constitutes one of the first-line therapies to treat MS, but has limited efficacy due to the injectable systemic administration, short half-life, and limited CNS access. To address these limitations, we developed IFN-ß-loaded chitosan/sulfobutylether-ß-cyclodextrin nanoparticles (IFN-ß-NPs) for delivery of IFN-ß into the CNS via the intranasal (i.n.) route. The nanoparticles (NPs) (≈200 nm, polydispersity ≈0.1, and zeta potential ≈20 mV) were prepared by mixing two aqueous solutions and associated human or murine IFN-ß with high efficiency (90%). Functional in vitro assays showed that IFN-ß-NPs were safe and that IFN-ß was steadily released while retaining biological activity. Biodistribution analysis showed an early and high fluorescence in the brain after nasal administration of fluorescent probe-loaded NPs. Remarkably, mice developing experimental autoimmune encephalomyelitis (EAE), an experimental model of MS, exhibited a significant improvement of clinical symptoms in response to intranasal IFN-ß-NPs (inIFN-ß-NPs), whereas a similar dose of intranasal or systemic free IFN-ß had no effect. Importantly, inIFN-ß-NPs treatment was equally effective despite a reduction of 78% in the total amount of weekly administered IFN-ß. Spinal cords obtained from inIFN-ß-NPs-treated EAE mice showed fewer inflammatory foci and demyelination, lower expression of antigen-presenting and costimulatory proteins on CD11b+ cells, and lower astrocyte and microglia activation than control mice. Therefore, IFN-ß treatment at tested doses was effective in promoting clinical recovery and control of neuroinflammation in EAE only when associated with NPs. Overall, inIFN-ß-NPs represent a potential, effective, non-invasive, and low-cost therapy for MS.

Dietary Fructose Promotes Prostate Cancer Growth.

Clinical localization of primary tumors and sites of metastasis by PET is based on the enhanced cellular uptake of 2-deoxy-2-[18F]-fluoro-D-glucose (FDG). In prostate cancer, however, PET-FDG imaging has shown limited clinical applicability, suggesting that prostate cancer cells may utilize hexoses other than glucose, such as fructose, as the preferred energy source. Our previous studies suggested that prostate cancer cells overexpress fructose transporters, but not glucose transporters, compared with benign cells. Here, we focused on validating the functional expression of fructose transporters and determining whether fructose can modulate the biology of prostate cancer cells in vitro and in vivo. Fructose transporters, Glut5 and Glut9, were significantly upregulated in clinical specimens of prostate cancer when compared with their benign counterparts. Fructose levels in the serum of patients with prostate cancer were significantly higher than healthy subjects. Functional expression of fructose transporters was confirmed in prostate cancer cell lines. A detailed kinetic characterization indicated that Glut5 represents the main functional contributor in mediating fructose transport in prostate cancer cells. Fructose stimulated proliferation and invasion of prostate cancer cells in vitro. In addition, dietary fructose increased the growth of prostate cancer cell line-derived xenograft tumors and promoted prostate cancer cell proliferation in patient-derived xenografts. Gene set enrichment analysis confirmed that fructose stimulation enriched for proliferation-related pathways in prostate cancer cells. These results demonstrate that fructose promotes prostate cancer cell growth and aggressiveness in vitro and in vivo and may represent an alternative energy source for prostate cancer cells. SIGNIFICANCE: This study identifies increased expression of fructose transporters in prostate cancer and demonstrates a role for fructose as a key metabolic substrate supporting prostate cancer cells, revealing potential therapeutic targets and biomarkers.

Oct4A is expressed by a subpopulation of prostate neuroendocrine cells.

