Promoter methylation and silencing of the retinoic acid receptor-beta gene in lung carcinomas

Fast proliferating and slowly migrating non-small cell lung cancer cells are vulnerable to decitabine and retinoic acid combinatorial treatment

Non-small cell lung cancer (NSCLC) patients are often elderly or unfit and thus cannot tolerate standard aggressive therapy regimes. In our study, we test the efficacy of the DNA-hypomethylating agent decitabine (DAC) in combination with all-trans retinoic acid (ATRA), which has been shown to possess little systemic adverse effects. Screening a broad panel of 56 NSCLC cell lines uncovered a decrease in cell viability after the combination treatment in 77% of the cell lines. Transcriptomics, proteomics, proliferation and migration profiling revealed that fast proliferating and slowly migrating cell lines were more sensitive to the drug combination. The comparison of mutational profiles found oncogenic KRAS mutations only in sensitive cells. Additionally, different cell lines showed a heterogeneous gene expression response to the treatment pointing to diverse mechanisms of action. Silencing KRAS, RIG-I or RARB partially reversed the sensitivity of KRAS-mutant NCI-H460 cells. To study resistance, we generated two NCI-H460 cell populations resistant to ATRA and DAC, which migrated faster and proliferated slower than the parental sensitive cells and showed signs of senescence. In summary, this comprehensive dataset uncovers a broad sensitivity of NSCLC cells to the combinatorial treatment with DAC and ATRA and indicates that migration and proliferation capacities correlate with and could thus serve as determinants for drug sensitivity in NSCLC.

The Contribution of Hippocampal All-Trans Retinoic Acid (ATRA) Deficiency to Alzheimer's Disease: A Narrative Overview of ATRA-Dependent Gene Expression in Post-Mortem Hippocampal Tissue

There is accumulating evidence that vitamin A (VA) deficiency contributes to the pathogenesis and progression of Alzheimer's disease (AD). All-trans retinoic acid (ATRA), a metabolite of VA in the brain, serves distinct roles in the human hippocampus. Agonists of retinoic acid receptors (RAR), including ATRA, promote activation of the non-amyloidogenic pathway by enhancing expression of α-secretases, providing a mechanistic basis for delaying/preventing amyloid beta (Aβ) toxicity. However, whether ATRA is actually deficient in the hippocampi of patients with AD is not clear. Here, using a publicly available human transcriptomic dataset, we evaluated the extent to which ATRA-sensitive genes are dysregulated in hippocampal tissue from post-mortem AD brains, relative to age-matched controls. Consistent with ATRA deficiency, we found significant dysregulation of many ATRA-sensitive genes and significant upregulation of RAR co-repressors, supporting the idea of transcriptional repression of ATRA-mediated signaling. Consistent with oxidative stress and neuroinflammation, Nrf2 and NfkB transcripts were upregulated, respectively. Interestingly, transcriptional targets of Nrf2 were not upregulated, accompanied by upregulation of several histone deacetylases. Overall, our investigation of ATRA-sensitive genes in the human hippocampus bolsters the scientific premise of ATRA depletion in AD and that epigenetic factors should be considered and addressed as part of VA supplementation.

DNA and histone modifications as potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine

Lung cancer has a very high mortality in females and males. Most (~ 85%) of lung cancers are non-small cell lung cancers (NSCLC). When lung cancer is diagnosed, most of them have either local or distant metastasis, with a poor prognosis. In order to achieve better outcomes, it is imperative to identify the molecular signature based on genetic and epigenetic variations for different NSCLC subgroups. We hypothesize that DNA and histone modifications play significant roles in the framework of predictive, preventive, and personalized medicine (PPPM; 3P medicine). Epigenetics has a significant impact on tumorigenicity, tumor heterogeneity, and tumor resistance to chemotherapy, targeted therapy, and immunotherapy. An increasing interest is that epigenomic regulation is recognized as a potential treatment option for NSCLC. Most attention has been paid to the epigenetic alteration patterns of DNA and histones. This article aims to review the roles DNA and histone modifications play in tumorigenesis, early detection and diagnosis, and advancements and therapies of NSCLC, and also explore the connection between DNA and histone modifications and PPPM, which may provide an important contribution to improve the prognosis of NSCLC. We found that the success of targeting DNA and histone modifications is limited in the clinic, and how to combine the therapies to improve patient outcomes is necessary in further studies, especially for predictive diagnostics, targeted prevention, and personalization of medical services in the 3P medicine approach. It is concluded that DNA and histone modifications are potent diagnostic and therapeutic targets to advance non-small cell lung cancer management from the perspective of 3P medicine.

Epigenetic Alterations and Inflammation as Emerging Use for the Advancement of Treatment in Non-Small Cell Lung Cancer

Lung cancer remains one of the most common malignancies in the world. Nowadays, the most common lung cancer is non-small cell lung cancer (NSCLC), namely, adenocarcinoma, squamous cell carcinoma, and large cell lung carcinoma. Epigenetic alterations that refer to DNA methylation, histone modifications, and noncoding RNA expression, are now suggested to drive the genesis and development of NSCLC. Additionally, inflammation-related tumorigenesis also plays a vital role in cancer research and efforts have been attempted to reverse such condition. During the occurrence and development of inflammatory diseases, the immune component of inflammation may cause epigenetic changes, but it is not always certain whether the immune component itself or the stimulated host cells cause epigenetic changes. Moreover, the links between epigenetic alterations and cancer-related inflammation and their influences on the human cancer are not clear so far. Therefore, the connection between epigenetic drivers, inflammation, and NSCLC will be summarized. Investigation on such topic is most likely to shed light on the molecular and immunological mechanisms of epigenetic and inflammatory factors and promote the application of epigenetics in the innovative diagnostic and therapeutic strategies for NSCLC.

DNA Methylation in Lung Cancer: Mechanisms and Associations with Histological Subtypes, Molecular Alterations, and Major Epidemiological Factors

Lung cancer is the major leading cause of cancer-related mortality worldwide. Multiple epigenetic factors-in particular, DNA methylation-have been associated with the development of lung cancer. In this review, we summarize the current knowledge on DNA methylation alterations in lung tumorigenesis, as well as their associations with different histological subtypes, common cancer driver gene mutations (e.g., KRAS, EGFR, and TP53), and major epidemiological risk factors (e.g., sex, smoking status, race/ethnicity). Understanding the mechanisms of DNA methylation regulation and their associations with various risk factors can provide further insights into carcinogenesis, and create future avenues for prevention and personalized treatments. In addition, we also highlight outstanding questions regarding DNA methylation in lung cancer to be elucidated in future studies.

Targeting DNA methyltransferases in non-small-cell lung cancer

Despite the advances in treatment using chemotherapy or targeted therapies, due to static survival rates, non-small cell lung cancer (NSCLC) is the major cause of cancer-related deaths worldwide. Epigenetic-based therapies have been developed for NSCLC by targeting DNA methyltransferases (DNMTs) and histone-modifying enzymes. However, treatment using single epigenetic agents on solid tumours has been inadequate; whereas, treatment with a combination of DNMTs inhibitors with chemotherapy and immunotherapy has shown great promise. Dietary sources of phytochemicals could also inhibit DNMTs and cancer stem cells, representing a novel and promising way to prevent and treat cancer. Herein, we will discuss the different DNMTs, DNA methylation profiling in NSCLC as well as current demethylating agents in ongoing clinical trials. Therefore, providing a concise overview of future developments in the field of epigenetic therapy in NSCLC.

