Radiosensitivity Of Lung Cancer Cells Research Articles

MicroRNA-449a Enhances Radiosensitivity in CL1-0 Lung Adenocarcinoma Cells

Lung cancer is the leading cause of cancer-related mortality worldwide. Radiotherapy is often applied for treating lung cancer, but it often fails because of the relative non-susceptibility of lung cancer cells to radiation. MicroRNAs (miRNAs) have been reported to modulate the radiosensitivity of lung cancer cells and have the potential to improve the efficacy of radiotherapy. The purpose of this study was to identify a miRNA that can adjust radiosensitivity in lung adenocarcinoma cells. Two lung adenocarcinoma cell lines (CL1-0 and CL1-5) with different metastatic ability and radiosensitivity were used. In order to understand the regulatory mechanisms of differential radiosensitivity in these isogenic tumor cells, both CL1-0 and CL1-5 were treated with 10 Gy radiation, and were harvested respectively at 0, 1, 4, and 24 h after radiation exposure. The changes in expression of miRNA upon irradiation were examined using Illumina Human microRNA BeadChips. Twenty-six miRNAs were identified as having differential expression post-irradiation in CL1-0 or CL1-5 cells. Among these miRNAs, miR-449a, which was down-regulated in CL1-0 cells at 24 h after irradiation, was chosen for further investigation. Overexpression of miR-449a in CL1-0 cells effectively increased irradiation-induced DNA damage and apoptosis, altered the cell cycle distribution and eventually led to sensitization of CL1-0 to irradiation.

Abstract 4166: MicroRNA-449a enhances radiosensitivity in lung adenocarcinoma cells.

Abstract Lung cancer is the leading cause of cancer-related mortality worldwide. Radiotherapy is often applied for treating lung cancer, but it often fails because of the relative non-susceptibility of lung cancer cells to radiation. MicroRNAs (miRNAs) have been reported to modulate the radiosensitivity of lung cancer cells and have the potential to improve the efficacy of radiotherapy. The purpose of this study was to identify a miRNA that can adjust radiosensitivity in lung adenocarcinoma cells. Two lung adenocarcinoma cell lines (CL1-0 and CL1-5) with different metastatic ability and radiosensitivity were used. In order to understand the regulatory mechanisms of differential radiosensitivity in these isogenic tumor cells, both CL1-0 and CL1-5 were treated with 10 Gy radiation, and were harvested respectively at 0, 1, 4, and 24 h after radiation exposure. The changes in expression of miRNA upon irradiation were examined using Illumina Human microRNA BeadChips. Twenty-five miRNAs were identified as having differential expression post-irradiation in CL1-0 or CL1-5 cells. Among these miRNAs, miR-449a, which was down-regulated in CL1-0 cells at 24 h after irradiation, was chosen for further investigation. Overexpression of miR-449a in CL1-0 cells effectively increased irradiation-induced DNA damage and apoptosis, altered the cell cycle distribution and eventually led to sensitization of CL1-0 to irradiation. Citation Format: Yi-Jyun Liu, Yu-Fen Lin, Yi-Fan Chen, En-Ching Luo, Yuh-Ping Sher, Mong-Hsun Tsai, Eric Y. Chuang, Liang-Chuan Lai. MicroRNA-449a enhances radiosensitivity in lung adenocarcinoma cells. [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 4166. doi:10.1158/1538-7445.AM2013-4166

Enhanced radiosensitivity of NSCLC cells by transducer of erbB2.1 (TOB1) through modulation of the MAPK/ERK pathway

