Targeting Base Excision Repair in Cancer: NQO1-Bioactivatable Drugs Improve Tumor Selectivity and Reduce Treatment Toxicity Through Radiosensitization of Human Cancer.

Ionizing radiation (IR) creates lethal DNA damage that can effectively kill tumor cells. However, the high dose required for a therapeutic outcome also damages healthy tissue. Thus, a therapeutic strategy with predictive biomarkers to enhance the beneficial effects of IR allowing a dose reduction without losing efficacy is highly desirable. NAD(P)H:quinone oxidoreductase 1 (NQO1) is overexpressed in the majority of recalcitrant solid tumors in comparison with normal tissue. Studies have shown that NQO1 can bioactivate certain quinone molecules (e.g., ortho-naphthoquinone and ß-lapachone) to induce a futile redox cycle leading to the formation of oxidative DNA damage, hyperactivation of poly(ADP-ribose) polymerase 1 (PARP1), and catastrophic depletion of NAD+ and ATP, which culminates in cellular lethality via NAD+-Keresis. However, NQO1-bioactivatable drugs induce methemoglobinemia and hemolytic anemia at high doses. To circumvent this, NQO1-bioactivatable agents have been shown to synergize with PARP1 inhibitors, pyrimidine radiosensitizers, and IR. This therapeutic strategy allows for a reduction in the dose of the combined agents to decrease unwanted side effects by increasing tumor selectivity. In this review, we discuss the mechanisms of radiosensitization between NQO1-bioactivatable drugs and IR with a focus on the involvement of base excision repair (BER). This combination therapeutic strategy presents a unique tumor-selective and minimally toxic approach for targeting solid tumors that overexpress NQO1.

Therapeutic Strategies and Biomarkers to Modulate PARP Activity for Targeted Cancer Therapy.

Poly-(ADP-ribose) polymerase 1 (PARP1) is commonly known for its vital role in DNA damage response and repair. However, its enzymatic activity has been linked to a plethora of physiological and pathophysiological transactions ranging from cellular proliferation, survival and death. For instance, malignancies with BRCA1/2 mutations heavily rely on PARP activity for survival. Thus, the use of PARP inhibitors is a well-established intervention in these types of tumors. However, recent studies indicate that the therapeutic potential of attenuating PARP1 activity in recalcitrant tumors, especially where PARP1 is aberrantly overexpressed and hyperactivated, may extend its therapeutic utility in wider cancer types beyond BRCA-deficiency. Here, we discuss treatment strategies to expand the tumor-selective therapeutic application of PARP inhibitors and novel approaches with predictive biomarkers to perturb NAD+ levels and hyperPARylation that inactivate PARP in recalcitrant tumors. We also provide an overview of genetic alterations that transform non-BRCA mutant cancers to a state of "BRCAness" as potential biomarkers for synthetic lethality with PARP inhibitors. Finally, we discuss a paradigm shift for the use of novel PARP inhibitors outside of cancer treatment, where it has the potential to rescue normal cells from severe oxidative damage during ischemia-reperfusion injury induced by surgery and radiotherapy.

The archaeal Dps nanocage targets kidney proximal tubules via glomerular filtration.

Nature exploits cage-like proteins for a variety of biological purposes, from molecular packaging and cargo delivery to catalysis. These cage-like proteins are of immense importance in nanomedicine due to their propensity to self-assemble from simple identical building blocks to highly ordered architecture and the design flexibility afforded by protein engineering. However, delivery of protein nanocages to the renal tubules remains a major challenge because of the glomerular filtration barrier, which effectively excludes conventional size nanocages. Here, we show that DNA-binding protein from starved cells (Dps) - the extremely small archaeal antioxidant nanocage - is able to cross the glomerular filtration barrier and is endocytosed by the renal proximal tubules. Using a model of endotoxemia, we present an example of the way in which proximal tubule-selective Dps nanocages can limit the degree of endotoxin-induced kidney injury. This was accomplished by amplifying the endogenous antioxidant property of Dps with addition of a dinuclear manganese cluster. Dps is the first-in-class protein cage nanoparticle that can be targeted to renal proximal tubules through glomerular filtration. In addition to its therapeutic potential, chemical and genetic engineering of Dps will offer a nanoplatform to advance our understanding of the physiology and pathophysiology of glomerular filtration and tubular endocytosis.

