Abstract 109: The Chromatin Remodeling Protein Brg1 Regulates Adventitial Progenitor Cell Myofibroblast Differentiation And Pathological Vascular Remodeling

Cardiovascular diseases lead to long-term stiffening of arteries and small vessels. The vascular wall contains several cellular populations that coordinate to maintain vessel homeostasis and induce vascular remodeling in disease states. We identified a population of smooth muscle-derived progenitor cells that reside in the adventitial layer (AdvSca1-SM cells) that drive vascular fibrosis after acute vascular injury. AdvSca1-SM cells can differentiate into myofibroblasts and secrete numerous pro-remodeling factors including extracellular matrix proteins and pro-inflammatory cytokines. While the response of AdvSca1-SM cells to vascular injury has been studied, the epigenetic changes that influence their differentiation towards myofibroblasts is poorly understood. We observed Brahma-related gene 1 (Brg1), a highly conserved chromatin remodeling ATPase, is upregulated in AdvSca1-SM cells in response to vascular injury and may be a key factor in regulating gene expression to influence AdvSca1-SM differentiation. We hypothesize that Brg1 induces expression of gene sets associated with remodeling and fibrosis and ultimately drives AdvSca1-SM cell differentiation towards pathologic myofibroblasts.

Results: Carotid arteries from mice subject to carotid ligation exhibit decreased perivascular collagen deposition, smaller neointima, decreased adventitial expansion, decreased numbers of alpha-actin positive AdvSca1-SM cells, and fewer infiltrating macrophages when treated with the pharmacological Brg1 bromodomain inhibitor PFI-3 as compared to mice that received vehicle control. In a cell culture system, TGF-β induces AdvSca1-SM cells to express myofibroblast-specific genes, including alpha actin and periostin, and demonstrate enhanced contractile function in collagen contraction assays. PFI-3 blocks TGF-β induced myofibroblast gene expression and dampens contractile function. Gene Ontology analysis reveals the top 100 TGF-β inducible genes blunted by PFI-3 are related to fibrosis and extracellular matrix signaling. In conclusion, these results suggest Brg1 is a major regulator of vascular remodeling and fibrosis and may be a targetable protein to help people who suffer from disease-related vascular stiffening.

Abstract 208: The Chromatin Remodeling Protein Brg1 Regulates Adventitial Progenitor Cell Myofibroblast Differentiation And Pathological Vascular Remodeling

Cardiovascular diseases lead to long-term stiffening of arteries and small vessels. The vascular wall contains several cellular populations that coordinate to maintain vessel homeostasis and induce vascular remodeling in disease states. We identified a population of smooth muscle-derived progenitor cells that reside in the adventitial layer (AdvSca1-SM cells) that drive vascular fibrosis after acute vascular injury. AdvSca1-SM cells can differentiate into myofibroblasts and secrete numerous pro-remodeling factors including extracellular matrix proteins and pro-inflammatory cytokines. While the response of AdvSca1-SM cells to vascular injury has been studied, the epigenetic changes that influence their differentiation towards myofibroblasts is poorly understood. We observed Brahma-related gene 1 (Brg1), a highly conserved chromatin remodeling ATPase, is upregulated in AdvSca1-SM cells in response to vascular injury and may be a key factor in regulating gene expression to influence AdvSca1-SM differentiation. We hypothesize that Brg1 induces expression of gene sets associated with remodeling and fibrosis and ultimately drives AdvSca1-SM cell differentiation towards pathologic myofibroblasts.

Results: Carotid arteries from mice subject to carotid ligation exhibit decreased perivascular collagen deposition, smaller neointima, decreased adventitial expansion, decreased numbers of alpha-actin positive AdvSca1-SM cells, and fewer infiltrating macrophages when treated with the pharmacological Brg1 bromodomain inhibitor PFI-3 as compared to mice that received vehicle control. In a cell culture system, TGF-β induces AdvSca1-SM cells to express myofibroblast-specific genes, including alpha actin and periostin, and demonstrate enhanced contractile function in collagen contraction assays. PFI-3 blocks TGF-β induced myofibroblast gene expression and dampens contractile function. Gene Ontology analysis reveals the top 100 TGF-β inducible genes blunted by PFI-3 are related to fibrosis and extracellular matrix signaling. In conclusion, these results suggest Brg1 is a major regulator of vascular remodeling and fibrosis and may be a targetable protein to help people who suffer from disease-related vascular stiffening.

15-Lipoxygenase worsens renal fibrosis, inflammation, and metabolism in a murine model of ureteral obstruction

15-Lipoxygenase (15-LO) is a nonheme iron-containing dioxygenase that has both pro- and anti-inflammatory roles in many tissues and disease states. 15-LO is thought to influence macrophage phenotype, and silencing 15-LO reduces fibrosis after acute inflammatory triggers. The goal of the present study was to determine whether altering 15-LO expression influences inflammation and fibrogenesis in a murine model of unilateral ureteral obstruction (UUO). C57BL/6J mice, 15-LO knockout (Alox15-/-) mice, and 15-LO transgenic overexpressing (15LOTG) mice were subjected UUO, and kidneys were analyzed at 3, 10, and 14 days postinjury. Histology for fibrosis, inflammation, cytokine quantification, flow cytometry, and metabolomics were performed on injured tissues and controls. PD146176, a specific 15-LO inhibitor, was used to complement experiments involving knockout animals. Compared with wild-type animals undergoing UUO, Alox15-/- mouse kidneys had less proinflammatory, profibrotic message along with less fibrosis and macrophage infiltration. PD146176 inhibited 15-LO and resulted in reduced fibrosis and macrophage infiltration similar to Alox15-/- mice. Flow cytometry revealed that Alox15-/- UUO-injured kidneys had a dynamic change in macrophage phenotype, with an early blunting of CD11bHiLy6CHi "M1" macrophages and an increase in anti-inflammatory CD11bHiLy6CInt "M2c" macrophages and reduced expression of the fractalkine receptor chemokine (C-X3-C motif) receptor 1. Many of these findings were reversed when UUO was performed on 15LOTG mice. Metabolomics analysis revealed that wild-type kidneys developed a glycolytic shift postinjury, while Alox15-/- kidneys exhibited increased oxidative phosphorylation. In conclusion, 15-LO manipulation by genetic or pharmacological means induces dynamic changes in the inflammatory microenvironment in the UUO model and appears to be critical in the progression of UUO-induced fibrosis.NEW & NOTEWORTHY 15-Lipoxygenase (15-LO) has both pro- and anti-inflammatory functions in leukocytes, and its role in kidney injury and repair is unexplored. Our study showed that 15-LO worsens inflammation and fibrosis in a rodent model of chronic kidney disease using genetic and pharmacological manipulation. Silencing 15-LO promotes an increase in M2c-like wound-healing macrophages in the kidney and alters kidney metabolism globally, protecting against anaerobic glycolysis after injury.

Abstract MP12: The Epigenetic Remodeling Protein Brg1 Is Implicated In Vascular Progenitor Cell Contribution To Pathological Vascular Remodeling And Fibrosis

Vascular fibrosis is an irreversible consequence of vascular remodeling that ensues in many cardiovascular diseases. Currently, no treatments are available to target chronic vascular fibrosis. We identified a unique population of multipotent smooth muscle-derived Sca1+ progenitor cells that reside in the vascular adventitia (AdvSca1-SM cells). While AdvSca1-SM cells can differentiate into mature smooth muscle cells (SMCs) and repair the vessel wall, AdvSca1-SM cells also have the potential to differentiate into myofibroblasts and greatly contribute to vascular fibrosis after acute vascular injury. The epigenetic remodeling protein Brg1 is upregulated in AdvSca1-SM cells in the setting of vascular injury, but how Brg1 influences AdvSca1-SM differentiation is unknown. Using in vitro and in vivo approaches, our goal was to define the role of Brg1 in AdvSca1-SM cells. We hypothesized that Brg1 regulates chromatin density around genetic loci associated with fibrosis to preferentially drive AdvSca1-SM cell differentiation towards pathologic myofibroblasts. Further, we hypothesized that pharmacologic inhibition of Brg1 will disrupt AdvSca1-SM differentiation into myofibroblasts and attenuate vascular fibrosis. Mice subjected to carotid ligation and treated with the highly specific Brg1 inhibitor, PFI-3, exhibited decreased vascular fibrosis, reduced neointima, and decreased adventitial expansion of AdvSca1-SM cells as compared to mice that received vehicle control. This in vivo data was complemented by in vitro studies where cultured AdvSca1-SM cells stimulated with TGF-β expressed myofibroblast genes including αSMA and periostin, and co-treatment with PFI-3 blocked TGF-β-induced myofibroblast marker expression at the mRNA and protein level. In conclusion, these results support the hypothesis that Brg1 is a major regulator of AdvSca1-SM myofibroblast differentiation and may represent a novel targetable protein to treat vascular fibrosis.

