Mutant p53 and NOX4 are modulators of a CCL5-driven pro-migratory secretome

Previously, we showed wild-type (WT) and mutant (mt) forms of p53 differentially regulate ROS generation by NADPH oxidase-4 (NOX4). We found that WT-p53 suppresses TGF-β-induced NOX4, ROS production, and cell migration, whereas tumor-associated mt-p53 proteins enhance NOX4 expression and cell migration by TGF-β/SMAD3-dependent mechanisms. In this study, we investigated the role of mutant p53-induced NOX4 on the cancer cell secretome and the effects NOX4 signaling have on the tumor microenvironment (TME). We found conditioned media collected from H1299 lung epithelial cells stably expressing either mutant p53-R248Q or R273H promotes the migration and invasion of naïve H1299 cells and chemotactic recruitment of THP-1 monocytes. These effects were diminished with conditioned media from cells co-transfected with dominant negative NOX4 (P437H). We utilized immunoblot-based cytokine array analysis to identify factors in mutant p53 H1299 cell conditioned media that promote cell migration and invasion. We found CCL5 was significantly reduced in conditioned media from H1299 cells co-expressing p53-R248Q and dominant negative NOX4. Moreover, neutralization of CCL5 reduced autocrine-mediated H1299 cell mobility. Furthermore, CCL5 and TGF-beta from M2-polarized macrophages have a significant role in crosstalk and H1299 cell migration and invasion. Collectively, our findings provide further insight into NOX4-based communication in the tumor microenvironment and its potential as a therapeutic target affecting metastatic disease progression.

Immunogenetics associated with severe coccidioidomycosis

Disseminated coccidioidomycosis (DCM) is caused by Coccidioides, pathogenic fungi endemic to the southwestern United States and Mexico. Illness occurs in approximately 30% of those infected, less than 1% of whom develop disseminated disease. To address why some individuals allow dissemination, we enrolled patients with DCM and performed whole-exome sequencing. In an exploratory set of 67 patients with DCM, 2 had haploinsufficient STAT3 mutations, and defects in β-glucan sensing and response were seen in 34 of 67 cases. Damaging CLEC7A and PLCG2 variants were associated with impaired production of β-glucan-stimulated TNF-α from PBMCs compared with healthy controls. Using ancestry-matched controls, damaging CLEC7A and PLCG2 variants were overrepresented in DCM, including CLEC7A Y238* and PLCG2 R268W. A validation cohort of 111 patients with DCM confirmed the PLCG2 R268W, CLEC7A I223S, and CLEC7A Y238* variants. Stimulation with a DECTIN-1 agonist induced DUOX1/DUOXA1-derived hydrogen peroxide [H2O2] in transfected cells. Heterozygous DUOX1 or DUOXA1 variants that impaired H2O2 production were overrepresented in discovery and validation cohorts. Patients with DCM have impaired β-glucan sensing or response affecting TNF-α and H2O2 production. Impaired Coccidioides recognition and decreased cellular response are associated with disseminated coccidioidomycosis.

Functional Characterization of DUOX Enzymes in Reconstituted Cell Models

Biosynthesis of active human dual oxidases (DUOX1 and DUOX2) requires maturation factors, a.k.a. DUOX activator proteins (DUOXA1 and DUOXA2), that form covalent complexes with DUOX; both chains together represent the mature catalytic unit that functions as a dedicated hydrogen peroxide-generating enzyme. Genetic defects in DUOX2 or DUOXA2 can result in congenital hypothyroidism, whereas partial defects in DUOX2 activity also have been associated with very early-onset inflammatory bowel disease. Our understanding of the links between DUOX dysfunction and these diseases remains incomplete. An important challenge in developing a better understanding of the pathogenic roles of DUOX defects requires robust and reliable DUOX reconstitution cell models to examine the functional consequences of candidate DUOX missense mutations and polymorphisms. Here, we describe methods for efficient heterologous DUOX/DUOXA co-expression and functional characterization, including detailed assessments of posttranslational processing and subcellular translocation of DUOX that accompanies the maturation of these enzymes into catalytically active NADPH oxidases.

