Decreases in different Dnmt3b activities drive distinct development of hematologic malignancies in mice.

DNA methylation regulates gene transcription and is involved in various physiological processes in mammals, including development and hematopoiesis. It is catalyzed by DNA methyltransferases including Dnmt1, Dnmt3a, and Dnmt3b. For Dnmt3b, its effects on transcription can result from its own DNA methylase activity, the recruitment of other Dnmts to mediate methylation, or transcription repression in a methylation-independent manner. Low-frequency mutations in human DNMT3B are found in hematologic malignancies including cutaneous T-cell lymphomas, hairy cell leukemia, and diffuse large B-cell lymphomas. Moreover, Dnmt3b is a tumor suppressor in oncogene-driven lymphoid and myeloid malignancies in mice. However, it is poorly understood how the different Dnmt3b activities contribute to these outcomes. We modulated Dnmt3b activity in vivo by generating Dnmt3b+/- mice expressing one wild-type allele as well as Dnmt3b+/CI and Dnmt3bCI/CI mice where one or both alleles express catalytically inactive Dnmt3bCI. We show that 43% of Dnmt3b+/- mice developed T-cell lymphomas, chronic lymphocytic leukemia, and myeloproliferation over 18 months, thus resembling phenotypes previously observed in Dnmt3a+/- mice, possibly through regulation of shared target genes. Interestingly, Dnmt3b+/CI and Dnmt3bCI/CI mice survived postnatal development and were affected by B-cell rather than T-cell malignancies with decreased penetrance. Genome-wide hypomethylation, increased expression of oncogenes such as Jdp2, STAT1, and Trip13, and p53 downregulation were major events contributing to Dnmt3b+/- lymphoma development. We conclude that Dnmt3b catalytic activity is critical to prevent B-cell transformation in vivo, whereas accessory and methylation-independent repressive functions are important to prevent T-cell transformation.

An aberrantly sustained emergency granulopoiesis response accelerates postchemotherapy relapse in MLL1-rearranged acute myeloid leukemia in mice.

Acute myeloid leukemia (AML) with mixed lineage leukemia 1 (MLL1) gene rearrangement is characterized by increased expression of a set of homeodomain transcription factors, including homeobox A9 (HOXA9) and HOXA10. The target genes for these regulators include fibroblast growth factor 2 (FGF2) and Ariadne RBR E3 ubiquitin ligase 2 (ARIH2). FGF2 induces leukemia stem cell expansion in MLL1-rearranged AML. ARIH2 encodes TRIAD1, an E3 ubiquitin ligase required for termination of emergency granulopoiesis and leukemia suppressor function in MLL1-rearranged AML. Receptor tyrosine kinases (RTKs), including the FGF receptor, are TRIAD1 substrates that are possibly relevant to these activities. Using transcriptome analysis, we found increased activity of innate immune response pathways and RTK signaling in bone marrow progenitors from mice with MLL1-rearranged AML. We hypothesized that sustained RTK signaling, because of decreased TRIAD1 activity, impairs termination of emergency granulopoiesis during the innate immune response and contributes to leukemogenesis in this AML subtype. Consistent with this, we found aberrantly sustained emergency granulopoiesis in a murine model of MLL1-rearranged AML, associated with accelerated leukemogenesis. Treating these mice with an inhibitor of TRIAD1-substrate RTKs terminated emergency granulopoiesis, delayed leukemogenesis during emergency granulopoiesis, and normalized innate immune responses when combined with chemotherapy. Emergency granulopoiesis also hastened postchemotherapy relapse in mice with MLL1-rearranged AML, but remission was sustained by ongoing RTK inhibition. Our findings suggest that the physiological stress of infectious challenges may drive AML progression in molecularly defined subsets and identify RTK inhibition as a potential therapeutic approach to counteract this process.

Nanobiosensor Reports on CDK1 Kinase Activity in Tumor Xenografts in Mice.

Probing the dynamics and quantifying the activities of intracellular protein kinases that coordinate cell growth and division and constitute biomarkers and pharmacological targets in hyperproliferative and pathological disorders remain a challenging task. Here engineering and characterization of a nanobiosensor of the mitotic kinase CDK1, through multifunctionalization of carbon nanotubes with a CDK1-specific fluorescent peptide reporter, are described. This original reporter of CDK1 activity combines the sensitivity of a fluorescent biosensor with the unique physico-chemical and biological properties of nanotubes for multifunctionalization and efficient intracellular penetration. The functional versatility of this nanobiosensor enables implementation to quantify CDK1 activity in a sensitive and dose-dependent fashion in complex biological environments in vitro, to monitor endogenous kinase in living cells and directly within tumor xenografts in mice by fluorescence imaging, thanks to a ratiometric quantification strategy accounting for response relative to concentration in space and in time.