Comparative sequence analysis across Brassicaceae, regulatory diversity in KCS5 and KCS6 homologs from Arabidopsis thaliana and Brassica juncea, and intronic fragment as a negative transcriptional regulator

Intra- and epicuticular-waxes primarily comprising of very long chain aliphatic lipid (VLCFA), terpenoids and secondary metabolites such as sterol and flavonoids played a major role in successful colonization of terrestrial ecosystem by aquatic plants and are thus considered as a key evolutionary innovation. The key rate limiting step of Fatty Acid (FA) biosynthesis of condensation/elongation are catalyzed by the enzyme, β-ketoacyl coenzyme A synthase (KCS), part of FAE (Fatty Acid Elongase) complex. KCS6 has been shown to be responsible for elongation using C22 fatty acid as substrate and is considered essential for synthesis of VLCFA for cuticular waxes. Earlier studies have established KCS5 as a close paralog of KCS6 in Arabidopsis thaliana, albeit with non-redundant function. We subsequently established segmental duplication responsible for origin of KCS6-KCS5 paralogy which is exclusive to Brassicaceae. In the present study, we aim to understand impact of duplication on regulatory diversification and evolution, through sequence and functional analysis of cis-regulatory element of KCS5 and KCS6. High level of sequence variation leading to conservation of only the proximal end of the promoter corresponding to the core promoter was observed among Brassicaceae members; such high diversity was also revealed when sliding window analysis revealed only two to three phylogenetic footprints. Profiling of transcription factor binding sites (TFBS) across Brassicaceae shows presence of light, hormone and stress responsive motifs; a few motifs involved in tissue specific expression (Skn-1; endosperm) were also detected. Functional characterization using transcriptional fusion constructs revealed regulatory diversification when promoter activity of homologs from A. thaliana and Brassica juncea were compared. When subjected to 5-Azacytidine, altered promoter activity was observed, implying role of DNA methylation in transcriptional regulation. Finally, investigation of the role of an 87 bp fragment from first intron that is retained in a splice variant, revealed it to be a transcriptional repressor. This is a first report on comparative sequence and functional analysis of transcriptional regulation of KCS5 and KCS6; further studies are required before manipulation of cuticular waxes as a strategy for mitigating stress.

Tumor evolution in epidermal growth factor receptor mutated non-small cell lung cancer

As the incidence of cancer increases worldwide there is an unmet need to understand cancer evolution to improve patient outcomes. Our growing knowledge of cancer cells' clonal expansion, heterogeneity, adaptation, and relationships within the tumor immune compartment and with the tumor microenvironment has made clear that cancer is a disease that benefits from heterogeneity and evolution. This review outlines recent knowledge of non-small cell lung cancer (NSCLC) pathogenesis and tumor progression from an evolutionary standpoint, focused on the role of oncogenic driver mutations as epidermal growth factor receptor (EGFR). Understanding lung cancer evolution during tumor development, growth, and under treatment pressures is crucial to improve therapeutic interventions and patient outcomes.

The Current Understanding Of Asbestos-Induced Epigenetic Changes Associated With Lung Cancer

Asbestos is a naturally occurring mineral consisting of extremely fine fibres that can become trapped in the lungs after inhalation. Occupational and environmental exposures to asbestos are linked to development of lung cancer and malignant mesothelioma, a cancer of the lining surrounding the lung. This review discusses the factors that are making asbestos-induced lung cancer a continuing problem, including the extensive historic use of asbestos and decades long latency between exposure and disease development. Genomic mutations of DNA nucleotides and gene rearrangements driving lung cancer are well-studied, with biomarkers and targeted therapies already in clinical use for some of these mutations. The genes involved in these mutation biomarkers and targeted therapies are also involved in epigenetic mechanisms and are discussed in this review as it is hoped that identification of epigenetic aberrations in these genes will enable the same gene biomarkers and targeted therapies to be used. Currently, understanding of how asbestos fibres trapped in the lungs leads to epigenetic changes and lung cancer is incomplete. It has been shown that oxidoreduction reactions on fibre surfaces generate reactive oxygen species (ROS) which in turn damage DNA, leading to genetic and epigenetic alterations that reduce the activity of tumour suppressor genes. Epigenetic DNA methylation changes associated with lung cancer are summarised in this review, and some of these changes will be due to asbestos exposure. So far, little research has been carried out to separate the asbestos driven epigenetic changes from those due to non-asbestos causes of lung cancer. Asbestos-associated lung cancers exhibit less methylation variability than lung cancers in general, and in a large proportion of samples variability has been found to be restricted to promoter regions. Epigenetic aberrations in cancer are proving to be promising biomarkers for diagnosing cancers. It is hoped that further understanding of epigenetic changes in lung cancer can result in useful asbestos-associated lung cancer biomarkers to guide treatment. Research is ongoing into the detection of lung cancer epigenetic alterations using non-invasive samples of blood and sputum. These efforts hold the promise of non-invasive cancer diagnosis in the future. Efforts to reverse epigenetic aberrations in lung cancer by epigenetic therapies are ongoing but have not yet yielded success.

Current Landscape of Epigenetics in Lung Cancer: Focus on the Mechanism and Application

Lung cancer is the leading cause of cancer-related mortality worldwide. Tumorigenesis involves a multistep process resulting from the interactions of genetic, epigenetic, and environmental factors. Genome-wide association studies and sequencing studies have identified many epigenetic alterations associated with the development of lung cancer. Epigenetic mechanisms, mainly including DNA methylation, histone modification, and noncoding RNAs (ncRNAs), are heritable and reversible modifications that are involved in some important biological processes and affect cancer hallmarks. We summarize the major epigenetic modifications in lung cancer, focusing on DNA methylation and ncRNAs, their roles in tumorigenesis, and their effects on key signaling pathways. In addition, we describe the clinical application of epigenetic biomarkers in the early diagnosis, prognosis prediction, and oncotherapy of lung cancer. Understanding the epigenetic regulation mechanism of lung cancer can provide a new explanation for tumorigenesis and a new target for the precise treatment of lung cancer.

Subtyping Lung Cancer Using DNA Methylation in Liquid Biopsies

BACKGROUND

Lung cancer (LCa) is the most frequently diagnosed and lethal cancer worldwide. Histopathological subtyping, which has important therapeutic and prognostic implications, requires material collection through invasive procedures, which might be insufficient to enable definitive diagnosis. Aberrant DNA methylation is an early event in carcinogenesis, detectable in circulating cell-free DNA (ccfDNA). Herein, we aimed to assess methylation of selected genes in ccfDNA from LCa patients and determine its accuracy for tumor subtyping.

METHODS

Methylation levels of APC, HOXA9, RARβ2, and RASSF1A were assessed in three independent study groups (study group #1: 152 tissue samples; study group #2: 129 plasma samples; study group #3: 28 benign lesions of lung) using quantitative methylation-specific PCR. Associations between gene promoter methylation levels and LCa subtypes were evaluated using non-parametric tests. Receiver operating characteristic (ROC) curve analysis was performed.

RESULTS

In study group #2, HOXA9 and RASSF1A displayed higher methylation levels in small-cell lung cancer (SCLC) than in non-small-cell lung cancer (NSCLC). HOXA9 displayed high sensitivity (63.8%), whereas RASSF1A disclosed high specificity (96.2%) for SCLC detection in ccfDNA. Furthermore, HOXA9 methylation levels showed to be higher in squamous cell carcinoma in comparison with adenocarcinoma in study group #1.

CONCLUSIONS

Methylation level assessments in ccfDNA may provide a minimally invasive procedure for LCa subtyping, complementing standard diagnostic procedures.

The potential of retinoids for combination therapy of lung cancer: Updates and future directions

Lung cancer is the most common cancer-related death worldwide. Natural compounds have shown high biological and pharmaceutical relevance as anticancer agents. Retinoids are natural derivatives of vitamin A having many regulatory functions in the human body, including vision, cellular proliferation and differentiation, and activation of tumour suppressor genes. Retinoic acid (RA) is a highly active retinoid isoform with promising anti-lung cancer activity. The abnormal expression of retinoid receptors is associated with loss of anticancer activities and acquired resistance to RA in lung cancer. The preclinical promise has not translated to the general clinical utility of retinoids for lung cancer patients, especially those with a history of smoking. Newer retinoid nano-formulations and the combinatorial use of retinoids has been associated with lower toxicity and more favorably efficacy in both the preclinical and clinical settings. Here, we highlight epidemiological and clinical therapeutic studies involving retinoids and lung cancer. We also discuss the biological actions of retinoids in lung cancer, which include effects on cancer stem cell differentiation, angiogenesis, metastasis, and proliferative. We suggest that the use of retinoids in combination with conventional and targeted anticancer agents will broaden the utility of these potent anticancer compounds in the lung cancer clinic.

