Source efficiency of alpha-emitters applied to the skin surface

Skin surface contamination by alpha-emitters is in itself not hazardous, but it would cause significant internal exposure in the case of injured skin as well as misjudgment in direct in vivo measurements (e.g. lung counting). The present study determined the source efficiency of alpha-emitters (241Am) applied to swine skin samples by analysing the observed alpha-particle energy spectra using advanced alpha-spectrometric simulation. Based on our results, the source efficiency was determined to be 0.365 (alpha-particle s-1 per Bq) on average (c.f. 0.5 in the case of no self-absorption in the source). The decrease in source efficiency would be attributed primarily to the radionuclide entering hair follicles or deep wrinkles. The degradation of the measured spectra from the skin samples indicates the penetration of some radionuclides into the upper layers of the stratum corneum. Although this study was limited to results obtained from swine skin samples, it suggests that irregularities in the skin surface may affect direct alpha measurements.

Inhibition of non-homologous end joining mitigates paclitaxel resistance resulting from mitotic slippage in non-small cell lung cancer

Mitotic slippage, which enables cancer cells to bypass cell death by transitioning from mitosis to the G1 phase without undergoing normal cytokinesis, is one likely mechanism of paclitaxel (PTX) resistance. DNA double-strand breaks (DSBs) in the G1 phase are mainly repaired through non-homologous end joining (NHEJ). Therefore, inhibiting NHEJ could augment the PTX-induced cytotoxicity by impeding the repair of PTX-induced DSBs during the G1 phase following mitotic slippage. We aimed to evaluate the effects of NHEJ inhibition on mitotic slippage after PTX treatment in non-small cell lung cancer (NSCLC). H1299, A549, H1975, and H520 NSCLC cell lines were employed. In addition, A-196 and JQ1 were used as NHEJ inhibitors. H1299 cells were PTX-resistant and exhibited an increased frequency of mitotic slippage upon PTX treatment. NHEJ inhibitors significantly augmented the PTX-induced cytotoxicity, DSBs, and apoptosis in H1299 cells. The newly generated PTX-resistant cells were even more prone to mitotic slippage following PTX treatment and susceptible to the combined therapy. Docetaxel further demonstrated synergistic effects with the NHEJ inhibitor in PTX-resistant cells. NHEJ inhibition may overcome intrinsic or acquired PTX resistance resulting from mitotic slippage by synergistically increasing the cytotoxic effects of antimitotic drugs in NSCLC.

Endobronchial ultrasound with a guide sheath during bronchoscopy for peripheral pulmonary lesions

INTRODUCTION

Radial probe endobronchial ultrasound (rEBUS) improves the diagnostic yield of peripheral pulmonary lesions (PPLs). A notable methodological limitation of rEBUS is that it does not provide real-time images during transbronchial biopsy (TBB) procedures. To overcome this limitation, a guide sheath (GS) method was developed.

AREAS COVERED

This review covers the procedures and complications of rEBUS-guided TBB with a GS (EGS method). We also present the data from key randomized controlled trials (RCTs) of the EGS method and summarize the usefulness of combining the EGS method with various techniques. Finally, we discuss in which situations EGS should be used.

EXPERT OPINION

A large RCT showed that the diagnostic yield of the EGS method for PPLs was significantly higher than that of rEBUS-guided TBB without a GS (non-GS method). However, since the EGS and non-GS methods each have their own advantages and disadvantages, they should be considered complementary and used flexibly in different cases. In some cases, a combination of the two may be an option. The appropriate combination of EGS with various techniques may enhance the diagnostic yield of PPLs and help prevent complications. The choice should be based on the location and texture of the target lesion, as well as operator skill, resource availability, safety, and accuracy.

EGFR inhibition in EGFR ‐mutant lung cancer cells perturbs innate immune signaling pathways in the tumor microenvironment

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) elicit potent cell cycle arrest in EGFR-mutant non-small-cell lung cancer (NSCLC) cells. However, little is known about the mechanisms through which these drugs alter the tumor phenotype that contributes to the immune escape of EGFR-mutant cells. Using EGFR-mutant NSCLC cell lines and tissue samples from patients, we investigated the changes in immune checkpoints expressed in tumor cells following EGFR inhibition. Subsequently, we also analyzed the role of soluble factors from the dying tumor cells in the activation of immune signaling pathways involved in therapy resistance. Upon EGFR-TKI treatment, we found that EGFR-mutant cells upregulated the expression of innate immune checkpoint CD24 in vitro. We then analyzed biopsy samples from six patients who developed resistance to a first-generation EGFR-TKI without the acquired T790M mutation. Immunohistochemistry revealed that levels of tumor CD24 expression were increased upon treatment compared with those from pre-treatment samples. Monocyte-derived macrophages facilitated antibody-dependent cellular phagocytosis when EGFR-TKI-treated EGFR-mutant cells were incubated with anti-CD24 antibodies in vitro, suggesting that CD24 may be a therapeutical target for EGFR-mutant lung cancer. Moreover, EGFR inhibition accelerated the release of cell-free DNA (cfDNA) from dying tumor cells, which activated the type I interferon signaling pathways in human THP-1 monocytes in a stimulator of interferon genes-dependent manner. Our study indicates that EGFR inhibition in EGFR-mutant NSCLC cells fosters a tumor microenvironment associated with immune escape. Thus, CD24 targeted therapy and cfDNA monitoring may contribute to improved treatment outcomes in patients with EGFR-mutant NSCLC.

Risk of bleeding associated with transbronchial biopsy using flexible bronchoscopy in patients with echocardiographic or chest CT evidence of pulmonary hypertension

Background

Endobronchial ultrasound (EBUS)-guided transbronchial biopsy (TBB) facilitates the diagnosis of various respiratory diseases. The safety of performing EBUS-guided TBB in patients with a finding of pulmonary hypertension (PH) is controversial. Little is known about the relationship between the risk of bleeding associated with EBUS-guided TBB in the presence of PH suspected on echocardiography or chest CT.

