Abstract 2661: AUTO6NG overcomes immune suppressive mechanisms in the TME and demonstrate preclinical anti-tumor activity in GD2-expressing solid tumors

Immune-checkpoint blockade therapies has had impressive results in the clinic and are approved in multiple cancer indications. However, meaningful responses remain elusive in several solid tumor types and durable responses in some of these indications, or subtypes, are rarely observed. It has been postulated that this is in part due to elaborate poorly understood immunosuppressive mechanisms that the therapeutic approach must overcome to elicit the desired durable responses. Chimeric Antigen Receptor T (CAR-T) cell therapies had been therapeutically highly successful in haematological malignancies but such successes have not been replicated yet in solid tumors, primarily due to immune suppressive mechanisms in the tumor microenvironment (TME) of these settings. To address these issues in developing our CAR-T therapeutics, we deployed tissue cytometry to conduct a multiplex analysis of 30 markers on the same tissue sections from each patient from a set of patients from various solid tumor indications expressing the antigen GD2 (e.g. SCLC, Melanoma, Neuroblastoma), a disialoganglioside to which we have developed a selective CAR. The panel aimed to characterize and phenotype key players within the TME (i.e. tumour cells, T cells, DCs, macrophages, MDSCs, CAFs, as well as endothelial cells). We then deployed machine learning analytics to assist in inferring about potential interactions the different cell types have in the 3D context of the tumor tissue which allowed the identification of therapeutically relevant elements in the TMEs of these indications. Next, we generated CAR-T cells from healthy donors targeting GD2, an antigen we validated its expression in multiple solid tumor types. A first generation GD2 CAR is currently being developed in the clinic for the treatment of Neuroblastoma. We proceeded to incorporate a CCR module (IL7R chimeric protein designed to improve cell persistence), a dnTGFβ (dominant negative TGF-βRII protein designed to block inhibitor signals from TGFβ), and other function enhancing modules into the GD2 CAR. The multi module CAR-T cells showed potent in vitro activity against human patient derived cancer cell lines as measured by both tumor lysis and cytokine secretion. These CAR-T cells also demonstrated enhanced tumor infiltration and anti-tumor activity in vivo in xenografts mouse models. Our findings suggest that GD2 targeted CAR-T cell therapy is a viable novel approach for the treatment of multiple solid tumors indications.

Citation Format: Margarida Neves, Lukas Stanczuk, Alireza Alavi, Meggan Czapiga, Rebecca Moore, Frederick Vargas, Muhammad A. Al-Hajj. AUTO6NG overcomes immune suppressive mechanisms in the TME and demonstrate preclinical anti-tumor activity in GD2-expressing solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2661.

Abstract 1451: Analysis of expression MHC class I chain-related gene A and B (MICA/B) in normal and tumor tissue

MHC class I chain-related gene A and B (MICA and MICB) are highly polymorphic proteins that are induced upon stress, damage or transformation of cells which act as a “kill me” signal through the NKG2D receptor expressed on Natural Killer, CD8+ and γδ T cells.

Experimentally, the MIC/NKG2D axis has been shown to be important for the recognition of tumour cells by cytotoxic cells of the immune system and many tumours have evolved strategies to evade the detection by NKG2D expressing cells, e.g. by shedding MIC from the cell surface.

Expression of MIC has been reported for most tumour types and in normal gastrointestinal tract epithelium but the published data is often difficult to interpret. Additionally, it is not clear how much of the protein is expressed on the cell surface as MIC cell surface expression is known to be regulated tightly on multiple levels.

A validated MICA/B IHC assay was developed using an in-house tool antibody to profile multiple frozen human normal and tumour tissue microarrays (TMA’s) by both standard and confocal microscopy techniques.

Using a stringently characterised novel antibody that detects MICA as well as MICB this study describes the expression patterns in a wide range of tumours and normal tissues. With this method we generated data with unprecedented resolution, which enabled us to analyse the expression of MICA and MICB not only on the cellular but also on the sub-cellular level.

Citation Format: Hormas Ghadially, Lee Brown, Arthur Lewis, Meggan Czapiga, Viia Valge-Archer, Robert W. Wilkinson. Analysis of expression MHC class I chain-related gene A and B (MICA/B) in normal and tumor tissue. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1451.

Genomic Landscape Survey Identifies SRSF1 as a Key Oncodriver in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive disease with poor survival. A few sequencing studies performed on limited number of samples have revealed potential disease-driving genes in SCLC, however, much still remains unknown, particularly in the Asian patient population. Here we conducted whole exome sequencing (WES) and transcriptomic sequencing of primary tumors from 99 Chinese SCLC patients. Dysregulation of tumor suppressor genes TP53 and RB1 was observed in 82% and 62% of SCLC patients, respectively, and more than half of the SCLC patients (62%) harbored TP53 and RB1 mutation and/or copy number loss. Additionally, Serine/Arginine Splicing Factor 1 (SRSF1) DNA copy number gain and mRNA over-expression was strongly associated with poor survival using both discovery and validation patient cohorts. Functional studies in vitro and in vivo demonstrate that SRSF1 is important for tumorigenicity of SCLC and may play a key role in DNA repair and chemo-sensitivity. These results strongly support SRSF1 as a prognostic biomarker in SCLC and provide a rationale for personalized therapy in SCLC.

SCLC patients are initially highly chemo-sensitive with response rates of greater than 80% in both limited and extensive diseases, but suffer uniform disease recurrence or progression in a very short period of time. In the absence of well-defined genomic biomarkers and insights into the resistance mechanism, many targeted treatments have yielded negative results in the last decade Using integrated next generation sequencing (NGS) technology in combination with a high quality surgical sample set with comprehensive clinical annotation, our study not only identified novel recurrent genetic alterations in genes such as CDH10 and DNA repair pathways which may influence outcomes in SCLC patients, but also discovered the expression of SRSF1, an RNA-splicing factor which can both regulate key oncogenic and survival pathways such as BCL2, and play a critical role in patient survival.

