Somatic alterations in cellular DNA underlie almost all human cancers1. The prospect of targeted therapies2 and the development of high-resolution, genome-wide approaches3–8 are now spurring systematic efforts to characterize cancer genomes. Here we report a large-scale project to characterize copy-number alterations in primary lung adenocarcinomas. By analysis of a large collection of tumors (n = 371) using dense single nucleotide polymorphism arrays, we identify a total of 57 significantly recurrent events. We find that 26 of 39 autosomal chromosome arms show consistent large-scale copy-number gain or loss, of which only a handful have been linked to a specific gene. We also identify 31 recurrent focal events, including 24 amplifications and 7 homozygous deletions. Only six of these focal events are currently associated with known mutations in lung carcinomas. The most common event, amplification of chromosome 14q13.3, is found in ~12% of samples. On the basis of genomic and functional analyses, we identify NKX2-1 (NK2 homeobox 1, also called TITF1), which lies in the minimal 14q13.3 amplification interval and encodes a lineage-specific transcription factor, as a novel candidate proto-oncogene involved in a significant fraction of lung adenocarcinomas. More generally, our results indicate that many of the genes that are involved in lung adenocarcinoma remain to be discovered.
Genome-wide association studies (GWASs) have unraveled a large number of cancer risk alleles. Understanding how these allelic variants predispose to disease is a major bottleneck confronting translational application. In this issue, Li and colleagues combine GWASs with The Cancer Genome Atlas (TCGA) to disambiguate the contributions of germline and somatic variants to tumorigenic gene expression programs. They find that close to half of the known risk alleles for estrogen receptor (ER)-positive breast cancer are expression quantitative trait loci (eQTLs) acting upon major determinants of gene expression in tumors.
Malignant pleural mesothelioma (MPM) is a highly aggressive neoplasm arising from the mesothelial cells lining the parietal pleura and it exhibits poor prognosis. Although there has been significant progress in MPM treatment, development of more efficient therapeutic approaches is needed. BMAL1 is a core component of the circadian clock machinery and its constitutive overexpression in MPM has been reported. Here, we demonstrate that BMAL1 may serve as a molecular target for MPM. The majority of MPM cell lines and a subset of MPM clinical specimens expressed higher levels of BMAL1 compared to a nontumorigenic mesothelial cell line (MeT-5A) and normal parietal pleural specimens, respectively. A serum shock induced a rhythmical BMAL1 expression change in MeT-5A but not in ACC-MESO-1, suggesting that the circadian rhythm pathway is deregulated in MPM cells. BMAL1 knockdown suppressed proliferation and anchorage-dependent and independent clonal growth in two MPM cell lines (ACC-MESO-1 and H290) but not in MeT-5A. Notably, BMAL1 depletion resulted in cell cycle disruption with a substantial increase in apoptotic and polyploidy cell population in association with downregulation of Wee1, cyclin B and p21WAF1/CIP1 and upregulation of cyclin E expression. BMAL1 knockdown induced mitotic catastrophe as denoted by disruption of cell cycle regulators and induction of drastic morphological changes including micronucleation and multiple nuclei in ACC-MESO-1 cells that expressed the highest level of BMAL1. Taken together, these findings indicate that BMAL1 has a critical role in MPM and could serve as an attractive therapeutic target for MPM.
apoptosis; BMAL1; mesothelioma; targeted therapy; mitotic catastrophe
Current practice guidelines recommend the combination of chemotherapy and thoracic radiation for locally advanced non-small cell lung cancer (NSCLC). Previous meta-analyses have shown that concurrent chemoradiation (CCRT) may be superior to sequential chemoradiation (SCRT). However, few previous in vitro studies have analyzed these two treatment schedules. In the current study, four lung cancer cell lines harboring wild-type epidermal growth factor receptor, comprising two squamous and two non-squamous cell lines, were used. The IC10 concentrations of three platinum-based regimens were combined with radiation treatment. Cells were irradiated at 0, 2, 4, 6 and 8 Gy using a 137Cs irradiator concurrently or sequentially. Surviving fractions (SFs) were plotted as a function of the radiation dose. In A549 cells, only the docetaxel (Doc) and carboplatin (Carbo) combination showed a significant radiosensitizing effect with CCRT treatment. For the other three cell lines, no difference was identified in the SFs between CCRT and SCRT. An in vitro method of comparing CCRT with SCRT was established using lung cancer cell lines. Overall, no significant difference was detected in the radiosensitizing effect of the two treatment schedules, with the exception of the A549 cell lines treated with Doc/Carbo.