Transducer of erbB2.1 (TOB1) is a member of the B-cell translocation gene (BTG)/transducer of erbB2 (TOB) anti‑proliferative protein family. Previous studies have demonstrated that overexpression of TOB1 significantly enhances the radiosensitivity of breast and cervical cancer cells. However, the potential mechanisms of TOB1 are still debated. In the present study, we evaluated the effects of infrared (IR) radiation on TOB1 expression in the human lung cancer cell lines NCI-H1975 and A549 via western blot analysis. NCI-H1975 cells were transfected with TOB1 recombinant plasmid, and A549 cells were treated with TOB1-small interfering RNA(siRNA) to establish gain-of-function and loss-of‑function cell models. The effects of radiation and TOB1 overexpression and silencing on clonogenic survival, cell cycle distribution and DNA repair were assessed. Western blot analysis was performed to determine the related mechanisms. The expression levels of TOB1 were significantly induced by IR radiation. Overexpression of TOB1 abrogated radiation-induced G2/M arrest, reduced clonogenic cell survival and enhanced γ-H2AX foci in NCI-H1975 cells exposed to irradiation. TOB1-siRNA demonstrated opposite effects in A549 cells. TOB1 regulated the activation of mitogen-activated protein kinase (MAPK) and modulated the phosphorylation of p53 via activation of the MAPK/extracellular signal-regulated kinase (ERK) pathway. The findings suggest that TOB1 may be a novel molecular target of irradiation. TOB1 modulated the radiosensitivity of lung cancer cells via the MAPK/ERK signaling pathway.

The Tumor Suppressor, p53, Contributes to Radiosensitivity of Lung Cancer Cells by Regulating Autophagy and Apoptosis

Cell death is one of the most important endpoints of radiosensitivity. The tumor suppressor p53 participates not only in regulation of apoptosis, but also in autophagy mechanism. In this study, H1299-P53 (with wild-type p53) and H1299-175H (with mutant 175H) were used, and the effects of p53 on radiosensitivity were analyzed. Cell models with different p53 status were established by gene engineering, and cell viability was examined by colony formation assay, and cell counting kit-8 (CCK-8), 3-Methyladenine, and Z-VAD were used to block autophagy and apoptosis, respectively. Western blot was used to detect protein expression; monodansylcadaverine (MDC) staining was used to analyze autophagy rate; DAPI/Propidium Iodide (PI) staining and flow cytometry were used to assess apoptosis and necrosis. In parental H1299, H1299-P53, and H1299-175H cells, radiosensitivity exhibited different by colony formation and CCK-8 assay (D0: 1.764 Gy, 1.407 Gy and 1.695 Gy; Dq: 2.977 Gy, 1.199 Gy and 2.312 Gy in turn). The radiosensitization of p53 was associated with the increase of MDM2 and P21 expression. The ionizing radiation (IR)-induced apoptosis was significant in H1299-P53 compared with in H1299 and H199-175H (p < 0.05) by flow cytometry, and the expression of cleaved-caspase3 was increased in H1299-P53 cells. While the IR-induced autophagy was significant in H1299 cells (p < 0.01) and decreased in H1299-P53 and H1299-175H cells (p < 0.01) by MDC staining, the expression of MAPLC3II and Beclin-1 increased in H1299, but not in H1299-p53 and H199-175H cells. The IR-induced cell survival was significantly increased by Z-VAD-FMK and decreased by 3MA in H1299-P53 cells; IR- induced autophagy was significantly increased by Z-VAD-FMK in H1299-P53 cells (p < 0.01), but not changed in H1299 cells. p53 could regulate radiosensitivity by inhibiting autophagy and activating apoptosis; autophagy provides a prosurvival mechanism, and p53 potently abrogated the IR-induced autophagy, while mutant 175H shown no effect on radiosensitivity, suggesting that individual treatment strategies should be based on p53 status in patients.

EGFR-dependent impact of indol-3-carbinol on radiosensitivity of lung cancer cells

背景与目的吲哚-3-甲醇（indole-3-carbinol, I3C）是十字花科蔬菜中一种主要的有效植物化学物质，且具有防癌和抗癌作用。本研究旨在观察I3C是否影响表皮生长因子受体（epidermal growth factor receptor, EGFR）表达水平不同的肺癌细胞放射敏感性。方法采用MTT和克隆形成实验方法分别检测肺癌细胞的生长和存活率；siRNA转染方法降低细胞中EGFR蛋白表达水平；Western blot和RT-PCR法分别测定EGFR蛋白和mRNA的表达。结果采用无明显毒副作用的5 μmol/L剂量的I3C预处理明显降低了EGFR表达阳性的人肺腺癌H1975和人肺鳞癌H226细胞对γ-射线照射的放射敏感性，而I3C对EGFR表达阴性的人肺鳞癌NIH-H520细胞的放射敏感性则影响非常小。Western blot结果显示I3C可以增加H1975和H226细胞中EGFR蛋白的表达水平和Y845位点磷酸化水平。EGFR siRNA降低了NIH-H1975细胞中EGFR蛋白的表达，增加了细胞的放射敏感性，并有效地降低和抑制了I3C导致的细胞耐辐射效应。结论我们的研究结果首次证实I3C可以通过调节EGFR表达和磷酸化水平从而影响肺癌细胞的放射治疗敏感性，提示EGFR可能是I3C影响肺癌放射治疗敏感性的重要靶蛋白。