The Relevance of Gender in Tumor-Influencing Epigenetic Traits

Tumorigenesis as well as the molecular orchestration of cancer progression are very complex mechanisms that comprise numerous elements of influence and regulation. Today, many of the major concepts are well described and a basic understanding of a tumor's fine-tuning is given. Throughout the last decade epigenetics has been featured in cancer research and it is now clear that the underlying mechanisms, especially DNA and histone modifications, are important regulators of carcinogenesis and tumor progression. Another key regulator, which is well known but has been neglected in scientific approaches as well as molecular diagnostics and, consequently, treatment conceptualization for a long time, is the subtle influence patient gender has on molecular processes. Naturally, this is greatly based on hormonal differences, but from an epigenetic point of view, the diverse susceptibility to stress and environmental influences is of prime interest. In this review we present the current view on which and how epigenetic modifications, emphasizing DNA methylation, regulate various tumor diseases. It is our aim to elucidate gender and epigenetics and their interconnectedness, which will contribute to understanding of the prospect molecular orchestration of cancer in individual tumors.

Label-free Detection for a DNA Methylation Assay Using Raman Spectroscopy

Background:

DNA methylation has been suggested as a biomarker for early cancer detection and treatment. Varieties of technologies for detecting DNA methylation have been developed, but they are not sufficiently sensitive for use in diagnostic devices. The aim of this study was to determine the suitability of Raman spectroscopy for label-free detection of methylated DNA.

Methods:

The methylated promoter regions of cancer-related genes cadherin 1 (CDH1) and retinoic acid receptor beta (RARB) served as target DNA sequences. Based on bisulfite conversion, oligonucleotides of methylated or nonmethylated probes and targets were synthesized for the DNA methylation assay. Principal component analysis with linear discriminant analysis (PCA-DA) was used to discriminate the hybridization between probes and targets (methylated probe and methylated target or nonmethylated probe and nonmethylated target) of CDH1 and RARB from nonhybridization between the probe and targets (methylated probe and nonmethylated target or nonmethylated probe and methylated target).

Results:

This study revealed that the CDH1 and RARB oligo sets and their hybridization data could be classified using PCA-DA. The classification results for CDH1 methylated probe + CDH1 methylated target versus CDH1 methylated probe + CDH1 unmethylated target showed sensitivity, specificity, and error rates of 92%, 100%, and 8%, respectively. The classification results for the RARB methylated probe + RARB methylated target versus RARB methylated probe + RARB unmethylated target showed sensitivity, specificity, and error rates of 92%, 93%, and 11%, respectively.

Conclusions:

Label-free detection of DNA methylation could be achieved using Raman spectroscopy with discriminant analysis.

Functional dissection of the role of UHRF1 in the regulation of retinoblastoma methylome

UHRF1 (ubiquitin-like with PHD and RING finger domains 1) is a critical regulator for DNA methylation, and its frequent overexpression in human cancers has been associated with tumor-promoting effects. However, whether the overexpressed UHRF1 contributes to the establishment and maintenance of tumor methylomes and whether this process can affect the tumorigenesis remain unclear. In this study, we show that UHRF1 is highly expressed in retinoblastoma, and genomes of human primary retinoblastoma and cell lines have differential DNA methylation patterns compared with those of normal retina, characterized by lower global methylation and higher promoter methylation of tumor suppressors. However, our genome-wide DNA methylation study uncovers that UHRF1 down-modulation in retinoblastoma cells exerts minor effects on the existing methylation patterns at both bulk genome and individual gene loci, suggesting that retinoblastoma methylome is primarily maintained by other mechanisms. Furthermore, using two murine retinoblastoma models, we found that high UHRF1 expression does not alter global methylation levels in both premalignant neonatal retina and retinoblastoma tumors, implying that DNA hypomethylation may not be an early mechanism driving retinoblastoma tumorigenesis unlike what has been proposed for other types of cancer. These results suggest that tumor-promoting functions of UHRF1 in retinoblastoma are largely independent of its role in DNA methylation.

Filomicelles Deliver a Chemo-Differentiation Combination of Paclitaxel and Retinoic Acid That Durably Represses Carcinomas in Liver to Prolong Survival

Drug resistance and relapse is common in cancer treatments with chemotherapeutics, and while drug combinations with naturally occurring, differentiation-inducing retinoic acid (RA) provide remission-free cures for one type of liquid tumor, solid tumors present major problems for delivery. Here, inspired by filoviruses that can be microns in length, flexible filomicelles that self-assemble from an amphiphilic block copolymer (PEG-PCL) are shown to effectively deliver RA and paclitaxel (TAX) to several solid tumor models, particularly in the liver. These hydrophobic compounds synergistically load into the cores of the elongated micelles, and the coloaded micelles prove most effective at causing cell death, ploidy, and durable regression of tumors compared to free drugs or to separately loaded drugs. RA-TAX filomicelles also reduce mortality of human lung or liver derived cancers engrafted at liver, intraperitoneal, and subcutaneous sites in immunodeficient mice. In vitro studies show that the dual drug micelles effectively suppress proliferation while upregulating a generic differentiation marker. The results highlight the potency of dual-loaded filomicelles in killing cancer cells or else driving their differentiation away from growth.

Association between Retinoic acid receptor-β hypermethylation and NSCLC risk: a meta-analysis and literature review

Emerging evidence indicates that Retinoic acid receptor-β (RARβ) is a tumor suppressor in many types of tumor. However, whether or not RARβ is a risk factor and is correlated to clinicopathological characteristics of non-small cell lung cancer (NSCLC) remains unclear. In this report, we performed a meta-analysis to determine the effects of RARβ hypermethylation on the incidence of NSCLC and clinicopathological characteristics in human NSCLC patients. Final valuation and analysis of 1780 cancer patients from 16 eligible studies was performed. RARβ hypermethylation was found to be significantly higher in NSCLC than in normal lung tissue, the pooled OR from 7 studies including 646 NSCLC and 580 normal lung tissues, OR = 6.05, 95% CI = 3.56-10.25, p<0.00001. RARβ hypermethylation was significantly higher in adenocarcinoma (AC) compared to squamous cell carcinoma (SCC), pooled OR is 0.68 (95% CI = 0.52-0.89, p = 0.005). RARβ hypermethylation was also found to occur significantly higher in smoker (n = 232) than non-smoker (n = 213) (OR = 2.46, 95% CI = 1.54-3.93, p = 0.0002). Our results indicate that RARβ hypermethylation correlates well with an increased risk in NSCLC patients. RARβ geneinactivation caused by RARβ methylation contributes the NSCLC tumorigenesis and may serve as a potential risk factor, diagnostic marker and drug target of NSCLC.

Epigenome-Based Precision Medicine in Lung Cancer

Lung cancer is the leading cause of cancer-related deaths in the world. Despite significant advances in the early detection and treatment of the disease, the prognosis remains poor, with an overall 5-year survival rate ranging from 15% to 20%. This poor prognosis results largely from early micrometastatic spread of cancer cells to nearby lymph nodes or tissues and partially from early recurrence after curative surgical resection. Recently, precision medicines that target potential oncogenic driver mutations have been approved to treat lung cancer. However, some lung cancer patients do not have targetable mutations, and many patients develop resistance to targeted therapy. Tumor heterogeneity and mutational density are also challenges in treating lung cancer, which underscores the need for developing alternative therapeutic strategies for treating lung cancer. Epigenetic therapy may circumvent the problems of tumor heterogeneity and drug resistance by affecting the expression of several hundred target genes. This review highlights precision medicine using an innovative approach of epigenetic priming prior to conventional standard therapy or targeted cancer therapy in lung cancer.

