Targeting the Epigenome for the Treatment and Prevention of Lung Cancer

Real world study of the continuation of bevacizumab beyond disease progression after first-line treatment containing bevacizumab in Chinese patients with advanced non-small cell lung cancer

Background

Bevacizumab (Bev) plus platinum‐based chemotherapy is a standard first‐line treatment option for advanced non‐squamous non‐small cell lung cancer (NS‐NSCLC). We evaluated the efficacy and safety of continuing Bev in Chinese patients with advanced NS‐NSCLC progression after first‐line treatment containing Bev in a real‐world setting.

Methods

The data of 118 patients with advanced NS‐NSCLC who received Bev between July 2009 and July 2017 were retrospectively collected. The patients were divided into groups: 15 in Bev first‐line, 82 in Bev ≥ second‐line, and 21 in Bev cross‐lines. The primary endpoint was overall survival; secondary objectives were progression‐free survival, objective response rate, disease control rate, and safety.

Results

The overall survival was 21.8, 32.5, and 18.9 months (P = 0.092) in the overall population and 39.3, 25.8, and 15.0 months (P = 0.347) in the wild‐type population in the Bev first‐line, Bev ≥ second‐line, and Bev cross‐lines groups, respectively. There were no significant differences in progression‐free survival of second‐line treatment between the groups in the overall population: 2.6, 3.7, and 3.2 months in the Bev first‐line, Bev ≥ second‐line, and Bev cross‐lines groups, respectively (P = 0.796). No statistically significant improvement in objective response or disease control rates in the Bev cross‐lines group was observed. No unexpected or severe adverse events were recorded.

Conclusion

We found no benefit in continuing Bev treatment beyond progression after first‐line treatment containing Bev for patients with advanced NS‐NSCLC. Further research of validated predictive biomarkers of response to treatment after long‐term antiangiogenic therapy is required.

Pulmonary Metastases Exhibit Epigenetic Clonality: Implications for Precision Cancer Therapy

BACKGROUND

Development of effective cancer therapies may be limited by intratumoral heterogeneity, which facilitates outgrowth and organ-specific dissemination of treatment resistant clones. At present, limited information is available regarding epigenetic landscapes of pulmonary metastases. This study was undertaken to characterize epigenetic signatures of pulmonary metastases and to identify potential therapeutic targets.

METHODS

RNA and DNA were extracted from 65 pulmonary metastases resected from 12 patients (5 with sarcoma, 7 with adrenocortical carcinoma). Quantitative reverse transcription polymerase chain reaction techniques were used to evaluate expression levels of cancer-testis (CT) genes (NY-ESO-1, MAGE-A3, MAGE-A9, MAGE-A12, GAGE1, CT-45, SSX-1, and SSX-2), tumor suppressor (TS) genes (p16 and RASSF1A), and genes encoding epigenetic modifiers (DNMT1, DNMT3A, DNMT3B, EZH2, EED, and SUZ12), aberrantly expressed in human malignant diseases. Pyrosequencing techniques were used to quantitate DNA methylation levels in LINE1, NBL2, and D4Z4 repetitive sequences and promoter methylation status of differentially regulated genes. Results of these analyses were compared with a standardized panel of normal lung tissues.

RESULTS

Pulmonary metastases exhibited histologically related and patient-specific global DNA demethylation. Significant interpatient heterogeneity of gene expression was observed even among patients with similar tumor histologic features. Epigenetic signatures appeared consistent among metastases from the same patient, irrespective of the time of resection (synchronous/metachronous) or the anatomic location. EZH2, EED, and SUZ12 (core components of Polycomb repressive complex-2 [PRC-2]) were upregulated in the majority of metastases.

CONCLUSIONS

Pulmonary metastases exhibit patient-specific epigenetic clonality, which may be exploited for precision therapies targeting aberrant CT or TS gene expression. PRC-2 may be a shared target for epigenetic therapy of pulmonary metastases.

Switch maintenance treatment with oral vinorelbine and bevacizumab after induction chemotherapy with cisplatin, gemcitabine and bevacizumab in patients with advanced non-squamous non-small cell lung cancer: a phase II study

The present study evaluated the efficacy and safety of cisplatin (Cis), gemcitabine (Gem) and bevacizumab (Bev), followed by maintenance treatment with Bev and oral vinorelbine (Vnb), in patients with advanced non-squamous non-small cell lung cancer (NSCLC). The patients were administered six cycles of induction chemotherapy consisting of intravenously (i.v.) Cis 70 mg/m(2) on day 1 plus i.v. Gem 1000 mg/m(2) on days 1 and 8, plus i.v. Bev 7.5 mg/kg on day 1, every 3 weeks. Patients who did not experience tumor progression remained on maintenance treatment with Bev combined with oral Vnb 60 mg/m(2) weekly until occurrence of disease progression or unacceptable toxicity. Thirty-seven patients were enrolled: The median age was 67 years (range 38-81); 22 patients were male, and 30 patients had stage IV tumors. The response rate was 32.4 % (95 % CI 18-49.7). The 9-month disease-control rate was 45.9 %. The median PFS was 8.4 months (95 % CI 4.4-10.7), and the median OS was 18.1 months (95 % CI 15.3-20.8 months). Grade 3-4 neutropenia occurred in 6 (16.2 %) patients and grade 3-4 thrombocytopenia in four (10.8 %) patients during induction chemotherapy. Bev- or Vnb-associated toxicities were mild. Switch maintenance treatment with Bev and oral Vnb after first-line Cis, Gem and Bev is feasible in patients with non-squamous NSCLC and may achieve encouraging results in terms of PFS and OS.