chemotherapy; radiation; concurrent; sequential; carcinoma; non-small cell lung cancer; cell line
Clinical studies have shown that statin use may alter the risk of lung cancer. However, these studies yielded different results. To quantify the association between statin use and risk of lung cancer, we performed a detailed meta-analysis. A literature search was carried out using MEDLINE, EMBASE and COCHRANE database between January 1966 and November 2012. Before meta-analysis, between-study heterogeneity and publication bias were assessed using adequate statistical tests. Fixed-effect and random-effect models were used to calculate the pooled relative risks (RR) and corresponding 95% confidence intervals (CIs). Subgroup analyses, sensitivity analysis and cumulative meta-analysis were also performed. A total of 20 (five randomized controlled trials, eight cohorts, and seven case–control) studies contributed to the analysis. Pooled results indicated a non-significant decrease of total lung cancer risk among all statin users (RR = 0.89, 95% CI [0.78, 1.02]). Further, long-term statin use did not significantly decrease the risk of total lung cancer (RR = 0.80, 95% CI [0.39 , 1.64]). In our subgroup analyses, the results were not substantially affected by study design, participant ethnicity, or confounder adjustment. Furthermore, sensitivity analysis confirmed the stability of results. The findings of this meta-analysis suggested that there was no significant association between statin use and risk of lung cancer. More studies, especially randomized controlled trials and high quality cohort studies are warranted to confirm this association.
The respiratory mucosa is a major coordinator of the inflammatory response in chronic airway diseases, including asthma and chronic obstructive pulmonary disease (COPD). Signals produced by the chronic inflammatory process induce epithelial mesenchymal transition (EMT) that dramatically alters the epithelial cell phenotype. The effects of EMT on epigenetic reprogramming and the activation of transcriptional networks are known, its effects on the innate inflammatory response are underexplored. We used a multiplex gene expression profiling platform to investigate the perturbations of the innate pathways induced by TGFβ in a primary airway epithelial cell model of EMT. EMT had dramatic effects on the induction of the innate pathway and the coupling interval of the canonical and noncanonical NF-κB pathways. Simulation experiments demonstrate that rapid, coordinated cap-independent translation of TRAF-1 and NF-κB2 is required to reduce the noncanonical pathway coupling interval. Experiments using amantadine confirmed the prediction that TRAF-1 and NF-κB2/p100 production is mediated by an IRES-dependent mechanism. These data indicate that the epigenetic changes produced by EMT induce dynamic state changes of the innate signaling pathway. Further applications of systems approaches will provide understanding of this complex phenotype through deterministic modeling and multidimensional (genomic and proteomic) profiling.
TUSC2-defective gene expression is detected in the majority of lung cancers and is associated with worse overall survival. We analyzed the effects of TUSC2 re-expression on tumor cell sensitivity to the AKT inhibitor, MK2206, and explored their mutual signaling connections, in vitro and in vivo. TUSC2 transient expression in three LKB1-defective non-small cell lung cancer (NSCLC) cell lines combined with MK2206 treatment resulted in increased repression of cell viability and colony formation, and increased apoptotic activity. In contrast, TUSC2 did not affect the response to MK2206 treatment for two LKB1-wild type NSCLC cell lines. In vivo, TUSC2 systemic delivery, by nanoparticle gene transfer, combined with MK2206 treatment markedly inhibited growth of tumors in a human LKB1-defective H322 lung cancer xenograft mouse model. Biochemical analysis showed that TUSC2 transient expression in LKB1-defective NSCLC cells significantly stimulated AMP-activated protein kinase (AMPK) phosphorylation and enzymatic activity. More importantly, AMPK gene knockdown abrogated TUSC2-MK2206 cooperation, as evidenced by reduced sensitivity to the combined treatment. Together, TUSC2 re-expression and MK2206 treatment was more effective in inhibiting the phosphorylation and kinase activities of AKT and mTOR proteins than either single agent alone. In conclusion, these findings support the hypothesis that TUSC2 expression status is a biological variable that potentiates MK2206 sensitivity in LKB1-defective NSCLC cells, and identifies the AMPK/AKT/mTOR signaling axis as an important regulator of this activity.