Pharmacological inhibition of IRAK1 attenuates colitis-induced tumorigenesis in mice by inhibiting the inflammatory response and epithelial-mesenchymal transition.

Colorectal cancer (CRC) is the third most common type of cancer. Here, we studied the inhibitory effect of IRAK1 and IRAK4 as a preventive strategy using a colitis-induced tumorigenesis mouse model. CRC clinical data were obtained from the Gene Expression Omnibus (GEO). An experimental inflammation-dependent CRC model was induced by treatment with azoxymethane (AOM) and then dextran sodium sulfate (DSS) in C57BL/6 mice. Mice were administered an IRAK1/4 inhibitor by intraperitoneal injection at 3 mg/kg twice each week for 9 weeks. The IRAK1/4 inhibitor attenuated histological changes and prevented tumor growth. Tumor-associated proteins, including p65 and Ki-67, were downregulated by the IRAK1/4 inhibitor in AOM/DSS-treated mice. Additionally, IRAK1/4 inhibitor administration effectively decreased the expression of inflammatory cytokines. Furthermore, we observed that IRAK1/4 inhibitor treatment attenuated colitis-induced tumorigenesis by inhibiting epithelial-mesenchymal transition. These observations indicate that inhibition of IRAK1 and IRAK4 may suppress experimental colitis-induced tumorigenesis by inhibiting inflammatory responses and epithelial-mesenchymal transition.

Hexokinase 2 in Cancer: A Prima Donna Playing Multiple Characters.

Hexokinases are a family of ubiquitous exose-phosphorylating enzymes that prime glucose for intracellular utilization. Hexokinase 2 (HK2) is the most active isozyme of the family, mainly expressed in insulin-sensitive tissues. HK2 induction in most neoplastic cells contributes to their metabolic rewiring towards aerobic glycolysis, and its genetic ablation inhibits malignant growth in mouse models. HK2 can dock to mitochondria, where it performs additional functions in autophagy regulation and cell death inhibition that are independent of its enzymatic activity. The recent definition of HK2 localization to contact points between mitochondria and endoplasmic reticulum called Mitochondria Associated Membranes (MAMs) has unveiled a novel HK2 role in regulating intracellular Ca2+ fluxes. Here, we propose that HK2 localization in MAMs of tumor cells is key in sustaining neoplastic progression, as it acts as an intersection node between metabolic and survival pathways. Disrupting these functions by targeting HK2 subcellular localization can constitute a promising anti-tumor strategy.

Cannabinoid Quinones-A Review and Novel Observations.

A cannabinoid anticancer para-quinone, HU-331, which was synthesized by our group five decades ago, was shown to have very high efficacy against human cancer cell lines in-vitro and against in-vivo grafts of human tumors in nude mice. The main mechanism was topoisomerase IIα catalytic inhibition. Later, several groups synthesized related compounds. In the present presentation, we review the publications on compounds synthesized on the basis of HU-331, summarize their published activities and mechanisms of action and report the synthesis and action of novel quinones, thus expanding the structure-activity relationship in these series.

The anti-mitotic agents PTC-028 and PTC596 display potent activity in pre-clinical models of multiple myeloma but challenge the role of BMI-1 as an essential tumour gene.

Future progress in the treatment of multiple myeloma (MM) requires both the characterisation of key drivers of the disease and novel, innovative approaches to tackle these vulnerabilities. The present study focussed on the pre-clinical evaluation of a novel drug class, BMI-1 modulators, in MM. We demonstrate potent activity of PTC-028 and PTC596 in a comprehensive set of in vitro and in vivo models, including models of drug resistance and stromal support. Treatment of MM cells with PTC-028 and PTC596 downregulated BMI-1 protein levels, which was found to correlate with drug activity. Surprisingly, BMI-1 was dispensable for the activity of BMI-1 modulators and MM cell growth. Our data rather point to mitotic arrest accompanied by myeloid cell leukaemia-1 (MCL-1) loss as key anti-MM mechanisms and reveal impaired MYC and AKT signalling activity due to BMI-1 modulator treatment. Moreover, we observed a complete eradication of MM after PTC596 treatment in the 5TGM.1 in vivo model and define epigenetic compounds and B cell leukaemia/lymphoma 2 homology domain 3 (BH3) mimetics as promising combination partners. These results bring into question the postulated role of BMI-1 as an essential MM gene and confirm BMI-1 modulators as potent anti-mitotic agents with encouraging pre-clinical activity that supports their rapid translation into clinical trials.