Inhibition of JAK2 Signaling by TG101209 Enhances Radiotherapy in Lung Cancer Models

Persistent STAT3 activation contributes to lung carcinogenesis. Survivin, one of STAT3-regulated genes, is antiapoptotic and confers cancer radioresistance. We tested whether TG101209, a small-molecule inhibitor of JAK2 (a STAT3-activating tyrosine kinase), affected survivin expression and sensitized lung cancer to radiation. We investigated whether inhibition of JAK2 signaling with TG101209 can be used to reduce survivin expression and enhance radiosensitivity of lung cancer cells in vitro and tumor growth delay in vivo. JAK2 downstream signaling, including PI3-K/Akt and Ras/MAPK/ERK pathways, was also explored. TG101209 inhibited STAT3 activation and survivin expression and sensitized HCC2429 (dose enhancement ratio = 1.34, p = 0.002) and H460 (dose enhancement ratio = 1.09, p = 0.006) cells to radiation in clonogenic assays. Radiation promoted phospho-Akt and phospho-ERK in H460 cells, while their levels were unchanged in HCC2429. After treatment with TG101209, phospho-ERK protein levels were reduced in both HCC2429 and H460 cells. HCC2429 cells transfected with KRAS-12V mutant were more resistant to radiation- and TG101209-induced apoptosis than wild-type control cells. In vivo, addition of TG101209 to radiation in lung xenografts produced a significant tumor growth delay (>10 days) compared with radiation alone and was well tolerated. Immunohistochemistry staining of tumor sections showed that TG101209 increased apoptosis and decreased cell proliferation and vascular density, suggesting that TG101209 also has antiangiogenic effects. TG101209 enhanced the effects of radiation in lung cancer in vitro and in vivo. This study suggests the potential utility of selecting lung cancer patients according to KRAS mutation status for future clinical trials testing combination of TG101209 and radiotherapy.

Lovastatin Sensitizes Lung Cancer Cells to Ionizing Radiation: Modulation of Molecular Pathways of Radioresistance and Tumor Suppression

In this study, we investigated the effect of the 3-hydroxy-3-methylgutaryl-CoA reductase inhibitor lovastatin, as a sensitizer of lung cancer cells to ionizing radiation (IR). A549 lung adenocarcinoma cells were treated with 0 to 50 μM lovastatin alone or in combination with 0 to 8 Gy IR and subjected to clonogenic survival and proliferation assays. To assess the mechanism of drug action, we examined the effects of lovastatin and IR on the epidermal growth factor (EGF) receptor and AMP-activated kinase (AMPK) pathways and on apoptotic markers and the cell cycle. Lovastatin inhibited basal clonogenic survival and proliferation of A549 cells and sensitized them to IR. This was reversed by mevalonate, the product of 3-hydroxy-3-methylgutaryl-CoA reductase. Lovastatin attenuated selectively EGF-induced phosphorylation of EGF receptor and Akt, and IR-induced Akt phosphorylation, in a mevalonate-sensitive fashion, without inhibition on extracellular signal-regulated kinase 1/2 phosphorylation by either stimulus. IR phosphorylated and activated the metabolic sensor and tumor suppressor AMPK, but lovastatin enhanced basal and IR-induced AMPK phosphorylation. The drug inhibited IR-induced expression of p53 and the cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1), but caused a redistribution of cells from G1-S phase (control and radiated cells) and G2-M phase (radiated cells) of cell cycle into apoptosis. The latter was also evident by induction of nuclear fragmentation and cleavage of caspase 3 by lovastatin in both control and radiated cells. We suggest that lovastatin inhibits survival and induces radiosensitization of lung cancer cells through induction of apoptosis, which may be mediated by a simultaneous inhibition of the Akt and activation of the AMPK signaling pathways.