Lung cancers are characterised by abundant genetic diversity with relatively few recurrent mutations occurring at high frequency. However, the genetic alterations often affect a common group of oncogenic signalling pathways. There have been vast improvements in our understanding of the molecular biology that underpins lung cancer in recent years and this has led to a revolution in the diagnosis and treatment of lung adenocarcinomas (ADC) based on the genotype of an individual’s tumour. New technologies are identifying key and potentially targetable genetic aberrations not only in adenocarcinoma but also in squamous cell carcinoma (SCC) of the lung. Lung cancer mutations have been identified in v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), epidermal growth factor receptor (EGFR), BRAF and the parallel phosphatidylinositol 3-kinase (PI3K) pathway oncogenes and more recently in MEK and HER2 while structural rearrangements in ALK, ROS1 and possibly rearranged during transfection (RET) provide new therapeutic targets. Amplification is another mechanism of activation of oncogenes such as MET in adenocarcinoma, fibroblastgrowth factor receptor 1 (FGFR1) and discoidin domain receptor 2 (DDR2) in SCC. Intriguingly, many of these genetic alternations are associated with smoking status and with particular racial and gender differences, which may provide insight into the mechanisms of carcinogenesis and role of host factors in lung cancer development and progression. The role of tumour suppressor genes is increasingly recognised with aberrations reported in TP53, PTEN, RB1, LKB11 and p16/CDKN2A. Identification of biologically significant genetic alterations in lung cancer that lead to activation of oncogenes and inactivation of tumour suppressor genes has the potential to provide further therapeutic opportunities. It is hoped that these discoveries may make a major contribution to improving outcome for patients with this poor prognosis disease.
Lung cancer; mutation; molecular pathology; oncogene; tumour suppressor gene
Access to gene expression data has become increasingly common in recent years; however, analysis has become more difficult as it is often desirable to integrate data from different platforms. Probe mapping across microarray platforms is the first and most crucial step for data integration. In this article, we systematically review and compare different approaches to map probes across seven platforms from different vendors: U95A, U133A and U133 Plus 2.0 from Affymetrix, Inc.; HT-12 v1, HT-12v2 and HT-12v3 from Illumina, Inc.; and 4112A from Agilent, Inc. We use a unique data set, which contains 56 lung cancer cell line samples—each of which has been measured by two different microarray platforms—to evaluate the consistency of expression measurement across platforms using different approaches. Based on the evaluation from the empirical data set, the BLAST alignment of the probe sequences to a recent revision of the Transcriptome generated better results than using annotations provided by Vendors or from Bioconductor's Annotate package. However, a combination of all three methods (deemed the ‘Consensus Annotation’) yielded the most consistent expression measurement across platforms. To facilitate data integration across microarray platforms for the research community, we develop a user-friendly web-based tool, an API and an R package to map data across different microarray platforms from Affymetrix, Illumina and Agilent. Information on all three can be found at http://qbrc.swmed.edu/software/probemapper/.
microarray; gene expression; probe; integrated analysis; probe mapping
The Eph family of receptors is the largest family of receptor tyrosine kinases, but it remains poorly studied in lung cancer. Our aim was to systematically explore the human Eph receptors and their ligands, the ephrins, in lung adenocarcinoma. The prognostic impact of Eph receptor and ephrin gene expression was analyzed using 2 independent cohorts of lung adenocarcinoma. Gene expression profiles in lung adenocarcinoma versus normal adjacent lung were studied in 3 independent cohorts and in cell lines. Gene expression profiles were validated with quantitative polymerase chain reaction (qPCR) and Western blotting in cell lines. Functional studies to assess the role of Eph receptor A4 (EphA4) were performed in vitro. The biological effects of EphA4 in lung cancer cell lines were assayed following overexpression and knockdown. Of the 11 Eph receptors and 8 ephrins analyzed, only EphA4 and ephrin A1 gene expression were consistently associated with an improved outcome in patients with lung adenocarcinoma. Expression levels of EphA4 by microarray correlated well with expression levels measured by qPCR and Western blotting. EphA4 overexpression reduced cell migration and invasion but did not affect cell cycle, apoptosis, or drug sensitivity. Surprisingly, EphA4 was expressed at higher levels in cancer versus non-cancer tissues and cell lines. EphA4 gene expression is associated with an improved outcome in patients with resected lung adenocarcinoma, likely by affecting cancer cell migration and invasion.
non-small cell lung cancer; adenocarcinoma; Eph receptor; ephrin; prognosis
Ionizing radiation composed of accelerated ions of high atomic number (Z) and energy (HZE) deposits energy and creates damage in cells in a discrete manner as compared to the random deposition of energy and damage seen with low energy radiations such as γ- or x-rays. Such radiations can be highly effective at cell killing, transformation, and oncogenesis, all of which are concerns for the manned space program and for the burgeoning field of HZE particle radiotherapy for cancer. Furthermore, there are differences in the extent to which cells or tissues respond to such exposures that may be unrelated to absorbed dose. Therefore, we asked whether the energy deposition patterns produced by different radiation types would cause different molecular responses. We performed transcriptome profiling using human bronchial epithelial cells (HBECs) after exposure to γ-rays and to two different HZE particles (28Si and 56Fe) with different energy transfer properties to characterize the molecular response to HZE particles and γ-rays as a function of dose, energy deposition pattern, and time post-irradiation.