Abstract MP28: The Bet Bromodomain Inhibitor, (+)-JQ1, Inhibits Neointima Formation Following Acute Vascular Injury Via Pten Upregulation

The primary aim of this work was to identify compounds that upregulate phosphatase and tensin homolog (PTEN) expression in smooth muscle cells (SMCs), with the expectation that PTEN upregulation would inhibit pathological vascular remodeling by promoting SMC homeostasis. Our recent work demonstrated that PTEN is an important regulator of SMC phenotype. SMC-specific PTEN deletion promotes spontaneous vascular remodeling and PTEN loss correlates with increased atherosclerotic lesion severity in human coronary arteries. In mice, PTEN overexpression reduces plaque area and preserves SMC contractile protein expression in atherosclerosis and blunts Angiotensin-II-induced pathological vascular remodeling, suggesting that pharmacologic PTEN upregulation could be a novel therapeutic approach to treat vascular disease. Currently, there are few known pharmacologic inducers of PTEN, however, we have shown that (+)-JQ1, which targets the epigenetic reader protein, Brd4, directly activates the PTEN promoter to drive PTEN expression. Mechanistically, our findings suggest that Brd4 inhibition results in p300-mediated hyper-acetylation of the PTEN promoter to increase PTEN transcriptional activity. Administration of (+)-JQ1 or SMC-specific Brd4 deletion inhibited neointima formation following acute carotid artery injury in mice. Using SMC-specific PTEN depletion both in vitro and in vivo, we showed that the observed anti-remodeling, anti-inflammatory effects were PTEN-dependent. Furthermore, we tested the effects of (+)-JQ1 on macrophage polarization, as systemic drug delivery could potentially modulate the phenotype of other resident vascular cells, including macrophages. We found that (+)-JQ1 inhibited bone marrow-derived macrophage polarization towards a pro-inflammatory phenotype, which is notable because vascular inflammation driven by SMC-macrophage cross-talk is known to promote neointima development. Importantly, our findings may hold direct clinical relevance, as BET bromodomain inhibitors related to (+)-JQ1 are currently undergoing clinical trials. These results are significant because they indicate that targeting PTEN upregulation in SMCs is a completely novel approach to inhibit vascular remodeling.

Activation of PPARγ in myeloid cells promotes lung cancer progression and metastasis

PPARγ activators inhibit cancer cell growth. However the role of these agents in progression/metastasis is not well-defined. Using an orthotopic model of lung cancer, we showed that pioglitazone accelerated progression/metastasis through affects on macrophages. This suggests that potential therapeutic agents may have opposing effects on cancer in different cells.

STAT3 Modulation of Regulatory T Cells in Response to Radiation Therapy in Head and Neck Cancer

BACKGROUND

Radioresistance represents a major problem in the treatment of head and neck cancer (HNC) patients. To improve response, understanding tumor microenvironmental factors that contribute to radiation resistance is important. Regulatory T cells (Tregs) are enriched in numerous cancers and can dampen the response to radiation by creating an immune-inhibitory microenvironment. The purpose of this study was to investigate mechanisms of Treg modulation by radiation in HNC.

METHODS

We utilized an orthotopic mouse model of HNC. Anti-CD25 was used for Treg depletion. Image-guided radiation was delivered to a dose of 10 Gy. Flow cytometry was used to analyze abundance and function of intratumoral immune cells. Enzyme-linked immunosorbent assay was performed to assess secreted factors. For immune-modulating therapies, anti-PD-L1, anti-CTLA-4, and STAT3 antisense oligonucleotide (ASO) were used. All statistical tests were two-sided.

RESULTS

Treatment with anti-CD25 and radiation led to tumor eradication (57.1%, n = 4 of 7 mice), enhanced T-cell cytotoxicity compared with RT alone (CD4 effector T cells [Teff]: RT group mean = 5.37 [ 0.58] vs RT + αCD25 group mean =10.71 [0.67], P = .005; CD8 Teff: RT group mean = 9.98 [0.81] vs RT + αCD25 group mean =16.88 [2.49], P = .01) and induced tumor antigen-specific memory response (100.0%, n = 4 mice). In contrast, radiation alone or when combined with anti-CTLA4 did not lead to durable tumor control (0.0%, n = 7 mice). STAT3 inhibition in combination with radiation, but not as a single agent, improved tumor growth delay, decreased Tregs, myeloid-derived suppressor cells, and M2 macrophages and enhanced effector T cells and M1 macrophages. Experiments in nude mice inhibited the benefit of STAT3 ASO and radiation.

CONCLUSION

We propose that STAT3 inhibition is a viable and potent therapeutic target against Tregs. Our data support the design of clinical trials integrating STAT3 ASO in the standard of care for cancer patients receiving radiation.

Abstract B51: MAPK regulation of an innate immune response in KRAS-mutant lung adenocarcinoma

Mutations in the KRAS oncogene are frequent in lung adenocarcinomas (LUADs). Unfortunately, KRAS lacks a pharmacologically available inhibitor for precision oncology. Immunotherapies have recently become available and are now FDA approved for LUAD, although only a subset of patients show clinical benefit. Recent work has unveiled biomarkers of immunotherapy response and include interferon γ (IFNγ) and T-cell inflamed gene signatures, suggesting that active IFN signaling within the tumor microenvironment (TME) and infiltration of antitumor T-cells are necessary for response. Thus, strategies that increase T-cell inflammation within LUAD are predicted to broaden immunotherapy response. Using human and murine KRAS-mutant LUAD cell lines, we demonstrated variable transcriptional induction of an innate immune response after 1-2-day treatment with the MEK inhibitor, trametinib. In particular, murine lung cancer cell lines 832B and LKR10 demonstrated induction of CXCL10 transcript, an innate immune chemotactic factor for effector T cells and natural killer (NK) cells. This variable induction was also seen at the protein level with CXCL10 protein increasing 8- and 4-fold, in 832B and LKR10 respectively, after a 3-day treatment. Human KRAS-mutant LUAD cell line, H358, exhibited a 17-fold induction in CXCL10 protein secretion following a 3-day treatment with trametinib. The mechanism(s) by which MAPK inhibition leads to induction of innate immune signaling remains ill defined. IKK-16, an inhibitor of IKKα/β and downstream NF-kB signaling, but not the JAK inhibitor, ruxolitinib, blocked trametinib-induced CXCL10 secretion in H358 cells. While the data support a central role for NF-kB signaling in this response, the complexity of innate immune signaling and IKK-NF-kB pathways prevents their full dissection with traditional candidate-based approaches. Therefore, we have initiated a functional genomics approach using CRISPR/Cas9-mediated tagging of the CXCL10gene in human lung cancer cell lines. While H358 cells are in process, we successfully generated EGFR mutant PC9 cells that bear GFP-tagged CXC10 and exhibit strong induction of CXCL10-GFP when treated with the 3rd-generation EGFR inhibitor, AZD9291. These CXCL10-GFP tagged cell lines will be deployed in functional genomics experiments to define in an unbiased manner signal pathway and transcription factor components that mediate oncogene-targeted drug-induced CXCL10 induction. A full elucidation of the mechanism by which oncogene pathways suppress innate immune pathways and CXCL10 expression may highlight novel ways in which to enhance antitumor inflammation and increase the depth of the therapeutic response to oncogene-targeted drugs.

Citation Format: Daniel Sisler, Sean Korpela, Natalia Gurule, Trista Hinz, Lindsay Marek, Bonnie Bullock, Howard Li, Molishree Joshi, Colin Sempeck, Raphael Nemenoff, Lynn Heasley. MAPK regulation of an innate immune response in KRAS-mutant lung adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr B51.

