The GAPDH redox switch safeguards reductive capacity and enables survival of stressed tumour cells

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is known to contain an active-site cysteine residue undergoing oxidation in response to hydrogen peroxide, leading to rapid inactivation of the enzyme. Here we show that human and mouse cells expressing a GAPDH mutant lacking this redox switch retain catalytic activity but are unable to stimulate the oxidative pentose phosphate pathway and enhance their reductive capacity. Specifically, we find that anchorage-independent growth of cells and spheroids is limited by an elevation of endogenous peroxide levels and is largely dependent on a functional GAPDH redox switch. Likewise, tumour growth in vivo is limited by peroxide stress and suppressed when the GAPDH redox switch is disabled in tumour cells. The induction of additional intratumoural oxidative stress by chemo- or radiotherapy synergized with the deactivation of the GAPDH redox switch. Mice lacking the GAPDH redox switch exhibit altered fatty acid metabolism in kidney and heart, apparently in compensation for the lack of the redox switch. Together, our findings demonstrate the physiological and pathophysiological relevance of oxidative GAPDH inactivation in mammals.

Expression of TRX1 optimizes the antitumor functions of human CAR T cells and confers resistance to a pro-oxidative tumor microenvironment

Use of chimeric antigen receptor (CAR) T cells to treat B cell lymphoma and leukemia has been remarkably successful. Unfortunately, the therapeutic efficacy of CAR T cells against solid tumors is very limited, with immunosuppression by the pro-oxidative tumor microenvironment (TME) a major contributing factor. High levels of reactive oxygen species are well-tolerated by tumor cells due to their elevated expression of antioxidant proteins; however, this is not the case for T cells, which consequently become hypo-responsive. The aim of this study was to improve CAR T cell efficacy in solid tumors by empowering the antioxidant capacity of CAR T cells against the pro-oxidative TME. To this end, HER2-specific human CAR T cells stably expressing two antioxidant systems: thioredoxin-1 (TRX1), and glutaredoxin-1 (GRX1) were generated and characterized. Thereafter, antitumor functions of CAR T cells were evaluated under control or pro-oxidative conditions. To provide insights into the role of antioxidant systems, gene expression profiles as well as global protein oxidation were analyzed. Our results highlight that TRX1 is pivotal for T cell redox homeostasis. TRX1 expression allows CAR T cells to retain their cytolytic immune synapse formation, cytokine release, proliferation, and tumor cell-killing properties under pro-oxidative conditions. Evaluation of differentially expressed genes and the first comprehensive redoxosome analysis of T cells by mass spectrometry further clarified the underlying mechanisms. Taken together, enhancement of the key antioxidant TRX1 in human T cells opens possibilities to increase the efficacy of CAR T cell treatment against solid tumors.

5’isomiR-183-5p|+2 elicits tumor suppressor activity in a negative feedback loop with E2F1

Background

MicroRNAs (miRNAs) and isomiRs play important roles in tumorigenesis as essential regulators of gene expression. 5’isomiRs exhibit a shifted seed sequence compared to the canonical miRNA, resulting in different target spectra and thereby extending the phenotypic impact of the respective common pre-miRNA. However, for most miRNAs, expression and function of 5’isomiRs have not been studied in detail yet. Therefore, this study aims to investigate the functions of miRNAs and their 5’isomiRs.

Methods

The expression of 5’isomiRs was assessed in The Cancer Genome Atlas (TCGA) breast cancer patient dataset. Phenotypic effects of miR-183 overexpression in triple-negative breast cancer (TNBC) cell lines were investigated in vitro and in vivo by quantifying migration, proliferation, tumor growth and metastasis. Direct targeting of E2F1 by miR-183-5p|+2 was validated with a 3’UTR luciferase assay and linked to the phenotypes of isomiR overexpression.

Results

TCGA breast cancer patient data indicated that three variants of miR-183-5p are highly expressed and upregulated, namely miR-183-5p|0, miR-183-5p|+1 and miR-183-5p|+2. However, TNBC cell lines displayed reduced proliferation and invasion upon overexpression of pre-miR-183. While invasion was reduced individually by all three isomiRs, proliferation and cell cycle progression were specifically inhibited by overexpression of miR-183-5p|+2. Proteomic analysis revealed reduced expression of E2F target genes upon overexpression of this isomiR, which could be attributed to direct targeting of E2F1, specifically by miR-183-5p|+2. Knockdown of E2F1 partially phenocopied the effect of miR-183-5p|+2 overexpression on cell proliferation and cell cycle. Gene set enrichment analysis of TCGA and METABRIC patient data indicated that the activity of E2F strongly correlated with the expression of miR-183-5p, suggesting transcriptional regulation of the miRNA by a factor of the E2F family. Indeed, in vitro, expression of miR-183-5p was regulated by E2F1. Hence, miR-183-5p|+2 directly targeting E2F1 appears to be part of a negative feedback loop potentially fine-tuning its activity.

Conclusions

This study demonstrates that 5’isomiRs originating from the same arm of the same pre-miRNA (i.e. pre-miR-183-5p) may exhibit different functions and thereby collectively contribute to the same phenotype. Here, one of three isomiRs was shown to counteract expression of the pre-miRNA by negatively regulating a transcriptional activator (i.e. E2F1). We speculate that this might be part of a regulatory mechanism to prevent uncontrolled cell proliferation, which is disabled during cancer progression.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02380-8.

Lysosomal enzyme trafficking factor LYSET enables nutritional usage of extracellular proteins

Mammalian cells can generate amino acids through macropinocytosis and lysosomal breakdown of extracellular proteins, which is exploited by cancer cells to grow in nutrient-poor tumors. Here, through genetic screens in defined nutrient conditions we characterized LYSET, a transmembrane protein (TMEM251) selectively required when cells consume extracellular proteins. LYSET was found to associate in the Golgi with GlcNAc-1-phosphotransferase, which targets catabolic enzymes to lysosomes through mannose-6-phosphate modification. Without LYSET, GlcNAc-1-phosphotransferase was unstable owing to a hydrophilic transmembrane domain. Consequently, LYSET-deficient cells were depleted of lysosomal enzymes and impaired in turnover of macropinocytic and autophagic cargoes. Thus, LYSET represents a core component of the lysosomal enzyme trafficking pathway, underlies the pathomechanism for hereditary lysosomal storage disorders, and may represent a target to suppress metabolic adaptations in cancer.

An episomal DNA vector platform for the persistent genetic modification of pluripotent stem cells and their differentiated progeny

The genetic modification of stem cells (SCs) is typically achieved using integrating vectors, whose potential integrative genotoxicity and propensity for epigenetic silencing during differentiation limit their application. The genetic modification of cells should provide sustainable levels of transgene expression, without compromising the viability of a cell or its progeny. We developed nonviral, nonintegrating, and autonomously replicating minimally sized DNA nanovectors to persistently genetically modify SCs and their differentiated progeny without causing any molecular or genetic damage. These DNA vectors are capable of efficiently modifying murine and human pluripotent SCs with minimal impact and without differentiation-mediated transgene silencing or vector loss. We demonstrate that these vectors remain episomal and provide robust and sustained transgene expression during self-renewal and targeted differentiation of SCs both in vitro and in vivo through embryogenesis and differentiation into adult tissues, without damaging their phenotypic characteristics.