BACKGROUND: Cancer stem cells are defined by their self-renewal and multi-potential capabilities and are hypothesized to be the source of primary and recurrent cancers. The stem cell properties of self-renewal and pluripotency in embryonic stem cells and germ cells are regulated by Oct4A, a splice variant of the POU5F1 (Oct3/4) gene, while the function of the alternative splice variant, Oct4B, is unknown. Rare cells that express Oct4 were identified in several somatic cancers, however, the differential contributions of the Oct4A and Oct4B variants were not determined. METHODS: Oct4A expression and co-localization with lineage markers was performed with PCR and immunohistochemistry. RESULTS: Rare Oct4A expressing cells are present in human benign and malignant prostate glands and the number of Oct4A expressing cells increases in prostate cancers with high Gleason scores. Oct4A expressing cells were non-proliferative, and did not co-express markers of basal epithelial cell or luminal epithelial cell differentiation, or AMACR, a marker of prostate cancer epithelial cells. A subpopulation of the Oct4A expressing cells co-expressed Sox2, an embryonic stem cell marker, but did not express other putative stem cell markers, such as ABCG2, NANOG or CD133. The majority of Oct4A expressing cells co-expressed chromogranin A, and a subset of Oct4A expressing cells co-expressed synaptophysin, both markers of neuroendocrine differentiation. CONCLUSION: The increased number of cells that expressed Oct4A in prostate cancer compared to benign prostate, and in cancers of increasing grade, suggests that Oct4A/Chromogranin A co-expressing cells represent neuroendocrine cells in prostate cancer.

Fructose and prostate cancer: toward an integrated view of cancer cell metabolism.

Activation of glucose transporter-1 (Glut-1) gene expression is a molecular feature of cancer cells that increases glucose uptake and metabolism. Increased glucose uptake is the basis for the clinical localization of primary tumors using positron emission tomography (PET) and 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) as a radiotracer. However, previous studies have demonstrated that a considerable number of cancers, which include prostate cancer (CaP), express low to undetectable levels of Glut-1 and that FDG-PET has limited clinical applicability in CaP. This observation could be explained by a low metabolic activity of CaP cells that may be overcome using different hexoses, such as fructose, as the preferred energy source. However, these hypotheses have not been examined critically in CaP. This review article summarizes what is currently known about transport and metabolism of hexoses, and more specifically fructose, in CaP and provides experimental evidences indicating that CaP cells may have increased capacity to transport and metabolize fructose in vitro and in vivo. Moreover, this review highlights recent findings that allow better understanding of how metabolism of fructose may regulate cancer cell proliferation and how fructose uptake and metabolism, through the de novo lipogenesis pathway, may provide new opportunities for CaP early diagnosis, staging, and treatment.

Androgen receptor is causally involved in the homeostasis of the human prostate endothelial cell.

Androgen deprivation causes a reduction of blood flow in the prostate gland that precedes temporally apoptosis of the epithelium. The acute response of prostate endothelial cells to androgen deprivation suggested they represent a primary target for androgen. However, rat prostate endothelial cells were reported not to express androgen receptor (AR), and the role of the androgen axis in human prostate endothelial cell (HPEC) homeostasis was poorly characterized. In this study AR expression was detected in HPEC in vivo in clinical specimens of benign prostate and prostate cancer, and AR function as a transcription factor was demonstrated in HPEC in primary xenografts of human benign prostate tissue transplanted into severe combined immunodeficient mice by iv administration of adenoviral mouse mammary tumor virus-driven luciferase expression vector. AR expression and functionality were maintained in vitro in primary cultures of HPEC that coexpressed CD31, CD34, von Willebrand factor, intercellular adhesion molecule, vascular endothelial growth factor receptor 1, and vascular endothelial growth factor receptor 2 but did not express prostate-specific antigen. AR expression in primary cultures of HPEC isolated from surgical specimens of benign prostate was validated using RT-PCR, cDNA sequencing, immunocytochemistry, and Western blot analyses. Scatchard analyses demonstrated a single ligand-binding site for R1881 in primary cultures of HPEC, with dissociation constant of 0.25 nm, and AR-mediated transcriptional activity was demonstrated using adenoviral mouse mammary tumor virus-driven luciferase reporters. Dihydrotestosterone increased proliferation in primary cultures of HPEC in a dose-dependent manner without modulating endothelial tube formation in Matrigel (BD Biosciences, Bedford, MA). Therefore, HPECs express functional AR, and androgen plays a direct role in modulating HPEC biology.

Androgen receptor in human endothelial cells.

