Integration of single-cell transcriptomes and biological function reveals distinct behavioral patterns in bone marrow endothelium.

Heterogeneity of endothelial cell (EC) populations reflects their diverse functions in maintaining tissue's homeostasis. However, their phenotypic, molecular, and functional properties are not entirely mapped. We use the Tie2-CreERT2;Rosa26-tdTomato reporter mouse to trace, profile, and cultivate primary ECs from different organs. As paradigm platform, we use this strategy to study bone marrow endothelial cells (BMECs). Single-cell mRNA sequencing of primary BMECs reveals that their diversity and native molecular signatures is transitorily preserved in an ex vivo culture that conserves key cell-to-cell microenvironment interactions. Macrophages sustain BMEC cellular diversity and expansion and preserve sinusoidal-like BMECs ex vivo. Endomucin expression discriminates BMECs in populations exhibiting mutually exclusive properties and distinct sinusoidal/arterial and tip/stalk signatures. In contrast to arterial-like, sinusoidal-like BMECs are short-lived, form 2D-networks, contribute to in vivo angiogenesis, and support hematopoietic stem/progenitor cells in vitro. This platform can be extended to other organs' ECs to decode mechanistic information and explore therapeutics.

COVID-19 vaccination elicits an evolving, cross-reactive antibody response to epitopes conserved with endemic coronavirus spike proteins.

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Many vaccinated subjects are previously naive to SARS-CoV-2; however, almost all have previously encountered other coronaviruses (CoVs), and the role of this immunity in shaping the vaccine response remains uncharacterized. Here, we use longitudinal samples and highly multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes, in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes shows a delayed but progressive increase following vaccination, we observe distinct kinetics for the endemic CoV homologs at conserved sites in Spike S2: these become detectable sooner and decay at later time points. Using homolog-specific antibody depletion and alanine-substitution experiments, we show that these distinct trajectories reflect an evolving cross-reactive response that can distinguish rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

Pre-clinical data supporting immunotherapy for HIV using CMV-HIV-specific CAR T cells with CMV vaccine.

T cells engineered to express HIV-specific chimeric antigen receptors (CARs) represent a promising strategy to clear HIV-infected cells, but to date have not achieved clinical benefits. A likely hurdle is the limited T cell activation and persistence when HIV antigenemia is low, particularly during antiretroviral therapy (ART). To overcome this issue, we propose to use a cytomegalovirus (CMV) vaccine to stimulate CMV-specific T cells that express CARs directed against the HIV-1 envelope protein gp120. In this study, we use a GMP-compliant platform to engineer CMV-specific T cells to express a second-generation CAR derived from the N6 broadly neutralizing antibody, one of the broadest anti-gp120 neutralizing antibodies. These CMV-HIV CAR T cells exhibit dual effector functions upon in vitro stimulation through their endogenous CMV-specific T cell receptors or the introduced CARs. Using a humanized HIV mouse model, we show that CMV vaccination during ART accelerates CMV-HIV CAR T cell expansion in the peripheral blood and that higher numbers of CMV-HIV CAR T cells were associated with a better control of HIV viral load and fewer HIV antigen p24+ cells in the bone marrow upon ART interruption. Collectively, these data support the clinical development of CMV-HIV CAR T cells in combination with a CMV vaccine in HIV-infected individuals.

COVID-19 vaccination recruits and matures cross-reactive antibodies to conserved epitopes in endemic coronavirus Spike proteins.

The COVID-19 pandemic has triggered the first widespread vaccination campaign against a coronavirus. Most vaccinated subjects are naïve to SARS-CoV-2, however almost all have previously encountered other coronaviruses (CoVs) and the role of this immunity in shaping the vaccine response remains uncharacterized. Here we use longitudinal samples and highly-multiplexed serology to identify mRNA-1273 vaccine-induced antibody responses against a range of CoV Spike epitopes and in both phylogenetically conserved and non-conserved regions. Whereas reactivity to SARS-CoV-2 epitopes showed a delayed but progressive increase following vaccination, we observed distinct kinetics for the endemic CoV homologs at two conserved sites in Spike S2: these became detectable sooner, and decayed at later timepoints. Using homolog-specific depletion and alanine-substitution experiments, we show that these distinctly-evolving specificities result from cross-reactive antibodies as they mature against rare, polymorphic residues within these epitopes. Our results reveal mechanisms for the formation of antibodies with broad reactivity against CoVs.

