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.

Intranasal delivery of interferon-β-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)-β 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-β-loaded chitosan/sulfobutylether-β-cyclodextrin nanoparticles (IFN-β-NPs) for delivery of IFN-β 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-β with high efficiency (90%). Functional in vitro assays showed that IFN-β-NPs were safe and that IFN-β 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-β-NPs (inIFN-β-NPs), whereas a similar dose of intranasal or systemic free IFN-β had no effect. Importantly, inIFN-β-NPs treatment was equally effective despite a reduction of 78% in the total amount of weekly administered IFN-β. Spinal cords obtained from inIFN-β-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-β treatment at tested doses was effective in promoting clinical recovery and control of neuroinflammation in EAE only when associated with NPs. Overall, inIFN-β-NPs represent a potential, effective, non-invasive, and low-cost therapy for MS.

Abstract B007: Stemness features of prostate cancer cells induced by carcinoma-associated fibroblasts

Introduction: Carcinoma-associated fibroblasts (CAFs) play a key role during cancer progression through several mechanisms, including the induction of the epithelial-mesenchymal transition (EMT) program, giving cancer cells the ability to initiate metastasis. As the cells progress to the mesenchymal state they acquire properties of cancer stem cells (CSC) or mesenchymal stem cell (MSC). However, the contribution of the CAFs in the acquisition of the differential stemness is largely unknown. Here, we studied the stemness features of prostate cancer cells (PC3) during the EMT program induced by fibroblasts obtained from patients with nonmetastatic prostate cancer (CAF) and bone metastatic prostate cancer (mCAF).

Materials and Methods: PC3 cells were incubated with conditioned medium (CM) of CAF and mCAF for 7,14, and 21 days to induced EMT. The presence of putative CSCs and MSCs was determined by qPCR, immunocytochemistry and Western blot for the expression of CSCs and MSCs markers, respectively, and functionally evaluated by the ability to perform adipogenic, chondrogrenic, and osteogenic differentiation (MSCs) and in vitro spheroids formation and clonogenic assay (CSCs).

Results and Discussion: Our results demonstrate that cancer cells treated with CM-CAF undergo to a partial EMT program, exhibiting certain mesenchymal traits and enriched for cancer stem cells (CSCs). On the other hand, tumor cells exposed to CM-mCAF, exhibited a full EMT conversion with the greater abilities to migrate and invade in vitro and in vivo. This suggests that CAFs and mCAFs induce differential EMT programs in prostate cancer cells, which leads them to acquire CSCs or MSC features enhancing the metastatic capabilities. (FONDECYT 1150397.)

Citation Format: Muriel A. Nuñez, Javier Cerda-Infante, Marianela Sánchez, Paula Sotomayor, Alejandro S. Godoy, Viviana P. Montecinos. Stemness features of prostate cancer cells induced by carcinoma-associated fibroblasts [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B007.

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.

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.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2604-7) contains supplementary material, which is available to authorized users.

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.

Abstract 4061: Evidence for hdac6 and er-α association in a subset of clear cell renal cell carcinoma