DNA methylation in lung tissues of mouse offspring exposed in utero to polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) comprise an important class of environmental pollutants that are known to cause lung cancer in animals and are suspected lung carcinogens in humans. Moreover, evidence from cell-based studies points to PAHs as modulators of the epigenome. The objective of this work was to assess patterns of genome-wide DNA methylation in lung tissues of adult offspring initiated in utero with the transplacental PAH carcinogens dibenzo [def,p]chrysene (DBC) or benzo [a]pyrene (BaP). Genome-wide methylation patterns for normal (not exposed), normal adjacent and lung tumor tissues obtained from adult offspring were determined using methylated DNA immunoprecipitation (MeDIP) with the NimbleGen mouse DNA methylation CpG island array. Lung tumor incidence in 45-week old mice initiated with BaP was 32%, much lower than that of the DBC-exposed offspring at 96%. Also, male offspring appeared more susceptible to BaP as compared to females. Distinct patterns of DNA methylation were associated with non-exposed, normal adjacent and adenocarcinoma lung tissues, as determined by principal components, hierarchical clustering and gene ontology analyses. From these methylation profiles, a set of genes of interest was identified that includes potential important targets for epigenetic modification during the process of lung tumorigenesis in animals exposed to environmental PAHs.

Epigenetic therapy approaches in non-small cell lung cancer: Update and perspectives

Non-small cell lung cancer (NSCLC) still constitutes the most common cancer-related cause of death worldwide. All efforts to introduce suitable treatment options using chemotherapeutics or targeted therapies have, up to this point, failed to exhibit a substantial effect on the 5-year-survival rate. The involvement of epigenetic alterations in the evolution of different cancers has led to the development of epigenetics-based therapies, mainly targeting DNA methyltransferases (DNMTs) and histone-modifying enzymes. So far, their greatest success stories have been registered in hematologic neoplasias. As the effects of epigenetic single agent treatment of solid tumors have been limited, the investigative focus now lies on combination therapies of epigenetically active agents with conventional chemotherapy, immunotherapy, or kinase inhibitors. This review includes a short overview of the most important preclinical approaches as well as an extensive discussion of clinical trials using epigenetic combination therapies in NSCLC, including ongoing trials. Thus, we are providing an overview of what lies ahead in the field of epigenetic combinatory therapies of NSCLC in the coming years.

Tumour biomarkers: homeostasis as a novel prognostic indicator

The term 'personalized medicine' refers to a medical procedure that consists in the grouping of patients based on their predicted individual response to therapy or risk of disease. In oncologic patients, a 'tailored' therapeutic approach may potentially improve their survival and well-being by not only reducing the tumour, but also enhancing therapeutic response and minimizing the adverse effects. Diagnostic tests are often used to select appropriate and optimal therapies that rely both on patient genome and other molecular/cellular analysis. Several studies have shown that lifestyle and environmental factors can influence the epigenome and that epigenetic events may be involved in carcinogenesis. Thus, in addition to traditional biomarkers, epigenetic factors are raising considerable interest, because they could potentially be used as an excellent tool for cancer diagnosis and prognosis. In this review, we summarize the role of conventional cancer genetic biomarkers and their association with epigenomics. Furthermore, we will focus on the so-called 'homeostatic biomarkers' that result from the physiological response to cancer, emphasizing the concept that an altered 'new' homeostasis influence not only tumour environment, but also the whole organism.

Curcumin use in pulmonary diseases: State of the art and future perspectives

Curcumin (diferuloylmethane) is a yellow pigment present in the spice turmeric (Curcuma longa). It has been used for centuries in Ayurveda (Indian traditional medicine) for the treatment of several diseases. Over the last several decades, the therapeutic properties of curcumin have slowly been elucidated. It has been shown that curcumin has pleiotropic effects, regulating transcription factors (e.g., NF-kB), cytokines (e.g., IL6, TNF-alpha), adhesion molecules (e.g., ICAM-1), and enzymes (e.g., MMPs) that play a major role in inflammation and cancerogenesis. These effects may be relevant for several pulmonary diseases that are characterized by abnormal inflammatory responses, such as asthma or chronic obstructive pulmonary disease, acute respiratory distress syndrome, pulmonary fibrosis, and acute lung injury. Furthermore, some preliminary evidence suggests that curcumin may have a role in the treatment of lung cancer. The evidence for the use of curcumin in pulmonary disease is still sparse and has mostly been obtained using either in vitro or animal models. The most important issue with the use of curcumin in humans is its poor bioavailability, which makes it necessary to use adjuvants or curcumin nanoparticles or liposomes. The aim of this review is to summarize the available evidence on curcumin's effectiveness in pulmonary diseases, including lung cancer, and to provide our perspective on future research with curcumin so as to improve its pharmacological effects, as well as provide additional evidence of curcumin's efficacy in the treatment of pulmonary diseases.

Epigenetics in non-small cell lung cancer: from basics to therapeutics

Lung cancer remains the number one cause of cancer-related deaths worldwide with 221,200 estimated new cases and 158,040 estimated deaths in 2015. Approximately 80% of cases are non-small cell lung cancer (NSCLC). The diagnosis is usually made at an advanced stage where the prognosis is poor and therapeutic options are limited. The evolution of lung cancer is a multistep process involving genetic, epigenetic, and environmental factor interactions that result in the dysregulation of key oncogenes and tumor suppressor genes, culminating in activation of cancer-related signaling pathways. The past decade has witnessed the discovery of multiple molecular aberrations that drive lung cancer growth, among which are epidermal growth factor receptor (EGFR) mutations and translocations involving the anaplastic lymphoma kinase (ALK) gene. This has translated into therapeutic agent developments that target these molecular alterations. The absence of targetable mutations in 50% of NSCLC cases and targeted therapy resistance development underscores the importance for developing alternative therapeutic strategies for treating lung cancer. Among these strategies, pharmacologic modulation of the epigenome has been used to treat lung cancer. Epigenetics approaches may circumvent the problem of tumor heterogeneity by affecting the expression of multiple tumor suppression genes (TSGs), halting tumor growth and survival. Moreover, it may be effective for tumors that are not driven by currently recognized druggable mutations. This review summarizes the molecular pathology of lung cancer epigenetic aberrations and discusses current efforts to target the epigenome with different pharmacological approaches. Our main focus will be on hypomethylating agents, histone deacetylase (HDAC) inhibitors, microRNA modulations, and the role of novel epigenetic biomarkers. Last, we will address the challenges that face this old-new strategy in treating lung cancer.

Regulation of Retinoic Acid Receptor Beta by Interleukin-15 in the Lung during Cigarette Smoking and Influenza Virus Infection

Virus-induced exacerbations often lead to further impairment of lung function in chronic obstructive pulmonary disease. IL-15 is critical in antiviral immune responses. Retinoic acid (RA) signaling plays an important role in tissue maintenance and repair, particularly in the lung. We studied RA signaling and its relation to IL-15 in the lung during cigarette smoke (CS) exposure and influenza virus infection. In vivo studies show that RA signaling is diminished by long-term CS exposure or influenza virus infection alone, which is further attenuated during infection after CS exposure. RA receptor β (RARβ) is specifically decreased in the lung of IL-15 transgenic (overexpression; IL-15Tg) mice, and a greater reduction in RARβ is found in these mice compared with wild-type (WT) mice after infection. RARβ is increased in IL-15 knockout (IL-15KO) mice compared with WT mice after infection, and the additive effect of CS and virus on RARβ down-regulation is diminished in IL-15KO mice. IL-15 receptor α (IL-15Rα) is increased and RARβ is significantly decreased in lung interstitial macrophages from IL-15Tg mice compared with WT mice. In vitro studies show that IL-15 down-regulates RARβ in macrophages via IL-15Rα signaling during influenza virus infection. These studies suggest that RA signaling is significantly diminished in the lung by CS exposure and influenza virus infection. IL-15 specifically down-regulates RARβ expression, and RARβ may play a protective role in lung injury caused by CS exposure and viral infections.