Engineered extracellular vesicles directed to the spike protein inhibit SARS-CoV-2.

SARS-CoV-2 (CoV-2) viral infection results in COVID-19 disease, which has caused significant morbidity and mortality worldwide. A vaccine is crucial to curtail the spread of SARS-CoV-2, while therapeutics will be required to treat ongoing and reemerging infections of SARS-CoV-2 and COVID-19 disease. There are currently no commercially available effective anti-viral therapies for COVID-19, urging the development of novel modalities. Here, we describe a molecular therapy specifically targeted to neutralize SARS-CoV-2, which consists of extracellular vesicles (EVs) containing a novel fusion tetraspanin protein, CD63, embedded within an anti-CoV-2 nanobody. These anti-CoV-2-enriched EVs bind SARS-CoV-2 spike protein at the receptor-binding domain (RBD) site and can functionally neutralize SARS-CoV-2. This work demonstrates an innovative EV-targeting platform that can be employed to target and inhibit the early stages of SARS-CoV-2 infection.

Large-scale manufacturing and characterization of CMV-CD19CAR T cells.

BACKGROUND: Adoptive transfer of CD19-specific chimeric antigen receptor (CD19CAR) T cells can induce dramatic disease regression in patients with B cell malignancies. CD19CAR T cell therapy may be limited by insufficient engraftment and persistence, resulting in tumor relapse. We previously demonstrated a proof of principle that cytomegalovirus (CMV)-specific T cells can be isolated and enriched prior to CD19CAR transduction to produce CMV-CD19CAR T cells, and that these CMV-CD19CAR T cells can be expanded in vivo through CMV vaccination, resulting in better tumor control in a murine model. Here we developed a clinical platform for generating CMV-CD19CAR T cells. METHODS: Peripheral blood mononuclear cells (PBMCs) collected from CMV-seropositive healthy donors were stimulated with a good manufacturing practices-grade PepTivator overlapping CMVpp65 peptide pool and enriched for CMV-responsive interferon γ (IFNγ)+T cells using IFNγ Catchmatrix, within the CliniMACS Prodigy Cytokine Capture System (Miltenyi Biotec). Resulting CMV-specific T cells were transduced with a lentiviral vector encoding a second generation CD19R:CD28:ζ/EGFRt CAR and expanded with interleukin 2 (IL-2) and IL-15 for 15 days before characterization. RESULTS: CMV-specific T cells were enriched from 0.8%±0.5 of input PBMC to 76.3%±11.6 in nine full-scale qualification runs (absolute yield of 4.2±3.3×106 IFNγ+T cells from an input of 1×109 PBMCs). Average CD19CAR transduction efficiency of CMV-specific T cells was 27.0%±14.2 in the final products, which underwent rapid expansion, resulting in a total cell dose of 6.2±0.9 × 106 CD19CAR-tranduced T cells with CMV specificity (ie, functionally bispecific). CMV-CD19CAR T cells were polyclonal, expressed memory markers but had low expression of exhaustion markers, responded to both CD19 and CMVpp65 stimulation with rapid proliferation and exhibited antigen-specific effector functions against both CD19-expressing tumors and CMVpp65 antigen. The final products passed release criteria for clinical use. CONCLUSIONS: We demonstrated the feasibility of our large-scale platform for generating CMV-CD19CAR T cells for clinical application. We plan to initiate a clinical trial at City of Hope using CMV-CD19CAR T cells for patients with intermediate/high-grade B cell non-Hodgkin's lymphoma immediately after autologous hematopoietic cell transplantation followed by vaccination with a novel CMV vaccine based on Modified Vaccinia Ankara (Triplex) 28 days and 56 days post-T cell infusion.

The Earliest T-Precursors in the Mouse Embryo Are Susceptible to Leukemic Transformation.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in pediatric patients. About 10-15% of pediatric ALL belong to T-cell ALL (T-ALL), which is characterized by aggressive expansion of immature T-lymphoblasts and is categorized as high-risk leukemia. Leukemia initiating cells represent a reservoir that is responsible for the initiation and propagation of leukemia. Its perinatal origin has been suggested in some childhood acute B-lymphoblastic and myeloblastic leukemias. Therefore, we hypothesized that child T-ALL initiating cells also exist during the perinatal period. In this study, T-ALL potential of the hematopoietic precursors was found in the para-aortic splanchnopleura (P-Sp) region, but not in the extraembryonic yolk sac (YS) of the mouse embryo at embryonic day 9.5. We overexpressed the Notch intracellular domain (NICD) in the P-Sp and YS cells and transplanted them into lethally irradiated mice. NICD-overexpressing P-Sp cells rapidly developed T-ALL while YS cells failed to display leukemia propagation despite successful NICD induction. These results suggest a possible role of fetal-derived T-cell precursors as leukemia-initiating cells.