Integrated computational and Drosophila cancer model platform captures previously unappreciated chemicals perturbing a kinase network.

Drosophila provides an inexpensive and quantitative platform for measuring whole animal drug response. A complementary approach is virtual screening, where chemical libraries can be efficiently screened against protein target(s). Here, we present a unique discovery platform integrating structure-based modeling with Drosophila biology and organic synthesis. We demonstrate this platform by developing chemicals targeting a Drosophila model of Medullary Thyroid Cancer (MTC) characterized by a transformation network activated by oncogenic dRetM955T. Structural models for kinases relevant to MTC were generated for virtual screening to identify unique preliminary hits that suppressed dRetM955T-induced transformation. We then combined features from our hits with those of known inhibitors to create a 'hybrid' molecule with improved suppression of dRetM955T transformation. Our platform provides a framework to efficiently explore novel kinase inhibitors outside of explored inhibitor chemical space that are effective in inhibiting cancer networks while minimizing whole body toxicity.

Recombinant Lactaptin Induces Immunogenic Cell Death and Creates an Antitumor Vaccination Effect in Vivo with Enhancement by an IDO Inhibitor.

Natural compounds of various origins are intensively investigated for their antitumor activity. Potential benefits of antitumor therapy can be achieved when cytotoxic agents kill cancer cells and these dying cancer cells drive adoptive immunity to the tumor. This strategy was successfully demonstrated for chemotherapeutic drugs that induce immunogenic type of cell death (ICD) with release of DAMPs (danger associated molecular patterns) and exposure of "eat me" signals. In this study, we demonstrated that recombinant human milk peptide lactaptin (RL2) induces death of cancer cells with ICD hallmarks in vitro with the release of ATP and high-mobility group box 1 protein (HMGB1) and exposure of calreticulin and HSP70 on the external cell membrane. RL2-treated cancer cells were efficiently engulfed by phagocytic cells. Using the syngeneic mouse model, we demonstrated that RL2-treated MX-7 rhabdomyosarcoma cells confer long-term immune-mediated protection against challenge with live MX-7 cells. We also analyzed the combinatorial antitumor effect of vaccination with RL2-treated cells and the inhibition of indoleamine 2,3-dioxygenase (IDO) with ethyl pyruvate. Compared to solo anti-tumor immunization with RL2-treated cells, additional chemical inhibition of IDO demonstrated better long-term antitumor responses than vaccination alone.

Generation of conditional ALK F1174L mutant mouse models for the study of neuroblastoma pathogenesis.

Neuroblastoma, an embryonal tumor arising from the sympathetic ganglia and adrenal medulla, is among the most intractable pediatric cancers. Although a variety of genetic changes have been identified in neuroblastoma, how they contribute to its pathogenesis remains largely unclear. Recent studies have identified alterations of the anaplastic lymphoma kinase (ALK) gene in neuroblastoma; ALK F1174L (a phenylalanine-to-leucine substitution at codon 1174) represents one of the most frequent of these somatic mutations, and is associated with amplification of the MYCN gene, the most reliable marker for the poor survival. We engineered the mouse Alk locus so that ALK F1174L is expressed by its endogenous promoter and can be induced in a spatiotemporally controlled fashion using Cre-loxP system. Although expression of ALK F1174L resulted in enhanced proliferation of sympathetic ganglion progenitors and increased the size of the sympathetic ganglia, it was insufficient to cause neuroblastoma. However, lethal neuroblastoma frequently developed in mice co-expressing ALK F1174L and MYCN, even in a genetic background where MYCN alone does not cause overt tumors. These data reveal that physiological expression of ALK F1174L significantly potentiates the oncogenic ability of MYCN in vivo. Our conditional mutant mice provide a valuable platform for investigating the pathogenesis of neuroblastoma.

Methionine sulfoxide reductase B1 regulates proliferation and invasion by affecting mitogen-activated protein kinase pathway and epithelial-mesenchymal transition in u2os cells.

