Hypoxia-Responsive CAR-T Cells Exhibit Reduced Exhaustion and Enhanced Efficacy in Solid Tumors

Expanding the utility of chimeric antigen receptor (CAR)-T cells in solid tumors requires improving their efficacy and safety. Hypoxia is a feature of most solid tumors that could be used to help CAR-T cells discriminate tumors from normal tissues. In this study, we developed hypoxia-responsive CAR-T cells by engineering the CAR to be under regulation of hypoxia-responsive elements and selected the optimal structure (5H1P-CEA CAR), which can be activated in the tumor hypoxic microenvironment to induce CAR-T cells with high polyfunctionality. Hypoxia-responsive CAR T cells were in a "resting" state with low CAR expression under normoxic conditions. Compared with conventional CAR-T cells, hypoxia-responsive CAR-T cells maintained lower differentiation and displayed enhanced oxidative metabolism and proliferation during cultivation, and they sowed a capacity to alleviate the negative effects of hypoxia on T-cell proliferation and metabolism. Furthermore, 5H1P-CEA CAR-T cells exhibited decreased T-cell exhaustion and improved T-cell phenotype in vivo. In patient-derived xenograft models, hypoxia-responsive CAR-T cells induced more durable antitumor activity than their conventional counterparts. Overall, this study provides an approach to limit CAR expression to the hypoxic tumor microenvironment that could help to enhance CAR T-cell efficacy and safety in solid tumors.

SIGNIFICANCE

Engineering CAR-T cells to upregulate CAR expression under hypoxic conditions induces metabolic reprogramming, reduces differentiation, and increases proliferation to enhance their antitumor activity, providing a strategy to improve efficacy and safety.

Spatial heterogeneity of tumor microenvironment influences the prognosis of clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is an immunologically and histologically diverse tumor. However, how the structural heterogeneity of tumor microenvironment (TME) affects cancer progression and treatment response remains unclear. Hence, we characterized the TME architectures of ccRCC tissues using imaging mass cytometry (IMC) and explored their associations with clinical outcome and therapeutic response.

METHODS

Using IMC, we profiled the TME landscape of ccRCC and paracancerous tissue by measuring 17 markers involved in tissue architecture, immune cell and immune activation. In the ccRCC tissue, we identified distinct immune architectures of ccRCC tissue based on the mix score and performed cellular neighborhood (CN) analysis to subdivide TME phenotypes. Moreover, we assessed the relationship between the different TME phenotypes and ccRCC patient survival, clinical features and treatment response.

RESULTS

We found that ccRCC tissues had higher levels of CD8⁺ T cells, CD163^- macrophages, Treg cells, endothelial cells, and fibroblasts than paracancerous tissues. Immune infiltrates in ccRCC tissues distinctly showed clustered and scattered patterns. Within the clustered pattern, we identified two subtypes with different clinical outcomes based on CN analysis. The TLS-like phenotype had cell communities resembling tertiary lymphoid structures, characterized by cell-cell interactions of CD8⁺ T cells-B cells and GZMB⁺CD8⁺ T cells-B cells, which exhibited anti-tumor features and favorable outcomes, while the Macrophage/T-clustered phenotype with macrophage- or T cell-dominated cell communities had a poor prognosis. Patients with scattered immune architecture could be further divided into scattered-CN-hot and scattered-CN-cold phenotypes based on the presence or absence of immune CNs, but both had a better prognosis than the macrophage/T-clustered phenotype. We further analyzed the relationship between the TME phenotypes and treatment response in five metastatic ccRCC patients treated with sunitinib, and found that all three responders were scattered-CN-hot phenotype while both non-responders were macrophage/T-clustered phenotype.

CONCLUSION

Our study revealed the structural heterogeneity of TME in ccRCC and its impact on clinical outcome and personalized treatment. These findings highlight the potential of IMC and CN analysis for characterizing TME structural units in cancer research.

BEX1 mediates sorafenib resistance in hepatocellular carcinoma by regulating AKT signaling

Sorafenib is the first-line therapy for advanced hepatocellular carcinoma (HCC). However, acquired tolerance after sorafenib treatment significantly limits its therapeutic efficacy, and the mechanisms underlying resistance remains poorly characterized. In this study, we identified BEX1 as key mediator of sorafenib resistance in HCC. We found that BEX1 expression was significantly reduced in sorafenib-resistant HCC cells and xenograft models, moreover, BEX1 expression in HCC tissues was down-regulated compared with that normal liver tissues in The Cancer Genome Atlas (TCGA) database, K-M analysis demonstrated that reduced BEX1 expression was correlated with poor clinical prognosis in HCC patients. Loss- and gain-of-function studies showed that BEX1 regulates the cell-killing ability of sorafenib. Further studies revealed that BEX1 renders HCC cells sensitive to sorafenib via induction of apoptosis and negatively regulates the phosphorylation of Akt. In summary, our study uncover BEX1 may serve as a promising predictive biomarker for the prognosis of patients with HCC.

SIRT1 promotes glucolipid metabolic conversion to facilitate tumor development in colorectal carcinoma

Background: Fatty acid oxidation (FAO) is a major alternate energy metabolism pathway in tumor cells subjected to metabolic stress caused by glucose deficiency during rapid progression. However, the mechanism of metabolic reprogramming between glycolysis and FAO in tumor cells is unknown. Therefore, identifying the metabolic glucolipid conversion hub in tumor cells is crucial. Methods: We used single-cell RNA sequencing (scRNA-Seq), RNA sequencing (RNA-Seq), The Cancer Genome Atlas (TCGA), and chromatin immunoprecipitation sequencing (ChIP-Seq) to predict the critical regulator and mechanism of metabolic glucolipid conversion in colorectal cancer (CRC) tumor cells. We used Seahorse metabolic analysis, immunoblotting, immunofluorescence, and immunohistochemical (IHC) technology to verify the prediction and mechanism of this regulator in cancer cell lines, a nude mouse xenograft model, and clinical CRC samples. Results: We demonstrated that sirtuin-1 (SIRT1) was upregulated in CRC cells in response to glucose deprivation and oxidative stress. SIRT1 was also a hub of metabolic glucolipid conversion. SIRT1 upregulation deacetylated β-catenin, translocated it from the nucleus to the cytoplasm, attenuated glycolysis, and was positively correlated with fatty acid oxidation (FAO). Clinical analysis of SIRT1 expression in tumor tissues showed the SIRT1^High profile was associated with poor prognosis in CRC patients. SIRT1 interference therapy significantly suppressed tumors in the mouse xenograft model. Conclusions: In hostile, glucose-deficient TMEs, SIRT1 is upregulated, and CRC cells transform the Warburg phenotype to FAO. SIRT1 indicates the frequency of glucolipid transformation and rapid tumor progression and is a promising therapeutic target of CRC.