Improving the Transduction of Bone Marrow-Derived Cells with an Integrase-Defective Lentiviral Vector.

In lentiviral vector (LV) applications where transient transgene expression is sufficient, integrase-defective lentiviral vectors (IDLVs) are beneficial for reducing the potential for off-target effects associated with insertional mutagenesis. It was previously demonstrated that human RPE65 mRNA expression from an integrating lentiviral vector (ILV) induces endogenous Rpe65 and Cralbp mRNA expression in murine bone marrow-derived cells (BMDCs), initiating programming of the cells to retinal pigment epithelium (RPE)-like cells. These cells regenerate RPE in retinal degeneration models when injected systemically. As transient expression of RPE65 is sufficient to activate endogenous RPE-associated genes for programming BMDCs, use of an ILV is an unnecessary risk. In this study, an IDLV expressing RPE65 (IDLV3-RPE65) was generated. Transduction with IDLV3-RPE65 is less efficient than the integrating vector (ILV3-RPE65). Therefore, IDLV3-RPE65 transduction was enhanced with a combination of preloading 20 × -concentrated viral supernatant on RetroNectin at a multiplicity of infection of 50 and transduction of BMDCs by low-speed centrifugation. RPE65 mRNA levels increased from ∼12-fold to ∼25-fold (p < 0.05) after modification of the IDLV3-RPE65 transduction protocol, achieving expression similar to the ∼27-fold (p < 0.05) increase observed with ILV3-RPE65. Additionally, the study shows that the same preparation of RetroNectin can be used to coat up to three wells with no reduction in transduction. Critically, IDLV3-RPE65 transduction initiates endogenous Rpe65 mRNA expression in murine BMDCs and Cralbp/CRALBP mRNA in both murine and human BMDCs, similar to expression observed in ILV3-RPE65-transduced cells. Systemic administration of ILV3-RPE65 or IDLV3-RPE65 programmed BMDCs in a mouse model of retinal degeneration is sufficient to retain visual function and reduce retinal degeneration compared to mice receiving no treatment or naïve BMDC. It is concluded that IDLV3-RPE65 is appropriate for programming BMDCs to RPE-like cells.

Endotoxin Preconditioning Reprograms S1 Tubules and Macrophages to Protect the Kidney.

Preconditioning with a low dose of endotoxin confers unparalleled protection against otherwise lethal models of sepsis. The mechanisms of preconditioning have been investigated extensively in isolated immune cells such as macrophages. However, the role of tissue in mediating the protective response generated by preconditioning remains unknown. Here, using the kidney as a model organ, we investigated cell type-specific responses to preconditioning. Compared with preadministration of vehicle, endotoxin preconditioning in the cecal ligation and puncture mouse model of sepsis led to significantly enhanced survival and reduced bacterial load in several organs. Furthermore, endotoxin preconditioning reduced serum levels of proinflammatory cytokines, upregulated molecular pathways involved in phagocytosis, and prevented the renal function decline and injury induced in mice by a toxic dose of endotoxin. The protective phenotype involved the clustering of macrophages around S1 segments of proximal tubules, and full renal protection required both macrophages and renal tubular cells. Using unbiased S1 transcriptomic and tissue metabolomic approaches, we identified multiple protective molecules that were operative in preconditioned animals, including molecules involved in antibacterial defense, redox balance, and tissue healing. We conclude that preconditioning reprograms macrophages and tubules to generate a protective environment, in which tissue health is preserved and immunity is controlled yet effective. Endotoxin preconditioning can thus be used as a discovery platform, and understanding the role and participation of both tissue and macrophages will help refine targeted therapies for sepsis.

Systemic Injection of RPE65-Programmed Bone Marrow-Derived Cells Prevents Progression of Chronic Retinal Degeneration.

