Jaekwang Kim

Melatonin Sensitizes H1975 Non-Small-Cell Lung Cancer Cells Harboring a T790M-Targeted Epidermal Growth Factor Receptor Mutation to the Tyrosine Kinase Inhibitor Gefitinib

Background/Aims: The use of tyrosine kinase inhibitors (TKIs) to target active epidermal growth factor receptor (EGFR)-harbouring mutations has been effective in patients with advanced non-small-cell lung cancer (NSCLC). However, the use of TKIs in NSCLS patients with somatic EGFR mutations, particularly T790M, causes drug resistance. Thus, in the present study, we investigated overcoming resistance against the TKI gefitinib by combination treatment with melatonin in H1975 NSCLC cells harbouring the T790M somatic mutation. Methods: H1975 and HCC827 cells were treated with melatonin in combination with gefitinib, and cell viability, cell cycle progression, apoptosis, and EGFR, AKT, p38, Bcl-2, Bcl-xL, caspase 3 and Bad protein levels were examined. Results: Treatment with melatonin dose-dependently decreased the viability of H1975 cells harbouring the T790M somatic mutation compared to HCC827 cells with an EGFR active mutation. Melatonin-mediated cell death resulted in decreased phosphorylation of EGFR and Akt, leading to attenuated expression of survival proteins, such as Bcl-2, Bcl-xL and survivin, and activated caspase 3 in H1975 cells, but not in HCC827 cells. However, we did not observe a significant change in expression of cell cycle proteins, such as cyclin D, cyclin A, p21 and CDK4 in H1975 cells. Surprisingly, co-treatment of gefitinib with melatonin effectively decreased the viability of H1975 cells, but not HCC827 cells. Moreover, co-treatment of H1975 cells caused consistent down-regulation of EGFR phosphorylation and induced apoptosis compared to treatment with gefitinib or melatonin alone. Conclusions: Our findings demonstrate that melatonin acts as a potent chemotherapeutic agent by sensitising to gefitinib TKI-resistant H1975 cells that harbour a EGFR T790M mutation.

Effect of the Graphene Oxide Reduction Temperature on Supercapacitor Performance

In this study, we investigated the influence of the reduction temperature on graphene oxide. After performing the thermal reduction at specific temperatures (200, 600, and 1000 °C), the morphological and crystallographic changes were investigated by several analysis methods. The reduced graphene oxides were used as supercapacitor electrodes and analyzed with various electrochemical techniques. The capacitance exhibited an increase up to 600 °C before decreasing abruptly at 1000 °C. This behavior was ascribed to the limited ionic accessibility into the compact graphene layer.

Farnesiferol c induces apoptosis via regulation of L11 and c-Myc with combinational potential with anticancer drugs in non-small-cell lung cancers.

Though Farnesiferol c (FC) has been reported to have anti-angiogenic and antitumor activity, the underlying antitumor mechanism of FC still remains unclear. Thus, in the present study, we investigated the apoptotic mechanism of FC in human H1299 and H596 non-small lung cancer cells (NSCLCs). FC significantly showed cytotoxicity, increased sub-G1 accumulation, and attenuated the expression of Bcl-2, Bcl-xL, Survivin and procaspase 3 in H1299 and H596 cells. Furthermore, FC effectively suppressed the mRNA expression of G1 arrest related genes such as Cyclin D1, E2F1 transcription factor and CDC25A by RT-PCR. Interestingly, FC inhibited the expression of c-Myc, ribosomal protein L11 (L11) and nucleolin (NCL) in H1299 and H596 cells. Of note, silencing of L11 by siRNA transfection enhanced the expression of c-Myc through a negative feedback mechanism, while c-Myc knockdown downregulated L11 in H1299 cells. Additionally, combined treatment of FC and puromycin/doxorubicin promoted the activation of caspase 9/3, and attenuated the expression of c-Myc, Cyclin D1 and CDK4 in H1299 cells compared to single treatment. Taken together, our findings suggest that FC induces apoptosis and G1 arrest via regulation of ribosomal protein L11 and c-Myc and also enhances antitumor effect of puromycin or doxorubicin in NSCLCs.

Development of Real-Time Monitoring System for Nuclear Material in Transport

Due to tragic event of Sep. 11, 2001 and experimental evidence of a dirty bomb, a threat using by radioactive or nuclear material is becoming a worldwide problem. To monitor the status and position of in-transit nuclear material in South Korea, real-time monitoring system has been developed and tested. Test results showed that the developed system carried out successfully various functions to track the movement of nuclear material and to notify competent authorities of emergencies for rapid and effective response. In the near future, the radiation detector with wireless communication will be added to this system for the purpose of monitoring the integrity of nuclear material.

Investigation of the Charge-Storage Behavior of Electrochemically Activated Graphene Oxide on Supercapacitor Electrodes in Acidic Electrolyte

AbstractHerein, charge storage behavior of graphene oxide electrode was investigated after its electrochemical activation. X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic chargedischarge method (GCD), and electrochemical impedance spectroscopy (EIS) were employed for this analysis. From XPS analysis, a decrease of atomic ratio of C=C bond was observed after electrochemical activation from 86.94 to 79.64%. Also, enhancement of specific capacitance appeared from 54.1 to 65.7 F g−1 at 20 mV s−1, and rectangular shape in CV became more collapsed in activated grapheme oxide electrode. In the GCD profiles, similarly, difference of resistance values at high and low cut-off potential became larger after activation, indicative of increased polarization. From EIS, detailed resistance components were compared, which reflected that the increased resistance and higher capacitance after activation was probably attributed to larger amount of surface functional groups after activation.