Clinicopathological significance and a potential drugtarget of RARβ in non-small-cell lung carcinoma: a meta-analysis and a systematic review

Lung cancer is the leading cause of cancer-related mortality in men worldwide. Aberrant RARβ promoter methylation has been frequently investigated in non-small-cell lung carcinoma (NSCLC), the most common form of lung cancer. The aim of present study was to carry out a meta-analysis and a systematic review to evaluate clinicopathological significance of RARβ promoter hypermethylation in NSCLC. A systematic literature search was carried out. The data were extracted and assessed by two reviewers independently. The Cochrane software Review Manager 5.2 was used to conduct the review. Odds ratios (ORs) with 95% corresponding confidence intervals (CIs) were calculated. A total of 18 relevant articles were available for meta-analysis which included 1,871 participants. The frequency of RARβ hypermethylation was significantly increased in NSCLC than in nonmalignant lung tissue, and the pooled OR was 5.69 (P<0.00001). RARβ hypermethylation was significantly more frequently observed in adenocarcinoma (AC) than in squamous cell carcinoma (SCC), and the pooled OR was 1.47 (P=0.005). Hypermethylation of RARβ gene in NSCLC was 2.46 times higher in smoking than in nonsmoking individuals, and the pooled OR was 2.46 (P=0.0002). RARβ hypermethylation rate was not significantly correlated with stage of the disease and sex. RARβ gene methylation status was not associated with prognosis of patients with NSCLC. In conclusion, RARβ promoter hypermethylation significantly increased in NSCLC than in non-neoplastic lung tissue and is predominant in AC, suggesting that RARβ methylation contributes to the development of NSCLC, especially AC. RARβ gene is a potential novel target for development of personalized therapy in patients with NSCLC, and is promising in restoration of retinoic acid-target gene induction via demethylation of RARβ1' promoter.

Non-DHFR-mediated effects of methotrexate in osteosarcoma cell lines: epigenetic alterations and enhanced cell differentiation

Background

Methotrexate is an important chemotherapeutic drug widely known as an inhibitor of dihydrofolate reductase (DHFR) which inhibits the reduction of folic acid. DHFR-mediated effects are apparently responsible for its primary antineoplastic action. However, other non-DHFR-mediated effects of methotrexate have been recently discovered, which might be very useful in the development of new strategies for the treatment of pediatric malignancies. The principal goal of this study was to analyze the possible impact of clinically achievable methotrexate levels on cell proliferation, mechanisms of epigenetic regulation (DNA methylation and histone acetylation), induced differentiation and the expression of differentiation-related genes in six osteosarcoma cell lines.

Methods

The Saos-2 reference cell line and five other patient-derived osteosarcoma cell lines were chosen for this study. The MTT assay was used to assess cell proliferation, DNA methylation and histone acetylation were detected using ELISA, and western blotting was used for a detailed analysis of histone acetylation. The expression of differentiation-related genes was quantified using RT-qPCR and the course of cell differentiation was evaluated using Alizarin Red S staining, which detects the level of extracellular matrix mineralization.

Results

Methotrexate significantly decreased the proliferation of Saos-2 cells exclusively, suggesting that this reference cell line was sensitive to the DHFR-mediated effects of methotrexate. In contrast, other results indicated non-DHFR-mediated effects in patient-derived cell lines. Methotrexate-induced DNA demethylation was detected in almost all of them; methotrexate was able to lower the level of 5-methylcytosine in treated cells, and this effect was similar to the effect of 5-aza-2′-deoxycytidine. Furthermore, methotrexate increased the level of acetylated histone H3 in the OSA-06 cell line. Methotrexate also enhanced all-trans retinoic acid-induced cell differentiation in three patient-derived osteosarcoma cell lines, and the modulation of expression of the differentiation-related genes was also shown.

Conclusions

Overall non-DHFR-mediated effects of methotrexate were detected in the patient-derived osteosarcoma cell lines. Methotrexate acts as an epigenetic modifier and has a potential impact on cell differentiation and the expression of related genes. Furthermore, the combination of methotrexate and all-trans retinoic acid can be effective as a differentiation therapy for osteosarcoma.

Association of Clostridium difficile infection in hospital mortality: A systematic review and meta-analysis

BACKGROUND

The purpose of this study was to evaluate whether Clostridium difficile infection (CDI) contributed to hospital mortality and whether the correlation between intensive care units (ICUs) and surgical wards in hospital CDI risk still remain controversial.

METHODS

By meta-analysis, 12 eligible studies involving 8,509 cases and 247,285 controls were identified via PubMed and Embase.

RESULTS

CDI patients had a higher risk of hospital mortality than non-CDI patients (odds ratio [OR], 1.899; 95% confidence interval [CI], 1.269-2.840), especially in 30-day mortality (OR, 2.521; 95% CI, 1.800-3.531). No correlation was found between hospital CDI and Charlson comorbidity index (OR, 0.830; 95% CI, 0.559-1.231). Patients treated in the ICU have an increased risk of hospital CDI (OR, 1.820; 95% CI, 1.161-2.851). However, the risk of CDI in patients who used to have surgery in surgical wards was not different to patients in the other departments (OR, 1.054; 95% CI, 0.838-1.325). Moreover, CDI patients in studies from the most recent 5 years have a higher risk of hospital mortality (OR, 2.171; 95% CI, 1.426-3.304).

CONCLUSION

Hospital CDI was associated with an increased risk of hospital mortality, especially in 30-day mortality. In addition, when compared with past years, CDI patients have a higher risk of hospital mortality in the most recent 5 years. Given the rapid dissemination of this organism worldwide, there is a need to aggressively develop and evaluate primary preventive strategies targeting CDI among hospitalized patients, especially in ICUs.

Combination of retinoid and histone deacetylase inhibitor produced an anti-tumor effect in cutaneous T-cell lymphoma by restoring tumor suppressor gene, retinoic acid receptorβ2, via histone acetylation

BACKGROUND

Retinoids exert anti-proliferative, differentiative, and apoptosis-inducing effects through their receptors. Retinoic acid receptor (RAR) β2 behaves as a tumor suppressor gene, and its expression is suppressible by DNA methylation in many malignancies.

OBJECTIVE

We aimed to determine whether combining a retinoid, Am 80, with a histone deacetylase inhibitor, MS-275, could suppress tumor growth in a RARβ2-negative human cutaneous T cell lymphoma (CTCL) cell lines and freshly isolated primary CTCL cells, and to elucidate the epigenetic mechanism behind the phenomena.

METHODS

SeAx cells were implanted subcutaneously in NOD-SCID mice which were randomly divided into four groups and treated with either Am80, MS-275 by oral gavage (five days/week), or a combination of the two agents. Cell proliferation assay, methylation-specific PCR, flow cytometric analysis of cell cycle and apoptosis and chromatin immunoprecipitation assay were employed.

RESULTS

Quantitative PCR analysis revealed that RARβ2 gene expression was restored only by this combination rather than by either of the agents singly. Restored retinoid sensitivity was observed in combining retinoid with a histone deacetylase inhibitor significantly inhibited cell growth in vitro, suppressed subcutaneously transplanted tumor growth, and prolonged survival of tumor-bearing mice in vivo by more strongly inducing apoptosis and p21 expression in CTCL cells than either agent alone. In the combination treatment, the histone H4 acetylation level at lysine 12 and 16 in the promoter region increased after restoration of RARβ2 expression although the DNA methylation of RARβ2 remained unchanged.

CONCLUSION

This is the first report of histone acetylation as the primary event in the restoration of RARβ2. Inducible RARβ2 expression may serve as a reliable predictor for tumor response in patients undergoing 'epigenetic & differentiation' therapy.

Vitamin A depletion induced by cigarette smoke is associated with an increase in lung cancer-related markers in rats

BACKGROUND

We have previously demonstrated that cigarette smoke is associated with a significant reduction of retinoic acid in rat lungs and the formation of tracheal precancerous lesions. However, the underlying mechanism of cancer risk induced by vitamin A deficiency is unclear. The purpose of this study was to determine whether the cigarette smoke-induced depletion of vitamin A is related to changes in lung cancer risk-related molecular markers.