Introduction: Histone deacetylases are overexpressed in several tumors including prostate, breast and clear cell renal cell carcinoma (ccRCC). Our group has previously reported that class II HDACs, HDAC4 and HDAC6 regulate HIF-α stability in ccRCC cell lines. Interestingly, HDAC6 overexpression in ER-α positive breast cancer has been shown to correlate with overall and cancer specific survival in response to tamoxifen treatment. In addition, HDAC6 increases cell motility by deacetylating α-tubulin, and HDAC6 interaction with ER-α on the cell membrane increases its deacetylating activity. The objective of our study was to assess whether HDAC6 associates with ER-α in a subset of ccRCC and whether this association can be targeted therapeutically. Methods: Radical nephrectomy tumor samples (n=14) with matched adjacent non tumor tissues were collected and analyzed for HDAC6 expression by Western blot analysis. HDAC6 expression was also assessed in C2, C2VHL and 786-O ccRCC cell lines by Western blot and immunofluorescence analysis. HDAC6 and ER-α colocalization was examined by immunoprecipitation and immunofluorescence. HDAC 6 was overexpressed in cell lines and investigated for cell motility by scratch assay. Cell lines were also treated with hydroxy tamoxifen in short term (4 hours) and long term (24, 48 and 72 hours) culture experiments for evaluation of effects on acetylated α-tubulin and cell proliferation, respectively. Results: Analysis of matched patient tumor samples revealed that a subset of ccRCC had higher HDAC6 expression as compared to the adjacent non tumor tissue. HDAC6 and ER-α examined in ccRCC tumors (n=44) by immunofluorescence showed overexpression in 10% of tumor samples. Immunoprecipitation of HDAC 6 in ccRCC cell lines showed that ER-α is present in the same complex as HDAC 6 as confirmed also by fluorescence microscopy. HDAC6 overexpression in ccRCC cell lines increased cell motility, although overexpression did not affect cell proliferation. Cells treated for short term experiments with hydroxy tamoxifen showed an increase in acetylated α-tubulin when examined by immunofluorescence. Upon long term hydroxy tamoxifen treatment in regular DMEM medium with serum, ccRCC cell proliferation was affected at high concentrations (10-20µM), similar to MCF 7 cells treated under similar conditions. Conclusions: HDAC 6 and ER-α are overexpressed in a subset of ccRCC. HDAC6 overexpression affects cell motility but not proliferation. HDAC6 and ER-α are present in the same immunocomplex and this association may be targeted with therapeutic interventions. Ongoing studies are testing concomitant, either genetic or pharmacological, inhibition of both HDAC6 and ER-α in ccRCC and will provide the rationale for novel targeted therapies for a selected group of patients with ccRCC.

Citation Format: Swathi Ramakrishnan, Sheng-Yu Ku, Wendy Swetzig, Dylan Conroy, Li Shen, Sreenivasulu Chintala, Paula Sotomayor, Kiersten M. Miles, Remi Adelaiye, Eric Ciamporcero, Ashley Orillion, Leigh Ellis, Gokul Das, Roberto Pili. Evidence for hdac6 and er-α association in a subset of clear cell renal cell carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4061. doi:10.1158/1538-7445.AM2014-4061

Overcoming sunitinib-induced resistance by dose escalation in renal cell carcinoma: Evidence in animal models and patients

4582

Background: Sunitinib is considered a first-line therapeutic option for patients with advanced clear cell renal cell carcinoma (ccRCC). However, despite the clinical efficacy, eventually tumors develop resistance and progress. Thus, we have tested the hypothesis whether sunitinib dose-escalation could overcome initial drug resistance. Methods: Human patient-derived ccRCC xenografts were implanted in SCID mice and were randomly assigned into two groups (sunitinib and vehicle). Mice were treated with sunitinib 5 days/week with a dose-escalation schema starting from 40 mg/kg to 60 mg/kg and 80 mg/kg. Tumor volumes and body weights were assessed weekly. Tumor tissues and blood were collected prior to dose increments. In selected patients treated with 50 mg sunitinib and presenting minimal toxicities, dose was escalated to 62.5 and 75 mg at the time of tumor progression. Results: Our preclinical results show that patient-derived tumors (RP-01 and RP-02), although initially responsive to sunitinib 40 mg/kg, eventually became resistant to treatment. Following dose increase to 60 mg/kg, we observed again tumor response but eventually the tumors became resistant. A similar effect was noticed when we further escalated sunitinib to 80 mg/kg. Immunohistochemistry analysis shows decreased tumor vascularization during response to sunitinib, but then hypervascularization at the time of resistance. Associated increase in expression of the methyltransferase EZH2, the histone marks H3K27me3, H3k4me2 and H3K9me2 in tumors resistant to sunitinib was observed. Analysis of sunitinib and VEGF/VEFGR2 blood and tumor levels will be reported. In parallel, our clinical experience shows that intra-patient sunitinib dose-escalation was safe and clinical benefit was observed. Details on tumor responses and toxicities will be reported. Conclusions: Overall, our results suggest that sunitinib-induced resistance may be overcome in part by increasing the dose of the VEGF receptor tyrosine kinase inhibitor in mouse models and ccRCC patients, and highlights the potential role of epigenetic changes associated with sunitinib resistance.

