Validation of an IFN-gamma ELISpot assay to measure cellular immune responses against viral antigens in non-human primates

Adeno-Associated Virus (AAV)-based gene therapy vectors are in development for many inherited human disorders. In nonclinical studies, cellular immune responses mediated by cytotoxic T cells may target vector-transduced cells, which could impact safety and efficacy. Here, we describe the bioanalytical validation of an interferon-gamma (IFN-γ)-based Enzyme-Linked Immunospot (ELISpot) assay for measuring T cell responses against viral antigens in cynomolgus monkeys. Since ELISpots performed with antigen-derived peptides offer a universal assay format, method performance characteristics were validated using widely available peripheral blood mononuclear cells (PBMCs) responsive to cytomegalovirus peptides. The limit of detection and confirmatory cut point were established using statistical methods; precision, specificity, and linearity were confirmed. Monkey PBMCs from an AAV5 gene therapy study were then analyzed, using peptide pools spanning the vector capsid and transgene product. AAV5-specific T cell responses were detected only in 2 of 18 monkeys at Day 28, but not at Day 13 and 56 after vector administration, with no correlation to liver enzyme elevations or transgene expression levels. No transgene product-specific T cell responses occurred. In conclusion, while viral peptide-specific IFN-γ ELISpots can be successfully validated for monkey PBMCs, monitoring peripheral T cell responses in non-clinical AAV5 gene therapy studies was of limited value to interpret safety or efficacy.

Reveglucosidase alfa (BMN 701), an IGF2-Tagged rhAcid α-Glucosidase, Improves Respiratory Functional Parameters in a Murine Model of Pompe Disease

Pompe disease is a rare neuromuscular disorder caused by an acid α-glucosidase (GAA) deficiency resulting in glycogen accumulation in muscle, leading to myopathy and respiratory weakness. Reveglucosidase alfa (BMN 701) is an insulin-like growth factor 2-tagged recombinant human acid GAA (rhGAA) that enhances rhGAA cellular uptake via a glycosylation-independent insulin-like growth factor 2 binding region of the cation-independent mannose-6-phosphate receptor (CI-MPR). The studies presented here evaluated the effects of Reveglucosidase alfa treatment on glycogen clearance in muscle relative to rhGAA, as well as changes in respiratory function and glycogen clearance in respiratory-related tissue in a Pompe mouse model (GAA^tm1Rabn/J). In a comparison of glycogen clearance in muscle with Reveglucosidase alfa and rhGAA, Reveglucosidase alfa was more effective than rhGAA with 2.8-4.7 lower EC₅₀ values, probably owing to increased cellular uptake. The effect of weekly intravenous administration of Reveglucosidase alfa on respiratory function was monitored in Pompe and wild-type mice using whole body plethysmography. Over 12 weeks of 20-mg/kg Reveglucosidase alfa treatment in Pompe mice, peak inspiratory flow (PIF) and peak expiratory flow (PEF) stabilized with no compensation in respiratory rate and inspiratory time during hypercapnic and recovery conditions compared with vehicle-treated Pompe mice. Dose-related decreases in glycogen levels in both ambulatory and respiratory muscles generally correlated to changes in respiratory function. Improvement of murine PIF and PEF were similar in magnitude to increases in maximal inspiratory and expiratory pressure observed clinically in late onset Pompe patients treated with Reveglucosidase alfa (Byrne et al., manuscript in preparation).

Mitophagy defects arising from BNip3 loss promote mammary tumor progression to metastasis

BNip3 is a hypoxia-inducible protein that targets mitochondria for autophagosomal degradation. We report a novel tumor suppressor role for BNip3 in a clinically relevant mouse model of mammary tumorigenesis. BNip3 delays primary mammary tumor growth and progression by preventing the accumulation of dysfunctional mitochondria and resultant excess ROS production. In the absence of BNip3, mammary tumor cells are unable to reduce mitochondrial mass effectively and elevated mitochondrial ROS increases the expression of Hif-1α and Hif target genes, including those involved in glycolysis and angiogenesis—two processes that are also markedly increased in BNip3-null tumors. Glycolysis inhibition attenuates the growth of BNip3-null tumor cells, revealing an increased dependence on autophagy for survival. We also demonstrate that BNIP3 deletion can be used as a prognostic marker of tumor progression to metastasis in human triple-negative breast cancer (TNBC). These studies show that mitochondrial dysfunction—caused by defects in mitophagy—can promote the Warburg effect and tumor progression, and suggest better approaches to stratifying TNBC for treatment.