Bone marrow stem and progenitor cells can differentiate into a range of non-hematopoietic cell types, including retinal pigment epithelium (RPE)-like cells. In this study, we programmed bone marrow-derived cells (BMDCs) ex vivo by inserting a stable RPE65 transgene using a lentiviral vector. We tested the efficacy of systemically administered RPE65-programmed BMDCs to prevent visual loss in the superoxide dismutase 2 knockdown (Sod2 KD) mouse model of age-related macular degeneration. Here, we present evidence that these RPE65-programmed BMDCs are recruited to the subretinal space, where they repopulate the RPE layer, preserve the photoreceptor layer, retain the thickness of the neural retina, reduce lipofuscin granule formation, and suppress microgliosis. Importantly, electroretinography and optokinetic response tests confirmed that visual function was significantly improved. Mice treated with non-modified BMDCs or BMDCs pre-programmed with LacZ did not exhibit significant improvement in visual deficit. RPE65-BMDC administration was most effective in early disease, when visual function and retinal morphology returned to near normal, and less effective in late-stage disease. This experimental paradigm offers a minimally invasive cellular therapy that can be given systemically overcoming the need for invasive ocular surgery and offering the potential to arrest progression in early AMD and other RPE-based diseases.

A Non-Canonical Role for ß-Secretase in the Retina.

It has long been established that ß-Secretase (BACE) plays a critical role in the formation of amyloid plaques in Alzheimer's Disease patients, but it is only recently that the importance of ß-secretases in retinal pathophysiology has been recognized. BACE expression is elevated in response to stress, and downregulation results in lysosomal abnormalities and mitochondrial changes. Inhibition of BACE can lead to reduced retinal function, retinal thinning, lipofuscin accumulation and vascular dysfunction in mice. Furthermore, BACE inhibition accelerates choroidal neovascularization (CNV) in mice. We propose that BACE plays an important role in retinal homeostasis and that BACE upregulation in response to stress is a protective measure.

Gestational diabetes induces alterations in the function of neonatal endothelial colony-forming cells.

BACKGROUND: Children born to mothers with gestational diabetes mellitus (GDM) experience increased risk of developing hypertension, type 2 diabetes mellitus, and obesity. Disrupted function of endothelial colony-forming cells (ECFCs) may contribute to this enhanced risk. The goal of this study was to determine whether cord blood ECFCs from GDM pregnancies exhibit altered functionality. METHODS: ECFCs isolated from the cord blood of control and GDM pregnancies were assessed for proliferation, senescence, and Matrigel network formation. The requirement for p38MAPK in hyperglycemia-induced senescence was determined using inhibition and overexpression studies. RESULTS: GDM-exposed ECFCs were more proliferative than control ECFCs. However, GDM-exposed ECFCs exhibited decreased network-forming ability in Matrigel. Aging of ECFCs by serial passaging led to increased senescence and reduced proliferation of GDM-exposed ECFCs. ECFCs from GDM pregnancies were resistant to hyperglycemia-induced senescence compared with those from controls. In response to hyperglycemia, control ECFCs activated p38MAPK, which was required for hyperglycemia-induced senescence. In contrast, GDM-exposed ECFCs showed no change in p38MAPK activation under equivalent conditions. CONCLUSION: Intrauterine exposure of ECFCs to GDM induces unique phenotypic alterations. The resistance of GDM-exposed ECFCs to hyperglycemia-induced senescence and decreased p38MAPK activation suggest that these progenitor cells have undergone changes that induce tolerance to a hyperglycemic environment.

Pronounced interferon-alpha production from plasmacytoid dendritic cells in patients with Behçet's disease following CpG D ODN stimulation.