Clopidogrel monotherapy following dual antiplatelet therapy in patients with acute coronary syndrome post-drug-eluting stent implantation: a systematic review and direct/indirect treatment comparison

Background

In patients with acute coronary syndromes (ACS) receiving a drug-eluting stent (DES), treatment with dual antiplatelet therapy (DAPT) reduces the risk of recurrent ischemic events. Optimal duration of DAPT depends on patient characteristics and switching to single antiplatelet therapy (SAPT) is recommended after the course of DAPT.

Purpose

The aim of this study was to evaluate the comparative efficacy and safety of switching to clopidogrel SAPT following DAPT in patients with ACS post DES-implantation.

Methods

A systematic literature review (SLR) was conducted by searching MEDLINE®, Embase, and CENTRAL up to July 27, 2021. Randomized controlled trials (RCTs) and observational studies that evaluated clopidogrel SAPT following DAPT in adults with ACS post-DES implantation were included. Heterogeneity of included studies was vetted in a feasibility assessment. Random effects meta-analyses were conducted using the metafor package for R. Direct comparisons were conducted for clopidogrel vs. aspirin and clopidogrel vs. DAPT. Using the Bucher method, aspirin vs. DAPT was indirectly compared by taking the difference between their respective pooled treatment effects vs. clopidogrel. A sensitivity analysis was conducted by including studies with a follow-up of 12 months.

Results

Of 5,349 records identified, seven unique studies (four RCTs and three observational studies) were eligible to be included in the SLR and quantitative treatment comparison. Risk of major adverse cardiovascular events (MACE) was lower in patients who switched to clopidogrel SAPT after DAPT compared with those who switched to aspirin monotherapy (hazard ratio [HR]: 0.72; 95% confidence interval [CI]: 0.54, 0.98), and this difference was significant. No significant difference in risk of MACE was found between switching to clopidogrel SAPT after DAPT and continuation of DAPT (HR: 0.90; 95% CI: 0.65, 1.25). This finding was consistent with the sensitivity analysis representing studies with follow-up of 12 months (HR: 0.95; 95% CI: 0.69, 1.31). Risk of bleeding was not analysed due to insufficient data across included studies for patients with ACS. However, within-study findings from one RCT of 4,136 patients demonstrated a significantly lower risk of bleeding, defined as thrombolysis in myocardial infarction (major and/or minor, for switching to clopidogrel SAPT following DAPT compared with continuation of DAPT (0.54% vs. 1.17% of patients had bleeding [HR: 0.46; 95% CI: 0.23, 0.94]).

Conclusion

Findings from this SLR suggest switching to clopidogrel SAPT after DAPT in ACS post-DES implantation has a lower risk of MACE compared with switching to aspirin monotherapy, and no difference in the risk of MACE compared with continuation of DAPT. There was insufficient data across the included studies to evaluate the bleeding risk, however, a single study indicated a lower bleeding risk with switching to clopidogrel SAPT.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Sanofi

Effects of Atomoxetine Hydrochloride on Regulation of Lifespan in Drosophila Model

Nootropics (smart drugs) are used by students to enhance cognitive performance which have been reported times in recent years. However, some of the nootropics are central nervous system stimulants which are very likely to lead to addiction or complications such as vomiting and dizziness. Are there nootropics that can improve learning behavior while having potential positive effect on health? Here, we reported that Atomoxetine (ATX) has sex-specific effect on prolonging the life span of female Drosophila melanogaster. Further study indicated that ATX enhanced female resistance to heat stress and their vertical climbing ability, but it did decrease the number of eggs laid. ATX increased food-intake and sleep time both of females and males, and significantly reduced the 24h spontaneous activity of females and males. Our results present the sex dimorphic effect of ATX on life span regulation in Drosophila, and support further research on the beneficial role of ATX and the mechanisms in other animal models.

Functionalized nanoparticles with monocyte membranes and rapamycin achieve synergistic chemoimmunotherapy for reperfusion-induced injury in ischemic stroke

Background

Ischemic stroke is an acute and severe neurological disease, and reperfusion is an effective way to reverse brain damage after stroke. However, reperfusion causes secondary tissue damage induced by inflammatory responses, called ischemia/reperfusion (I/R) injury. Current therapeutic strategies that control inflammation to treat I/R are less than satisfactory.

Results

We report a kind of shield and sword nano-soldier functionalized nanoparticles (monocyte membranes-coated rapamycin nanoparticles, McM/RNPs) that can reduce inflammation and relieve I/R injury by blocking monocyte infiltration and inhibiting microglia proliferation. The fabricated McM/RNPs can actively target and bind to inflammatory endothelial cells, which inhibit the adhesion of monocytes to the endothelium, thus acting as a shield. Subsequently, McM/RNPs can penetrate the endothelium to reach the injury site, similar to a sword, and release the RAP drug to inhibit the proliferation of inflammatory cells. In a rat I/R injury model, McM/RNPs exhibited improved active homing to I/R injury areas and greatly ameliorated neuroscores and infarct volume. Importantly, in vivo animal studies revealed good safety for McM/RNPs treatment.

Conclusion

The results demonstrated that the developed McM/RNPs may serve as an effective and safe nanovehicles for I/R injury therapy.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01067-0.

CD9, a potential leukemia stem cell marker, regulates drug resistance and leukemia development in acute myeloid leukemia

BACKGROUND

Leukemia stem cells (LSCs) are responsible for the initiation, progression, and relapse of acute myeloid leukemia (AML). Therefore, a therapeutic strategy targeting LSCs is a potential approach to eradicate AML. In this study, we aimed to identify LSC-specific surface markers and uncover the underlying mechanism of AML LSCs.

METHODS

Microarray gene expression data were used to investigate candidate AML-LSC-specific markers. CD9 expression in AML cell lines, patients with AML, and normal donors was evaluated by flow cytometry (FC). The biological characteristics of CD9-positive (CD9⁺) cells were analyzed by in vitro proliferation, chemotherapeutic drug resistance, migration, and in vivo xenotransplantation assays. The molecular mechanism involved in CD9⁺ cell function was investigated by gene expression profiling. The effects of alpha-2-macroglobulin (A2M) on CD9⁺ cells were analyzed with regard to proliferation, drug resistance, and migration.