The effect of MEK1/2 inhibitors on cisplatin-induced acute kidney injury (AKI) and cancer growth in mice

In a clinically-relevant model of 4 week, low-dose cisplatin-induced AKI, mice were injected subcutaneously with non small cell lung cancer (NSCLC) cells that harbor an activating Kirsten rat sarcoma viral oncogene homolog (KRAS)^G12V mutation. Phospho extracellular signal-regulated kinase1/2 (pERK1/2) expression in kidney and tumors was decreased by the MEK1/2 inhibitors, U0126 and trametinib, that potently inhibit pERK1/2. U0126 resulted in a significant improvement in kidney function, acute tubular necrosis (ATN) and tubular cell apoptosis in mice with AKI. Genes that were significantly decreased by U0126 were heat shock protein 1, cyclin-dependent kinase 4 (CDK4) and stratifin (14-3-3σ). U0126 resulted in a significant decrease in tumor weight and volume and significantly increased the chemotherapeutic effect of cisplatin. Trametinib, a MEK1/2 inhibitor that is FDA-approved for the treatment of cancer, did not result in functional protection against AKI or worse AKI, but dramatically decreased tumor growth more than cisplatin. Smaller tumors in cisplatin or MEK1/2 inhibitor-treated mice were not related to changes in microtubule-associated proteins 1A/1B light chain 3B (LC3-II), p62, cleaved caspase-3, granzyme B, or programmed death-ligand 1 (PD-L1). In summary, despite ERK inhibition by both U0126 and trametinib, only U0126 protected against AKI suggesting that the protection against AKI by U0126 was due to an off-target effect independent of ERK inhibition. The effect of U0126 to decrease AKI may be mediated by inhibition of heat shock protein 1, CDK4 or stratifin (14-3-3σ). Trametinib was more effective than cisplatin in decreasing tumor growth, but unlike cisplatin, trametinib did not cause AKI.

Regulatory T cells mediate resistance to radiotherapy in head and neck squamous cell carcinoma

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Background: Head and neck tumors are highly enriched in regulatory T cells which dampen the response to radiotherapy by creating an immune-inhibitory microenvironment. We explored mechanisms of Treg infiltration and assessed their modulation by RT in murine models of HNSCC. Methods: Mechanisms of Treg infiltration were investigated in murine HNSCC tumors using whole genome sequencing and flow cytometry. Mice were treated with anti-CTLA-4, anti-CD-25 and/or anti-PD-L1 alone and in combination with RT. Tumor growth and survival were assessed. Flow cytometry was used to assess phenotypic and functional changes in intratumoral T cell populations. Multiplex ELISA was performed for assessment of cytokines. RNA Sequencing was performed to interrogate mechanisms of response and resistance to treatment. Results: Treatment with anti-CD-25 concurrently with RT led to significant tumor growth delay, enhanced T cell cytotoxicity, decreased Tregs and improved survival. In contrast CTLA-4 blockade did not affect tumor growth or survival. Treg depletion induced an influx of CD8 and CD4 T cells when combined with RT. In addition, Treg depletion in combination with RT transformed myeloid populations decreasing M2 macrophages and MDSCs and increasing M1 macrophages. Mechanistically, tumors secrete CCL20, a potent Treg chemoattractant responsible for creating a highly immunuosuppressive tumor microenvironment and potentially responsible for treatment resistance. Conclusions: These data reveal a critical role for regulatory T cells in mediating resistance to RT. Targeted depletion of Tregs represents an important mechanism of sensitizing tumors to RT. Our data support the design of clinical trials integrating targeted Treg inhibitors in the standard of care for cancer patients receiving RT.

Inhibition of 5-lipoxygenase decreases renal fibrosis and progression of chronic kidney disease

In inflammatory diseases, the 5-lipoxygenase (5-LO) pathway contributes to epithelial damage and fibrosis by catalyzing the production of leukotrienes (LTs). Antagonists of the 5-LO pathway are currently approved for use in patients and are well tolerated. We found that expression of 5-LO is strongly induced in three models of chronic kidney disease: unilateral ureteral obstruction (UUO), folate nephropathy, and an orthologous mouse model of polycystic kidney disease. Immunohistochemistry showed that macrophages are the dominant source of 5-LO. Zileuton, a US Food and Drug Administration-approved antagonist of 5-LO, significantly reduced fibrosis at 7 and 14 days after UUO; these findings were confirmed using a genetically modified [5-LO-associated protein-knockout ( Alox5ap^-/-)] mouse strain. Inhibition of 5-LO did not appear to change infiltration of leukocytes after UUO as measured by flow cytometry. However, fluorescence-lifetime imaging microscopy showed that 5-LO inhibitors reversed the glycolytic switch in renal tubular epithelial cells after UUO. Two downstream enzymes of 5-LO, LTA₄ hydrolase (LTA₄H) and LTC₄ synthase (LTC₄S), are responsible for the synthesis of LTB₄ and cysteinyl LTs, respectively. Fibrosis was reduced after UUO in Ltc4s^-/-, but not Lta4h^-/-, mice. In contrast, using the folate nephropathy model, we found reduced fibrosis and improved renal function in both Ltc4s^-/- and Lta4h^-/- mice. In summary, our studies suggest that manipulation of the 5-LO pathway may represent a novel treatment approach for chronic kidney disease.

Resistance to Radiotherapy and PD-L1 Blockade Is Mediated by TIM-3 Upregulation and Regulatory T-Cell Infiltration

Purpose: Radiotherapy (RT) can transform the immune landscape and render poorly immunogenic tumors sensitive to PD-L1 inhibition. Here, we established that the response to combined RT and PD-L1 inhibition is transient and investigated mechanisms of resistance.Experimental Design: Mechanisms of resistance to RT and PD-L1 blockade were investigated in orthotopic murine head and neck squamous cell carcinoma (HNSCC) tumors using mass cytometry and whole-genome sequencing. Mice were treated with anti-PD-L1 or anti-TIM-3 alone and in combination with and without RT. Tumor growth and survival were assessed. Flow cytometry was used to assess phenotypic and functional changes in intratumoral T-cell populations. Depletion of regulatory T cells (Treg) was performed using anti-CD25 antibody.Results: We show that the immune checkpoint receptor, TIM-3, is upregulated on CD8 T cells and Tregs in tumors treated with RT and PD-L1 blockade. Treatment with anti-TIM-3 concurrently with anti-PD-L1 and RT led to significant tumor growth delay, enhanced T-cell cytotoxicity, decreased Tregs, and improved survival in orthotopic models of HNSCC. Despite this treatment combination, the response was not durable, and analysis of relapsed tumors revealed resurgence of Tregs. Targeted Treg depletion, however, restored antitumor immunity in mice treated with RT and dual immune checkpoint blockade and resulted in tumor rejection and induction of immunologic memory.Conclusions: These data reveal multiple layers of immune regulation that can promote tumorigenesis and the therapeutic potential of sequential targeting to overcome tumor resistance mechanisms. We propose that targeted Treg inhibitors may be critical for achieving durable tumor response with combined radiotherapy and immunotherapy. Clin Cancer Res; 24(21); 5368-80. ©2018 AACR.

Abstract B33: CRISPR/Cas9 generation of Ret and Ntrk1 fusion oncogenes and novel in vitro sgRNA screening method

Chromosomal rearrangements of ALK, RET, ROS1, and NTRK1 collectively represent approximately 10% of oncogenic drivers in lung adenocarcinoma. These rearrangements result in the aberrant expression and constitutive activation of a chimeric fusion kinase, which promotes growth, proliferation and survival of the cancer cell. CRISPR/Cas9 technology can now be employed to generate these chromosomal rearrangements both in vitro and in vivo. sgRNAs can be designed to target the Cas9 endonuclease to introns within the 5′ and 3′ gene partners of the rearrangement. A unique advantage of this approach is that it is compatible with immunocompetent mouse models. We have developed a novel in vitro screening strategy to identify sgRNAs that successfully generated the intended rearrangements. Ba/F3 cells are a murine B-cell cell line whose proliferation is normally dependent on the exogenous addition of the cytokine interleukin 3 (IL3), but can be rendered IL3 independent if an oncogenic alteration is introduced. We hypothesized that IL3-independence in Ba/F3 cells could be used as a method to select for cells that had successfully created chromosomal rearrangements leading to oncogenic fusions. This strategy eliminates the need for single cell cloning to confirm that successful CRISPR genome editing has occurred. We transfected Ba/F3 cells with pairs of sgRNAs within the PX330 Cas9 containing plasmid and then withdrew IL3. Cells that became IL3 independent were tested for rearrangements. Using this screening system, we successfully generated Kif5b-Ret, Trim24-Ret, and Tpm3-Ntrk1 rearrangements in Ba/F3 cells. These rearrangements were confirmed using PCR or RT-PCR and sequencing using fusion-specific primers. Additionally, the Ret rearrangements and Ntrk1 rearrangements were far more sensitive to RET and TRK inhibitors, respectively, than parental Ba/F3 cells, further confirming that the Ba/F3 cells' growth was now dependent on signaling from the fusion kinase. RET protein expression was also detected with Western blotting in the two Ret rearranged Ba/F3 cell lines. Our future plans are to introduce adenovirus containing validated sgRNAs into immune-competent mice, and confirm that they generate tumors with the intended rearrangements.

