The Dual Role of the NFATc2/galectin-9 Axis in Modulating Tumor-Initiating Cell Phenotypes and Immune Suppression in Lung Adenocarcinoma

Tumor-initiating cells (TICs) resilience and an immunosuppressive microenvironment are aggressive oncogenic phenotypes that contribute to unsatisfactory long-term outcomes in lung adenocarcinoma (LUAD) patients. The molecular mechanisms mediating the interaction between TICs and immune tolerance have not been elucidated. The role of Galectin-9 in oncogenesis and immunosuppressive microenvironment is still unknown. This study explored the potential role of galectin-9 in TIC regulation and immune modulation in LUAD. The results show that galectin-9 supports TIC properties in LUAD. Co-culture of patient-derived organoids and matched peripheral blood mononuclear cells showed that tumor-secreted galectin-9 suppressed T cell cytotoxicity and induced regulatory T cells (Tregs). Clinically, galectin-9 is upregulated in human LUAD. High expression of galectin-9 predicted poor recurrence-free survival and correlated with high levels of Treg infiltration. LGALS9, the gene encoding galectin-9, is found to be transcriptionally regulated by the nuclear factor of activated T cells 2 (NFATc2), a previously reported TIC regulator, via in silico prediction and luciferase reporter assays. Overall, the results suggest that the NFATc2/galectin-9 axis plays a dual role in TIC regulation and immune suppression.

Genome-wide association study of lung adenocarcinoma in East Asia and comparison with a European population

Lung adenocarcinoma is the most common type of lung cancer. Known risk variants explain only a small fraction of lung adenocarcinoma heritability. Here, we conducted a two-stage genome-wide association study of lung adenocarcinoma of East Asian ancestry (21,658 cases and 150,676 controls; 54.5% never-smokers) and identified 12 novel susceptibility variants, bringing the total number to 28 at 25 independent loci. Transcriptome-wide association analyses together with colocalization studies using a Taiwanese lung expression quantitative trait loci dataset (n = 115) identified novel candidate genes, including FADS1 at 11q12 and ELF5 at 11p13. In a multi-ancestry meta-analysis of East Asian and European studies, four loci were identified at 2p11, 4q32, 16q23, and 18q12. At the same time, most of our findings in East Asian populations showed no evidence of association in European populations. In our studies drawn from East Asian populations, a polygenic risk score based on the 25 loci had a stronger association in never-smokers vs. individuals with a history of smoking (Pinteraction = 0.0058). These findings provide new insights into the etiology of lung adenocarcinoma in individuals from East Asian populations, which could be important in developing translational applications.

Targeting GSTP1 as Therapeutic Strategy against Lung Adenocarcinoma Stemness and Resistance to Tyrosine Kinase Inhibitors

Glutathione S-transferase pi (GSTP1), a phase II detoxification enzyme, is known to be overexpressed and mediates chemotherapeutic resistance in lung cancer. However, whether GSTP1 supports cancer stem cells (CSCs) and the underlying mechanisms in lung adenocarcinoma (LUAD) remain largely unknown. This study unveiled that GSTP1 is upregulated in lung CSCs and supports tumor self-renewal, metastasis, and resistance to targeted tyrosine kinase inhibitors of LUAD both in vitro and in vivo. Mechanistically, CaMK2A (calcium/calmodulin-dependent protein kinase 2 isoform A)/NRF2 (nuclear factor erythroid 2-related factor 2)/GSTP1 is uncovered as a regulatory axis under hypoxia. CaMK2A increased GSTP1 expression through phosphorylating the Sersine558 residue of NRF2 and promoting its nuclear translocation, a novel mechanism for NRF2 activation apart from conventional oxidization-dependent activation. Upregulation of GSTP1 in turn suppressed reactive oxygen species levels and supported CSC phenotypes. Clinically, GSTP1 analyzed by immunohistochemistry is upregulated in a proportion of LUAD and serves as a prognostic marker for survival. Using patient-derived organoids from an ALK-translocated LUAD, the therapeutic potential of a specific GSTP1 inhibitor ezatiostat in combination treatment with the ALK inhibitor crizotinib is demonstrated. This study demonstrates GSTP1 to be a promising therapeutic target for long-term control of LUAD through targeting CSCs.

Sub-multiplicative interaction between polygenic risk score and household coal use in relation to lung adenocarcinoma among never-smoking women in Asia

We previously identified 10 lung adenocarcinoma susceptibility loci in a genome-wide association study (GWAS) conducted in the Female Lung Cancer Consortium in Asia (FLCCA), the largest genomic study of lung cancer among never-smoking women to date. Furthermore, household coal use for cooking and heating has been linked to lung cancer in Asia, especially in Xuanwei, China. We investigated the potential interaction between genetic susceptibility and coal use in FLCCA. We analyzed GWAS-data from Taiwan, Shanghai, and Shenyang (1472 cases; 1497 controls), as well as a separate study conducted in Xuanwei (152 cases; 522 controls) for additional analyses. We summarized genetic susceptibility using a polygenic risk score (PRS), which was the weighted sum of the risk-alleles from the 10 previously identified loci. We estimated associations between a PRS, coal use (ever/never), and lung adenocarcinoma with multivariable logistic regression models, and evaluated potential gene-environment interactions using likelihood ratio tests. There was a strong association between continuous PRS and lung adenocarcinoma among never coal users (Odds Ratio (OR) = 1.69 (95% Confidence Interval (CI) = 1.53, 1.87), p=1 × 10^-26). This effect was attenuated among ever coal users (OR = 1.24 (95% CI: 1.03, 1.50), p = 0.02, p-interaction = 6 × 10^-3). We observed similar attenuation among coal users from Xuanwei. Our study provides evidence that genetic susceptibility to lung adenocarcinoma among never-smoking Asian women is weaker among coal users. These results suggest that lung cancer pathogenesis may differ, at least partially, depending on exposure to coal combustion products. Notably, these novel findings are among the few instances of sub-multiplicative gene-environment interactions in the cancer literature.

Nidogen 1-Enriched Extracellular Vesicles Facilitate Extrahepatic Metastasis of Liver Cancer by Activating Pulmonary Fibroblasts to Secrete Tumor Necrosis Factor Receptor 1

In hepatocellular carcinoma (HCC) patients with extrahepatic metastasis, the lung is the most frequent site of metastasis. However, how the lung microenvironment favors disseminated cells remains unclear. Here, it is found that nidogen 1 (NID1) in metastatic HCC cell-derived extracellular vesicles (EVs) promotes pre-metastatic niche formation in the lung by enhancing angiogenesis and pulmonary endothelial permeability to facilitate colonization of tumor cells and extrahepatic metastasis. EV-NID1 also activates fibroblasts, which secrete tumor necrosis factor receptor 1 (TNFR1), facilitate lung colonization of tumor cells, and augment HCC cell growth and motility. Administration of anti-TNFR1 antibody effectively diminishes lung metastasis induced by the metastatic HCC cell-derived EVs in mice. In the clinical perspective, analysis of serum EV-NID1 and TNFR1 in HCC patients reveals their positive correlation and association with tumor stages suggesting the potential of these molecules as noninvasive biomarkers for the early detection of HCC. In conclusion, these results demonstrate the interplay of HCC EVs and activated fibroblasts in pre-metastatic niche formation and how blockage of their functions inhibits distant metastasis to the lungs. This study offers promise for the new direction of HCC treatment by targeting oncogenic EV components and their mediated pathways.

CAMK2A supported tumor initiating cells of lung adenocarcinoma by upregulating SOX2 through EZH2 phosphorylation

Tumor initiating cells (TIC) of lung cancer are mainly induced by stress-related plasticity. Calcium/Calmodulin dependent protein kinase II alpha (CAMK2A) is a key calcium signaling molecule activated by exogenous and endogenous stimuli with effects on multiple cell functions but little is known about its role on TIC. In human lung adenocarcinomas (AD), CAMK2A was aberrantly activated in a proportion of cases and was an independent risk factor predicting shorter survivals. Functionally, CAMK2A enhanced TIC phenotypes in vitro and in vivo. CAMK2A regulated SOX2 expression by reducing H3K27me3 and EZH2 occupancy at SOX2 regulatory regions, leading to its epigenetic de-repression with functional consequences. Further, CAMK2A caused kinase-dependent phosphorylation of EZH2 at T487 with suppression of EZH2 activity. Together, the data demonstrated the CAMK2A-EZH2-SOX2 axis on TIC regulation. This study provided phenotypic and mechanistic evidence for the TIC supportive role of CAMK2A, implicating a novel predictive and therapeutic target for lung cancer.

Tuberculosis infection and lung adenocarcinoma: Mendelian randomization and pathway analysis of genome-wide association study data from never-smoking Asian women

We investigated whether genetic susceptibility to tuberculosis (TB) influences lung adenocarcinoma development among never-smokers using TB genome-wide association study (GWAS) results within the Female Lung Cancer Consortium in Asia. Pathway analysis with the adaptive rank truncated product method was used to assess the association between a TB-related gene-set and lung adenocarcinoma using GWAS data from 5512 lung adenocarcinoma cases and 6277 controls. The gene-set consisted of 31 genes containing known/suggestive associations with genetic variants from previous TB-GWAS. Subsequently, we followed-up with Mendelian Randomization to evaluate the association between TB and lung adenocarcinoma using three genome-wide significant variants from previous TB-GWAS in East Asians. The TB-related gene-set was associated with lung adenocarcinoma (p = 0.016). Additionally, the Mendelian Randomization showed an association between TB and lung adenocarcinoma (OR = 1.31, 95% CI: 1.03, 1.66, p = 0.027). Our findings support TB as a causal risk factor for lung cancer development among never-smoking Asian women.