RESULTS

CD9, a cell surface protein, was specifically expressed on AML LSCs but barely detected on normal hematopoietic stem cells (HSCs). CD9⁺ cells exhibit more resistance to chemotherapy drugs and higher migration potential than do CD9-negative (CD9^-) cells. More importantly, CD9⁺ cells possess the ability to reconstitute human AML in immunocompromised mice and promote leukemia growth, suggesting that CD9⁺ cells define the LSC population. Furthermore, we identified that A2M plays a crucial role in maintaining CD9⁺ LSC stemness. Knockdown of A2M impairs drug resistance and migration of CD9⁺ cells.

CONCLUSION

Our findings suggest that CD9 is a new biomarker of AML LSCs and is a promising therapeutic target.

Disruption of SIRT7 Increases the Efficacy of Checkpoint Inhibitor via MEF2D Regulation of Programmed Cell Death 1 Ligand 1 in Hepatocellular Carcinoma Cells

BACKGROUND & AIMS

Immune checkpoint inhibitors have some efficacy in the treatment of hepatocellular carcinoma (HCC). Programmed cell death 1 ligand 1 (PD-L1), expressed on some cancer cells, binds to the receptor programmed cell death 1 (PDCD1, also called PD1) on T cells to prevent their proliferation and reduce the antigen-tumor immune response. Immune cells that infiltrate some types of HCCs secrete interferon gamma (IFNG). Some HCC cells express myocyte enhancer factor 2D (MEF2D), which has been associated with shorter survival times of patients. We studied whether HCC cell expression of MEF2D regulates expression of PD-L1 in response to IFNG.

METHODS

We analyzed immune cells from 20 fresh HCC tissues by flow cytometry. We analyzed 225 fixed HCC tissues (from 2 cohorts) from patients in China by immunohistochemistry and obtained survival data. We created mice with liver-specific knockout of MEF2D (MEF2D^LPC-KO mice). We knocked out or knocked down MEF2D, E1A binding protein p300 (p300), or sirtuin 7 (SIRT7) in SMMC-7721, Huh7, H22, and Hepa1-6 HCC cell lines, some incubated with IFNG. We analyzed liver tissues from mice and cell lines by RNA sequencing, immunoblot, dual luciferase reporter, and chromatin precipitation assays. MEF2D protein acetylation and proteins that interact with MEF2D were identified by coimmunoprecipitation and pull-down assays. H22 cells, with MEF2D knockout or without (controls), were transplanted into BALB/c mice, and some mice were given antibodies to deplete T cells. Mice bearing orthotopic tumors grown from HCC cells, with or without knockout of SIRT7, were given injections of an antibody against PD1. Growth of tumors was measured, and tumors were analyzed by immunohistochemistry and flow cytometry.

RESULTS

In human HCC specimens, we found an inverse correlation between level of MEF2D and numbers of CD4⁺ and CD8⁺ T cells; level of MEF2D correlated with percentages of PD1-positive or TIM3-positive CD8⁺ T cells. Knockout of MEF2D from H22 cells reduced their growth as allograft tumors in immune-competent mice but not in immune-deficient mice or mice with depletion of CD8⁺ T cells. When MEF2D-knockout cells were injected into immune-competent mice, they formed smaller tumors that had increased infiltration and activation of T cells compared with control HCC cells. In human and mouse HCC cells, MEF2D knockdown or knockout reduced expression of PD-L1. MEF2D bound the promoter region of the CD274 gene (encodes PD-L1) and activated its transcription. Overexpression of p300 in HCC cells, or knockout of SIRT7, promoted acetylation of MEF2D and increased its binding, along with acetylated histones, to the promoter region of CD274. Exposure of HCC cells to IFNG induced expression of p300 and its binding MEF2D, which reduced the interaction between MEF2D and SIRT7. MEF2D-induced expression of PD-L1 upon IFNG exposure was independent of interferon-regulatory factors 1 or 9. In HCC cells not exposed to IFNG, SIRT7 formed a complex with MEF2D that attenuated expression of PD-L1. Knockout of SIRT7 reduced proliferation of HCC cells and growth of tumors in immune-deficient mice. Compared with allograft tumors grown from control HCC cells, in immune-competent mice, tumors grown from SIRT7-knockout HCC cells expressed higher levels of PD-L1 and had reduced infiltration and activation of T cells. In immune-competent mice given antibodies to PD1, allograft tumors grew more slowly from SIRT7-knockout HCC cells than from control HCC cells.

CONCLUSIONS

Expression of MEF2D by HCC cells increases their expression of PD-L1, which prevents CD8⁺ T-cell-mediated antitumor immunity. When HCC cells are exposed to IFNG, p300 acetylates MEF2D, causing it to bind the CD274 gene promoter and up-regulate PD-L1 expression. In addition to promoting HCC cell proliferation, SIRT7 reduced acetylation of MEF2D and expression of PD-L1 in HCC cells not exposed to IFNG. Strategies to manipulate this pathway might increase the efficacy of immune therapies for HCC.

LINC00324 exerts tumor-promoting functions in lung adenocarcinoma via targeting miR-615-5p/AKT1 axis

OBJECTIVE

The underlying mechanism of long non-coding RNA (lncRNA) in lung adenocarcinoma (LAC) has not been fully understood yet. Hence, this study aimed to determine the biological function of LINC00324 in LAC and to provide a novel diagnostic and therapeutic target for it.

PATIENTS AND METHODS

The expression level of LINC00324 in 87 paired LAC tumor tissues and matched para-tumor tissues was detected using quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Cell counting kit-8 (CCK-8) assay was employed to analyze the cell proliferative ability, whereas flow cytometry was performed to detect cell apoptotic rate. Cell metastasis change was measured using wound-healing assay and transwell assay. Luciferase reporter gene assay and Western blotting analysis were utilized to investigate the underlying mechanism of LINC00324 in LAC.