Abstract 2032: Genomic landscape survey identifies SRSF1 as a key oncodriver in small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive disease with poor survival. Large-scale sequencing studies have revealed potential disease-driving genes in various cancers, although in SCLC, much still remains unknown, particularly in the Asian patient population. Here we conducted whole exome sequencing (WES) and transcriptomic sequencing of primary tumors from 99 Chinese SCLC patients. It revealed 34,099 somatic nonsilent single nucleotide variants (SNVs) or insertion/deletions (indels), an average of 308 per patient and nonsilent/silent ratio of 1.66. Genes harboring the most recurrent SNVs or indels were TP53 (81%), CSMD3 (43%), RB1 (46%), LRP1B (38%) and OBSCN (41%). Somatic copy number variants (CNVs) were also identified including MYC (8%), KIT (17%), and SOX4 (19%), with SOX2 (67%) and multiple other genes located across a segment on chromosome 3q27.1. Genes with CN losses include RB1 (34%), RASSF1 (57%), FHIT (54%), KIF2A (16%), and CNTN3 (53%), as well as a long segment along chromosome 3p22.1. Recurrence rates of these genes affected by SNVs and CNVs were comparable to those reported previously. In addition, we found recurrent gains of Serine/Arginine Splicing Factor 1 (SRSF1) in 51% (49/96) patients as well as concordant over-expression of mRNA for those patients with gains (p = 0.005; two-tailed two-sided Welch's t-test;). Among these 96 Chinese patients, 28% had both CN gain and mRNA over-expression of SRSF1; SRSF1 CN status was evaluated by FISH assay (N = 34), the positive and negative predictive values were 57% and 69% respectively. Patients with both RNASeq and survival data were interrogated (N = 49), SRSF1 was the only gene correlating between both CN gain and mRNA over-expression as well as between over-expression and survival using a Cox proportion hazard (PH) regression model adjusting for age, gender, tumor stage, and chemotherapy status (p = 0.034; HR = 3.0). Patients with SRSF1 mRNA over-expression or CN gain demonstrated significantly worse survival. The discovery (log-rank test p = 0.062), validation (log-rank test p = 0.03), and combined patient cohort (Cox PH p = 0.021; HR = 2.1; log-rank test p = 0.005).

On target in vivo studies demonstrated that SRSF1 is essential for tumorigenecity of SCLC. siRNAs (control/SRSF1)were transfected to cell lines with DNA amplification/mRNA overexpression (DMS114 and SHP-77SRSF1). Equal numbers of viable transfected cells were injected in immunocompromised mice and tumor growth was monitored for up to three weeks. SRSF1 knockdown completely suppressed the tumor growth These data strongly support SRSF1 as a therapeutic target in SCLC and provide a rationale for personalized therapy in SCLC.

Citation Format: Zheng Liu, Jiaqi Huang, Brandon W. Higgs, Haihong Zhong, Dong Shen, Zhan Xiao, Xin Yao, Philip Brohawn, Xiaoxiao Ge, Zhibing Hu, Yue Jiang, Chris Morehouse, Wei Zhu, Yinong Sebastian, Meggan Czapiga, Vaheh Oganesyan, Haihua. Fu, Xinying Su, Yi Gu, Baohui Han, Ronald Herbst, Liayang Jiang, Hongbing Shen, Yihong Yao. Genomic landscape survey identifies SRSF1 as a key oncodriver in small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2032. doi:10.1158/1538-7445.AM2015-2032

Abstract 4954: Serine/arginine splicing factor 1 (SRSF1) mediates DNA repair and chemo-sensitivity and drives growth in small cell lung cancer

Small cell lung cancer (SCLC) is the most aggressive subtype of lung cancer. Despite a high response rate to chemotherapy, more than 95% of patients eventually die from SCLC. We have identified that Serine/Arginine Splicing Factor 1 (SRSF1) DNA copy number gain and mRNA over-expression in tumor is strongly associated with poor survival based on whole exome sequencing (WES) and transcriptomic sequencing of primary tumors from 99 Chinese SCLC patients. Here, SRSF1 is evaluated as a tumor driver in SCLC. Treatment of SCLC cell lines in vitro with a low dose of cisplatin or topotecan (two of the most common standard of care in SCLC) only induced a modest decrease of cell growth. However, knockdown of SRSF1 with siRNA along with a sub-lethal dose of cisplatin or topotecan enhanced the overall growth inhibition effect compared to the chemotherapy alone. SRSF1 siRNA alone induced modest but significant caspase-3 activation, similar to cisplatin or topotecan treatment alone. The combination of SRSF1 siRNA with chemotherapy treatments produced a significantly higher caspase induction. DNA-damage induction as a potential mechanism of SRSF1 knockdown was assessed. Phosphorylation of H2AX and Chk2, established markers of DNA-strand breaks and DNA-repair response, was consistently induced upon SRSF1 abrogation in cells, and further increased the phosphorylation of these proteins when combined with cisplatin or topotecan treatment. The knockdown of SRSF1 in SCLC cells also resulted in significant growth inhibition when cells were grown as 3D spheroids. Cells transfected with non-targeting siRNA produced large and well-organized spheroids; in contrast, cells transfected with SRSF1 siRNA did not form well-organized structures but mainly existed as single cells with poor viability. Results were confirmed by colony formation assays and could be rescued with a siRNA-resistant SRSF1 expression construct. Finally, we investigated the impact of SRSF1 loss on kinase signaling pathways in SCLC cells through phospho-kinase array profiling. Strong phospho-AKT and ERK signals were observed in control siRNA-transfected cells, and were abrogated by SRSF1 siRNA. Western blot confirmed this in several SCLC cell lines. These targeting studies demonstrate that SRSF1 plays a key role in DNA repair, chemo-sensitivity and cell proliferation. Together, these data reveal SRSF1 as a therapeutic target in SCLC and provide a rationale for personalized therapy in SCLC.

Citation Format: Sarah J. Conley, Xin Yao, Jiaqi Huang, Brandon Higgs, Zhibin Hu, Zhan Xiao, Haihong Zhong, Zheng Liu, Philip Brohawn, Xiaoxiao Ge, Meggan Czapiga, Vaheh Oganesyan, Haihua Fu, David Tice, Ronald Herbst, Xinying Su, Yi Gu, Jianren Gu, Baohui Han, Laura Richman, Bahija Jallal, Liyan Jiang, Hongbing Shen, Yihong Yao. Serine/arginine splicing factor 1 (SRSF1) mediates DNA repair and chemo-sensitivity and drives growth in small cell lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4954. doi:10.1158/1538-7445.AM2015-4954

S100A9 induced inflammatory responses are mediated by distinct damage associated molecular patterns (DAMP) receptors in vitro and in vivo