An exceptional overall survival using bevacizumab beyond progression in a patient with non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common malignancy and the leading cause of cancer death worldwide. In this report, we describe a patient with NSCLC who was treated with continuation of Bevacizumab (Bev) beyond progression to first-line Bev-based chemotherapy. The prolonged treatment with Bev by continuing the inhibition of VEGF beyond first-progression has a strong rationale. Nevertheless, few data exist regarding the efficacy and safety of Bev beyond first line of chemotherapy progression in NSCLC patients. Further studies including a large number of patients are needed, in order to select patients who could benefit from this approach.

Inhibition of human esophageal squamous cell carcinomas by targeted silencing of tumor enhancer genes: an overview

Esophageal cancer has been reported as the ninth most common malignancy and ranks as the sixth most frequent cause of death worldwide. Esophageal cancer treatment involves surgery, chemotherapy, radiation therapy, or combination therapy. Novel strategies are needed to boost the oncologic outcome. Recent advances in the molecular biology of esophageal cancer have documented the role of genetic alterations in tumorigenesis. Oncogenes serve a pivotal function in tumorigenesis. Targeted therapies are directed at the unique molecular signature of cancer cells for enhanced efficacy with low toxicity. RNA interference (RNAi) technology is a powerful tool for silencing endogenous or exogenous genes in mammalian cells. Related results have shown that targeting oncogenes with siRNAs, specifically the mRNA, effectively reduces tumor cell proliferation and induces apoptotic cell death. This article will briefly review studies on silencing tumor enhancer genes related to the induction of esophageal cancer.

Effects of treatment with histone deacetylase inhibitors in solid tumors: a review based on 30 clinical trials

It has been found that the epigenetic silence of tumor suppressor genes induced by overexpression of histone deacetylases (HDACs) plays an important role in carcinogenesis. HDAC inhibitors (HDACi) that block the activity of specific HDACs have emerged as the accessory therapeutic agents for multiple human cancers. To better understand the effects of HDACi in cancer treatment, we carried out a review based on 30 published clinical trials to determine whether HDACi will benefit patients with solid tumors. Information of complete response, partial response, stable disease, objective responses and objective response rate was collected to assess clinical outcomes. A lack of therapeutic effects was observed when HDACi was used as a single agent. However, when HDACi treatment was combined with other agents, it appeared to increase the anti-tumor activity. High-quality studies are required to better understand the clinical effects of HDACi.

Detection of cancer-specific epigenomic changes in biofluids: powerful tools in biomarker discovery and application

The genetic and epigenetic material originating from tumour that can be found in body fluids of individuals with cancer harbours tumour-specific alterations and represents an attractive target for biomarker discovery. Epigenetic changes (DNA methylation, histone modifications and non-coding RNAs) are present ubiquitously in virtually all types of human malignancies and may appear in early cancer development, and thus they provide particularly attractive markers with broad applications in diagnostics. In addition, because changes in the epigenome may constitute a signature of specific exposure to certain risk factors, they have the potential to serve as highly specific biomarkers for risk assessment. While reliable detection of cancer-specific epigenetic changes has proven to be technically challenging, a substantial progress has been made in developing the methodologies that allow an efficient and sensitive detection of epigenomic changes using the material originating from body fluids. In this review we discuss the application of epigenomics as a tool for biomarker research, with the focus on the analysis of DNA methylation in biofluids.

Phase I study of 5-aza-2'-deoxycytidine in combination with valproic acid in non-small-cell lung cancer

PURPOSE

Non-small-cell lung cancer (NSCLC) accounts for the majority of lung cancer and is the most common cause of cancer death in industrialized countries. Epigenetic modifications are observed universally during the tumorigenesis of lung cancer. The development of epigenetic-modulating agents utilizing the synergism between hypomethylating agents and histone deacetylase (HDAC) inhibitors provides a novel therapeutic approach in treating NSCLC.

METHODS

We performed a phase I trial combining 5-aza-2'-deoxycytidine (decitabine) and valproic acid (VPA), in patients with advanced stage NSCLC. Patients were treated with escalating doses of decitabine (5-15 mg/m(2)) IV for 10 days in combination with VPA (10-20 mg/kg/day) PO on days 5-21 of a 28-day cycle. Pharmacokinetic and pharmacodynamic analysis included decitabine pharmacokinetics and fetal hemoglobin expression.

RESULTS

Eight patients were accrued to this phase I study. All patients had advanced NSCLC and had received prior chemotherapy. Eastern Cooperative Oncology Group performance status was 0-2. Major toxicities included myelosuppression and neurotoxicity. Dose-limiting toxicity was seen in two patients suffering grade 3 neurotoxicity during cycle one including disorientation, lethargy, memory loss, and ataxia at dose level 1. One patient had grade 3 neutropenia at the de-escalated dose. No objective response was observed, and stable disease was seen in one patient. Fetal hemoglobin levels increased after cycle one in all seven patients with evaluable results.