MRP4 sustains Wnt/β-catenin signaling for pregnancy, endometriosis and endometrial cancer

Rationale: Abnormal Wnt/β-catenin signaling in the endometrium can lead to both embryo implantation failure and severe pathogenic changes of the endometrium such as endometrial cancer and endometriosis. However, how Wnt/β-catenin signaling is regulated in the endometrium remains elusive. We explored possible regulation of Wnt/β-catenin signaling by multi-drug resistance protein 4 (MRP4), a potential target in cancer chemotherapy, and investigated the mechanism.

Methods: Knockdown of MRP4 was performed in human endometrial cells in vitro or in a mouse embryo-implantation model in vivo. Immunoprecipitation, immunoblotting and immunofluorescence were used to assess protein interaction and stability. Wnt/β-catenin signaling was assessed by TOPflash reporter assay and quantitative PCR array. Normal and endometriotic human endometrial tissues were examined. Data from human microarray or RNAseq databases of more than 100 participants with endometriosis, endometrial cancer or IVF were analyzed. In vitro and in vivo tumorigenesis was performed.

Results: MRP4-knockdown, but not its transporter-function-inhibition, accelerates β-catenin degradation in human endometrial cells. MRP4 and β-catenin are co-localized and co-immunoprecipitated in mouse and human endometrium. MRP4-knockdown in mouse uterus reduces β-catenin levels, downregulates a series of Wnt/β-catenin target genes and impairs embryo implantation, which are all reversed by blocking β-catenin degradation. Analysis of human endometrial biopsy samples and available databases reveals significant and positive correlations of MRP4 with β-catenin and Wnt/β-catenin target genes in the receptive endometrium in IVF, ectopic endometriotic lesions and endometrial cancers. Knockdown of MRP4 also inhibits in vitro and in vivo endometrial tumorigenesis.

Conclusion: A previously undefined role of MRP4 in stabilizing β-catenin to sustain Wnt/β-catenin signaling in endometrial cells is revealed for both embryo implantation and endometrial disorders, suggesting MRP4 as a theranostic target for endometrial diseases associated with Wnt/β-catenin signaling abnormality.

NFATc2 enhances tumor-initiating phenotypes through the NFATc2/SOX2/ALDH axis in lung adenocarcinoma

Tumor-initiating cells (TIC) are dynamic cancer cell subsets that display enhanced tumor functions and resilience to treatment but the mechanism of TIC induction or maintenance in lung cancer is not fully understood. In this study, we show the calcium pathway transcription factor NFATc2 is a novel regulator of lung TIC phenotypes, including tumorspheres, cell motility, tumorigenesis, as well as in vitro and in vivo responses to chemotherapy and targeted therapy. In human lung cancers, high NFATc2 expression predicted poor tumor differentiation, adverse recurrence-free and cancer-specific overall survivals. Mechanistic investigations identified NFATc2 response elements in the 3’ enhancer region of SOX2, and NFATc2/SOX2 coupling upregulates ALDH1A1 by binding to its 5’ enhancer. Through this axis, oxidative stress induced by cancer drug treatment is attenuated, leading to increased resistance in a mutation-independent manner. Targeting this axis provides a novel approach for the long-term treatment of lung cancer through TIC elimination.

DOI:http://dx.doi.org/10.7554/eLife.26733.001

Cancer develops when cells become faulty and start to grow uncontrollably. They eventually form lumps or tumors, which may spread to surrounding tissues or even to other areas in the body. One of the reasons why cancer treatment remains a challenge is that there are over 200 types of cells in the body, and there are a lot of moments in the life cycle of a cell when things could go wrong. Researchers have shown that many cancers, including lung cancer, are not only extremely different from patient to patient, but also display great differences between cancer cells within the same tumor.

Increasing evidence suggest that these differences may be caused by a type of cells called tumor initiating cells, or TICs for short. These TICs behave like stem cells and can renew themselves or mature into different types of cells. They are thought to help cancers grow and spread, and even make them resistant to treatments. Previous research has shown that in many types of cancer, the protein NFATc2 helps cancer cells to grow and spread. Until now, however, it was not known if NFATc2 is also important in TICs in lung cancer.

Using human lung cancer cell lines and animal models, Xiao et al. show that the protein NFATc2 stimulates the stem-cell like behavior of TICs. The results showed that TICs had higher levels of the NFATc2 protein than other lung cancer cells that were not TICs. Tumors with higher levels were also more aggressive. When NFATc2 was removed from the cells, they formed smaller tumors and were more sensitive to drug treatment compared to cancer cells with NFATc2.

Further experiments revealed that NFATc2 helped to increase the levels of a protein called Sox2, which gives cells the ability to renew or develop into different cell types. Together, these two proteins stimulated the production of another protein that was already known to play a crucial role in TIC maintenance.

A better understanding of the mechanisms regulating TICs in lung cancer will help scientists tackle new questions about how this cancer progresses and resists to therapy. In the longer-term, combining classic cancer treatments with new therapeutic strategies targeting NFATc2 could make treatments for lung cancer patients more effective.

DOI:http://dx.doi.org/10.7554/eLife.26733.002

Association between GWAS-identified lung adenocarcinoma susceptibility loci and EGFR mutations in never-smoking Asian women, and comparison with findings from Western populations

To evaluate associations by EGFR mutation status for lung adenocarcinoma risk among never-smoking Asian women, we conducted a meta-analysis of 11 loci previously identified in genome-wide association studies (GWAS). Genotyping in an additional 10,780 never-smoking cases and 10,938 never-smoking controls from Asia confirmed associations with eight known single nucleotide polymorphisms (SNPs). Two new signals were observed at genome-wide significance (P < 5 × 10-8), namely, rs7216064 (17q24.3, BPTF), for overall lung adenocarcinoma risk, and rs3817963 (6p21.3, BTNL2) which is specific to cases with EGFR mutations. In further sub-analyses by EGFR status, rs9387478 (ROS1/DCBLD1) and rs2179920 (HLA-DPB1) showed stronger estimated associations in EGFR-positive compared to EGFR-negative cases. Comparison of the overall associations with published results in Western populations revealed that the majority of these findings were distinct, underscoring the importance of distinct contributing factors for smoking and non-smoking lung cancer. Our results extend the catalogue of regions associated with lung adenocarcinoma in non-smoking Asian women and highlight the importance of how the germline could inform risk for specific tumour mutation patterns, which could have important translational implications.

Abstract 3034: Overcoming gefitinib resistance in non-small-cell lung cancer by inducing epidermal growth factor receptor (EGFR) degradation via methionine 790 oxidation

Personalized therapy is becoming a dominant cancer therapeutic strategy, Epidermal Growth Factor Receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been developed to treat non-small-cell lung cancer (NSCLC) patients with EGFR mutation but they only inhibit EGFR phosphorylation, acquired-resistance still remains unavoidable without EGFRT790M removal. Here, we report a new treatment strategy to overcome such drug resistance by selectively inducing EGFRT790M degradation via specific stimulation of methionine 790 (M790) oxidation. The basal reactive oxygen species (ROS) levels in EGFRT790M containing gefitinib-resistant NSCLC cell lines were substantially high and 63 clinical lung tumors showed higher NADPH oxidase 2 (NOX2) expression than 61 normal lung tissues which may contribute to high basal ROS in cancer. Interestingly, only NOX3 was upregulated by sanguinarine, a pharmacological agent to elevate ROS, resulted in EGFR over-oxidation and degradation as well as apoptosis. By contrast, such responses were lacking in EGFRWild-type (WT) cells, suggesting a new promising drug development strategy with wide therapeutic window between EGFRT790M and EGFRWT. Selective EGFRT790M degradation was manipulated by REDOX imbalance between NOX3 and methionine reductase (MsrA). When NOX3 was activated, NADPH, the key substrate of MsrA, was depleted to generate excessive ROS, resulting in inhibition of MsrA physiological reduction function on oxidized-methionine, thus localized methionine 790 oxidation

of EGFRT790M occurred. Furthermore, the in vivo tumor suppression effect of sanguinarine, NOX3 upregulation and EGFR degradation were confirmed. These findings indicate that specific inducing EGFRT790M degradation via manipulating REDOX imbalance between NOX3 and MsrA would be promising strategy for treating gefitinib-resistant NSCLC.

Citation Format: Elaine Lai-Han Leung, Xing-Xing Fan, Maria Pik Wong, Zhi-Hong Jiang, Zhong-Qiu Liu, Xiao-Jun Yao, Lin-Lin Lu, Yan-Ling Zhou, Li-Fong Yau, Vicky Pui-Chi Tin, Liang Liu. Overcoming gefitinib resistance in non-small-cell lung cancer by inducing epidermal growth factor receptor (EGFR) degradation via methionine 790 oxidation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3034.