Clonogenic assay indicated that the relative biological effectiveness (RBE) for 56Fe was 3.91 and for 28Si was 1.38 at 34% cell survival. Unsupervised clustering analysis of gene expression segregated samples according to the radiation species followed by the time after irradiation, whereas dose was not a significant parameter for segregation of radiation response. While a subset of genes associated with p53-signaling, such as CDKN1A, TRIM22 and BTG2 showed very similar responses to all radiation qualities, distinct expression changes were associated with the different radiation species. Gene enrichment analysis categorized the differentially expressed genes into functional groups related to cell death and cell cycle regulation for all radiation types, while gene pathway analysis revealed that the pro-inflammatory Acute Phase Response Signaling was specifically induced after HZE particle irradiation. A 73 gene signature capable of predicting with 96% accuracy the radiation species to which cells were exposed, was developed.
These data suggest that the molecular response to the radiation species used here is a function of the energy deposition characteristics of the radiation species. This novel molecular response to HZE particles may have implications for radiotherapy including particle selection for therapy and risk for second cancers, risk for cancers from diagnostic radiation exposures, as well as NASA’s efforts to develop more accurate lung cancer risk estimates for astronaut safety. Lastly, irrespective of the source of radiation, the gene expression changes observed set the stage for functional studies of initiation or progression of radiation-induced lung carcinogenesis.
Gene expression; HZE particles; Ionizing radiation; Human bronchial epithelial cells
Nicotine replacement therapy (NRT) is a valuable, proven, and U.S. Food and Drug Administration–approved tool for smoking cessation. However, the discoveries of functional nicotinic acetylcholine receptors (nAChR) on lung epithelial and cancer cells and of nAChR polymorphisms associated with lung cancer risk, in addition to a large number of preclinical studies indicating that nicotine may promote or facilitate cancer development and growth, have prompted concern that NRT, although important for smoking cessation, may actually augment lung carcinogenesis. Therefore, it is of great public health interest that two independent studies reported in this issue of the journal (Murphy and colleagues, beginning on page 1752, and Maier and colleagues, beginning on page 1743) showed that nicotine given in drinking water at a dose to achieve blood concentrations in mice similar to those achieved in people receiving NRT did not enhance lung carcinogenesis or tumor growth in several mouse models of lung cancer. Effective non-nicotine alternatives to NRT, such as varenicline and bupropion, are also available and perhaps better than NRT for smoking cessation therapy. In the near future, nicotine vaccines will likely be added to the smoking cessation armamentarium. However, the normal and pathophysiologic role of nicotine, nAChRs, and the signaling pathways they activate in lung epithelial cells and lung cancer still requires elucidation.
Few prognostic biomarkers are approved for clinical use primarily because their initial performance cannot be repeated in independent datasets. We posited that robust biomarkers could be obtained by identifying deregulated biological processes shared among tumor types having a common etiology. We performed a gene set enrichment analysis in 20 publicly available gene expression datasets comprising 1968 patients having one of the three most common tobacco-related cancers (lung, bladder, head and neck) and identified cell cycle related genes as the most consistently prognostic class of biomarkers in bladder (BL) and lung adenocarcinoma (LUAD). We also found the prognostic value of 13 of 14 published BL and LUAD signatures were dependent on cell cycle related genes, supporting the importance of cell cycle related biomarkers for prognosis. Interestingly, no prognostic gene classes were identified in squamous cell lung carcinoma or head and neck squamous cell carcinoma. Next, a specific 31 gene cell cycle proliferation (CCP) signature, previously derived in prostate tumors was evaluated and found predictive of outcome in BL and LUAD cohorts in univariate and multivariate analyses. Specifically, CCP score significantly enhanced the predictive ability of multivariate models based on standard clinical variables for progression in BL patients and survival in LUAD patients in multiple cohorts. We then generated random CCP signatures of various sizes and found sets of 10–15 genes had robust performance in these BL and LUAD cohorts, a finding that was confirmed in an independent cohort. Our work characterizes the importance of cell cycle related genes in prognostic signatures for BL and LUAD patients and identifies a specific signature likely to survive additional validation.