CONCLUSIONS

We observed that decitabine and valproic acid are an effective combination in reactivating hypermethylated genes as demonstrated by re-expressing fetal hemoglobin. This combination in patients with advanced stage IV NSCLC, however, is limited by unacceptable neurological toxicity at a relatively low dosage. Combining hypomethylating agents with alternative HDAC inhibitors that lack the toxicity of VPA should be explored further.

Targeting epigenetic mediators of gene expression in thoracic malignancies

Lung and esophageal cancers and malignant pleural mesotheliomas are highly lethal neoplasms that are leading causes of cancer-related deaths worldwide. Presently, limited information is available pertaining to epigenetic mechanisms mediating initiation and progression of these neoplasms. The following presentation will focus on the potential clinical relevance of epigenomic alterations in thoracic malignancies mediated by DNA methylation, perturbations in the histone code, and polycomb group proteins, as well as ongoing translational efforts to target epigenetic regulators of gene expression for treatment of these neoplasms. This article is part of a Special Issue entitled: Chromatin in time and space.

Inhibition of histone lysine methylation enhances cancer-testis antigen expression in lung cancer cells: implications for adoptive immunotherapy of cancer

Cancer-testis antigens (CTA), such as NY-ESO-1, MAGE-A1, and MAGE-A3, are immunogenic proteins encoded by genes, which are normally expressed only in male germ cells but are activated by ill-defined epigenetic mechanisms in human tumors, including lung cancers. Previously, we reported induction of these CTAs in cancer cells, but not normal cells, by DNA-demethylating agents and histone deacetylase inhibitors using clinically achievable exposure conditions. In the present study, we evaluated chromatin alterations associated with repression/activation of cancer-testis genes in lung cancer cells to further develop gene-induction regimens for cancer immunotherapy. Repression of NY-ESO-1, MAGE-A1, and MAGE-A3 coincided with DNA hypermethylation, recruitment, and binding of polycomb-group proteins, and histone heterochromatin modifications within the promoters of these genes. Derepression coincided with DNA demethylation, dissociation of polycomb proteins, and presence of euchromatin marks within the respective promoters. Short hairpin RNAs were used to inhibit several histone methyltransferases (KMT) and histone demethylases (KDM) that mediate histone methylation and repress gene expression. Knockdown of KMT6, KDM1, or KDM5B markedly enhanced deoxyazacytidine (DAC)-mediated activation of these cancer-testis genes in lung cancer cells. DZNep, a pharmacologic inhibitor of KMT6 expression, recapitulated the effects of KMT6 knockdown. Following DAC-DZNep exposure, lung cancer cells were specifically recognized and lysed by allogeneic lymphocytes expressing recombinant T-cell receptors recognizing NY-ESO-1 and MAGE-A3. Combining DNA-demethylating agents with compounds, such as DZNep, that modulate histone lysine methylation may provide a novel epigenetic strategy to augment cancer-testis gene expression as an adjunct to adoptive cancer immunotherapy.

Bmi1 regulates cell fate via tumor suppressor WWOX repression in small-cell lung cancer cells

Mortality from lung cancer is important worldwide. Recently, epigenetic aberration of lung cancer, not only genomic DNA methylation but also chromatin modification, has become an important target for lung cancer research, although previous research has demonstrated that lung cancer develops as a result of both environmental and genetic factors. Here, we demonstrated that an epigenetic regulator/polycomb group protein Bmi1 is more highly expressed in small-cell lung cancer (SCLC) than in non-small-cell lung cancer by immunohistochemical analysis. In vitro experiments indicated that Bmi1 reduction by lentivirus-derived shRNA significantly suppressed proliferation, colony formation and in vivo tumor formation. Importantly, apoptosis was induced by Bmi1 depletion in small-cell lung cancer cells. Furthermore, a tumor suppressor WWOX was identified as a Bmi1 target in the cells by a chromatin immunoprecipitation assay and a quantitative real-time PCR assay; WWOX had a role as a tumor suppressor in SCLC cells; therefore, the Bmi1/WWOX pathway could be a new candidate for a new therapeutic approach for SCLC.

The biology of cancer testis antigens: putative function, regulation and therapeutic potential

Cancer testis antigens (CTA) are a large family of tumor-associated antigens expressed in human tumors of different histological origin, but not in normal tissues except for testis and placenta. This tumor-restricted pattern of expression, together with their strong in vivo immunogenicity, identified CTA as ideal targets for tumor-specific immunotherapeutic approaches, and prompted the development of several clinical trials of CTA-based vaccine therapy. Driven by this practical clinical interest, a more detailed characterization of CTA biology has been recently undertaken. So far, at least 70 families of CTA, globally accounting for about 140 members, have been identified. Most of these CTA are expressed during spermatogenesis, but their function is still largely unknown. Epigenetic events, particularly DNA methylation, appear to be the primary mechanism regulating CTA expression in both normal and transformed cells, as well as in cancer stem cells. In view of the growing interest in CTA biology, the aim of this review is to provide the most recent information on their expression, regulation and function, together with a brief summary of the major clinical trials involving CTA as therapeutic agents. The pharmacologic modulation of CTA expression profiles on neoplastic cells by DNA hypomethylating drugs will also be discussed as a feasible approach to design new combination therapies potentially able to improve the clinical efficacy of currently adopted CTA-based immunotherapeutic regimens in cancer patients.

