The role of APOBEC3B in lung tumor evolution and targeted cancer therapy resistance

In this study, the impact of the apolipoprotein B mRNA-editing catalytic subunit-like (APOBEC) enzyme APOBEC3B (A3B) on epidermal growth factor receptor (EGFR)-driven lung cancer was assessed. A3B expression in EGFR mutant (EGFRmut) non-small-cell lung cancer (NSCLC) mouse models constrained tumorigenesis, while A3B expression in tumors treated with EGFR-targeted cancer therapy was associated with treatment resistance. Analyses of human NSCLC models treated with EGFR-targeted therapy showed upregulation of A3B and revealed therapy-induced activation of nuclear factor kappa B (NF-κB) as an inducer of A3B expression. Significantly reduced viability was observed with A3B deficiency, and A3B was required for the enrichment of APOBEC mutation signatures, in targeted therapy-treated human NSCLC preclinical models. Upregulation of A3B was confirmed in patients with NSCLC treated with EGFR-targeted therapy. This study uncovers the multifaceted roles of A3B in NSCLC and identifies A3B as a potential target for more durable responses to targeted cancer therapy.

3-Phosphoinositide-dependent kinase 1 drives acquired resistance to osimertinib

Osimertinib sensitive and resistant NSCLC NCI-H1975 clones are used to model osimertinib acquired resistance in humanized and non-humanized mice and delineate potential resistance mechanisms. No new EGFR mutations or loss of the EGFR T790M mutation are found in resistant clones. Resistant tumors grown under continuous osimertinib pressure both in humanized and non-humanized mice show aggressive tumor regrowth which is significantly less sensitive to osimertinib as compared with parental tumors. 3-phosphoinositide-dependent kinase 1 (PDK1) is identified as a potential driver of osimertinib acquired resistance, and its selective inhibition by BX795 and CRISPR gene knock out, sensitizes resistant clones. In-vivo inhibition of PDK1 enhances the osimertinib sensitivity against osimertinib resistant xenograft and a patient derived xenograft (PDX) tumors. PDK1 knock-out dysregulates PI3K/Akt/mTOR signaling, promotes cell cycle arrest at the G1 phase. Yes-associated protein (YAP) and active-YAP are upregulated in resistant tumors, and PDK1 knock-out inhibits nuclear translocation of YAP. Higher expression of PDK1 and an association between PDK1 and YAP are found in patients with progressive disease following osimertinib treatment. PDK1 is a central upstream regulator of two critical drug resistance pathways: PI3K/AKT/mTOR and YAP.

Abstract 2197: Targeted cancer therapy induces APOBEC fueling the evolution of drug resistance

Introduction: Increasing our understanding of drivers of mutagenesis in lung cancer is critical in our efforts to prevent tumor reoccurrence and resistance.

Results: Using the multi-region TRACERx lung cancer study, we uncovered that APOBEC3B is significantly upregulated when compared with other APOBEC family members in EGFR driven lung cancer and identified subclonal enrichment of APOBEC mutational signatures. To model APOBEC mutagenesis in lung cancer, several novel EGFR mutant mouse models containing a human APOBEC3B transgene were generated. Using these models, it was uncovered that APOBEC3B expression is detrimental at tumor initiation when expressed continuously in a p53 wildtype background. This detrimental effect is likely due to elevated chromosomal instability, which was observed to increase significantly with APOBEC3B expression in an EGFR mutant TP53 deficient mouse model. Induction of subclonal expression of APOBEC3B in an EGFR mutant mouse model with tyrosine kinase inhibitor (TKI) therapy resulted in a significant increase in resistant tumor development. Significant downregulation of the base excision repair gene uracil-DNA glycosylase (UNG) was also observed in APOBEC3B expressing mice, which paralleled findings in patient tumors and cell lines treated with TKI therapy. Finally, a mouse mutational signature was identified in APOBEC3B expressing cell lines, reinforcing the idea that APOBEC driven mutagenesis contributes to TKI resistance.