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Nanovectors are used to engineer SCs efficiently, safely, and persistently

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Isogenic SC lines retain their capacity for self-renewal and pluripotency

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Nanovectors survive reprogramming and differentiation without loss or silencing

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Nanovectors are a universal genetic tool for the modification of any cell

RSPO2 inhibits BMP signaling to promote self-renewal in acute myeloid leukemia

Acute myeloid leukemia (AML) is a rapidly progressing cancer, for which chemotherapy remains standard treatment and additional therapeutic targets are requisite. Here, we show that AML cells secrete the stem cell growth factor R-spondin 2 (RSPO2) to promote their self-renewal and prevent cell differentiation. Although RSPO2 is a well-known WNT agonist, we reveal that it maintains AML self-renewal WNT independently, by inhibiting BMP receptor signaling. Autocrine RSPO2 signaling is also required to prevent differentiation and to promote self-renewal in normal hematopoietic stem cells as well as primary AML cells. Comprehensive datamining reveals that RSPO2 expression is elevated in patients with AML of poor prognosis. Consistently, inhibiting RSPO2 prolongs survival in AML mouse xenograft models. Our study indicates that in AML, RSPO2 acts as an autocrine BMP antagonist to promote cancer cell renewal and may serve as a marker for poor prognosis.

Abrogating GPT2 in triple-negative breast cancer inhibits tumor growth and promotes autophagy

Uncontrolled proliferation and altered metabolic reprogramming are hallmarks of cancer. Active glycolysis and glutaminolysis are characteristic features of these hallmarks and required for tumorigenesis. A fine balance between cancer metabolism and autophagy is a prerequisite of homeostasis within cancer cells. Here we show that glutamate pyruvate transaminase 2 (GPT2), which serves as a pivot between glycolysis and glutaminolysis, is highly upregulated in aggressive breast cancers, particularly the triple-negative breast cancer subtype. Abrogation of this enzyme results in decreased tricarboxylic acid cycle intermediates, which promotes the rewiring of glucose carbon atoms and alterations in nutrient levels. Concordantly, loss of GPT2 results in an impairment of mechanistic target of rapamycin complex 1 activity as well as the induction of autophagy. Furthermore, in vivo xenograft studies have shown that autophagy induction correlates with decreased tumor growth and that markers of induced autophagy correlate with low GPT2 levels in patient samples. Taken together, these findings indicate that cancer cells have a close network between metabolic and nutrient sensing pathways necessary to sustain tumorigenesis and that aminotransferase reactions play an important role in maintaining this balance.

Time-Resolved Profiling Reveals ATF3 as a Novel Mediator of Endocrine Resistance in Breast Cancer

Breast cancer is one of the leading causes of death for women worldwide. Patients whose tumors express Estrogen Receptor α account for around 70% of cases and are mostly treated with targeted endocrine therapy. However, depending on the degree of severity of the disease at diagnosis, 10 to 40% of these tumors eventually relapse due to resistance development. Even though recent novel approaches as the combination with CDK4/6 inhibitors increased the overall survival of relapsing patients, this remains relatively short and there is a urgent need to find alternative targetable pathways. In this study we profiled the early phases of the resistance development process to uncover drivers of this phenomenon. Time-resolved analysis revealed that ATF3, a member of the ATF/CREB family of transcription factors, acts as a novel regulator of the response to therapy via rewiring of central signaling processes towards the adaptation to endocrine treatment. ATF3 was found to be essential in controlling crucial processes such as proliferation, cell cycle, and apoptosis during the early response to treatment through the regulation of MAPK/AKT signaling pathways. Its essential role was confirmed in vivo in a mouse model, and elevated expression of ATF3 was verified in patient datasets, adding clinical relevance to our findings. This study proposes ATF3 as a novel mediator of endocrine resistance development in breast cancer and elucidates its role in the regulation of downstream pathways activities.

Cancer susceptibility of beta HPV49 E6 and E7 transgenic mice to 4-nitroquinoline 1-oxide treatment correlates with mutational signatures of tobacco exposure

We have previously showed that a transgenic (Tg) mouse model with cytokeratin 14 promoter (K14)-driven expression of E6 and E7 from beta-3 HPV49 in the basal layer of the epidermis and of the mucosal epithelia of the digestive tract (K14 HPV49 E6/E7 Tg mice) are highly susceptible to upper digestive tract carcinogenesis upon exposure to 4-nitroquinoline 1-oxide (4NQO). Using whole-exome sequencing, we show that in K14 HPV49 E6/E7 Tg mice, development of 4NQO-induced cancers tightly correlates with the accumulation of somatic mutations in cancer-related genes. The mutational signature in 4NQO-treated mice was similar to the signature observed in humans exposed to tobacco smoking and tobacco chewing. Similar results were obtained with K14 Tg animals expressing mucosal high-risk HPV16 E6 and E7 oncogenes. Thus, beta-3 HPV49 share some functional similarities with HPV16 in Tg animals.

A transplantable tumor model allowing investigation of NY-BR-1-specific T cell responses in HLA-DRB1*0401 transgenic mice

BACKGROUND

NY-BR-1 has been described as a breast cancer associated differentiation antigen with intrinsic immunogenicity giving rise to endogenous T and B cell responses. The current study presents the first murine tumor model allowing functional investigation of NY-BR-1-specific immune responses in vivo.

METHODS

A NY-BR-1 expressing tumor model was established in DR4tg mice based on heterotopic transplantation of stable transfectant clones derived from the murine H2 compatible breast cancer cell line EO771. Composition and phenotype of tumor infiltrating immune cells were analyzed by qPCR and FACS. MHC I binding affinity of candidate CTL epitopes predicted in silico was determined by FACS using the mutant cell line RMA-S. Frequencies of NY-BR-1 specific CTLs among splenocytes of immunized mice were quantified by FACS with an epitope loaded D^b-dextramer. Functional CTL activity was determined by IFNγ catch or IFNγ ELISpot assays and statistical analysis was done applying the Mann Whitney test. Tumor protection experiments were performed by immunization of DR4tg mice with replication deficient recombinant adenovirus followed by s.c. challenge with NY-BR-1 expressing breast cancer cells.

RESULTS

Our results show spontaneous accumulation of CD8⁺ T cells and F4/80⁺ myeloid cells preferentially in NY-BR-1 expressing tumors. Upon NY-BR-1-specific immunization experiments combined with in silico prediction and in vitro binding assays, the first NY-BR-1-specific H2-D^b-restricted T cell epitope could be identified. Consequently, flow cytometric analysis with fluorochrome conjugated multimers showed enhanced frequencies of CD8⁺ T cells specific for the newly identified epitope in spleens of immunized mice. Moreover, immunization with Ad.NY-BR-1 resulted in partial protection against outgrowth of NY-BR-1 expressing tumors and promoted intratumoral accumulation of macrophages.

CONCLUSION

This study introduces the first H2-D^b-resctricted CD8⁺ T cell epitope-specific for the human breast cancer associated tumor antigen NY-BR-1. Our novel, partially humanized tumor model enables investigation of the interplay between HLA-DR4-restricted T cell responses and CTLs within their joint attack of NY-BR-1 expressing tumors.