Methods

To assess the risk of bleeding associated with EBUS-guided TBB in patients with presumed PH per echocardiography or chest CT, we retrospectively reviewed the medical records of 314 consecutive patients who underwent EBUS-guided TBB using a guide sheath (GS), as well as echocardiography and chest CT. Bleeding complication was defined as over one minute of suctioning; repeated wedging of the bronchoscope; instillation of cold saline, diluted vasoactive substances, or thrombin due to persistent bleeding. Findings of suspected PH were defined as peak tricuspid regurgitation velocity (TRV) > 2.8 m/s on echocardiography or pulmonary artery to aorta ratio (PA:A ratio) > 0.9 on chest CT.

Results

In total, 35 (11.1%) patients developed bleeding, and all cases were managed safely. Furthermore, 17 (5.4%) and 59 (18.8%) patients were suspected to have PH based on echocardiography and chest CT, respectively. Among the patients suspected to have PH on echocardiography, five (5/17 = 29.4%) patients developed bleeding. Among the patients suspected to have PH on chest CT, 11 (11/59 = 18.6%) patients developed bleeding. Univariate analysis revealed that long diameter (≥ 30 mm) of the lesion, lesion location (the biopsy site was inner than the segmental bronchus), bronchoscopic diagnosis of malignancy, and additional biopsy were potential predictive factors for bleeding. The finding of suspected PH on echocardiography correlated significantly with bleeding (p = 0.03). On multivariate analysis, long diameter (≥ 30 mm) of the lesion (p = .021) and findings of suspected PH on echocardiography (p = .049) were significantly associated with bleeding.

Conclusion

All cases of bleeding in the present study were managed safely. The risk of bleeding is moderately elevated when PH is suspected by echocardiography in patients undergoing EBUS-guided TBB using a GS.

Double-pulsed wave packets in spontaneous radiation from a tandem undulator

We verify that each wave packet of spontaneous radiation from two undulators placed in series has a double-pulsed temporal profile with pulse spacing which can be controlled at the attosecond level. Using a Mach–Zehnder interferometer operating at ultraviolet wavelengths, we obtain the autocorrelation trace for the spontaneous radiation from the tandem undulator. The results clearly show that the wave packet has a double-pulsed structure, consisting of a pair of 10-cycle oscillations with a variable separation. We also report the characterization of the time delay between the double-pulsed components in different wavelength regimes. The excellent agreement between the independent measurements confirms that a tandem undulator can be used to produce double-pulsed wave packets at arbitrary wavelength.

Clinical Significance of Tumor Markers for Advanced Thymic Carcinoma: A Retrospective Analysis from the NEJ023 Study

Simple Summary

Advanced thymic carcinoma (ATC) is rare. Owing to its rarity, there is limited information on the prognostic factors, and the optimal serum tumor markers are also unknown. We conducted a multi-institutional retrospective study of patients with ATC. In this study, we collected data on patient characteristics, progression-free survival (PFS), overall survival (OS), and tumor marker values, and investigated the relationship between tumor marker values and PFS/OS. We found that the neuron-specific enolase (NSE) level may be a useful prognostic tumor marker for ATC, regardless of histology. The findings of the analysis limited to squamous cell carcinoma suggested that the NSE and squamous cell carcinoma antigen levels may be useful prognostic factors.

Abstract

The optimal tumor marker for predicting the prognosis of advanced thymic carcinoma (ATC) remains unclear. We conducted a multi-institutional retrospective study of patients with ATC. A total of 286 patients were treated with chemotherapy. Clinicopathological information, including serum tumor markers, was evaluated to determine the overall survival (OS) and progression-free survival (PFS). The carcinoembryonic antigen, cytokeratin-19 fragment, squamous cell carcinoma (SCC) antigen, progastrin-releasing peptide, neuron-specific enolase (NSE), and alpha-fetoprotein levels were evaluated. In the Kaplan–Meier analysis, the OS was significantly shorter in the patients with elevated NSE levels than in those with normal NSE levels (median, 20.3 vs. 36.8 months; log-rank test p = 0.029; hazard ratio (HR), 1.55; 95% confidence interval (CI), 1.05–2.31 (Cox proportional hazard model)); a similar tendency regarding the PFS was observed (median, 6.4 vs. 11.0 months; log-rank test p = 0.001; HR, 2.04; 95% CI, 1.31–3.18). No significant differences in the OS and PFS were observed among the other tumor markers. In both univariate and multivariate analyses of the patients with SCC only, the NSE level was associated with the OS and PFS. Thus, the NSE level may be a prognostic tumor marker for thymic carcinoma, regardless of histology.

A phase I/II study of osimertinib in EGFR exon 20 insertion mutation-positive non-small cell lung cancer

OBJECTIVES

Several preclinical data proposed a potential efficacy of osimertinib, a third-generation EGFR tyrosine kinase inhibitor, for EGFR exon 20 insertion (EGFR ex20ins)-positive non-small cell lung cancer (NSCLC). However, reported case series and a retrospective study proposed controversial efficacy. The efficacy of osimertinib in EGFR ex20ins-positive NSCLC have not been well evaluated in prospective clinical trials. In this study, we performed a prospective, single-arm, multi-center, open-label, non-randomized phase I/II study to evaluate efficacy of osimertinib for EGFR ex20ins-positive NSCLC.

MATERIALS AND METHODS

From August 2018 to January 2020, 14 NSCLC patients with EGFR ex20ins were enrolled, of whom 2 were excluded because they did not meet the inclusion criteria. Efficacy and safety of 80 mg osimertinib were evaluated. In addition, we performed a translational exploratory study to clarify the association of mutation type-specific drug sensitivity, osimertinib pharmacokinetic data, and clinical efficacy.

RESULTS

Of the evaluated patients, none experienced objective response, 7 experienced stable disease (58.3%), and 5 experienced disease progression (41.7%). The median progression free survival (PFS) was 3.8 months, and the median overall survival was 15.8 months. Interestingly, the exploratory study demonstrated statistically significant positive correlation between plasma osimertinib concentration/in vitro IC₅₀ ratio and PFS (R = 0.9912, P = 0.0001), highlighting the mutation type-specific concentration-dependent efficacy of osimertinib for EGFR ex20ins-positive NSCLC.

CONCLUSIONS

Regular dose, 80 mg/day, of osimertinib has limited clinical activity in NSCLC patients with EGFR ex20ins. The translational study proposed the potential efficacy of higher dose osimertinib in a subgroup of EGFR ex20ins-positive NSCLC.