Therapeutic targeting of the E3 ubiquitin ligase SKP2 in T-ALL.

Timed degradation of the cyclin-dependent kinase inhibitor p27Kip1 by the E3 ubiquitin ligase F-box protein SKP2 is critical for T-cell progression into cell cycle, coordinating proliferation and differentiation processes. SKP2 expression is regulated by mitogenic stimuli and by Notch signaling, a key pathway in T-cell development and in T-cell acute lymphoblastic leukemia (T-ALL); however, it is not known whether SKP2 plays a role in the development of T-ALL. Here, we determined that SKP2 function is relevant for T-ALL leukemogenesis, whereas is dispensable for T-cell development. Targeted inhibition of SKP2 by genetic deletion or pharmacological blockade markedly inhibited proliferation of human T-ALL cells in vitro and antagonized disease in vivo in murine and xenograft leukemia models, with little effect on normal tissues. We also demonstrate a novel feed forward feedback loop by which Notch and IL-7 signaling cooperatively converge on SKP2 induction and cell cycle activation. These studies show that the Notch/SKP2/p27Kip1 pathway plays a unique role in T-ALL development and provide a proof-of-concept for the use of SKP2 as a new therapeutic target in T-cell acute lymphoblastic leukemia (T-ALL).

Strategies and limitations in app usage and human mobility.

Cognition has been found to constrain several aspects of human behaviour, such as the number of friends and the number of favourite places a person keeps stable over time. This limitation has been empirically defined in the physical and social spaces. But do people exhibit similar constraints in the digital space? We address this question through the analysis of pseudonymised mobility and mobile application (app) usage data of 400,000 individuals in a European country for six months. Despite the enormous heterogeneity of apps usage, we find that individuals exhibit a conserved capacity that limits the number of applications they regularly use. Moreover, we find that this capacity steadily decreases with age, as does the capacity in the physical space but with more complex dynamics. Even though people might have the same capacity, applications get added and removed over time. In this respect, we identify two profiles of individuals: app keepers and explorers, which differ in their stable (keepers) vs exploratory (explorers) behaviour regarding their use of mobile applications. Finally, we show that the capacity of applications predicts mobility capacity and vice-versa. By contrast, the behaviour of keepers and explorers may considerably vary across the two domains. Our empirical findings provide an intriguing picture linking human behaviour in the physical and digital worlds which bridges research studies from Computer Science, Social Physics and Computational Social Sciences.

Functional analysis of HOXA10 and HOXB4 in human medulloblastoma cell lines.

Medulloblastoma (MB) is a malignant childhood brain tumor which at molecular level is classified into at least four major subtypes: WNT, SHH, group C and group D differing in response to treatment. Previous studies have associated changes in expression levels and activation of certain HOX genes with MB development. In the present study, we investigate the role of HOX genes in two attributes acquired by tumor cells: migration and proliferation potential, as well as, in vivo tumorigenic potential. We analyzed UW402, UW473, DAOY and ONS-76 human pediatric MB cell lines and cerebellum primary cultures. Two-color microarray-based gene expression analysis was used to identify differentially expressed HOX genes. Among the various HOX genes significantly overexpressed in DAOY and ONS-76 cell lines compared to UW402 and UW473 cell lines, HOXA10 and HOXB4 were selected for further analysis. The expression levels of these HOX genes were validated by real-time PCR. A mouse model was used to study the effect of the HOXA10 and HOXB4 genes on the in vivo tumorigenic potential and the in vitro proliferative and migration potential of MB cell lines. Our results show that the inhibition of HOXA10 in DAOY cell line led to increased in vitro cell migration while in vitro cell proliferation or in vivo tumorigenic potential were unaffected. We also observed that induced expression of HOXB4 in the UW473 cell line significantly reduced in vitro cell proliferation and migration capability of UW473 cells with no effect on the in vivo tumorigenicity. This suggests that HOXA10 plays a role in migration events and the HOXB4 gene is involved in proliferation and migration processes of medulloblastoma cells, however, it appears that these genes are not essential for the tumorigenic process of these cells.