Abstract 4316: BNIP3 suppresses mammary tumorigenesis and metastasis through negative regulation of Warburg effect and HIF-1α

BNIP3 is a hypoxia-inducible protein involved in mitochondrial dynamics and mitophagy that is up-regulated at pre-malignant stages of various human cancers, including breast cancer but down-regulated at later stages of tumorigenesis. To examine the role of BNip3 in tumor progression, we crossed BNip3 null mice to the MMTV-PyMT mouse model of breast cancer. Loss of BNip3 promoted primary tumor growth in vivo and tumor cell proliferation in vitro and was associated with increased aerobic glycolysis and reduced mitochondrial respiration. BNip3 null tumor cells also showed increased invasive properties that were cell intrinsic and transplantable to wild-type host mice. Consistently, there was reduced latency to lung metastasis in the MMTV-PyMT;BNip3-/- mice and increased numbers of metastases compared to control mice. BNip3 null tumors exhibited increased mitochondrial mass, but a greater fraction of mitochondria were dysfunctional with reduced membrane potential and decreased metabolite uptake compared to BNip3 wild-type tumor cells. Consistently, increased proliferation of BNip3 null tumor cells was associated with increased carbon flux from glucose to lipid and nucleic acids. Interestingly, although mitochondria were less efficient at uptake of pyruvate and glutamine, the rate of production of Krebs cycle intermediates was increased. This indicates that defective mitochondria due to inefficient mitophagy can induce the Warburg effect, as originally proposed by Warburg himself. Loss of BNip3 also resulted in more hypoxic tumors that expressed increased levels of Hif-1α and its target genes and showed increased angiogenesis, although blood vessels were abnormal possibly explaining increased tumor hypoxia, thus suggesting a negative feedback loop between Hif-1α and its target gene, BNip3. Inhibition of glycolysis or inhibition of HIF activity reduced proliferation in BNip3 null tumor cells to the levels observed in control cells. Significantly, BNip3 null tumor cells underwent autophagic flux as efficiently as wild-type cells demonstrating for the first time that inhibition of mitophagy has a distinct tumorigenic consequence to general inactivation of autophagy, as reported elsewhere. These results demonstrate that BNip3 has tumor and metastasis suppressor properties required to maintain mitochondrial integrity, promote oxidative metabolism and mitigate against the metastasis promoting activities of hypoxia and glycolytic metabolism.

Citation Format: Aparajita Hoskote Chourasia, Kristin Tracy, Michelle Boland, Marina Sharifi, Kay F. Macleod. BNIP3 suppresses mammary tumorigenesis and metastasis through negative regulation of Warburg effect and HIF-1α. [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 4316. doi:10.1158/1538-7445.AM2014-4316

Abstract 3938: BNip3 limits HIF-1α stabilization and metastasis in a mouse model of breast cancer through effects on mitochondrial integrity and ROS generation

BNIP3 is a hypoxia-inducible mitochondrial protein that has been implicated in mitochondrial fragmentation and mitophagy. BNIP3 protein is also up-regulated at pre-malignant stages of various different human cancers, including breast cancer and down-regulated later through a variety of mechanisms. To examine the role of BNip3 in tumor progression to metastasis, we crossed mice carrying a targeted deletion in the mouse BNip3 gene to the MMTV-PyMT mouse model of breast cancer. All analyses were performed with mice on a pure FVB/N genetic background. Loss of BNip3 promoted S phase entry that was associated with increased primary tumor growth. There was highly significant increase in the numbers of lung metastases and a reduced latency to metastasis in the MMTV-PyMT;BNip3-/- mice compared to control MMTV-PyMT;BNip3+/+ mice. BNip3 null tumors showed increased invasive properties and nuclear grade at earlier stages, a phenotype that was transplantable to wild-type host mice arguing that the increased invasiveness was intrinsic to BNip3 null tumor cells. BNip3 null tumor cells exhibited abnormal mitochondria, reduced mitochondrial membrane potential, increased ROS levels and increased hypoxia. Their invasive pathology was also associated with increased HIF-1α levels, increased HIF target gene expression and increased CD31-positive blood vessel formation. Quenching ROS limited Hif-1α stabilization, reduced angiogenesis and metastasis in MMTV-PyMT;BNip3-/- mouse tumors to wild-type levels. These results suggest that BNip3 is a metastasis suppressor by virtue of its role in maintaining mitochondrial integrity that mitigates against the metastasis promoting activity of reactive oxygen and hypoxia. Work on this project is supported by NIH/NCI RO1-CA131188 and by Department of Defense BRCP W81XWH-09-1-0587.