A critical re-appraisal of BRCA1 methylation studies in ovarian cancer

A central challenge facing gynecologic oncology is achieving personalized care in ovarian cancer treatment. The current ovarian cancer classification scheme distinguishes tumors based on histopathologic subtype, grade, and surgical stage. Recent molecular investigations have highlighted distinguishing genetic features of certain tumors within a given category, and given the rapid pace of technologic advancement combined with plummeting costs for complete genomic sequencing this classification will markedly improve. Clinical studies have begun to explore the influence of currently known distinctions on the natural history of the disease, most recently with particular attention to the BRCA1 status of tumors. Mutations in the BRCA1 gene have long been known to increase a woman's risk of developing ovarian cancer. As has been shown, BRCA1-associated ovarian cancers may be associated with characteristic differences in therapeutic response and overall survival, and further defining these subsets may become instrumental in clinical decision-making. Therefore, given the eightfold difference (5-40%) in reported frequency of BRCA1 inactivation by methylation in the pioneering studies in the field, a critical re-appraisal of the literature, techniques, samples used, and interpretations of BRCA1 inactivation is warranted along with a review of the more recent and comprehensive molecular studies.

Clinical and molecular responses in lung cancer patients receiving Romidepsin

PURPOSE

Our preclinical experiments indicated that Romidepsin (Depsipeptide FK228; DP) mediates growth arrest and apoptosis in cultured lung cancer cells. A phase II trial was done to examine clinical and molecular responses mediated by this histone deacetylase inhibitor in lung cancer patients.

EXPERIMENTAL DESIGN

Nineteen patients with neoplasms refractory to standard therapy received 4-h DP infusions (17.8 mg/m(2)) on days 1 and 7 of a 21-day cycle. Each full course of therapy consisted of two identical 21-day cycles. Plasma DP levels were evaluated by liquid chromatography-mass spectrometry techniques. A variety of molecular end points were assessed in tumor biopsies via immunohistochemistry techniques. Long oligo arrays were used to examine gene expression profiles in laser-captured tumor cells before and after DP exposure, relative to lung cancer cells and adjacent normal bronchial epithelia from patients undergoing pulmonary resections.

RESULTS

Nineteen patients were evaluable for toxicity assessment; 18 were evaluable for treatment response. Myelosuppression was dose limiting in one individual. No significant cardiac toxicities were observed. Maximum steady-state plasma DP concentrations ranged from 384 to 1,114 ng/mL. No objective responses were observed. Transient stabilization of disease was noted in nine patients. DP enhanced acetylation of histone H4, increased p21 expression in lung cancer cells, and seemed to shift global gene expression profiles in these cells toward those detected in normal bronchial epithelia.

CONCLUSION

Although exhibiting minimal clinical efficacy at this dose and schedule, DP mediates biological effects that may warrant further evaluation of this histone deacetylase inhibitor in combination with novel-targeted agents in lung cancer patients.

SmgGDS regulates cell proliferation, migration, and NF-kappaB transcriptional activity in non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is promoted by the increased activities of several small GTPases, including K-Ras4B, Rap1A, Rap1B, RhoC, and Rac1. SmgGDS is an unusual guanine nucleotide exchange factor that activates many of these small GTPases, and thus may promote NSCLC development or progression. We report here that SmgGDS protein levels are elevated in NSCLC tumors, compared with normal lung tissue from the same patients or from individuals without cancer. To characterize SmgGDS functions in NSCLC, we tested the effects of silencing SmgGDS expression by transfecting cultured NSCLC cells with SmgGDS small interfering RNA (siRNA). Cells with silenced SmgGDS expression form fewer colonies in soft agar, do not proliferate in culture due to an arrest in G(1) phase, and exhibit disrupted myosin organization and reduced cell migration. The transcriptional activity of NF-kappaB in NSCLC cells is diminished by transfecting the cells with SmgGDS siRNA, and enhanced by transfecting the cells with a cDNA encoding SmgGDS. Because RhoA is a major substrate for SmgGDS, we investigated whether diminished RhoA expression mimics the effects of diminished SmgGDS expression. Silencing RhoA expression with RhoA siRNA disrupts myosin organization, but only moderately decreases cell proliferation and does not inhibit migration. Our finding that the aggressive NSCLC phenotype is more effectively suppressed by silencing SmgGDS than by silencing RhoA is consistent with the ability of SmgGDS to regulate multiple small GTPases in addition to RhoA. These results demonstrate that SmgGDS promotes the malignant NSCLC phenotype and is an intriguing therapeutic target in NSCLC.

Cigarette smoke induces demethylation of prometastatic oncogene synuclein-gamma in lung cancer cells by downregulation of DNMT3B

The prometastatic oncogene synuclein-gamma (SNCG) is not expressed in normal lung tissues, but it is highly expressed in lung tumors. Here, we show that cigarette smoke extract (CSE) has strong inducing effects on SNCG gene expression in A549 lung cancer cells through demethylation of SNCG CpG island. CSE treatment also augments the invasive capacity of A549 cells in an SNCG-dependent manner. To elucidate the mechanisms underlying the demethylating effects of CSE, we examined expression levels of DNA methyltransferases (DNMTs), 1, 3A and 3B in CSE-treated cells. We show that the mRNA expression of DNMT3B is specifically downregulated by CSE with a kinetics concurrent to SNCG reexpression. Utilizing siRNA to knockdown DNMT3B expression, we show that inhibition of DNMT3B directly increases SNCG mRNA expression. We further show that exogenous overexpression of DNMT3B in an SNCG-positive lung cancer cell line H292 suppresses SNCG mRNA and protein expression and induces de novo methylation of SNCG CpG island, whereas overexpression of DNMT1 or DNMT3A has no effects. Taken together, these new findings demonstrate that tobacco exposure induces the abnormal expression of SNCG in lung cancer cells through downregulation of DNMT3B. This work sheds light on the molecular understanding of demethylation of this oncogene during cancer progression.