Methionine sulfoxide reductase B1 (MsrB1), a member of the selenoprotein family and contributes significantly to the reduction of methionine sulfoxides produced from reactive oxygen species (ROS). However, few studies have examined the role of MsrB1 in tumors. Here We tested the proliferation and invasion in MsrB1 knockdown u2os cells under H2O2/thioredoxin. As shown in our result, knockdown of MsrB1 inhibited the proliferation of u2os cells and regulates mitogen-activated protein kinase (MAPK) pathway by down-regulation of Erk, MeK phosphorylation and p53 expression in u2os cells. In a xenograft tumorigenicity mice, MsrB1 knockdown effectively inhibited tumor growth. Furthermore, MsrB1 knockdown resulted in migration and invasion reducement of u2os cells. MsrB1 regulates epithelial-mesenchymal transition (EMT) via affecting cytoskeleton by increasing E-cadherin expression and decreasing N-cadherin, TGF-ß1, slug, fibronectin, vimentin, c-myc, snail and ß-catenin expressions. In vivo, MsrB1 shRNAi can inhibit lung metastasis in metastasis model. In conclusion, MsrB1 regulates proliferation and invasion of u2os cells by affecting MAPK pathway and EMT, and MsrB1 gene may be a novel therapeutic target against tumors.

Decreased expression of protein tyrosine kinase 6 contributes to tumor progression and metastasis in laryngeal squamous cell carcinoma.

BACKGROUND: PTK6 is involved in cell proliferation, invasion and migration. Patients with lower PTK6 expression predicts poor prognosis of LSCC. However, the mechanism of PTK6 in LSCC progression remains unclear. We investigated the role of PTK6 in the pathogenesis of LSCC. METHODS: Human LSCC tissues and paired adjacent non-tumor tissues were obtained to evaluate PTK6 expression. The biological function of PTK6 in LSCC was determined by overexpression of PTK6 in Hep-2 cells in vitro and in nude mice. The potential PTK6 target factors and signaling pathways were identified by Western blotting assay and immunohistochemical staining. RESULTS: PTK6 was downregulated in tissues of human LSCC. Biological function investigation of PTK6 demonstrated that overexpression of PTK6 significantly decreased cell growth, clonogenicity, invasion and migration capacity in vitro and suppressed xenograft tumor growth as well as lung metastasis in vivo. PTK6 suppresses LSCC proliferation mainly by inhibiting c-myc and cyclinD1 expression. In addition, PTK6 promotes cell apoptosis in LSCC. Moreover, PTK6 mitigated LSCC invasion and migration through regulating EMT and MMP-9. CONCLUSION: PTK6 plays a tumor suppressor role in LSCC by regulating c-myc and cyclinD1 expression, cell apoptosis, EMT and MMP-9.

Caffeic acid prevents UVB radiation induced photocarcinogenesis through regulation of PTEN signaling in human dermal fibroblasts and mouse skin.

Previously, we proved that caffeic acid (CA), a major dietary phenolic acid, prevents skin carcinogenesis by modulating inflammatory signaling in mouse skin. However, the actual mechanisms of CA against UVB (280-320 nm) induced photocarcinogenesis remains unclear. The present results confirms that CA significantly inhibits single UVB-induced CPDs formation, oxidative DNA damage, ROS generation and frequency of apoptotic cell death in human dermal fibroblasts (HDFa). Furthermore, CA prevents UVB-induced expression of PI3K and AKT kinases through activation of PTEN which subsequently promotes XPC dependant NER proteins such as XPC, XPE, TFIIH (p44) and ERCC1 in HDFa cells and mouse skin tissue. Further, CA directly activates PTEN through hydrogen bond and hydrophobic interactions. Taken together, these findings suggest that CA prevents UVB-induced photodamage through the activation of PTEN expression in human dermal fibroblasts and mouse skin.

Acetazolamide-based [18F]-PET tracer: In vivo validation of carbonic anhydrase IX as a sole target for imaging of CA-IX expressing hypoxic solid tumors.