Abstract CT106: Phase I/II study of osimertinib in EGFR exon 20 insertion mutations in non-small cell lung cancer patients: AEX20

Background EGFR exon 20 insertion gene mutation (ex20ins) accounts for about 4-12% of the total EGFR gene mutations in non-small cell lung cancer (NSCLC) patients. NSCLC patients with EGFR ex20ins is known to be less sensitive to 1st- or 2nd-generation EGFR-TKIs. Although 3rd-generation EGFR-TKI, osimertinib is active against in vitro models of EGFR ex20ins, its efficacy has not yet been fully elucidated. This phase I/II study is conducted to evaluate the clinical efficacy of osimertinib in NSCLC patients with EGFR ex20ins. Method This is a single-arm, multi-center, open-label, non-randomized phase I/II study (UMIN000031929) consisting of stage 1 and stage 2 (Simon's two-stage design). In stage 1, 12 patients receive osimertinib 80mg once daily until they meet the termination criteria, such as, disease progression, severe toxicities, withdrawal etc. In stage 2, 9 patients receive the same dose of osimertinib if more than 1 patient achieve PR or CR in stage 1. At the transition from stage 1 to 2, Independent Data Monitoring Committee (IDMC) will provide recommendation regarding the need for study continuation, termination or dose modification of osimertinib. Patients with advanced or metastatic NSCLC with EGFR ex20ins who have a history of chemotherapy within 0 to 3 regimens are enrolled. Patients with history of EGFR-TKI treatment (gefitinib, erlotinib, afatinib, dacomitinib) can be included if the EGFR-TKI treatment did not show any clinical benefit. Patients with EGFR gene mutations, such as exon 19 deletion, L858R, T790M, G719X, L861Q are excluded. Primary end point is objective response rate (ORR) assessed via Response Evaluation Criteria in Solid Tumors version 1.1. Secondary end points are progression-free survival, overall survival, and safety profiles. Blood sampling is obtained at 4-weeks after starting osimertinib to analyze pharmacokinetic parameters. We also perform liquid biopsy for next generation sequencing at before and after acquiring resistance to osimertinib to clarify resistant mechanisms of osimertinib in EGFR ex20ins. We explore the relationship among clinical outcome, side effect, pharmacokinetic parameters and subtype of EGFR ex20ins. Result Recruitment began in June 2018 and by February 2020, 12 patients were enrolled in stage 1 at 6 institutions. Backgrounds of the patients were as follows, the median age was 63 years (range 22-84), female/male 6/6, ECOG PS 0/1 8/4, cStage IIIA/IIIb/IVA/IVB 1/1/2/8. The ORR was 0% (CR/PR 0, SD 8, PD 4), and the DCR was 66.7%. From the result of stage 1, one of the IDMC's recommendations was protocol revision since it is presumed that increasing the dose of osimertinib could be clinically promising. At the conference, the influence of subtype of EGFR ex20ins and blood levels of osimertinib on survival will be evaluated and the results of interim analysis for stage 1 will be presented. Conclusion Regular dose of osimertinib has limited clinical activity in NSCLC patients with EGFR ex20ins. Funding AstraZeneca.

Citation Format: Eiki Ichihara, Hiroyuki Yasuda, Yuta Takashima, Yoshitaka Zenke, Shinji Takeuchi, Masahiro Morise, Katsuyuki Hotta, Mineyoshi Sato, Shingo Matsumoto, Azusa Tanimoto, Reiko Matsuzawa, Katsuyuki Kiura, Hideki Terai, Shinnosuke Ikemura, Koichi Goto, Kenzo Soejima. Phase I/II study of osimertinib in EGFR exon 20 insertion mutations in non-small cell lung cancer patients: AEX20 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT106.

Usefulness of lead delivery catheter system for true right ventricular septal pacing

Background

Right ventricular (RV) septal pacing is often selected to preserve a more physiologic ventricular activation. But the pacing leads are not always located in true septal wall, rather in hinge or free wall in some cases with the conventional stylet-guided lead implantation. In recent years, new guiding catheter systems has attracted attention as a solution to that problem.

Objective

The aim of this study is to investigate that true ventricular sepal pacing can be achieved by use of the new guiding catheter system for pacing lead.

Methods

We enrolled 198 patients who underwent RV septal lead implantation and computed tomography (CT) after pacemaker implantation. 16 cases were used delivery catheter (Delivery), and 182 cases were used stylet for targeting ventricular septum (Conventional). We analyzed the lead locations with CT, and evaluated capture thresholds, R-wave amplitudes, lead impedances and 12-lead electrocardiogram findings one month after implantation.

Results

All cases of delivery catheter group had true septal lead positions (Delivery; 100% vs Conventional; 44%, p<0.01). Capture thresholds and lead impedances had not significant differences between between two groups (0.65±0.15V vs 0.60±0.15V, p=0.21, 570±95Ω vs 595±107Ω, p=0.39, respectively). R-wave amplitudes were significantly higher in delivery catheter group (13.0±4.8mV vs 10±4.6mV, p<0.01). Paced QRS durations were shorter in delivery catheter group (128±16ms vs 150±21ms, p<0.01).

Conclusions

The delivery catheter system designated for pacing lead can contribute to select the true ventricular septal sites and to attain the more physiologic ventricular activation.

Funding Acknowledgement

Type of funding source: None

AB0089 THE ANALYSIS FOR THE INHIBITION OF ANGIOGENESIS BY JAK INHIBITOR

Background:

Many blood vessels are generated in the hyperplastic synovial tissue of patients with rheumatoid arthritis (RA), and lead to chronic tissue inflammation and joint destruction [1]. Janus kinase (JAK) family consisting of JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2) are chain receptors which phosphorylate signal transducers and activators of transcription (STAT) and mediate inflammatory diseases including RA [2]. Nowadays, several JAK inhibitors such as Tofacitinib (TOF), Baricitinib (BAR) and Peficitinib (PEF) have been developed and demonstrated to have the inhibitory effects on inflammatory arthritis [3-5]. However, there were few reports concerning their effects on angiogenesis in vitro.

Objectives:

The purpose of the present study is to investigate the influence of JAK inhibitors on angiogenesis of human umbilical vein endothelial cell (HUVEC) activated by vascular endothelial growth factor (VEGF).

Methods:

The cell line of HUVECs were used for this study. The activity of proliferation and tube formation were analyzed by counting assay and tube formation assay, respectively.