Epigenetic drugs as pleiotropic agents in cancer treatment: biomolecular aspects and clinical applications

In the last three decades huge efforts have been made to characterize genetic defects responsible for cancer development and progression, leading to the comprehensive identification of distinct cellular pathways affected by the alteration of specific genes. Despite the undoubtable role of genetic mechanisms in triggering neoplastic cell transformation, epigenetic modifications (i.e., heritable changes of gene expression that do not derive from alterations of the nucleotide sequence of DNA) are rapidly emerging as frequent alterations that often occur in the early phases of tumorigenesis and that play an important role in tumor development and progression. Epigenetic alterations, such as modifications in DNA methylation patterns and post-translational modifications of histone tails, behave extremely different from genetic modifications, being readily revertable by "epigenetic drugs" such as inhibitors of DNA methyl transferases and inhibitors of histone deacetylases. Since epigenetic alterations in cancer cells affect virtually all cellular pathways that have been associated to tumorigenesis, it is not surprising that epigenetic drugs display pleiotropic activities, being able to concomitantly restore the defective expression of genes involved in cell cycle control, apoptosis, cell signaling, tumor cell invasion and metastasis, angiogenesis and immune recognition. Prompted by this emerging clinical relevance of epigenetic drugs, this review will focus on the large amount of available data, deriving both from in vitro experimentations and in vivo pre-clinical and clinical studies, which clearly indicate epigenetic drugs as effective modifiers of cancer phenotype and as positive regulators of tumor cell biology with a relevant therapeutic potential in cancer patients.

Apoptosis induced by depsipeptide FK228 coincides with inhibition of survival signaling in lung cancer cells

BACKGROUND

Whereas histone deacetylase inhibitors are known to modulate chromatin structure, the precise mechanisms by which these novel agents induce apoptosis in cancer cells remain unknown. Previously we reported that depsipeptide FK228 depletes epidermal growth factor receptor (EGFR), erbB2, and Raf-1 kinases in non-small cell lung cancer cells. In the present study we sought to further define the mechanisms by which FK228 modulates oncoprotein signaling and to ascertain whether altered signal transduction contributes to FK228-mediated apoptosis in lung cancer cells.

METHODS

Cultured non-small cell lung cancer cells were treated with FK228 alone or FK228 with a variety of kinase inhibitors. Proliferation and apoptosis mediated by drug exposure were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium, and Apo-BrdU techniques. Western blot and kinase assays were used to evaluate EGFR-related signal transduction pathways. Lung cancer cells were transduced with adenoviral vectors expressing activated AKT or mitogen-activated protein kinase kinase (MEK) 1 or beta-galactosidase to determine whether constitutive activation of mitogen-activated protein kinase signaling could abrogate FK228-mediated apoptosis.

RESULTS

FK228 treatment induced time-dependent apoptosis in lung cancer cells expressing wild-type or mutant EGFR. FK228 inhibited a variety of EGFR-related pathways including Src, RAF-MEK-extracellular signal-regulated kinase (ERK) 1/2 and phosphatidyl inositol-3 kinase (PI3K)/AKT, resulting in down-regulation of Bcl-2 and Bcl-xL and up-regulation of Bax. The kinase inhibitors AG1478, AG825, PD98059, and LY294002 markedly enhanced FK228-induced apoptosis in lung cancer cells. Coincident with inhibition of ERK1/2 and PI3K/AKT survival pathways, FK228 enhanced p38 and stress-activated protein kinase/c-Jun NH2-terminal kinase stress signaling. Constitutive expression of MEK1 but not AKT markedly reduced FK228-mediated apoptosis in lung cancer cells.

CONCLUSIONS

FK228 inhibits EGFR expression and modulates a variety of downstream mediators regulating proliferation and stress responses in lung cancer cells. These data highlight the significance of MEK signaling with respect to FK228-mediated apoptosis and support evaluation of histone deacetylase inhibitors in conjunction with agents specifically targeting mitogen-activated protein kinases in patients with lung cancer.

Utilization of chromatin remodeling agents for lung cancer therapy

Lung cancer is a disease with enormous global medical and economic impact that remains refractory to conventional treatment modalities. Recent insights regarding mechanisms pertaining to epigenetic regulation of gene expression during malignant transformation, together with the identification of agents that modulate chromatin structure provide new opportunities for the treatment and prevention of this lethal disease.