Female chromosome X mosaicism is age-related and preferentially affects the inactivated X chromosome

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events >2 Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses of 33 women with X mosaicism indicate events preferentially involve the inactive X chromosome. Our results provide further evidence that the sex chromosomes undergo mosaic events more frequently than autosomes, which could have implications for understanding the underlying mechanisms of mosaic events and their possible contribution to risk for chronic diseases.

It is unclear how often genetic mosaicism of chromosome X arises. Here, the authors examine women with cancer and cancer-free controls and show that X chromosome mosaicism occurs more frequently than on autosomes, especially on the inactive X chromosome, but is not linked to non-haematologic cancer risk

Targeting Tyrosine Kinase Inhibitor-Resistant Non-Small Cell Lung Cancer by Inducing Epidermal Growth Factor Receptor Degradation via Methionine 790 Oxidation

AIMS

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been developed to treat non-small cell lung cancer (NSCLC) patients with EGFR mutation, but TKI resistance is common. Almost half of the acquired resistance patients are due to additional T790M mutation on EGFR (EGFR(T790M)), thus overcoming TKI resistance is important. In this study, we aim to investigate the role of reactive oxygen species (ROS) in TKI resistance as well as the molecular and biological effects of EGFR(T790M) after redox manipulation.

RESULTS

The basal ROS levels in EGFR(T790M)-containing TKI-resistant NSCLC cell lines were substantially high. Sixty-three human lung tumors showed higher NADPH oxidase isoform 2 (NOX2) expression than normal lung tissues, which may contribute to high basal ROS in cancer and poor survival. Interestingly, only NOX3 was upregulated by sanguinarine, a pharmacological agent to elevate ROS, and resulted in EGFR overoxidation, degradation, and apoptosis. By contrast, such responses were lacking in EGFR(WT) cells. Selective EGFR(T790M) degradation was manipulated by redox imbalance between NOX3 and methionine reductase A (MsrA). Furthermore, the in vivo tumor suppression effect of sanguinarine, NOX3 upregulation, and EGFR degradation were confirmed.

INNOVATION

We have found a new treatment strategy to overcome TKI resistance by selectively inducing EGFR(T790M) degradation via specific stimulation of methionine 790 (M790) oxidation. It can be achieved via manipulating redox imbalance between NOX3 and MsrA.

CONCLUSION

Targeting EGFR by elevating ROS and redox imbalance is a potential new strategy to develop a new EGFR inhibitor for TKI-resistant patients with a wide therapeutic window between EGFR(T790M) and EGFR(WT).

Meta-analysis of genome-wide association studies identifies multiple lung cancer susceptibility loci in never-smoking Asian women

Genome-wide association studies (GWAS) of lung cancer in Asian never-smoking women have previously identified six susceptibility loci associated with lung cancer risk. To further discover new susceptibility loci, we imputed data from four GWAS of Asian non-smoking female lung cancer (6877 cases and 6277 controls) using the 1000 Genomes Project (Phase 1 Release 3) data as the reference and genotyped additional samples (5878 cases and 7046 controls) for possible replication. In our meta-analysis, three new loci achieved genome-wide significance, marked by single nucleotide polymorphism (SNP) rs7741164 at 6p21.1 (per-allele odds ratio (OR) = 1.17; P = 5.8 × 10(-13)), rs72658409 at 9p21.3 (per-allele OR = 0.77; P = 1.41 × 10(-10)) and rs11610143 at 12q13.13 (per-allele OR = 0.89; P = 4.96 × 10(-9)). These findings identified new genetic susceptibility alleles for lung cancer in never-smoking women in Asia and merit follow-up to understand their biological underpinnings.

Analysis of Heritability and Shared Heritability Based on Genome-Wide Association Studies for Thirteen Cancer Types

BACKGROUND

Studies of related individuals have consistently demonstrated notable familial aggregation of cancer. We aim to estimate the heritability and genetic correlation attributable to the additive effects of common single-nucleotide polymorphisms (SNPs) for cancer at 13 anatomical sites.

METHODS

Between 2007 and 2014, the US National Cancer Institute has generated data from genome-wide association studies (GWAS) for 49 492 cancer case patients and 34 131 control patients. We apply novel mixed model methodology (GCTA) to this GWAS data to estimate the heritability of individual cancers, as well as the proportion of heritability attributable to cigarette smoking in smoking-related cancers, and the genetic correlation between pairs of cancers.

RESULTS

GWAS heritability was statistically significant at nearly all sites, with the estimates of array-based heritability, hl (2), on the liability threshold (LT) scale ranging from 0.05 to 0.38. Estimating the combined heritability of multiple smoking characteristics, we calculate that at least 24% (95% confidence interval [CI] = 14% to 37%) and 7% (95% CI = 4% to 11%) of the heritability for lung and bladder cancer, respectively, can be attributed to genetic determinants of smoking. Most pairs of cancers studied did not show evidence of strong genetic correlation. We found only four pairs of cancers with marginally statistically significant correlations, specifically kidney and testes (ρ = 0.73, SE = 0.28), diffuse large B-cell lymphoma (DLBCL) and pediatric osteosarcoma (ρ = 0.53, SE = 0.21), DLBCL and chronic lymphocytic leukemia (CLL) (ρ = 0.51, SE =0.18), and bladder and lung (ρ = 0.35, SE = 0.14). Correlation analysis also indicates that the genetic architecture of lung cancer differs between a smoking population of European ancestry and a nonsmoking Asian population, allowing for the possibility that the genetic etiology for the same disease can vary by population and environmental exposures.

CONCLUSION

Our results provide important insights into the genetic architecture of cancers and suggest new avenues for investigation.

Characterization of large structural genetic mosaicism in human autosomes

Analyses of genome-wide association study (GWAS) data have revealed that detectable genetic mosaicism involving large (>2 Mb) structural autosomal alterations occurs in a fraction of individuals. We present results for a set of 24,849 genotyped individuals (total GWAS set II [TGSII]) in whom 341 large autosomal abnormalities were observed in 168 (0.68%) individuals. Merging data from the new TGSII set with data from two prior reports (the Gene-Environment Association Studies and the total GWAS set I) generated a large dataset of 127,179 individuals; we then conducted a meta-analysis to investigate the patterns of detectable autosomal mosaicism (n = 1,315 events in 925 [0.73%] individuals). Restricting to events >2 Mb in size, we observed an increase in event frequency as event size decreased. The combined results underscore that the rate of detectable mosaicism increases with age (p value = 5.5 × 10(-31)) and is higher in men (p value = 0.002) but lower in participants of African ancestry (p value = 0.003). In a subset of 47 individuals from whom serial samples were collected up to 6 years apart, complex changes were noted over time and showed an overall increase in the proportion of mosaic cells as age increased. Our large combined sample allowed for a unique ability to characterize detectable genetic mosaicism involving large structural events and strengthens the emerging evidence of non-random erosion of the genome in the aging population.

Interactions between household air pollution and GWAS-identified lung cancer susceptibility markers in the Female Lung Cancer Consortium in Asia (FLCCA)

We previously carried out a multi-stage genome-wide association study (GWAS) on lung cancer among never smokers in the Female Lung Cancer Consortium in Asia (FLCCA) (6,609 cases, 7,457 controls) that identified novel susceptibility loci at 10q25.2, 6q22.2, and 6p21.32, and confirmed two previously identified loci at 5p15.33 and 3q28. Household air pollution (HAP) attributed to solid fuel burning for heating and cooking, is the leading cause of the overall disease burden in Southeast Asia, and is known to contain lung carcinogens. To evaluate the gene-HAP interactions associated with lung cancer in loci independent of smoking, we analyzed data from studies participating in FLCCA with fuel use information available (n = 3; 1,731 cases; 1,349 controls). Coal use was associated with a 30% increased risk of lung cancer (OR 1.3, 95% CI 1.0-1.6). Among the five a priori SNPs identified by our GWAS, two showed a significant interaction with coal use (HLA Class II rs2395185, p = 0.02; TP63 rs4488809 (rs4600802), p = 0.04). The risk of lung cancer associated with coal exposure varied with the respective alleles for these two SNPs. Our observations provide evidence that genetic variation in HLA Class II and TP63 may modify the association between HAP and lung cancer risk. The roles played in the cell cycle and inflammation pathways by the proteins encoded by these two genes provide biological plausibility for these interactions; however, additional replication studies are needed in other non-smoking populations.

Genetic variants associated with longer telomere length are associated with increased lung cancer risk among never-smoking women in Asia: a report from the female lung cancer consortium in Asia

Recent evidence from several relatively small nested case-control studies in prospective cohorts shows an association between longer telomere length measured phenotypically in peripheral white blood cell (WBC) DNA and increased lung cancer risk. We sought to further explore this relationship by examining a panel of seven telomere-length associated genetic variants in a large study of 5,457 never-smoking female Asian lung cancer cases and 4,493 never-smoking female Asian controls using data from a previously reported genome-wide association study. Using a group of 1,536 individuals with phenotypically measured telomere length in WBCs in the prospective Shanghai Women's Health study, we demonstrated the utility of a genetic risk score (GRS) of seven telomere-length associated variants to predict telomere length in an Asian population. We then found that GRSs used as instrumental variables to predict longer telomere length were associated with increased lung cancer risk (OR = 1.51 (95% CI = 1.34-1.69) for upper vs. lower quartile of the weighted GRS, p value = 4.54 × 10(-14) ) even after removing rs2736100 (p value = 4.81 × 10(-3) ), a SNP in the TERT locus robustly associated with lung cancer risk in prior association studies. Stratified analyses suggested the effect of the telomere-associated GRS is strongest among younger individuals. We found no difference in GRS effect between adenocarcinoma and squamous cell subtypes. Our results indicate that a genetic background that favors longer telomere length may increase lung cancer risk, which is consistent with earlier prospective studies relating longer telomere length with increased lung cancer risk.