Conclusion: This study demonstrates a unique principle by which targeted therapy induces changes within tumors ideal for APOBEC driven tumor evolution, fueling therapy resistance.

Citation Format: Manasi Mayekar, Deborah Caswell, Natalie Vokes, Emily K. Law, Wei Wu, William Hill, Eva Gronroos, Andrew Rowan, Maise Al Bakir, Clare Weeden, Caroline E. McCoach, Collin M. Blakely, Nuri Alpay Temiz, Ai Nagano, Daniel L. Kerr, Julia K. Rotow, Oriol Pich, Franziska Haderk, Michelle Dietzen, Carlos Martinez Ruiz, Bruna Almeida, Lauren Cech, Beatrice Gini, Joanna Przewrocka, Chris Moore, Miguel Murillo, Bjorn Bakker, Brandon Rule, Cameron Durfee, Shigeki Nanj, Lisa Tan, Lindsay K. Larson, Prokopios P. Argyris, William L. Brown, Johnny Yu, Carlos Gomez, Philippe Gui, Rachel I. Vogel, Elizabeth A. Yu, Nicholas J. Thomas, Subramanian Venkatesan, Sebastijan Hobor, Su Kit Chew, Nicholas McGranahan, Nnennaya Kanu, Eliezer M. Van Allen, Julian Downward, Reuben S. Harris, Trever Bivona, Charles Swanton. Targeted cancer therapy induces APOBEC fueling the evolution of drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2197.

Abstract 3808: Spatially resolved transcriptomics of cellular architecture in EGFR-mutated lung cancer

Introduction: Single-cell RNA sequencing of dissociated tumors enables the profiling of cellular states in fine detail, but erases the cellular organization of the analyzed tissue. Spatially resolved transcriptomics (SRT) using 10X Genomics’ Visium platform combines histological staining and RNA sequencing by capturing each transcript across spatially barcoded microarrays. SRT yields gene-expression matrices resolved within 55-micron array spots, and creates opportunities to explore how lung biology is affected by lung adenocarcinoma and how tumor cells and the proximal microenvironment are modulated by targeted therapy.

Methods: SRT reactions (n=8) were performed on surgical specimens from human lung adenocarcinomas driven by kinase domain mutations of EGFR (exon 19 deletion, L858R point mutation, exon 20 insertion). SRT reactions analyzed primary lung cancer (n=5) or paired tumor-adjacent lung tissues (n=3).

Results: 28458 array spots were recorded across all samples, and array spots captured a median of 5800 total transcripts and a median of 2416 unique transcripts. Single marker gene expression and unsupervised clustering across array spots corresponded with histological annotations of lung structures and adenocarcinoma. Integration of single-cell RNA sequencing data from lung adenocarcinoma specimens permitted mapping and quantification of 15 major cell types, including cancer cells, T- and B- lymphocytes, macrophages, dendritic cells, fibroblasts, and endothelial cells. Compared with paired tumor-adjacent lung tissues, adenocarcinoma tissues contained fibroblast-enriched desmoplasia and B-cell enriched tertiary lymphoid structures. In a clinical case with resistance to Osimertinib, the standard tyrosine kinase inhibitor, gene signature analysis of cancer-containing array spots revealed enrichment of gap-junction, fatty acid metabolism, and kynurenine pathway signatures compared to treatment naïve array spots.

Conclusion: This pilot study demonstrates the feasibility of using SRT in lung adenocarcinoma. Paired with a single-cell atlas of lung adenocarcinoma during targeted therapy, this approach enables hypothesis-generation to investigate the alterations of tumor and tumor microenvironmental architecture in relation to targeted therapy.

Citation Format: Daniel L. Kerr, Wei Wu, Whitney Tamaki, Anatoly Urisman, Yu-Ting Chou, Philippe Gui, David M. Jablons, Trever G. Bivona, Collin M. Blakely. Spatially resolved transcriptomics of cellular architecture in EGFR-mutated lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3808.