In counting assay, HUVECs (5 × 104cells/ml) were seeded onto 96-well cell culture plate with 20 ng/ml VEGF including various doses (0.1µM, 1µM, 5µM) of TOF, BAR or PEF. After 48 hours incubation at 37°C in a humidified atmosphere containing 5% CO2, cell proliferation of each groups was assessed using cell counting kit. In tube formation assay, HUVECs (5 × 104cells/ml) were treated with 20ng/ml VEGF including various dose (0.1µM, 1µM, 5µM) of TOF, BAR or PEF for 00 hours, then seeded onto 48-well plate applied with Matrigel. After 24 hours incubation on Matrigel, the capillary-like tube formation of each well was photographed using phase contrast microscopy. Tube formation were quantitated by measurement of the length of branch.

Results:

HUVECs were activated in proliferation and tube formation by VEGF treatment. And, the proliferation and tube formation of HUVECs activated by VEGF were suppressed by All of TOF, BAR and PEF. In particular, TOF and PEF could suppress them highly.

Conclusion:

This study showed the inhibitory effect of JAK inhibitors on proliferation and tube formation of HUVECs activated by VEGF. In particular, the angiogenesis of HUVECs activated by VEGF was highly suppressed by TOF and PEF. VEGF is reported to regulate the angiogenesis through multi JAK-STAT signaling pathways [6]. The inhibitory effects on angiogenesis of TOF, BAR and PEF might depend on the differences in their affinity for JAKs. VEGF has been shown to a have a central involvement in the angiogenic process in RA [7]. JAK inhibitors might suppress the angiogenesis in RA synovial tissues by inhibiting VEGF signaling.

References:

[1]Scott DL, et al. Rheumatoid arthritis. Lancet. 2010.

[2]Banerjee S, et al. JAK-STAT signaling as a target for inflammatory and autoimmune diseases: current and future prospects. Drugs. 2017.

[3]William D, et al. JAK inhibitors in dermatology: the promise of a new drug class. Journal of the American Academy of Dermatology. 2017.

[4]Dhillon S. Tofacitinib: A Review in Rheumatoid Arthritis. Drugs. 2017.

[5]Markham A, et al. Peficitinib: First Global Approval. Drugs. 2019.

[6]Zhang HY, et al. Three important components in the regeneration of the cavernous nerve: brain-derived neurotrophic factor, vascular endothelial growth factor and the JAK/STAT signaling pathway. Asian journal of andrology. 2011.

[7]Paleolog EM. Angiogenesis in rheumatoid arthritis. Arthritis research. 2002.

Acknowledgments:

none

Disclosure of Interests:

None declared

SAT0019 HISTOPATHOLOGICAL CHANGES OF SYNOVIAL TISSUE IN RHEUMATOID ARTHRITIS PATIENTS TREATED WITH TNF INHIBITORS

Background:

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by hyperplasia of synovial tissues [1]. Tumor necrosis factor (TNF)-α is one of the pro-inflammatory cytokines that play a crucial role in the pathogenesis of RA synovitis, and TNF inhibitors (TNFi) were reported to force the RA to go into remission or low disease activity and have brought revolutionary impacts on RA treatment [2]. TNFi have been shown to act on inflammatory cells and form the discoid fibrosis in the sublining layers [3,4]. However, the changes of synovial tissue and the cause of discoid fibrosis in RA patients treated with TNFi has not been determined in detail.

Objectives:

The purpose of this study is to demonstrate the histological changes and the types of cells around discoid fibrosis in RA synovium treated with TNFi.

Methods:

Synovial tissues were obtained from 30 patients with RA during joint surgeries. 6 patients were treated with TNFi (1 patient with golimumab, 3 patients with etanercept, 2 patients with infliximab). As a control, synovial tissues were obtained from 6 patients who were treated only with csDMARDs (6 patients with MTX). The frozen sections were stained by hematoxylin and eosin (HE). To detect the apoptosis, TdT-mediated dUTP nick end labeling (TUNEL) was performed. The immunohistochemical characterization of the synovial cells was performed by using following antibodies: CD20 and CD3 for detecting B and T lymphocytes respectively, CD163 and CD86 for detecting M1 and M2 macrophage respectively.

Results:

In the sections stained with HE, the formation of discoid fibrosis and the other characteristic changes including hydropic degeneration, vacuolation, sclerosis of small vasculature, and the number of multilayered synovial cells was decreased in synovium from RA patients treated with TNFi. In the sections with TUNEL stain, apoptosis of lining cells around the discoid fibrosis was detected in RA synovium treated with TNFi (Figure 1a, 1b). In the sections with immunohistochemistry stain, CD86 expression increased in lining layer of RA synovium treated with TNFi. CD163 positive cells showed diffuse expression in RA synovium treated with TNFi. In contrast, CD20 and CD3 positive cells decreased around discoid fibrosis compared to control sections. These results showed indicated that the types of cells in lining and sublining layers were mainly macrophages and that the apoptosis of macrophages might form the discoid fibrosis in lining layers.

Conclusion:

This study showed the apoptosis of lining cells derived from macrophages resulted in the formation of the discoid fibrosis. These findings indicated TNFi might induce apoptosis of macrophage leading to the suppression of RA synovitis.

References:

[1] Scott Dl, et al. Progression of radiological changes in rheumatoid arthritis. Ann Rheum Dis. 1984.

[2]van der Heijde D,et al. Comparison of etanercept and methotrexate, alone and combined, in the treatment of rheumatoid arthritis: two-year clinical and radiographic results from the TEMPO study, a double-blind, randomized trial. Arthritis Rheum. 2006.

[3] Hirohata S,et al. TNF inhibitors induce discoid fibrosis in the sublining layers of the synovium with degeneration of synoviocytes in rheumatoid arthritis. Rheumatol Int. 2013.

[4] Yamanaka H,et al. Scoring evaluation for histopathological features of synovium in patients with rheumatoid arthritis during anti-tumor necrosis factor therapy. Rheumatol Int. 2010.