Rapid and profound potentiation of Apo2L/TRAIL-mediated cytotoxicity and apoptosis in thoracic cancer cells by the histone deacetylase inhibitor Trichostatin A: the essential role of the mitochondria-mediated caspase activation cascade

Apo2L/TRAIL is actively investigated as a novel targeted agent to directly induce apoptosis of susceptible cancer cells. Apo2L/TRAIL-refractory cells can be sensitized to the cytotoxic effect of this ligand by cytotoxic chemotherapeutics. The aim of this study was to evaluate the in vitro tumoricidal activity of the Apo2L/TRAIL + Trichostatin A in cultured thoracic cancer cells and to elucidate the molecular basis of the synergistic cytotoxicity of this combination. Concurrent exposure of cultured cancer cells to sublethal concentrations of Apo2L/TRAIL and Trichostatin A resulted in profound enhancement of Apo2L/TRAIL-mediated cytotoxicity in all cell lines regardless of their intrinsic susceptibility to this ligand. This combination was not toxic to primary normal cells. While Apo2L/TRAIL alone or Trichostatin A alone mediated < 20% cell death, 60 to 90% of cancer cells were apoptotic following treatment with TSA + Apo2L/TRAIL combinations. Complete translocation of Bax from the cytosol to the mitochondria compartment was mainly observed in combination-treated cells and this was correlated with robust elevation of caspase 9 proteolytic activity indicative of activation of the mitochondria apoptogenic effect. Profound TSA + Apo2L/TRAIL-mediated cytotoxicity and apoptosis were completely abrogated by either Bcl2 over-expression or by the selective caspase 9 inhibitor, highlighting the essential role of mitochondria-dependent apoptosis signaling cascade in this process. Moreover, increased caspase 8 activity observed in cells treated with the TSA + Apo2L/TRAIL combination was completely suppressed by Bcl-2 over-expression or by the selective caspase 9 inhibitor indicating that the elevated caspase 8 activity in combination-treated cells was secondary to a mitochondria-mediated amplification feedback loop of caspase activation. These finding form the basis for further development of HDAC inhibitors + Apo2L/TRAIL combination as novel targeted therapy for thoracic malignancies.

Targeting the epigenome for the treatment of thoracic malignancies

Despite considerable efforts to improve the diagnosis and treatment of lung cancer, this disease remains the leading cause of cancer-related mortality worldwide. Recent elucidation of epigenetic regulation of gene expression during malignant transformation, together with the identification of agents that modulate DNA methylation and histone acetylation, provide new opportunities for the treatment and prevention of lung cancer via chromatin remodeling mechanisms. Further analysis of molecular response in tumor tissues following exposure to chromatin remodeling agents may enable us to identify novel mechanisms pertaining to lung cancer epigenetics, and design more efficacious regimens.

Dynamic transcriptional regulatory complexes including BORIS, CTCF and Sp1 modulate NY-ESO-1 expression in lung cancer cells

Previously, we reported that the paralogous zinc-finger proteins--CTCF and brother of the regulator of imprinted sites (BORIS), directly contribute to transcriptional regulation of NY-ESO-1 in lung cancer cells. To further examine mechanisms that mediate expression of this cancer-testis gene, we performed software-guided analysis of the NY-ESO-1 promoter region, which revealed several potential Sp1-binding motifs. Sequential 5-aza-2'deoxycytidine/depsipeptide FK228 treatment markedly induced BORIS expression and enhanced nuclear translocation of Sp1 in lung cancer cells. Transient transfection assays using promoter-reporter constructs, as well as gel-shift and chromatin immunoprecipitation experiments revealed that NY-ESO-1 promoter activity coincided with occupancy of the proximal Sp1-binding site in lung cancer cells. Mutations within the Sp1 recognition sequence specifically eliminated binding of Sp1 to this motif in vitro, and markedly diminished NY-ESO-1 promoter activity in vivo. siRNA-mediated inhibition of Sp1 expression decreased NY-ESO-1 promoter activity, whereas knock down of CTCF expression augmented NY-ESO-1 transcription in lung cancer cells. Co-immunoprecipitation experiments indicated that Sp1 physically interacts with BORIS but not with CTCF in vivo. Collectively, these findings suggest that BORIS recruits Sp1 to mediate de-repression of NY-ESO-1 during pulmonary carcinogenesis.

Phase I study of decitabine-mediated gene expression in patients with cancers involving the lungs, esophagus, or pleura

PURPOSE

The DNA methylation paradox, manifested as derepression of cancer-testis antigens, and silencing of tumor suppressors during malignant transformation, provides the rationale for the utilization of chromatin remodeling agents for cancer therapy. A phase I trial was done to examine pharmacokinetics, toxicities, and gene expression mediated by 5-aza-2'-deoxycytidine (DAC) in patients with thoracic malignancies.

EXPERIMENTAL DESIGN

Thirty-five patients with cancers refractory to standard therapy received continuous 72-hour DAC infusions using a phase I dose-escalation schema. Each full course of therapy consisted of two identical 35-day cycles. Plasma DAC levels were evaluated by liquid chromatography-mass spectrometry techniques. Quantitative reverse transcription-PCR, methylation-specific PCR, and immunohistochemical techniques were used to evaluate NY-ESO-1, MAGE-3, and p16 expression in tumor biopsies. Long oligonucleotide arrays were used to evaluate gene expression profiles in laser-captured tumor cells before and after DAC exposure.