OBJECTIVE: Several lines of evidence point to a polarized T-helper-1 (Th1) immune response in Behçet's disease (BD). Interferon (IFN)-alpha which has an ability to promote strong Th1 type immune response has been shown to increase in patients with BD. In order to clarify if plasmacytoid dendritic cells (pDCs) abnormally respond to a stimulus in patients with BD, we investigated the levels of intracellular IFN-alpha and beta in pDCs with or without CpG D ODN stimulation. METHODS: The study population consisted of 8 patients with clinically active BD, 8 ankylosing spondilitis (AS) patients having active disease and 11 healthy volunteers. pDC subsets in peripheral blood mononuclear cells (PBMCs) cultures were analysed by flow cytometry. RESULTS: The percentage of IFN-alpha+ pDCs in unstimulated PBMCs cultures from patients BD was significantly higher (p=0.036) than in AS and HC. But this difference disappeared in stimulated PBMCs cultures (p=0.167). The mean fluorescence intensity (MFI) of IFN-alpha+ pDCs in stimulated PBMCs cultures of BD patients was significantly higher than those from patients with AS and HC. The percentage of IFN-beta+ pDCs in unstimulated PBMCs cultures from patients with BD and AS was significantly higher (p=0.004) than in HC. But this difference was not significant in stimulated PBMCs cultures (p=0.694). When compared to healthy subjects, the MFI of IFN-beta + pDCs in unstimulated and stimulated PBMCs cultures from patients with BD and AS was not different (p=0.287, p=0.152, respectively). In patients with BD, the percentage and MFI of IFN-alpha+ pDCs were higher (p=0.012 for all) in stimulated PBMCs cultures as compared to unstimulated ones. CONCLUSION: We suggest that increased frequency of IFN-alpha+ pDC in BD patients and the higher sensitiveness of these cells to CpG D ODN stimulus contribute to high serum IFN-alpha levels found in these patients which eventually resulted in Th1 type immune response.

The role of HLA-DRB1 shared epitope alleles in predicting short-term response to leflunomide in rheumatoid arthritis.

OBJECTIVES: To investigate the role of shared epitope (SE) alleles in the short-term clinical response to leflunomide for the treatment of active RA. METHODS: In an open-label, multi-centre study of 16-weeks duration, 93 patients (82% female) fulfilling ARA 1987 RA criteria were treated with leflunomide (100 mg loading dose for 3 days, then 20 mg/day as the maintenance dose). The primary efficacy criterion was the response status according to the European League Against Rheumatism (EULAR) response criteria using Disease Activity Score-28 (DAS28) activity measure. SE determinations have been undertaken by polymerase chain reaction and sequence-specific oligonucleotide genotyping methods. RESULTS: The mean (s.d.) Disease Activity Score-28 (DAS28) was 5.1 (1.3) before the treatment, which was significantly decreased after 16 weeks [3.0 (1.1), P < 0.001]. According to the EULAR response criteria, 55 patients (59.1%) were classified as good responders. SE was positive in 51 (54.8%) of the patients, with 13 (13.9%) having SE homozygosity or carrying any two SE alleles. Among SE-positive patients, 68.6% (35/51) were good responders, compared with 47.6% (20/42) in SE negatives (P = 0.04). No difference was present according to SE hetero- or homozygosity (68.4 vs 69.2%). RF was also present significantly more frequently in the SE-positive group compared with negatives (78.4 vs 57.1%, P = 0.03). However, no significant difference was observed in the prevalence of RF positivity in patients with a good clinical response (72.7 vs 63.2%, P = 0.32). CONCLUSIONS: The results suggest that HLA-DRB1 SE presence may favourably affect the outcome of leflunomide monotherapy in an unselected group of RA patients with an active disease and naive to leflunomide.

Synovial lymphoid neogenetic factors in Behçet's synovitis: do they play a role in self-limiting and subacute course of arthritis?