Acknowledgments :

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Disclosure of Interests:

None declared

DLL3 regulates the migration and invasion of small cell lung cancer by modulating Snail

Delta‐like protein 3 (DLL3) is a ligand of Notch signaling, which mediates cell‐fate decisions and is tumor‐suppressive or oncogenic depending on the cellular context. Previous studies show that DLL3 is highly expressed in small cell lung cancer (SCLC) but not in normal lung tissue, suggesting that DLL3 might be associated with neuroendocrine tumorigenesis. However, its role in SCLC remains unclear. To investigate the role of DLL3 in tumorigenesis in SCLC, we performed loss‐of‐function and gain‐of‐function assays using SCLC cell lines. In vitro analysis of cell migration and invasion by transwell assay showed that DLL3 knockdown reduced migration and invasion of SCLC cells, whereas DLL3 overexpression increased these activities. In addition, DLL3 positively regulated SNAI1 expression and knockdown of SNAI1 attenuated the migration and invasion ability of SCLC cells. Moreover, upregulated DLL3 expression induced subcutaneous tumor growth in mouse models. These results indicate that DLL3 promoted tumor growth, migration and invasion in an SCLC model by modulating SNAI1/Snail.

Abstract 332: The BET bromodomain inhibitor JQ1 synergizes with WEE1 inhibitor AZD1775 by impairing non-homologous end joining and enhancing DNA damages in non-small cell lung cancer

Background: The bromodomain and extraterminal domain (BET) inhibitors are broadly active in different cancer types, including non-small cell lung cancer (NSCLC). Although their activity on oncogene expression such as c-Myc has been addressed in many studies, the mechanism of BET inhibition on the cytotoxicity remain unknown. BET proteins have been also reported to interact with some DNA damage repair-related genes. AZD1775, a selective WEE1 G2 checkpoint kinase inhibitor, induces DNA damage and consequent apoptosis by abrogating G2 cell cycle arrest and inducing premature mitotic entry. We hypothesized that repression of BET activity would increase WEE1 inhibitor-induced cytotoxicity by impairing DNA damage repair. Here, we evaluate the efficacy and mechanistic rationale for combining AZD1775 and JQ1 as a potential therapy for NSCLC.

Methods: NSCLC cell lines (A549, H1299, H1975) and human embryonic kidney cells line (293T) were used in the present study. Anti-tumor activities of JQ1, AZD1775, or the combination were analyzed using MTT survival assay. Changes in protein expression were analyzed by Western Blot analysis. mRNA expressions were evaluated by quantitative rt-PCR. Cell cycle was analyzed by flow cytometry using PI staining. Activity of non-homologous end joining (NHEJ) was evaluated using NHEJ reporter plasmid.

Results: The combination of AZD1775 and JQ1 showed synergistic effects for NSCLC cell lines in vitro with combination indices of 0.1-0.5. The JQ1 monotherapy did not induce gamma-H2AX expression, but JQ1 increased and prolonged AZD1775-induced gamma-H2AX expression. The mRNA analysis showed that JQ1 significantly repressed NHEJ-related genes, such as XRCC4 and LIG4. Moreover, NHEJ reporter assay revealed JQ1 diminished NHEJ activity.

Conclusions: Our data demonstrate that the combination of JQ1 and AZD1775 has a synergistic effect against NSCLC cell lines via a mechanism of compromised DNA damage repair by JQ1. This combination therapy can be a novel therapeutic strategy for NSCLC.

Citation Format: Yuta Takashima, Eiki Kikuchi, Junko Kikuchi, Tetsuaki Shoji, Megumi Furuta, Hajime Kikuchi, Jun Sakakibara-Konishi, Ichiro Kinoshita, Hirotoshi Dosaka-Akita, Masaharu Nishimura. The BET bromodomain inhibitor JQ1 synergizes with WEE1 inhibitor AZD1775 by impairing non-homologous end joining and enhancing DNA damages in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 332.

Abstract 3158: DLL3 regulates migration and invasion of small cell lung cancer

Background: Delta-like protein 3 (DLL3) is a ligand of Notch signaling, which is reported to be a tumor suppressor in small cell lung cancer (SCLC). Previous studies suggest that DLL3 might be associated with neuroendocrine tumorigenesis through inhibition of Notch signaling unlike other activating ligands. Moreover, DLL3 was highly expressed in SCLC, but not in normal lung tissue. However, little is known about function of DLL3 in SCLC. In this study, we examine the effect of DLL3 in tumorigenesis of SCLC.

Methods: The mRNA expression levels and proteins of DLL3, Notch receptors (Notch1, Notch2, Notch3 and Notch4), Hes1 and EMT markers (E-cadherin, Snail and Vimentin) were examined using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot in 9 SCLC cell lines (SBC-3, SBC-5, MS-1, RERF-LC-MA, H69, H82, H209, H529 and H1688). We used small interfering RNA (siRNA) to down-regulate the expression of DLL3 in SCLC cell lines. Anchorage-dependent and anchorage-independent cell growth was measured by MTT assay and migration and invasion were assessed by transwell assay.

Results: The mRNA of DLL3 was expressed in all of 9 SCLC cell lines. The expression of DLL3 was especially higher in H82, H69, H209, H529 and H1688 cells. Notch1 protein was expressed in SBC-3, SBC-5, MS-1 and H82. Based on DLL3 expression analysis data, we used H82 and H69 in the following experiments. The suppression of DLL3 by siRNA resulted in the moderate inhibition of cell growth of H82 cells in both anchorage-dependent and anchorage-independent cell proliferation. The depletion of DLL3 prevented migration and invasion in the two cell lines. The expressions of Notch1 and Notch target gene, Hes1 were downregulated by DLL3 knockdown in both SCLC cells. Because Notch pathway was reported to regulate EMT, we evaluated the EMT markers when DLL3 was inhibited in SCLC cells. Snail was downregulated in DLL3 knockdown SCLC cells, while protein expression levels of E-cadherin and Vimentin were not changed in these DLL3 knockdown cells compared to control cells.

Conclusions: DLL3 promotes the migration and invasion in SCLC cells by modulating Notch1 and Snail.

Citation Format: Megumi Furuta, Jun Konishi Sakakibara, Tetsuaki Shoji, Yuta Takashima, Hajime Kikuchi, Eiki Kikuchi, Junko Kikuchi, Ichiro Kinoshita, Hirotoshi Dosaka Akita, Masaharu Nishimura. DLL3 regulates migration and invasion of small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3158.