Histone modifications affect differential regulation of TGFβ- induced NADPH oxidase 4 (NOX4) by wild-type and mutant p53

Previously, we showed wild-type (WT) and mutant (mut) p53 differentially regulate reactive oxygen species (ROS) generation by NADPH oxidase-4 (NOX4): p53-WT suppresses TGFβ-induced NOX4, ROS and cell migration, whereas tumor-associated mut-p53 proteins enhance NOX4 expression and cell migration. Here, we extended our findings on the effects of p53 on NOX4 in several tumors and examined the basis of NOX4 transcriptional regulation by p53 and SMAD3. Statistical analysis of expression data from primary tumors available from The Cancer Genome Atlas (TCGA) detected correlations between mut-p53 and increased NOX4 expression. Furthermore, by altering p53 levels in cell culture models we showed several common tumor-associated mutant forms support TGFβ/SMAD3-dependent NOX4 expression. Deletion analysis revealed two critical SMAD3 binding elements (SBE) required for mut-p53-dependent NOX4 induction, whereas p53-WT caused dose-dependent suppression of NOX4 transcription. ChIP analysis revealed SMAD3 and p53-WT or mut-p53 associate with SBEs and p53 response elements in a TGFβ-dependent manner. Interestingly, the repressive effects of p53-WT on NOX4 were relieved by mutation of its transactivation domain or histone deacetylase (HDAC) inhibitor treatment. Overexpression of p300, a transcriptional co-regulator and histone acetyltransferase (HAT), enhanced p53-mediated NOX4 induction, whereas HAT-inactive p300 reduced NOX4 expression. Mut-p53 augmented TGFβ-stimulated histone acetylation within the NOX4 promoter. Finally, wound assays demonstrated NOX4 and p300 promote TGFβ/mut-p53-mediated cell migration. Our studies provide new insight into TGFβ/SMAD3 and mut-p53-mediated NOX4 induction involving epigenetic control of NOX4 in tumor cell migration, suggesting NOX4 is a potential therapeutic target to combat tumor progression and metastasis.

Abstract 5508: Histone modifications affect differential regulation of TGF-beta-induced Nox4 by p53

Recent studies suggest p53 plays an important role in TGF-β-mediated cell signaling and migration. Previously, we showed wild-type (WT) and mutant (mt) forms of p53 differentially regulate reactive oxygen species (ROS) generation by NADPH oxidase-4 (NOX4). We found that WT-p53 suppresses TGF-β-induced NOX4, ROS production, and cell migration, whereas tumor-associated p53-mt proteins enhance NOX4 expression and cell migration by TGF-β/SMAD3-dependent mechanisms. In this study, we utilized The Cancer Genome Atlas (TCGA) to perform statistical analysis on gene expression data from primary tumor samples and found a correlation between tumors with p53 “hotspot” mutations and increased NOX4 mRNA expression. Furthermore, we examined the basis of human NOX4 promoter regulation by p53 and SMAD3. By deletion analysis of the NOX4 promoter, we found two critical SMAD3 binding elements (SBE) are also required for p53-dependent promoter activity. Conversely, promoter activity was abolished by dose-dependent heterologous expression of p53-WT. Moreover, expression of active SMAD3 resulted in robust NOX4 promoter activity, which was abolished when co-expressed with p53-WT. Chromatin immunoprecipitation (ChIP) analysis revealed SMAD3 and p53-WT or p53-mt were associated with specific SBEs and p53 response elements (p53-RE) in a TGF-β-dependent manner. Interestingly, the repressive effect by p53-

WT on NOX4 was relieved upon treatment with histone deacetylase (HDAC) inhibitors or mutation of the transactivation domain. Overexpression of p300, a known p53-mt-binding transcriptional co-regulator and histone acetyltranserfase (HAT), enhanced p53-mt-mediated NOX4 promoter activity, whereas the HAT-inactive p300-mt reduced promoter activity. Furthermore, overexpression of p53-mt augmented TGF-β-mediated acetylation of histones associated with the NOX4 promoter. Finally, scratch wound assays demonstrated NOX4 and p300 promote TGF-β/mutant p53-mediated cell migration. Collectively, these data and provide new insight on TGF-β/SMAD3 and mutant p53-mediated NOX4 induction involving epigenetic control of NOX4 in tumor cell migration.