RESULTS

LINC00324 was highly expressed in LAC tissues compared with the para-tumor samples. Identically, the expression level of LINC00324 was significantly higher in LAC cell lines. The overexpression of LINC00324 promoted cell proliferation and inhibited cell apoptosis of LAC cells, while knockdown of LINC00324 presented the opposite effect. Up-regulation of LINC00324 accelerated cell migration and invasion, but down-regulation of LINC0324 decreased cell metastasis of LAC cells. Furthermore, miR-615-5p was found to be regulated by LINC00324 and inhibited AKT1 expression, indicating that LINC00324 promoted cell progression via affecting the miR-615-5p/AKT1 pathway.

CONCLUSIONS

LINC00324 was significantly over-expressed in LAC tissues and cells. It promoted proliferation and metastasis but inhibited cell apoptosis of LAC cells via sponging miR-615-5p to promote AKT1 expression. Our results demonstrated LINC00324 as a novel diagnostic and therapeutic target for LAC.

Sirtuin-1/Mitochondrial Ribosomal Protein S5 Axis Enhances the Metabolic Flexibility of Liver Cancer Stem Cells

Metabolic reprogramming endows cancer cells with the ability to adjust metabolic pathways to support heterogeneously biological processes. However, it is not known how the reprogrammed activities are implemented during differentiation of cancer stem cells (CSCs). In this study, we demonstrated that liver CSCs relied on the enhanced mitochondrial function to maintain stemness properties, which is different from aerobic glycolysis playing main roles in the differentiated non-CSCs. We found that liver CSCs exhibit increased mitochondrial respiratory capacity and that complex-I of mitochondria was necessary for stemness properties of liver CSCs through regulation of mitochondrial respiration. Bioinformatics analysis reveals that mitochondrial ribosomal protein S5 (MRPS5) is closely related with the function of complex-I. Further experiments confirmed that MRPS5 promoted the production of nicotinamide adenine dinucleotide (NAD⁺ ), which is necessary for enhanced mitochondrial function in liver CSCs. MRPS5 played a critical role for liver CSCs to maintain stemness properties and to participate in tumor progression. Mechanistically, the acetylation status of MRPS5 is directly regulated by NAD⁺ dependent deacetylase sirtuin-1 (SIRT1), which is abundant in liver CSCs and decreased during differentiation. Deacetylated MRPS5 locates in mitochondria to promote the function complex-I and the generation of NAD⁺ to enhance mitochondrial respiration. Conversely, the acetylated MRPS5 gathered in nuclei leads to increased expression of glycolytic proteins and promotion of the Warburg Effect. Therefore, liver CSCs transform mitochondrial-dependent energy supply to a Warburg phenotype by the dual function of MRPS5. Clinical analysis of SIRT1 and MRPS5 expression in tumor tissues showed the SIRT1^High /Cytoplasmic-MRPS5^High profile was associated with patients with hepatocellular carcinoma with poor prognosis. Conclusion: SIRT1/MRPS5 axis participates in metabolic reprogramming to facilitate tumor progression and may serve as a promising therapeutic target of liver cancer.

Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids

Magnons in ferromagnets behave as a viscous fluid over a length scale, the momentum-relaxation length, below which momentum-conserving scattering processes dominate. We show theoretically that in this hydrodynamic regime viscous effects lead to a sign change in the magnon chemical potential, which can be detected as a sign change in the nonlocal resistance measured in spin transport experiments. This sign change is observable when the injector-detector distance becomes comparable to the momentum-relaxation length. Taking into account momentum- and spin-relaxation processes, we consider the quasiconservation laws for momentum and spin in a magnon fluid. The resulting equations are solved for nonlocal spin transport devices in which spin is injected and detected via metallic leads. Because of the finite viscosity we also find a backflow of magnons close to the injector lead. Our work shows that nonlocal magnon spin transport devices are an attractive platform to develop and study magnon-fluid dynamics.

Tcf7l1 Acts as a Suppressor for the Self-Renewal of Liver Cancer Stem Cells and Is Regulated by IGF/MEK/ERK Signaling Independent of β-Catenin

Tcf7l1, which is a key effector molecule of the Wnt/β-catenin signaling pathway, is highly expressed in various cancers, and it promotes tumor growth. In this study, we demonstrated that unlike its tumor-promoting effects in several other types of cancers, Tcf7l1 expression is downregulated in hepatocarcinoma compared with their adjacent nontumor counterparts. Underexpression of Tcf7l1 is correlated with poorer survival. In liver cancer stem cell (CSC) populations, Tcf7l1 expression is downregulated. Ectopic expression of Tcf7l1 attenuates the self-renewal abilities of liver CSCs. Mechanistically, Tcf7l1 regulates the self-renewal abilities of liver CSCs through transcriptional repression of the Nanog gene, and the effect is independent of β-catenin. Moreover, we found that Tcf7l1 expression is controlled by extracellular insulin-like growth factor (IGF) signaling, and we demonstrated for the first time that IGF signaling stimulates Tcf7l1 phosphorylation and degradation through the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway. Overall, our results provide some new insights into how extracellular signals modulate the self-renewal of liver CSCs and highlight the inhibitory roles of Tcf7l1 in cancer. Stem Cells 2019;37:1389-1400.

KIAA1199 promotes sorafenib tolerance and the metastasis of hepatocellular carcinoma by activating the EGF/EGFR-dependent epithelial-mesenchymal transition program

Patients with advanced hepatocellular carcinoma (HCC) will almost always develop acquired tolerance after sorafenib therapy, and the molecular mechanism of sorafenib tolerance remains poorly characterized. Here, using our established sorafenib-resistant HCC cell and xenograft models, we identified a novel gene, KIAA1199, which was markedly elevated among the differentially expressed genes involved in sorafenib tolerance. Moreover, elevated expression of KIAA1199 was positively correlated with a high risk of recurrence and metastasis and advanced TNM stage in HCC patients. Functionally, loss- and gain-of-function studies showed that KIAA1199 promoted the migration, invasion, and metastasis of sorafenib-resistant HCC cells. Mechanistically, KIAA1199 is required for EGF-induced epithelial-mesenchymal transition (EMT) in sorafenib-resistant HCC cells by aiding in EGFR phosphorylation. In summary, our data uncover KIAA1199 as a novel sorafenib-tolerant promoting gene that plays an indispensable role in maintaining sorafenib-resistant HCC cell metastasis.