Imputation and subset-based association analysis across different cancer types identifies multiple independent risk loci in the TERT-CLPTM1L region on chromosome 5p15.33

Genome-wide association studies (GWAS) have mapped risk alleles for at least 10 distinct cancers to a small region of 63 000 bp on chromosome 5p15.33. This region harbors the TERT and CLPTM1L genes; the former encodes the catalytic subunit of telomerase reverse transcriptase and the latter may play a role in apoptosis. To investigate further the genetic architecture of common susceptibility alleles in this region, we conducted an agnostic subset-based meta-analysis (association analysis based on subsets) across six distinct cancers in 34 248 cases and 45 036 controls. Based on sequential conditional analysis, we identified as many as six independent risk loci marked by common single-nucleotide polymorphisms: five in the TERT gene (Region 1: rs7726159, P = 2.10 × 10(-39); Region 3: rs2853677, P = 3.30 × 10(-36) and PConditional = 2.36 × 10(-8); Region 4: rs2736098, P = 3.87 × 10(-12) and PConditional = 5.19 × 10(-6), Region 5: rs13172201, P = 0.041 and PConditional = 2.04 × 10(-6); and Region 6: rs10069690, P = 7.49 × 10(-15) and PConditional = 5.35 × 10(-7)) and one in the neighboring CLPTM1L gene (Region 2: rs451360; P = 1.90 × 10(-18) and PConditional = 7.06 × 10(-16)). Between three and five cancers mapped to each independent locus with both risk-enhancing and protective effects. Allele-specific effects on DNA methylation were seen for a subset of risk loci, indicating that methylation and subsequent effects on gene expression may contribute to the biology of risk variants on 5p15.33. Our results provide strong support for extensive pleiotropy across this region of 5p15.33, to an extent not previously observed in other cancer susceptibility loci.

Abstract 1949: P38MAPK plays a tumor suppressive role through differentiation of ALDHhigh/CD44high tumor iniating cells in primary human lung adenocarcinoma

The p38 MAPK cascade regulates body responses to a wide range of stress stimuli in a context-dependent and tissue-specific manner. The isoform p38alpha (p38) mediates both tumor suppressive and tumor-supportive functions in different cancer models. However, its role in lung cancer is not clear. Since EGFR is frequently mutated in lung adenocarcinomas in non-smoking women and p38 is a downstream target of EGFR signaling, it is possible that p38 plays a tumor-supportive role. Using immunohistochemistry to analyze nuclear activated p38 expression in 90 lung adenocarcinomas, we observed p38 expression was significantly associated with well differentiated compared to poorly-differentiated carcinomas (p&lt;0.001) and better patient outcome (p=0.019, disease-free survival; p=0.03, overall survival). In vitro p38 suppression in lung cancer cell lines did not lead to enhanced cell death. On the other hand, p38 suppression alone or in combination with EGFR inhibition led to increased CD44high/ALDHhigh lung tumor initiating cells (TIC); isolated lung TIC also showed higher p38 expression. Together, the data implicate p38 plays a tumor suppressive role in lung cancer by driving tumor cell differentiation. Disrupting pathways that inhibit p38 expression or enhancement of p38 expression might be useful for lung cancer treatment.

Citation Format: Jing Liu, Lai-han Leung, Zhi-jie Xiao, Vicky PC Tin, Maria Pik Wong. P38MAPK plays a tumor suppressive role through differentiation of ALDHhigh/CD44high tumor iniating cells in primary human lung adenocarcinoma. [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 1949. doi:10.1158/1538-7445.AM2014-1949

Abstract 1939: Calcineurin/NFAT signaling regulates tumor initiating cell properties in non-small cell lung cancer

Background:

Targeting specific pathways responsible for Tumor Initiating Cells (TIC) maintenance is postulated to be an important therapeutic strategy for more effective control of tumors. Nuclear Factors of Activated T-cells (NFATs), consisting of 4 homologues (NFATc1-c4), are calcium-dependent transcription factors that are activated upon dephosphorylation by the protein phosphatase calcineurin. NFAT is known to be involved in T cell activation and differentiation. Recently, its roles in regulating embryonic stem cell proliferation and cancer survival have been reported. However, the involvement of Calcineurin/NFAT signaling in TIC maintenance remains unknown.

Objective:

To study the role of Calcineurin/NFAT in regulating TIC properties in non-small cell lung cancer (NSCLC).

Methods and results:

Analysis of NFAT mRNA expression in a panel of established and early passage patient derived NSCLC cell lines showed NFATc2 and NFATc4 were up-regulated in 92.6% (25 of 27) and 72% (20 of 27) of cancer cells compared to normal bronchial cell line (BEAS-2B), respectively. To study its role in TIC, tumor spheres or flow cytometry-isolated ALDHhigh/CD44high cells were obtained and NFAT expressions and activities were compared between TIC and non-TIC. The expression of NFAT and downstream targets were significantly higher in tumor spheres and ALDHhigh/CD44high cells compared to the corresponding monolayers and ALDHlow/CD44low cells. Correspondingly, luciferase reporter assay also showed higher NFAT activities in tumor spheres compared to monolayers. To study its functional importance, calcineurin and NFAT were inhibited and effects on TIC properties were analyzed. Inhibition of calcineurin by pharmacological inhibitors cyclosporin A (CSA) and FK506 resulted in reduced sphere formation ability, down-regulation of pluripotent genes (SOX2, OCT4, NANOG) and TIC markers (ALDH1A1, CD133, CD166) expression, as well as decreased TIC proportions (ALDHhigh/CD44high and CD133+) by flow cytometry. These effects were verified using siRNA knockdown of PPP3R1 which encodes one of the calcineurin regulatory subunits. Apart from expression changes, stable knockdown of NFATc2 using lentiviral shRNA inhibited in vitro and in vivo tumorigenecity as shown in soft agar colony formation and mice xenografts compared to shRNA control. To explore the clinical relevance of NFAT, NFAT expression levels were analyzed in human resected lung cancers by quantitative PCR and immunohistochemsitry. Results showed that NFATs were significantly up-regulated in clinical NSCLC compared to corresponding normal lung, and higher NFAT expression predicted shorter recurrence free survival.

Conclusions:

Calcineurin/NFAT signaling is active in both NSCLC and lung TIC. It plays an important role in TIC maintenance. Inhibition of this pathway is a promising approach for long term lung cancer control.

Citation Format: Zhi-Jie Xiao, Jing Liu, Vicky Pui-Chi Tin, Maria Pik Wong. Calcineurin/NFAT signaling regulates tumor initiating cell properties in non-small cell lung cancer. [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 1939. doi:10.1158/1538-7445.AM2014-1939

FaSD-somatic: a fast and accurate somatic SNV detection algorithm for cancer genome sequencing data

Recent advances in high-throughput sequencing technologies have enabled us to sequence large number of cancer samples to reveal novel insights into oncogenetic mechanisms. However, the presence of intratumoral heterogeneity, normal cell contamination and insufficient sequencing depth, together pose a challenge for detecting somatic mutations. Here we propose a fast and an accurate somatic single-nucleotide variations (SNVs) detection program, FaSD-somatic. The performance of FaSD-somatic is extensively assessed on various types of cancer against several state-of-the-art somatic SNV detection programs. Benchmarked by somatic SNVs from either existing databases or de novo higher-depth sequencing data, FaSD-somatic has the best overall performance. Furthermore, FaSD-somatic is efficient, it finishes somatic SNV calling within 14 h on 50X whole genome sequencing data in paired samples.

AVAILABILITY AND IMPLEMENTATION

The program, datasets and supplementary files are available at http://jjwanglab.org/FaSD-somatic/.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

High-resolution detection of recurrent aberrations in lung adenocarcinomas by array comparative genomic hybridization and expression analysis of selective genes by quantitative PCR

Genomic abnormalities are the hallmark of cancers and may harbor potential candidate genes important for cancer development and progression. We performed array comparative genomic hybridization (array CGH) on 36 cases of primary lung adenocarcinoma (AD) using an array containing 2621 BAC or PAC clones spanning the genome at an average interval of 1 Mb. Array CGH identified the commonest aberrations consisting of DNA gains within 1p, 1q, 5p, 5q, 7p, 7q, 8q, 11q, 12p, 13q, 16p, 17q, 20q, and losses with 6q, 9p, 10q and 18q. High-level copy gains involved mainly 7p21-p15 and 20q13.3. Dual color fluorescence in situ hybridization (FISH) was performed on a selective locus for validation of array CGH results. Genomic aberrations were compared with different clinicopathological features and a trend of higher number of aberrations in tumors with aggressive phenotypes and current tobacco exposure was identified. According to array CGH data, 23 candidate genes were selected for quantitative PCR (qPCR) analysis. The concordance observed between the genomic and expression changes in most of the genes suggested that they could be candidate cancer-related genes that contributed to the development of lung AD.

