Mitochondrial Dysfunction, Oxidative Stress, and Inter-Organ Miscommunications in T2D Progression.

Type 2 diabetes (T2D) is a heterogenous disease, and conventionally, peripheral insulin resistance (IR) was thought to precede islet ß-cell dysfunction, promoting progression from prediabetes to T2D. New evidence suggests that T2D-lean individuals experience early ß-cell dysfunction without significant IR. Regardless of the primary event (i.e., IR vs. ß-cell dysfunction) that contributes to dysglycemia, significant early-onset oxidative damage and mitochondrial dysfunction in multiple metabolic tissues may be a driver of T2D onset and progression. Oxidative stress, defined as the generation of reactive oxygen species (ROS), is mediated by hyperglycemia alone or in combination with lipids. Physiological oxidative stress promotes inter-tissue communication, while pathological oxidative stress promotes inter-tissue mis-communication, and new evidence suggests that this is mediated via extracellular vesicles (EVs), including mitochondria containing EVs. Under metabolic-related stress conditions, EV-mediated cross-talk between ß-cells and skeletal muscle likely trigger mitochondrial anomalies leading to prediabetes and T2D. This article reviews the underlying molecular mechanisms in ROS-related pathogenesis of prediabetes, including mitophagy and mitochondrial dynamics due to oxidative stress. Further, this review will describe the potential of various therapeutic avenues for attenuating oxidative damage, reversing prediabetes and preventing progression to T2D.

DOC2b Enhances ß-Cell Function via a Novel Tyrosine Phosphorylation-Dependent Mechanism.

Double C2 domain Β (DOC2b) protein is required for glucose-stimulated insulin secretion (GSIS) in ß-cells, the underlying mechanism of which remains unresolved. Our biochemical analysis using primary human islets and human and rodent clonal ß-cells revealed that DOC2b is tyrosine phosphorylated within 2 min of glucose stimulation, and Src family kinase member YES is required for this process. Biochemical and functional analysis using DOC2bY301 mutants revealed the requirement of Y301 phosphorylation for the interaction of DOC2b with YES kinase and increased content of VAMP2, a protein on insulin secretory granules, at the plasma membrane (PM), concomitant with DOC2b-mediated enhancement of GSIS in ß-cells. Coimmunoprecipitation studies demonstrated an increased association of DOC2b with ERM family proteins in ß-cells following glucose stimulation or pervanadate treatment. Y301 phosphorylation-competent DOC2b was required to increase ERM protein activation, and ERM protein knockdown impaired DOC2b-mediated boosting of GSIS, suggesting that tyrosine-phosphorylated DOC2b regulates GSIS via ERM-mediated granule localization to the PM. Taken together, these results demonstrate the glucose-induced posttranslational modification of DOC2b in ß-cells, pinpointing the kinase, site of action, and downstream signaling events and revealing a regulatory role of YES kinase at various steps in GSIS. This work will enhance the development of novel therapeutic strategies to restore glucose homeostasis in diabetes.

Changes in Skeletal Muscle PAK1 Levels Regulate Tissue Crosstalk to Impact Whole Body Glucose Homeostasis.

Skeletal muscle accounts for ~80% of insulin-stimulated glucose uptake. The Group I p21-activated kinase 1 (PAK1) is required for the non-canonical insulin-stimulated GLUT4 vesicle translocation in skeletal muscle cells. We found that the abundances of PAK1 protein and its downstream effector in muscle, ARPC1B, are significantly reduced in the skeletal muscle of humans with type 2 diabetes, compared to the non-diabetic controls, making skeletal muscle PAK1 a candidate regulator of glucose homeostasis. Although whole-body PAK1 knockout mice exhibit glucose intolerance and are insulin resistant, the contribution of skeletal muscle PAK1 in particular was unknown. As such, we developed inducible skeletal muscle-specific PAK1 knockout (skmPAK1-iKO) and overexpression (skmPAK1-iOE) mouse models to evaluate the role of PAK1 in skeletal muscle insulin sensitivity and glucose homeostasis. Using intraperitoneal glucose tolerance and insulin tolerance testing, we found that skeletal muscle PAK1 is required for maintaining whole body glucose homeostasis. Moreover, PAK1 enrichment in GLUT4-myc-L6 myoblasts preserves normal insulin-stimulated GLUT4 translocation under insulin resistance conditions. Unexpectedly, skmPAK1-iKO also showed aberrant plasma insulin levels following a glucose challenge. By applying conditioned media from PAK1-enriched myotubes or myoblasts to ß-cells in culture, we established that a muscle-derived circulating factor(s) could enhance ß-cell function. Taken together, these data suggest that PAK1 levels in the skeletal muscle can regulate not only skeletal muscle insulin sensitivity, but can also engage in tissue crosstalk with pancreatic ß-cells, unveiling a new molecular mechanism by which PAK1 regulates whole-body glucose homeostasis.