Release of endogenous damage associated molecular patterns (DAMPs), including members of the S100 family, are associated with infection, cellular stress, tissue damage and cancer. The extracellular functions of this family of calcium binding proteins, particularly S100A8, S100A9 and S100A12, are being delineated. They appear to mediate their functions via receptor for advanced glycation endproducts (RAGE) or TLR4, but there remains considerable uncertainty over the relative physiological roles of these DAMPs and their pattern recognition receptors. In this study, we surveyed the capacity of S100 proteins to induce proinflammatory cytokines and cell migration, and the contribution RAGE and TLR4 to mediate these responses in vitro. Using adenoviral delivery of murine S100A9, we also examined the potential for S100A9 homodimers to trigger lung inflammation in vivo. S100A8, S100A9 and S100A12, but not the S100A8/A9 heterodimer, induced modest levels of TLR4-mediated cytokine production from human PBMC. In contrast, for most S100s including S100A9, RAGE blockade inhibited S100-mediated cell migration of THP1 cells and major leukocyte populations, whereas TLR4-blockade had no effect. Intranasal administration of murine S100A9 adenovirus induced a specific, time-dependent predominately macrophage infiltration that coincided with elevated S100A9 levels and proinflammatory cytokines in the BAL fluid. Inflammatory cytokines were markedly ablated in the TLR4-defective mice, but unexpectedly the loss of TLR4 signaling or RAGE-deficiency did not appreciably impact the S100A9-mediated lung pathology or the inflammatory cell infiltrate in the alveolar space. These data demonstrate that physiological levels of S100A9 homodimers can trigger an inflammatory response in vivo, and despite the capacity of RAGE and TLR4 blockade to inhibit responses in vitro, the response is predominately independent of both these receptors.

Abstract 2377: Low frequency KRAS mutations in colorectal cancer patients and the presence of multiple mutations in oncogenic drivers in non-small cell lung cancer patients

Intratumor heterogeneity can confound the results of mutation analyses in oncodriver genes using traditional methods thereby challenging the application of targeted cancer therapy strategies for patients. Ultradeep sequencing can detect low frequency and expanded clonal mutations in primary tumors to better inform treatment decisions. KRAS coding exons in 61 treatment-naïve colorectal cancer (CRC) tumors and KRAS, EGFR, ALK, and MET in lung tumors from three Chinese non-small cell lung cancer (NSCLC) patients were sequenced using ultradeep sequencing methods. Forty-one percent of CRC patients (25/61) harbored mutations in the KRAS active domain, eight of which (13%) were not detected by Sanger sequencing. Three (of eight) had frequencies less than 10% and one patient harbored more than one mutation. Low frequency KRAS active (G12R) and EGFR kinase domain mutations (G719A) were identified in one NSCLC patient. A second NSCLC patient showed an EML4-ALK fusion with ALK, EGFR, and MET mutations. A third NSCLC patient harbored multiple low frequency mutations in KRAS, EGFR, and MET as well as ALK gene copy number increases. Within the same patient, multiple low frequency mutations occurred within a gene. A complex pattern of intrinsic low frequency driver mutations in well-known tumor oncogenes may exist prior to treatment, resulting in resistance to targeted therapies. Current targeted cancer therapies usually lack durability and demonstrate limited overall efficacy in patients. The types of low frequency concurrent mutations in candidate oncogenes presented here suggest necessary modifications both to methods for detection of these variants and to general treatment strategies. To date, Sanger sequencing has been effectively used for detection of treatment-relevant somatic mutations. However, in a heterogeneous mixture of cancerous and normal tissue, Sanger sequencing will likely fail to detect low frequency mutations. More sensitive and cost-effective sequencing methods are required to systematically assess the mutation status within cancer pathway genes or at the whole genome level. Furthermore, because patients often develop resistance to targeted therapy over time that is due to the preexistence of low frequency mutations in oncogenes, treatment strategies based on combination therapy might prove to be the most optimal treatment approach for cancer patients. Ultradeep sequencing can characterize intratumor heterogeneity and identify such mutations to ultimately affect treatment decisions.

Citation Format: Christopher Morehouse, Liyan Jiang, Jiagi Huang, Wei Zhu, Susana Korolevich, Xiaoxiao Ge, Kim Lehmann, Zheng Lui, Christine Kiefer, Meggan Czapiga, Xinying Su, Philip Brohawn, Yi Gu, Brandon Higgs, Yihong Yao. Low frequency KRAS mutations in colorectal cancer patients and the presence of multiple mutations in oncogenic drivers in non-small cell lung cancer patients. [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 2377. doi:10.1158/1538-7445.AM2014-2377

Inhibition of myogenic microRNAs 1, 133, and 206 by inflammatory cytokines links inflammation and muscle degeneration in adult inflammatory myopathies

OBJECTIVE

The molecular basis of inflammatory myopathies such as dermatomyositis (DM), polymyositis, and inclusion body myositis, which share the characteristics of chronic muscle inflammation and skeletal muscle wasting, are poorly understood. As such, effective targeted treatments for these diseases are lacking, resulting in critical unmet medical needs for these devastating diseases. The purpose of this study was to identify possible new targets for drug development by exploring the mechanism by which inflammation may play a role in the pathology of the inflammatory myopathies.

METHODS

We compared expression levels of inflammatory cytokines and microRNAs (miRNAs) between muscle biopsy samples from patients with inflammatory myopathies and those from donors without myositis. In vitro human and mouse model systems were then used to characterize the role of these cytokines and microRNAs on myoblast-to-myocyte differentiation.

RESULTS

We observed increased expression of inflammatory cytokines, including tumor necrosis factor α (TNFα), interferon-α (IFNα), IFNβ, and interleukin-1β, in different subtypes of inflammatory myopathies. We observed decreased expression of microRNA-1 (miR-1), miR-133a, and miR-133b in all of the inflammatory myopathy subtypes we evaluated, as well as decreased expression of miR-206 in DM; these miRNAs are essential for adult skeletal muscle differentiation and maintenance. TNFα was significantly inversely correlated with decreased myogenic miRNA expression in the inflammatory myopathy subtypes. In mechanistic studies, TNFα inhibited the expression of myogenic miRNAs and suppressed the differentiation of C2C12 myoblasts to myocytes/myotubes in an NF-κB-dependent manner. This block in differentiation by TNFα was relieved by overexpression of miR-1, miR-206, or miR-133a/b.

CONCLUSION

Taken together, these results provide a new mechanistic link between the action of proinflammatory cytokines and the degenerative pathology of inflammatory myopathies, and suggest therapeutic approaches for these diseases.