Functional Proteomics of Breast Cancer Metabolism Identifies GLUL as Responder during Hypoxic Adaptation

Hypoxia as well as metabolism are central hallmarks of cancer, and hypoxia-inducible factors (HIFs) and metabolic effectors are crucial elements in oxygen-compromised tumor environments. Knowledge of changes in the expression of metabolic proteins in response to HIF function could provide mechanistic insights into adaptation to hypoxic stress, tumorigenesis, and disease progression. We analyzed time-resolved alterations in metabolism-associated protein levels in response to different oxygen potentials across breast cancer cell lines. Effects on the cellular metabolism of both HIF-dependent and -independent processes were analyzed by reverse-phase protein array profiling and a custom statistical model. We revealed a strong induction of glucose transporter 1 (GLUT1) and lactate dehydrogenase A (LDHA) as well as reduced glutamate-ammonia ligase (GLUL) protein levels across all cell lines tested as consistent changes upon hypoxia induction. Low GLUL protein levels were correlated with aggressive molecular subtypes in breast cancer patient data sets and also with hypoxic tumor regions in a xenograft mouse tumor model. Moreover, low GLUL expression was associated with poor survival in breast cancer patients and with high HIF-1α-expressing patient subgroups. Our data reveal time-resolved changes in the regulation of metabolic proteins under oxygen-deprived conditions and elucidate GLUL as a strong responder to HIFs and the hypoxic environment.

Cancer cell specific inhibition of Wnt/β-catenin signaling by forced intracellular acidification

Use of the diabetes type II drug Metformin is associated with a moderately lowered risk of cancer incidence in numerous tumor entities. Studying the molecular changes associated with the tumor-suppressive action of Metformin we found that the oncogene SOX4, which is upregulated in solid tumors and associated with poor prognosis, was induced by Wnt/β-catenin signaling and blocked by Metformin. Wnt signaling inhibition by Metformin was surprisingly specific for cancer cells. Unraveling the underlying specificity, we identified Metformin and other Mitochondrial Complex I (MCI) inhibitors as inducers of intracellular acidification in cancer cells. We demonstrated that acidification triggers the unfolded protein response to induce the global transcriptional repressor DDIT3, known to block Wnt signaling. Moreover, our results suggest that intracellular acidification universally inhibits Wnt signaling. Based on these findings, we combined MCI inhibitors with H⁺ ionophores, to escalate cancer cells into intracellular hyper-acidification and ATP depletion. This treatment lowered intracellular pH both in vitro and in a mouse xenograft tumor model, depleted cellular ATP, blocked Wnt signaling, downregulated SOX4, and strongly decreased stemness and viability of cancer cells. Importantly, the inhibition of Wnt signaling occurred downstream of β-catenin, encouraging applications in treatment of cancers caused by APC and β-catenin mutations.

Aryl-hydrocarbon receptor-driven responses of innate lymphocytes

Innate Lymphoid Cells (ILCs) play significant roles during immune responses to infection at barrier sites and in the control of tissue damage and repair. In addition, ILCs have been involved in several pathologies, including exacerbated inflammation and carcinogenesis. However, understanding the contribution of distinct ILC subsets and modules of their regulation in both homeostasis and disease, is still incomplete. The Aryl-hydrocarbon Receptor (AhR) is a ligand-induced transcription factor that binds various exo- and endogenous polycyclic hydrocarbons and induces transcription of numerous target genes involved in development, cell differentiation and immune response. Here, we show that subsets of NKp46-expressing ILCs, including natural killer (NK) cells and helper ILC1, express AhR and respond to stimulation with AhR ligands. Exposure of NK cells to the tryptophan degradation product kynurenine, an endogenous AhR ligand, induced changes in global gene expression and primed NK cells for enhanced effector responses, including cytokine secretion and migration. In the context of diet-induced chronic liver damage, NK cells accumulated in the liver in an AhR-dependent manner. Conditional AhR deletion abolished NK cell accumulation, which correlated with reduced liver damage. In contrast to NK cells, liver resident helper ILC1 required AhR for the development and/or maintenance. In conclusion, the AhR is expressed by ILC1 subsets and differentially affects their development and effector responses. This might impact ILC1-driven responses in the context of chronic liver damage and could be of significance for liver tissue regeneration.

Beta HPV38 oncoproteins act with a hit-and-run mechanism in ultraviolet radiation-induced skin carcinogenesis in mice

Cutaneous beta human papillomavirus (HPV) types are suspected to be involved, together with ultraviolet (UV) radiation, in the development of non-melanoma skin cancer (NMSC). Studies in in vitro and in vivo experimental models have highlighted the transforming properties of beta HPV E6 and E7 oncoproteins. However, epidemiological findings indicate that beta HPV types may be required only at an initial stage of carcinogenesis, and may become dispensable after full establishment of NMSC. Here, we further investigate the potential role of beta HPVs in NMSC using a Cre-loxP-based transgenic (Tg) mouse model that expresses beta HPV38 E6 and E7 oncogenes in the basal layer of the skin epidermis and is highly susceptible to UV-induced carcinogenesis. Using whole-exome sequencing, we show that, in contrast to WT animals, when exposed to chronic UV irradiation K14 HPV38 E6/E7 Tg mice accumulate a large number of UV-induced DNA mutations, which increase proportionally with the severity of the skin lesions. The mutation pattern detected in the Tg skin lesions closely resembles that detected in human NMSC, with the highest mutation rate in p53 and Notch genes. Using the Cre-lox recombination system, we observed that deletion of the viral oncogenes after development of UV-induced skin lesions did not affect the tumour growth. Together, these findings support the concept that beta HPV types act only at an initial stage of carcinogenesis, by potentiating the deleterious effects of UV radiation.

Many epidemiological and biological findings support the hypothesis that beta HPV types cooperate with UV radiation in the induction of NMSC, the most common form of human cancer. We have previously shown that K14 HPV38 E6/E7 Tg mice, when exposed to long-term UV radiation, developed NMSC, whereas WT animals subjected to identical treatments did not develop any type of skin lesions. Here, we show that the high skin cancer susceptibility of these Tg animals tightly correlates with their tendency to accumulate UV-induced mutations in genes that are frequently mutated in human NMSC. Importantly, deletion of the HPV38 E6 and E7 genes in existing skin lesions did not affect the further growth of the cancer cells. Together, these findings support the model that beta HPV infection is a co-factor in skin carcinogenesis, facilitating the accumulation of the UV-induced DNA mutations.

Acetyl-CoA Carboxylase 1-Dependent Protein Acetylation Controls Breast Cancer Metastasis and Recurrence

Breast tumor recurrence and metastasis represent the main causes of cancer-related death in women, and treatments are still lacking. Here, we define the lipogenic enzyme acetyl-CoA carboxylase (ACC) 1 as a key player in breast cancer metastasis. ACC1 phosphorylation was increased in invading cells both in murine and human breast cancer, serving as a point of convergence for leptin and transforming growth factor (TGF) β signaling. ACC1 phosphorylation was mediated by TGFβ-activated kinase (TAK) 1, and ACC1 inhibition was indispensable for the elevation of cellular acetyl-CoA, the subsequent increase in Smad2 transcription factor acetylation and activation, and ultimately epithelial-mesenchymal transition and metastasis induction. ACC1 deficiency worsened tumor recurrence upon primary tumor resection in mice, and ACC1 phosphorylation levels correlated with metastatic potential in breast and lung cancer patients. Given the demonstrated effectiveness of anti-leptin receptor antibody treatment in halting ACC1-dependent tumor invasiveness, our work defines a "metabolocentric" approach in metastatic breast cancer therapy.