Syntaxin 4 Enrichment in ß-Cells Prevents Conversion to Autoimmune Diabetes in Non-Obese Diabetic (NOD) Mice.

Syntaxin 4 (STX4), a plasma membrane-localized SNARE protein, regulates human islet ß-cell insulin secretion and preservation of ß-cell mass. We found that human type 1 diabetes (T1D) and NOD mouse islets show reduced ß-cell STX4 expression, consistent with decreased STX4 expression, as a potential driver of T1D phenotypes. To test this hypothesis, we generated inducible ß-cell-specific STX4-expressing NOD mice (NOD-ißSTX4). Of NOD-ißSTX4 mice, 73% had sustained normoglycemia vs. <20% of control NOD (NOD-Ctrl) mice by 25 weeks of age. At 12 weeks of age, before diabetes conversion, NOD-ißSTX4 mice demonstrated superior whole-body glucose tolerance and ß-cell glucose responsiveness than NOD-Ctrl mice. Higher ß-cell mass and reduced ß-cell apoptosis were also detected in NOD-ißSTX4 pancreata compared with pancreata of NOD-Ctrl mice. Single-cell RNA sequencing revealed that islets from NOD-ißSTX4 had markedly reduced interferon-γ signaling and tumor necrosis factor-α signaling via nuclear factor-κB in islet ß-cells, including reduced expression of the chemokine CCL5; CD4+ regulatory T cells were also enriched in NOD-ißSTX4 islets. These results provide a deeper mechanistic understanding of STX4 function in ß-cell protection and warrant further investigation of STX4 enrichment as a strategy to reverse or prevent T1D in humans or protect ß-cell grafts.

Conventional and Unconventional Mechanisms by which Exocytosis Proteins Oversee ß-cell Function and Protection.

Type 2 diabetes (T2D) is one of the prominent causes of morbidity and mortality in the United States and beyond, reaching global pandemic proportions. One hallmark of T2D is dysfunctional glucose-stimulated insulin secretion from the pancreatic ß-cell. Insulin is secreted via the recruitment of insulin secretory granules to the plasma membrane, where the soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and SNARE regulators work together to dock the secretory granules and release insulin into the circulation. SNARE proteins and their regulators include the Syntaxins, SNAPs, Sec1/Munc18, VAMPs, and double C2-domain proteins. Recent studies using genomics, proteomics, and biochemical approaches have linked deficiencies of exocytosis proteins with the onset and progression of T2D. Promising results are also emerging wherein restoration or enhancement of certain exocytosis proteins to ß-cells improves whole-body glucose homeostasis, enhances ß-cell function, and surprisingly, protection of ß-cell mass. Intriguingly, overexpression and knockout studies have revealed novel functions of certain exocytosis proteins, like Syntaxin 4, suggesting that exocytosis proteins can impact a variety of pathways, including inflammatory signaling and aging. In this review, we present the conventional and unconventional functions of ß-cell exocytosis proteins in normal physiology and T2D and describe how these insights might improve clinical care for T2D.

Syntaxin 4 Mediates NF-κB Signaling and Chemokine Ligand Expression via Specific Interaction With IκBß.