Androgen receptor (AR) is a ligand-inducible transcription factor, and a member of the steroid-thyroid-retinoid receptor superfamily, that mediates the biological effects of androgens in a wide range of physiological and pathological processes. AR expression was identified in vascular cells nearly 20 years ago, and recent research has shown that AR mediates a variety of actions of androgens in endothelial and vascular smooth muscle cells. In this mini-review, we review evidence indicating the importance of AR in human endothelial cell (HUVEC) homeostatic and pathogenic processes. Although a role for AR in the modulation of HUVEC biology is evident, the molecular mechanisms by which AR regulates HUVEC homeostasis and disease processes are not fully understood. Understanding these mechanisms could provide critical insights into the processes of pathogenesis of diseases ranging from cardiovascular disease to cancer that are major causes of human morbidity and mortality.

Sunitinib dose escalation overcomes transient resistance in clear cell renal cell carcinoma and is associated with epigenetic modifications.

Sunitinib is considered a first-line therapeutic option for patients with advanced clear cell renal cell carcinoma (ccRCC). Despite sunitinib's clinical efficacy, patients eventually develop drug resistance and disease progression. Herein, we tested the hypothesis whether initial sunitinib resistance may be transient and could be overcome by dose increase. In selected patients initially treated with 50 mg sunitinib and presenting with minimal toxicities, sunitinib dose was escalated to 62.5 mg and/or 75 mg at the time of tumor progression. Mice bearing two different patient-derived ccRCC xenografts (PDX) were treated 5 days per week with a dose-escalation schema (40-60-80 mg/kg sunitinib). Tumor tissues were collected before dose increments for immunohistochemistry analyses and drug levels. Selected intrapatient sunitinib dose escalation was safe and several patients had added progression-free survival. In parallel, our preclinical results showed that PDXs, although initially responsive to sunitinib at 40 mg/kg, eventually developed resistance. When the dose was incrementally increased, again we observed tumor response to sunitinib. A resistant phenotype was associated with transient increase of tumor vasculature despite intratumor sunitinib accumulation at higher dose. In addition, we observed associated changes in the expression of the methyltransferase EZH2 and histone marks at the time of resistance. Furthermore, specific EZH2 inhibition resulted in increased in vitro antitumor effect of sunitinib. Overall, our results suggest that initial sunitinib-induced resistance may be overcome, in part, by increasing the dose, and highlight the potential role of epigenetic changes associated with sunitinib resistance that can represent new targets for therapeutic intervention.

Dll4 blockade potentiates the anti-tumor effects of VEGF inhibition in renal cell carcinoma patient-derived xenografts.

BACKGROUND: The Notch ligand Delta-like 4 (Dll4) is highly expressed in vascular endothelium and has been shown to play a pivotal role in regulating tumor angiogenesis. Blockade of the Dll4-Notch pathway in preclinical cancer models has been associated with non-productive angiogenesis and reduced tumor growth. Given the cross-talk between the vascular endothelial growth factor (VEGF) and Delta-Notch pathways in tumor angiogenesis, we examined the activity of a function-blocking Dll4 antibody, REGN1035, alone and in combination with anti-VEGF therapy in renal cell carcinoma (RCC). METHODS AND RESULTS: Severe combined immunodeficiency (SCID) mice bearing patient-derived clear cell RCC xenografts were treated with REGN1035 and in combination with the multi-targeted tyrosine kinase inhibitor sunitinib or the VEGF blocker ziv-aflibercept. Immunohistochemical and immunofluorescent analyses were carried out, as well as magnetic resonance imaging (MRI) examinations pre and 24 hours and 2 weeks post treatment. Single agent treatment with REGN1035 resulted in significant tumor growth inhibition (36-62%) that was equivalent to or exceeded the single agent anti-tumor activity of the VEGF pathway inhibitors sunitinib (38-54%) and ziv-aflibercept (46%). Importantly, combination treatments with REGN1035 plus VEGF inhibitors resulted in enhanced anti-tumor effects (72-80% growth inhibition), including some tumor regression. Magnetic resonance imaging showed a marked decrease in tumor perfusion in all treatment groups. Interestingly, anti-tumor efficacy of the combination of REGN1035 and ziv-aflibercept was also observed in a sunitinib resistant ccRCC model. CONCLUSIONS: Overall, these findings demonstrate the potent anti-tumor activity of Dll4 blockade in RCC patient-derived tumors and a combination benefit for the simultaneous targeting of the Dll4 and VEGF signaling pathways, highlighting the therapeutic potential of this treatment modality in RCC.