Mutations in the v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) play a critical role in cancer cell growth and resistance to therapy. Most mutations occur at codons 12 and 13. In colorectal cancer, the presence of any mutant KRas amino acid substitution is a negative predictor of patient response to targeted therapy. However, in non–small cell lung cancer (NSCLC), the evidence that KRAS mutation is a predictive factor is conflicting.
We used data from a molecularly targeted clinical trial for 215 patients with tissues available out of 268 evaluable patients with refractory NSCLC to examine associations between specific mutant KRas proteins and progression-free survival and tumor gene expression. Transcriptome microarray studies of patient tumor samples and reverse-phase protein array studies of a panel of 67 NSCLC cell lines with known substitutions in KRas and in immortalized human bronchial epithelial cells stably expressing different mutant KRas proteins were used to investigate signaling pathway activation. Molecular modeling was used to study the conformations of wild-type and mutant KRas proteins. Kaplan–Meier curves and Cox regression were used to analyze survival data. All statistical tests were two-sided.
Patients whose tumors had either mutant KRas-Gly12Cys or mutant KRas-Gly12Val had worse progression-free survival compared with patients whose tumors had other mutant KRas proteins or wild-type KRas (P = .046, median survival = 1.84 months) compared with all other mutant KRas (median survival = 3.35 months) or wild-type KRas (median survival = 1.95 months). NSCLC cell lines with mutant KRas-Gly12Asp had activated phosphatidylinositol 3-kinase (PI-3-K) and mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) signaling, whereas those with mutant KRas-Gly12Cys or mutant KRas-Gly12Val had activated Ral signaling and decreased growth factor–dependent Akt activation. Molecular modeling studies showed that different conformations imposed by mutant KRas may lead to altered association with downstream signaling transducers.
Not all mutant KRas proteins affect patient survival or downstream signaling in a similar way. The heterogeneous behavior of mutant KRas proteins implies that therapeutic interventions may need to take into account the specific mutant KRas expressed by the tumor.
EMT has been associated with metastatic spread and EGFR inhibitor resistance. We developed and validated a robust 76-gene EMT signature using gene expression profiles from four platforms using NSCLC cell lines and patients treated in the BATTLE study.
We conducted an integrated gene expression, proteomic, and drug response analysis using cell lines and tumors from NSCLC patients. A 76-gene EMT signature was developed and validated using gene expression profiles from four microarray platforms of NSCLC cell lines and patients treated in the BATTLE (Biomarker-integrated Approaches of Targeted Therapy for Lung Cancer Elimination) study, and potential therapeutic targets associated with EMT were identified.
Compared with epithelial cells, mesenchymal cells demonstrated significantly greater resistance to EGFR and PI3K/Akt pathway inhibitors, independent of EGFR mutation status, but more sensitivity to certain chemotherapies. Mesenchymal cells also expressed increased levels of the receptor tyrosine kinase Axl and showed a trend towards greater sensitivity to the Axl inhibitor SGI-7079, while the combination of SGI-7079 with erlotinib reversed erlotinib resistance in mesenchymal lines expressing Axl and in a xenograft model of mesenchymal NSCLC. In NSCLC patients, the EMT signature predicted 8-week disease control in patients receiving erlotinib, but not other therapies.