Abstract 3927: Clinicopathologic features and immune microenvironment of non-small cell lung cancer with primary resistance to epidermal growth factor receptor-tyrosine kinase inhibitors

Background: Approximately 20-30% of non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) activating mutations are not responsive to EGFR-tyrosine kinase inhibitors (TKIs). Although, primary resistance to EGFR-TKI is attributed to various genetic alterations, little is known about the clinical and immunopathological features of patients with primary resistance. The tumor immune microenvironment including tumor infiltrating lymphocytes (TILs) and programmed death ligand 1 (PD-L1) has been reported to play an important role in tumor progression in NSCLC. However, few studies have directly focused on the relationship between the tumor immune microenvironment and primary resistance to EGFR-TKI.

Materials and Methods: Characteristics of 124 NSCLC patients with EGFR mutations who received EGFR-TKI were analyzed. Primary resistance was defined as disease progression within 3 months after EGFR-TKI treatment. Tumor specimens obtained before EGFR-TKI treatment were assessed for the density of TILs expressing CD4 or CD8, and for the expression rate of PD-L1 on tumor cells and tumor-infiltrating immune cells, immunohistochemically.

Results: Primary resistance was observed in 13.7% (17/124) of patients. Smoking Tobacco correlated significantly with primary resistance compared to non-primary resistance. Lower density of total TILs and negative PD-L1 expression as per immunohistochemical analysis correlated significantly with primary resistance. Moreover, immune ignorant phenotype of tumor microenvironment, negative PD-L1 expression with low TIL density, was significantly observed in primary resistance.

Conclusions: Smoking and immune ignorance in the tumor microenvironment might result in primary resistance to EGFR-TKIs.

Citation Format: Yuta Takashima, Jun Sakakibara-Konishi, Yutaka Hatanaka, Kanako C. Hatanaka, Yoshihito Ohhara, Satoshi Oizumi, Yasuhiro Hida, Kichizo Kaga, Ichiro Kinoshita, Hirotoshi Dosaka-Akita, Yoshihiro Matsuno, Masaharu Nishimura. Clinicopathologic features and immune microenvironment of non-small cell lung cancer with primary resistance to epidermal growth factor receptor-tyrosine kinase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3927.

Successful Application of Edoxaban in the Treatment of Venous Thromboembolism Recurrence in a Patient with Non-small Cell Lung Cancer after Tumor Shrinkage

This report describes the case of a 66-year-old man with non-small cell lung cancer and venous thromboembolism (VTE). Unfractionated heparin (UFH) was initially used to control VTE before chemotherapy. However, switching UFH to warfarin or edoxaban, a novel oral anticoagulant (NOAC), failed. Chemotherapy was then administered to control the tumor which was thought to have been the main cause of VTE, which had been treated by UFH. After tumor shrinkage was achieved by chemotherapy, we were able to successfully switch from UFH to edoxaban. Controlling the tumor size and activity enabled the use of edoxaban as maintenance therapy for VTE.

Prognostic Factors and Efficacy of First-Line Chemotherapy in Patients with Advanced Thymic Carcinoma: A Retrospective Analysis of 286 Patients from NEJ023 Study

BACKGROUND

The prognostic factors and the efficacy of first-line chemotherapy remain unclear in patients with advanced thymic carcinoma.

MATERIALS AND METHODS

We conducted a multi-institutional retrospective study named NEJ023 for patients with advanced thymic carcinoma. All patients without any indication of curative treatment were treated with chemotherapy from 1995 to 2014 at 40 institutions of the North East Japan Study Group.

RESULTS

A total of 286 patients with advanced thymic carcinoma were analyzed. First-line chemotherapy included platinum-based doublets in 62.2% of the patients, monotherapy in 3.5%, and other multidrug chemotherapy (e.g., cisplatin, doxorubicin, vincristine, and cyclophosphamide [ADOC]) in 34.3%. The median follow-up period was 55.5 months, and the median overall survival (OS) from the start of first-line chemotherapy was 30.7 months (95% confidence interval, 25.9-35.9 months). There was no significant difference in OS among different first-line chemotherapy regimens (e.g., between carboplatin/paclitaxel and ADOC, median OS: 27.8 vs. 29.9 months). Masaoka-Koga stage IVa and volume reduction surgery were favorable prognostic factors for OS in the multivariate analysis using the Cox proportional hazards model.

CONCLUSION

The efficacy of each first-line chemotherapy regimen for advanced thymic carcinoma did not vary significantly. Our results might support the adequacy of the use of carboplatin/paclitaxel as first-line chemotherapy for these patients.

IMPLICATIONS FOR PRACTICE

Because of its rarity, there is limited information about prognostic factors and efficacy of chemotherapy in patients with advanced thymic carcinoma. This is the largest data set for those patients treated with chemotherapy. This study suggests there is no significant difference in efficacy between carboplatin/paclitaxel and cisplatin/doxorubicin/vincristine/cyclophosphamide for advanced thymic carcinoma. This result can support the adequacy of the selection of platinum doublets as treatment for those patients, rather than anthracycline-based multidrug regimen.

Angular Momentum of Twisted Radiation from an Electron in Spiral Motion

We theoretically demonstrate for the first time that a single free electron in circular or spiral motion emits twisted photons carrying well-defined orbital angular momentum along the axis of the electron circulation, in adding to spin angular momentum. We show that, when the electron velocity is relativistic, the radiation field contains harmonic components and the photons of lth harmonic carry lℏ total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and are more ubiquitous in laboratories and in nature than ever thought.

A specific Streptococcus mutans strain aggravates non-alcoholic fatty liver disease

OBJECTIVE

Streptococcus mutans, a major dental caries pathogen, has shown to be associated with the aggravation of cerebral hemorrhage and inflammatory bowel diseases. In this study, we evaluated the effects ofS. mutans on the development of non-alcoholic steatohepatitis (NASH) in a mouse model.

MATERIALS AND METHODS

Streptococcus mutans oral strain MT8148 (serotype c) and a blood isolate TW871 (k) were used. C57BL/6J mice (6 weeks old)were fed a high-fat diet for 4 weeks; the test strains or phosphate-buffered saline was then intravenously administered. Mice were euthanized after 8 or 12 weeks. Whole body, extirpated liver, and visceral fat weights were determined, and histopathological evaluations of the liver specimens were performed.