Identification and characterization of ALK kinase splicing isoforms in non-small-cell lung cancer

INTRODUCTION

Anaplastic lymphoma kinase (ALK) rearrangements are present in an important subset of non-small-cell lung cancer (NSCLC) and predict for response to the tyrosine kinase inhibitor crizotinib. In this study, we evaluated the yet unknown frequency and functional role of ALK splicing isoforms in NSCLC.

METHODS

We analyzed 270 cases of NSCLC for ALK kinase domain splicing aberrations and in addition generated constructs with full-length echinoderm microtubule-associated protein-like 4 (EML4)-ALK (E13;A20) and a splicing isoform.

RESULTS

Splicing isoforms of the kinase domain of ALK-including complete skipping of exon 23 (ALKdel23, ALK p.I1171fs*42) and exon 27 (ALKdel27, ALK p.T1312fs*0)-were identified in 11.1% (30 of 270 cases) of NSCLC, and these changes coexisted with ALK rearrangements, KRAS mutations, and EGFR mutations. ALK splicing isoforms were observed with full-length EML4-ALK in crizotinib-naive and treated NSCLCs. ALK T1312fs*0 was unable to render cells solely dependent on ALK signaling. Unlike EML4-ALK and EML4-ALK p.L1196M, EML4-ALK T1312fs*0 did not autophosphorylate ALK or other phosphotyrosine sites. Coexpression of equal amounts of EML4-ALK T1312fs*0 and EML4-ALK did not result in resistance to crizotinib, whereas coexpression of EML4-ALK L1196M with EML4-ALK resulted in resistance to inhibition of ALK by crizotinib.

CONCLUSIONS

ALK kinase splicing isoforms were present in NSCLC and even if translated seemed to be nonfunctional variants of ALK.

Abstract 2255: Distinct biological effect of inhibiting the metabolic pathway using active compounds derived from Chinese medicinal herbs in non-small cell lung cancer cells with different EGFR mutational profiles

Lung cancer is the leading cause of cancer death worldwide. Epidermal Growth Factor Receptor (EGFR) mutation(s) is/are common in non-small cell lung cancer (NSCLC) in Eastern Oriental population, resulting in constitutive activation of EGFR downstream anti-apoptotic signaling and lung tumor formation. Molecular targeted therapy using tyrosine kinase inhibitor (TKI) targeting EGFR shows promising initial response, however, drug resistance and relapse are universal, making the treatment outcome undesirable. Drug resistance could be due to additional EGFR mutation or activation of alternative survival pathways. Therefore, it is important to identify new inhibitors and new molecular targets to tackle TKI-resistance. Chinese Medicinal Herbs (CMHs) has been used to treat variety systemic diseases for many years in China, including diabetes, neurodegenerative disease and cancer. The multi-targeting nature and potential alternation effects on metabolic pathways of CMHs could be a new era for novel cancer drug discovery.

Hence, we have reviewed the literature and selected ten single purified compounds derived from CMHs which exhibited the highest potential of cancer suppression effect in NSCLC. We have recruited three EGFR-dependent NSCLC cell lines for drug screening using cytotoxicity assay. A549 is used as EGFR wild-type control. Two TKI-resistant NSCLC cell lines were used, H1975 harbors double mutation (EGFRL858R+T790M) and H1650 harbors EGFRexon 19 deletion with activation of alternative cell survival pathway. H2228 is a NSCLC cell line which harbours EML4-ALK fusion gene and was used as EGFR-independent cell line control. MTT assay revealed that six out of ten candidate agents showed significant cancer-inhibiting effects in H1650, H1975 cells. Three compounds exhibited IC50 value at micro-molar levels while another three compounds exhibited IC50 at as low as nano-molar levels. One compound exhibited specificity on EGFR-dependent NSCLC cell lines, which showed 10-fold more selective than the EGFR-independent H2228 cells.

Cell cycle analysis and western blot showed that one effective compound altered the metabolic pathway of glucose metabolism and induced cell cycle arrest at G1 phase in NSCLC with EGFR mutation. However, the anti-proliferative effects were distinct in NSCLC cell lines with different EGFR mutation patterns. Our compound significantly induced cell cycle arrest in four NSCLC in EGFR mutant cell lines but the inhibiting effect was not significant in EGFR wild-type cell line. Immunobloting assay revealed that glycolytic enzymes and cell cycle regulatory gene expression were altered after 72 hr compound treatment in the responsive cells. Further investigation is required to elucidate the underlying reason of drug selectivity and the treatment mechanism of these compounds.

Citation Format: Xing Xing Fan, Maria Pik Wong, Zhi Wei Cao, Jian Lin Wu, Hua Zhou, Zhi Hong Jiang, Liang Liu, Elaine Lai-Han Leung. Distinct biological effect of inhibiting the metabolic pathway using active compounds derived from Chinese medicinal herbs in non-small cell lung cancer cells with different EGFR mutational profiles. [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 2255. doi:10.1158/1538-7445.AM2013-2255

Abstract LB-271: The CD44high/ALDHhighcell population mediates tumor initiating cell properties through the sonic Hedgehog pathway in lung cancer

In spite of the decreasing lung cancer incidence recently observed in some countries, its mortality has remained high due to late presentation and limited chemotherapy effectiveness. Even for EGFR mutant cancers initially responding to tyrosine kinase inhibitors (TKI), long term patient survival has not been achieved due to the almost universal occurrence of TKI resistance. Tumor initiating cells (TIC) are a subpopulation of cancer cells believed to be capable of self-renewal leading to tumor perpetuation, metastasis and treatment resistance. To identify self-renewing cells in lung cancer and investigate their regulatory pathways, tumor cells with differential expression of the combined CD44 and ALDH1 markers were isolated by flow cytometry for functional comparison. The results showed in established lung cancer cell lines and early passage clinical lung cancer cells, the CD44high/ALDHhigh population had the strongest, while CD44low/ALDHlow the weakest in-vitro cell sphere formation and in-vivo serial xenograft transplantation capacities. The CD44high/ALDHhigh population also showed higher matrigel invasion ability, pluripotency genes expression, cell cycle regulator expression, as well as resistance to tyrosine kinase inhibitor and/or cisplatin treatment. TKI treatment led to increased CD44high/ALDHhigh cell proportions. Simultaneous down-regulation of CD44 by si-RNA and enzymatic inhibition of ALDH1 suppressed stem/progenitor genes expression including OCT4, SOX2 and NANOG, and attenuated cell sensitivity to TKI and cisplatin treatment in different lung cancer cells, indicating CD44 and ALDH were not only surface markers for TIC, but also had functional roles in TIC maintenance. To investigate for phenotypic differences and potential regulatory pathways involved in the maintenance of the two cell populations, the expression microarray profiles of isolated TIC (CD44high/ALDHhigh) and non-TIC (CD44low/ALDHlow) populations were compared. The results showed differential expression of various cell adhesion molecules, HLA markers, and signaling proteins involved in the Sonic Hedgehog (e.g. GLI1, GLI3) and Notch (e.g. DLL4, JAG1) pathways. Differential expression of selective molecules was independently validated by quantitative RT-PCR in an expanded panel of lung cancer cell lines. Pharmacological inhibition of the Hedgehog pathway using cyclopamine decreased TIC proportion in a dose dependent manner and sensitized lung cancer cells to TKI treatment, while Notch inhibition led to less prominent effects. Taken together, these findings indicated that CD44high/ALDHhigh expression characterized a subpopulation of self-renewing and tumorigenic cells in lung cancer. Therapeutic targeting of the Hedgehog pathway might be useful for disrupting TIC and help to achieve lung cancer control.

Citation Format: Maria Pik Wong, Jing Liu, Zhi-jie Xiao. The CD44high/ALDHhigh cell population mediates tumor initiating cell properties through the sonic Hedgehog pathway in lung cancer. [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 LB-271. doi:10.1158/1538-7445.AM2013-LB-271

Genome-wide association analysis identifies new lung cancer susceptibility loci in never-smoking women in Asia

To identify common genetic variants that contribute to lung cancer susceptibility, we conducted a multistage genome-wide association study of lung cancer in Asian women who never smoked. We scanned 5,510 never-smoking female lung cancer cases and 4,544 controls drawn from 14 studies from mainland China, South Korea, Japan, Singapore, Taiwan and Hong Kong. We genotyped the most promising variants (associated at P < 5 × 10(-6)) in an additional 1,099 cases and 2,913 controls. We identified three new susceptibility loci at 10q25.2 (rs7086803, P = 3.54 × 10(-18)), 6q22.2 (rs9387478, P = 4.14 × 10(-10)) and 6p21.32 (rs2395185, P = 9.51 × 10(-9)). We also confirmed associations reported for loci at 5p15.33 and 3q28 and a recently reported finding at 17q24.3. We observed no evidence of association for lung cancer at 15q25 in never-smoking women in Asia, providing strong evidence that this locus is not associated with lung cancer independent of smoking.

A novel KIF5B-ALK variant in nonsmall cell lung cancer

BACKGROUND

The anaplastic lymphoma kinase (ALK) gene is involved frequently in chromosomal translocations, resulting in fusion genes with different partners found in various lymphoproliferative conditions. It was recently reported in nonsmall cell lung cancer (NSCLC) that the fusion protein encoded by echinoderm microtubule-associated protein-like 4-ALK (EML4-ALK) fusion gene conferred oncogenic properties. The objective of the current study was to identify other possible ALK fusion genes in NSCLC.