We have developed a robust EMT signature that predicts resistance to EGFR and PI3K/Akt inhibitors, highlights different patterns of drug responsiveness for epithelial and mesenchymal cells, and identifies Axl as a potential therapeutic target for overcoming EGFR inhibitor resistance associated with the mesenchymal phenotype
lung cancer; EMT; EGFR inhibition; PI3K inhibition; Axl
Inhibitors of apoptosis proteins (IAPs) are key regulators of apoptosis and are inhibited by the second mitocondrial activator of caspases (SMAC). Previously, a small subset of TNFα-expressing non-small cell lung cancers (NSCLCs) was found to be sensitive to SMAC mimetics alone. In this study we determined if a SMAC mimetic (JP1201) could sensitize non-responsive NSCLC cell lines to standard chemotherapy. We found that JP1201 sensitized NSCLCs to doxorubicin, erlotinib, gemcitabine, paclitaxel, vinorelbine, and the combination of carboplatin with paclitaxel in a synergistic manner at clinically achievable drug concentrations. Sensitization did not occur with platinum alone. Furthermore, sensitization was specific for tumor compared to normal lung epithelial cells, increased in NSCLCs harvested after chemotherapy treatment, and did not induce TNFα secretion. Sensitization also was enhanced in vivo with increased tumor inhibition and increased survival of mice carrying xenografts. These effects were accompanied by caspase 3, 4, and 9 activation, indicating that both mitochondrial and ER stress-induced apoptotic pathways are activated by the combination of vinorelbine and JP1201. Chemotherapies that induce cell death through the mitochondrial pathway required only inhibition of XIAP for sensitization, while chemotherapies that induce cell death through multiple apoptotic pathways required inhibition of cIAP1, cIAP2, and XIAP. Therefore, the data suggest that IAP-targeted therapy using a SMAC mimetic provides a new therapeutic strategy for synergistic sensitization of NSCLCs to standard chemotherapy agents, which appears to occur independently of TNFα secretion.
non-small cell lung cancer; smac mimetic; vinorelbine; gemcitabine; IAPs
Loss of terminal cell differentiation promotes tumorigenesis. 15-LOX-1 contributes to terminal cell differentiation in normal cells. The mechanistic significance of 15-LOX-1 expression loss in human cancers to terminal cell differentiation suppression is unknown. In a screen of 128 cancer cell lines representing more than 20 types of human cancer, we found that 15-LOX-1 mRNA expression levels were markedly lower than levels in terminally differentiated cells. Relative expression levels of 15-LOX-1 (relative to the level in terminally differentiated primary normal human-derived bronchial epithelial cells) were lower in 79% of the screened cancer cell lines than relative expression levels of p16 (INK4A), which promotes terminal cell differentiation and is considered one of the most commonly lost tumor suppressor genes in cancer cells. 15-LOX-1 was expressed during terminal differentiation in three-dimensional air-liquid interface cultures, and 15-LOX-1 expression and terminal differentiation occurred in immortalized non-transformed bronchial epithelial but not lung cancer cell lines. 15-LOX-1 expression levels were lower in human tumors than paired normal lung epithelia. Short hairpin RNA-mediated downregulation of 15-LOX-1 in Caco-2 cells blocked enterocyte-like differentiation, disrupted tight junction formation, and blocked E-cadherin and ZO-1 localization to the cell wall membrane. 15-LOX-1 episomal expression in Caco-2 and HT-29 colon cancer cells induced differentiation. Our findings indicate that 15-LOX-1 downregulation in cancer cells is an important mechanism for terminal cell differentiation dysregulation and support the potential therapeutic utility of 15-LOX-1 re-expression to inhibit tumorigenesis.
15-lipoxygenase-1; terminal cell differentiation; tumorigenesis
Cisplatin, a commonly used chemotherapeutic, is associated with ototoxicity, renal toxicity and neurotoxicity, thus identifying means to increase the therapeutic index of cisplatin may allow for improved outcomes. A SNP (rs4343077) within EPS8, discovered through a genome wide association study of cisplatin-induced cytotoxicity and apoptosis in lymphoblastoid cell lines (LCLs), provided impetus to further study this gene. The purpose of this work was to evaluate the role of EPS8 in cellular susceptibility to cisplatin in cancerous and non-cancerous cells. We used EPS8 RNA interference to determine the effect of decreased EPS8 expression on LCL and A549 lung cancer cell sensitivity to cisplatin. EPS8 knockdown in LCLs resulted in a 7.9% increase in cisplatin-induced survival (P = 1.98×10−7) and an 8.7% decrease in apoptosis (P = 0.004) compared to control. In contrast, reduced EPS8 expression in lung cancer cells resulted in a 20.6% decrease in cisplatin-induced survival (P = 5.08×10−5). We then investigated an EPS8 inhibitor, mithramycin A, as a potential agent to increase the therapeutic index of cisplatin. Mithramycin A decreased EPS8 expression in LCLs resulting in decreased cellular sensitivity to cisplatin as evidenced by lower caspase 3/7 activation following cisplatin treatment (42.7%±6.8% relative to control P = 0.0002). In 5 non-small-cell lung carcinoma (NSCLC) cell lines, mithramycin A also resulted in decreased EPS8 expression. Adding mithramycin to 4 NSCLC cell lines and a bladder cancer cell line, resulted in increased sensitivity to cisplatin that was significantly more pronounced in tumor cell lines than in LCL lines (p<0.0001). An EGFR mutant NSCLC cell line (H1975) showed no significant change in sensitivity to cisplatin with the addition of mithramycin treatment. Therefore, an inhibitor of EPS8, such as mithramycin A, could improve cisplatin treatment by increasing sensitivity of tumor relative to normal cells.