OBJECTIVE: Lymphoid neogenesis seems to play an important role in the persistence of chronic inflammation and has been shown in various disorders characterized by chronic inflammation including rheumatoid arthritis. Arthritis of Behçet's disease is characterized by non-erosive arthritis in which the disease course is considered to be subacute and self limiting. However, molecular mechanisms underlying those features of Behçet's arthritis have not been defined yet. In order to determine the contribution of lymphoid neogenesis in the disease course of Behçet's arthritis, we investigated the synovial fluid (SF) levels of CXCL 12, CXCL 13, CCL 21 homeostatic chemokines and the percentage of SF naive lymphocytes expressing their receptors such as CXCR4+ and CCR7+. We further measured the SF TGF-Beta and INF-Beta levels which are known to contribute lymphoid neogenesis via leading persistent expression of CXCR4 on T cells and inhibiting T cell apoptosis, respectively. METHODS: Fifty-one [15 BD, 17 RA, and 19 osteoarthritis (OA)] patients with at least one- sided knee arthritis were enrolled in the study. Patients with BD constituted the study group, and RA, OA patients were used as positive and negative control groups, respectively. The SF levels of CXCL 12, CXCL 13, CCL 21, TGF-Beta and INF-Beta were measured by ELISA. CXCR4, CCR7 chemokine receptors on SF lymphocytes were tested by Flow- cytometry. Kruskal-Wallis test and Mann-Whitney U test were used for statistical analysis where appropriate. RESULTS: Synovial fluid CCL 21 levels were found to be increased in RA patients as compared to BD and OA patients (p = 0.003, and p = 0.013, respectively). No significant difference was detected between BD and OA patients with respect to CCL 21 levels. Both CXCL 12 and CXCL 13 SF levels were found to be higher in RA and BD patients as compared to OA patients (CXCL-12; p = 0.012, and p = 0.024), (CXCL 13; p < 0.001, and p = 0.007). However, no difference with regard to SF levels of both CXCL 12 and CXCL 13 were found between RA and BD patients. Percentages of both CD3+CXCR4+ lymphocytes and CD3+CCR7+ lymphocytes in the SF of RA patients were detected to be increased as compared to those of BD and OA patients (CD3+CXCR4+; p = 0.019, p = 0.048, respectively), (CD3+CCR7+; p = 0.023, p = 0.001, respectively). However, no differences with respect to the percentages of SF lymphocytes expressing CD3+CXCR4+ or CD3+CCR7+ were found between BD and OA patients. Both TGF-Beta and INF-Beta SF levels were found to be higher in RA patients as compared to BD and OA patients (TGF-Beta; p = 0.041, and p = 0.003), (INF-Beta; p = 0.012, and p = 0.016). However, no differences with regard to SF levels of both TGF-Beta and INF-Beta were found between BD and OA patients. CONCLUSION: Considering the subacute, self limiting and non-erosive course of arthritis observed in BD, our finding of detection of lower levels of CCL21 and TGF-Beta1 and IFN-Beta in BD patients, seems to prevent the development of LN and chronic inflammation in Behçet's synovitis. In support of this view, percentages of SF naïve T lymphocytes were found to be lower in BD patients comparing with those of the RA. Absence of tertiary lymphoid structures in BD patients, may explain the spontaneous resolution of Behçet's arthritis in most of the cases.

Dendritic cell subsets and type I interferon system in Behçet's disease: does functional abnormality in plasmacytoid dendritic cells contribute to Th1 polarization?

OBJECTIVE: Several lines of evidence point to a polarized T-helper-1 (Th1) immune response in Behçet's disease (BD). However, it is not yet clear which factors are involved in the proposed Th1 mediated pathogenesis of BD. Dendritic cells (DCs) are antigen presenting cells which play a crucial role in the polarization of immune response. No previous study has examined the possible role of DCs in the pathogenesis of BD. We conducted both quantitative and functional analysis of the peripheral blood DC subsets in BD patients with different clinical presentations. METHODS: Thirty-eight patients with BD, 12 healthy controls (HC), and 12 patients with undifferentiated spondylarthritis (uSpA) were enrolled in the study. Peripheral blood DC subsets were analysed by flow cytometry and were further characterized for maturation with CCR7. Serum levels of interferon (IFN)-alpha and IFN-b were measured by ELISA. RESULTS: BD patients had a decreased percentage of plasmacytoid DCs (pDCs) compared to HC (p = 0.036). IFN-alpha levels were found to be increased in BD patients as compared to HC and uSPA (p < 0.001, p = 0.005, respectively). BD patients had decreased levels of IFN-Beta as compared to HC and uSpA (p = 0.013, p = 0.004, respectively). No difference was found between HC and patients with uSpA regarding IFN-Beta levels. Subgroup analysis of BD patients disclosed normalization of percentage of pDCs and the level of IFN-Beta in patients receiving IFN-alpha-2b. CONCLUSION: We suggest abnormalities in pDCs and type I IFNs appear to be a master switch leading to the pathogenicity in BD by directing immune response towards Th1.

Serum MMP-2 and MMP-9 in patients with Behçet's disease: do their higher levels correlate to vasculo-Behçet's disease associated with aneurysm formation?