Subtype-specific differentiation of cardiac pacemaker cell clusters from human induced pluripotent stem cells

Background

Human induced pluripotent stem cells (hiPSC) harbor the potential to differentiate into diverse cardiac cell types. Previous experimental efforts were primarily directed at the generation of hiPSC-derived cells with ventricular cardiomyocyte characteristics. Aiming at a straightforward approach for pacemaker cell modeling and replacement, we sought to selectively differentiate cells with nodal-type properties.

Methods

hiPSC were differentiated into spontaneously beating clusters by co-culturing with visceral endoderm-like cells in a serum-free medium. Subsequent culturing in a specified fetal bovine serum (FBS)-enriched cell medium produced a pacemaker-type phenotype that was studied in detail using quantitative real-time polymerase chain reaction (qRT-PCR), immunocytochemistry, and patch-clamp electrophysiology. Further investigations comprised pharmacological stimulations and co-culturing with neonatal cardiomyocytes.

Results

hiPSC co-cultured in a serum-free medium with the visceral endoderm-like cell line END-2 produced spontaneously beating clusters after 10–12 days of culture. The pacemaker-specific genes HCN4, TBX3, and TBX18 were abundantly expressed at this early developmental stage, while levels of sarcomeric gene products remained low. We observed that working-type cardiomyogenic differentiation can be suppressed by transfer of early clusters into a FBS-enriched cell medium immediately after beating onset. After 6 weeks under these conditions, sinoatrial node (SAN) hallmark genes remained at high levels, while working-type myocardial transcripts (NKX2.5, TBX5) were low. Clusters were characterized by regular activity and robust beating rates (70–90 beats/min) and were triggered by spontaneous Ca²⁺ transients recapitulating calcium clock properties of genuine pacemaker cells. They were responsive to adrenergic/cholinergic stimulation and able to pace neonatal rat ventricular myocytes in co-culture experiments. Action potential (AP) measurements of cells individualized from clusters exhibited nodal-type (63.4%) and atrial-type (36.6%) AP morphologies, while ventricular AP configurations were not observed.

Conclusion

We provide a novel culture media-based, transgene-free approach for targeted generation of hiPSC-derived pacemaker-type cells that grow in clusters and offer the potential for disease modeling, drug testing, and individualized cell-based replacement therapy of the SAN.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0681-4) contains supplementary material, which is available to authorized users.

A Hepatic GAbp-AMPK Axis Links Inflammatory Signaling to Systemic Vascular Damage

Increased pro-inflammatory signaling is a hallmark of metabolic dysfunction in obesity and diabetes. Although both inflammatory and energy substrate handling processes represent critical layers of metabolic control, their molecular integration sites remain largely unknown. Here, we identify the heterodimerization interface between the α and β subunits of transcription factor GA-binding protein (GAbp) as a negative target of tumor necrosis factor alpha (TNF-α) signaling. TNF-α prevented GAbpα and β complex formation via reactive oxygen species (ROS), leading to the non-energy-dependent transcriptional inactivation of AMP-activated kinase (AMPK) β1, which was identified as a direct hepatic GAbp target. Impairment of AMPKβ1, in turn, elevated downstream cellular cholesterol biosynthesis, and hepatocyte-specific ablation of GAbpα induced systemic hypercholesterolemia and early macro-vascular lesion formation in mice. As GAbpα and AMPKβ1 levels were also found to correlate in obese human patients, the ROS-GAbp-AMPK pathway may represent a key component of a hepato-vascular axis in diabetic long-term complications.

Incipient Melanoma Brain Metastases Instigate Astrogliosis and Neuroinflammation

Malignant melanoma is the deadliest of skin cancers. Melanoma frequently metastasizes to the brain, resulting in dismal survival. Nevertheless, mechanisms that govern early metastatic growth and the interactions of disseminated metastatic cells with the brain microenvironment are largely unknown. To study the hallmarks of brain metastatic niche formation, we established a transplantable model of spontaneous melanoma brain metastasis in immunocompetent mice and developed molecular tools for quantitative detection of brain micrometastases. Here we demonstrate that micrometastases are associated with instigation of astrogliosis, neuroinflammation, and hyperpermeability of the blood-brain barrier. Furthermore, we show a functional role for astrocytes in facilitating initial growth of melanoma cells. Our findings suggest that astrogliosis, physiologically instigated as a brain tissue damage response, is hijacked by tumor cells to support metastatic growth. Studying spontaneous melanoma brain metastasis in a clinically relevant setting is the key to developing therapeutic approaches that may prevent brain metastatic relapse. Cancer Res; 76(15); 4359-71. ©2016 AACR.

Downregulation of the TGFβ Pseudoreceptor BAMBI in Non-Small Cell Lung Cancer Enhances TGFβ Signaling and Invasion

Non-small cell lung cancer (NSCLC) is characterized by early metastasis and has the highest mortality rate among all solid tumors, with the majority of patients diagnosed at an advanced stage where curative therapeutic options are lacking. In this study, we identify a targetable mechanism involving TGFβ elevation that orchestrates tumor progression in this disease. Substantial activation of this pathway was detected in human lung cancer tissues with concomitant downregulation of BAMBI, a negative regulator of the TGFβ signaling pathway. Alterations of epithelial-to-mesenchymal transition (EMT) marker expression were observed in lung cancer samples compared with tumor-free tissues. Distinct alterations in the DNA methylation of the gene regions encoding TGFβ pathway components were detected in NSCLC samples compared with tumor-free lung tissues. In particular, epigenetic silencing of BAMBI was identified as a hallmark of NSCLC. Reconstitution of BAMBI expression in NSCLC cells resulted in a marked reduction of TGFβ-induced EMT, migration, and invasion in vitro, along with reduced tumor burden and tumor growth in vivo In conclusion, our results demonstrate how BAMBI downregulation drives the invasiveness of NSCLC, highlighting TGFβ signaling as a candidate therapeutic target in this setting. Cancer Res; 76(13); 3785-801. ©2016 AACR.

A mammosphere formation RNAi screen reveals that ATG4A promotes a breast cancer stem-like phenotype

Introduction

Breast cancer stem cells are suspected to be responsible for tumour recurrence, metastasis formation as well as chemoresistance. Consequently, great efforts have been made to understand the molecular mechanisms underlying cancer stem cell maintenance. In order to study these rare cells in-vitro, they are typically enriched via mammosphere culture. Here we developed a mammosphere-based negative selection shRNAi screening system suitable to analyse the involvement of thousands of genes in the survival of cells with cancer stem cell properties.

Methods

We describe a sub-population expressing the stem-like marker CD44⁺/CD24^-/low in SUM149 that were enriched in mammospheres. To identify genes functionally involved in the maintenance of the sub-population with cancer stem cell properties, we targeted over 5000 genes by RNAi and tested their ability to grow as mammospheres. The identified candidate ATG4A was validated in mammosphere and soft agar colony formation assays. Further, we evaluated the influence of ATG4A expression on the sub-population expressing the stem-like marker CD44⁺/CD24^low. Next, the tumorigenic potential of SUM149 after up- or down-regulation of ATG4A was examined by xenograft experiments.

Results

Using this method, Jak-STAT as well as cytokine signalling were identified to be involved in mammosphere formation. Furthermore, the autophagy regulator ATG4A was found to be essential for the maintenance of a sub-population with cancer stem cell properties and to regulate breast cancer cell tumourigenicity in vivo.