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 3938. doi:1538-7445.AM2012-3938

Abstract 2804: Increased metastasis linked to defective mitochondria and elevated ROS in BNip3 deficient mammary tumorigenesis

BNIP3 is a hypoxia-inducible mitochondrial protein that has been implicated in mitochondrial fragmentation and subsequent mitophagy. BNIP3 protein has also been shown to be up-regulated at pre-malignant stages of various different human cancers, including breast cancer and down-regulated later through a variety of mechanisms, including promoter methylation and altered sub-cellular localization. With an established role for hypoxia in promoting invasiveness and progression to metastasis in breast cancer, we were interested to determine how BNIP3 (as a HIF target gene) acted in tumor progression. To do this, we crossed mice carrying a targeted deletion in the mouse BNip3 gene to the MMTV-PyMT mouse model of breast cancer. All analyses were performed on mice backcrossed onto a pure FVB/N genetic background. We show that while loss of BNip3 has only a modest effect on primary tumor growth, there is a highly significant increase in the numbers of lung metastases and a reduced latency to metastasis in the MMTV-PyMTl;BNip3-/- mice compared to control MMTV-PyMT;BNip3+/+ mice. BNip3 null tumors showed increased invasive properties and nuclear grade at earlier stages that were transplantable to wild-type host mice arguing that the phenotype was cell-intrinsic to BNip3 null tumor cells. This invasive pathology was also associated with increased tumor cell proliferation, increased HIF-1α levels, increased CD31-positive blood vessel formation and elevated MMPase activity. BNip3 null tumor cells exhibited abnormal mitochondria, reduced mitochondrial membrane potential and increased ROS levels. In vitro, quenching ROS limited the increased invasion/migration properties of BNip3 null tumor cells under hypoxia. These results suggest that BNip3 is a metastasis suppressor by virtue of its role in maintaining mitochondrial integrity that mitigates against the metastasis promoting activity of hypoxia.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2804. doi:10.1158/1538-7445.AM2011-2804

BNIP3 is an RB/E2F target gene required for hypoxia-induced autophagy

Hypoxia and nutrient deprivation are environmental stresses governing the survival and adaptation of tumor cells in vivo. We have identified a novel role for the Rb tumor suppressor in protecting against nonapoptotic cell death in the developing mouse fetal liver, in primary mouse embryonic fibroblasts, and in tumor cell lines. Loss of pRb resulted in derepression of BNip3, a hypoxia-inducible member of the Bcl-2 superfamily of cell death regulators. We identified BNIP3 as a direct target of pRB/E2F-mediated transcriptional repression and showed that pRB attenuates the induction of BNIP3 by hypoxia-inducible factor to prevent autophagic cell death. BNIP3 was essential for hypoxia-induced autophagy, and its ability to promote autophagosome formation was enhanced under conditions of nutrient deprivation. Knockdown of BNIP3 reduced cell death, and remaining deaths were necrotic in nature. These studies identify BNIP3 as a key regulator of hypoxia-induced autophagy and suggest a novel role for the RB tumor suppressor in preventing nonapoptotic cell death by limiting the extent of BNIP3 induction in cells.