Abstract 2987: VHL dependent and independent regulation of HDAC expression and activity in renal cell carcinomas

Background: Histone modifications include addition and/or deletion of acetyl and methyl groups to lysine, serine and arginine residues of the histone tails leading to transcriptional inactivation or activation. The enzymes governing these modifications are histone acetyl transferases (HATs), histone deacetylases (HDACs), histone methylases (HMTs) and histone demethylases (HDMTs). HDAC inhibitors exert their inhibitory effects on tumor cell population through cell cycle inhibition, apoptosis, decreased cell proliferation as well as their induction of tumor suppressor genes (for eg: p53). Clear cell renal cell carcinoma (ccRCC) represents the dominant major subtype of RCC malignancy with frequent mutations, deletions or methylation in the tumor suppressor gene Von-Hippel Lindau (VHL). Class I HDACs have been reported to be overexpressed in ccRCCs and VHL protein is present in the same complex containing class I HDACs. The present study was aimed at defining the role of VHL in the regulation of HDAC expression and activity. Methods: Approximately 15 ccRCC tumors and matched normal kidney samples from nephrectomies were collected. Western blot analysis of UMRC-2 (VHL−/− RCC cell line) and UMRC2 (wt-VHL RCC cell line) were carried out under conditions of normoxia, hypoxia and in the presence of proteasomal inhibitor MG-132. Tumor cells (1 x 107) were injected subcutaneously in SCID mice to establish tumor xenografts. Results: Our preliminary studies in matched clinical tumor samples show overexpression of specific Class I (2 fold increase; p<0.05) and II HDACs (5 fold increase for HDAC 4). Conversely, HDAC 6 expression (2 fold decrease, p<0.01) and activity was down regulated in tumor samples. To investigate the role of VHL in RCCs, UMRC2 and UMRC2-VHL were utilized for HDAC expression and activity. Western blot analysis indicated HDAC 1 down regulation (1.5 fold) and HDAC 6 overexpression (1.5 fold) in the UMRC2 cells as compared to the UMRC2-VHL cells. In contrast, HDAC 6 activity, measured by expression of its target protein acetylated α-tubulin, was lower in the UMRC2 cells. Under hypoxic conditions both HDAC 1 and HDAC 6 were induced in the UMRC2-VHL cells suggesting VHL dependent hypoxic regulation of these HDACs. MG-132 induced HDAC 1 and 6 in UMRC2-VHL; whereas proteasome inhibitor down regulated HDAC 1 and 6 in UMRC2 cells suggesting a VHL independent mechanism of HDAC regulation. In vivo studies of tumor xenografts generated from the cell lines demonstrated hypoxic induction of HDAC 1 (5 fold increase) and HDAC 6 in UMRC2 when compared to the UMRC2-VHL tumors. Conclusion: Our results suggest that specific HDACs are differentially regulated by VHL dependent (via hypoxia regulation) and independent mechanisms, providing a rationale for testing selective HDAC inhibitors in RCCs.

Citation Format: Swathi Ramakrishnan, Paula Sotomayor, Leigh Ellis, Sreenivasulu Chintala, Roberto Pili. VHL dependent and independent regulation of HDAC expression and activity in renal cell carcinomas. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2987. doi:10.1158/1538-7445.AM2013-2987

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.

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.

Abstract 5016: Epigenetics in renal cell carcinoma

In 2011, an estimated 60,920 men and women will be diagnosed of which 13,120 will die of cancer of the kidney and renal pelvis. The current standard line of therapy includes surgery [partial or radical nephrectomy] or the use of molecular targeted agents such as antiangiogenic agents or immunotherapy. The common mutations found in renal cell carcinomas [RCC] are Von-Hippau Lindau [VHL] gene in clear cell RCC, c-met gene in papillary RCC type I, Fumarate hydratase [FH] gene in papillary type II or the Brit Hogg Dube’ [BHD] gene in chromophobe RCC. However there have been several studies indicating that some of the above genes like VHL can be silenced through promoter methylation as well. Hence, there has been an increasing focus on epigenetic modifications that can occur in RCCs, because of the possibility of reversing these epigenetic marks. There have been considerable reports on the use of agents such as histone deacetylase [HDAC] inhibitors or DNA methyl transferase inhibitors in different RCC cell lines or clinical trials. In this study, we looked at the HDAC expression and activity in matched tumor and non-tumor renal cell carcinoma tissue obtained from tissue procurement services at RPCI. Class I HDACs [HDAC 1, 2 and 3] and two members of class II HDACs [HDAC 4 and 5] are overexpressed in tumors compared to their non-tumor counterparts. In contrast, a class II member HDAC 6 level is lower in the tumor tissues relative to their non-tumor counterparts which corresponded to higher levels to acetylated α-tubulin in those tumors. However, these HDAC expression levels did not tend to have a correlation with grade or stage. We also established xenografts, that are implanted orthotopically and efforts are underway to obtain relatively faster growing tumors subcutaneously. Ongoing studies include defining the relation between expression and activity of HDACs in these tissues and the interaction and impact of other proteins with Class I and II HDACs [such as ER-α, Class III HDACs, VHL] in the context of common active pathways in tumors such as hypoxia [results of which will be available at the time of the meeting]. Further work also includes to look into other histone as well as DNA modifications, as well as enzymes that cause these modifications, in the matched tissues and to explore the potential use of histone or DNA modifying agents as part of RCC treatment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5016. doi:1538-7445.AM2012-5016