[Prospective association between childhood abuse experiences and depressive symptoms in adolescence]

Objective: To evaluate the prospective association between childhood abuse experiences and depressive symptoms in adolescence. Methods: Students in grade 3 and 4 from three primary schools were selected, with informed consent, through convenience cluster sampling in Bengbu, Anhui province in May 2013. The students' body height, weight were assessed. Childhood abuse experiences including emotional, physical or sexual abuses, as well as depressive symptoms were reported by children themselves. Data on parental educational background and household economic status were collected through parent questionnaire. A follow up was conducted 4 years later after baseline survey. Depressive symptoms were evaluated by using Children's Depression Inventory at baseline survey, and by using Mood and Feeling Questionnaire at follow-up. Logistic regression model was used to analyze the relationship between childhood abuse experiences and depressive symptoms in adolescence. Results: A total of 1 172 students were included in baseline survey, and a follow-up was conducted for 87.1% of them (n=1 021). Among 1 126 students with complete information on childhood abuse experiences at baseline survey, the reported rates of physical, emotional and sexual abuses were 12.8% (144/1 126), 11.1% (125/1 126) and 10.9% (123/1 126), respectively. The prevalence of depressive symptoms at baseline survey and follow-up was 7.0% (82/1 172) and 12.3% (126/1 021), respectively. After adjusted for baseline depressive symptoms, age at follow-up, sex, the only-child in family, household economic status, divorce of parents and BMI, childhood emotional and physical abuse experiences were significant risk factors for depressive symptoms in mid-adolescence, with the ORs were 1.86 (95%CI: 1.03-3.36, P=0.039) and 2.37 (95%CI: 1.39-4.03, P=0.001), respectively. Conclusion: Childhood physical and emotional abuse might increase the risk of depressive symptoms in adolescence.

Association of size-fractionated indoor particulate matter and black carbon with heart rate variability in healthy elderly women in Beijing

Associations between size-fractionated indoor particulate matter (PM) and black carbon (BC) and heart rate variability (HRV) and heart rate (HR) in elderly women remain unclear. Twenty-nine healthy elderly women were measured for 24-hour HRV/HR indices. Real-time size-fractionated indoor PM and BC were monitored on the same day and on the preceding day. Mixed-effects models were applied to investigate the associations between pollutants and HRV/HR indices. Increases in size-fractionated indoor PM were significantly associated with declines in power in the high-frequency band (HF), power in the low-frequency band (LF), and standard deviation of all NN intervals (SDNN). The largest decline in HF was 19% at 5-minute moving average for an interquartile range (IQR) increase (24 μg/m³ ) in PM_0.5 . The results showed that smaller particles could lead to greater reductions in HRV indices. The reported associations were modified by body mass index (BMI): Declines in HF at 5-minute average for an IQR increase in PM_0.5 were 34.5% and 1.0% for overweight (BMI ≥25 kg/m² ) and normal-weight (BMI <25 kg/m² ) participants, respectively. Moreover, negative associations between BC and HRV indices were found to be significant in overweight participants. Increases in size-fractionated indoor PM and BC were associated with compromised cardiac autonomic function in healthy elderly women, especially overweight ones.

[Therapeutic effects of psychological intervention combined with manual reduction on benign paroxysmal positional vertigo in the elderly]

Objective:To explore the best treatment for elderly patients with benign paroxysmal positional vertigo (BPPV). Method:Sixty-eight BPPV patients aged 60-85 years were randomly divided into two groups. The control group was treated by simple manipulation. The study group was treated by manual reduction combined with psychological intervention. The curative effect was compared. Result:The cure rates of the control group and the study group were 44.4% and 43.8% respectively, with no significant difference (P>0.05); the effective rates were 52.78% and 87.50% respectively, with significant difference (P<0.05). The recurrence rates of control group and study group were 8.3% and 3.1% after 2 weeks of treatment, respectively, with no significant difference (P>0.05). The recurrence rates at 3 months were 5.6% and 0 respectively, with no significant difference (P>0.05). The difference of SAS and SDS between the two groups after treatment was statistically significant (P<0.05). There was no significant difference in the residual symptoms between the two groups at the first follow-up (P>0.05), and at 1 week and 4 weeks (P<0.05). The residual symptoms of the patients after reoperation were relieved compared with those of the control group. The DHI scores of the study group between 60-70 years old and 71-85 years old group for the first time, after 1 week and 4 weeks were statistically significant (P<0.05), and the residual symptoms in the 60-70 years group were reduced compare to the 71-85-year-old group. Conclusion:Elderly people with BPPV are susceptible to anxiety and depression. Manipulation combined with psychological intervention can promote the curative effect well, but personalized treatment plan should be developed.

MEK1 signaling promotes self-renewal and tumorigenicity of liver cancer stem cells via maintaining SIRT1 protein stabilization

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death. This high mortality has been commonly attributed to the presence of residual cancer stem cells (CSCs). Meanwhile, MEK1 signaling is regarded as a key molecular in HCC maintenance and development. However, nobody has figured out the particular mechanisms that how MEK1 signaling regulates liver CSCs self-renewal. In this study, we show that inhibition or depletion of MEK1 can significantly decrease liver CSCs self-renewal and tumor growth both in vitro and vivo conditions. Furthermore, we demonstrate that MEK1 signaling promotes liver CSCs self-renewal and tumorigenicity by maintaining SIRT1 level. Mechanistically, MEK1 signaling keeps SIRT1 protein stabilization through activating SIRT1 ubiquitination, which inhibits proteasomal degradation. Clinical analysis shows that patients co-expression of MEK1 and SIRT1 are associated with poor survival. Our finding indicates that MEK1-SIRT1 can act as a novel diagnostic biomarker and inhibition of MEK1 may be a viable therapeutic option for targeting liver CSCs treatment.

Androgen/androgen receptor axis maintains and promotes cancer cell stemness through direct activation of Nanog transcription in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common and malignant cancers. The HCC incidence gets a strong sexual dimorphism as men are the major sufferers in this disaster. Although several studies have uncovered the presentative correlation between the axis of androgen/androgen receptor (AR) and HCC incidence, the mechanism is still largely unknown. Cancer stem cells (CSCs) are a small subgroup of cancer cells contributing to multiple tumors malignant behaviors, which play an important role in oncogenesis of various cancers including HCC. However, whether androgen/AR axis involves in regulation of HCC cells stemness remains unclear. Our previous study had identified that the pluripotency factor Nanog is not only a stemness biomarker, but also a potent regulator of CSCs in HCC. In this study, we revealed androgen/AR axis can promote HCC cells stemness by transcriptional activation of Nanog expression through directly binding to its promoter. In HCC tissues, we found that AR expression was abnormal high and got correlation with Nanog. Then, by labeling cellular endogenous Nanog with green fluorescent protein (GFP) through CRISPR/Cas9 system, it verified the co-localization of AR and Nanog in HCC cells. With in vitro experiments, we demonstrated the axis can promote HCC cells stemness, which effect is in a Nanog-dependent manner and through activating its transcription. And the xenografted tumor experiments confirmed the axis effect on tumorigenesis facilitation in vivo. Above all, we revealed a new sight of androgen/AR axis roles in HCC and provided a potential way for suppressing the axis in HCC therapy.