Ref-1/APE1 as a Transcriptional Regulator and Novel Therapeutic Target in Pediatric T-cell Leukemia.

The increasing characterization of childhood acute lymphoblastic leukemia (ALL) has led to the identification of multiple molecular targets but has yet to translate into more effective targeted therapies, particularly for high-risk, relapsed T-cell ALL. Searching for master regulators controlling multiple signaling pathways in T-ALL, we investigated the multifunctional protein redox factor-1 (Ref-1/APE1), which acts as a signaling "node" by exerting redox regulatory control of transcription factors important in leukemia. Leukemia patients' transcriptome databases showed increased expression in T-ALL of Ref-1 and other genes of the Ref-1/SET interactome. Validation studies demonstrated that Ref-1 is expressed in high-risk leukemia T cells, including in patient biopsies. Ref-1 redox function is active in leukemia T cells, regulating the Ref-1 target NF-κB, and inhibited by the redox-selective Ref-1 inhibitor E3330. Ref-1 expression is not regulated by Notch signaling, but is upregulated by glucocorticoid treatment. E3330 disrupted Ref-1 redox activity in functional studies and resulted in marked inhibition of leukemia cell viability, including T-ALL lines representing different genotypes and risk groups. Potent leukemia cell inhibition was seen in primary cells from ALL patients, relapsed and glucocorticoid-resistant T-ALL cells, and cells from a murine model of Notch-induced leukemia. Ref-1 redox inhibition triggered leukemia cell apoptosis and downregulation of survival genes regulated by Ref-1 targets. For the first time, this work identifies Ref-1 as a novel molecular effector in T-ALL and demonstrates that Ref-1 redox inhibition results in potent inhibition of leukemia T cells, including relapsed T-ALL. These data also support E3330 as a specific Ref-1 small-molecule inhibitor for leukemia. Mol Cancer Ther; 16(7); 1401-11. ©2017 AACR.

Individualized Breast Cancer Characterization through Single-Cell Analysis of Tumor and Adjacent Normal Cells.

There is a need to individualize assays for tumor molecular phenotyping, given variations in the differentiation status of tumor and normal tissues in different patients. To address this, we performed single-cell genomics of breast tumors and adjacent normal cells propagated for a short duration under growth conditions that enable epithelial reprogramming. Cells analyzed were either unselected for a specific subpopulation or phenotypically defined as undifferentiated and highly clonogenic ALDH+/CD49f+/EpCAM+ luminal progenitors, which express both basal cell and luminal cell-enriched genes. We analyzed 420 tumor cells and 284 adjacent normal cells for expression of 93 genes that included a PAM50-intrinsic subtype classifier and stemness-related genes. ALDH+/CD49f+/EpCAM+ tumor and normal cells clustered differently compared with unselected tumor and normal cells. PAM50 gene-set analyses of ALDH+/CD49f+/EpCAM+ populations efficiently identified major and minor clones of tumor cells, with the major clone resembling clinical parameters of the tumor. Similarly, a stemness-associated gene set identified clones with divergent stemness pathway activation within the same tumor. This refined expression profiling technique distinguished genes truly deregulated in cancer from genes that identify cellular precursors of tumors. Collectively, the assays presented here enable more precise identification of cancer-deregulated genes, allow for early identification of therapeutically targetable tumor cell subpopulations, and ultimately provide a refinement of precision therapeutics for cancer treatment. Cancer Res; 77(10); 2759-69. ©2017 AACR.

Cell Adhesion Molecule CD166 Drives Malignant Progression and Osteolytic Disease in Multiple Myeloma.