Citation Format: Laura Schubert, Anh T. Le, Stephen P. Malkoski, Raphael Nemenoff, Robert C. Doebele. CRISPR/Cas9 generation of Ret and Ntrk1 fusion oncogenes and novel in vitro sgRNA screening method [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B33.

Tumor cell-intrinsic MHC class II expression as a determinant of immunotherapy responsiveness in an orthotopic mouse model of non-small cell lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide and the second most common cancer among both men and women in the United States. Immunotherapy regimens that disrupt the inhibitory PD-1/PD-L1 axis have recently emerged as promising treatments that can unleash anti-tumor immunity against a wide range of cancers, including a subset of lung cancers. How these therapies elicit potent anti-tumor immunity remains controversial, with markers for immunotherapy-sensitivity still an active area of investigation. To study determinants of lung cancer growth in vivo we studied two orthotopic mouse models of non-small cell lung cancer (NSCLC). These Kras-mutant tumor lines dramatically differ in their response to immunotherapy: CMT167 tumor cells are exquisitely susceptible to PD-1/PD-L1 targeted immunotherapy whereas LLC tumor cells are immunotherapy-resistant. Immunotherapy-sensitive cells showed induction of the MHC class II antigen processing and presentation pathway in vitro and in vivo, and were capable of stimulating CD4 T cells directly in ex vivo co-culture. To study the impact of tumor cell-intrinsic MHC class II induction, we used RNA interference to knockdown CIITA, a transcriptional inducer of the MHC class II pathway. CIITA knockdown in immunotherapy-sensitive cells impaired the induction of tumor cell-intrinsic MHC class II in vitro and abrogated CD4 T cell stimulation in co-culture. CIITA knockdown further converted tumors from immunotherapy-sensitive to immunotherapy-resistant. These studies identify tumor cell-intrinsic expression of MHC class II as a potential direct target for CD4 T cell recognition that may promote sensitivity to PD-1/PD-L1 blockade.

IL-33 deficiency slows cancer growth but does not protect against cisplatin-induced AKI in mice with cancer

The effect of IL-33 deficiency on acute kidney injury (AKI) and cancer growth in a 4-wk model of cisplatin-induced AKI in mice with cancer was determined. Mice were injected subcutaneously with murine lung cancer cells. Ten days later, cisplatin (10 mg·kg-¹·wk-¹) was administered weekly for 4 wk. The increase in kidney IL-33 preceded the AKI and tubular injury, suggesting that IL-33 may play a causative role. However, the increase in serum creatinine, blood urea nitrogen, serum neutrophil gelatinase-associated lipoprotein, acute tubular necrosis, and apoptosis scores in the kidney in cisplatin-induced AKI was the same in wild-type and IL-33-deficient mice. There was an increase in kidney expression of pro-inflammatory cytokines CXCL1 and TNF-α, known mediators of cisplatin-induced AKI, in IL-33-deficient mice. Surprisingly, tumor weight, tumor volume, and tumor growth were significantly decreased in IL-33-deficient mice, and the effect of cisplatin on tumors was enhanced in IL-33-deficient mice. As serum IL-33 was increased in cisplatin-induced AKI in mice, it was determined whether serum IL-33 is an early biomarker of AKI in patients undergoing cardiac surgery. Immediate postoperative serum IL-33 concentrations were higher in matched AKI cases compared with non-AKI controls. In conclusion, even though the cancer grows slower in IL-33-deficient mice, the data that IL-33 deficiency does not protect against AKI in a clinically relevant model suggest that IL-33 inhibition may not be useful to attenuate AKI in patients with cancer. However, serum IL-33 may serve as a biomarker of AKI.

Ionizing radiation sensitizes tumors to PD-L1 immune checkpoint blockade in orthotopic murine head and neck squamous cell carcinoma

Immunotherapy clinical trials targeting the programmed-death ligand axis (PD-1/PD-L1) show that most head and neck squamous cell carcinoma (HNSCC) patients are resistant to PD-1/PD-L1 inhibition. We investigated whether local radiation to the tumor can transform the immune landscape and render poorly immunogenic HNSCC tumors sensitive to PD-L1 inhibition. We used the first novel orthotopic model of HNSCC with genetically distinct murine cell lines. Tumors were resistant to PD-L1 checkpoint blockade, harbored minimal PD-L1 expression and tumor infiltrating lymphocytes at baseline, and were resistant to radiotherapy. The combination of radiation and PD-L1 inhibition significantly enhanced tumor control and improved survival. This was mediated in part through upregulation of PD-L1 on tumor cells and increased T-cell infiltration after RT, resulting in a highly inflamed tumor. Depletion of both CD4 and CD8 T-cells completely abrogated the effect of anti PD-L1 with radiation on tumor growth. Our findings provide evidence that radiation to the tumor can induce sensitivity to PD-L1 checkpoint blockade in orthotopic models of HNSCC. These findings have direct relevance to high risk HNSCC patients with poorly immunogenic tumors and who may benefit from combined radiation and checkpoint blockade.

Radiotherapy to enhance T-cell infiltration and efficacy of PD-L1 blockade in murine orthotopic models of head and neck cancer

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Background: Cancers of the head and neck (HNC) represent some of the most debilitating and aggressive tumors. Radiotherapy (RT) is the primary treatment modality for locally advanced HNC, but less than 50% of patients treated with RT survive to 5 years. Clinical trials with the immune checkpoint inhibitor PD-L1 have shown considerable promise, but on its own has only yielded a 20% response rate. RT has the potential to transform the tumor microenvironment promoting infiltration of T-cells in poorly immunogenic tumors and activating T-cells in tumors with pre-existing T-cell populations. We hypothesized that the combination of PD-L1 inhibition with radiation can enhance therapeutic efficacy through re-invigoration of exhausted T-cells. Methods: Tumor cells were injected into the right buccal mucosa. Treatment was initiated when established tumors were observed. Forty mice per tumor model were randomized to IgG2b control, anti PD-L1, RT alone or RT+anti PD-L1. Anti PD-L1 was started 3 days before RT (single dose of 10Gy) and maintained for 3 weeks. For mechanistic studies, mice received the same treatment but were euthanized 72 hours after RT. Flow cytometric analysis of T-cell expression of PD-1, CTLA-4, FOXP3, CD44 and IFNG was performed on freshly harvested tumors and regional lymph nodes. Results: Tumor-bearing mice formed aggressive tumors with regional lymph node metastasis. Mice treated with RT or anti PD-L1 had slightly improved survival whereas mice treated with RT+anti-PD-L1 had significantly improved survival (p = 0.0007). Tumor control was significantly improved in the RT+anti-PD-L1 group compared to other groups. Anti PD-L1 alone did not improve tumor control. Average tumor volume on day 23 was 175±60.1 mm3 in the RT+anti-PD-L1 group compared to 623±91.0 mm3 in the PD-L1 group. Flow cytometric analysis revealed that this is mediated by enhancement in T-cell infiltration. Analysis of T-cell activation showed increased expression of CD44 and IFNG. Conclusions: Our results show a critical role for RT in mediating sensitivity to PD-L1 inhibition in HNC. In combination with anti PD-L1, RT significantly increased survival and tumor control compared to either modality alone.