Low frequency KRAS mutations in colorectal cancer patients and the presence of multiple mutations in oncogenic drivers in non-small cell lung cancer patients

Intratumor heterogeneity can confound the results of mutation analyses in oncodriver genes using traditional methods thereby challenging the application of targeted cancer therapy strategies for patients Ultradeep sequencing can detect low frequency and expanded clonal mutations in primary tumors to better inform treatment decisions. KRAS coding exons in 61 treatment-naive colorectal cancer (CRC) tumors and KRAS, EGFR, ALK, and MET in lung tumors from three Chinese non-small cell lung cancer (NSCLC) patients were sequenced using ultradeep sequencing methods. Forty-one percent of CRC patients (25/61) harbored mutations in the KRAS active domain, eight of which (13%) were not detected by Sanger sequencing. Three (of eight) had frequencies less than 10% and one patient harbored more than one mutation. Low frequency KRAS active (G12R) and EGFR kinase domain mutations (G719A) were identified in one NSCLC patient. A second NSCLC patient showed an EML4-ALK fusion with ALK, EGFR, and MET mutations. A third NSCLC patient harbored multiple low frequency mutations in KRAS, EGFR, and MET as well as ALK gene copy number increases. Within the same patient, multiple low frequency mutations occurred within a gene. A complex pattern of intrinsic low frequency driver mutations in well-known tumor oncogenes may exist prior to treatment, resulting in resistance to targeted therapies. Ultradeep sequencing can characterize intratumor heterogeneity and identify such mutations to ultimately affect treatment decisions.

Abstract 4587: In vitro and In vivo characterization of circulating tumor cells from breast cancer patients

Circulating tumor cells (CTCs) are an independent prognostic marker associated with poor clinical outcome in patients with metastatic diseases. However, CTC biology, especially the tumorigenic and metastatic activity of CTCs, is not yet well understood. In this study, we hypothesized that CTCs contain a population of cancer stem cells (CSCs) that are the seed cells responsible for metastases. To test this hypothesis, we sought to assess subpopulations of CTCs in breast cancer patients and to characterize CTCs for CSC properties and tumorigenic potential. For assessment of CTC subsets, blood samples from breast cancer patients were enriched for CTCs by magnetic separation. The enriched CTC samples were immunostained for various cell surface markers and then analyzed by FACS. The phenotypes of CTCs were further confirmed by imaging analysis. To evaluate tumorigenicity of CTCs, CTC samples from patients were cultured in vitro and then implanted into immunodeficient mice by orthotopic injection. Different phenotypes of CTCs were found in breast cancer patients, including EpCAM+CD44−CD24−/dimCD45−, EpCAM+CD44+CD24−/dimCD45−, EpCAM+CD44+CD24+CD45−, and EpCAM+CD44+CD24+CD45dim. Of these phenotypes, EpCAM+CD44+CD24−/dim cells have been reported as CSCs in breast cancer. This subset of CSC-like CTCs constituted 4.6% to 71% of the total CTC population. In vitro culture of CTCs resulted in the generation of mammospheres, as is typical of CSCs. During in vitro culture, some of CTCs showed staining positive for Ki-67, indicating that these cells were proliferating. To assess tumorigenic potential of CTCs, cultured CTCs were injected into the mouse mammary fat pads of immunodeficient mice. Human tumors were developed in these mice. Further analysis of the CTC-derived tumor xenografts demonstrated a heterogenous phenotype where EpCAM+CD44+CD24dim/− CSCs accounted for less than 3% of the total tumor cells. Only this subset of cells isolated from CTC-derived xenograft tumors could form secondary tumors after being reimplanted into mice. Our results support the hypothesis that CTCs contain a CSC-like population that may initiate new tumors. As a result, CTCs may be a potential therapeutic target for the prevention of metastasis in addition to serving as a readily accessible source for biomarker evaluation of new therapies in cancer patients.

Citation Format: Sanjoo Jalla, Xiaoru Chen, Patricia Burke, Xiaoqing Shi, Meggan Czapiga, Vivekananda Datta, Philip Brohawn, Jiaqi Huang, Charles Brown, Elaine Hurt, Laura Richman, Robert Hollingsworth, Theresa LaVallee, Haifeng Bao. In vitro and In vivo characterization of circulating tumor cells from breast cancer patients. [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 4587. doi:10.1158/1538-7445.AM2013-4587

MEDI3617, a human anti-angiopoietin 2 monoclonal antibody, inhibits angiogenesis and tumor growth in human tumor xenograft models

Angiopoietin 2 (Ang2) is an important regulator of angiogenesis, blood vessel maturation and integrity of the vascular endothelium. The correlation between the dynamic expression of Ang2 in tumors with regions of high angiogenic activity and a poor prognosis in many tumor types makes Ang2 an ideal drug target. We have generated MEDI3617, a human anti-Ang2 monoclonal antibody that neutralizes Ang2 by preventing its binding to the Tie2 receptor in vitro, and inhibits angiogenesis and tumor growth in vivo. Treatment of mice with MEDI3617 resulted in inhibition of angiogenesis in several mouse models including: FGF2-induced angiogenesis in a basement extract plug model, tumor and retinal angiogenesis. In xenograft tumor models, treatment with MEDI3617 resulted in a reduction in tumor angiogenesis and an increase in tumor hypoxia. The administration of MEDI3617 as a single agent to mice bearing human tumor xenografts resulted in tumor growth inhibition against a broad spectrum of tumor types. Combining MEDI3617 with chemotherapy or bevacizumab resulted in a delay in tumor growth and no body weight loss was observed in the combination groups. These results, combined with pharmacodynamic studies, demonstrate that treatment of tumor-bearing mice with MEDI3617 significantly inhibited tumor growth as a single agent by blocking tumor angiogenesis. Together, these data show that MEDI3617 is a robust antiangiogenic agent and support the clinical evaluation and biomarker development of MEDI3617 in cancer patients.