Blood pressure control over time in childhood-onset systemic lupus erythematous

Introduction Hypertension (HTN) is prevalent in patients with systemic lupus erythematosus (SLE) and causes early cardiovascular aging and progression of renal and cardiac disease. The aim of this longitudinal retrospective study was to evaluate the prevalence of HTN, the follow-up blood pressure trends, and risk factors for HTN in a population-based cohort with childhood-onset SLE (cSLE). Methods Demographic and clinical data of consecutive visits from the baseline to the last visit were extracted from electronic medical records of patients with cSLE. Results A total of 110 patients with cSLE were identified with a median follow-up duration of 29.5 months; 19% had lupus nephritis (LN) at diagnosis. Further, 29% and 23% had HTN and preHTN at the baseline visit. Compared to those without HTN, patients with HTN had higher disease activity, obesity, more frequent LN, and lower eGFR. In multivariate analysis, the presence of LN, obesity, and high extra-renal disease activity were independent predictors of HTN at baseline. Conclusions While HTN is a known feature of LN, HTN is common and persistent in cSLE without LN, with about one-third of patients having uncontrolled elevated blood pressure almost three years after the onset of lupus. In addition to LN, obesity and high overall disease activity were independent predictors of HTN.

LSD1 Stimulates Cancer-Associated Fibroblasts to Drive Notch3-Dependent Self-Renewal of Liver Cancer Stem-like Cells

Cancer stem-like cells (CSC) in hepatocellular carcinoma (HCC) are thought to mediate therapeutic resistance and poor survival outcomes, but their intrinsic and extrinsic control is not well understood. In this study, we found that the chromatin modification factor LSD1 is highly expressed in HCC CSC where it decreases during differentiation. LSD1 was responsible for maintaining CSC self-renewal and tumorigenicity in HCC, and its overexpression was sufficient to drive self-renewal of non-CSC. Levels of acetylated LSD1 were low in CSC with high LSD1 activity, and these CSC were capable of self-renewal. Notch signaling activated LSD1 through induction of the sirtuin SIRT1, leading to deacetylation and activation of LSD1 and CSC self-renewal. Notably, we found that LSD1 expression was increased in cancer-associated fibroblasts (CAF) as an upstream driver of Notch3-mediated CSC self-renewal. In clinical specimens of HCC, the presence of CAF, LSD1, and Notch3 strongly associated with poor patient survival. Overall, our results reveal that CAF-induced expression of Notch3 is responsible for LSD1 activation in CSC, driving their self-renewal in HCC.Significance: These seminal findings illuminate a complex pathway in the tissue microenvironment of liver cancer, which is responsible for orchestrating the self-renewal of stem-like cancer cells, with potential implications to improve therapy and limit relapses. Cancer Res; 78(4); 938-49. ©2017 AACR.

MicroRNA-449a maintains self-renewal in liver cancer stem-like cells by targeting Tcf3

Cancer stem cells (CSCs) are thought to be responsible for tumor invasion, metastasis, and recurrence. We previously showed that the pluripotency factor Nanog not only serves as a novel biomarker of CSCs but also potentially plays a crucial role in maintaining the self-renewal ability of liver CSCs. However, how CSCs maintain Nanog gene expression has not been elucidated. Here, we demonstrated that microRNA-449a (miR-449a) is overexpressed in poorly differentiated hepatocellular carcinoma tissues, drug-resistant liver cancer cells, cultured liver tumorspheres, and Nanog-positive liver cancer cells. The upregulation of miR-449a in non-CSCs increased stemness, whereas the downregulation of miR-449a in Nanog-positive CSCs reduced stemness. Furthermore, transcription factor 3 (TCF3), a target of miR-449a, could downregulate Nanog expression, and restoring TCF3 expression in miR-449a-expressing Nanog-negative cells abrogated cellular stemness. These data establish that the miR449a-TCF3-Nanog axis maintains stemness in liver CSCs.

[The effect of short-term exposure to ambient NO(2) on lung function and fractional exhaled nitric oxide in 33 chronic obstructive pulmonary disease patients]

Objectives: To investigate the effect of short-term exposure to ambient NO(2) has influence on lung function and fractional exhaled nitric oxide (FeNO) in chronic obstructive pulmonary disease (COPD) patients. Methods: A panel of doctor-diagnosed stable COPD patients (n=33) were recruited and repeatedly measured for lung function and FeNO from December 2013 to October 2014. The patients who lived in Beijing for more than one year and aged between 60 and 85 years old were included in the study. We excluded patients with asthma, bronchial tensor, lung cancer and other respiratory disorders other than chronic obstructive pulmonary disease and occupational exposure and chest trauma surgery patients. Because the frequency of each subject visiting to the hospital was different, a total of 170 times of lung function measurements and 215 times of FeNO measurements were conducted. At the same time, the atmospheric NO(2) data of Beijing environmental monitoring station near the residence of each patient during the study period were collected from 1 day to 7 days lag before the measurement. Effects of short-term NO(2) exposure on lung function and FeNO in COPD patients were estimated by linear mixed-effects models. Results: The subjects' forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)), peak expiratory flow (PEF), and exhaled NO of subjects were (3.26±0.83) L, (1.66±0.61) L, (4.13±1.77) L/s, and (48.99±14.30) μg/m(3), respectively. The concentration of NO(2) was (70.3±34.2) μg/m(3) and the interquartile range (IQR) was 39.0 μg/m(3). Short-term exposure to NO(2) resulted in a significant decrease in FVC among COPD patients' which was most obvious in 2 days lag. Every quartile range increased in NO(2) (39 μg/m(3), 2 day) would cause a 1.84% (95%CI: -3.20%- -0.48%) reduction in FVC. The effects of exposure to higher concentration of NO(2) (≥58.0 μg/m(3)) on FVC estimate was -2.32% (95%CI: -4.15%- -0.48%)(P=0.02). No significant relevance of FeNO and NO(2) was observed in this study. Conclusions: Short term exposure to ambient NO(2) may bring down pulmonary function in COPD patients.