RESULTS

We investigated the roles of the retinoic acid receptors (RARs) as well as other biomarkers for potential cancer risk in the lungs of rats exposed to cigarette smoke. Twenty-four male weanling rats were fed a purified diet and divided equally into four groups. Three experimental groups were exposed to increasing doses of cigarette smoke from 20, 40 or 60 commercial cigarettes/day for 5 days/week. After 6 weeks, the retinoic acid concentrations in the lung tissue as measured via high performance liquid chromatography (HPLC) significantly decreased (P < 0.01) in cigarette smoke exposed groups. Western Blot analysis revealed that cigarette smoke exposure increased lung protein expression of RAR α in a threshold manner and decreased RAR β and RAR γ expression in a dose-dependent fashion. Protein expressions of cyclin E and proliferating cell nuclear antigen (PCNA) were increased significantly in a dose-dependent manner in cigarette smoke exposed-groups. Additionally, there was a significant increase in protein expression of cJun and cyclin D1 demonstrating a threshold effect similar to that exhibited by RARα, suggesting a potential independent signaling pathway for RARα in lung carcinogenesis.

CONCLUSIONS

Findings from this study suggest that cigarette smoke-induced lung retinoic acid depletion may involve two independent pathways, RARα- and RARβ-mediated, responsible for the increased cancer risk associated with cigarette smoke-induced vitamin A deficiency.

Curcumin Reactivates Silenced Tumor Suppressor Gene RARβ by Reducing DNA Methylation

Reactivation of tumor suppressor genes by nontoxic bioactive food component represents a promising strategy for cancer chemoprevention. Retinoic acid receptor β (RARβ), one member of the RAR receptor family, is considered as a tumor suppressor. Reduced expression of RARβ has been reported in lung cancer and other solid tumors. DNA hypermethylation of the promoter region of RARβ is a major mechanism for its silencing in tumors. Recently, curcumin has been considered as a potential DNA methyltransferase inhibitor. Herein, we demonstrated that curcumin significantly elevate RARβ expression at the mRNA and protein levels in tested cancer cells. Additionally, curcumin decreased RARβ promoter methylation in lung cancer A549 and H460 cells. Mechanistic study demonstrated that curcumin was able to downregulate the mRNA levels of DNMT3b. In a lung cancer xenograft node mice model, curcumin exhibited protective effect against weight loss because of tumor burden. Tumor growth was strongly repressed by curcumin treatment. As the results from in vitro, RARβ mRNA were increased and DNMT3b mRNA were decreased by curcumin treatment compared with the mice in control group. Altogether, this study reveals a novel molecular mechanism of curcumin as a chemo-preventive agent for lung cancer through reactivation of RARβ.

Epigenetic Mechanisms of Human Papillomavirus-Associated Head and Neck Cancer

CONTEXT

Growing evidence suggests that as many as half of all oropharyngeal squamous cell carcinomas (OPSCCs) harbor human papillomavirus (HPV) infections. Despite being more advanced at diagnosis, HPV-positive OPSCCs are associated with a better response to therapy and longer patient survival than HPV-negative OPSCCs. Human papillomavirus-positive OPSCC has also been shown to have distinct host gene expression profiles compared with HPV-negative OPSCC. Recently, this distinction has been shown to include the epigenome. It is well supported that cancers are epigenetically deregulated. This review highlights epigenetic differences between HPV-positive and HPV-negative OPSCCs. The epigenetic mechanisms highlighted include methylation changes to host and viral DNA, and host chromatin modification. We also review the current evidence regarding host DNA methylation changes associated with smoking, and deregulation of microRNA expression in HPV-positive OPSCC.

OBJECTIVE

To provide an overview of epigenetic mechanisms reported in HPV-positive OPSCC, with analogies to cervical cancer, and discussion of the challenges involved in studying epigenetic changes in HPV-associated OPSCC in combination with changes associated with smoking.

DATA SOURCES

Sources were a literature review of peer-reviewed articles in PubMed on HPV and either OPSCC or head and neck squamous cell carcinoma, and related epigenetic mechanisms.

CONCLUSIONS

Epigenetic changes are reported to be a contributing factor to maintaining a malignant phenotype in HPV-positive OPSCC. The epigenetic mechanisms highlighted in this review can be studied for potential as biomarkers or as drug targets. Furthermore, continued research on the deregulation of epigenetic mechanisms in HPV-positive OPSCC (compared with HPV-negative OPSCC) may contribute to our understanding of the clinical and biologic differences between HPV-positive and HPV-negative OPSCC.

Combined effects methylation of FHIT, RASSF1A and RARβ genes on non-small cell lung cancer in the Chinese population

Epigenetic modifications of tumour suppressor genes are involved in all kinds of human cancer. Aberrant promoter methylation is also considered to play an essential role in development of lung cancer, but the pathogenesis remains unclear.We collected the data of 112 subjects, including 56 diagnosed patients with lung cancer and 56 controls without cancer. Methylation of the FHIT, RASSF1A and RAR-β genes in DNA from all samples and the corresponding gene methylation status were assessed using the methylation-specific polymerase chain reaction (PCR, MSP). The results showed that the total frequency of separate gene methylation was significantly higher in lung cancer compared with controls (33.9-85.7 vs 0 %) (p<0.01).Similar outcomes were obtained from the aberrant methylation of combinations of any two or three genes (p<0.01). There was a tendency that the frequency of combinations of any two or three genes was higher in stage I+II than that in stage III+IV with lung cancer. However, no significant difference was found across various clinical stages and clinic pathological gradings of lung cancer (p>0.05).These observations suggest that there is a significant association of promoter methylation of individual genes with lung cancer risk, and that aberrant methylation of combination of any two or three genes may be associated with clinical stage in lung cancer patients and involved in the initiation of lung cancer tumorigenesis. Methylation of FHIT, RASSF1A and RARβ genes may be related to progression of lung oncogenesis.

RARβ2 hypermethylation is associated with poor recurrence-free survival in never-smokers with adenocarcinoma of the lung

Background

This study was aimed at investigating if the effect of RARβ2 hypermethylation on recurrence-free survival (RFS) in non-small cell lung cancer (NSCLC) depends on one’s smoking status and specific interacting proteins.

Results

We retrospectively analyzed the expressions of five proteins using immunohistochemistry in archival formalin-fixed and paraffin-embedded tissues from 578 NSCLC patients who had undergone surgical resection from 1994 through 2004. Promoter methylation of RARβ2 was assessed by bisulfite pyrosequencing. Recurrence was found in 268 (46%) of 578 NSCLCs with a median follow-up period of 4.8 years. Overexpression of β-catenin, c-MET, cyclin D1, and EGFR occurred in 55%, 72%, 51%, and 41% of the patients, respectively. E-cadherin expression was negative in 62% of the patients, and RARβ2 hypermethylation was found in 37%. The abnormal expression of c-MET (P = 0.002) and EGFR (P = 0.001) was found to be highly prevalent in never-smokers. RARβ2 hypermethylation was significantly associated with poor recurrence-free survival (RFS) in 128 never-smokers with adenocarcinoma (P = 0.01) For parsimonious model building, the five proteins were clustered into three groups (β-catenin and E-cadherin; c-MET; cyclin D1 and EGFR) by an unsupervised hierarchical clustering and were included in a multivariate analysis. Cox proportional hazard analysis showed that RARβ2 hypermethylation was significantly associated with poor RFS in 128 never-smokers with adenocarcinoma (adjusted hazard ratio [HR] = 2.19, 95% confidence interval [CI] = 1.28 to 3.47; P = 0.009), after adjusting for interacting proteins.

Conclusions

The present study suggests that RARβ2 hypermethylation may be an independent prognostic factor of RFS in never-smokers with adenocarcinoma of the lung.