Abstract B7: Genome-wide analysis of CpG methylation for the radiosensitivity

Abstract Epigenetic regulation is one of the most important mechanisms for the development and the progression of human cancers. To understand the epigenetic control of differential sensitivity to radiotherapy, we investigated the DNA CpG methylation profiles of normal lung epithelial cells and lung cancer cell lines using DNA microarray. Among 27K CpG probes in Illumina BeadChip, we found CpG sites of 1091 genes were differentially methylated in radiosensitive H460 and radioresistant H1299 cell lines against normal lung cells. Among the hypermethylated genes in H1299 cells, promoter CpG methylation and mRNA expression of SERPINB5 and S100A6 were validated by methylation-specific PCR and quantitative RT-PCR, respectively. When we suppressed the expression of these two genes using siRNA in H460 cells, the survival fraction of H460 cells were increased upon ionizing radiation. Promoter CpG sites of CAT and BNC1 were hypomethylated in radioresistant H1299 cells and the introduction of siRNA against CAT or BNC1 in H1299 cells could reduce the resistance to ionizing radiation. Here we report the differentially methylated genes by genome-wide CpG methylation profiling in two lung cancer cell lines, which might prove the epigenetic regulation of radiosensitivity in lung cancer cells. Citation Information: Clin Cancer Res 2010;16(14 Suppl):B7.

Global analysis of CpG methylation reveals epigenetic control of the radiosensitivity in lung cancer cell lines

Epigenetic regulation by CpG methylation has an important role in tumorigenesis as well as in the response to cancer therapy. To analyze the mechanism of epigenetic control of radiosensitivity, the CpG methylation profiles of radiosensitive H460 and radioresistant H1299 human non-small cell lung cancer (NSCLC) cell lines were analyzed using microarray profiling. These analyses revealed 1091 differentially methylated genes (DMG) (absolute difference of mean beta-values, |Deltabeta |>0.5), including genes involved in cell adhesion, cell communication, signal transduction and transcriptional regulation. Among the 747 genes hypermethylated in radioresistant H1299 cells, CpG methylation of SERPINB5 and S100A6 in radioresistant H1299 cells was confirmed by methylation-specific PCR. Reverse transcriptase-PCR showed higher expression of these two genes in radiosensitive H460 cells compared with radioresistant H1299 cells. Downregulation of SERPINB5 or S100A6 by small interfering RNA in H460 cells increased the resistance of these cells to ionizing radiation. In contrast, promoter CpG sites of 344 genes, including CAT and BNC1, were hypomethylated in radioresistant H1299 cells. Suppression of CAT or BNC1 mRNA expression in H1299 cells also reduced the resistance of these cells to ionizing radiation. Thus, we identified DMGs by genome-wide CpG methylation profiling in two NSCLC cell lines with different responses to ionizing radiation, and our data indicated that these differences may be critical for epigenetic regulation of radiosensitivity in lung cancer cells.

Dietary Curcumin Increases Antioxidant Defenses in Lung, Ameliorates Radiation-Induced Pulmonary Fibrosis, and Improves Survival in Mice