Context-dependent role for chromatin remodeling component PBRM1/BAF180 in clear cell renal cell carcinoma

A subset of clear cell renal cell carcinoma (ccRCC) tumors exhibit a HIF1A gene mutation, yielding two ccRCC tumor types, H1H2 type expressing both HIF1α and HIF2α, and H2 type expressing HIF2α, but not functional HIF1α protein. However, it is unclear how the H1H2 type ccRCC tumors escape HIF1's tumor-suppressive activity. The polybromo-1 (PBRM1) gene coding for the BAF180 protein, a component of the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, is inactivated in 40% ccRCCs, the function and mechanism of BAF180 mutation is unknown. Our previous study indicates that BAF180-containing SWI/SNF chromatin remodeling complex is a co-activator for transcription factor HIF to induce HIF target genes. Thus, our questions are if BAF180 is involved in HIF-mediated hypoxia response and if PBRM1/BAF180 mutation has any association with the HIF1A retention in H1H2 type ccRCC. We report here that BAF180 is mutated in H1H2 ccRCC cell lines and tumors, and BAF180 re-expression in H1H2 ccRCC cell lines reduced cell proliferation/survival, indicating that BAF180 has tumor-suppressive role in these cells. However, BAF180 is expressed in HIF1-deficient H2 ccRCC cell lines and tumors, and BAF180 knockdown in H2 type ccRCC cell lines reduced cell proliferation/survival, indicating that BAF180 has tumor-promoting activity in these cells. In addition, our data show that BAF180 functions as co-activator for HIF1- and HIF2-mediated transcriptional response, and BAF180's tumor-suppressive and -promoting activity in ccRCC cell lines depends on co-expression of HIF1 and HIF2, respectively. Thus, our studies reveal that BAF180 function in ccRCC is context dependent, and that mutation of PBRM1/BAF180 serves as an alternative strategy for ccRCC tumors to reduce HIF1 tumor-suppressive activity in H1H2 ccRCC tumors. Our studies define distinct functional subgroups of ccRCCs based on expression of BAF180, and suggest that BAF180 inhibition may be a novel therapeutic target for patients with H2, but not H1H2, ccRCC tumors.

Label-free fluorescence lifetime and second harmonic generation imaging microscopy improves quantification of experimental renal fibrosis

All forms of progressive renal diseases develop a final pathway of tubulointerstitial fibrosis and glomerulosclerosis. Renal fibrosis is usually quantified using histological staining, a process that is time-consuming and pathologist dependent. Here we develop a fast and operator-independent method to measure fibrosis utilizing the murine unilateral ureteral obstruction model which manifests a time-dependent fibrotic increase in obstructed kidneys while the contralateral kidneys are used as controls. After ureteral obstruction, kidneys were analyzed at 7, 14, and 21 days. Fibrosis was quantified using fluorescence lifetime imaging (FLIM) and second harmonic generation (SHG) in a Deep Imaging via Enhanced photon Recovery deep tissue imaging microscope. This microscope was developed for deep tissue along with second and third harmonic generation imaging and has extraordinary sensitivity toward harmonic generation. SHG data suggest the presence of more fibrillar collagen in the obstructed kidneys. The combination of short-wavelength FLIM and SHG analysis results in a robust assessment procedure independent of observer interpretation and let us create criteria to quantify the extent of fibrosis directly from the image. Thus, the FLIM-SHG technique shows remarkable improvement in quantification of renal fibrosis compared to standard histological techniques.

Abstract A122: Non-small cell lung cancer cells induce PD-L1 expression in the tumor microenvironment in an orthotopic mouse model of lung cancer

Background: In many cancers, tumor cells induce local and systemic immunosuppression, inhibiting T-cell-mediated cytotoxic responses to tumor growth. Activation of the programmed cell death 1 (PD-1) pathway has been shown to contribute to immune escape in the setting of lung cancer. Antibody-mediated blockade of PD-1 and programmed death-ligand 1 (PD-L1) induces durable tumor regression and prolongs stabilization of disease in patients with non-small cell lung cancer (NSCLC), which has lead to FDA approval of an anti-PD-1 agent for the treatment of patients with advanced squamous NSCLC. However, patient selection criteria for immunotherapy targeting the PD-1 axis have not been established. Although recent studies have focused on the regulation of PD-L1 expression on lung cancer cells, the role of PD-L1 expression in the lung tumor microenvironment (TME) in mediating responses to anti-PD-1 or anti-PD-L1 therapy has not been defined. The purpose of this study was to determine the relative contributions of PD-L1 expression on cancer cells versus cells in the TME on lung cancer progression.

Methods: Two murine lung cancer cell lines derived from C57BL/6 mice were used in an orthotopic model of tumor progression: Lewis Lung Carcinoma (LLC) cells, which are a de-differentiated cell line in which driver mutations have not been identified; and CMT167 cells, which are an epithelial lung cancer cell line that express oncogenic K-Ras. Tumor cells were implanted in the left lungs of wild-type C57BL/6 mice. One week after tumor implantation, mice were treated with anti-PD-1 neutralizing antibody, anti-PD-L1 neutralizing antibody, or isotype control antibodies. The effect of pharmacologic blockade of PD-1 or PD-L1 on tumor progression was determined. In separate experiments, tumor cells were implanted into green fluorescent protein (GFP)-expressing mice, and lungs from tumor-bearing mice were analyzed by flow cytometry to evaluate the expression of PD-L1 on lung cancer cells (GFP-negative cells) and in the TME (GFP-positive cells).

Results: Antibody-mediated pharmacologic blockade of PD-1 or PD-L1 suppressed primary tumor growth and liver metastasis of both LLC and CMT167 tumors in our orthotopic model. Whereas there was a modest effect only on LLC tumors, PD-1/PD-L1 antibody blockade had a dramatic effect on CMT167 primary tumor size, with 40% of mice injected with CMT167 cells and treated with anti-PD-L1 antibody having no detectable lung tumors at the time of sacrifice. In contrast to previously published work that has shown epithelial-to-mesenchymal transition can upregulate PD-L1 expression on lung cancer cells, leading to CD8-positive T-cell immunosuppression (Chen et al, Nat Commun 2014), the well-differentiated CMT167 cells were more responsive than LLC cells to PD-L1 inhibition. Moreover, sensitivity to PD-1/PD-L1 antibody blockade did not correlate with expression of PD-L1 on tumor cells. Analysis of lungs from tumor-bearing mice revealed that both LLC cells and CMT167 cells induce PD-L1 expression in the TME (most likely tumor-associated macrophages), and that expression of PD-L1 is higher in the TME than on cancer cells in vivo. Interestingly, CMT167 tumors are associated with higher numbers of both PD-L1-positive cells and PD-1-positive cells in the TME than LLC tumors.

Conclusions: In an orthotopic mouse model, lung cancer cells upregulated PD-L1 expression in the TME, which may be an important mechanism whereby tumor cells induce T-cell immunosuppression. The ability to upregulate PD-L1 in the TME may also represent an important factor that predicts sensitivity to PD-1/PD-L1 antibody blockade.

Citation Format: Howard Li, Maria McSharry, Eric Clambey, Teresa Nguyen, Eoin McNamee, Mary Weiser-Evans, Raphael Nemenoff. Non-small cell lung cancer cells induce PD-L1 expression in the tumor microenvironment in an orthotopic mouse model of lung cancer. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A122.

Pioglitazone restores phagocyte mitochondrial oxidants and bactericidal capacity in chronic granulomatous disease

BACKGROUND

Deficient production of reactive oxygen species (ROS) by the phagocyte nicotinamide adenine dinucleotide (NADPH) oxidase in patients with chronic granulomatous disease (CGD) results in susceptibility to certain pathogens secondary to impaired oxidative killing and mobilization of other phagocyte defenses. Peroxisome proliferator-activated receptor (PPAR) γ agonists, including pioglitazone, approved for type 2 diabetes therapy alter cellular metabolism and can heighten ROS production. It was hypothesized that pioglitazone treatment of gp91(phox-/-) mice, a murine model of human CGD, would enhance phagocyte oxidant production and killing of Staphylococcus aureus, a significant pathogen in patients with this disorder.

OBJECTIVES

We sought to determine whether pioglitazone treatment of gp91(phox-/-) mice enhanced phagocyte oxidant production and host defense.

METHODS

Wild-type and gp91(phox-/-) mice were treated with the PPARγ agonist pioglitazone, and phagocyte ROS and killing of S aureus were investigated.

RESULTS

As demonstrated by 3 different ROS-sensing probes, short-term treatment of gp91(phox-/-) mice with pioglitazone enhanced stimulated ROS production in neutrophils and monocytes from blood and neutrophils and inflammatory macrophages recruited to tissues. Mitochondria were identified as the source of ROS. Findings were replicated in human monocytes from patients with CGD after ex vivo pioglitazone treatment. Importantly, although mitochondrial (mt)ROS were deficient in gp91(phox-/-) phagocytes, their restoration with treatment significantly enabled killing of S aureus both ex vivo and in vivo.