Retinoic acid receptors: from molecular mechanisms to cancer therapy

Retinoic acid (RA), the major bioactive metabolite of retinol or vitamin A, induces a spectrum of pleiotropic effects in cell growth and differentiation that are relevant for embryonic development and adult physiology. The RA activity is mediated primarily by members of the retinoic acid receptor (RAR) subfamily, namely RARα, RARβ and RARγ, which belong to the nuclear receptor (NR) superfamily of transcription factors. RARs form heterodimers with members of the retinoid X receptor (RXR) subfamily and act as ligand-regulated transcription factors through binding specific RA response elements (RAREs) located in target genes promoters. RARs also have non-genomic effects and activate kinase signaling pathways, which fine-tune the transcription of the RA target genes. The disruption of RA signaling pathways is thought to underlie the etiology of a number of hematological and non-hematological malignancies, including leukemias, skin cancer, head/neck cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, renal cell carcinoma, pancreatic cancer, liver cancer, glioblastoma and neuroblastoma. Of note, RA and its derivatives (retinoids) are employed as potential chemotherapeutic or chemopreventive agents because of their differentiation, anti-proliferative, pro-apoptotic, and anti-oxidant effects. In humans, retinoids reverse premalignant epithelial lesions, induce the differentiation of myeloid normal and leukemic cells, and prevent lung, liver, and breast cancer. Here, we provide an overview of the biochemical and molecular mechanisms that regulate the RA and retinoid signaling pathways. Moreover, mechanisms through which deregulation of RA signaling pathways ultimately impact on cancer are examined. Finally, the therapeutic effects of retinoids are reported.

RARβ Promoter Methylation as an Epigenetic Mechanism of Gene Silencing in Non-small Cell Lung Cancer

The retinoid acid receptor-p (RARβ) gene is one of the tumor suppressor genes (TSGs), which is frequently deleted or epigenetically silenced at an early stage of tumor progression. In this study we investigated the promoter methylation and expression status of the RARβ gene in 60 surgically resected non-small cell lung cancer (NSCLC) tissue samples and 60 corresponding unchanged lung tissue samples, using methylation-specific PCR and real-time-polymerase chain reaction (qPCR) techniques. We correlated the results with the pathological features of tumors and clinical characteristics of patients. qPCR analysis detected a significantly lower RARβ expression in the patients with adenocarcinoma (AC) and large cell carcinoma (LCC) than in those with squamous cell carcinoma (SCC) (AC vs. SCC, p = 0.032; AC and LCC vs. SCC, p = 0.0 13). Additionally, significantly lower expression of the RARβ gene was revealed in the patients with non-squamous cell cancer with a history of smoking assessed as pack-years (PY < 40 vs. PY ≥ 40, p = 0.045). Regarding RARβ promoter methylation, we found significant differences in the methylation index in the SCC group when considering pTNM staging; with higher index values in T1a + T1b compared with T2a + T2b and T3 + T4 groups (p = 0.024). There was no correlation between the methylation status and expression level of the RARβ gene, which suggests that other molecular mechanisms influence the RARβ expression in NSCLC patients. In conclusion, different expression of the RARβ gene in SCC and NSCC makes the RARβ gene a valuable diagnostic marker for differentiating the NSCLC subtypes.

Epigenetics of lung cancer

Lung cancer is the leading cause of cancer-related mortality in the United States. Epigenetic alterations, including DNA methylation, histone modifications, and noncoding RNA expression, have been reported widely in the literature to play a major role in the genesis of lung cancer. The goal of this review is to summarize the common epigenetic changes associated with lung cancer to give some clarity to its etiology, and to provide an overview of the potential translational applications of these changes, including applications for early detection, diagnosis, prognostication, and therapeutics.

Chemoprevention of lung cancer: concepts and strategies

Lung cancer develops in a stepwise fashion, with an accumulation of molecular alterations progressing through preinvasive steps to invasive disease. This progression could be arrested or reversed through pharmacologic treatments, which are known as cancer chemoprevention. Preclinical and clinical findings relating to different classes of candidate chemopreventive agents provide support for this strategy as an active and promising approach for controlling this disease.

Maintaining the unmethylated state

BACKGROUND

A remarkable correspondence exists between the cytogenetic locations of the known fragile sites and frequently reported sites of hypermethylation. The best-known features of fragile sites are sequence motifs that are prone to the spontaneous formation of a non-B DNA structure. These facts, coupled with the known enzymological specificities of DNA methyltransferase 1 (DNMT1), the ATP-dependent and actin-dependent helicases, and the ten-eleven translocation (TET) dioxygenases, suggest that these enzymes are involved in an epigenetic cycle that maintains the unmethylated state at these sites by resolving non-B structure, preventing both the sequestration of DNA methyltransferases (DNMTs) and hypermethylation in normal cells.

PRESENTATION OF THE HYPOTHESIS

The innate tendency of DNA sequences present at fragile sites to form non-B DNA structures results in de novo methylation of DNA at these sites that is held in check in normal cells by the action of ATP-dependent and actin-dependent helicases coupled with the action of TET dioxygenases. This constitutes a previously unrecognized epigenetic repair cycle in which spontaneously forming non-B DNA structures formed at fragile sites are methylated by DNMTs as they are removed by the action of ATP-dependent and actin-dependent helicases, with the resulting nascent methylation rendered non-transmissible by TET dioxygenases.

TESTING THE HYPOTHESIS

A strong prediction of the hypothesis is that knockdown of ATP-dependent and actin-dependent helicases will result in enhanced bisulfite sensitivity and hypermethylation at non-B structures in multiple fragile sites coupled with global hypomethylation.

IMPLICATIONS OF THE HYPOTHESIS

A key implication of the hypothesis is that helicases, like the lymphoid-specific helicase and alpha thalassemia/mental retardation syndrome X-linked helicase, passively promote accurate maintenance of DNA methylation by preventing the sequestration of DNMTs at sites of unrepaired non-B DNA structure. When helicase action is blocked due to mutation or downregulation of the respective genes, DNMTs stall at unrepaired non-B structures in fragile sites after methylating them and are unable to methylate other sites in the genome, resulting in hypermethylation at non-B DNA-forming sites, along with hypomethylation elsewhere.

The association of retinoic acid receptor beta2(RARβ2) methylation status and prostate cancer risk: a systematic review and meta-analysis

The retinoic acid receptor beta2(RARβ2) is a type of nuclear receptor that is activated by both all-trans retinoic acid and 9-cis retinoic acid, which has been shown to function as a tumor suppressor gene in different types of human tumors. Previous reports demonstrated that the frequency of RARβ2 methylation was significantly higher in prostate cancer patients compared with controls, but the relationship between RARβ2 promoter methylation and pathological stage or Gleason score of prostate cancer remained controversial. Therefore, a meta-analysis of published studies investigating the effects of RARβ2 methylation status in prostate cancer occurrence and association with both pathological stage and Gleason score in prostate cancer was performed in the study. A total of 12 eligible studies involving 777 cases and 404 controls were included in the pooled analyses. Under the random-effects model, the pooled OR of RARβ2 methylation in prostate cancer patients, compared to non-cancer controls, was 17.62 with 95%CI = 6.30-49.28. The pooled OR with the fixed-effects model of pathological stage in RASSF1A methylated patients, compared to unmethylated patients, was 0.67 (95%CI = 0.40-1.09) and the pooled OR of low-GS in RARβ2 methylated patients by the random-effect model, compared to high-GS RARβ2 methylated patients, was 0.54 (95%CI = 0.28-1.04). This study showed that RARβ2 might be a potential biomarker in prostate cancer prevention and diagnosis. The detection of RARβ2 methylation in urine or serum is a potential non-invasive diagnostic tool in prostate cancer. The present findings also require confirmation through adequately designed prospective studies.

Repression of G protein-coupled receptor family C group 5 member A is associated with pathologic differentiation grade of oral squamous cell carcinoma

BACKGROUND

G protein-coupled receptor family C group 5 member A (GPRC5A), a member of G protein-coupled receptor family, has been shown to function as a tumor suppressor in lung tissue. The biological functions of GPRC5A have therefore been linked to lung tissue. However, the biological significance of this gene product remains obscure. In this study, we investigated the expression of GPRC5A proteins in normal oral tissue and oral squamous cell carcinoma (OSCC), and we characterized its biological activity in OSCC cell lines.