The effectiveness of lung radiotherapy is limited by radiation tolerance of normal tissues and by the intrinsic radiosensitivity of lung cancer cells. The chemopreventive agent curcumin has known antioxidant and tumor cell radiosensitizing properties. Its usefulness in preventing radiation-induced pneumonopathy has not been tested previously. We evaluated dietary curcumin in radiation-induced pneumonopathy and lung tumor regression in a murine model. Mice were given 1% or 5% (w/w) dietary curcumin or control diet prior to irradiation and for the duration of the experiment. Lungs were evaluated at 3 weeks after irradiation for acute lung injury and inflammation by evaluating bronchoalveolar lavage (BAL) fluid content for proteins, neutrophils and at 4 months for pulmonary fibrosis. In a separate series of experiments, an orthotopic model of lung cancer using intravenously injected Lewis lung carcinoma (LLC) cells was used to exclude possible tumor radioprotection by dietary curcumin. In vitro, curcumin boosted antioxidant defenses by increasing heme oxygenase 1 (HO-1) levels in primary lung endothelial and fibroblast cells and blocked radiation-induced generation of reactive oxygen species (ROS). Dietary curcumin significantly increased HO-1 in lungs as early as after 1 week of feeding, coinciding with a steady-state level of curcumin in plasma. Although both 1% and 5% w/w dietary curcumin exerted physiological changes in lung tissues by significantly decreasing LPS-induced TNF-alpha production in lungs, only 5% dietary curcumin significantly improved survival of mice after irradiation and decreased radiation-induced lung fibrosis. Importantly, dietary curcumin did not protect LLC pulmonary metastases from radiation killing. Thus dietary curcumin ameliorates radiation-induced pulmonary fibrosis and increases mouse survival while not impairing tumor cell killing by radiation.

Abstract 5549: p53-independent radiosensitization of lung cancer cells by inhibition of mTOR pathway

Abstract A high extent of activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and mutations in the p53 gene are involved in lung cancer therapeutic resistance. The mammalian target of rapamycin (mTOR) acts as a downstream effector for Akt and activation of the Akt/mTOR signal is a contributing factor to decreased radiation sensitivity. The aim of this study was to examine whether the effect of rapamycin on radiation sensitivity is affected by cellular p53 gene status in two human non-small cell lung cancer (NSCLC) cell lines with the same genetic background except for their p53 gene status (H1299/wtp53 and H1299/mp53). Cellular radiation sensitivity was evaluated with colony formation assays and apoptosis assays, using Hoechst33342 staining. Rapamycin synergistically enhanced the cytotoxicity of radiation regardless of p53 gene status, and promoted the induction of apoptosis. Moreover, the combined treatment augmented the cytostatic effects of radiation independently of cellular p53 gene status. In agreement with this result, cell cycle analysis by flow cytometry showed increased G1 arrest and suppression of progression to S phase in both cell lines. Western blotting revealed a prominent p53-independent down-regulation of the mTOR signal and pro-survival molecule, cyclin D1 after the combined treatment, suggesting that rapamycin can enhance the effect of radiation through the repression of pro-survival signals and the reduction in the apoptotic threshold. This study indicates that inhibition of the mTOR signal may be a promising strategy for radiosensitization with no relevance to p53 gene status from two aspects of cell lethality and cell growth depression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5549.

Correlation of initial DNA damage detected by alkaline comet assay and clinical endpoints in lung cancer patients

Cells derived from lung cancer are biological heterogeneous and have different intrinsic radiosensitivity, it is a key question for us to investigate radiosensitive parameters for an individualized radiotherapy plan. The comet assay is a sensitive and facilitated method to detect single-cell DNA damage and repair, and the results from it have been proven to be so highly coincident with those from clonogenic assay by cell-line investigations that it has been considered as a promising method in predicting radiosensitivity. The study is designed to evaluate preliminarily the correlation between initial DNA damage detected by alkaline comet assay and the clinical endpoints. Biopsy samples from 31 lung cancer patients by fibrous bronchial endoscopy were detected by alkaline comet assay from April, 2002 to November, 2002. The adjusted tail moment (R TM) was measured and thoracic local-region lesions were measured by computer tomography scan. Response rate (RR) and time to progression (TTP) for the local-region lesions were as clinical endpoints. SPSS 10.0 software was used to compare median R TM of different RR and TTP groups by Mann-Whitney U and Kruskal-Wallis H rank test, the correlations between R TM with RR and TTP were estimated by Spearman's rank test. There were no statistic differences of median R TM among different pathological types with a median R TM of 0.98, 1.27 and 1.05 in squamous cell carcinoma group, adenocarcinoma group and small cell lung cancer group, respectively (Chi-square=0.347, P=0.84). Through a median follow-up of 10 months, a median R TM of 1.08 and 1.21 for squamous cell carcinoma group and small cell lung cancer group in RR≥50% group was greater than 0.88 and 0.91 in RR < 50% group; median R TM in TTP > 9-monthgroups stratified according to pathological type was greater than that in TTP≤9-month groups (1.26, 1.38 and 1.39 versus 0.71, 0.48 and 1.03 for squamous cell carcinoma group, adenocarcinoma group and small cell lung cancer group respectively), but the differences of R TM classified by RR or TTP were not statistically significant (U=63.5, P=0.58; U=71, P=0.057); the Spearman's coefficients of R TM with RR and TTP were -0.105 (P=0.57) and 0.38 (P=0.035). The coefficients of R TM with TTP was 0.47 for non-small cell lung cancer indicating a modest correlation (P=0.048) and 0.043 for small cell lung cancer (P=0.89). Although the results are confounded due to sampling and the greater background tail moments, Spearman's coefficient of R TM with TTP for non-small cell lung cancer indicates a modest positive correlation. The comet assay might be a promising method in predicting intrinsic radiosensitivity of lung cancer cells and techniques for sampling and assaying need to be further improved.