Regulation of mitochondrial integrity, autophagy and cell survival by BNIP3

Understanding the role of BNIP3 in the systemic response to hypoxia has been complicated by conflicting results that indicate on the one hand that BNIP3 promotes cell death, and other data, including our own that BNIP3 is not sufficient for cell death, but rather plays a critical role in hypoxia-induced autophagy. This work suggests that rather than promoting death, BNIP3 may actually allow survival either by preventing ATP depletion or by eliminating damaged mitochondria. However, the function of BNIP3 may be subverted under unusual conditions associated with acidosis that arise following extended periods of hypoxia and anaerobic glycolysis. Despite this novel insight into BNIP3 function, much remains to be done in terms of pinning down a molecular activity for BNIP3 that explains both its role in autophagy and how this may be subverted to induce cell death. As a target of the RB tumor suppressor, our work also places BNIP3 at the center of efforts to exploit autophagy to better treat human cancers in which tumor hypoxia is implicated as a progression factor.

Vitamin E treatment for tardive dyskinesia. Veterans Affairs Cooperative Study #394 Study Group

BACKGROUND

Several short-term, controlled trials have documented the efficacy of vitamin E in treating tardive dyskinesia. However, the persistent nature of the disease prompted us to perform a multicenter, longer-term trial of vitamin E.

METHODS

The study was a prospective, randomized, 9-site trial of up to 2 years of treatment with d-vitamin E (1600 IU/d) vs matching placebo. One hundred fifty-eight subjects with tardive dyskinesia who were receiving neuroleptic medications were enrolled. The blinded assessments performed were clinical (Abnormal Involuntary Movements Scale, Barnes Akathisia Scale, and Modified Simpson-Angus [for Extrapyramidal Symptoms] Scale) and electromechanical assessments of movement disorders, psychiatric status (Brief Psychiatric Rating Scale), and functioning (Global Assessment of Functioning). There were no significant differences in baseline demographic characteristics or in study assessments between the group that received vitamin E and the group that received placebo.

RESULTS

Vitamin E was well tolerated and subject compliance with medication was good and similar between treatment groups. One hundred seven subjects (70% of those receiving vitamin E and 66% of subjects receiving placebo) completed at least 1 year of treatment. There were no significant effects of vitamin E on total scores or subscale scores for the AIMS, electromechanical measures of dyskinesia, or scores from the other 4 scales.

CONCLUSION

This long-term, randomized trial of vitamin E vs placebo found no evidence for efficacy of vitamin E in the treatment of tardive dyskinesia.

Reliability of an instrumental assessment of tardive dyskinesia: results from VA Cooperative Study #394

Nine VA Medical Centers are participating in a 2-year double-blind placebo controlled study of antioxidant treatment for tardive dyskinesia (TD) conducted by the Department of Veteran Affairs Cooperative Studies Program. One of the principal outcome measures of this study is the score derived from the instrumental assessment of upper extremity dyskinesia. Dyskinetic hand movements are quantified by assessing the variability associated with steady-state isometric force generated by the patient. In the present report, we describe the training procedures and results of a multi-center reliability assessment of this procedure. Data from nine study centers comprising 45 individual patients with six trials each (three from left hand and three from right hand) were reanalyzed by an independent investigator and the results were subjected to reliability assessment. For the statistic of interest (average coefficient of variation over trials 2 and 3 for each hand, then take the larger of these two values), we found very high intraclass correlation coefficients for reliability over all patients across sites (ICC = 0.995). We also calculated the reliability of the measures across trials within patient for each combination of hand (right, left, dominant), rater group (site, control), and trials set (all three, trials 2 and 3). For a given hand and trial set, the reliability of the site raters was similar to that of the control. This study demonstrates that instrumental measures for the assessment of dyskinesia are reliable and can be implemented in multi-center studies with minimal training.