Citation Format: Howard E. Boudreau, Wei Feng MA, Agnieszka Korzeniowska, Jonathan J. Park, Thomas L. Leto. Histone modifications affect differential regulation of TGF-beta-induced Nox4 by p53 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5508. doi:10.1158/1538-7445.AM2017-5508

Peroxiredoxin 6 (Prdx6) supports NADPH oxidase1 (Nox1)-based superoxide generation and cell migration

Nox1 is an abundant source of reactive oxygen species (ROS) in colon epithelium recently shown to function in wound healing and epithelial homeostasis. We identified Peroxiredoxin 6 (Prdx6) as a novel binding partner of Nox activator 1 (Noxa1) in yeast two-hybrid screening experiments using the Noxa1 SH3 domain as bait. Prdx6 is a unique member of the Prdx antioxidant enzyme family exhibiting both glutathione peroxidase and phospholipase A2 activities. We confirmed this interaction in cells overexpressing both proteins, showing Prdx6 binds to and stabilizes wild type Noxa1, but not the SH3 domain mutant form, Noxa1 W436R. We demonstrated in several cell models that Prdx6 knockdown suppresses Nox1 activity, whereas enhanced Prdx6 expression supports higher Nox1-derived superoxide production. Both peroxidase- and lipase-deficient mutant forms of Prdx6 (Prdx6 C47S and S32A, respectively) failed to bind to or stabilize Nox1 components or support Nox1-mediated superoxide generation. Furthermore, the transition-state substrate analogue inhibitor of Prdx6 phospholipase A2 activity (MJ-33) was shown to suppress Nox1 activity, suggesting Nox1 activity is regulated by the phospholipase activity of Prdx6. Finally, wild type Prdx6, but not lipase or peroxidase mutant forms, supports Nox1-mediated cell migration in the HCT-116 colon epithelial cell model of wound closure. These findings highlight a novel pathway in which this antioxidant enzyme positively regulates an oxidant-generating system to support cell migration and wound healing.

Hypothyroidism-associated missense mutation impairs NADPH oxidase activity and intracellular trafficking of Duox2

In the thyroid gland Duox2-derived H2O2 is essential for thyroid hormone biosynthesis. Several patients were identified with partial or severe iodide organification defects caused by mutation in the gene for Duox2 or its maturation factor, DuoxA2. A Duox2-deficient (Duox2(thyd)) mouse model enabled in vivo investigation of its critical function in thyroid tissues, but its roles proposed in host defense or other innate responses in nonthyroid tissues remain less certain. These mice carry a spontaneous DUOX2 missense mutation, a T→G transversion, in exon 16 that changes the highly conserved valine 674 to glycine and results in severe congenital hypothyroidism. The exact mechanism underlying the effects of the V674G mutation has not been elucidated at the molecular or cellular level. To determine how the V674G mutation leads to congenital hypothyroidism, we introduced the same mutation into human Duox2 or Duox1 cDNAs and expressed them in HEK-293 cells stably expressing the corresponding DuoxA proteins. We found that the valine→glycine mutant Duox proteins fail to produce H2O2, lose their plasma membrane localization pattern, and are retained within the endoplasmic reticulum. The Duox2 mutant binds to DuoxA2, but appears to be unstable owing to this retention. Immunohistochemical staining of Duox2 in murine salivary gland ducts showed that Duox2 in mutant mice loses its condensed apical plasma membrane localization pattern characteristic of wild-type Duox2 and accumulates in punctate vesicular structures within cells. Our findings demonstrate that changing the highly conserved valine 674 in Duox2 leads to impaired subcellular targeting and reactive oxygen species release required for hormonogenesis, resulting in congenital hypothyroidism.