CONCLUSIONS

Together, the data support the hypothesis that signaling from the NADPH oxidase under normal circumstances governs phagocyte mtROS production and that such signaling is lacking in the absence of a functioning phagocyte oxidase. PPARγ agonism appears to bypass the need for the NADPH oxidase for enhanced mtROS production and partially restores host defense in CGD.

Homeoprotein Six2 promotes breast cancer metastasis via transcriptional and epigenetic control of E-cadherin expression

Misexpression of developmental transcription factors occurs often in human cancers, where embryonic programs may be reinstated in a context that promotes or sustains malignant development. In this study, we report the involvement of the kidney development transcription factor Six2 in the metastatic progression of human breast cancer. We found that Six2 promoted breast cancer metastasis by a novel mechanism involving both transcriptional and epigenetic regulation of E-cadherin. Downregulation of E-cadherin by Six2 was necessary for its ability to increase soft agar growth and in vivo metastasis in an immunocompetent mouse model of breast cancer. Mechanistic investigations showed that Six2 represses E-cadherin expression by upregulating Zeb2, in part, through a microRNA-mediated mechanism and by stimulating promoter methylation of the E-cadherin gene (Cdh1). Clinically, SIX2 expression correlated inversely with CDH1 expression in human breast cancer specimens, corroborating the disease relevance of their interaction. Our findings establish Six2 as a regulator of metastasis in human breast cancers and demonstrate an epigenetic function for SIX family transcription factors in metastatic progression through the regulation of E-cadherin.

Abstract 1675: Variations in the composition of inflammatory infiltrates are associated with persistence or regression of bronchial dysplasia

INTRODUCTION: The clinical course of dysplastic bronchial lesions is variable. While some regress, others progress to invasive carcinoma. We sought to identify how variations in inflammatory infiltrates might influence the clinical outcome of dysplastic bronchial lesions.

METHODS AND RESULTS: Gene expression microarray analyses identified 318 genes that distinguish persistent from regressive bronchial dysplastic lesions. Pathway analysis utilizing this genelist was performed using Ingenuity© software. Gene expression data showed several inflammation related pathways with statistically different levels of activity in persistent versus regressive lesions. Expression of genes associated with CD4 positive T-cells and HLA-DRA positive macrophages were both increased in regressive lesions. To further investigate these findings, a similar set of progressive and regressive lesions were selected for immunohistochemical (IHC) analysis. For each biopsy, IHC for T-cell markers CD3, CD4 and CD8 and macrophage marker CD68 was performed. Immunohistochemically positive inflammatory cell subsets were counted in a single high power field corresponding to the focus of maximum inflammation. For each marker, separate counts for epithelium and stroma-associated inflammation were performed. Preliminary IHC data (n=6) shows a strong trend towards increased numbers of macrophages in the dysplastic epithelium of regressive lesions (4.6 fold increase, p=0.082).

CONCLUSION: Our findings suggest that differences in inflammatory cell subsets may distinguish persistent and regressive bronchial dysplasia. Preliminary data points to CD4 positive T-cells and intraepithelial macrophages as differentiating factors that correlate with regression.

Citation Format: Mary C. O'Keefe, Lori Dwyer-Nield, Michael Edwards, Robert L. Keith, Wilbur A. Franklin, Michio Sugita, York E. Miller, Micah Friedman, Meredith Tennis, Kevin S. Choo, Gregory Hickey, Jeannine Porter, Storey Wilson, Andrea Osypuk, Mary Weiser, Adrie van Bokhoven, Mark Geraci, Raphael Nemenoff, Daniel T. Merrick. Variations in the composition of inflammatory infiltrates are associated with persistence or regression of bronchial dysplasia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1675. doi:10.1158/1538-7445.AM2014-1675

Abstract 231: Gene expression analysis of persistent and regressive bronchial dysplasia identifies polo-like kinase 1 (PLK1) and epoxide hydrolase 3 (EPHX3) as potential mediators of malignant progression

Introduction: Gene expression microarray analysis was employed to identify alterations that distinguish persistent from regressive bronchial dysplasia (BD). BD is a precursor of squamous cell carcinoma (SCC), and persistent BDs represent a high risk subset of these lesions. A potential role for promotion of genomic instability in persistence of BD is suggested by the overexpression of polo-like kinase 1 (PLK1), which abrogates G2-M checkpoint DNA damage repair, and epoxide hydrolase 3 (EPHX3), which converts tobacco smoke derived pro-carcinogens to mutagens.

Methods and Results: Sixty-three frozen baseline biopsies were classified, based on the presence or absence of BD in follow-up biopsies, into persistent BD, regressive BD, progressive non-dysplasia and stable non-dysplasia groups. ANOVA statistical analysis with a false discovery rate of 10% revealed 318 differentially expressed genes between persistent and regressive BD, whereas all other intergroup comparisons except persistent BD versus stable non-dysplasia revealed no or very few (<15) differentially expressed genes. This confirmed the unique biological nature of persistent BD. A pathway analysis using this genelist and employing Ingenuity© software revealed “mitotic roles of PLKs” as having the most significant association with persistence. Based on their potential complimentary contribution to genomic instability, PLK1 and EPHX3 were further studied. Gene expression levels from all specimens with BD at baseline were used to classify biopsies as PLK1 and/or EPHX3 overexpressers based on expression levels greater than the mean expression for the gene. Using a histology score (1-8 for normal-SCC), a significant increase in outcome histology was noted in progressing from groups composed of cases without overexpression either gene, overexpression of one gene or overexpression of both genes (2.58 vs. 3.60 vs. 5.06 respectively). Validational analyses employing quantitative RT-PCR using cultures of 8 persistent BD and 6 regressive BD confirmed increased expression in persistent BD of PLK1 (2.77X, p=0.002) and EPHX3 (2.36X, p=0.081). Treatment of a persistent BD cell line with Volasertib, a specific inhibitor of PLK1, at 100nM showed potent inhibition of cell viability (live cell protease activity, 0.61 fold change vs untreated, p<0.05) and a strong trend toward increased apoptotic activity (caspase 3/7 activity, 1.71 fold change vs. untreated, p=0.076). Volasertib had no effect on these activities in cultured normal bronchial epithelial cells.

Conclusion: Gene expression analysis demonstrates the biologically distinct, high risk nature of persistent BD and suggests a potential role for overexpression of PLK1 and EPHX3 in the development of invasive SCC of the lung.

Citation Format: Daniel T. Merrick, Michael G. Edwards, Wilbur A. Franklin, Michio Sugita, Micah Friedman, York E. Miller, Lori Dwyer-Nield, Meredith Tennis, Kevin Choo, Greg Hickey, van Bokhoven Adriaan, Lynn Heasley, Paul A. Bunn, Mark Geraci, Robert L. Keith, Raphael Nemenoff. Gene expression analysis of persistent and regressive bronchial dysplasia identifies polo-like kinase 1 (PLK1) and epoxide hydrolase 3 (EPHX3) as potential mediators of malignant progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 231. doi:10.1158/1538-7445.AM2014-231

Transmigrating neutrophils shape the mucosal microenvironment through localized oxygen depletion to influence resolution of inflammation

Acute intestinal inflammation involves early accumulation of neutrophils (PMNs) followed by either resolution or progression to chronic inflammation. Based on recent evidence that mucosal metabolism influences disease outcomes, we hypothesized that transmigrating PMNs influence the transcriptional profile of the surrounding mucosa. Microarray studies revealed a cohort of hypoxia-responsive genes regulated by PMN-epithelial crosstalk. Transmigrating PMNs rapidly depleted microenvironmental O2 sufficiently to stabilize intestinal epithelial cell hypoxia-inducible factor (HIF). By utilizing HIF reporter mice in an acute colitis model, we investigated the relative contribution of PMNs and the respiratory burst to "inflammatory hypoxia" in vivo. CGD mice, lacking a respiratory burst, developed accentuated colitis compared to control, with exaggerated PMN infiltration and diminished inflammatory hypoxia. Finally, pharmacological HIF stabilization within the mucosa protected CGD mice from severe colitis. In conclusion, transcriptional imprinting by infiltrating neutrophils modulates the host response to inflammation, via localized O2 depletion, resulting in microenvironmental hypoxia and effective inflammatory resolution.