RESULTS

Thirty-five patients were evaluable for toxicities; 25 were evaluable for treatment response. Myelosuppression constituted dose-limiting toxicity. The maximum tolerated dose of DAC was 60 to 75 mg/m(2) depending on the number of prior cytotoxic chemotherapy regimens. No objective responses were observed. Plasma DAC concentrations approximated thresholds for gene induction in cultured cancer cells. Target gene induction was observed in 36% of patients. Posttreatment antibodies to NY-ESO-1 were detected in three patients exhibiting NY-ESO-1 induction in their tumor tissues. Complex, heterogeneous gene expression profiles were observed in pretreatment and posttreatment tissues.

CONCLUSION

Prolonged DAC infusions can modulate gene expression in primary thoracic malignancies. These findings support further evaluation of DNA-demethylating agents alone or in combination with other regimens targeting induced gene products for the treatment of these neoplasms.

Epigenetics of lung cancer

Epigenetics is the study of heritable changes in gene expression that occur without changes in DNA sequence. It has a role in determining when and where a gene is expressed during development. Perhaps the most well known epigenetic mechanism is DNA methylation whereby cytosines at position 5 in CpG dinucleotides are methylated. Histone modification is another form of epigenetic control, which is quite complex and diverse. Histones and DNA make up the nucleosome which is the structural unit of chromatin which are involved in packaging DNA. Apart from the crucial role epigenetics plays in embryonic development, transcription, chromatin structure, X chromosome inactivation and genomic imprinting, its role in an increasing number of human diseases is more and more recognized. These diseases include cancer, and lung cancer in particular has been increasingly studied for the potential biological role of epigenetic changes with the promise of better and novel diagnostic and therapeutic tools.

Pharmacologic inhibition of epigenetic modifications, coupled with gene expression profiling, reveals novel targets of aberrant DNA methylation and histone deacetylation in lung cancer

Lung cancer is the leading cause of cancer-related deaths in the United States due, in large part, to the lack of early detection methods. Lung cancer arises from a complex series of genetic and epigenetic changes leading to uncontrolled cell growth and metastasis. Unlike genetic changes, epigenetic changes, such as DNA methylation and histone acetylation, are reversible with currently available pharmaceuticals and are early events in lung tumorigenesis detectable by non-invasive methods. In order to better understand how epigenetic changes contribute to lung cancer, and to identify new disease biomarkers, we combined pharmacologic inhibition of DNA methylation and histone deacetylation in non-small cell lung cancer (NSCLC) cell lines, with genome-wide expression profiling. Of the more than 200 genes upregulated by these treatments, three of these, neuronatin, metallothionein 3 and cystatin E/M, were frequently hypermethylated and transcriptionally downregulated in NSCLC cell lines and tumors. Interestingly, four other genes, cylindromatosis, CD9, activating transcription factor 3 and oxytocin receptor, were dominantly regulated by histone deacetylation and were also frequently downregulated in lung tumors. The majority of these genes also suppressed NSCLC growth in culture when ectopically expressed. This study therefore reveals new putative NSCLC growth regulatory genes and epigenetic disease biomarkers that may enhance early detection strategies and serve as therapeutic targets.

Valproic acid, an antiepileptic drug with histone deacetylase inhibitory activity, potentiates the cytotoxic effect of Apo2L/TRAIL on cultured thoracic cancer cells through mitochondria-dependent caspase activation

Inhibitors of histone deacetylases have been shown to enhance the sensitivity of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand TRAIL-mediated cytotoxicity. Valproic acid (VA), a commonly used antiepileptic agent whose pharmacokinetics and toxicity profiles are well described, is a histone deacetylase inhibitor. This project aims to evaluate if VA can potentiate Apo2L/TRAIL-mediated cytotoxicity in cultured thoracic cancer cells and to elucidate the underlying molecular mechanism responsible for this effect. VA sensitized cultured thoracic cancer cells to Apo2L/TRAIL, as indicated by a 4-fold to a >20-fold reduction of Apo2L/TRAIL IC50 values in combination-treated cells. Although VA (0.5-5 mM) or Apo2L/TRAIL (20 ng/ml) induced less than 20% cell death, VA + Apo2L/TRAIL combinations caused 60% to 90% apoptosis of cancer cells. Moreover, substantial activation of caspases 8, 9, and 3, which was observed only in cells treated with the drug combination, was completely suppressed by Bcl2 overexpression or by the caspase 9 inhibitor. Both the caspase 9 inhibitor and Bcl2 completely abrogated the substantial cytotoxicity and apoptosis induced by this combination, thus highlighting the pivotal role of the type II pathway in this process. These findings provide a rationale for the development of VA and Apo2L/TRAIL combination as a novel molecular therapeutic for thoracic cancers.