Abstract 4792: Biomarker discovery: Correlation of peripheral and tumoral markers in matched tumor and plasma samples

The heterogeneous nature of cancer necessitates the identification of markers to enable selection of appropriate patients for treatment and maximal clinical benefit. Archival tumor specimens are often analyzed for biomarkers, but may not reflect a patient's current state of disease. Predictive biomarkers from matrices amenable to longitudinal analyses and available through minimally invasive approaches could greatly improve patient outcomes by ensuring that the right patient receives the right drug. Peripheral markers are accessible and attractive, however, their relationship to tumoral markers, tumor biology as well as to primary or secondary clinical outcomes are not well understood. We examined the correlations among potential predictive biomarkers in these compartments by performing proteomic profiling of ∼300 analytes in 100 matched plasma and tumor tissue samples derived from patients with colorectal cancer (CRC), gastric, ovarian, and non-small cell lung cancer (NSCLC) of squamous cell carcinoma (SCC) or adenocarcinoma (ADC) histology. Using Luminex based assays, we identified markers which clearly distinguish each tumor type from another and may be useful for patient enrichment. VEGF has been implicated in processes essential to tumor growth and disease progression such as angiogenesis, vasculogenesis and hypoxia. Therefore, we examined the relationship between VEGF levels in plasma samples and tumor tissue within individual patients and explored the correlations among VEGF levels with those of other soluble proteins in the same matrices as well as with a marker of blood vessel formation in the tumors, microvessel density (MVD). We found the highest level of VEGF in the plasma of CRC patients but NSCLC patients displayed the highest level of VEGF in tumors. A poor correlation between tumoral or plasma VEGF levels was observed in all of the samples except for those from NSCLC SCC patients. MVD analysis of the tumors revealed that gastric and NSCLC ADC patients have a higher density of capillary vessels than other cancers. Surprisingly, no intra-patient correlation was detected between tumoral levels or plasma levels of VEGF and MVD. However, modest correlations between the MVD level in tumor tissues and select analytes in plasma have been observed for some tumor types. Further evaluation of these potential protein signatures in additional matched patient samples and animal disease models is warranted to generate clinically testable hypotheses for patient enrichment. The validity of these protein signatures as predictive markers for response to targeted therapies must be tested clinically. These novel and unexpected findings suggest that some peripheral markers may accurately represent the biology of the tumor and that matched sample analysis can provide an approach for biomarker discovery and hypothesis generation.

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 4792. doi:1538-7445.AM2012-4792

Innate immunity against Granulibacter bethesdensis, an emerging gram-negative bacterial pathogen

Acetic acid bacteria were previously considered nonpathogenic in humans. However, over the past decade, five genera of Acetobacteraceae have been isolated from patients with inborn or iatrogenic immunodeficiencies. Here, we describe the first studies of the interactions of the human innate immune system with a member of this bacterial family, Granulibacter bethesdensis, an emerging pathogen in patients with chronic granulomatous disease (CGD). Efficient phagocytosis of G. bethesdensis by normal and CGD polymorphonuclear leukocytes (CGD PMN) required heat-labile serum components (e.g., C3), and binding of C3 and C9 to G. bethesdensis was detected by immunoblotting. However, this organism survived in human serum concentrations of ≥90%, indicating a high degree of serum resistance. Consistent with the clinical host tropism of G. bethesdensis, CGD PMN were unable to kill this organism, while normal PMN, in the presence of serum, reduced the number of CFU by about 50% after a 24-h coculture. This finding, together with the observations that G. bethesdensis was sensitive to H(2)O(2) but resistant to LL-37, a human cationic antimicrobial peptide, suggests an inherent resistance to O(2)-independent killing. Interestingly, 10 to 100 times greater numbers of G. bethesdensis were required to achieve the same level of reactive oxygen species (ROS) production induced by Escherichia coli in normal PMN. In addition to the relative inability of the organism to elicit production of PMN ROS, G. bethesdensis inhibited both constitutive and FAS-induced PMN apoptosis. These properties of reduced PMN activation and resistance to nonoxidative killing mechanisms likely play an important role in G. bethesdensis pathogenesis.

Abstract 3736: Application of circulating tumor cells and circulating cell-free DNA to assess the pharmacodynamic response to chemotherapy in xenograft models

Circulating tumor cells (CTCs) are found in various cancer patients and are a prognostic factor for survival in some tumor indications. Circulating cell-free DNA is elevated in cancer patients and has been shown to decrease in response to treatments that result in clinical benefit in cancer patients. CTCs and circulating DNA have the potential to serve as minimally invasive methods that allow monitoring response of tumor to anticancer treatment. Our objectives were to 1) establish analytical methods for enumeration and characterization of CTCs from human xenografts in mice, and 2) evaluate CTCs and circulating DNA as pharmacodynamic (PD) markers/proof of mechanism biomarkers for anticancer therapy in xenograft models. Methods: the Veridex CellSearch™ method was modified for quantifying CTCs (defined as nucleated cells positive for cytokeratin but negative for mouse CD45) in mouse whole blood. The assay was characterized and validated by spiking humor tumor cells into mouse whole blood. Additional markers of Ki-67 and cleaved caspase 3 were added to the assay for assessment of proliferation and apoptosis of CTCs. Circulating nucleosomal DNA was measured in plasma by anti-histone H3 ELISA assay. Results: CTCs were detectable in blood from mice with tumor xenografts of PC3-M, MDA-MB-468, and H358. The number of CTCs was not correlated with the volume of the primary tumor. To evaluate changes of CTCs and circulating DNA in response to anticancer therapy, mice with tumor xenografts were treated with taxotere (0, 2.5, 7.5 or 15 mg/kg) to assess dose response or following a single dose (15 mg/kg) to assess response kinetics at 1, 3, 5 and 8 days. Treatment of tumor-bearing mice with taxotere increased the total number of CTCs but decreased the percentage of proliferating Ki-67 positive CTCs, which was consistent with decreased levels of Ki-67 positive cells observed in tumor sections. The increase in the number of CTCs was transient, peaking on day 3 and then returning to a low level by day 5 post-treatment. Circulating DNA levels were significantly elevated in tumor-bearing mice as compared with naïve mice and were positively correlated with tumor growth. Taxotere treatment further increased the level of circulating DNA in a dose-dependent manner. The elevation of the level of circulating DNA peaked on day 5 and returned to pre-treatment level on day 8. These results suggest that the release of tumor cells into circulation with decreased proliferative potential combined with increased circulating cell-free DNA may represent markers for the early response to effective cancer treatments. Studies in mice support the use of CTCs, particularly if characterized for proliferative potential, in addition to circulating DNA, as potential early response/proof of mechanism biomarkers for anticancer drug candidates and warrant further evaluation in human clinical studies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3736.

Functionally competent eosinophils differentiated ex vivo in high purity from normal mouse bone marrow

We have devised an ex vivo culture system which generates large numbers of eosinophils at high purity (>90%) from unselected mouse bone marrow progenitors. In response to 4 days of culture with recombinant mouse FLT3-L and recombinant mouse stem cell factor followed by recombinant mouse IL-5 alone thereafter, the resulting bone marrow-derived eosinophils (bmEos) express immunoreactive major basic protein, Siglec F, IL-5R alpha-chain, and transcripts encoding mouse eosinophil peroxidase, CCR3, the IL-3/IL-5/GM-CSF receptor common beta-chain, and the transcription factor GATA-1. BmEos are functionally competent: they undergo chemotaxis toward mouse eotaxin-1 and produce characteristic cytokines, including IFN-gamma, IL-4, MIP-1alpha, and IL-6. The rodent pathogen pneumonia virus of mice replicates in bmEos and elevated levels of IL-6 are detected in supernatants of bmEos cultures in response to active infection. Finally, differentiating bmEos are readily transfected with lentiviral vectors, suggesting a means for rapid production of genetically manipulated cells.