Abstract 2356: Biomarkers of progressive squamous lung dyplasia

Lung cancer is the leading cause of cancer death in the United States. Squamous cell lung cancers (SCC) comprise approximately 30% of lung cancer cases, and 48,000 people are projected to die this year in the U.S. from SCC. Bronchial dysplasia (BD) is a precursor of SCC, however not all BDs progress to carcinoma. Persistent or progressive BD is associated with a higher risk for the development of invasive lung cancer. We hypothesize that characterization of the difference between persistent and regressive BD will identify high risk patients and suggest novel therapeutic targets for prevention of progression to lung SCC. Gene expression analysis was used to identify differences between persistent and regressive BD. Subjects recruited to Colorado SPORE in Lung Cancer screening studies that met sputum atypia criteria and underwent multiple bronchoscopies were evaluated. Sixty-three frozen baseline biopsies showing BD by histology were classified as persistent/progressive (group 1) or regressive (group 2) according the presence or absence of BD on follow-up biopsies at the same sites. H&E staining was performed on frozen sections to confirm histology, and RNA was harvested and used to create gene expression arrays. PLK1 was selected as a gene of interest based on significantly increased levels of expression and pathway analyses implicating increased activity of cellular pathways associated with PLK-1 expression. Additionally, bronchial epithelial cells were cultured from fresh biopsies taken immediately adjacent to persistent or regressive bronchial sites, and RNA, DNA, and protein were harvested. qRT-PCR was performed on RNA extracted from these persistent and regressive biopsy epithelial cultures. PLK1 expression in epithelial cultures was shown to be increased in persistent as compared to regressive cell lines suggesting that this cell cycle control enzyme may represent a possible chemoprevention target in persistent/progressive dysplasias. RNA was also extracted from a variety of immortalized cancer cell lines of both squamous and adenocarcinoma subtypes, and qRT-PCR was used to establish baseline expression of these genes in cancer cells. Eleven of 20 lung cancer cell lines showed at least 20 fold higher PKL-1 expression compared to non-tumorigenic cell lines while 4 out of 4 lines of SCC origin showed 75 fold or higher expression further supporting a role for this enzyme in SCC progression.

Citation Format: Micah Friedman, Meredith Tennis, Lori Dwyer-Nield, Robert Keith, Raphael Nemenoff, Wilbur Franklin, Mark Geraci, Michael Edwards, Sugita Michio, Dan Merrick. Biomarkers of progressive squamous lung dyplasia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2356. doi:10.1158/1538-7445.AM2013-2356

Adipose lineage specification of bone marrow-derived myeloid cells

We have reported the production of white adipocytes in adipose tissue from hematopoietic progenitors arising from bone marrow. However, technical challenges have hindered detection of this adipocyte population by certain other laboratories. These disparate results highlight the need for sensitive and definitive techniques to identify bone marrow progenitor (BMP)-derived adipocytes. In these studies we exploited new models and methods to enhance detection of this adipocyte population. Here we showed that confocal microscopy with spectrum acquisition could effectively identify green fluorescent protein (GFP) positive BMP-derived adipocytes by matching their fluorescence spectrum to that of native GFP. Likewise, imaging flow cytometry made it possible to visualize intact unilocular and multilocular GFP-positive BMP-derived adipocytes and distinguished them from non-fluorescent adipocytes and cell debris in the cytometer flow stream. We also devised a strategy to detect marker genes in flow-enriched adipocytes from which stromal cells were excluded. This technique also proved to be an efficient means for detecting genetically labeled adipocytes and should be applicable to models in which marker gene expression is low or absent. Finally, in vivo imaging of mice transplanted with BM from adipocyte-targeted luciferase donors showed a time-dependent increase in luciferase activity, with the bulk of luciferase activity confined to adipocytes rather than stromal cells. These results confirmed and extended our previous reports and provided proof-of-principle for sensitive techniques and models for detection and study of these unique cells.

Splenectomy exacerbates lung injury after ischemic acute kidney injury in mice

Patients with acute kidney injury (AKI) have increased serum proinflammatory cytokines and an increased occurrence of respiratory complications. The aim of the present study was to examine the effect of renal and extrarenal cytokine production on AKI-mediated lung injury in mice. C57Bl/6 mice underwent sham surgery, splenectomy, ischemic AKI, or ischemic AKI with splenectomy and kidney, spleen, and liver cytokine mRNA, serum cytokines, and lung injury were examined. The proinflammatory cytokines IL-6, CXCL1, IL-1β, and TNF-α were increased in the kidney, spleen, and liver within 6 h of ischemic AKI. Since splenic proinflammatory cytokines were increased, we hypothesized that splenectomy would protect against AKI-mediated lung injury. On the contrary, splenectomy with AKI resulted in increased serum IL-6 and worse lung injury as judged by increased lung capillary leak, higher lung myeloperoxidase activity, and higher lung CXCL1 vs. AKI alone. Splenectomy itself was not associated with increased serum IL-6 or lung injury vs. sham. To investigate the mechanism of the increased proinflammatory response, splenic production of the anti-inflammatory cytokine IL-10 was determined and was markedly upregulated. To confirm that splenic IL-10 downregulates the proinflammatory response of AKI, IL-10 was administered to splenectomized mice with AKI, which reduced serum IL-6 and improved lung injury. Our data demonstrate that AKI in the absence of a counter anti-inflammatory response by splenic IL-10 production results in an exuberant proinflammatory response and lung injury.

Prostacyclin prevents murine lung cancer independent of the membrane receptor by activation of peroxisomal proliferator--activated receptor gamma

Overexpression of prostacyclin synthase (PGIS) decreases lung tumor multiplicity in chemical- and cigarette-smoke-induced murine lung cancer models. Prostacyclin signals through a single G-protein-coupled receptor (IP), which signals through cyclic AMP. To determine the role of this receptor in lung cancer chemoprevention by prostacyclin, PGIS-overexpressing mice were crossed to mice that lack the IP receptor [IP(-/-)]. Carcinogen-induced lung tumor incidence was similar in IP(+/+), IP(+/-), and IP(-/-) mice, and overexpression of PGIS gave equal protection in all three groups, indicating that the protective effects of prostacyclin are not mediated through activation of IP. Because prostacyclin can activate members of the peroxisomal proliferator-activated receptor (PPAR) family of nuclear receptors, we examined the role of PPARgamma in the protection of prostacyclin against lung tumorigenesis. Iloprost, a stable prostacyclin analogue, activated PPARgamma in nontransformed bronchial epithelial cells and in a subset of human non-small-cell lung cancer cell lines. Iloprost-impregnated chow fed to wild-type mice resulted in elevated lung macrophages and decreased lung tumor formation. Transgenic animals with lung-specific PPARgamma overexpression also developed fewer lung tumors. This reduction was not enhanced by administration of supplemental iloprost. These studies indicate that PPARgamma is a critical target for prostacyclin-mediated lung cancer chemoprevention and may also have therapeutic activity.

Paired-related homeobox gene Prx1 is required for pulmonary vascular development

Herein, we show that the paired-related homeobox gene, Prx1, is required for lung vascularization. Initial studies revealed that Prx1 localizes to differentiating endothelial cells (ECs) within the fetal lung mesenchyme, and later within ECs forming vascular networks. To begin to determine whether Prx1 promotes EC differentiation, fetal lung mesodermal cells were transfected with full-length Prx1 cDNA, resulting in their morphological transformation to an endothelial-like phenotype. In addition, Prx1-transformed cells acquired the ability to form vascular networks on Matrigel. Thus, Prx1 might function by promoting pulmonary EC differentiation within the fetal lung mesoderm, as well as their subsequent incorporation into vascular networks. To understand how Prx1 participates in network formation, we focused on tenascin-C (TN-C), an extracellular matrix (ECM) protein induced by Prx1. Immunocytochemistry/histochemistry showed that a TN-C-rich ECM surrounds Prx1-positive pulmonary vascular networks both in vivo and in tissue culture. Furthermore, antibody-blocking studies showed that TN-C is required for Prx1-dependent vascular network formation on Matrigel. Finally, to determine whether these results were relevant in vivo, we examined newborn Prx1-wild-type (+/+) and Prx1-null (-/-) mice and showed that Prx1 is critical for expression of TN-C and lung vascularization. These studies provide a framework to understand how Prx1 controls EC differentiation and their subsequent incorporation into functional pulmonary vascular networks.