Abstract 4380: Effect of sunitinib on endothelial-pericyte cell interaction

Background: Sunitinib is a multitargeted tyrosine kinase receptor inhibitor, which has been used for the last 5 years as an anti-angiogenic drug for the treatment of metastasic renal cell carcinoma (RCC). Sunitinib treatment induces an initial favorable response in patients with RCC, however, resistant to sunitinib occurs in the majority of patients after ∼11 months of treatment. One of the mechanism that has been hypothesized to explain the resistance of RCC to sunitinib is an increase in pericyte cell coverage in the tumor vasculature. In vivo, pericytes and endothelial cells are in close proximity and they frequently have direct contact with each other through gap junctions. Endothelial-pericytes interactions regulate vascular development, endothelial cell permeability, vessel stabilization, vessel maturation, and remodeling. Moreover, pericytes have been demonstrated to secrete paracrine factors that stimulate signaling pathways implicated in endothelial cell differentiation and survival. Previous studies have shown that anti-angiogenic drugs may disrupt the physical interaction between endothelial cells and pericytes in vivo. Moreover, in vitro studies have demonstrated that the loss of endothelial-pericyte contact may decrease the level of expression of SMA and NG2, the two most important pericyte markers used in vivo. The aim of this study is to analyze the endothelial-pericyte cell interactions in vitro and the effect that sunitinib has in these interactions. Methods and Results: HUVEC (Human Umbilical Vein Endothelial Cells) and hPC-PL (Human Pericytes from Placenta) cells were utilized to characterize in vitro the effect of sunitinib in endothelial-pericyte cell interactions. The effect of sunitinib in cell proliferation of each primary culture was determined by using crystal violet and growth curve assays. Sunitinib, at 1uM concentration, decreases proliferation rate of endothelial and pericyte cells, process that was reversible after sunitinib withdrawal. Cocultures of HUVEC and hPC-PL cells showed that both cells types start to physically interact after 24 hours. After 48 hours of co-culture, hPC-PL cells in close proximity to endothelial cells overexpressed the pericyte markers NG2 and SMA, process that have been reported to be dependent on gap junction formation. Use of conditioned media obtained from endothelial cells did not induce overexpression of NG2 or SMA in hPC-PL cells, which suggests physical contact between pericyte and endothelial cells was necessary for pericyte to over-express NG2 and SMA. In addition, co-culture experiments performed in the presence of sunitinib did not affect the physical cell-to-cell interaction between HUVEC and hPC-PL. Conclusion: These results indicate endothelial-pericyte cell interactions are not only an important mechanism for endothelial survival signaling, but also are necessary to maintain pericyte differentiation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4380. doi:1538-7445.AM2012-4380

Class I histone deacetylase inhibitor entinostat suppresses regulatory T cells and enhances immunotherapies in renal and prostate cancer models

Background

Immunosuppressive factors such as regulatory T cells (Tregs) limit the efficacy of immunotherapies. Histone deacetylase (HDAC) inhibitors have been reported to have antitumor activity in different malignancies and immunomodulatory effects. Herein, we report the Tregs-targeting and immune-promoting effect of a class I specific HDAC inhibitor, entinostat, in combination with either IL-2 in a murine renal cell carcinoma (RENCA) model or a survivin-based vaccine therapy (SurVaxM) in a castration resistant prostate cancer (CR Myc-CaP) model.