Abstract 5354: 3-phosphoinositide-dependent kinase-1 (PDK1, PDPK1) is a driver of osimertinib acquired resistance in EGFR mutant NSCLC

Osimertinib, the only third-generation EGFR-TKI, showed incomplete responses to T790M-mutant NSCLC due to acquired resistance caused by activation of bypass pathways. We developed osimertinib-acquired resistant H1975-OSIR (T790M/L858R mutant) isogenic cells and TC386-OSIR isogenic PDXs. Neither H1975-OSIR nor TC386-OSIR PDXs developed additional mutations in EGFR. The H1975-OSIR clone showed 100 fold higher resistance to osimertinib compared with H1975 cells. TC386-OSIR PDX was developed through continuous in-vivo treatment for 8 months and the residual PDXs were passaged for several generations under continuous osimertinib treatment. TC386-OSIR fourth resistant generation (RG4) showed significantly higher resistance than initial generations (RG1). H1975-OSIR xenografts were developed in non-humanized and humanized NSG mice under osimertinib pressure. H1975-OsiR tumors were significantly less sensitive to osimertinib than their parental counterparts in both mouse models. Dose dependent antitumor activity of osimertinib (5mg/kg and 10mg/kg) was observed in H1975-parental tumors, whereas no treatment effect was observed for H1975-OsiR tumors with increasing doses. The tumor microenvironment was enriched with higher infiltration of tumor associated macrophages (TAM) and lower numbers of tumor infiltrating lymphocytes (TIL) in H1975-OSIR vs H1975 tumors. RPPA analysis of residual tumor tissues showed a distinct set of proteins upregulated in H1975-OsiR vs H1975-parental, among which PDK1 was the most upregulated. PDK1 was also significantly upregulated in H1975-OsiR tumors treated with osimertinib vs controls. PDK1 was not altered in any treatment groups in H1975-parental tumors. PDK1 and pPDK1 expression was many-fold higher in both H1975-OSIR cells and TC386-OSIR PDXs as compared to their parental counterparts by western blot and mass spec proteomics. Selective inhibition by the PDK inhibitor, BX 795, and CRISPR knock-out (KO) restored osimertinib sensitivity in resistant cells. Colony forming assays showed that the PDK1 KO clone was as sensitive as H1975-parental cells whereas a PDK overexpressing clone (OE) restored resistance. In-vivo inhibition of PDK1 by treating mice with BX-795 in both H1975-OSIR xenografts and TC386-OSIR PDXs significantly enhanced the antitumor activity of osimertinib. PDK1 KO dysregulated PI3K/Akt/mTOR signaling by downregulating Akt and mTOR phosphorylation and promoted cell cycle arrest at the G1 phase. NCI-H1975-OSIR and PDK1 OE cells showed a high level of nuclear localization of the activated Yes-associated protein pYAP(Y357). PDK1 KO cells significantly reduced nuclear localization of pYAP(Y357). The level of YAP and pYAP was upregulated in osimertinib resistant xenograft tumors and residual tumor biopsies. Taken together, we identified PDK1 as a drug able target to treat osimertinib acquired resistance.

Citation Format: Ismail M. Meraz, Mourad Majidi, Bingliang Fang, Feng Meng, Lihui Gao, RuPing Shao, Renduo Song, Feng Li, Min Jin Ha, Qi Wang, Jing Wang, Elizabeth Shpall, Sung Yun Jung, Franziska Haderk, Philippe Gui, Jonathan W. Riess, Victor Olivas, Trever G. Bivona, Jack A. Roth. 3-phosphoinositide-dependent kinase-1 (PDK1, PDPK1) is a driver of osimertinib acquired resistance in EGFR mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5354.