Enrichment of human islets with syntaxin 4 (STX4) improves functional ß-cell mass through a nuclear factor-κB (NF-κB)-dependent mechanism. However, the detailed mechanisms underlying the protective effect of STX4 are unknown. For determination of the signaling events linking STX4 enrichment and downregulation of NF-κB activity, STX4 was overexpressed in human islets, EndoC-ßH1 and INS-1 832/13 cells in culture, and the cells were challenged with the proinflammatory cytokines interleukin-1ß, tumor necrosis factor-α, and interferon-γ individually and in combination. STX4 expression suppressed cytokine-induced proteasomal degradation of IκBß but not IκBα. Inhibition of IKKß prevented IκBß degradation, suggesting that IKKß phosphorylates IκBß. Moreover, the IKKß inhibitor, as well as a proteosomal degradation inhibitor, prevented the loss of STX4 caused by cytokines. This suggests that STX4 may be phosphorylated by IKKß in response to cytokines, targeting STX4 for proteosomal degradation. Expression of a stabilized form of STX4 further protected IκBß from proteasomal degradation, and like wild-type STX4, stabilized STX4 coimmunoprecipitated with IκBß and the p50-NF-κB. This work proposes a novel pathway wherein STX4 regulates cytokine-induced NF-κB signaling in ß-cells via associating with and preventing IκBß degradation, suppressing chemokine expression, and protecting islet ß-cells from cytokine-mediated dysfunction and demise.

A requirement for PAK1 to support mitochondrial function and maintain cellular redox balance via electron transport chain proteins to prevent ß-cell apoptosis.

OBJECTIVE: p21 (Cdc42/Rac1) activated Kinase 1 (PAK1) is a candidate susceptibility factor for type 2 diabetes (T2D). PAK1 is depleted in the islets from T2D donors, compared to control individuals. In addition, whole-body PAK1 knock out (PAK1-KO) in mice worsens the T2D-like effects of high-fat diet. The current study tested the effects of modulating PAK1 levels only in ß-cells. MATERIALS/METHODS: ß-cell-specific inducible PAK1 KO (ßPAK1-iKO) mice were generated and used with human ß-cells and T2D islets to evaluate ß-cell function. RESULTS: ßPAK1-iKO mice exhibited glucose intolerance and elevated ß-cell apoptosis, but without peripheral insulin resistance. ß-cells from ßPAK-iKO mice also contained fewer mitochondria per cell. At the cellular level, human PAK1-deficient ß-cells showed blunted glucose-stimulated insulin secretion and reduced mitochondrial function. Mitochondria from human PAK1-deficient ß-cells were deficient in the electron transport chain (ETC) subunits CI, CIII, and CIV; NDUFA12, a CI complex protein, was identified as a novel PAK1 binding partner, and was significantly reduced with PAK1 knockdown. PAK1 knockdown disrupted the NAD+/NADH and NADP+/NADPH ratios, and elevated ROS. An imbalance of the redox state due to mitochondrial dysfunction leads to ER stress in ß-cells. PAK1 replenishment in the ß-cells of T2D human islets ameliorated levels of ER stress markers. CONCLUSIONS: These findings support a protective function for PAK1 in ß-cells. The results support a new model whereby the PAK1 in the ß-cell plays a required role upstream of mitochondrial function, via maintaining ETC protein levels and averting stress-induced ß-cell apoptosis to retain healthy functional ß-cell mass.

DOC2B promotes insulin sensitivity in mice via a novel KLC1-dependent mechanism in skeletal muscle.