OBJECTIVES: Basic and clinical studies have revealed a strong correlation between matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, and the formation of abdominal aortic aneurysms. In addition, previous studies have clearly shown that MMP-2 and MMP-9 play an important role in the pathogenesis of vasculitis characterized by aneurysm formation such as Kawasaki disease, temporal arteritis and Takayasu arteritis. Depending on those findings, we hypothesized that circulating MMP-2 and MMP-9 could be useful markers to demonstrate vascular aneurysmatic involvement in patients with Behçet's disease (BD). METHODS: Fifty-eight patients with BD, and 20 healthy controls were enrolled in the study. We assessed the disease activity of patients according to the Leeds activity score system. We compared the Leeds activity scores of patients with their serum levels of MMP2 and MMP-9. Patients with BD were categorized as active (total activity score > or = 5) or inactive (total activity score < 5). Patients were further categorized with respect to their extent of involvement as muco-cutaneous or systemic. Patients with systemic involvement were subdivided into ocular or vascular involvement. Patients with vascular involvement were subgrouped as thrombotic or aneurysmatic involvement. The levels of MMP-2 and MMP-9 were measured by ELISA. RESULTS: Serum MMP-9 but not MMP-2 levels were significantly higher both in patients with active and inactive disease as compared to healthy controls (p = 0.008 and 0.013 respectively). We found positive correlation between Leeds activity score and serum MMP-2 levels in patients with vascular involvement (p = 0.035 and r = 0.485), and serum MMP-9 levels in active BD patients (p = 0.003 and r = 0.599). The serum levels of MMP-2 and MMP-9 in patients with systemic involvement were higher than those of healthy controls but not patients with mucocutaneous involvement (p = 0.046 and 0.002 respectively). The serum levels of MMP-2 in patients with vascular involvement were found to be higher than those of healthy controls and patients with mucocutaneous involvement (p = 0.001 and 0.003, respectively) but not different in those with ocular involvement. The serum levels of MMP-9 in patients with vascular involvement were found to be higher than those of healthy controls and ocular disease (p = 0.001 and 0.033 respectively) but not different in those with mucocutaneous involvement. The serum levels of MMP-2 in patients with aneurysmatic involvement were found to be higher than those of healthy controls, mucocutaneous and ocular involvement (p = 0.004, 0.008 and 0.004 respectively). The serum levels of MMP-2 in patients with thrombotic involvement were found to be higher than those of healthy controls and mucocutaneous (p = 0.018 and 0.033 respectively) but not ocular involvement. The serum levels of MMP-9 in patients with aneurysmatic involvement were found to be higher than those of healthy controls, mucocutaneous and ocular involvement (p = 0.001, 0.048 and 0.007 respectively). The serum levels of MMP-9 in patients with thrombotic involvement were found to be higher than those of healthy controls but not mucocutaneous and ocular involvement (p = 0.046). CONCLUSIONS: We concluded that serum MMP-2 and MMP-9 levels can be used as an activity indicator for vasculo-Behçet's or active Behçet's patients, respectively. But they can not be used as a marker reflecting the systemic involvement of patients with BD. The systemic expressions of MMP-2 and MMP-9 were strongly associated with vasculo-Behçet's disease, particularly aneurysmatic involvement, suggesting their pathogenetic roles in vasculo-Behçet's disease complicated with aneurysm formation.

Peripheral insulin resistance in patients with Behçet's disease.

In this study, we examined peripheral insulin resistance in patients with Behçet's disease (BD) characterized by chronic inflammation and endothelial dysfunction. Fourteen patients with BD and 15 healthy controls were recruited to the study. Insulin resistance was investigated by the hyperinsulinaemic-euglycaemic glucose clamp technique. BD patients displayed an enhanced rate of insulin resistance compared to healthy controls (P = 0.014). The insulin sensitivity (M), measured as the glucose utilization rate under steady-state conditions of euglycaemia, was significantly decreased (P = 0.001) in BD patients compared to the controls (4.09 +/- 0.16 vs. 5.60 +/- 0.27 mg/kg/min). The C-reactive protein (CRP) level, but not the erythrocyte sedimentation rate (ESR), was significantly related to the presence of insulin resistance (CRP: r(s) = 0.589, P = 0.27; ESR: r(s) = 0444, P = 0112), whereas no relationship was found between the M-value and ESR or CRP. We conclude that patients with BD exhibit peripheral insulin resistance; this could be explained as the diverse consequences of inflammation and endothelial dysfunction in BD.