Evolution of metastasis: new tools and insights

Metastasis is an evolutionary process occurring across multiple organs and timescales. Due to its continuous and dynamic nature, this multifaceted process has been challenging to investigate and remains incompletely understood, in part due to the lack of tools capable of probing genomic evolution at high enough resolution. However, technological advances in genetic sequencing and editing have provided new and powerful methods to refine our understanding of the complex series of events that lead to metastatic dissemination. In this review, we summarize the latest genetic and lineage-tracing approaches developed to unravel the genetic evolution of metastasis. The findings that have emerged have enhanced our comprehension of the mechanistic trajectories and timescales of metastasis and could provide new strategies for therapy.

Stepwise evolution of therapy resistance in AML

Relapse of AML patients to FLT3i treatment is the result of a long-term and stepwise process leading to resistance, whereby residual cancer cells initially survive and subsequently expand. Here, Joshi et al. use a multifaceted approach to characterize how microenvironment-driven early resistance to gilteritinib evolves into mutation-driven late resistance.

Abstract 2753: Deciphering macrophage function in lung tumor microenvironment and disease progression

Introduction: Lung cancer is the leading cause of cancer-related mortality, with non-small cell lung cancer (NSCLC) as the most common form. Targeting the immune system with immune checkpoint inhibitors has transformed NSCLC treatment, highlighting the crucial contribution of immune cells and the tumor microenvironment (TME) to NSCLC initiation and progression. However, oncogenic-driven cancers treated with targeted molecular therapies have not benefited from immunotherapy, suggesting that other mechanisms of disease progression and resistance are involved. Macrophages in the lung TME are associated with disease outcomes but their exact role in tumor progression and resistance is less well understood. Characterizing their function using high-resolution methods, such as single cell RNA sequencing (scRNAseq), has the potential to identify mechanisms by which macrophages promote lung cancer progression and drug resistance.

Methods: We performed scRNAseq analyses on individual human NSCLC tumor biopsies collected at different treatment states. Samples were obtained from patients before initiating systemic targeted therapy (treatment-naïve, TN), at the residual disease state, which includes samples taken at any time during treatment with targeted therapy while the tumor was regressing or at a stable state by standard clinical imaging (residual disease, RD), and upon the subsequent and clear progressive disease, as determined by standard clinical imaging, at which point the tumors had establishment of acquired drug resistance (progressive disease, PD). Samples were primarily EGFR-, BRAF-, and ALK-driven tumors. Macrophages from lung tumor biopsies were identified and annotated using SingleR, which is a computational method for unbiased cell type recognition of scRNAseq, and then characterized.

Results: We identified 678 macrophages that clustered into 7 distinct groups (Figure 1A). Clusters MF0, MF1, MF3, and MF5 had significant differences across treatment time points. Cluster MF0 had significantly less RD cells and was characterized by expression of genes associated with neutrophil and leukocyte recruitment. Cluster MF5 had significantly more PD cells and was characterized by expression of genes associated with T-cell activation (Figures 1B and 1C).

Conclusion: We annotated macrophages in the lung TME using scRNAseq and characterized macrophage changes across different treatment states. Our findings suggest there are less macrophages recruiting neutrophils and leukocytes in RD compared to TN and PD, and more T-cell activating macrophages in PD compared to TN and RD, which could have potential therapeutic and prognostic implications.

Citation Format: Elizabeth A. Yu, Wei Wu, Philippe Gui, Caroline E. McCoach, Collin M. Blakely, Stephanie A. Christenson, Trever G. Bivona. Deciphering macrophage function in lung tumor microenvironment and disease progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2753.