AIMS/HYPOTHESIS: Skeletal muscle accounts for >80% of insulin-stimulated glucose uptake; dysfunction of this process underlies insulin resistance and type 2 diabetes. Insulin sensitivity is impaired in mice deficient in the double C2 domain ß (DOC2B) protein, while whole-body overexpression of DOC2B enhances insulin sensitivity. Whether insulin sensitivity in the skeletal muscle is affected directly by DOC2B or is secondary to an effect on other tissues is unknown; the underlying molecular mechanisms also remain unclear. METHODS: Human skeletal muscle samples from non-diabetic or type 2 diabetic donors were evaluated for loss of DOC2B during diabetes development. For in vivo analysis, new doxycycline-inducible skeletal-muscle-specific Doc2b-overexpressing mice fed standard or high-fat diets were evaluated for insulin and glucose tolerance, and insulin-stimulated GLUT4 accumulation at the plasma membrane (PM). For in vitro analyses, a DOC2B-overexpressing L6-GLUT4-myc myoblast/myotube culture system was coupled with an insulin resistance paradigm. Biochemical and molecular biology methods such as site-directed mutagenesis, co-immunoprecipitation and mass spectrometry were used to identify the molecular mechanisms linking insulin stimulation to DOC2B. RESULTS: We identified loss of DOC2B (55% reduction in RNA and 40% reduction in protein) in the skeletal muscle of human donors with type 2 diabetes. Furthermore, inducible enrichment of DOC2B in skeletal muscle of transgenic mice enhanced whole-body glucose tolerance (AUC decreased by 25% for female mice) and peripheral insulin sensitivity (area over the curve increased by 20% and 26% for female and male mice, respectively) in vivo, underpinned by enhanced insulin-stimulated GLUT4 accumulation at the PM. Moreover, DOC2B enrichment in skeletal muscle protected mice from high-fat-diet-induced peripheral insulin resistance, despite the persistence of obesity. In L6-GLUT4-myc myoblasts, DOC2B enrichment was sufficient to preserve normal insulin-stimulated GLUT4 accumulation at the PM in cells exposed to diabetogenic stimuli. We further identified that DOC2B is phosphorylated on insulin stimulation, enhancing its interaction with a microtubule motor protein, kinesin light chain 1 (KLC1). Mutation of Y301 in DOC2B blocked the insulin-stimulated phosphorylation of DOC2B and interaction with KLC1, and it blunted the ability of DOC2B to enhance insulin-stimulated GLUT4 accumulation at the PM. CONCLUSIONS/INTERPRETATION: These results suggest that DOC2B collaborates with KLC1 to regulate insulin-stimulated GLUT4 accumulation at the PM and regulates insulin sensitivity. Our observation provides a basis for pursuing DOC2B as a novel drug target in the muscle to prevent/treat type 2 diabetes.

Syntaxin 4 Expression in Pancreatic ß-Cells Promotes Islet Function and Protects Functional ß-Cell Mass.

Syntaxin 4 (Stx4) enrichment in human and mouse islet grafts improves the success of transplants in reversing streptozotocin (STZ)-induced diabetes in mice, although the underlying molecular mechanisms remain elusive. Toward a further understanding of this, human islets and inducible transgenic mice that selectively overexpress Stx4 in islet ß-cells (ßTG-Stx4) were challenged with proinflammatory stressors in vitro and in vivo. Remarkably, ßTG-Stx4 mice resisted the loss of ß-cell mass and the glucose intolerance that multiple low doses of STZ induce. Under standard conditions, glucose tolerance was enhanced and mice maintained normal fasting glycemia and insulinemia. Conversely, Stx4 heterozygous knockout mice succumbed rapidly to STZ-induced glucose intolerance compared with their wild-type littermates. Human islet ß-cells overexpressing Stx4 exhibited enhanced insulin secretory capability; resilience against proinflammatory cytokine-induced apoptosis; and reduced expression of the CXCL9, CXCL10, and CXCL11 genes coordinate with decreased activation/nuclear localization of nuclear factor-κB. Finding ways to boost Stx4 expression presents a novel potential therapeutic avenue for promoting islet function and preserving ß-cell mass.

Impact of silencing hepatic SREBP-1 on insulin signaling.

Sterol Regulatory Element Binding Protein-1 (SREBP-1) is a conserved transcription factor of the basic helix-loop-helix leucine zipper family (bHLH-Zip) that plays a central role in regulating expression of genes of carbohydrate and fatty acid metabolism in the liver. SREBP-1 activity is essential for the control of insulin-induced anabolic processes during the fed state. In addition, SREBP-1 regulates expression of key molecules in the insulin signaling pathway, including insulin receptor substrate 2 (IRS2) and a subunit of the phosphatidylinositol 3-kinase (PI3K) complex, PIK3R3, suggesting that feedback mechanisms exist between SREBP-1 and this pathway. Nevertheless, the overall contribution of SREBP-1 activity to maintain insulin signal transduction is unknown. Furthermore, Akt is a known activator of mTORC1, a sensor of energy availability that plays a fundamental role in metabolism, cellular growth and survival. We have silenced SREBP-1 and explored the impact on insulin signaling and mTOR in mice under fed, fasted and refed conditions. No alterations in circulating levels of insulin were observed. The studies revealed that depletion of SREBP-1 had no impact on IRS1Y612, AktS473, and downstream effectors GSK3αS21 and FoxO1S256 during the fed state. Nevertheless, reduced levels of these molecules were observed under fasting conditions. These effects were not associated with changes in phosphorylation of mTOR. Overall, our data indicate that the contribution of SREBP-1 to maintain insulin signal transduction in liver is modest.