Multiple myeloma is incurable once osteolytic lesions have seeded at skeletal sites, but factors mediating this deadly pathogenic advance remain poorly understood. Here, we report evidence of a major role for the cell adhesion molecule CD166, which we discovered to be highly expressed in multiple myeloma cell lines and primary bone marrow cells from patients. CD166+ multiple myeloma cells homed more efficiently than CD166- cells to the bone marrow of engrafted immunodeficient NSG mice. CD166 silencing in multiple myeloma cells enabled longer survival, a smaller tumor burden, and less osteolytic lesions, as compared with mice bearing control cells. CD166 deficiency in multiple myeloma cell lines or CD138+ bone marrow cells from multiple myeloma patients compromised their ability to induce bone resorption in an ex vivo organ culture system. Furthermore, CD166 deficiency in multiple myeloma cells also reduced the formation of osteolytic disease in vivo after intratibial engraftment. Mechanistic investigation revealed that CD166 expression in multiple myeloma cells inhibited osteoblastogenesis of bone marrow-derived osteoblast progenitors by suppressing Runx2 gene expression. Conversely, CD166 expression in multiple myeloma cells promoted osteoclastogenesis by activating TRAF6-dependent signaling pathways in osteoclast progenitors. Overall, our results define CD166 as a pivotal director in multiple myeloma cell homing to the bone marrow and multiple myeloma progression, rationalizing its further study as a candidate therapeutic target for multiple myeloma treatment. Cancer Res; 76(23); 6901-10. ©2016 AACR.

Structural and functional characterization of endothelial microparticles released by cigarette smoke.

Circulating endothelial microparticles (EMPs) are emerging as biomarkers of chronic obstructive pulmonary disease (COPD) in individuals exposed to cigarette smoke (CS), but their mechanism of release and function remain unknown. We assessed biochemical and functional characteristics of EMPs and circulating microparticles (cMPs) released by CS. CS exposure was sufficient to increase microparticle levels in plasma of humans and mice, and in supernatants of primary human lung microvascular endothelial cells. CS-released EMPs contained predominantly exosomes that were significantly enriched in let-7d, miR-191; miR-126; and miR125a, microRNAs that reciprocally decreased intracellular in CS-exposed endothelium. CS-released EMPs and cMPs were ceramide-rich and required the ceramide-synthesis enzyme acid sphingomyelinase (aSMase) for their release, an enzyme which was found to exhibit significantly higher activity in plasma of COPD patients or of CS-exposed mice. The ex vivo or in vivo engulfment of EMPs or cMPs by peripheral blood monocytes-derived macrophages was associated with significant inhibition of efferocytosis. Our results indicate that CS, via aSMase, releases circulating EMPs with distinct microRNA cargo and that EMPs affect the clearance of apoptotic cells by specialized macrophages. These targetable effects may be important in the pathogenesis of diseases linked to endothelial injury and inflammation in smokers.

Sepsis Induces Hematopoietic Stem Cell Exhaustion and Myelosuppression through Distinct Contributions of TRIF and MYD88.

Toll-like receptor 4 (TLR4) plays a central role in host responses to bacterial infection, but the precise mechanism(s) by which its downstream signaling components coordinate the bone marrow response to sepsis is poorly understood. Using mice deficient in TLR4 downstream adapters MYD88 or TRIF, we demonstrate that both cell-autonomous and non-cell-autonomous MYD88 activation are major causes of myelosuppression during sepsis, while having a modest impact on hematopoietic stem cell (HSC) functions. In contrast, cell-intrinsic TRIF activation severely compromises HSC self-renewal without directly affecting myeloid cells. Lipopolysaccharide-induced activation of MYD88 or TRIF contributes to cell-cycle activation of HSC and induces rapid and permanent changes in transcriptional programs, as indicated by persistent downregulation of Spi1 and CebpA expression after transplantation. Thus, distinct mechanisms downstream of TLR4 signaling mediate myelosuppression and HSC exhaustion during sepsis through unique effects of MyD88 and TRIF.

Notch-dependent repression of miR-155 in the bone marrow niche regulates hematopoiesis in an NF-κB-dependent manner.

The microRNA miR-155 has been implicated in regulating inflammatory responses and tumorigenesis, but its precise role in linking inflammation and cancer has remained elusive. Here, we identify a connection between miR-155 and Notch signaling in this context. Loss of Notch signaling in the bone marrow (BM) niche alters hematopoietic homeostasis and leads to lethal myeloproliferative-like disease. Mechanistically, Notch signaling represses miR-155 expression by promoting binding of RBPJ to the miR-155 promoter. Loss of Notch/RBPJ signaling upregulates miR-155 in BM endothelial cells, leading to miR-155-mediated targeting of the nuclear factor κB (NF-κB) inhibitor κB-Ras1, NF-κB activation, and increased proinflammatory cytokine production. Deletion of miR-155 in the stroma of RBPJ(-/-) mice prevented the development of myeloproliferative-like disease and cytokine induction. Analysis of BM from patients carrying myeloproliferative neoplasia also revealed elevated expression of miR-155. Thus, the Notch/miR-155/κB-Ras1/NF-κB axis regulates the inflammatory state of the BM niche and affects the development of myeloproliferative disorders.