Methods and Results

RENCA or CR Myc-CaP tumors were implanted orthotopically or subcutaneously, respectively. Inoculated mice were randomized into four treatment groups: vehicle, entinostat, cytokine or vaccine, and combination. Tregs in the blood were assessed by FACS analysis. Real time quantitative PCR and Western blot analysis of isolated T cell subpopulations from spleen were performed to determine Foxp3 gene and protein expression. The suppressive function of Tregs was tested by T cell proliferation assay. Low dose (5 mg/kg) entinostat reduced Foxp3 levels in Tregs and this was associated with enhanced tumor growth inhibition in combination with either IL-2 or a SurVaxM vaccine. Entinostat down-regulated Foxp3 expression transcriptionally and blocked Tregs suppressive function without affecting T effector cells (Teffs). In vitro low dose entinostat (0.5 µM) induced STAT3 acetylation and a specific inhibitor of STAT3 partially rescued entinostat-induced down-regulation of Foxp3, suggesting that STAT3 signaling is involved in Foxp3 down-regulation by entinostat.

Conclusions

These results demonstrate a novel immunomodulatory effect of class I HDAC inhibition and provide a rationale for the clinical testing of entinostat to enhance cancer immunotherapy.

Vascular disruption in combination with mTOR inhibition in renal cell carcinoma

Renal cell carcinoma (RCC) is an angiogenesis-dependent and hypoxia-driven malignancy. As a result, there has been an increased interest in the use of antiangiogenic agents for the management of RCC in patients. However, the activity of tumor-vascular disrupting agents (tumor-VDA) has not been extensively examined against RCC. In this study, we investigated the therapeutic efficacy of the tumor-VDA ASA404 (DMXAA, 5,6-dimethylxanthenone-4-acetic acid, or vadimezan) in combination with the mTOR inhibitor everolimus (RAD001) against RCC. In vitro studies were carried out using human umbilical vein endothelial cells and in vivo studies using orthotopic RENCA tumors and immunohistochemical patient tumor-derived RCC xenografts. MRI was used to characterize the vascular response of orthotopic RENCA xenografts to combination treatment. Therapeutic efficacy was determined by tumor growth measurements and histopathologic evaluation. ASA404/everolimus combination resulted in enhanced inhibition of endothelial cell sprouting in the 3-dimensional spheroid assay. MRI of orthotopic RENCA xenografts revealed an early increase in permeability 4 hours posttreatment with ASA404, but not with everolimus. Twenty-four hours after treatment, a significant reduction in blood volume was observed with combination treatment. Correlative CD31/NG2 staining of tumor sections confirmed marked vascular damage following combination therapy. Histologic sections showed extensive necrosis and a reduction in the viable rim following combination treatment compared with VDA treatment alone. These results show the potential of combining tumor-VDAs with mTOR inhibitors in RCC. Further investigation into this novel combination strategy is warranted.

TAK1-TAB2 signaling contributes to bone destruction by breast carcinoma cells

Advanced-stage breast cancers frequently metastasize to the bones and cause bone destruction, but the underlying mechanism is not fully understood. This study presents evidence that TGF-β-activated protein kinase 1 (TAK1) signaling in tumor cells promotes bone destruction by metastatic breast carcinoma cells, controlling expression of prometastatic factors including matrix metalloproteinase (MMP) 9 and COX2. Suppression of TAK1 signaling by dominant-negative TAK1 (dn-TAK1) in breast carcinoma MDA-MB-231 cells impairs bone colonization by carcinoma cells and bone osteolysis in the intracardiac injection model. Mechanistic studies showed that inhibition of TAK1 by dn-TAK1 or siRNA blocked expression of factors implicated in bone metastasis, such as MMP-9, COX2/PTGS2, parathyroid hormone-related protein (PTHrP) and interleukin 8 (IL-8), but did not affect activation of p38MAPK by TGF-β. TAK1 signaling is mediated by TAK1-binding partners TAB1, TAB2, and TAB3. Carcinoma cells express elevated mRNA levels of TAB2 and TAB3, whereas the TAB1 expression is noticeably low. Accordingly, depletion of TAB2 by siRNA reduced expression of MMP-9 and COX2. Together, these studies show that the TAK1-TAB2-TAB3 signaling axis is critical for carcinoma-induced bone lesions, mediating expression of proinvasive and osteolytic factors. These findings identify the TAK1-TAB2 axis as a potential therapeutic target in bone metastasis.

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.