Doc2b Protects ß-Cells Against Inflammatory Damage and Enhances Function.

Loss of functional ß-cell mass is an early feature of type 1 diabetes. To release insulin, ß-cells require soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes, as well as SNARE complex regulatory proteins like double C2 domain-containing protein ß (Doc2b). We hypothesized that Doc2b deficiency or overabundance may confer susceptibility or protection, respectively, to the functional ß-cell mass. Indeed, Doc2b+/- knockout mice show an unusually severe response to multiple-low-dose streptozotocin (MLD-STZ), resulting in more apoptotic ß-cells and a smaller ß-cell mass. In addition, inducible ß-cell-specific Doc2b-overexpressing transgenic (ßDoc2b-dTg) mice show improved glucose tolerance and resist MLD-STZ-induced disruption of glucose tolerance, fasting hyperglycemia, ß-cell apoptosis, and loss of ß-cell mass. Mechanistically, Doc2b enrichment enhances glucose-stimulated insulin secretion (GSIS) and SNARE activation and prevents the appearance of apoptotic markers in response to cytokine stress and thapsigargin. Furthermore, expression of a peptide containing the Doc2b tandem C2A and C2B domains is sufficient to confer the beneficial effects of Doc2b enrichment on GSIS, SNARE activation, and apoptosis. These studies demonstrate that Doc2b enrichment in the ß-cell protects against diabetogenic and proapoptotic stress. Furthermore, they identify a Doc2b peptide that confers the beneficial effects of Doc2b and may be a therapeutic candidate for protecting functional ß-cell mass.

Exocytosis Protein DOC2B as a Biomarker of Type 1 Diabetes.

Context: Efforts to preserve ß-cell mass in the preclinical stages of type 1 diabetes (T1D) are limited by few blood-derived biomarkers of ß-cell destruction. Objective: Platelets are proposed sources of blood-derived biomarkers for a variety of diseases, and they show distinct proteomic changes in T1D. Thus, we investigated changes in the exocytosis protein, double C2 domain protein-ß (DOC2B) in platelets and islets from T1D humans, and prediabetic nonobese diabetic (NOD) mice. Design, Patients, and Main Outcome Measure: Protein levels of DOC2B were assessed in platelets and islets from prediabetic NOD mice and humans, with and without T1D. Seventeen new-onset T1D human subjects (10.3 ± 3.8 years) were recruited immediately following diagnosis, and platelet DOC2B levels were compared with 14 matched nondiabetic subjects (11.4 ± 2.9 years). Furthermore, DOC2B levels were assessed in T1D human pancreatic tissue samples, cytokine-stimulated human islets ex vivo, and platelets from T1D subjects before and after islet transplantation. Results: DOC2B protein abundance was substantially reduced in prediabetic NOD mouse platelets, and these changes were mirrored in the pancreatic islets from the same mice. Likewise, human DOC2B levels were reduced over twofold in platelets from new-onset T1D human subjects, and this reduction was mirrored in T1D human islets. Cytokine stimulation of normal islets reduced DOC2B expression ex vivo. Remarkably, platelet DOC2B levels increased after islet transplantation in patients with T1D. Conclusions: Reduction of DOC2B is an early feature of T1D, and DOC2B abundance may serve as a valuable in vivo indicator of ß-cell mass and an early biomarker of T1D.

The p21-activated kinase (PAK1) is involved in diet-induced beta cell mass expansion and survival in mice and human islets.