Conclusion

In summary, we present a high-throughput screening system to identify genes involved in cancer stem cell maintenance and demonstrate its utility by means of ATG4A.

TSC22D4 is a molecular output of hepatic wasting metabolism

In mammals, proper storage and distribution of lipids in and between tissues is essential for the maintenance of energy homeostasis. Here, we show that tumour growth triggers hepatic metabolic dysfunction as part of the cancer cachectic phenotype, particularly by reduced hepatic very-low-density-lipoprotein (VLDL) secretion and hypobetalipoproteinemia. As a molecular cachexia output pathway, hepatic levels of the transcription factor transforming growth factor beta 1-stimulated clone (TSC) 22 D4 were increased in cancer cachexia. Mimicking high cachectic levels of TSC22D4 in healthy livers led to the inhibition of hepatic VLDL release and lipogenic genes, and diminished systemic VLDL levels under both normal and high fat dietary conditions. Liver-specific ablation of TSC22D4 triggered hypertriglyceridemia through the induction of hepatic VLDL secretion. Furthermore, hepatic TSC22D4 expression levels were correlated with the degree of body weight loss and VLDL hypo-secretion in cancer cachexia, and TSC22D4 deficiency rescued tumour cell-induced metabolic dysfunction in hepatocytes. Therefore, hepatic TSC22D4 activity may represent a molecular rationale for peripheral energy deprivation in subjects with metabolic wasting diseases, including cancer cachexia.

Tumor-microenvironment interactions studied by zonal transcriptional profiling of squamous cell lung carcinoma

Invasion is a critical step in lung tumor progression. The interaction between tumor cells and their surroundings may play an important role in tumor invasion and metastasis. To better understand the mechanisms of tumor invasion and tumor-microenvironment interactions in lung tumors, total RNA was isolated from the inner tumor, tumor invasion front, adjacent lung, and distant normal lung tissue from 17 patients with primary squamous cell lung carcinoma using punch-aided laser capture microdissection. Messenger RNA expression profiles were obtained by microarray analysis, and microRNA profiles were generated from eight of these samples using TaqMan Low Density Arrays. Statistical analysis of the expression data showed extensive changes in gene expression in the inner tumor and tumor front compared with the normal lung and adjacent lung tissue. Only a few genes were differentially expressed between tumor front and the inner tumor. Several genes were validated by immunohistochemistry. Evaluation of the microRNA data revealed zonal expression differences in nearly a fourth of the microRNAs analyzed. Validation of selected microRNAs by in situ hybridization demonstrated strong expression of hsa-miR-196a in the inner tumor; moderate expression of hsa-miR-224 in the inner tumor and tumor front, and strong expression of hsa-miR-650 in the adjacent lung tissue. Pathway analysis placed the majority of genes differentially expressed between tumor and nontumor cells in intrinsic processes associated with inflammation and extrinsic processes related to lymphocyte physiology. Genes differentially expressed between the inner tumor and the adjacent lung/normal lung tissue affected pathways of arachidonic acid metabolism and eicosanoid signaling.

Origin of pancreatic ductal adenocarcinoma from atypical flat lesions: a comparative study in transgenic mice and human tissues

Pancreatic ductal adenocarcinoma (PDAC) and its precursor lesions, pancreatic intraepithelial neoplasia (PanIN), display a ductal phenotype. However, there is evidence in genetically defined mouse models for PDAC harbouring a mutated kras under the control of a pancreas-specific promoter that ductal cancer might arise in the centroacinar-acinar region, possibly through a process of acinar-ductal metaplasia (ADM). In order to further elucidate this model of PDAC development, an extensive expression analysis and molecular characterization of the putative and already established (PanIN) precursor lesions were performed in the Kras(G12D/+) ; Ptf1a-Cre(ex1/+) mouse model and in human tissues, focusing on lineage markers, developmental pathways, cell cycle regulators, apomucins, and stromal activation markers. The results of this study show that areas of ADM are very frequent in the murine and human pancreas and represent regions of increased proliferation of cells with precursor potential. Moreover, atypical flat lesions originating in areas of ADM are the most probable precursors of PDAC in the Kras(G12D/+); Ptf1a-Cre(ex1/+) mice and similar lesions were also found in the pancreas of three patients with a strong family history of PDAC. In conclusion, PDAC development in Kras(G12D/+); Ptf1a-Cre(ex1/+) mice starts from ADM and a similar process might also take place in patients with a strong family history of PDAC.

Deleted in malignant brain tumors 1 is present in the vascular extracellular matrix and promotes angiogenesis

OBJECTIVE

Deleted in malignant brain tumors 1 (DMBT1) belongs to the scavenger receptor cysteine-rich superfamily of proteins and is implicated in innate immunity, cell polarity, and differentiation. Here we studied the role of DMBT1 in endothelial cells.

METHODS AND RESULTS

DMBT1 was secreted into the extracellular matrix (ECM) by endothelial cells in vitro and in situ and the presence of DMBT1 in the ECM increased endothelial cell adherence. Endothelial cell-derived DMBT1 associated with galectin-3 (coprecipitation), and human recombinant DMBT1 bound EGF, vascular endothelial growth factor and Delta-like (Dll) 4 (specific ELISAs). Compared to cells from wild-type mice, endothelial cells from DMBT1(-/-) mice demonstrated reduced migration, proliferation, and tube formation. In vivo recovery from hindlimb ischemia was attenuated in DMBT1(-/-) animals as was vascular endothelial growth factor -induced endothelial sprouting from isolated aortic rings; the latter response could be rescued by the addition of recombinant DMBT1. The Notch pathway is involved in multiple aspects of vascular development, including arterial-venous differentiation and we found that endothelial cells from DMBT1(-/-) mice expressed more EphrinB2 than cells from wild-type mice. Levels of Dll1, Dll4, Hes1, Hey1, and EphB4, on the other hand, were decreased.

CONCLUSIONS

Taken together, the results of this study indicate that DMBT1 functions as an important endothelium-derived ECM protein that is able to bind angiogenic factors and promote adhesion, migration, proliferation, and angiogenesis as well as vascular repair. Mechanistically, DMBT1 interacts with galectin-3 and modulates the Notch signaling pathway as well as the differential expression of ephrin-B2 and EphB4.

Hepatic deficiency in transcriptional cofactor TBL1 promotes liver steatosis and hypertriglyceridemia

The aberrant accumulation of lipids in the liver ("fatty liver") is tightly associated with several components of the metabolic syndrome, including type 2 diabetes, coronary heart disease, and atherosclerosis. Here we show that the impaired hepatic expression of transcriptional cofactor transducin beta-like (TBL) 1 represents a common feature of mono- and multigenic fatty liver mouse models. Indeed, the liver-specific ablation of TBL1 gene expression in healthy mice promoted hypertriglyceridemia and hepatic steatosis under both normal and high-fat dietary conditions. TBL1 deficiency resulted in inhibition of fatty acid oxidation due to impaired functional cooperation with its heterodimerization partner TBL-related (TBLR) 1 and the nuclear receptor peroxisome proliferator-activated receptor (PPAR) α. As TBL1 expression levels were found to also inversely correlate with liver fat content in human patients, the lack of hepatic TBL1/TBLR1 cofactor activity may represent a molecular rationale for hepatic steatosis in subjects with obesity and the metabolic syndrome.