Detection and imaging of non-contractile inclusions and sarcomeric anomalies in skeletal muscle by second harmonic generation combined with two-photon excited fluorescence

The large size of the multinucleated muscle fibers of skeletal muscle makes their examination for structural and pathological defects a challenge. Sections and single fibers are accessible to antibodies and other markers but imaging of such samples does not provide a three-dimensional view of the muscle. Regrettably, bundles of fibers cannot be stained or imaged easily. Two-photon microscopy techniques overcome these obstacles. Second harmonic generation (SHG) by myosin filaments and two-photon excited fluorescence (2PEF) of mitochondrial and lysosomal components provides detailed structural information on unstained tissue. Furthermore, the infrared exciting light can penetrate several layers of muscle fibers and the minimal processing is particularly valuable for fragile biopsies. Here we demonstrate the usefulness of SHG, combined with 2PEF, to reveal enlarged lysosomes and accumulations of non-contractile material in muscles from the mouse model for the lysosomal storage disorder Pompe disease (PD), and in biopsies from adult and infant PD patients. SHG and 2PEF also detect sarcomeric defects that may presage the loss of myofibrils in atrophying muscle and signify loss of elasticity. The combination of SHG and 2PEF should be useful in the analysis and diagnosis of a wide range of skeletal muscle pathologies.

R7-binding protein targets the G protein beta 5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain

Background

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain.

Results

We show that endogenous Gβ5/R7-RGS/R7BP protein complexes are present in native neuron-like PC12 cells and that a fraction is targeted to low-density, detergent-resistant membrane lipid rafts. The buoyant density of endogenous raft-associated Gβ5/R7-RGS protein complexes in PC12 cells was similar to that of lipid rafts containing the palmitoylated marker proteins PSD-95 and LAT, but distinct from that of the membrane microdomain where flotillin was localized. Overexpression of wild-type R7BP, but not its palmitoylation-deficient mutant, greatly enriched the fraction of endogenous Gβ5/R7-RGS protein complexes in the lipid rafts. In HEK-293 cells the palmitoylation status of R7BP also regulated the lipid raft targeting of co-expressed Gβ5/R7-RGS/R7BP proteins. A fraction of endogenous Gβ5/R7-RGS/R7BP complexes was also present in lipid rafts in mouse brain.

Conclusion

A fraction of Gβ5/R7-RGS/R7BP protein complexes is targeted to low-density, detergent-resistant membrane lipid rafts in PC12 cells and brain. In cultured cells, the palmitoylation status of R7BP regulated the lipid raft targeting of endogenous or co-expressed Gβ5/R7-RGS proteins. Taken together with recent evidence that the kinetic effects of the Gβ5 complex on GPCR signaling are greatly enhanced by R7BP palmitoylation through a membrane-anchoring mechanism, our data suggest the targeting of the Gβ5/R7-RGS/R7BP complex to lipid rafts in neurons and brain, where G proteins and their effectors are concentrated, may be central to the G protein regulatory function of the complex.

Eosinophils from lineage-ablated Delta dblGATA bone marrow progenitors: the dblGATA enhancer in the promoter of GATA-1 is not essential for differentiation ex vivo

A critical role for eosinophils in remodeling of allergic airways was observed in vivo upon disruption of the dblGATA enhancer that regulates expression of GATA-1, which resulted in an eosinophil-deficient phenotype in the DeltadblGATA mouse. We demonstrate here that bone marrow progenitors isolated from DeltadblGATA mice can differentiate into mature eosinophils when subjected to cytokine stimulation ex vivo. Cultured DeltadblGATA eosinophils contain cytoplasmic granules with immunoreactive major basic protein and they express surface Siglec F and transcripts encoding major basic protein, eosinophil peroxidase, and GATA-1, -2, and -3 to an extent indistinguishable from cultured wild-type eosinophils. Fibroblast coculture and bone marrow cross-transplant experiments indicate that the in vivo eosinophil deficit is an intrinsic progenitor defect, and remains unaffected by interactions with stromal cells. Interestingly, and in contrast to those from the wild type, a majority of the GATA-1 transcripts from cultured DeltadblGATA progenitors express a variant GATA-1 transcript that includes a first exon (1E(B)), located approximately 3700 bp downstream to the previously described first exon found in hemopoietic cells (1E(A)) and approximately 42 bp upstream to another variant first exon, 1E(C). These data suggest that cultured progenitors are able to circumvent the effects of the DeltadblGATA ablation by using a second, more proximal, promoter and use this mechanism to generate quantities of GATA-1 that will support eosinophil growth and differentiation.

Nuclear localization of the parafibromin tumor suppressor protein implicated in the hyperparathyroidism-jaw tumor syndrome enhances its proapoptotic function

Parafibromin is a tumor suppressor protein encoded by HRPT2, a gene recently implicated in the hereditary hyperparathyroidism-jaw tumor syndrome, parathyroid cancer, and a subset of kindreds with familial isolated hyperparathyroidism. Human parafibromin binds to RNA polymerase II as part of a PAF1 transcriptional regulatory complex. The mechanism by which loss of parafibromin function can lead to neoplastic transformation is poorly understood. Because the subcellular localization of parafibromin is likely to be critical for its function with the nuclear PAF1 complex, we sought to experimentally define the nuclear localization signal (NLS) of parafibromin and examine its potential role in parafibromin function. Using site-directed mutagenesis, we define a dominant bipartite NLS and a secondary NLS, both in the NH(2)-terminal region of parafibromin whose combined mutation nearly abolishes nuclear targeting. The NLS-mutant parafibromin is significantly impaired in its association with endogenous Paf1 and Leo1. We further report that overexpression of wild-type but not NLS-mutant parafibromin induces apoptosis in transfected cells. Inhibition of endogenous parafibromin expression by RNA interference inhibits the basal rate of apoptosis and apoptosis resulting from DNA damage induced by camptothecin, a topoisomerase I inhibitor. These experiments identify for the first time a proapoptotic activity of endogenous parafibromin likely to be important in its role as a tumor suppressor and show a functional role for the NLS of parafibromin in this activity.