AIMS/HYPOTHESIS: Human islets from type 2 diabetic donors are reportedly 80% deficient in the p21 (Cdc42/Rac)-activated kinase, PAK1. PAK1 is implicated in beta cell function and maintenance of beta cell mass. We questioned the mechanism(s) by which PAK1 deficiency potentially contributes to increased susceptibility to type 2 diabetes. METHODS: Non-diabetic human islets and INS 832/13 beta cells cultured under diabetogenic conditions (i.e. with specific cytokines or under glucolipotoxic [GLT] conditions) were evaluated for changes to PAK1 signalling. Combined effects of PAK1 deficiency with GLT stress were assessed using classic knockout (Pak1 (-/-) ) mice fed a 45% energy from fat/palmitate-based, 'western' diet (WD). INS 832/13 cells overexpressing or depleted of PAK1 were also assessed for apoptosis and signalling changes. RESULTS: Exposure of non-diabetic human islets to diabetic stressors attenuated PAK1 protein levels, concurrent with increased caspase 3 cleavage. WD-fed Pak1 knockout mice exhibited fasting hyperglycaemia and severe glucose intolerance. These mice also failed to mount an insulin secretory response following acute glucose challenge, coinciding with a 43% loss of beta cell mass when compared with WD-fed wild-type mice. Pak1 knockout mice had fewer total beta cells per islet, coincident with decreased beta cell proliferation. In INS 832/13 beta cells, PAK1 deficiency combined with GLT exposure heightened beta cell death relative to either condition alone; PAK1 deficiency resulted in decreased extracellular signal-related kinase (ERK) and B cell lymphoma 2 (Bcl2) phosphorylation levels. Conversely, PAK1 overexpression prevented GLT-induced cell death. CONCLUSIONS/INTERPRETATION: These findings suggest that PAK1 deficiency may underlie an increased diabetic susceptibility. Discovery of ways to remediate glycaemic dysregulation via altering PAK1 or its downstream effectors offers promising opportunities for disease intervention.

Gene targets of mouse miR-709: regulation of distinct pools.

MicroRNA (miRNA) are short non-coding RNA molecules that regulate multiple cellular processes, including development, cell differentiation, proliferation and death. Nevertheless, little is known on whether miRNA control the same gene networks in different tissues. miR-709 is an abundant miRNA expressed ubiquitously. Through transcriptome analysis, we have identified targets of miR-709 in hepatocytes. miR-709 represses genes implicated in cytoskeleton organization, extracellular matrix attachment, and fatty acid metabolism. Remarkably, none of the previously identified targets in non-hepatic tissues are silenced by miR-709 in hepatocytes, even though several of these genes are abundantly expressed in liver. In addition, miR-709 is upregulated in hepatocellular carcinoma, suggesting it participates in the genetic reprogramming that takes place during cell division, when cytoskeleton remodeling requires substantial changes in gene expression. In summary, the present study shows that miR-709 does not repress the same pool of genes in separate cell types. These results underscore the need for validating gene targets in every tissue a miRNA is expressed.

Sterol regulatory element-binding protein-1 (SREBP-1) is required to regulate glycogen synthesis and gluconeogenic gene expression in mouse liver.

Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor that regulates genes in the de novo lipogenesis and glycolysis pathways. The levels of SREBP-1 are significantly elevated in obese patients and in animal models of obesity and type 2 diabetes, and a vast number of studies have implicated this transcription factor as a contributor to hepatic lipid accumulation and insulin resistance. However, its role in regulating carbohydrate metabolism is poorly understood. Here we have addressed whether SREBP-1 is needed for regulating glucose homeostasis. Using RNAi and a new generation of adenoviral vector, we have silenced hepatic SREBP-1 in normal and obese mice. In normal animals, SREBP-1 deficiency increased Pck1 and reduced glycogen deposition during fed conditions, providing evidence that SREBP-1 is necessary to regulate carbohydrate metabolism during the fed state. Knocking SREBP-1 down in db/db mice resulted in a significant reduction in triglyceride accumulation, as anticipated. However, mice remained hyperglycemic, which was associated with up-regulation of gluconeogenesis gene expression as well as decreased glycolysis and glycogen synthesis gene expression. Furthermore, glycogen synthase activity and glycogen accumulation were significantly reduced. In conclusion, silencing both isoforms of SREBP-1 leads to significant changes in carbohydrate metabolism and does not improve insulin resistance despite reducing steatosis in an animal model of obesity and type 2 diabetes.

Vector and helper genome rearrangements occur during production of helper-dependent adenoviral vectors.