Induction of cell cycle arrest and DNA damage by the HDAC inhibitor panobinostat (LBH589) and the lipid peroxidation end product 4-hydroxynonenal in prostate cancer cells

Histone deacetylase inhibitors (HDACIs) are promising antineoplastic agents for the treatment of cancer. Here we report that the lipid peroxidation end product 4-hydroxynonenal (HNE) significantly potentiates the anti-tumor effects of the HDAC inhibitor panobinostat (LBH589) in the PC3 prostate cancer cell model. Panobinostat and HNE inhibited proliferation of PC3 cells and the combination of the two agents resulted in a significant combined effect. Cell cycle analysis revealed that both single agents and, to a greater extent, their combined treatment induced G2/M arrest, but cell death occurred in the combined treatment only. Furthermore, HNE and, to a greater extent, the combined treatment induced dephosphorylation of Cdc2 leading to progression into mitosis as confirmed by α-tubulin/DAPI staining and phospho-histone H3 (Ser10) analysis. To evaluate possible induction of DNA damage we utilized the marker phosphorylated histone H2A.X. Results showed that the combination of panobinostat and HNE induced significant DNA damage concomitant with the mitotic arrest. Then, by using androgen receptor (AR)-expressing PC3 cells we observed that the responsiveness to HNE and panobinostat was independent of the expression of functional AR. Taken together, our data suggest that HNE potentiates the antitumoral effect of the HDACI panobinostat in prostate cancer cells.

Rb-dependent cellular senescence, multinucleation and susceptibility to oncogenic transformation through PKC scaffolding by SSeCKS/AKAP12

A subset of AKAPs (A Kinase Anchoring Proteins) regulate signaling and cytoskeletal pathways through the spaciotemporal scaffolding of multiple protein kinases (PK) such as PKC and PKA, and associations with the plasma membrane and the actin-based cytoskeleton. SSeCKS/Gravin/Akap12 expression is severely downregulated in many advanced cancers and exhibits tumor- and metastasis-suppressing activity. akap12-null (KO) mice develop prostatic hyperplasia with focal dysplasia, but the precise mechanism how Akap12 prevents oncogenic progression remains unclear. Here, we show that KO mouse embryonic fibroblasts (MEF) exhibit premature senescence marked by polyploidy and multinucleation, and by increased susceptibility to oncogenic transformation. Although p53 and Rb pathways are activated in the absence of Akap12, senescence is dependent on Rb. Senescence is driven by the activation of PKCα, which induces p16(Ink4a)/Rb through a MEK-dependent downregulation of Id1, and PKCδ, which downregulates Lats1/Warts, a mitotic exit network kinase required for cytokinesis. Our data strongly suggest that Akap12 controls Rb-mediated cell aging and oncogenic progression by directly scaffolding and attenuating PKCα/δ.

ABCG2-mediated DyeCycle Violet efflux defined side population in benign and malignant prostate

The efflux of Hoechst 33342 by ATP-binding cassette protein G2 (ABCG2) membrane pump allows reproducible identification of a subpopulation of cells by flow cytometric analysis termed the "side population" (SP). The SP identified by constitutive Hoechst efflux contains the stem/progenitor cell population from bone marrow and many solid organs, including prostate. DyeCycle Violet (DCV) is a cell membrane permeable, fluorescent vital dye that intercalates into DNA and is a substrate for ABCG2-mediated efflux. Therefore, DCV was evaluated in this study as a tool for identification of the SP from prostate cancer cell lines and from freshly harvested human prostate tissue. SPs that demonstrated ABCG2-mediated efflux of DCV were identified in the human prostate cancer cell lines CWR-R1, DU-145 and RWPE-1, but not in the BPH-1, LAPC-4 or PC-3 cell lines. Additionally, a SP was identified in enzymatically disaggregated prostate tumors from Transgenic Adenocarcinoma of Mouse Prostate (TRAMP), human benign prostate tissue and human prostate cancer tissue. The causal role of ABCG2-mediated efflux of DCV in the identification of the SP was confirmed by loss of the SP by incubation with the specific inhibitor of ABCG2, Fumitremorgin C. Expression of ABCG2 in the SP cells was confirmed by qRT-PCR and immunofluorescence analysis. Consequently, DCV represents an important new tool for isolation of viable candidate stem cells/cancer stem cells as a SP from cultured prostate cell lines, and prostate tissue specimens, without the requirement for instrumentation with ultra-violet excitation capability and minimizing the risk of damage to DNA in the sorted population.

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.

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.