Unique pathology in simian immunodeficiency virus-infected rapid progressor macaques is consistent with a pathogenesis distinct from that of classical AIDS

Simian immunodeficiency virus (SIV) infection of macaques and human immunodeficiency virus type 1 (HIV-1) infection of humans result in variable but generally fatal disease outcomes. Most SIV-infected macaques progress to AIDS over a period of 1 to 3 years, in the face of robust SIV-specific immune responses (conventional progressors [CP]). A small number of SIV-inoculated macaques mount transient immune responses and progress rapidly to AIDS (rapid progressors [RP]). We speculated that the underlying pathogenic mechanisms may differ between RP and CP macaques. We compared the pathological lesions, virus loads, and distribution of virus and target cells in SIVsmE660- or SIVsmE543-infected RP and CP rhesus macaques at terminal disease. RP macaques developed a wasting syndrome characterized by severe SIV enteropathy in the absence of opportunistic infections. In contrast, opportunistic infections were commonly observed in CP macaques. RP and CP macaques showed distinct patterns of CD4(+) T-cell depletion, with a selective loss of memory cells in RP macaques and a generalized (naive and memory) CD4 depletion in CP macaques. In situ hybridization demonstrated higher levels of virus expression in lymphoid tissues (P < 0.001) of RP macaques and a broader distribution to include many nonlymphoid tissues. Finally, SIV was preferentially expressed in macrophages in RP macaques whereas the primary target cells in CP macaques were T lymphocytes at end stage disease. These data suggest distinct pathogenic mechanisms leading to the deaths of these two groups of animals, with CP macaques being more representative of HIV-induced AIDS in humans.

Evolution and Function of Leukocyte RNase A Ribonucleases of the Avian Species, Gallus gallus

In this study, we explore the evolution and function of two closely related RNase A ribonucleases from the chicken, Gallus gallus. Separated by approximately 10 kb on chromosome 6, the coding sequences of RNases A-1 and A-2 are diverging under positive selection pressure (dN > dS) but remain similar to one another (81% amino acid identity) and to the mammalian angiogenins. Immunoreactive RNases A-1 and A-2 (both approximately 16 kDa) were detected in peripheral blood granulocytes and bone marrow. Recombinant proteins are ribonucleolytically active (kcat = 2.6 and 0.056 s(-1), respectively), and surprisingly, both interact with human placental ribonuclease inhibitor. RNase A-2, the more cationic (pI 11.0), is both angiogenic and bactericidal; RNase A-1 (pI 10.2) has neither activity. We demonstrated via point mutation of the catalytic His110 that ablation of ribonuclease activity has no impact on the bactericidal activity of RNase A-2. We determined that the divergent domains II (amino acids 71-76) and III (amino acids 89-104) of RNase A-2 are both important for bactericidal activity. Furthermore, we demonstrated that these cationic domains can function as independent bactericidal peptides without the tertiary structure imposed by the RNase A backbone. These results suggest that ribonucleolytic activity may not be a crucial constraint limiting the ongoing evolution of this gene family and that the ribonuclease backbone may be merely serving as a scaffold to support the evolution of novel, nonribonucleolytic proteins.

Human platelets exhibit chemotaxis using functional N-formyl peptide receptors

OBJECTIVE

Activated platelets participate in inflammatory and microbicidal processes by upregulation of surface selectins, shedding of CD40 ligand, and release of platelet microbicidal proteins and microparticles. Given their myeloid lineage, we hypothesized that platelets express functional N-formyl peptide receptors and respond to the bacterially derived chemotactic peptide N-formyl peptide with gradient-driven chemotaxis.

METHODS AND RESULTS

Here we show specific binding of N-formyl peptides to the surface of activated platelets. Platelet expression and function of the formyl peptide receptor, FPR, was verified by RT-PCR of the differentiated megakaryocyte MEG-01 cell line, immunoblotting of platelet proteins, and calcium mobilization in platelets with formyl peptide binding. Furthermore, we demonstrate gradient-driven chemotaxis of platelets by video microscopy and transwell migration toward formyl peptides. We also show that endogenous formyl peptides, released by eukaryotic mitochondria from necrotic cells, induce chemotaxis using formyl peptide receptors expressed by thrombin-activated platelets. Conversely, supernatants from cells undergoing apoptotic cell death do not induce platelet chemotaxis. Platelet chemotaxis to formyl peptides was blocked with FPR-specific antibody as well as by pertussis toxin inhibition of the formyl peptide G-coupled receptor.

CONCLUSION

These data establish a new role for platelets in host defense and suggest reexamination of their active function in microbicidal and other host defense activities.

Platelets deliver costimulatory signals to antigen-presenting cells: A potential bridge between injury and immune activation

The danger model of immunity and tolerance holds that antigen-presenting cells (APCs), activated by stress, injury, or necrosis, but not by physiological (apoptotic) cell death, initiate adaptive immune responses. APC activation is fundamentally associated with binding of CD40 to its ligand CD154. Platelets express CD154 upon activation and are thus potential primal danger signals linking the homeostatic response to trauma to activation of the acquired immune system. Previously, we showed that platelets can undergo gradient-driven migration, or chemotaxis, toward supernatants from cells injured by repeated freeze/thaws, UV light, or ischemia/reperfusion. Herein, we demonstrate that platelet-derived CD154 induces immature dendritic cell maturation with upregulation of costimulatory molecules and IL-12p40 production. Overall, these results provide a mechanism for platelet activation of APC facilitating the induction of adaptive immunity in environments of cell injury.

Microglial function in human APOE3 and APOE4 transgenic mice: altered arginine transport

The APOE4 genotype is a known risk factor for Alzheimer's disease (AD) and is associated with poorer outcomes after neuropathological insults. To understand APOE's function, we have examined microglia, the CNS specific macrophage, in transgenic mice expressing the human APOE3 and APOE4 gene allele. Our data demonstrate that arginine uptake is enhanced in APOE4 microglia compared to APOE3 microglia. The increased arginine uptake in APOE4 Tg microglia is associated with an increased expression of mRNA for cationic amino acid transporter-1 (Cat1), a constuitively expressed member of the arginine selective transport system (the y+ transport system) found in most cells. The macrophage-associated transporter, cationic amino acid transporter 2B (Cat2B) did not demonstrate a change in mRNA expression. This change in microglial arginine transport suggests a potential impact of the APOE4 gene allele on those biochemical pathways such as NO production or cell proliferation to which arginine contributes.