Cyclooxygenase-2 controls energy homeostasis in mice by de novo recruitment of brown adipocytes

Obesity results from chronic energy surplus and excess lipid storage in white adipose tissue (WAT). In contrast, brown adipose tissue (BAT) efficiently burns lipids through adaptive thermogenesis. Studying mouse models, we show that cyclooxygenase (COX)-2, a rate-limiting enzyme in prostaglandin (PG) synthesis, is a downstream effector of beta-adrenergic signaling in WAT and is required for the induction of BAT in WAT depots. PG shifted the differentiation of defined mesenchymal progenitors toward a brown adipocyte phenotype. Overexpression of COX-2 in WAT induced de novo BAT recruitment in WAT, increased systemic energy expenditure, and protected mice against high-fat diet-induced obesity. Thus, COX-2 appears integral to de novo BAT recruitment, which suggests that the PG pathway regulates systemic energy homeostasis.

Localization of cyclo-oxygenase-2 in human recurrent colorectal cancer

AIM

The aim of this paper is to examine COX-2 expression in human recurrent colorectal carcinoma tissues using immunohistochemistry and quantative real-time PCR (qPCR).

METHODS

Colon and rectal specimens were obtained from 26 patients with recurrent colorectal carcinomas. We examined COX-2 expression in human recurrent colorectal carcinoma tissues using immunohistochemistry and quantative real-time PCR (qPCR).

RESULTS

In recurrent colorectal cancer a strong cytoplasmic and perinuclear staining of COX-2 was found. Moderate to strong immunosignals were detected in almost all of the carcinomas. We observed a strong specific staining of COX-2 in vascular endothelium. COX-2 immunoreactivity was also detected in stromal cells such as mononuclear cells, fibroblasts, and smooth muscle cells. The real-time PCR analyses demonstrated marked overexpression of the COX-2 gene in the cancer mucosa in concert with the immunohistochemistry data.

CONCLUSION

We investigated COX-2 expression at the level of its protein as well as its messenger RNA in a series of recurrent colorectal cancers. These observations give additional information about the possibility that COX-2 could be involved in tumor promotion during colorectal cancer progression.

Nuclear receptor cofactor receptor interacting protein 140 controls hepatic triglyceride metabolism during wasting in mice

In mammals, triglycerides (TG) represent the most concentrated form of energy. Aberrant TG storage and availability are intimately linked to the negative energy balance under severe clinical conditions, such as starvation, sepsis, or cancer cachexia. Despite its crucial role for energy homeostasis, molecular key determinants of TG metabolism remain enigmatic. Here we show that the expression of nuclear receptor cofactor receptor interacting protein (RIP) 140 was induced in livers of starved, septic, and tumor-bearing mice. Liver-specific knockdown of RIP140 led to increased hepatic TG release and alleviated hepatic steatosis in tumor-bearing, cachectic animals. Indeed, hepatic RIP140 was found to control the expression of lipid-metabolizing genes in liver.

CONCLUSION

By preventing the mobilization of hepatic TG stores, the induction of RIP140 in liver provides a molecular rationale for hepatic steatosis in starvation, sepsis, or cancer cachexia. Inhibition of hepatic RIP140 transcriptional activity might, thereby, provide an attractive adjunct scheme in the treatment of these conditions.

The glucocorticoid receptor controls hepatic dyslipidemia through Hes1

Aberrant accumulation of lipids in the liver ("fatty liver" or hepatic steatosis) represents a hallmark of the metabolic syndrome and is tightly associated with obesity, type II diabetes, starvation, or glucocorticoid (GC) therapy. While fatty liver has been connected with numerous abnormalities of liver function, the molecular mechanisms of fatty liver development remain largely enigmatic. Here we show that liver-specific disruption of glucocorticoid receptor (GR) action improves the steatotic phenotype in fatty liver mouse models and leads to the induction of transcriptional repressor hairy enhancer of split 1 (Hes1) gene expression. The GR directly interferes with Hes1 promoter activity, triggering the recruitment of histone deacetylase (HDAC) activities to the Hes1 gene. Genetic restoration of hepatic Hes1 levels in steatotic animals normalizes hepatic triglyceride (TG) levels. As glucocorticoid action is increased during starvation, myotonic dystrophy, and Cushing's syndrome, the inhibition of Hes1 through the GR might explain the fatty liver phenotype in these subjects.

RAGE signaling sustains inflammation and promotes tumor development

A broad range of experimental and clinical evidence has highlighted the central role of chronic inflammation in promoting tumor development. However, the molecular mechanisms converting a transient inflammatory tissue reaction into a tumor-promoting microenvironment remain largely elusive. We show that mice deficient for the receptor for advanced glycation end-products (RAGE) are resistant to DMBA/TPA-induced skin carcinogenesis and exhibit a severe defect in sustaining inflammation during the promotion phase. Accordingly, RAGE is required for TPA-induced up-regulation of proinflammatory mediators, maintenance of immune cell infiltration, and epidermal hyperplasia. RAGE-dependent up-regulation of its potential ligands S100a8 and S100a9 supports the existence of an S100/RAGE-driven feed-forward loop in chronic inflammation and tumor promotion. Finally, bone marrow chimera experiments revealed that RAGE expression on immune cells, but not keratinocytes or endothelial cells, is essential for TPA-induced dermal infiltration and epidermal hyperplasia. We show that RAGE signaling drives the strength and maintenance of an inflammatory reaction during tumor promotion and provide direct genetic evidence for a novel role for RAGE in linking chronic inflammation and cancer.

cAMP-dependent signaling regulates the adipogenic effect of n-6 polyunsaturated fatty acids

The effect of n-6 polyunsaturated fatty acids (n-6 PUFAs) on adipogenesis and obesity is controversial. Using in vitro cell culture models, we show that n-6 PUFAs was pro-adipogenic under conditions with base-line levels of cAMP, but anti-adipogenic when the levels of cAMP were elevated. The anti-adipogenic action of n-6 PUFAs was dependent on a cAMP-dependent protein kinase-mediated induction of cyclooxygenase expression and activity. We show that n-6 PUFAs were pro-adipogenic when combined with a high carbohydrate diet, but non-adipogenic when combined with a high protein diet in mice. The high protein diet increased the glucagon/insulin ratio, leading to elevated cAMP-dependent signaling and induction of cyclooxygenase-mediated prostaglandin synthesis. Mice fed the high protein diet had a markedly lower feed efficiency than mice fed the high carbohydrate diet. Yet, oxygen consumption and apparent heat production were similar. Mice on a high protein diet had increased hepatic expression of PGC-1alpha (peroxisome proliferator-activated receptor gamma coactivator 1alpha) and genes involved in energy-demanding processes like urea synthesis and gluconeogenesis. We conclude that cAMP signaling is pivotal in regulating the adipogenic effect of n-6 PUFAs and that diet-induced differences in cAMP levels may explain the ability of n-6 PUFAs to either enhance or counteract adipogenesis and obesity.