METHODS

Immunohistochemical analysis was used to screen for aberrant ALK expression in primary NSCLC. The authors used 5' rapid amplification of complementary DNA ends to screen for potential, novel 5' fusion partners of ALK other than EML4-ALK. Reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization analyses were used to confirm the identity of 5' fusion partners. The genomic breakpoint was verified using genomic sequencing. Overexpression of the novel ALK fusion gene and variants 3a and 3b of EML4-ALK was performed to assess downstream signaling and functional effects.

RESULTS

The authors identified a novel gene resulting from the fusion of kinesin family member 5B (KIF5B) exon 15 to ALK exon 20 in a primary lung adenocarcinoma. Western blot analysis of clinical tumor tissues revealed the expression of a protein whose size correlated with that of the predicted KIF5B-ALK. Overexpression of KIF5B-ALK in mammalian cells led to the activation of signal transducer and activator of transcription 3 and protein kinase B and to enhanced cell proliferation, migration, and invasion.

CONCLUSIONS

The discovery of the novel KIF5B-ALK variant further consolidated the role of aberrant ALK signaling in lung carcinogenesis.

Non-small cell lung cancer cells expressing CD44 are enriched for stem cell-like properties

BACKGROUND

The cancer stem cell theory hypothesizes that cancers are perpetuated by cancer stem cells (CSC) or tumor initiating cells (TIC) possessing self-renewal and other stem cell-like properties while differentiated non-stem/initiating cells have a finite life span. To investigate whether the hypothesis is applicable to lung cancer, identification of lung CSC and demonstration of these capacities is essential.

METHODOLOGY/PRINCIPAL FINDING

The expression profiles of five stem cell markers (CD34, CD44, CD133, BMI1 and OCT4) were screened by flow cytometry in 10 lung cancer cell lines. CD44 was further investigated by testing for in vitro and in vivo tumorigenecity. Formation of spheroid bodies and in vivo tumor initiation ability were demonstrated in CD44(+) cells of 4 cell lines. Serial in vivo tumor transplantability in nude mice was demonstrated using H1299 cell line. The primary xenografts initiated from CD44(+) cells consisted of mixed CD44(+) and CD44(-) cells in similar ratio as the parental H1299 cell line, supporting in vivo differentiation. Semi-quantitative Real-Time PCR (RT-PCR) showed that both freshly sorted CD44(+) and CD44(+) cells derived from CD44(+)-initiated tumors expressed the pluripotency genes OCT4/POU5F1, NANOG, SOX2. These stemness markers were not expressed by CD44(-) cells. Furthermore, freshly sorted CD44(+) cells were more resistant to cisplatin treatment with lower apoptosis levels than CD44(-) cells. Immunohistochemical analysis of 141 resected non-small cell lung cancers showed tumor cell expression of CD44 in 50.4% of tumors while no CD34, and CD133 expression was observed in tumor cells. CD44 expression was associated with squamous cell carcinoma but unexpectedly, a longer survival was observed in CD44-expressing adenocarcinomas.

CONCLUSION/SIGNIFICANCE

Overall, our results demonstrated that stem cell-like properties are enriched in CD44-expressing subpopulations of some lung cancer cell lines. Further investigation is required to clarify the role of CD44 in tumor cell renewal and cancer propagation in the in vivo environment.

Double EGFR mutants containing rare EGFR mutant types show reduced in vitro response to gefitinib compared with common activating missense mutations

Epidermal growth factor receptor (EGFR) mutations are common in lung adenocarcinomas, especially from nonsmoking women of Asian descent. We have previously shown EGFR mutations occur in >70% of lung adenocarcinoma from nonsmokers in our population with a complex mutational profile, including 13% of EGFR double mutations. In this study, we investigated the in vitro gefitinib response of four EGFR double mutants identified in untreated patients, including Q787R+L858R, E709A+G719C, T790M+L858R, and H870R+L858R. The phosphorylation profiles of EGFR and downstream effectors AKT, STAT3/5, and ERK1/2 were compared by immunoblot analyses among the single and double mutants transfected into H358 cells. Results showed that mutants responded to in vitro gefitinib treatment with different sensitivities. The G719C and L858R single mutants showed the highest gefitinib sensitivity compared with the corresponding coexisting single mutants E709A, Q787R, H870R, and T790M. The double mutants E709A+G719C, Q787R+L858R, and H870R+L858R showed attenuated responses to gefitinib in the EGFR and downstream effector phosphorylation profiles compared with G719C or L858R alone. T790M+L858R showed strong resistance to gefitinib. Clinically, the patient whose tumor contained H870R+L858R showed tumor stabilization by 250 mg oral gefitinib daily but cerebral metastasis developed 6 months later. Correlation with the in vitro phosphorylation profile of H870R+L858R suggested that treatment failure was probably due to inadequate suppression of EGFR signaling by the drug level attainable in the cerebrospinal fluid at the given oral dosage. Overall, the findings suggested that rare types of EGFR substitution mutations could confer relative gefitinib resistance when combined with the common activating mutants.

The EML4-ALK fusion gene is involved in various histologic types of lung cancers from nonsmokers with wild-type EGFR and KRAS

BACKGROUND

The echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) fusion gene resulting from the chromosome inversion inv(2)(p21;p23) recently was identified in nonsmall cell lung cancer (NSCLC). The authors of this study investigated the frequency, genetic and clinicopathologic profiles of EML4-ALK in Chinese patients with NSCLC.

METHODS

EML4-ALK was investigated in 266 resected primary NSCLC, including adenocarcinomas (AD), lymphoepithelioma-like carcinomas, squamous cell carcinomas, mucoepidermoid carcinomas, and adenosquamous carcinomas, by reverse transcriptase-polymerase chain reaction and was verified by sequencing. EML4-ALK protein expression was studied by immunohistochemistry.

RESULTS

Thirteen tumors (4.9%) had EML4-ALK comprising 4 fusion transcript variants with fusion of the variable segments from 5' EML4 to 3' ALK and with preservation of the ALK kinase domain. The most common variant consisted of 8 tumors with variant 3 that involved EML4 exon 6. The others included 2 tumors with variant 1 (exon 13), 2 tumors with variant 2 (exon 20), and 1 tumor with the novel variant 5 (exon 18). There were 11 ADs and 2 unusual carcinomas with mixed squamous and glandular components. Immunohistochemistry demonstrated diffuse ALK fusion proteins in the tumor cell cytoplasm. EML4-ALK was associated with nonsmokers (P = .009). Tumors with the fusion gene had the wild-type epidermal growth factor receptor (EGFR) (P = .001) and v-Ki-ras2/Kirsten rat sarcoma viral oncogene homolog (KRAS) genes. Patients who had EML4-ALK-positive AD had a younger median age (P = .018) compared with patients who did not have the fusion gene.

CONCLUSIONS

The EML4-ALK fusion gene was present in various histologic types of NSCLC. It occurred in mutual exclusion to EGFR and KRAS mutations and was associated with nonsmokers. The authors concluded that EML4-ALK may be useful for predicting the potential response to ALK inhibitors as a therapeutic option for patients with lung cancer.

SRC promotes survival and invasion of lung cancers with epidermal growth factor receptor abnormalities and is a potential candidate for molecular-targeted therapy

Molecular-targeted therapy using tyrosine kinase inhibitors against epidermal growth factor receptor (EGFR) is an effective therapy for non-small cell lung cancer that harbor EGFR mutations. This study aimed to investigate the role of Src, a close EGFR associator, as a drug target in NSCLC cells with different EGFR genomic statuses. Src inhibition was achieved using 4-(4'-Phenoxyanilino)-6,7-dimethoxyquinazolinee (SKI-1) and the specificity of action was verified by RNA interference. The results showed that SKI-1 induced significant apoptosis in a dose-dependent manner in cancer cells with high basal Src activation. Activation of FAK and p130Cas was involved in Src-mediated invasion in SKI-1-sensitive cells. SKI-1 inhibited phosphorylation of EGFR as well as EGFR downstream effectors, such as signal transducers and activators of transcription 3/5, extracellular signal-regulated kinase 1/2 and AKT in the mutant cells but not the wild-type cells. This inhibition profile of EGFR implicates that induction of apoptosis and sensitivity of mutant cells to SKI treatment is mediated by EGFR and EGFR downstream pathways. Cotreatment with SKI-1 and gefitinib enhanced apoptosis in cancer cells that contained EGFR mutation and/or amplification. SKI-1 treatment alone induced significant apoptosis in H1975 cells known to be resistant to gefitinib. Src phosphorylation was shown by immunohistochemistry in around 30% of primary lung carcinomas. In 152 adenocarcinomas studied, p-Src was associated with EGFR mutations (P = 0.029). Overall, the findings indicated that Src could be a useful target for treatment of non-small cell lung cancer. Besides EGFR genomic mutations, other forms of EGFR and related family member abnormalities such as EGFR amplification might enhance SKI sensitivity.