On June 27–28, 2011 scientists from the National Cancer Institute (NCI), NASA, and academia met in Bethesda to discuss major lung cancer issues confronting each organization. For NASA – available data suggest lung cancer is the largest potential cancer risk from space travel for both men and women and quantitative risk assessment information for mission planning is needed. In space the radiation risk is from high energy and charge (HZE) nuclei (such as Fe) and high energy protons from solar flares and not from gamma radiation. By contrast the NCI is endeavoring to estimate the increased lung cancer risk from the potential wide-spread implementation of computed tomography (CT) screening in individuals at high risk for developing lung cancer based on the National Lung Cancer Screening Trial (NLST). For the latter, exposure will be x-rays from CT scans from the screening (which uses “low dose” CT scans) and also from follow-up scans used to evaluate abnormalities found during initial screening. Topics discussed included the risk of lung cancer arising after HZE particle, proton, and low dose Earth radiation exposure. The workshop examined preclinical models, epidemiology, molecular markers, “omics” technology, radiobiology issues, and lung stem cells (LSC) that relate to the development of lung cancer.
We have developed a method for the parallel analysis of multiple CpG sites in genomic DNA for their state of methylation. Hypermethylation of CpG islands within the promoters and 5′ exons of genes has been found to be a mechanism of transcriptional inactivation associated with a variety of tumors. The method that we developed relies on the differential reactivity of methylated and unmethylated cytosines with sodium bisulfite, which exclusively converts unmethylated cytosines to deoxyuracils. The resulting sequence changes are determined with single-nucleotide resolution by hybridization to an oligonucleotide array. Cohybridization with a reference sample containing a different label provides an internal standard for assessment of methylation state. This method provides advantages in parallelism over existing methods of methylation analysis. We have demonstrated this technique with a region from the promoter of the tumor suppressor gene p16, which is hypermethylated in many cancers.
Hypermethylation; CpG island; Oligonucleotide array; Sodium bisulfite; Tumor suppressor
We have positionally cloned and characterized a new calcium channel auxiliary subunit, α2δ-2 (CACNA2D2), which shares 56% amino acid identity with the known α2δ-1 subunit. The gene maps to the critical human tumor suppressor gene region in chromosome 3p21.3, showing very frequent allele loss and occasional homozygous deletions in lung, breast, and other cancers. The tissue distribution of α2δ-2 expression is different from α2δ-1, and α2δ-2 mRNA is most abundantly expressed in lung and testis and well expressed in brain, heart, and pancreas. In contrast, α2δ-1 is expressed predominantly in brain, heart, and skeletal muscle. When co-expressed (via cRNA injections) with α1B and β3 subunits in Xenopus oocytes, α2δ-2 increased peak size of the N-type Ca2+ currents 9-fold, and when co-expressed with α1C or α1G subunits in Xenopus oocytes increased peak size of L-type channels 2-fold and T-type channels 1.8-fold, respectively. Anti-peptide antibodies detect the expression of a 129-kDa α2δ-2 polypeptide in some but not all lung tumor cells. We conclude that the α2δ-2 gene encodes a functional auxiliary subunit of voltage-gated Ca2+ channels. Because of its chromosomal location and expression patterns, CACNA2D2 needs to be explored as a potential tumor suppressor gene linking Ca2+ signaling and lung, breast, and other cancer pathogenesis. The homologous location on mouse chromosome 9 is also the site of the mouse neurologic mutant ducky (du), and thus, CACNA2D2 is also a candidate gene for this inherited idiopathic generalized epilepsy syndrome.