Bioinformatics analysis of RNA-seq data revealed critical genes in colon adenocarcinoma

OBJECTIVE

RNA-seq data of colon adenocarcinoma (COAD) were analyzed with bioinformatics tools to discover critical genes in the disease. Relevant small molecule drugs, transcription factors (TFs) and microRNAs (miRNAs) were also investigated.

MATERIALS AND METHODS

RNA-seq data of COAD were downloaded from The Cancer Genome Atlas (TCGA). Differential analysis was performed with package edgeR. False positive discovery (FDR) < 0.05 and |log2 (fold change)|>1 were set as the cut-offs to screen out differentially expressed genes (DEGs). Gene coexpression network was constructed with package Ebcoexpress. GO enrichment analysis was performed for the DEGs in the gene coexpression network with DAVID. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was also performed for the genes with KOBASS 2.0. Modules were identified with MCODE of Cytoscape. Relevant small molecules drugs were predicted by Connectivity map. Relevant miRNAs and TFs were searched by WebGestalt.

RESULTS

A total of 457 DEGs, including 255 up-regulated and 202 down-regulated genes, were identified from 437 COAD and 39 control samples. A gene coexpression network was constructed containing 40 DEGs and 101 edges. The genes were mainly associated with collagen fibril organization, extracellular matrix organization and translation. Two modules were identified from the gene coexpression network, which were implicated in muscle contraction and extracellular matrix organization, respectively. Several critical genes were disclosed, such as MYH11, COL5A2 and ribosomal proteins. Nine relevant small molecule drugs were identified, such as scriptaid and STOCK1N-35874. Accordingly, a total of 17 TFs and 10 miRNAs related to COAD were acquired, such as ETS2, NFAT, AP4, miR-124A, MiR-9, miR-96 and let-7.

CONCLUSIONS

Several critical genes and relevant drugs, TFs and miRNAs were revealed in COAD. These findings could advance the understanding of the disease and benefit therapy development.

Myocyte enhancer factor 2D promotes colorectal cancer angiogenesis downstream of hypoxia-inducible factor 1α

Myocyte enhancer factor 2D (MEF2D) is involved in many aspects of cancer progression, including cell proliferation, invasion, and migration. However, little is known about the role of MEF2D in tumor angiogenesis. Using clinical specimens, colorectal cancer (CRC) cell lines and a mouse model in the present study, we found that MEF2D expression was positively correlated with CD31-positive microvascular density in CRC tissues. MEF2D promoted tumor angiogenesis in vitro and in vivo and induced the expression of proangiogenic cytokines in CRC cells. MEF2D was found to be a downstream effector of hypoxia-inducible factor (HIF)-1α in the induction of tumor angiogenesis. HIF-1α transactivates MEF2D expression by binding to the MEF2D gene promoter. These results demonstrate that the HIF-1α/MEF2D axis can serve as a therapeutic target for the treatment of CRC.

[Surveillance on the epidemiological and etiological characteristics of hand-foot-mouth disease during the outbreaks in three cities of Jiangsu province, 2012-2015]

Objective: To analyze the epidemiological and etiological characteristics through monitoring the outbreaks of hand-foot-mouth disease (HFMD), in three cities of Jiangsu province from 2012 to 2015 and to provide evidence for prevention and control of the disease. Methods: Data related to cases of HFMD during the outbreaks was collected through active surveillance programs in three cities of Jiangsu province, under the guidelines of clusters and outbreaks of HFMD (2012 edition HFMD). Features related to clusters and outbreaks of the disease were identified according to the real-time RT-PCR detection. Descriptive analysis was conducted to understand the type/subtype of HFMD virus and time, area, place and extent of the outbreaks. Logistic regression was used to explore the influencing factors. Results: From 2012 to 2015, a total of 1 425 HFMD epidemics, including 1 314 clusters and 111 outbreaks were reported. Two incidence peaks were observed each year, between March and June, as well as between September and December, accounting for 58.18% (829/1 425), 33.68% (480/1 425), respectively. Most HFMD clusters and outbreaks were reported in Wuxi city, accounting for 59.30% (845/1 425) of the total. Most HFMD clusters and outbreaks happened in kindergartens, accounting for 68.63% (978/1 425) of the total. A total of 931 HFMD clusters and outbreaks were confirmed under laboratory findings. The main pathogens were Entervirus type 71 (EV71) in 2013 and Coxsackie A16 (Cox A16) in 2015, respectively, while both EV71 and Cox A16 were predominant in 2012 and 2014. With multivariate backward conditional regression, surrounding environment was identified as important risk factor associated with the attack rate. Health condition of the environment was quite good, with low attack rates (middle vs. bad: OR=0.150, 95% CI: 0.034-0.667; good vs. bad: OR=0.072, 95%CI: 0.016-0.317). Time between the onset of index patient and the reporting of HFMD clusters or outbreaks was important in the control program of HFMD epidemics (4-7 d vs. 1-3 d: OR=3.452, 95%CI: 2.293-5.198; 8 d vs. 1-3 d: OR=12.108, 95%CI: 7.767-18.763). Conclusions: The clusters and outbreaks of HFMD happened in Jiangsu province showed an obvious feature of seasonality. The predominant types or subtypes of the virus varied in different years. Kindergartens were the hard-hit places of HFMD clusters and outbreaks. Timely report of the disease appeared the key point regarding the control of HFMD clusters and outbreaks.

SIRT1-mediated transcriptional regulation of SOX2 is important for self-renewal of liver cancer stem cells

Hepatocellular carcinoma (HCC) is a highly aggressive liver tumor containing cancer stem cells (CSCs), which participate in tumor invasion, therapeutic resistance, and tumor relapse leading to poor outcome and limited therapeutic options. Histone deacetylatase sirtuin 1 (SIRT1) has been shown to be up-regulated in human cancers; however, its role in liver CSCs is unknown. In this study, we explored the biological functions of SIRT1 in liver CSCs. Our data show that SIRT1 is highly expressed in liver CSCs and decreases during differentiation. In addition, high levels of SIRT1 predict a decreased probability of survival in patients with HCC. SIRT1 is responsible for the maintenance of self-renewal and tumorigenicity of liver CSCs, and overexpression of exogenous SIRT1 can restore self-renewal of non-CSCs. We demonstrated that SOX2 is a main downstream regulator of SIRT1-mediated self-renewal and tumorigenicity potential of liver CSCs. Mechanistically, SIRT1 regulates transcription of the SOX2 gene by way of chromatin-based epigenetic changes, which are dependent on DNA methylation. This effect is achieved by alternation of histone modification and interaction with DNA methyltransferase 3A, resulting in hypermethylation of SOX2 promoter. Furthermore, we demonstrated that insulin growth factor signaling plays an important role in maintaining SIRT1 expression through increased SIRT1 protein stability.