Abstract LB124: APOBEC3B fuels evolution of resistance during targeted cancer therapy

Despite recent advances in cancer treatment, lung cancer remains the leading cause of cancer mortality worldwide. Lung adenocarcinoma is the most prevalent subtype of lung cancer. Genomic profiling of lung adenocarcinomas has led to the identification of several targetable oncogenic drivers. Therapies targeting the oncogenic-driver pathway using various tyrosine kinase inhibitors (TKIs), are effective initially but responses are often transient and tumors eventually regrow due to drug resistance. Furthermore, drug resistance can arise via the selection of pre-existing resistant clones or via the de novo acquisition of mutations that are not present before therapy. We set out to understand the mechanism for the de novo acquisition of drug resistance mutations in oncogene-driven lung cancers. To do so, we investigated the gene expression changes that occur upon inhibition of oncogenic pathways. We found that oncoprotein targeted therapy induces adaptations favorable for APOBEC genome mutagenesis. Treatment with small molecule inhibitors against EGFR and ALK promoted transcriptional upregulation of members of APOBEC family of cytidine deaminases and downregulation of the uracil glycosylase UNG, the key protein needed for removal of APOBEC-induced DNA lesions. These changes in mRNA levels resulted in functional effects that can impact nuclear DNA by increasing nuclear APOBEC activity and reducing nuclear uracil excision capacity. Determination of changes in APOBEC mRNA levels and nuclear APOBEC activity over time and depletion studies identified APOBEC3B as a driver of both baseline and targeted therapy-induced nuclear APOBEC activity in pre-clinical lung cancer models. We found that APOBEC3B mediates genetic evolution and emergence of resistance during targeted therapy. We identified NF-kB pathway induction and c-Jun downregulation as key mediators of these treatment-induced molecular changes. Furthermore, we find an upregulation of APOBEC3B in lung cancer patients with progressive disease and a high proportion of APOBEC-associated mutations in patient tumors treated with targeted therapy. Some putative resistance mutations in patient tumors were also in the APOBEC-preferred context. Our study identifies a novel targeted therapy-induced evolutionary process involving an APOBEC DNA deaminase that could serve as an attractive co-target to elicit more durable treatment responses.

Citation Format: Manasi K. Mayekar, Deborah Caswell, Natalie Vokes, Wei Wu, Caroline McCoach, Collin Blakely, Nuri Alpay Temiz, Daniel Lucas Kerr, Julia Rotow, Franziska Haderk, Lauren Cech, Beatrice Gini, Shigeki Nanjo, Lisa Tan, Johnny Yu, Carlos Gomez, Philippe Gui, Elizabeth Yu, Nicholas Thomas, Julian Downward, Reuben Harris, Eliezer Van Allen, Charles Swanton, Trever Bivona. APOBEC3B fuels evolution of resistance during targeted cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB124.

Characterization of the tumor microenvironment landscape and deep learning-guided prediction of prognosis in lung adenocarcinoma with bulk RNA sequencing data

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Background: The tumor microenvironment (TME) plays an important role in tumor progression and treatment response, therefore profoundly affecting patient outcomes. Efforts to characterize the TME in lung adenocarcinoma are emerging but have been limited by the sample size and lack of treatment timepoints. Methods: We characterized changes in lung TME using the xCell algorithm to distinguish 64 immune and stroma cell types from bulk RNA sequencing data. The correlation between subtype cell population in lung TME and various clinical and biological characteristics was analyzed from over 500 lung adenocarcinoma (LUAD) samples from The Cancer Genome Atlas and an independent cohort of 48 advanced LUAD patients with treatment annotations (treatment-naive, residual disease, and progressive disease). In addition, we used key features in lung TME to predict prognosis using deep learning algorithms. Results: We found significant changes in both immune and stroma cell populations according to various clinical parameters such as smoking history, cancer stage, and treatment status. Specific sub-populations within lung TME correlate with survival outcomes based on Kaplan-Meier survival analyses. CD4- and CD8-positive T-cells are enriched in early stage disease and depleted in late stage disease, suggesting evolution of the TME during cancer progression. Consistent with previous reports, scores of immune cell populations associated with worse survival, such as T helper type 2 cells, are increased in late stage disease. Smoking history also reshapes the lung TME as populations correlated with better survival are decreased in smokers. We also found variations in sub-populations according to the driver oncogenes, with a less abundant lymphoid compartment in EGFR mutant samples compared to KRAS driven samples. Interestingly, we found higher scores of macrophage populations in residual disease following targeted-therapy treatment compared to pre-treatment. Finally, using machine and deep learning methods we identified a panel of 12 key features within the lung TME which could be used to predict prognosis. Conclusions: We comprehensively characterized immune and stroma cell type changes in the lung TME utilizing bulk RNA-seq data, and evaluated the association of sub-type cell populations with different clinical and biological features. Key features in lung TME could be used to predict prognosis.