Nox4 involvement in TGF-beta and SMAD3-driven induction of the epithelial-to-mesenchymal transition and migration of breast epithelial cells

The epithelial-to-mesenchymal transition (EMT) is the development of increased cell plasticity that occurs normally during wound healing and embryonic development and can be coopted for cancer invasion and metastasis. TGF-beta induces EMT but the mechanism is unclear. Our studies suggest that Nox4, a member of the NADPH oxidase (Nox) family, is a source of reactive oxygen species (ROS) affecting cell migration and fibronectin expression, an EMT marker, in normal and metastatic breast epithelial cells. We found that TGF-beta induces Nox4 expression (mRNA and protein) and ROS generation in normal (MCF10A) and metastatic (MDA-MB-231) human breast epithelial cells. Conversely, cells expressing a dominant-negative form of Nox4 or Nox4-targeted shRNA showed significantly lower ROS production on TGF-beta treatment. Expression of a constitutively active TGF-beta receptor type I significantly increased Nox4 promoter activity, mRNA and protein expression, and ROS generation. Nox4 transcriptional regulation by TGF-beta was SMAD3 dependent based on the effect of constitutively active SMAD3 increasing Nox4 promoter activity, whereas dominant-negative SMAD3 or SIS3, a SMAD3-specific inhibitor, had the opposite effect. Furthermore, Nox4 knockdown, dominant-negative Nox4 or SMAD3, or SIS3 blunted TGF-beta induced wound healing and cell migration, whereas cell proliferation was not affected. Our experiments further indicate that Nox4 plays a role in TGF-beta regulation of fibronectin mRNA expression, based on the effects of dominant-negative Nox4 in reducing fibronectin mRNA in TGF-beta-treated MDA-MB-231and MCF10A cells. Collectively, these data indicate that Nox4 contributes to NADPH oxidase-dependent ROS production that may be critical for the progression of the EMT in breast epithelial cells, and thereby has therapeutic implications.

Duox maturation factors form cell surface complexes with Duox affecting the specificity of reactive oxygen species generation

Dual oxidases (Duox1 and Duox2) are plasma membrane-targeted hydrogen peroxide generators that support extracellular hemoperoxidases. Duox activator 2 (Duoxa2), initially described as an endoplasmic reticulum resident protein, functions as a maturation factor needed to deliver active Duox2 to the cell surface. However, less is known about the Duox1/Duoxa1 homologues. We identified four alternatively spliced Duoxa1 variants and explored their roles in Duox subcellular targeting and reconstitution. Duox1 and Duox2 are functionally rescued by Duoxa2 or the Duoxa1 variants that contain the third coding exon. All active maturation factors are cotransported to the cell surface when coexpressed with either Duox1 or Duox2, consistent with detection of endogenous Duoxa1 on apical plasma membranes of the airway epithelium. In contrast, the Duoxa proteins are retained in the endoplasmic reticulum when expressed without Duox. Duox1/Duoxa1alpha and Duox2/Duoxa2 pairs produce the highest levels of hydrogen peroxide, as they undergo Golgi-based carbohydrate modifications and form stable cell surface complexes. Cross-functioning pairs that do not form stable complexes produce less hydrogen peroxide and leak superoxide. These findings suggest Duox activators not only promote Duox maturation, but they function as part of the hydrogen peroxide-generating enzyme.

Dysembryoplastic neuroepithelial tumour (DNT). Is the mechanism of seizures related to glutamate? An immunohistochemical study

Dysembryoplastic neuroepithelial tumour (DNT) is a rare low-grade, mixed neuronal and glial tumour, usually associated with pharmacologically intractable, complex partial or generalised seizures which date from childhood. The prognosis after surgery is favourable. We present a classic case of DNT occurring in an 18-year-old male, who presented simple partial seizures without signs of raised intracranial pressure. CT and MR demonstrated focal mass located in the right temporal lobe. Histologically there were found the features of a typical DNT architecture with mixed cellular composition. The response to surgery was excellent. The tumour has not recurred, and the control of seizures remained good. Immunostaining for glutamate receptor GluR-2 showed stronger immunopositivity in neurones dispersed within the tumour and especially in margins of lesion as compared with apparently normal cerebral cortex. The expression of both excitatoryamino acid transporterproteins EAAT1 and EAAT2 was weaker then in normal cortex and uneven. This perhaps may explain the mechanism of seizures (elevated glutaminergic stimulation), and may suggest the excitotoxic damage of neurones.