Increased epoxyeicosatrienoic acid formation in the rat kidney during liver cirrhosis

Vascular complications during liver cirrhosis are often severe, particularly in the kidney. These complications are the result of complex and poorly understood interactions between the injured liver and other organs such as the lungs, heart, and kidney. The purpose of this study was to investigate the alterations to renal hemodynamics during cirrhosis, focusing on the actions of epoxyeicosatrienoic acids (EET), known to be potent regulators of renal hemodynamics. Cirrhosis was induced in rats by common bile duct ligation (CBDL), and they were compared with sham rats. Experiments were conducted 4 wk after either the sham or CBDL surgery. Vasoreactivity was assessed in isolated perfused kidneys. cPLA(2) expression and cytochrome P450 (CYP450) expression were measured using Western blot. cPLA(2) enzymatic activity was measured by radioenzymatic assay. EET production was measured using rpHPLC analysis. The major findings were that kidneys from CBDL rats had significantly greater acetylcholine-induced vasodilation that was partially blocked by nitric oxide (NO) and prostaglandin inhibition and fully blocked by the combined inhibition of NO, prostaglandins, and CYP450 metabolites. Expression and activity of cPLA(2) in CBDL kidneys was increased, providing arachidonic acid substrate to the CYP450 enzymes. Finally, expression and activity of CYP450 enzymes was elevated in CBDL kidneys, resulting in significantly greater production of the vasodilating 11,12-EET and 14,15-EET. While it is well documented that renal vasoconstriction leading to impaired renal function occurs during cirrhosis, our data clearly demonstrate that endogenous production of EET is increased in cirrhotic kidneys. This may be a homeostatic response to preserve renal perfusion.

FAK induces expression of Prx1 to promote tenascin-C-dependent fibroblast migration

Fibroblast migration depends, in part, on activation of FAK and cellular interactions with tenascin-C (TN-C). Consistent with the idea that FAK regulates TN-C, migration-defective FAK-null cells expressed reduced levels of TN-C. Furthermore, expression of FAK in FAK-null fibroblasts induced TN-C, whereas inhibition of FAK activity in FAK-wild-type cells had the opposite effect. Paired-related homeobox 1 (Prx1) encodes a homeobox transcription factor that induces TN-C by interacting with a binding site within the TN-C promoter, and it also promotes fibroblast migration. Therefore, we hypothesized that FAK regulates TN-C by controlling the DNA-binding activity of Prx1 and/or by inducing Prx1 expression. Prx1-homeodomain binding site complex formation observed with FAK-wild-type fibroblasts failed to occur in FAK-null fibroblasts, yet expression of Prx1 in these cells induced TN-C promoter activity. Thus, FAK is not essential for Prx1 DNA-binding activity. However, activated FAK was essential for Prx1 expression. Functionally, Prx1 expression in FAK-null fibroblasts restored their ability to migrate toward fibronectin, in a manner that depends on TN-C. These results appear to be relevant in vivo because Prx1 and TN-C expression levels were reduced in FAK-null embryos. This paper suggests a model whereby FAK induces Prx1, and subsequently the formation of a TN-C-enriched ECM that contributes to fibroblast migration.

Hypoxia-induced pulmonary vascular remodeling: contribution of the adventitial fibroblasts

Vascular repair in response to injury or stress (often referred to as remodeling) is a common complication of many cardiovascular abnormalities including pulmonary hypertension, systemic hypertension, atherosclerosis, vein graft remodeling and restenosis following balloon dilatation of the coronary artery. It is not surprising that repair and remodeling occurs frequently in the vasculature in that exposure of blood, vessels to either excessive hemodynamic stress (e.g. hypertension), noxious blood borne agents (e.g. atherogenic lipids), locally released cytokines, or unusual environmental conditions (e.g. hypoxia), requires readily available mechanisms to counteract these adverse stimuli and to preserve structure and function of the vessel wall. The responses, which were presumably evolutionarily developed to repair an injured tissue, often escape self-limiting control and can result, in the case of blood vessels, in lumen narrowing and obstruction to blood flow. Each cell type (i. e. endothelial cells, smooth muscle cells, and fibroblasts) in the vascular wall plays a specific role in the response to injury. However, while the roles of the endothelial cells and smooth muscle cells (SMC) in vascular remodeling have been extensively studied, relatively little attention has been given to the adventitial fibroblasts. Perhaps this is because the fibroblast is a relatively ill-defined cell which, at least compared to the SMC, exhibits few specific cellular markers. Importantly though, it has been well demonstrated that fibroblasts possess the capacity to express several functions such as migration, rapid proliferation, synthesis of connective tissue components, contraction and cytokine production in response to activation or stimulation. The myriad of responses exhibited by the fibroblasts, especially in response to stimulation, suggest that these cells could play a pivotal role in the repair of injury. This fact has been well documented in the setting of wound healing where a hypoxic environment has been demonstrated to be critical in the cellular responses. As such it is not surprising that fibroblasts may play an important role in the vascular response to hypoxia and/or injury. This paper is intended to provide a brief review of the changes that occur in the adventitial fibroblasts in response to vascular stress (especially hypoxia) and the role the activated fibroblasts might play in hypoxia-mediated pulmonary vascular disease.

Hypoxia induces cell-specific changes in gene expression in vascular wall cells: implications for pulmonary hypertension

Mammals respond to reduced oxygen concentrations (hypoxia) in many different ways at the systemic, local, cellular and molecular levels. Within the pulmonary circulation, exposure to chronic hypoxia has been demonstrated to illicit increases in pulmonary artery pressure as well as dramatic structural changes in both large and small vessels. It has become increasingly clear that the response to hypoxia in vivo is differentially regulated at the level of specific cell types within the vessel wall. For instance, in large pulmonary blood vessels there is now convincing evidence to suggest that the medial layer is made up of many different subpopulations of smooth muscle cells. In response to hypoxia there are remarkable differences in the proliferative and matrix producing responses of these cells to the hypoxic environment. Some cell populations proliferate and increase matrix protein synthesis, while in other cell populations no apparent change in the proliferative or differentiation state of the cell takes place. In more peripheral vessels, the predominant proliferative changes in response to hypoxia in the pulmonary circulation occur in the adventitial layer rather than in the medial layer. Here again, specific increases in proliferation and matrix protein synthesis take place. Accumulating evidence suggests that the unique responses exhibited by specific cell types of hypoxia in vivo can be modeled in vitro. We have isolated, in culture, specific medial cell populations which demonstrate significant increases in proliferation in response to hypoxia, and others which exhibit no change or, in fact, a decrease in proliferation under hypoxic conditions. We have also isolated and cloned several unique populations of adventitial fibroblasts. There is good evidence that only certain fibroblast populations are capable of responding to hypoxia with an increase in proliferation. We have begun to elucidate the signaling pathways which are activated in those cell populations that exhibit proliferative responses to hypoxia. We show that hypoxia, in the absence of serum or mitogens, specifically activates select members of the protein kinase C isozyme family, as well as members of the mitogen-activated protein kinase (MAPK) family of proteins. This selective activation appears to take place in response to hypoxia only in those cells exhibiting a proliferative response, and antagonists of this pathway inhibit the response. Thus, there appear to be cells within each organ that demonstrate unique responses to hypoxia. A better understanding of why these cells exist and how they specifically transduce hypoxia-mediated signals will lead to a better understanding of how the changes in the pulmonary circulation take place under conditions of chronic hypoxia.

Effect of hypoxia on proximal tubules isolated from nitric oxide synthase knockout mice

Nitric oxide (NO) has been shown to be a mediator of hypoxic injury in rat renal proximal tubules (PT). However, the role of NO in hypoxic injury to mouse. PT has not been examined. The aim of the present study was to determine the effect of knockout of nitric oxide synthase (NOS) isoforms on hypoxic injury in mouse PT. Mouse PTs were isolated by collagenase digestion and Percoll centrifugation. The nonselective NOS inhibitor, N-nitro-L-arginine methyl ester (L-NAME, 10 mM), but not its inactive stereoisomer D-NAME, protected against hypoxic injury as assessed by LDH release. Carboxy-imidazolineoxyl N-oxide (carboxy-PTIO, 100 microM), a stable NO scavenger, also afforded cytoprotection against hypoxic injury. To determine the role of the different NOS isoforms in the hypoxic injury, we examined the effect of hypoxia on PT isolated from knockout mice in which either the inducible NOS (iNOS) endothelial NOS (eNOS) or neuronal NOS (nNOS) gene was lacking. PT isolated from iNOS knockout mice were resistant to hypoxic injury compared to wild-type controls. In contrast, PT isolated from both nNOS and eNOS knockout mice were not protected against hypoxic injury. In conclusion, the present study demonstrates that NO is a mediator of hypoxic PT injury in the mouse and that knockout of the iNOS gene is cytoprotective against this hypoxic PT injury.