RASSF1A is a recently identified 3p21.3 tumor suppressor gene. The high frequency of epigenetic inactivation of this gene in a wide range of human sporadic cancers including non-small cell lung cancer (NSCLC) and neuroblastoma suggests that RASSF1A inactivation is important for tumor development. Although little is known about the function of RASSF1A, preliminary data suggests that it may have multiple functions. To gain insight into RASSF1A functions in an unbiased manner, we have characterized the expression profile of a lung cancer cell line (A549) transfected with RASSF1A. Initially we demonstrated that transient expression of RASSF1A into the NSCLC cell line A549 induced G1 cell cycle arrest, as measured by propidium iodide staining. Furthermore, an-nexin-V staining showed that RASSF1A-expressing cells had an increased sensitivity to staurosporine-induced apoptosis. We then screened a cDNA microarray containing more than 6000 probes to identify genes differentially regulated by RASSF1A. Sixty-six genes showed at least a 2-fold change in expression. Among these were many genes with relevance to tumorigenesis involved in transcription, cytoskeleton, signaling, cell cycle, cell adhesion, and apoptosis. For 22 genes we confirmed the microarray results by real-time RT-PCR and/or Northern blotting. In silico, we were able to confirm the majority of these genes in other NSCLC cell lines using published data on gene expression profiles. Furthermore, we confirmed 10 genes at the RNA level in two neuroblastoma cell lines, indicating that these RASSF1A target genes have relevance in non-lung cell backgrounds. Protein analysis of six genes (ETS2, Cyclin D3, CDH2, DAPK1, TXN, and CTSL) showed that the changes induced by RASSF1A at the RNA level correlated with changes in protein expression in both non-small cell lung cancer and neuroblastoma cell lines. Finally, we have used a transient assay to demonstrate the induction of CDH2 and TGM2 by RASSF1A in NSCLC cell lines. We have identified several novel targets for RASSF1A tumor suppressor gene both at the RNA and the protein levels in two different cellular backgrounds. The identified targets are involved in diverse cellular processes; this should help toward understanding mechanisms that contribute to RASSF1A biological activity.
The CACNA2D2 gene, a new subunit of the Ca2+-channel complex, was identified in the homozygous deletion region of chromosome 3p21.3 in human lung and breast cancers. Expression deficiency of the CACNA2D2 in cancer cells suggests a possible link of it to Ca2+ signaling in the pathogenesis of lung cancer and other cancers. We investigated the effects of overexpression of CACNA2D2 on intracellular Ca2+ contents, mitochondria homeostasis, cell proliferation, and apoptosis by adenoviral vector-mediated wild-type CACNA2D2 gene transfer in 3p21.3-deficient nonsmall cell lung cancer cell lines. Exogenous expression of CACNA2D2 significantly inhibited tumor cell growth compared with the controls. Overexpression of CACNA2D2 induced apoptosis in H1299 (12.5%), H358 (13.7%), H460 (22.3%), and A549 (50.1%) cell lines. Levels of intracellular free Ca2+ were elevated in AdCACNA2D2-transduced cells compared with the controls. Mitochondria membrane depolarization was observed prior to apoptosis in Ad-CACNA2D2 and Adp53-transduced H460 and A549 cells. Release of cyt c into the cytosol, caspase 3 activation, and PARP cleavage were also detected in these cells. Together, these results suggest that one of the pathways in CACNA2D2-induced apoptosis is mediated through disruption of mitochondria membrane integrity, the release of cyt c, and the activation of caspases, a process that is associated with regulation of cytosolic free Ca2+ contents.
tumor suppressor genes; apoptosis; calcium channel proteins; human chromosome 3p21.3; lung cancer
A group of candidate tumor suppressor genes (designated CACNA2D2, PL6, 101F6, NPRL2, BLU, RASSF1, FUS1, HYAL2, and HYAL1) has been identified in a 120-kb critical tumor homozygous deletion region (found in lung and breast cancers) of human chromosome 3p21.3. We studied the effects of six of these 3p21.3 genes (101F6, NPRL2, BLU, FUS1, HYAL2, and HYAL1) on tumor cell proliferation and apoptosis in human lung cancer cells by recombinant adenovirus-mediated gene transfer in vitro and in vivo. We found that forced expression of wild-type FUS1, 101F6, and NPRL2 genes significantly inhibited tumor cell growth by induction of apoptosis and alteration of cell cycle processes in 3p21.3 120-kb region-deficient (homozygous) H1299 and A549 cells but not in the 3p21.3 120-kb region-heterozygous H358 and the normal human bronchial epithelial cells. Intratumoral injection of Ad-101F6, Ad-FUS1, Ad-NPRL2, and Ad-HYAL2 vectors or systemic administration of protamine-complexed vectors significantly suppressed growth of H1299 and A549 tumor xenografts and inhibited A549 experimental lung metastases in nu/nu mice. Together, our results, coupled with other studies demonstrating a tumor suppressor role for the RASSSF1A isoform, suggest that multiple contiguous genes in the 3p21.3 120-kb chromosomal region may exhibit tumor suppressor activity in vitro and in vivo.