Co-occurring Alterations in the RAS-MAPK Pathway Limit Response to MET Inhibitor Treatment in MET Exon 14 Skipping Mutation-Positive Lung Cancer

PURPOSE

Although patients with advanced-stage non-small cell lung cancers (NSCLC) harboring MET exon 14 skipping mutations (METex14) often benefit from MET tyrosine kinase inhibitor (TKI) treatment, clinical benefit is limited by primary and acquired drug resistance. The molecular basis for this resistance remains incompletely understood.

EXPERIMENTAL DESIGN

Targeted sequencing analysis was performed on cell-free circulating tumor DNA obtained from 289 patients with advanced-stage METex14-mutated NSCLC.

RESULTS

Prominent co-occurring RAS-MAPK pathway gene alterations (e.g., in KRAS, NF1) were detected in NSCLCs with METex14 skipping alterations as compared with EGFR-mutated NSCLCs. There was an association between decreased MET TKI treatment response and RAS-MAPK pathway co-occurring alterations. In a preclinical model expressing a canonical METex14 mutation, KRAS overexpression or NF1 downregulation hyperactivated MAPK signaling to promote MET TKI resistance. This resistance was overcome by cotreatment with crizotinib and the MEK inhibitor trametinib.

CONCLUSIONS

Our study provides a genomic landscape of co-occurring alterations in advanced-stage METex14-mutated NSCLC and suggests a potential combination therapy strategy targeting MAPK pathway signaling to enhance clinical outcomes.

Synthetic Essentiality of Metabolic Regulator PDHK1 in PTEN-Deficient Cells and Cancers

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor and bi-functional lipid and protein phosphatase. We report that the metabolic regulator pyruvate dehydrogenase kinase1 (PDHK1) is a synthetic-essential gene in PTEN-deficient cancer and normal cells. The PTEN protein phosphatase dephosphorylates nuclear factor κB (NF-κB)-activating protein (NKAP) and limits NFκB activation to suppress expression of PDHK1, a NF-κB target gene. Loss of the PTEN protein phosphatase upregulates PDHK1 to induce aerobic glycolysis and PDHK1 cellular dependence. PTEN-deficient human tumors harbor increased PDHK1, a biomarker of decreased patient survival. This study uncovers a PTEN-regulated signaling pathway and reveals PDHK1 as a potential target in PTEN-deficient cancers.

Rho/ROCK pathway inhibition by the CDK inhibitor p27(kip1) participates in the onset of macrophage 3D-mesenchymal migration

Infiltration of macrophages into tissue can promote tumour development. Depending on the extracellular matrix architecture, macrophages can adopt two migration modes: amoeboid migration--common to all leukocytes, and mesenchymal migration--restricted to macrophages and certain tumour cells. Here, we investigate the initiating mechanisms involved in macrophage mesenchymal migration. We show that a single macrophage is able to use both migration modes. Macrophage mesenchymal migration is correlated with decreased activity of Rho/Rho-associated protein kinase (ROCK) and is potentiated when ROCK is inhibited, suggesting that amoeboid inhibition participates in mechanisms that initiate mesenchymal migration. We identify the cyclin-dependent kinase (CDK) inhibitor p27(kip1) (also known as CDKN1B) as a new effector of macrophage 3D-migration. By using p27(kip1) mutant mice and small interfering RNA targeting p27(kip1), we show that p27(kip1) promotes mesenchymal migration and hinders amoeboid migration upstream of the Rho/ROCK pathway, a process associated with a relocation of the protein from the nucleus to the cytoplasm. Finally, we observe that cytoplasmic p27(kip1) is required for in vivo infiltration of macrophages within induced tumours in mice. This study provides the first evidence that silencing of amoeboid migration through inhibition of the Rho/ROCK pathway by p27(kip1) participates in the onset of macrophage mesenchymal migration.

Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.

Regulation of ion channels by protein tyrosine phosphorylation

Ion channels are regulated by protein phosphorylation and dephosphorylation of serine, threonine, and tyrosine residues. Evidence for the latter process, tyrosine phosphorylation, has increased substantially since this topic was last reviewed. In this review, we present a comprehensive summary and synthesis of the literature regarding the mechanism and function of ion channel regulation by protein tyrosine kinases and phosphatases. Coverage includes the majority of voltage-gated, ligand-gated, and second messenger-gated channels as well as several types of channels that have not yet been cloned, including store-operated Ca2+ channels, nonselective cation channels, and epithelial Na+ and Cl- channels. Additionally, we discuss the critical roles that channel-associated scaffolding proteins may play in localizing protein tyrosine kinases and phosphatases to the vicinity of ion channels.

Protective effect of rhubarb on endotoxin-induced acute lung injury

To approach the mechanism of lipopolysaccharide (LPS) in causing acute lung injury (ALI) and the protective effect of rhubarb and dexamethasone, lung specimens were examined with macroscopy, microscopy, electron microscopy and the biological markers of ALI including lung wet/dry weight, the rate of neutrophils and protein content in the pulmonary alveolar lavage fluid, pulmonary capillary permeability and pulmonary alveolar permeability index were observed. The mechanism of the ALI is mainly due to direct injury of alveolar epithelium and pulmonary vascular endothelium. Rhubarb and dexamethasone could significantly reduce the edema of the lung tissue, decrease the red blood cell exudation, neutrophil infiltration and plasma protein exudation in the alveoli and all the biological markers in comparison with the ALI model rats, indicating they have protective action on vascular endothelium and alveolar epithelium.

Actions of NO and INOS on endotoxin induced rat acute lung injury and effect of rhubarb on them

This study is to explore the actions of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) on endotoxin (lipopolysaccharide, LPS) induced rat acute lung injury (ALI) and effect of Rhubarb on them. LPS was injected into the sublingual vein of male Wistar rats to prepare ALI animal models. The rats were divided into 4 groups: LPS, control, Rhubarb, and dexamethasone. Macroscopic and histopathological examinations of the lung specimens were performed and the biological indexes of lung, including wet weight/dry weight, the rate of neutrophils and protein content in the pulmonary alveolar lavage fluid, pulmonary vascular permeability and pulmonary alveolar permeability were observed. In the mean time, the contents of serum NO and the activities of lung tissue homogenate iNOS were measured. The results showed that in the LPS group, the injury and celluar infiltration in the pulmonary stroma and alveoli were more prominent than that in the control group. Lung wet weight/dry weight, the rate of neutrophils, protein content, pulmonary alveolar permeability, pulmonary vascular permeability were significantly increased (P < 0.01); NO and iNOS were also markedly elevated (P < 0.01). In the groups of dexamethasone and Rhubarb, the histopathological changes were significantly milder, and all the above biological indexes of lung injury and the contents of NO and the activities of iNOS were correspondingly decreased (P < 0.05). The above data demonstrate that NO and iNOS play an important role in the onset of ALI; dexamethasone and Rhubarb interfering treatment can ameliorate lung injury and decrease the concentrations of NO and the activities of iNOS, showing that through inhibiting the levels of NO and the activities of iNOS, these 2 agents exert protective effect on ALI induced LPS.