RESULTS

Mice infected with TW871 showed significantly greater body and liver weights than those administered MT8148 or phosphate-buffered saline. Histopathological analyses revealed prominent infiltration of inflammatory cells and adipocellular deposition in livers extirpated 8 weeks after an infection with TW871; fibrosis was also observed in livers extirpated after 12 weeks.

CONCLUSION

These results suggest that a specific strain of S. mutans could induce NASH.

Contribution of glucan-binding protein A to firm and stable biofilm formation by Streptococcus mutans

Glucan-binding proteins (Gbps) of Streptococcus mutans, a major pathogen of dental caries, mediate the binding of glucans synthesized from sucrose by the action of glucosyltransferases (GTFs) encoded by gtfB, gtfC, and gtfD. Several stress proteins, including DnaK and GroEL encoded by dnaK and groEL, are related to environmental stress tolerance. The contribution of Gbp expression to biofilm formation was analyzed by focusing on the expression levels of genes encoding GTFs and stress proteins. Biofilm-forming assays were performed using GbpA-, GbpB-, and GbpC-deficient mutant strains and the parental strain MT8148. The expression levels of gtfB, gtfC, gtfD, dnaK, and groEL were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Furthermore, the structure of biofilms formed by these Gbp-deficient mutant strains was observed using confocal laser scanning microscopy (CLSM). Biofilm-forming assay findings demonstrated that the amount formed by the GbpA-deficient mutant strain (AD1) was nearly the same as that by the parental strain, while the GbpB- and GbpC-deficient mutant strains produced lower amounts than MT8148. Furthermore, RT-qPCR assay results showed that the expressions of gtfB, dnaK, and groEL in AD1 were elevated compared with MT8148. CLSM also revealed that the structure of biofilm formed by AD1 was prominently different compared with that formed by the parental strain. These results suggest that a defect in GbpA influences the expression of genes controlling biofilm formation, indicating its importance as a protein for firm and stable biofilm formation.

Microbunching instability in relativistic electron bunches: direct observations of the microstructures using ultrafast YBCO detectors

Relativistic electron bunches circulating in accelerators are subjected to a dynamical instability leading to microstructures at millimeter to centimeter scale. Although this is a well-known fact, direct experimental observations of the structures, or the field that they emit, remained up to now an open problem. Here, we report the direct, shot-by-shot, time-resolved recording of the shapes (including envelope and carrier) of the pulses of coherent synchrotron radiation that are emitted, and that are a "signature" of the electron bunch microstructure. The experiments are performed on the UVSOR-III storage ring, using electrical field sensitive YBa2Cu3O(7-x) thin-film ultrafast detectors. The observed patterns are subjected to permanent drifts, that can be explained from a reasoning in phase space, using macroparticle simulations.

Topical drug delivery to retinal pigment epithelium with microfluidizer produced small liposomes

Drug delivery from topically instilled eye drops to the posterior segment of the eye has long been one of the greatest challenges of ocular drug development. We developed methods of liposome preparation utilizing a microfluidizer to achieve adjustable nanoparticle size (even less than 80 nm) and high loading capacity of plasmid DNA. The microfluidizing process parameters were shown to affect the size of the liposomes. Higher operating pressures and passage for at least 10 times through the microfluidizer produced small liposomes with narrow size distribution. The liposomes were physically stable for several months at +4°C. In vivo distribution of the optimized liposome formulations in the rat eyes was investigated with confocal microscopy of the histological specimens. Transferrin was used as a targeting ligand directed to retinal pigment epithelium. Size dependent distribution of liposomes to different posterior segment tissues was seen. Liposomes with the diameter less than 80 nm permeated to the retinal pigment epithelium whereas liposomes with the diameter of 100 nm or more were distributed to the choroidal endothelium. Active targeting was shown to be necessary for liposome retention to the target tissue. In conclusion, these microfluidizer produced small liposomes in eye drops are an attractive option for drug delivery to the posterior segment tissues of the eye.

Diversities and similarities in pH dependency among bacterial NhaB-like Na+/H+ antiporters

NhaB-like antiporters were the second described class of Na(+)/H(+) antiporters, identified in bacteria more than 20 years ago. While nhaB-like gene sequences have been found in a number of bacterial genomes, only a few of the NhaB-like antiporters have been functionally characterized to date. Although earlier studies have identified a few pH-sensitive and -insensitive NhaB-like antiporters, the mechanisms that determine their pH responses still remain elusive. In this study, we sought to investigate the diversities and similarities among bacterial NhaB-like antiporters, with particular emphasis on their pH responsiveness. Our phylogenetic analysis of NhaB-like antiporters, combined with pH profile analyses of activities for representative members of several phylogenetic groups, demonstrated that NhaB-like antiporters could be classified into three distinct types according to the degree of their pH dependencies. Interestingly, pH-insensitive NhaB-like antiporters were only found in a limited proportion of enterobacterial species, which constitute a subcluster that appears to have diverged relatively recently among enterobacterial NhaB-like antiporters. Furthermore, kinetic property analyses of NhaB-like antiporters at different pH values revealed that the degree of pH sensitivity of antiport activities was strongly correlated with the magnitude of pH-dependent change in apparent Km values, suggesting that the dramatic pH sensitivities observed for several NhaB-like antiporters might be mainly due to the significant increases of apparent Km at lower pH. These results strongly suggested the possibility that the loss of pH sensitivity of NhaB-like antiporters had occurred relatively recently, probably via accumulation of the mutations that impair pH-dependent change of Km in the course of molecular evolution.

Inhibitory effects of Oenothera biennis (evening primrose) seed extract on Streptococcus mutans and S. mutans-induced dental caries in rats

BACKGROUND

Oenothera biennis (evening primrose) seed extract (OBSE) is known to contain polyphenols, which may possess antioxidant activities. Polyphenols extracted from several plants are reported to exhibit cariostatic activities by inhibiting mutans streptococcus growth and glucosyltransferase activities. The purpose of the present study was to examine the inhibitory effects of OBSE on the development of dental caries, both in vitro and in vivo.

METHODS

OBSE was investigated for its inhibitory effects on cellular aggregation, hydrophobicity, sucrose-dependent adherence and insoluble glucan synthesis. Furthermore, biofilm formation was examined in the presence of OBSE, using confocal microscopic imaging. An animal experiment was also performed to examine the in vivo effects.