Carbonic anhydrase IX is overexpressed in many solid tumors including hypoxic tumors and is a potential target for cancer therapy and diagnosis. Reported imaging agents targeting CA-IX are successful mostly in clear cell renal carcinoma as SKRC-52 and no candidate was approved yet in clinical trials for imaging of CA-IX. To validate CA-IX as a valid target for imaging of hypoxic tumor, we designed and synthesized novel [18F]-PET tracer (1) based on acetazolamide which is one of the well-known CA-IX inhibitors and performed imaging study in CA-IX expressing hypoxic tumor model as 4T1 and HT-29 in vivo models other than SKRC-52. [18F]-acetazolamide (1) was found to be insufficient for the specific accumulation in CA-IX expressing tumor. This study might be useful to understand in vivo behavior of acetazolamide PET tracer and can contribute to the development of successful PET imaging agents targeting CA-IX in future. Additional study is needed to understand the mechanism of poor targeting of CA-IX, as if CA-IX is not reliable as a sole target for imaging of CA-IX expressing hypoxic solid tumors.

In vivo tumor imaging by a γ-glutamyl transpeptidase-activatable near-infrared fluorescent probe.

γ-Glutamyl transpeptidase (GGT), overexpressed in various cancer cells, has been perceived as a latent tumor biomarker. Thus, developing near-infrared (NIR) fluorescent GGT probes is highly desired for in vivo tumor imaging and studies. To our knowledge, however, such a GGT probe is still rare. Herein, we construct a new GGT-activatable NIR fluorescent probe HCAGlu by incorporating γ-glutamyl group as a recognition unit directly into a NIR hemicyanine fluorophore. HCAGlu exhibits a highly sensitive and selective NIR fluorescence off-on response to GGT. The probe has been applied to cell and histological section imaging, which demonstrates the ability of HCAGlu in distinguishing different GGT-expression levels in situ in biological samples. Notably, in vivo fluorescence imaging in tumor-bearing mice has been performed, verifying that probe HCAGlu can rapidly produce a distinct fluorescence signal in the tumor site via both intravenous and intratumoral injections. The simplicity and excellent performance of HCAGlu make it of high potential in studying the physiological function of GGT in vivo. Graphical abstract A near-infrared fluorescent probe for imaging γ-glutamyl transpeptidase in biological samples.

Therapeutic Cell-Cycle-Decoy Efficacy of a Telomerase-Dependent Adenovirus in an Orthotopic Model of Chemotherapy-Resistant Human Stomach Carcinomatosis Peritonitis Visualized With FUCCI Imaging.

We have established an orthotopic nude-mouse model of gastric cancer carcinomatosis peritonitis, a recalcitrant disease in human patients. Human MKN45 poorly-differentiated human gastric cancer cells developed carcinomatosis peritonitis upon orthotopic transplantation in nude mice. The MKN45 cells expressed the fluorescent ubiquitination-based cell cycle indicator (FUCCI) that color codes the phases of the cell cycle. The intra-peritoneal tumors and ascites contained mostly quiescent G1 /Go cancer cells visualized as red by FUCCI imaging. Cisplatinum (CDDP) treatment did not reduce bloody ascites, and larger tumors formed in the peritoneal cavity after CDDP treatment in an early-stage carcinomatosis peritonitis orthotopic mouse model. Paclitaxel-treated mice had reduced ascites, but also had large tumor masses in the peritonium after treatment with cancer cells mostly in G0 /G1 , visualized by FUCCI red. In contrast, OBP-301 telomerase-dependent adenovirus-treated mice had no ascites and only small tumor nodules consisting of cancer cells mostly in S/G2 phases in the early-stage carcinomatosis peritonitis model, visualized by FUCCI green. Furthermore, OBP-301 significantly reduced the size of tumors (P < 0.01) and ascites even in a late-stage carcinomatosis peritonitis model. These results suggest that quiescent peritoneally-disseminated gastric cancer cells are resistant to conventional chemotherapy, but OBP-301 significantly reduced the weight of the tumors and increased survival, suggesting clinical potential. J. Cell. Biochem. 118: 3635-3642, 2017. © 2016 Wiley Periodicals, Inc.

Angiotensin-converting enzyme 2 is a potential therapeutic target for EGFR-mutant lung adenocarcinoma.