Potentiation of the anticancer effect of valproic acid, an antiepileptic agent with histone deacetylase inhibitory activity, by the kinase inhibitor Staurosporine or its clinically relevant analogue UCN-01

Histone deacetylase inhibitors (HDACIs) are novel anticancer agents with potent cytotoxicity against a wide range of malignancies. We have previously demonstrated that either Calphostin C (CC) (a protein kinase C (PKC) inhibitor) or Parthenolide (an NF-kappaB inhibitor) abrogates HDACI-induced transcriptional activation of NF-kappaB and p21, which is associated with profound potentiation of HDACI-mediated induction of apoptosis. Valproic acid (VA), a commonly used antiepileptic agent, has recently been shown to be an HDACI. This study was aimed to evaluate the anticancer property of VA in thoracic cancer cells and the development of clinically relevant strategies to enhance VA-mediated induction of apoptosis using kinase inhibitors Staurosporine (STP) or its analogue UCN-01. Treating cultured thoracic cancer cells with VA (0.62-10.0 mM) resulted in significant cell line- and dose-dependent growth inhibition (IC(50) values: 4.1-6.0 mM) and cell cycle arrest at G1/S checkpoint with profound accumulation of cells at G0/G1 phase but little induction of apoptosis. Valproic acid, being an HDACI, caused significant dose-dependent accumulation of hyperacetylated histones, following 24 h of treatment. Valproic acid-mediated 5-20-fold upregulation of transcriptional activity of NF-kappaB was substantially (50-90%) suppressed by cotreatment with CC, STP or UCN-01. Whereas minimal death (<20%) was observed in cells treated with either VA (1.0 or 5.0 mM) alone or kinase inhibitors alone, 60-90% of cells underwent apoptosis following exposure to combinations of VA+kinase inhibitors. Kinase inhibitor-mediated suppression of NF-kappaB transcriptional activity played an important role in sensitising cancer cells to VA as direct inhibition of NF-kappaB by Parthenolide drastically synergised with VA to induce apoptosis (VA+Parthenolide: 60-90% compared to <20% following single-drug treatments). In conclusion, VA, a well-known antiepileptic drug, has mild growth-inhibitory activity on cultured cancer cells. The weak VA-mediated induction of apoptosis of thoracic cancer cells can be profoundly enhanced either by Parthenolide, a pharmacologic inhibitor of NF-kappaB, or by UCN-01 a kinase inhibitor that has already undergone phase I clinical development. Combinations of VA with either a PKC inhibitor or an NF-kappaB inhibitor are promising novel molecularly targeted therapeutics for thoracic cancers.

De novo induction of a cancer/testis antigen by 5-aza-2'-deoxycytidine augments adoptive immunotherapy in a murine tumor model

Recent studies suggest that immunotherapy targeting specific tumor-associated antigens (TAAs) may be beneficial in cancer patients. However, most of these TAAs are tumor type specific and heterogeneous among patients, thus limiting their applications. Here, we describe the de novo induction of a cancer/testis antigen (CTA) for immunotherapy of tumors of various histologies. The murine CTA P1A, normally expressed only in a few tumor lines, could be induced de novo in all P1A-negative cancer lines of eight histologic origins in vitro and in various murine xenografts by systemic administration of 5-aza-2'-deoxycytidine. The induction of P1A expression correlated strongly with demethylation of the CpG island in the promoter region of this gene. The induced antigen was processed and presented properly for recognition by H-2L(d)-restricted P1A-specific CTLs. The combination of a demethylating agent and adoptive transfer of P1A-specific CTL effectively treated lung metastases in syngeneic mice challenged with P1A-negative 4T1 mammary carcinoma cells. These data show a novel strategy of combined chemoimmunotherapy of cancer targeting a CTA induced de novo in a broad range of tumor histologies, and support further evaluation of chromatin-remodeling agents for human cancer therapy.

Reciprocal binding of CTCF and BORIS to the NY-ESO-1 promoter coincides with derepression of this cancer-testis gene in lung cancer cells

Regulatory sequences recognized by the unique pair of paralogous factors, CTCF and BORIS, have been implicated in epigenetic regulation of imprinting and X chromosome inactivation. Lung cancers exhibit genome-wide demethylation associated with derepression of a specific class of genes encoding cancer-testis (CT) antigens such as NY-ESO-1. CT genes are normally expressed in BORIS-positive male germ cells deficient in CTCF and meCpG contents, but are strictly silenced in somatic cells. The present study was undertaken to ascertain if aberrant activation of BORIS contributes to derepression of NY-ESO-1 during pulmonary carcinogenesis. Preliminary experiments indicated that NY-ESO-1 expression coincided with derepression of BORIS in cultured lung cancer cells. Quantitative reverse transcription-PCR analysis revealed robust, coincident induction of BORIS and NY-ESO-1 expression in lung cancer cells, but not normal human bronchial epithelial cells following 5-aza-2'-deoxycytidine (5-azadC), Depsipeptide FK228 (DP), or sequential 5-azadC/DP exposure under clinically relevant conditions. Bisulfite sequencing, methylation-specific PCR, and chromatin immunoprecipitation (ChIP) experiments showed that induction of BORIS coincided with direct modulation of chromatin structure within a CpG island in the 5'-flanking noncoding region of this gene. Cotransfection experiments using promoter-reporter constructs confirmed that BORIS modulates NY-ESO-1 expression in lung cancer cells. Gel shift and ChIP experiments revealed a novel CTCF/BORIS-binding site in the NY-ESO-1 promoter, which unlike such sites in the H19-imprinting control region and X chromosome, is insensitive to CpG methylation in vitro. In vivo occupancy of this site by CTCF was associated with silencing of the NY-ESO-1 promoter, whereas switching from CTCF to BORIS occupancy coincided with derepression of NY-ESO-1. Collectively, these data indicate that reciprocal binding of CTCF and BORIS to the NY-ESO-1 promoter mediates epigenetic regulation of this CT gene in lung cancer cells, and suggest that induction of BORIS may be a novel strategy to augment immunogenicity of pulmonary carcinomas.