Tropism of avian influenza A (H5N1) in the upper and lower respiratory tract

Poor human-to-human transmission of influenza A H5N1 virus has been attributed to the paucity of putative sialic acid alpha2-3 virus receptors in the epithelium of the human upper respiratory tract, and thus to the presumed inability of the virus to replicate efficiently at this site. We now demonstrate that ex vivo cultures of human nasopharyngeal, adenoid and tonsillar tissues can be infected with H5N1 viruses in spite of an apparent lack of these receptors.

Disturbance of systemic antioxidant profile in nonsmall cell lung carcinoma

The present study aimed to determine the alterations of antioxidant activities in erythrocytes from patients with nonsmall cell lung carcinoma (NSCLC). A comparative study of the systemic antioxidant activities in red blood cell lysate from subjects with NSCLC and healthy control subjects was conducted. The antioxidants catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured using chemical kinetic reactions under spectrophotometry. In total, 189 cases of mostly advanced-stage IIIB or stage IV NSCLC and 202 healthy controls were studied. In subjects with lung cancer, there was similar catalase activity, lower SOD activity (median (interquartile range) 13.4 (9.0-27.2) versus 48.7 (27.0-64.3) U x (ghaemoglobulin(Hb)(-1)), and higher GPx activity (175.2 (126.6-288.3) versus 49.2 (39.5-59.2) mU x (gHb)(-1)) compared with controls. The antioxidant activities in lung cancer subjects were not associated with age, sex, smoking status, or tumour cell types. However, more advanced disease (stage IV compared with stage IIIB) was associated with lower SOD activity. Using multivariable analysis, the presence of lung cancer independently predicted SOD and GPx activities. In conclusion, nonsmall cell lung carcinoma in Chinese subjects is associated with alterations in systemic antioxidant activities, which may play an important role in carcinogenesis.

The clinical value of autofluorescence bronchoscopy for the diagnosis of lung cancer

The aim of this study was to evaluate the role of autofluorescence bronchoscopy (AFB) in the routine work-up of lung cancer. Consecutive patients with atypical or suspicious cells in sputum or bronchial aspirate, no localising abnormality on chest radiography and nondiagnostic white-light bronchoscopic (WLB) results were recruited. WLB and AFB were performed sequentially during the same session. All abnormal areas detected by WLB, AFB or both were sampled and the biopsy specimens sent for histological examination. Sixty-two patients were recruited within the 32-month study period. Seventeen had no endobronchial lesion detected. Among the 45 patients with endobronchial lesions, 37 had lesions with a histopathological grade of mild dysplasia or less; of the eight patients who had a lesion with a histological grade of moderate dysplasia or worse, five were found to have lung cancer, two invasive lung cancer and three an intra-epithelial neoplasm (severe dysplasia). Lesions showing moderate dysplasia or worse were more commonly found in patients with suspicious cells than in those with atypical cells on sputum examination. AFB was more sensitive than WLB (91 versus 58%) at detecting these lesions, but less specific (26 versus 50%). A combination of white-light and autofluorescence bronchoscopy can increase the diagnostic yield of this invasive procedure in patients exhibiting abnormal sputum cytology.

High resolution analysis of genomic aberrations by metaphase and array comparative genomic hybridization identifies candidate tumour genes in lung cancer cell lines

Tumours develop from clonally expanded population of cells harbouring aberrations of oncogenes and tumour suppressor genes. In this study, metaphase and array comparative genomic hybridization showed good correlation of aberration profiles in lung adenocarcinoma cell lines from patients with different tobacco exposure. Recurrent DNA gains were found at chromosomes 1, 7, 8, 17, 20, and deletions at 1, 3, 8, 9, 10, 12, 17, 18, 19. Candidate tumour loci and encompassed genes at 7p21 (AGR2), 8q21(TPD52), 20q13 (ZNF217, WFDC2, EEF1A2) and 10p15 (KLF6) were analyzed by dual colour FISH for genomic changes and quantitative PCR for expression changes. Results indicated that EEF1A2 and KLF6 were strong candidates of oncogene and tumour suppressor genes, respectively. This study illustrates, a practical strategy for identifying candidate cancer genes from microarray data.

Frequent allelic loss of 21q11.1∼q21.1 region in advanced stage oral squamous cell carcinoma

A fine mapping of loss of heterozygosity (LOH) was performed in oral squamous cell carcinoma (OSCC), using 12 markers on 21q11.1 approximately q21.1. We studied 43 resected primary invasive tumors and their paired normal tissues, concurrent dysplasia or carcinoma in situ in separate areas from 8 of the specimens, and 6 local recurrent carcinomas. LOH status was compared between lesions of different phases of progression within the same patient. A high frequency of LOH was observed for D21S1410, D21S120, and D21S1433 (60% each) in the primary lesions, constituting two interstitial deleted regions encompassing eight known genes. Cases showing LOH of D21S120 were significantly associated with advanced clinical stages (III and IV; P=0.02). Consistent allelic loss was observed in 64.2% of the informative cases between the precursor lesions and their corresponding invasive tumors, and in 59.5% of those between the primary lesions and their recurrent counterparts. Fewer than half of the different lesions within a given patient showed discordant allelic loss for tested markers. Our results suggest that 21q11.1 approximately q21.1 harbors tumor suppressor genes in OSCC. Genetic divergence may develop during tumor clone evolution.

Lymphoepithelioma-like carcinoma of the lung: experience with ten cases

OBJECTIVE

Lymphoepithelioma-like carcinoma of the lung (LELC) is a rare form of non-small cell lung cancer predominantly affecting young non-smoking Asians, and there has been only limited experience in its palliative chemotherapy and radiotherapy. We investigated tumour response, time to progression and survival of LELC patients who received such treatment.

DESIGN

We prospectively recruited patients with confirmed advanced LELC who were treated with chemoradiotherapy in our unit, a regional tertiary referral centre for lung cancer treatment.

RESULTS

There were 10 patients (five males, age 47 +/- 9.8 years, median follow-up 22 months) with advanced LELC (respectively 1, 4, and 5 patients at TNM stage IIIA, IIIB and IV) who received systemic chemotherapy and radiotherapy. The primary chemotherapy regimen consisted of 5-fluorouracil/leucovorin/cisplatin. The response rates to 5-fluorouracil/leucovorin/cisplatin were 60% partial response, 10% stable disease, and 30% progressive disease. Eight patients were also given local radiotherapy. Five patients received salvage chemotherapy when disease progressed after primary chemotherapy. The overall median survival was 23.4 +/- 4.7 months.

CONCLUSION

The encouraging response to combination chemotherapy with 5-fluorouracil/leucovorin/ cisplatin, although empirical, supports its use with radiotherapy in unresectable lymphoepithelioma-like carcinoma of the lung.

Lymphoepithelioma-like carcinoma of the lung in a patient with silicosis

Silicosis is an important form of pneumoconiosis, which is caused by significant exposure to crystalline silica. The carcinogenicity of silica, despite traditional beliefs, in relation to lung cancer has been controversial. Lymphoepithelioma-like carcinoma of the lung, an Epstein-Barr virus-associated undifferentiated carcinoma, is a rare entity of pulmonary malignancy, which tends to affect young nonsmoking Asians. The first case of silicosis, initially complicated by pulmonary tuberculosis, which later developed into advanced lymphoepithelioma-like carcinoma of the lung is reported. A combination of 5-fluorouracil, cisplatin and calcium folinate resulted in partial tumour response.

Computed tomography characteristics of advanced primary pulmonary lymphoepithelioma-like carcinoma

Our objectives were to document CT features of advanced primary pulmonary lymphoepithelioma-like carcinoma (LELC) and to determine features that may assist differentiation from other non-small cell lung cancers (NSCLC). Imaging and clinical data of all patients with biopsy-proven pulmonary LELC ( n=12) were retrieved from a database of all NSCLC patients over a 2-year period. Twenty-five controls were recruited from other inoperable non-LELC NSCLC patients from the database. Pre-treatment CT scans of the thorax of both study and control patients were reviewed for lobe involved; tumour site, borders and size; and pleural, vascular or pulmonary involvement. Presence of lymphangitis carcinomatosis was noted. Lymph node metastasis was characterised as ipsilateral or contralateral enlarged (>1 cm) mediastinal or hilar nodes, or as peribronchovascular nodal spread. Differences between the two groups were tested using Mann-Whitney rank-sum test. The LELC tumours were significantly larger (45.67 vs 17.71 cm(2)) than controls and were closely associated with the mediastinum. There were more LELC tumours with well-defined borders ( p<0.001) and fewer with spiculated borders ( p<0001) than non-LELC tumours. There was increased peribronchovascular nodal spread ( p=0.01) and vascular encasement ( p=0.02) in LELC compared with non-LELC tumours. Advanced primary pulmonary LELC has distinct radiological features, and can appear as well-defined tumour closely associated with the mediastinum, with peribronchovascular spread and vascular encasement.