RESULTS

OBSE induced a strong aggregation of Streptococcus mutans MT8148 cells, while cell surface hydrophobicity was decreased by approximately 90% at a concentration of 0.25 mg/ml. The sucrose-dependent adherence of the MT8148 cells was also reduced by addition of OBSE, with a reduction rate of 73% seen at a concentration of 1.00 mg/ml. Additionally, confocal microscopic observations revealed the biofilm development phase to be remarkably changed in the presence of OBSE. Furthermore, insoluble glucan synthesis was significantly reduced when OBSE was present at concentrations greater than 0.03 mg/ml. In an animal experiment, the caries scores in rats given OBSE (0.05 mg/ml in drinking water) were significantly lower than those in rats given water without OBSE.

CONCLUSION

Our results indicate that OBSE has inhibitory activity on dental caries.

The development of peripheral cold neural circuits based on TRPM8 expression

Afferent nerve fibers of the somatosensory system are a molecularly diverse cell population that detects a varied range of environmental stimuli, converting these external cues ultimately into a sensory percept. Afferents mediating detection of thermal stimuli express a repertoire of temperature sensitive ion channels of the TRP family which endow these nerves with the ability to respond to the breadth of temperatures in the environment. The cold and menthol receptor TRPM8 is responsible for detection of cold and, unlike other thermosensors, detects both innocuous and noxious temperatures. How this single molecule can perform such diverse functions is currently unknown, but expression analyses in adult tissues shows that TRPM8 neurons are a molecularly diverse population and it is likely that this diversity underlies differential functionality. To determine how this phenotype is established, we examined the developmental time course of TRPM8 expression using a mouse transgenic line in which GFP expression is driven by the TRPM8 transcriptional promoter (Trpm8(GFP)). We find that Trpm8(GFP) expression begins prior to embryonic day 15.5 (E15.5) after which expression reaches levels observed in adult neurons. By E18.5, central axons of Trpm8(GFP) neurons reach the spinal cord dorsal horn, but anatomical localization and in vivo measurements of neural activity suggest that fully functional cold circuits are not established until after the first postnatal week. Additionally, Trpm8(GFP) neurons undergo a transition in neurochemical phenotype, ultimately reaching adult expression of markers such TRPV1, CGRP, peripherin, and NF200 by postnatal day 14. Thus, based on immunochemical, anatomical and functional criteria, active cold neural circuits are fully established by the second week postnatal, thereby suggesting that important extrinsic or intrinsic mechanisms are active prior to this developmental stage.

Transverse-longitudinal coupling effect in laser bunch slicing

We report turn-by-turn observation of coherent synchrotron radiation (CSR) produced by the laser bunch slicing technique at an electron storage ring operated with a small momentum compaction factor. CSR emission was intermittent, and its interval depended strongly on the betatron tune. This peculiar behavior of the CSR could be interpreted as a result of coupling between the transverse and longitudinal motion of the electrons. This is the first observation of such an effect, which would be important not only for controlling the CSR emission but also for generating and transporting ultrashort electron bunches or electron bunches with microdensity structures in advanced accelerators.

Extremely low frequency magnetic fields and the promotion of H2O2‐induced cell death in HL‐60 cells

PURPOSE

To test whether exposure to an extremely low frequency magnetic field (60 Hz, 5 mT) affects hydrogen peroxide (H2O2)-induced cell death in human leukaemia HL-60 cells.

MATERIALS AND METHODS

Cells were treated with H2O2 with or without exposure to an extremely low frequency magnetic fields. Viable cells, apoptotic and necrotic cells were determined by annexin V flow cytometry assay. The levels of apoptosis-related proteins (caspase-3, caspase-7, Bcl-2 and Bax) and poly(ADP-ribose) polymerase were detected using Western blotting.

RESULTS

Simultaneous treatment with exposure to the magnetic field and H2O2 (85 or 100 microM) for 24 h increased the number of apoptotic and necrotic cells significantly, and significantly decreased the number of viable cells compared with cells treated with H2O2 alone. The protein levels of Bax and Bcl-2 showed no differences between H2O2-treated cells and those treated with both H2O2 and an extremely low frequency magnetic field. Exposure to the magnetic field also had no effect on H2O2-induced caspase-3 activation. However, the protein levels of active caspase-7 in cells simultaneously exposed to an extremely low frequency magnetic field and H2O2 for 2 and 8 h was higher than that of H2O2 treatment alone. In addition, simultaneous exposure to an extremely low frequency magnetic field and H2O2 caused poly(ADP-ribose) polymerase cleavage and induced early inactivation at 2 h, while H2O2 treatment alone did not produce this effect until 4 h.

CONCLUSIONS

The data suggest that although the magnetic field itself cannot induce apoptosis and necrosis, it exerts a promoting effect on H2O2-induced cell death, and it demonstrates that caspase-7 as well as poly(ADP-ribose) polymerase might be involved in this process.

Inhibition of UV‐induced G1 arrest by exposure to 50 Hz magnetic fields in repair‐proficient and ‐deficient yeast strains

PURPOSE

To assess the possibility that extremely low frequency (ELF) magnetic fields obstruct the damage repair process, the gene conversion frequency and cell cycle kinetics in a DNA repair-proficient and nucleotide excision repair (NER)-deficient strain of diploid yeast Saccharomyces cerevisiae.

MATERIALS AND METHODS

DNA repair- or NER-deficient cells were irradiated with sublethal doses of ultraviolet light (UV) radiation followed by exposure to 50 Hz magnetic fields up to 30 mT for 48 h. After exposure, colony-forming ability was scored as revertants in which gene conversion had restored the functional allele of the ARG4 gene conversion hotspot. Cell cycle analysis was performed using flow cytometry.

RESULTS

Gene conversion rate was increased by the combined exposure in DNA repair-proficient cells, whereas it remained unchanged between UV alone and the combined exposure in NER-deficient cells. The UV-induced G1 arrest was inhibited by exposure to 30 mT ELF magnetic fields in both repair-proficient and -deficient cells.

CONCLUSIONS

The results suggest that exposure to high-density (30 mT) ELF magnetic fields decreases the efficiency of NER by suppressing G1 arrest, which in turn led to enhancement of the UV-induced gene conversion.