The cyclooxygenase-2-mediated prostaglandin signaling is causally related to epithelial carcinogenesis

Epidemiologic, pharmacologic, clinical, and experimental studies document the importance of prostaglandin (PG) signaling in cancer development, including non-melanoma skin cancer lesions in humans and mice. First of all, enzymes involved in PG biosynthesis, such as cyclooxygenase (COX)-2 and/or membrane prostaglandin E synthase (mPGES)-1, were found to be overexpressed in a wide range of premalignant and malignant epithelial tumors, including those of the skin, breast, esophagus, stomach, colorectum, pancreas, and bladder. On the other hand, 15-hydroxy-prostaglandin dehydrogenase (15-PGDH), which is involved in the degradation pathway of PG including PGE(2,) thus counteracting the activities of COX-2 and PGES, was found to be downregulated in human epithelial tumors, indicating a tumor suppressor activity of this enzyme. Most remarkably, genetic studies showed that mice, which are deficient in COX-2 and/or PGES are resistant to the development of cancer of skin, colon, and stomach. In contrast, the forced overexpression of COX-2 in proliferative compartments of simple or stratified epithelia such as skin epidermis, urinary bladder, mammary gland, and pancreas results in spontaneous hyperplasia and dysplasia in transgenic mice. In skin, the pathological changes are found to be due to an abnormal process of terminal differentiation, while in other tissues, hyperproliferation seems to be the main contributor to the pre-invasive neoplasms. Moreover, the COX-2 transgenic mouse lines are sensitized for cancer development.

The expression pattern of prostaglandin E synthase and EP receptor isoforms in normal mouse skin and preinvasive skin neoplasms

Prostaglandin (PG) E(2), the predominant PG in skin, accumulates in experimentally produced mouse skin tumors. PGE(2) induces proliferation of mouse keratinocytes in vitro, epidermal hyperplasia and dysplasia, a promoted epidermis phenotype, and angiogenesis in keratin 5 promoter (K5) cyclooxygenase (COX)-2-transgenic NMRI mouse skin in vivo. PGE(2) is synthesized by COX-catalysed oxygenation of arachidonic acid to PGH(2) and its conversion to PGE(2) by prostaglandin E synthase (PGES) isoforms. PGE(2) signals via PGE(2) receptor isoforms EP1-EP4. Here, we investigated the expression profiles of PGES and EP receptors in wild type NMRI mouse skin constitutively expressing COX-1 when compared with the hyperplastic/dysplastic skin of homozygous K5 COX-2-transgenic mice and papillomas of both genotypes, which, in addition to COX-1, overexpress COX-2. The three PGES are constitutively expressed in normal and transgenic skin independent of the COX expression status. In papillomas, the increased PGE(2) levels correlate with an increased expression of mPGES-1 and cPGES. All four EP receptors were expressed in normal and transgenic skin. Only EP3 was slightly increased in transgenic skin. In papillomas of both genotypes, the expression levels of EP1 and EP4 were low when compared with those in wild type back skin. EP2 was the predominant receptor in papillomas of wild type and transgenic mice. In papillomas of wild type mice EP3 levels were slightly elevated when compared with transgenic tumors. EP1 and EP2 were localized in basal keratinocytes, sebaceous glands and CD31-positive vessels. Thus, normal and preinvasive mouse skin express the complete protein repertoire for PGE(2) biosynthesis and signalling.

Tumor promotion as a target of cancer prevention

Tumor promotion is an essential process in multistage cancer development providing the conditions for clonal expansion and genetic instability of preneoplastic and premalignant cells. It is caused by a continuous disturbance of cellular signal transduction that results in an overstimulation of metabolic pathways along which mediators of cell proliferation and inflammation as well as genotoxic by-products are generated. Among such pathways the oxidative metabolism of arachidonic acid has turned out to be of utmost importance in tumor promotion. The aberrant overexpression of cyclooxygenase-2, an inducible enzyme of prostanoid synthesis and lipid peroxidation, is a characteristic feature of more than two-thirds of all human neoplasias, and the specific inhibition of this enzyme has been found to have a substantial chemopreventive effect in both animal models and man. The prostaglandins produced by COX-2 promote tumor development by stimulating cell proliferation and angiogenesis and by suppressing programmed cell death and immune defense. In mice, a COX-2 transgene fused with the keratin 5 promoter, which is constitutively active in the basal (proliferative) compartment of stratified and simple epithelia, causes a preneoplastic and premalignant phenotype in several organs. Among these organs, skin, mammary gland, urinary bladder, and pancreas have been investigated in more detail. Histologically and biochemically, the COX-2-dependent alterations resemble an autopromoted state that--as shown for skin and urinary bladder--strongly sensitizes the tissue for carcinogenesis. In transgenic animals COX-2 expression is not restricted to keratin 5-positive cells but is seen also in adjacent keratin 5-negative cells. This spreading of the COX-2 signal indicates a paracrine mechanism of autoamplification. While cancer chemoprevention by COX-2 inhibition is a rapidly developing field, much less is known about other pathways of unsaturated fatty acid metabolism, although some of them may play a role in carcinogenesis rivaling that of prostaglandin formation. Here an urgent demand for systematic research exists.

What are cyclooxygenases and lipoxygenases doing in the driver's seat of carcinogenesis?

Substantial evidence supports a functional role for cyclooxygenase- and lipoxygenase-catalyzed arachidonic and linoleic acid metabolism in cancer development. Genetic intervention studies firmly established cause-effect relations for cyclooxygenase-2, but cyclooxygenase-1 may also be involved. In addition, pharmacologic cyclooxygenase inhibition was found to suppress carcinogenesis in both experimental mouse models and several cancers in humans. Arachidonic acid-derived eicosanoid or linoleic acid-derived hydro[peroxy]fatty acid signaling are likely to be involved impacting fundamental biologic phenomena as diverse as cell growth, cell survival, angiogenesis, cell invasion, metastatic potential and immunomodulation. However, long chain unsaturated fatty acid oxidation reactions indicate antipodal functions of distinct lipoxygenase isoforms in carcinogenesis, i.e., the 5- and platelet-type 12-lipoxygenase exhibit procarcinogenic activities, while 15-lipoxygenase-1 and 15-lipoxygenase-2 may suppress carcinogenesis.

Preinvasive duct-derived neoplasms in pancreas of keratin 5-promoter cyclooxygenase-2 transgenic mice

BACKGROUND & AIMS

Basic research aimed at a better understanding of pancreatic carcinogenesis and improving the treatment of this disease is crucial because the majority of pancreatic cancers are highly aggressive and therapeutically nonaccessible. Cyclooxygenase (COX)-2, which is a key enzyme of prostaglandin (PG) biosynthesis, is overexpressed in around 75% of human carcinomas including those of the pancreas.

METHODS

The pathologic changes of transgenic mouse pancreas with keratin 5-promoter-driven expression and activity of COX-2 were characterized.

RESULTS

Aberrant expression of COX-2 in a few ductal cells and COX-2-mediated PG synthesis in the transgenic mice resulted in keratin 19- and mucin-positive intraductal papillary mucinous neoplasm- and pancreatic intraepithelial neoplasia-like structures, characterized by an increased proliferation index and serous cystadenomas. Moreover, Ras activation was enhanced and the HER-2/Neu receptor was overexpressed. Loss of acini, fibrosis, and inflammation were pronounced. Feeding a COX-2-selective inhibitor to the transgenic mice suppressed the accumulation of PG and the phenotype. The changes resemble the human disease in which COX-2 was overexpressed consistently.

CONCLUSIONS

We present strong evidence for a causal relationship between aberrant COX-2 overexpression and COX-2-mediated PG synthesis and the development of serous cystadenoma, intraductal papillary mucinous, and pancreatic intraepithelial neoplasms. This model offers the unique possibility of identifying molecular pathways leading to the formation and malignant progression of the various types of preinvasive lesions of pancreatic adenocarcinomas that show different dismal outcomes.