APOE and the regulation of microglial nitric oxide production: a link between genetic risk and oxidative stress

The mechanism linking the APOE4 gene with increased susceptibility for Alzheimer's disease (AD) and poorer outcomes following closed head injury and stroke is unknown. One potential link is activation of the innate immune system in the CNS. Our previously published data demonstrated that apolipoprotein E regulates production of nitric oxide, a critical cytoactive factor released by immune active macrophages. To determine if immune regulation is different in the presence of apolipoprotein E4 compared to apolipoprotein E3, we have measured NO production by peritoneal and CNS macrophages (microglia) cultured from transgenic mice that only express the human apoE4 or apoE3 protein isoform. Significantly more NO was produced in APOE4 mice compared to APOE3 transgenic mice that only express human apoE3 protein. Similarly, monocyte derived macrophages from humans carrying APOE4 gene alleles also produce significantly greater NO than those individuals with APOE3. The mechanism for this isoform-specific difference in NO production is not known and multiple sites in the NO production pathway may be affected. Expression of inducible nitric oxide synthase (iNOS) mRNA and protein are not significantly different between the APOE3 and APOE4 mice, suggesting that induction of iNOS is not a primary cause of the increased NO production in APOE4 animals. One alternative regulatory mechanism that demonstrates isoform specificity is arginine transport, which is greater in microglia from APOE4 transgenic mice compared to microglia from APOE3 mice. Increased transport is consistent with an increased production of NO and may reflect a direct or indirect effect of the APOE genotype on microglial arginine uptake and microglial activation in general. Overall, greater NO production in APOE4 carriers where characteristically high levels of oxidative/nitrosative stress are found in diseases such as AD provides a mechanism that potentially explains the genetic association between APOE4 and human diseases.

Apolipoprotein-E allele-specific regulation of nitric oxide production

Cognitive decline and dementia are key features of Alzheimer's disease (AD) that result from failure of neuronal function. Affected neurons demonstrate indices of nitrosative stress resulting from changes in nitric oxide (NO) mediated redox balance. Neurofibrillary tangles, a characteristic neuropathologic feature of AD, and dysfunctional neurons frequently display 3-nitrotyrosine or other markers of nitrosative stress and immunoreactive nitric oxide synthase (NOS), suggesting that NOS-containing neurons are affected in AD. Our previous studies showed that apolipoprotein E treatment of macrophages increased NO production. Using transgenic mouse models expressing human apoE2, apoE3, or apoE4 protein isoforms and no mouse apoE, we now report an isoform specific difference in microglial NO production. Mice expressing the apoE4 protein isoform have a greater NO production than mice expressing the apoE3 protein isoform. The supply of arginine, the sole substrate for NOS, is dependent on cationic amino acid transporters (CATs) that also demonstrate a similar pattern of apoE isoform dependency. Although arginine transport is greater in APOE4 microglia, this effect is not limited to tissue macrophages. Cortical neurons in primary culture from APOE4 transgenic mice exhibit a similar increase in arginine uptake over neurons cultured from APOE3 mice. The inappropriate levels of arginine transport and of NO in the presence of the APOE4 compared to the APOE3 gene and its products are likely to have significant impact in the CNS.

Apolipoprotein E acts to increase nitric oxide production in macrophages by stimulating arginine transport

Previous studies have shown that apolipoprotein E (apoE) plays a role in immune function by modulating tissue redox balance. Using a mouse macrophage cell line (RAW 264.7), we have examined the mechanism by which apoE regulates nitric oxide (NO) production in macrophages. ApoE potentiates NO production in immune activated RAW cells in combination with lipopolysaccharide or polyinosinic:polycytidylic acid (PIC), agents known to induce expression of inducible nitric oxide synthase mRNA and protein. The effect is not observed with apolipoprotein B or heat-inactivated apoE. The combination of PIC plus apoE produced more NO than the level expected from an additive effect of PIC and apoE alone. Furthermore, this increase was observed at submaximal extracellular arginine concentrations, suggesting that apoE altered arginine (substrate) availability. Examination of [(3)H]arginine uptake across the cell membrane demonstrated that arginine uptake was increased by PIC but further increased by PIC plus apoE. Treatment of RAW cells with apoE was associated with an increased apparent V(max) and decreased affinity for arginine as well as a switch in the induction of mRNA for subtypes of cationic amino acid transporters (CAT). Treatment of RAW cells with PIC plus apoE resulted in the loss of detectable CAT1 mRNA and expression of CAT2 mRNA. Regulation of arginine availability is a novel action of apoE on the regulation of macrophage function and the immune response.

Function of microglia in organotypic slice cultures

We have examined the functional characteristics of microglia in an environment where the cytoarchitecture of the brain is preserved. Using organotypic slice culture under serum-free conditions, microglia initially demonstrated a rounded morphology but after 10 days in vitro (DIV), microglia in the slice were highly branched. Stimulation of the microglia at 4 DIV with phorbol ester significantly increased the number of cells stained with nitroblue tetrazolium, an indicator of superoxide anion production, compared to non-stimulated conditions. At 10 DIV, superoxide anion production was significantly less than that seen at 4 DIV and no increase in production was seen with phorbol ester stimulation. Phagocytosis of fluorescent latex beads and chemotaxis of microglia in response to zymosan activated serum was also reduced at 10 DIV compared to 4 DIV. These experiments indicate that microglia at 4 DIV in tissue slice culture have functional characteristics that resemble microglia in primary culture. However, prolonged culture of the slices results in a return of the microglia to a ramified and functionally down-regulated state, reminiscent of an "in vivo"-like environment. The organotypic slice culture, thus, provides a useful model system to I examine the interactions of microglia with neurons and other glia in the normal and injured brain.

The effects of the naltrexone implant on rodent social interactions and cocaine-induced conditioned place preference

Two experiments were conducted to determine the behavioral properties of the naltrexone implant on: 1) rodent social interactions; and 2) the appetitive properties of cocaine. Rats were surgically implanted with a naltrexone implant (placebo, 10 or 30 mg) and placed into an open field for the recording of social interactions. The naltrexone implants increased latency to initiate contact and decreased pinning, bouts of grooming, and crawl unders on all 7 days. Other rats were surgically implanted with naltrexone (60, 120, or 240 mg) and habituated to a two-chambered conditioned place preference apparatus. After 6 days of conditioning, place preference was computer recorded. Cocaine produced a dose-dependent conditioned place preference in the rats implanted with placebo or 60 mg of naltrexone. The 120 and 240 mg naltrexone implants blocked the emergence of cocaine-induced place preference. The results indicate that naltrexone implants produce significant social behavioral effects within 1 day, and are effective at attenuating the conditioned place preference produced by cocaine.