Helper-dependent adenoviral vectors (HD Ad) hold extreme promise for gene therapy of human diseases. All viral genes are deleted in HD Ad vectors, and therefore, the presence of a helper virus is required for their production. Current methods to minimize helper contamination in large-scale preparations rely on the use of the Cre/loxP system. The inclusion of loxP sites flanking the packaging signal results in its excision in the presence of Cre recombinase, preventing helper genome encapsidation. It is well established that the level of Cre recombinase activity is important in determining the degree of helper contamination. However, there is little information on other mechanisms that could also play an important role. We have generated several HD Ad vectors containing a rapalog-inducible system to regulate transgene expression, or LacZ under the control of the elongation factor 1 α promoter. Large-scale production of these vectors resulted in abundant helper contamination. Viral DNA analysis revealed the presence of rearrangements between vector and helper genomes. The rearrangements involved a helper DNA molecule with a fragment of the left arm of the HD Ad vector, including its ITR, packaging signal, and some stuffer sequence. Overall, our data suggest that helper DNA molecules that accumulate after Cre recombinase activity are prone to rearrangements, resulting in helper genomes that have incorporated a packaging signal from the vector. Helper particles with rearranged genomes have a growth advantage. This study identifies a novel mechanism leading to helper contamination during helper-dependent adenoviral vector production.

Anti-angiogenic gene therapy for metastatic renal cell carcinoma produces tumor growth suppression in an athymic nude mouse model.

PURPOSE: We investigated the anti-angiogenic and antitumor properties of 2 adenoviral vectors expressing the endostatin-angiostatin fusion protein Ad-EndoAngio and the soluble, endothelium specific tyrosine kinase receptor Ad-Tie2 in a mouse renal cell carcinoma xenograft model. MATERIALS AND METHODS: A total of 29 bilateral subcutaneous renal cell carcinomas were induced in athymic nude mice. On days 2 and 10 following tumor establishment the mice were intratumorally injected with an adenoviral vector in the right flank only. Seven treatment groups were randomly assigned, including the control group of 7 mice, the Ad-GFP control group of 7, the Ad-Tie2 group of 9, the Ad-EndoAngio group of 8, the Ad-GFP plus Ad-Tie2 group of 7, the Ad-GFP plus Ad-EndoAngio group of 9 and the Ad-EndoAngio plus Ad-Tie2 group of 8. Tumor volume was measured biweekly for 60 days. Additionally, each treatment group was administered fluorescent rhodamine conjugated bovine serum albumin dye for vascular imaging. After establishing skin windows overlying the tumors dual photon optical imaging was used to qualitatively assess the tumor vasculature. RESULTS: Tumors treated with Ad-EndoAngio, Ad-GFP plus Ad-EndoAngio and Ad-EndoAngio plus Ad-Tie2 demonstrated 82%, 83% and 87% growth reduction, respectively, compared to controls (p <0.001). Furthermore, in vivo imaging revealed a decrease in the number of blood vessels, lumen diameter and flow velocity in these treatment groups. CONCLUSIONS: Adenoviral vectors expressing endostatin-angiostatin fusion protein have effective anti-angiogenic action against human renal cell carcinoma cells as well as potential as a novel treatment for metastatic renal cell carcinoma.

Tumor-specific gene therapy for uterine cervical cancer using MN/CA9-directed replication-competent adenovirus.

Although gene therapies using tissue-specific promoters have been reported to be a promising tool for treating cancers, few studies have explored this possibility for uterine cervical cancer. MN/CA9 is a transmembrane glycoprotein that was first identified in the human cervical carcinoma cell line, HeLa. Since MN/CA9 protein is highly expressed in uterine cervical cancer tissues, but not in normal cervix, we constructed a tumor-specific replication-competent adenoviral vector utilizing MN/CA9 promoter (Ad-MN/CA9-E1a), which can replicate only in MN/CA9-expressing cells. Infection of Ad-MN/CA9-E1a to MN/CA9-positive uterine cervical cancer cells (HeLa, C-33 A and SiHa) resulted in much stronger Ad5 E1a protein expressions compared with MN/CA9-negative cells (SK-RC-29), suggesting a tissue-specific replication of this recombinant adenovirus. In vitro cytotoxicity assay revealed that the growth of MN/CA9-positive cells was significantly inhibited with 0.01-1 MOI of Ad-MN/CA9-E1a, but the growth of MN/CA9-negative cells (SK-RC-29) could only be inhibited by as many as 100 MOI. Intratumoral injection of Ad-MN/CA9-E1a effectively induced growth delay of HeLa tumors in nude mice. These results suggest that a novel replication-competent adenoviral vector mediated by MN/CA9 promoter, Ad-MN/CA9-E1a, can selectively replicate in MN/CA9-expressing tumors with cytotoxic effects and may be utilized for the treatment of uterine cervical cancer.