Synergistic Radiosensitization of Lung Cancer Cells using Parthenolide and Low Dose Combinations of Proteasome or Cycloxygenase Inhibitors

Synergistic Radiosensitization of Lung Cancer Cells using Parthenolide and Low Dose Combinations of Proteasome or Cycloxygenase Inhibitors

Resveratrol Enhances Radiosensitivity of Human Non-Small Cell Lung Cancer NCI-H838 Cells Accompanied by Inhibition of Nuclear Factor-Kappa B Activation

Resveratrol, a polyphenol in red wine, possesses many pharmacological activities including cardioprotection, chemoprevention, anti-tumor effects, and nuclear factor-kappa B (NF-kappaB) inactivation. The present study was designed to evaluate the effects and possible mechanism of resveratrol in enhancing radiosensitivity of lung cancer cells. Human non-small cell lung cancer NCI-H838 cells were irradiated with or without resveratrol pretreatment. The surviving fraction and sensitizer enhancement ratio (SER) were estimated by using a colony formation assay and linear-quadratic model. The cell-cycle distribution was evaluated by using propidium iodide staining and flow cytometry. An ELISA-based assay with immobilized oligonucleotide was performed to assess the DNA binding activity of NF-kappaB. Resveratrol had no direct growth-inhibitory effect on NCI-H838 cells treated for 24 hours with doses up to 25 microM. Pretreatment with resveratrol significantly enhanced cell killing by radiation, with an SER up to 2.2. Radiation activated NF-kappaB, an effect reversed by resveratrol pretreatment. Resveratrol resulted in a decrease of cells in the G0/G1 phase and an increase in the S phase. Our results demonstrate that resveratrol enhances the radiosensitivity of NCI-H838 cells accompanied by NF-kappaB inhibition and S-phase arrest.

Modulation of response to radiation of human lung cancer cells following insulin-like growth factor 1 receptor inactivation

Targeted disruption of the insulin-like growth factor 1 receptor (IGF-1R) restricts proliferation of tumor cells and enhances their in vitro radiosensitivity. However, there is little information regarding the effect of IGF-1R expression and function on the lung cancer response to radiotherapy. In this study, we evaluated the cell surface expression of IGF-1R and the antitumoral effect of IGF-1R blockade in combination with irradiation in 6 non-small cell lung cancer (NSCLC) cell lines. All cell lines showed specific IGF-1 binding with an affinity ranging from 0.95×10 −9 to 2.3×10 −9 M, which was evaluated by competitive binding assay. The amount of binding sites ranged from 118 to 377 fmol/mg protein. In one cell line (U1810), the combined treatment led to synergistic cell death and was associated with an accumulation of cells in the G 2 phase. IGF-1R activation was able to obstruct serum starvation/radiation-induced cell death in U1810 cell line. Additive interactions were found for four cell lines (A549, H157, H23 and H125) whereas only subadditive effects were observed in U1752 cell line. Our results indicate that the IGF-1R is present on NSCLC cells and thereby its involvement in the modulation of radiosensitivity in lung cancer cells.