Vitamin C Is an Essential Antioxidant That Enhances Survival of Oxidatively Stressed Human Vascular Endothelial Cells in the Presence of a Vast Molar Excess of Glutathione

Cellular glutathione levels may exceed vitamin C levels by 10-fold, generating the question about the real antioxidant role that low intracellular concentrations of vitamin C can play in the presence of a vast molar excess of glutathione. We characterized the metabolism of vitamin C and its relationship with glutathione in primary cultures of human endothelial cells oxidatively challenged by treatment with hydrogen peroxide or with activated cells undergoing the respiratory burst, and analyzed the manner in which vitamin C interacts with glutathione to increase the antioxidant capacity of cells. Our data indicate that: (i) endothelial cells express transporters for reduced and oxidized vitamin C and accumulate ascorbic acid with participation of glutathione-dependent dehydroascorbic acid reductases, (ii) although increased intracellular levels of vitamin C or glutathione caused augmented resistance to oxidative stress, 10-times more glutathione than vitamin C was required, (iii) full antioxidant protection required the simultaneous presence of intracellular and extracellular vitamin C at concentrations normally found in vivo, and (iv) intracellular vitamin C cooperated in enhancing glutathione recovery after oxidative challenge thus providing cells with enhanced survival potential, while extracellular vitamin C was recycled through a mechanism involving the simultaneous neutralization of oxidant species. Therefore, in endothelial cells under oxidative challenge, vitamin C functions as an essential cellular antioxidant even in the presence of a vast molar excess of glutathione.

Mechanistic Insights and Functional Determinants of the Transport Cycle of the Ascorbic Acid Transporter SVCT2

We characterized the human Na(+)-ascorbic acid transporter SVCT2 and developed a basic model for the transport cycle that challenges the current view that it functions as a Na(+)-dependent transporter. The properties of SVCT2 are modulated by Ca(2+)/Mg(2+) and a reciprocal functional interaction between Na(+) and ascorbic acid that defines the substrate binding order and the transport stoichiometry. Na(+) increased the ascorbic acid transport rate in a cooperative manner, decreasing the transport K(m) without affecting the V(max), thus converting a low affinity form of the transporter into a high affinity transporter. Inversely, ascorbic acid affected in a bimodal and concentration-dependent manner the Na(+) cooperativity, with absence of cooperativity at low and high ascorbic acid concentrations. Our data are consistent with a transport cycle characterized by a Na(+):ascorbic acid stoichiometry of 2:1 and a substrate binding order of the type Na(+):ascorbic acid:Na(+). However, SVCT2 is not electrogenic. SVCT2 showed an absolute requirement for Ca(2+)/Mg(2+) for function, with both cations switching the transporter from an inactive into an active conformation by increasing the transport V(max) without affecting the transport K(m) or the Na(+) cooperativity. Our data indicate that SVCT2 may switch between a number of states with characteristic properties, including an inactive conformation in the absence of Ca(2+)/Mg(2+). At least three active states can be envisioned, including a low affinity conformation at Na(+) concentrations below 20 mM and two high affinity conformations at elevated Na(+) concentrations whose Na(+) cooperativity is modulated by ascorbic acid. Thus, SVCT2 is a Ca(2+)/Mg(2+)-dependent transporter.

Aluminum fluoride affects the structure and functions of cell membranes

No useful biological function for aluminum has been found. To the contrary, it might play an important role in several pathologies, which could be related to its interactions with cell membranes. On the other hand, fluoride is a normal component of body fluids, soft tissues, bones and teeth. Its sodium salt is frequently added to drinking water to prevent dental caries. However, large doses cause severe pathological alterations. In view of the toxicity of Al(3+) and F(-) ions, it was thought of interest to explore the damaging effects that AlF(3) might induce in cell membranes. With this aim, it was incubated with human erythrocytes, which were examined by phase contrast and scanning electron microscopy, and molecular models of biomembranes. The latter consisted of large unilamellar vesicles (LUV) of dimyristoylphosphatidylcholine (DMPC) and bilayers of DMPC and dimyristoylphosphatidylethanolamine (DMPE) which were studied by fluorescence spectroscopy and X-ray diffraction, respectively. In order to understand the effects of AlF(3) on ion transport (principally sodium and chloride) we used the isolated toad skin to which electrophysiological measurements were applied. It was found that AlF(3) altered the shape of erythrocytes inducing the formation of echinocytes. This effect was explained by X-ray diffraction which revealed that AlF(3) perturbed the structure of DMPC, class of lipids located in the outer monolayer of the erythrocyte membrane. This result was confirmed by fluorescence spectroscopy on DMPC LUV. The biphasic (stimulatory followed by inhibitory) effects on the isolated skin suggested changes in apical Cl(-) secretion and moderate ATPase inactivation.