EGFR-mutant lung adenocarcinomas contain a subpopulation of cells that have undergone epithelial-to-mesenchymal transition and can grow independently of EGFR. To kill these cancer cells, we need a novel therapeutic approach other than EGFR inhibitors. If a molecule is specifically expressed on the cell surface of such EGFR-independent EGFR-mutant cancer cells, it can be a therapeutic target. We found that a mesenchymal EGFR-independent subline derived from HCC827 cells, an EGFR-mutant lung adenocarcinoma cell line, expressed angiotensin-converting enzyme 2 (ACE2) to a greater extent than its parental cells. ACE2 was also expressed at least partially in most of the primary EGFR-mutant lung adenocarcinomas examined, and the ACE2 expression level in the cancer cells was much higher than that in normal lung epithelial cells. In addition, we developed an anti-ACE2 mouse monoclonal antibody (mAb), termed H8R64, that was internalized by ACE2-expressing cells. If an antibody-drug conjugate consisting of a humanized mAb based on H8R64 and a potent anticancer drug were produced, it could be effective for the treatment of EGFR-mutant lung adenocarcinomas.

A novel two-photon fluorescent probe with a long Stokes shift and a high signal-to-background ratio for human NAD(P)H:quinone oxidoreductase 1 (hNQO1) detection and imaging in living cells and tissues.

In recent years, many activatable fluorescent probes have been developed for hNQO1 detection. However, most of the reported fluorescent probes are susceptible to the interferences of endogenous fluorescence and have the drawback of inadequate penetration depth. Very recently, researchers have reported a two-photon excitation (TPE) fluorescent probe for hNQO1 detection. Nevertheless, this probe only exhibits a compromised signal-to-background ratio, and has not been applied to image hNQO1 in living tissues. Herein, a novel TPE fluorescent probe, trimethyl locked quinone caged Acedan (Q3CA-P), has been developed for hNQO1 detection and imaging in living cells and tissues. Q3CA-P displays over 25-fold enhancement in fluorescence intensity toward hNQO1 with a Stokes shift over 100 nm in one-photon excitation and exhibits a very low detection limit of 5.6 ng mL-1. The imaging experiments performed in tumour cells and tissue slices using Q3CA-P demonstrate that Q3CA-P could image the endogenous hNQO1 with high selectivity and sensitivity with a TPE probing depth of 120 µm. Thus, our probe may have great potential for use in cancer diagnosis and image-guided surgery.

An efficient two-photon fluorescent probe for measuring γ-glutamyltranspeptidase activity during the oxidative stress process in tumor cells and tissues.

Oxidative stress, a disturbance in the balance between oxidant/antioxidant ratios, is associated with cancer, aging, inflammation, neurodegenerative diseases and other conditions. γ-Glutamyltranspeptidase (GGT) is a redox-related enzyme that plays a key role in mitigating the effects of oxidative stress by maintaining cellular glutathione (GSH) metabolism and homeostasis. Therefore, oxidative stress will upregulate the intracellular GGT level. To better understand the major pathophysiological resist mechanism to oxidative injury in mediating many disease states, we designed and synthesized a novel two-photon (TP) fluorescent turn-on probe, Np-Glu, for GGT detection and bioimaging. Under the optimized conditions, Np-Glu exhibited remarkable fluorescence enhancement (150-fold), good selectivity and high sensitivity (LOD is 0.033 U L-1), with a wide linear concentration range (0-50 U L-1). More importantly, the probe Np-Glu was successfully applied in one-photon and TP fluorescence imaging of GGT activity in an oxidative stress model in living cells and tissues, suggesting Np-Glu as an ideal indicator for clinical and biological samples.

Histamine promotes the development of monocyte-derived dendritic cells and reduces tumor growth by targeting the myeloid NADPH oxidase.

The efficiency of immune-mediated clearance of cancer cells is hampered by immunosuppressive mediators in the malignant microenvironment, including NADPH oxidase-derived reactive oxygen species. We aimed at defining the effects of histamine, an inhibitor of the myeloid NADPH oxidase/NOX2, on the development of Ag-presenting dendritic cells (DCs) from myeloid precursors and the impact of these mechanisms for tumor growth. Histamine was found to promote the maturation of human DCs from monocytes by increasing the expression of HLA-DR and costimulatory molecules, which resulted in improved induction of Th cells with Th0 polarity. Experiments using wild-type and NOX2-deficient myelomonoblastic cells showed that histamine facilitated myeloid cell maturation only in cells capable of generating reactive oxygen species. Treatment of mice with histamine reduced the growth of murine EL-4 lymphomas in parallel with an increment of tumor-infiltrating DCs in NOX2-sufficient mice but not in NOX2-deficient (gp91(phox) (-/-)) mice. We propose that strategies to target the myeloid NADPH oxidase may facilitate the development of endogenous DCs in cancer.