Primary adenocarcinomas of the lung in nonsmokers show a distinct pattern of allelic imbalance

Lung cancer development in nonsmokers, particularly in females, has long been observed,but the genetic pathways of oncogenesis are still unclear. The purpose of this study was to identify important targets of chromosomal alteration involved in non-tobacco-related adenocarcinomas of lung. In this study, loci of recurrent allelic imbalance (AI) were identified by microsatellite analysis, focusing on tumors with low frequencies of AI (FAL) relative to the mean level. We reasoned that studying such tumors would facilitate the identification of essential genetic changes needed for the malignant phenotype, which could be masked by genomic instability and widespread nonspecific alterations, especially in tumors showing high FAL. Forty-two adenocarcinomas from nonsmokers (NT-ADs) were analyzed by a broad spectrum of 84 markers covering all nonacrocentric chromosomal arms. Using the mean AI frequency (40%) as the threshold, loci in 7q31, 8p23.2, 10p14-p15, 13q12.3, 16q24, 17p13.1-p13.3, 17q22, 19q13.3, and Xq11.2-q12 showed recurrent AI in the low-FAL tumors, which suggested that essential targets of carcinogenesis may be present. To analyze whether loci, frequently altered in NT-ADs, were uniquely involved in these tumors, 43 loci were also studied in 29 adenocarcinomas from smokers. 2q, 6p, 10p, 13q, 16q, 17q, 19p, 19q, 20p, and 20q showed frequent aberrations in NT-ADs, whereas 1q, 2p, 3p, 3q, 7q, 8p, 9p, 9q, 10q, 11q, 13q, 14q, TP53, 17p, 18q, and 21q were commonly altered in both of the tumor groups. Further comparison of their low-FAL tumors showed that AI involving 16q24, 17q22, and 19q13.3 were significantly associated with NT-ADs; whereas those involving 7q31, 8p23.2, 10p14-p15, 13q12.3, and 17p13.1-p13.3 were observed in both. The findings suggest that oncogenesis in the lung of smokers and nonsmokers involve overlapping yet distinct genetic pathways, whereas the recurrent loci of alteration in NT-ADs may provide a basis for the further mapping of critical molecular targets in these pathways.

Pulmonary cryptococcosis: a case report and review of the Asian-Pacific experience

Pulmonary cryptococcosis is a very rare form of pneumonia, which is seldom seen among immunocompetent patients. We report the case of a 36-year-old man who presented with indolent pneumonia that was subsequently diagnosed to be pulmonary cryptococcosis without other systemic involvement. Contrary to formal belief, there was evidence of residual lung fibrosis 12 months after initial presentation. The features of pulmonary cryptococcosis reported in the Asian Pacific region are also reviewed.

Adenocarcinoma of the lung in Chinese patients: a revisit and some perspectives from the literature

AIM

To establish an updated clinical profile of adenocarcinoma of the lung.

DESIGN

Retrospective review of clinical charts, chest radiography, and computed tomography of consecutive patients who attended Queen Mary Hospital in Hong Kong between June 1995 and December 1997.

RESULTS

In the 115 patients studied, 13% were <40 years of age (33.3% ever smokers). Haemoptysis is more common among patients with early disease, while finger clubbing was detected more commonly among smokers and ex-smokers. Most (98.3%) patients had abnormal chest radiology including presence of mass lesion, pleural effusion, collapse/consolidation, and effusion. Patients with adenocarcinoma were significantly more likely to be younger, female, in advanced disease (stage IIIB and IV), non-smoker, and symptomatic on presentation (p<0.05) than those with squamous cell lung cancer (n=128).

CONCLUSION

The clinical profile of Chinese adenocarcinoma patients should help clinicians in the diagnosis and management of these patients.

Diagnostic yield of bronchoscopic sampling methods in bronchial carcinoma

OBJECTIVES

The aim was to study the yield of malignant or suspicious cells from bronchoalveolar lavage (BAL), endobronchial biopsy (BX) and endobronchial brushing (BR) specimens obtained at bronchoscopy.

METHODOLOGY

We prospectively followed up all patients who had undergone bronchoscopy and studied those with subsequent diagnosis of bronchial carcinoma at a tertiary referral centre. Bronchoalveolar lavage, BX and BR were performed, sequentially whenever possible, by one pulmonologist. The parameters assessed were age, gender, macroscopic bronchoscopic findings, TNM staging, radiological findings, histological typing, and diagnostic yield from BAL, BX, and BR.

RESULTS

One hundred patients (31 females, 69 males; mean age +/- SD, 61.8+/-12.7 years; range 32-81 years) were studied between 1995 and 1997. Of these, BAL, BX and BR were performed on 100, 64 and 37 cases which yielded diagnostic specimens for bronchial carcinoma in 69, 78.1, and 62.2% of cases, respectively (P > 0.05). Diagnostic specimens were therefore obtained in 69,50, and 23% of the entire patient cohort from BAL, BX, and BR, respectively (P < 0.001). The diagnostic yield of BAL was independent of patient age, gender, site of lesion, TNM staging, histological typing and macroscopic bronchoscopic findings. Addition of BX, BR and postbronchoscopic sputum sampling to BAL only increased the yield of diagnostic specimens for bronchial carcinoma by 7, 0, and 4%, respectively.

CONCLUSION

Bronchoalveolar lavage is a highly effective sampling method to obtain cytological evidence for bronchial carcinoma. The diagnostic yield for BAL is independent of tumour or other clinical characteristics. Further studies should be performed to confirm these important and clinically relevant findings.

The angiopoietins, tie2 and vascular endothelial growth factor are differentially expressed in the transformation of normal lung to non-small cell lung carcinomas

The successful establishment of angiogenesis depends on a complex process of endothelial proliferation and organization. The angiopoietins (Ang-1 and Ang-2) and Tie2 ligand-receptor system is essential for the regulation of vascular maturation and stability during embryonic development. Together with the vascular endothelial growth factor (VEGF)-mediated pathway, they have been implicated in the control of normal physiological angiogenesis. We investigated their potential role and interaction in the development of lung cancers by comparing the expression pattern and inter-relationship of Ang-1 and 2, Tie2 and VEGF levels in 28 pairs of primary non-small cell lung cancers (NSCLC) and normal lung. Using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and in-situ hybridization (ISH), we showed that in NSCLC, there was significantly up-regulated VEGF expression by the tumour cells and an increased intensity of Ang-2 expression in the tumour vessels. The number of Ang-2-expressing vessels also correlated with the grades of tumour cell expression of VEGF. On the other hand, normal lung expressed constitutively high and correlated levels of Ang-1 and Tie2, which were significantly reduced in the carcinomas. The findings suggested a role of the Ang-1/Tie2 pathway in the maintenance of the complex vasculature in normal lung, while collaborative activities between the Ang-2 and VEGF pathways might be important in promoting tumour angiogenesis in NSCLC.

Vascular endothelial growth factor is up-regulated in the early pre-malignant stage of colorectal tumour progression

Angiogenesis is an essential requirement for the development, progression and metastasis of malignant tumours. Studies on transgenic mouse models have shown that angiogenesis begins in the pre-malignant phase of oncogenesis, when dysplastic lesions acquire an increased microvasculature. To investigate the relationship between the expression of vascular endothelial growth factor (VEGF) and colorectal tumour progression, we have studied VEGF expression level and splice variant pattern by semi-quantitative RT-PCR and the cellular source of VEGF expression by in situ hybrization (ISH) in a range of lesions that modelled the tumour-development pathway from normal colon to invasive colorectal adenocarcinomas. Colonic adenomas showed a statistically significant up-regulation of VEGF expression over normal tissues, with a further increase during the development of adenocarcinomas. Tumour cells formed the major source of VEGF expression, with a minor contribution from mononuclear cells in the tumour stroma and enhanced expression in tumour cells around necrotic regions. The comparable expression level in both the in situ and invasive components in the same tumours indicated that a high VEGF expression capacity had been acquired prior to establishment of the invasive phenotype. Our findings support activation of VEGF as the molecular basis for the discrete induction of angiogenesis in the pre-malignant phase of colorectal tumour development.

Vascular endothelial growth factor is up-regulated in the early pre-malignant stage of colorectal tumour progression

Angiogenesis is an essential requirement for the development, progression and metastasis of malignant tumours. Studies on transgenic mouse models have shown that angiogenesis begins in the pre-malignant phase of oncogenesis, when dysplastic lesions acquire an increased microvasculature. To investigate the relationship between the expression of vascular endothelial growth factor (VEGF) and colorectal tumour progression, we have studied VEGF expression level and splice variant pattern by semi-quantitative RT-PCR and the cellular source of VEGF expression by in situ hybrization (ISH) in a range of lesions that modelled the tumour-development pathway from normal colon to invasive colorectal adenocarcinomas. Colonic adenomas showed a statistically significant up-regulation of VEGF expression over normal tissues, with a further increase during the development of adenocarcinomas. Tumour cells formed the major source of VEGF expression, with a minor contribution from mononuclear cells in the tumour stroma and enhanced expression in tumour cells around necrotic regions. The comparable expression level in both the in situ and invasive components in the same tumours indicated that a high VEGF expression capacity had been acquired prior to establishment of the invasive phenotype. Our findings support activation of VEGF as the molecular basis for the discrete induction of angiogenesis in the pre-malignant phase of colorectal tumour development.

Supraventricular tachycardia terminated by external mechanical stimulation: a case of "pothole conversion"

Supraventricular tachycardia requires atrial or AV junctional tissue for its initiation and maintenance. Acute management of supraventricular tachycardias include vagal maneuvers, pharmacological treatment, and electrical cardioversion. We describe a case of a supraventricular tachycardias cardioverted by the jolt of the ambulance hitting a pothole. The proposed mechanism of cardioversion is an external mechanical one similar to the precordial thump.