Toxic effects of the fungicide benomyl on cell membranes

This paper examines the toxicity of the fungicide benomyl towards cell membranes. Approaches to this aim were the study of its acute effects on the stimulatory response of a frog neuroepithelial synapse and on membrane models. The latter consisted of large unilamellar vesicles of dimyristoylphosphatidylcholine (DMPC) and phospholipid multilayers built-up of DMPC and dimyristoylphosphatidylethanolamine (DMPE). Results showed that benomyl at concentrations as low as 10 microM decreased the stimulatory response of the potential difference (PD) and the short-circuit current (SCC) of the frog sympathetic junction. It is concluded that benomyl caused a dose-dependent reduction in the response of a sympathetic junction of the frog to stimulation leading to Cl(-) channel perturbation. This finding might be explained from those obtained from fluorescence spectroscopy and X-ray diffraction studies on membrane models. In fact, similar (0.01-1.0 mM) concentrations induced structural perturbations in DMPC large unilamellar vesicles and multilayers, respectively. Although it is still premature to define the precise molecular mechanism of benomyl toxicity, the experimental results confirm the important role played by the phospholipid bilayers in the interaction of the pesticide with cell membranes.

Physical state of bulk and protein-associated lipid in nicotinic acetylcholine receptor-rich membrane studied by laurdan generalized polarization and fluorescence energy transfer

The spectral properties of the fluorescent probe laurdan (6-dodecanoyl-2-dimethylaminonaphthalene) were exploited to learn about the physical state of the lipids in the nicotinic acetylcholine receptor (AChR)-rich membrane and compare them with those in reconstituted liposomes prepared from lipids extracted from the native membrane and those formed with synthetic phosphatidylcholines. In all cases redshifts of 50 to 60 nm were observed as a function of temperature in the spectral emission maximum of laurdan embedded in these membranes. The so-called generalized polarization of laurdan exhibited high values (0.6 at 5 degrees C) in AChR-rich membranes, diminishing by approximately 85% as temperature increased, but no phase transitions with a clear Tm were observed. A still unexploited property of laurdan, namely its ability to act as a fluorescence energy transfer acceptor from tryptophan emission, has been used to measure properties of the protein-vicinal lipid. Energy transfer from the protein in the AChR-rich membrane to laurdan molecules could be observed upon excitation at 290 nm. The efficiency of this process was approximately 55% for 1 microM laurdan. A minimum donor-acceptor distance r of 14 +/- 1 A could be calculated considering a distance 0 < H < 10 A for the separation of the planes containing donor and acceptor molecules, respectively. This value of r corresponds closely to the diameter of the first-shell protein-associated lipid. A value of approximately 1 was calculated for Kr, the apparent dissociation constant of laurdan, indicating no preferential affinity for the protein-associated probe, i.e., random distribution in the membrane. From the spectral characteristics of laurdan in the native AChR-rich membrane, differences in the structural and dynamic properties of water penetration in the protein-vicinal and bulk bilayer lipid regions can be deduced. We conclude that 1) the physical state of the bulk lipid in the native AChR-rich membrane is similar to that of the total lipids reconstituted in liposomes, exhibiting a decreasing polarity and an increased solvent dipolar relaxation at the hydrophilic/hydrophobic interface upon increasing the temperature; 2) the wavelength dependence of laurdan generalized polarization spectra indicates the presence of a single, ordered (from the point of view of molecular axis rotation)-liquid (from the point of view of lateral diffusion) lipid phase in the native AChR membrane; 3) laurdan molecules within energy transfer distance of the protein sense protein-associated lipid, which differs structurally and dynamically from the bulk bilayer lipid in terms of polarity and molecular motion and is associated with a lower degree of water penetration.

Conditions for growing Mycoplasma canadense and Mycoplasma verecundum in a serum-free medium

Mycoplasma canadense and Mycoplasma verecundum were cultured in a serum-free medium containing bovine serum albumin, cholesterol, oleic acid, and palmitic acid in order to avoid the addition of horse serum. Growth was detected by measurement of A640 and by colony formation. The level of growth attained in this medium was less than that obtained in the horse serum-supplemented media, but colonies retained their distinctive morphology.