CD166 regulates human and murine hematopoietic stem cells and the hematopoietic niche.

We previously showed that immature CD166(+) osteoblasts (OB) promote hematopoietic stem cell (HSC) function. Here, we demonstrate that CD166 is a functional HSC marker that identifies both murine and human long-term repopulating cells. Both murine LSKCD48(-)CD166(+)CD150(+) and LSKCD48(-)CD166(+)CD150(+)CD9(+) cells, as well as human Lin(-)CD34(+)CD38(-)CD49f(+)CD166(+) cells sustained significantly higher levels of chimerism in primary and secondary recipients than CD166(-) cells. CD166(-/-) knockout (KO) LSK cells engrafted poorly in wild-type (WT) recipients and KO bone marrow cells failed to radioprotect lethally irradiated WT recipients. CD166(-/-) hosts supported short-term, but not long-term WT HSC engraftment, confirming that loss of CD166 is detrimental to the competence of the hematopoietic niche. CD166(-/-) mice were significantly more sensitive to hematopoietic stress. Marrow-homed transplanted WT hematopoietic cells lodged closer to the recipient endosteum than CD166(-/-) cells, suggesting that HSC-OB homophilic CD166 interactions are critical for HSC engraftment. STAT3 has 3 binding sites on the CD166 promoter and STAT3 inhibition reduced CD166 expression, suggesting that both CD166 and STAT3 may be functionally coupled and involved in HSC competence. These studies illustrate the significance of CD166 in the identification and engraftment of HSC and in HSC-niche interactions, and suggest that CD166 expression can be modulated to enhance HSC function.

Noise tolerance in a Neocognitron-like network.

The Neocognitron and its related hierarchical models have been shown to be competitive in recognizing handwritten digits and objects. However, the tolerance of these models to several types of noise can be low. We will start by briefly overviewing some previous results regarding the tolerance of these models. Afterwards, we report the higher noise tolerance of the winner-take-all response in a hierarchical model over related models. We provide an analysis and interpretation of this tolerance under Bayesian decision theory. Finally, we report on how to further improve recognition for extremely noisy patterns.

APE1/Ref-1 regulates STAT3 transcriptional activity and APE1/Ref-1-STAT3 dual-targeting effectively inhibits pancreatic cancer cell survival.

Pancreatic cancer is a largely incurable disease, and increasing evidence supports strategies targeting multiple molecular mediators of critical functions of pancreatic ductal adenocarcinoma cells. Intracellular redox state modulates the activity of various signal transduction pathways and biological processes, including cell survival, drug resistance and responsiveness to microenvironmental factors. Recently, it has been shown that the transcription factor STAT3 is under redox control, but the mechanisms involved in its regulation are unknown. Here, we demonstrate for the first time that STAT3 DNA binding and transcriptional activity is directly regulated by the redox function of the APE1/Ref-1 endonuclease, using overexpression and redox-specific mutational strategies, and gene knockdown. Also, pharmacological blockade of APE1/Ref-1 by the redox-selective inhibitor E3330 abrogates STAT3 DNA binding. Since APE1/Ref-1 also exerts redox control on other cancer-associated transcription factors, we assessed the impact of dual-targeting of STAT3 signaling and APE1/Ref-1 redox on pancreatic cancer cell functions. We observed that disruption of APE1/Ref-1 redox activity synergizes with STAT3 blockade to potently inhibit the proliferation and viability of human PDAC cells. Mechanistically, we show that STAT3-APE1/Ref-1 dual targeting promotes marked tumor cell apoptosis, with engagement of caspase-3 signaling, which are significantly increased in comparison to the effects triggered by single target blockade. Also, we show that STAT3-APE1/Ref-1 dual blockade results in significant inhibition of tumor cell migration. Overall, this work demonstrates that the transcriptional activity of STAT3 is directly regulated by the redox function of APE1/Ref-1, and that concurrent blockade of STAT3 and APE1/Ref-1 redox synergize effectively inhibit critical PDAC cell functions.