CONCLUSIONS

These findings highlight the importance of SIRT1 in the biology of liver CSCs and suggest that SIRT1 may serve as a molecular target for HCC therapy. (Hepatology 2016;64:814-827).

Sox9 regulates self-renewal and tumorigenicity by promoting symmetrical cell division of cancer stem cells in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a highly aggressive liver tumor containing cancer stem cells (CSCs) that participate in tumor propagation, resistance to conventional therapy, and promotion of tumor recurrence, causing poor patient outcomes. The protein SRY (sex determining region Y)-box 9 (Sox9) is a transcription factor expressed in some solid tumors, including HCC. However, the molecular mechanisms underlying Sox9 function in liver CSCs remain unclear. Here, we show that Sox9 is highly expressed in liver CSCs and that high levels of Sox9 predict a decreased probability of survival in HCC patients. We demonstrate that Sox9 is required for maintaining proliferation, self-renewal, and tumorigenicity in liver CSCs. Overexpression of exogenous Sox9 in liver non-CSCs restored self-renewal capacity. Additionally, a reduction in the asymmetrical cell division of spheroid-cultured liver CSCs was observed when compared with differentiated cancer cells or liver CSCs with inhibited Notch signaling. Furthermore, we demonstrate that Sox9 is responsible for the asymmetrical-to-symmetrical cell division switch in liver CSCs. Sox9 also negatively regulates Numb expression, contributing to a feedback circuit that maintains Notch activity and directs symmetrical cell division. Clinical analyses revealed that the Sox9(High) Numb(Low) profile is associated with poor prognosis in human HCC patients.

CONCLUSION

We demonstrate that Sox9 plays a critical role in self-renewal and tumor propagation of liver CSCs and identify the molecular mechanisms regulated by Sox9 that link tumor initiation and cell division. (Hepatology 2016;64:117-129).

MEF2D Transduces Microenvironment Stimuli to ZEB1 to Promote Epithelial-Mesenchymal Transition and Metastasis in Colorectal Cancer

Epithelial-mesenchymal transition (EMT) is an essential mechanism of metastasis, including in colorectal cancer. Although EMT processes are often triggered in cancer cells by their surrounding microenvironment, how EMT-relevant genes control these processes is not well understood. In multiple types of cancers, the transcription factor MEF2D has been implicated in cell proliferation, but its contributions to metastasis have not been addressed. Here, we show MEF2D is overexpressed in clinical colorectal cancer tissues where its high expression correlates with metastatic process. Functional investigations showed that MEF2D promoted cancer cell invasion and EMT and that it was essential for certain microenvironment signals to induce EMT and metastasis in vivo Mechanistically, MEF2D directly regulated transcription of the EMT driver gene ZEB1 and facilitated histone acetylation at the ZEB1 promoter. More importantly, MEF2D responded to various tumor microenvironment signals and acted as a central integrator transducing multiple signals to activate ZEB1 transcription. Overall, our results define a critical function for MEF2D in upregulating EMT and the metastatic capacity of colorectal cancer cells. Further, they offer new insights into how microenvironment signals activate EMT-relevant genes and deepen the pathophysiologic significance of MEF2D, with potential implications for the prevention and treatment of metastatic colorectal cancer. Cancer Res; 76(17); 5054-67. ©2016 AACR.

[Effect of air pollution on health service demand of the elderly and middle-age patients with hypertension, cardiovascular and cerebrovascular diseases: based on analysis of data from CHARLS]

OBJECTIVE

To study the association of air pollution with health service demand of the elderly and middle-age patients with cardiovascular and cerebrovascular diseases, and to provide a scientific basis for development of environmental protection policy and health service policy of the Chinese government.

METHODS

This study included survey data on self-evaluated health, outpatient service demand and inpatient service demand of the patients with hypertension, heart disease and stroke in 62 cities of 17 provinces from China Health and Retirement Longitudinal Study (CHARLS) in 2011 and 2013, and combined it with the data on the annual concentrations of inhalable particulate matter (PM(10)), sulfur dioxide(SO(2)) and nitrogen dioxide (NO(2)) of those provinces and cities. Conditional Logistic regression was carried out to assess the possible effects of air pollutants on self-evaluated health and health service utilization.

RESULTS

The results showed that turning points existed in the effects of concentrations of NO(2) and SO(2) on the health service demand of the patients with hypertension, heart disease and stroke. The inpatient service demand of the hypertension patients increased with NO(2) concentration when it was lower than 35.1 μg/m(3) and decreased with NO(2) concentration for higher value. Self-evaluated health of the patients with heart disease and stroke decreased with SO(2) concentration when it was lower than 63.8 μg/m(3) and increased with SO(2) concentration for higher value. In addition, no evidence was found for the association between PM(10) and health service demand.

CONCLUSION

Air pollution may have effects on health service demand of the patients with hypertension,cardiovascular and cerebrovascular diseases, and different air pollutants at high or low concentration may have different health effects.

Optical Coherence in Atomic-Monolayer Transition-Metal Dichalcogenides Limited by Electron-Phonon Interactions

We systematically investigate the excitonic dephasing of three representative transition-metal dichalcogenides, namely, MoS_{2}, MoSe_{2}, and WSe_{2} atomic monolayer thick and bulk crystals, in order to gain a proper understanding of the factors that determine the optical coherence in these materials. Coherent nonlinear optical spectroscopy and temperature dependent absorption, combined with theoretical calculations of the phonon spectra, indicate electron-phonon interactions, to be the limiting factor. Surprisingly, the excitonic dephasing, differs only slightly between atomic monolayers and high quality bulk crystals, which indicates that material imperfections are not the limiting factor in atomically thin monolayer samples. The temperature dependence of the electronic band gap and the excitonic linewidth combined with "ab initio" calculations of the phonon energies and the phonon density of states reveal a strong interaction with the E' and E" phonon modes.