Differential protein expression in the epidermis of wild-type and COX-2 transgenic mice

Cyclooxygenases (COX) 1 and 2 are the key enzymes of prostaglandin biosynthesis. Like in many tissues, in adult skin COX-1 is a constitutive 'housekeeping' enzyme, while COX-2 is induced transiently in stress situations such as tissue damage and regeneration. In human skin carcinomas and corresponding early-stage cancer lesions, permanent COX-2 expression and activation is a consistent feature. Knockout and various transgenic approaches and pharmacologic studies show strong evidence for a cause-and-effect relationship between the aberrant COX-2 activation and tumor formation. In skin epidermis, keratin 5 promoter-driven overexpression of COX-2 caused hyperplasia and dysplasia, and sensitized skin for carcinogenesis. Therefore, this model offers the unique possibility of identifying COX-2-dependent and prostaglandin-mediated molecular pathways leading to the formation and malignant progression of early-stage cancer lesions.

Enzymes involved in the biosynthesis of leukotriene B4 and prostaglandin E2 are active in sebaceous glands

The expression of enzymes involved in leukotriene and prostaglandin signalling pathways, of interleukins 6 and 8 and of peroxisome proliferator-activated receptors in sebaceous glands of acne-involved facial skin was compared with those of non-involved skin of acne patients and of healthy individuals. Moreover, 5-lipoxygenase and leukotriene A(4) hydrolase were expressed at mRNA and protein levels in vivo and in SZ95 sebocytes in vitro (leukotriene A(4) hydrolase > 5-lipoxygenase), while 15-lipoxygenase-1 was only detected in cultured sebocytes. Cyclooxygenase-1 and cyclooxygenase-2 were also present. Peroxisome proliferator-activated receptors were constitutively expressed. Enhanced 5-lipoxygenase, cyclooxygenase 2 and interleukin 6 expression was detected in acne-involved facial skin. Arachidonic acid stimulated leukotriene B(4) and interleukin 6 release as well as prostaglandin E(2) biosynthesis in SZ95 sebocytes, induced abundant increase in neutral lipids and down-regulated peroxisome proliferator-activated receptor-alpha, but not receptor-gamma1 mRNA levels, which were the predominant peroxisome proliferator-activated receptor isotypes in SZ95 sebocytes. In conclusion, human sebocytes possess the enzyme machinery for functional leukotriene and prostaglandin pathways. A comprehensive link between inflammation and sebaceous lipid synthesis is provided.

Inhibition of cell proliferation by bacterial lipopolysaccharides in TLR4-positive epithelial cells: independence of nitric oxide and cytokine release

Phylogenetically conserved toll-like receptors (TLR) recognize "pathogen-associated molecular patterns". Upon binding of ligands, TLR initiate innate immune response in immune and most likely epithelial cells. The TLR4 isoform is considered as a lipopolysaccharide (LPS) receptor. As shown here, a rat-tongue-derived epithelial cell line RTE2 expressed TLR4 mRNA and functional protein. LPS-treated RTE2 cells responded with the transient expression of inducible nitric oxide synthase (iNOS), an effector protein of TLR4 involved in the innate immune defense of monocytes. iNOS induction occurred along a nuclear factor-kappaB (NF-kappab)-dependent pathway and correlated with the increased production of NO. Moreover, LPS and lipid A were potent inhibitors of proliferation of RTE2 cells, of mouse keratinocytes, and mouse epidermis in vivo. The inhibition depended on lipid A structure, i.e., it was related to the endotoxin activity of LPS and at least in vitro was in part mediated by NF-kappaB. C57Bl/10 ScCr mice, lacking a functional TLR4, did not respond with growth inhibition, strongly suggesting a TLR4-mediated effect. RTE2 proliferation was also inhibited by transforming growth factor beta (TGFbeta) and tumor necrosis factor alpha (TNFalpha), whereas interferon gamma (IFNgamma) was a weak inhibitor. But the growth-inhibitory effect of LPS on RTE2 cells was not mediated by TNFalpha, TGFbeta, or NO. It is concluded that besides induction of innate immune responses, LPS specifically induces growth arrest in epithelial tongue cells and keratinocytes in vitro and in mouse epidermis in a TLR4-dependent but cytokine- and NO-independent manner.

Cystic duct dilatations and proliferative epithelial lesions in mouse mammary glands upon keratin 5 promoter-driven overexpression of cyclooxygenase-2

Expression and pharmacological studies support a contribution of cyclooxygenase (COX)-2 to mammary gland tumorigenesis. In a recent transgenic study, mouse mammary tumor virus promoter-driven COX-2 expression in mouse mammary glands was shown to result in alveolar hyperplasia, dysplasia, and carcinomas after multiple rounds of pregnancy and lactation. In the study presented here, the effects of constitutive COX-2 overexpression in keratin 5-positive myoepithelial and luminal cells, driven by the keratin 5 promoter in a hormone-independent manner, was investigated. In nulliparous female mice, aberrant COX-2 overexpression correlated with increased prostaglandin (PG) E(2) levels and caused cystic duct dilatations, adenosis, and fibrosis whereas carcinomas developed rarely. This phenotype depended on COX-2-mediated PGE(2) synthesis and correlated with increased expression of proliferation-associated Ki67 in epithelial cells. No changes in the expression of apoptosis-related Bcl-2, caspase 3, or p53 were observed. Hyperproliferation of the mammary gland epithelial cells was associated with increased aromatase mRNA levels in this tissue. The spontaneous pathologies bear analogies to the human breast with fibrocystic changes. Intriguingly, strong COX-2 expression was observed in fibrocystic changes, as compared to low expression in normal breast epithelium. These results show for the first time that aberrant COX-2 expression contributes to the development of fibrocystic changes (FC), indicating that COX-2 and COX-2-mediated PG synthesis represent potential targets for the therapy of this most frequent benign disorder of the human breast.

Transitional Cell Hyperplasia and Carcinomas in Urinary Bladders of Transgenic Mice with Keratin 5 Promoter-Driven Cyclooxygenase-2 Overexpression

The inducible form of cyclooxygenase (COX), COX-2, is up-regulated in many epithelial cancers and its prostaglandin products increase proliferation, enhance angiogenesis, and inhibit apoptosis in several tissues. Pharmacologic inhibition and genetic deletion studies showed a marked reduction of tumor development in colon and skin. COX-2 has also been strongly implicated in urinary bladder cancer primarily by studies with nonselective COX- and COX-2-selective inhibitors. We now show that forced expression of COX-2, under the control of a keratin 5 promoter, is sufficient to cause transitional cell hyperplasia (TCH) in 17% and 75% of the heterozygous and homozygous transgenic lines, respectively, in an age-dependent manner. TCH was strongly associated with inflammation, primarily nodules of B lymphocytes; some T cells and macrophage infiltration were also observed. Additionally, transitional cell carcinoma was observed in approximately 10% of the K5.COX-2 transgenic mice; no TCH or transitional cell carcinoma was observed in wild-type bladders. Immunohistochemistry for vascular proliferation and vascular endothelial growth factor showed significant increases above that in wild-type urinary bladders. Our results suggest that overexpression of COX-2 is sufficient to cause hyperplasia and carcinomas in the urinary bladder. Therefore, inhibition of COX-2 should continue to be pursued as a potential chemopreventive and therapeutic strategy.