Interrater reliability issues in multicenter trials, Part II: Statistical procedures used in Department of Veterans Affairs Cooperative Study #394

The primary goal of Veterans Affairs (VA) Cooperative Study (CS) #394 is to determine if vitamin E is a safe and efficacious treatment for tardive dyskinesia (TD). The study uses various instruments to assess subjects for movement disorders (Abnormal Involuntary Movement Scale [AIMS], and Barnes Akathisia Scale [BAS]), psychopathology (Anchored Brief Psychiatric Rating Scale [BPRS]), and level of functioning (Global Assessment of Functioning scale [GAF]). Since the study involves nine sites, each with its own set of raters, it is important to establish and maintain high interrater reliability (IRR) on these instruments throughout the study and to identify raters who differ significantly from the others. To make this determination, personnel at each site assessed subjects from standardized videotapes on the AIMS, BAS, and Anchored BPRS, and rated written vignettes on the GAF. We fit these data to a two-way additive model to identify nonstandardized raters (i.e., those whose average ratings were significantly lower or higher than the others, or those whose scores, after adjusting for subject and rater effects, were highly variable). The proportion of nonstandardized raters ranged from 7 percent (Anchored BPRS) to 33 percent (AIMS). The estimated intraclass correlation coefficients (ICCs) indicated moderate reliability for the AIMS, BAS, and Anchored BPRS (0.73 to 0.75) and excellent agreement for the GAF (0.90). The companion article (Part I: Tracy et al. 1997, page 53 of this issue) describes the procedures used to train the raters for this study.

Interrater reliability issues in multicenter trials, Part I: Theoretical concepts and operational procedures used in Department of Veterans Affairs Cooperative Study #394

This article describes a standardized method for establishing and maintaining desired levels of interrater reliability (IRR) in multicenter trials. The procedure involves six steps: distribution of procedural guides, distribution of an introduction tape, initial distribution of patient interviews to rate, training at the study kickoff meeting, ongoing IRR monitoring, and group training throughout the study. This method is being used in a national Veterans Affairs Cooperative Study (CS #394), involving nine sites to examine the treatment effects of vitamin E on tardive dyskinesia. The six-step standardized process allowed for early detection of areas of concern in assessment administration. When comparing intraclass correlation coefficients (ICCs) at different points in the initial training, the Barnes Akathisia Scale and Anchored Brief Psychiatric Rating Scale reliability improved from 0.68 to 0.74 and from 0.54 to 0.87, respectively. After analyzing the ratings collected prior to the start of CS #394, data were collected to conduct the first check on Abnormal Involuntary Movement Scale (AIMS) IRR during enrollment; the estimated ICC for the AIMS had decreased from 0.87 to 0.60. Raters were instructed to re-assess the subjects from the first videotape on the AIMS and received additional training. The re-rating indicated very good reliability, 0.84, IRR was measured once for the Global Assessment of Functioning Scale resulting in an ICC of 0.90. The companion article (Part II: Edson et al. 1997, page 59 of this issue) describes the statistical procedures used to measure IRR.

Adrenocorticotropin, beta-endorphin, and beta-lipotropin in normal thyroid and lung: possible implications for ectopic hormone secretion

The expression of the proopiomelanocortin (POMC) gene by normal lung and thyroid was examined by measurement of the content of ACTH, beta-lipotropin (beta LPH), and beta-endorphin (beta EP) in porcine lung and thyroid tissue. Acid extracts of normal porcine lung and thyroid tissue each contained appreciable amounts of immunoreactive (ir) ACTH, ir-beta LPH, and ir-beta EP. The content of ir-beta LPH in both tissues exceeded by severalfold, on a molar basis, the content of ir-ACTH and ir-beta EP, suggesting that the common precursor POMC was processed predominantly to peptides other than ir-ACTH and ir-beta EP. A porcine thyroid extract (Calcitare, porcine calcitonin, Armour) showed equivalent levels of beta EP-like immunoreactivity and bioactivity, measured by opiate radioreceptor assay; in contrast, ACTH-like bioactivity, measured by rat zona fasciculata steroidogenesis, was only 4% of ACTH-like immunoreactivity. On reversed phase high performance liquid chromatography, Calcitare showed multiple peaks of ACTH-like immunoreactivity, one of which coeluted with porcine ACTH-(1-39), and two much smaller peaks of beta EP-like immunoreactivity, of which the smaller coeluted with porcine beta EP. These data suggest that both lung and thyroid gland synthesize POMC, which in normal tissue is usually predominantly processed to species other than ACTH and beta EP. Ectopic secretion of ACTH and beta EP by lung and thyroid neoplasms may thus represent the loss of a system(s) normally responsible for processing the precursor beyond ACTH and beta EP.