METHODS

Western blot analysis and immunohistochemical staining were used to investigate the expression of GPRC5A in both OSCC cell lines and clinical samples. GPRC5A stable transfectants and their parental OSCC cells were characterized for their biological activities in anchorage-independent growth.

RESULTS

High levels of immunohistochemical GPRC5A expression were detected in normal oral tissue, especially differentiated area. In contrast, GPRC5A expression was dramatically repressed in OSCCs (P < 0.01). The immunohistochemical GPRC5A expression was moderately well differentiated, but greatly repressed in moderately differentiated OSCCs and completely repressed in poorly differentiated OSCCs. Overexpression of GPRC5A in OSCC CAL27 cells resulted in a suppressed anchorage-independent growth activity, a transforming phenotype.

CONCLUSIONS

GPRC5A is expressed in normal oral epithelium. Repression of GPRC5A is associated with poorly differential grade of OSCCs. Overexpression of GPRC5A in OSCC cell line reversed the malignant phenotype. Thus, GPRC5A is important for homeostasis in oral tissue, and deletion or repression of this gene may involve in tumorigenesis of OSCCs and may serve as a prognostic marker for malignant type of OSCCs.

Significant frequency of allelic imbalance in 3p region covering RARβ and MLH1 loci seems to be essential in molecular non-small cell lung cancer diagnosis

The aim of the study was to investigate the influence of allelic imbalance (AI) in several loci of tumor suppressor genes in 3p region on the non-small cell lung cancer (NSCLC) development. We evaluated the frequency of loss of heterozygosity and/or microsatellite imbalance (LOH/MSI) and assessed their association with patients’ characteristics (age, gender, tobacco addiction) and NSCLC classification according to TNM/AJCC staging. To analyze the potential role of AI involved in NSCLC pathogenesis, we allelotyped a group of 74 NSCLC patients using 7 microsatellite markers. The highest frequency of LOH/MSI, however, not statistically significant, was observed in RARβ and MLH1 (p = 0.104 and p = 0.216, respectively) loci. The association between high LOH/MSI frequency in 3p region with male gender (p = 0.041) as well as with age (especially >60 years) for RARβ and MLH1 genes (p = 0.0001 and p = 0.020, respectively) was documented. Statistically significant increased frequency of MLH1 allelic loss in squamous cell carcinoma (SCC) versus non-squamous cell carcinoma (non-SCC) was observed (p = 0.01). Significant increase in LOH/MSI frequency in 3p region (mainly in FHIT and MLH1loci) in correlation with cigarette addiction in a lifetime (≥40 years and ≥40 Pack Years) was also documented (p < 0.05). The highest LOH/MSI was revealed in RARβ locus in IA tumors (p = 0.0001), while the similarly high allelic loss of MLH1 correlated with III A/B tumors (p = 0.0002), according to AJCC staging. The obtained results demonstrate that AI is influenced by tobacco smoking and seems to be vital in the molecular diagnosis of NSCLC, especially of SCC subtype.

Specific Biomarkers Are Associated with Docetaxeland Gemcitabine-Resistant NSCLC Cell Lines

Five-year survival rate for lung cancer is limited to 10% to 15%. Therefore, the identification of novel therapeutic prognostic factors is an urgent requirement. The aim of this study is thus to highlight specific biomarkers in chemoresistant non-small cell lung cancer cell lines. Therefore, we checked-in the control condition as well as after short-term pharmacological treatment with either docetaxel or gemcitabine-the expression of genes such as tumor suppressor genes (CDKN2A, DAPK, FHIT, GSTP1, MGMT, RARβ2, RASSF1A, and TIMP3), genes associated with drug resistance (BRCA1, COX2, ERCC1, IGFBP3, RRM1, and TUBB3), and stemness-related genes (CD133, OCT4, and SLUG) in two cellular models of squamous carcinoma (CAEP) and adenocarcinoma (RAL) of the lung originally established. Their promoter methylation profile was also evaluated. Drug-related genes were upregulated. Cisplatin resistance matched with high levels of BRCA1 and ERCC1 in both cell lines; docetaxel sensitivity of CAEP cells was associated to levels of TUBB3 lower than RAL cells. Although CAEP cells were more sensitive to gemcitabine, both cell lines showed high levels of RRM1. Stemness-related genes were downregulated in the control condition but became upregulated in docetaxel-resistant cells, indicating the selection of a population with stemness features. We did not find an unequivocal correspondence between gene expression and respective DNA promoter methylation status, suggesting the involvement of additional mechanisms of gene expression regulation. These results highlight specific biomarkers consistent with the different responses of the two cell lines to standard pharmacological treatments and indicate specific molecular traits for their chemoresistance.

Drugs for preventing lung cancer in healthy people

BACKGROUND

This is an updated version of the original review published in Issue 2, 2003. Some studies have suggested a protective effect of antioxidant nutrients on lung cancer. Observational epidemiological studies suggest an association between higher dietary levels of fruits and vegetables containing beta-carotene and a lower risk of lung cancer.

OBJECTIVES

To determine whether vitamins, minerals and other potential agents, alone or in combination, reduce incidence and mortality from lung cancer in healthy people.

SEARCH METHODS

For this update we have used a search strategy adapted from the design in the original review. The following electronic databases have been searched up to December 2011: MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL). References included in published studies and reviews were also screened.

SELECTION CRITERIA

Included studies were randomised controlled clinical trials comparing different vitamins, mineral supplements or supplements with placebo, administered to healthy people with the aim of preventing lung cancer.

DATA COLLECTION AND ANALYSIS

Two authors independently selected the trials to be included in the review, assessed the methodological quality of each trial and extracted data using a standardised form. For each study, relative risk and 95% confidence limits were calculated for dichotomous outcomes and pooled results were calculated using the random-effect model.

MAIN RESULTS

In the first version of this review four studies were included; in this review update, an additional five studies have been included. Four studies included only males and two only females; two studies included only participants considered at high risk, namely smokers or exposed to asbestos, and one study included people deficient in many micronutrients. Six studies analysed vitamin A, three vitamin C, four vitamin E, one selenium supplements, and six studied combinations of two or more products. All the RCTs included in this review were classified as being of low risk of bias.For people not at high risk of lung cancer and compared to placebo, none of the supplements of vitamins or minerals or their combinations resulted in a statistically significant difference in lung cancer incidence or mortality, except for a single study that included 7627 women and found a higher risk of lung cancer incidence for those taking vitamin C but not for total cancer incidence, but that effect was not seen in males or when the results for males and females were pooled.For people at high risk of lung cancer, such as smokers and those exposed to asbestos and compared to placebo, beta-carotene intake showed a small but statistically significant higher risk of lung cancer incidence, lung cancer mortality and for all-causes mortality.

AUTHORS' CONCLUSIONS

There is no evidence for recommending supplements of vitamins A, C, E, selenium, either alone or in different combinations, for the prevention of lung cancer and lung cancer mortality in healthy people. There is some evidence that the use of beta-carotene supplements could be associated with a small increase in lung cancer incidence and mortality in smokers or persons exposed to asbestos.

DNA methylation biomarkers offer improved diagnostic efficiency in lung cancer

The exceptional high mortality of lung cancer can be instigated to a high degree by late diagnosis. Despite the plethora of studies on potential molecular biomarkers for lung cancer diagnosis, very few have reached clinical implementation. In this study, we developed a panel of DNA methylation biomarkers and validated their diagnostic efficiency in bronchial washings from a large retrospective cohort. Candidate targets from previous high-throughput approaches were examined by pyrosequencing in an independent set of 48 lung tumor/normal paired. Ten promoters were selected and quantitative methylation-specific PCR (qMSP) assays were developed and used to screen 655 bronchial washings from the Liverpool Lung Project (LLP) subjects divided into training (194 cases and 214 controls) and validation (139 cases and 109 controls) sets. Three statistical models were used to select the optimal panel of markers and to evaluate the performance of the discriminatory algorithms. The final logit regression model incorporated hypermethylation at p16, TERT, WT1, and RASSF1. The performance of this 4-gene methylation signature in the validation set showed 82% sensitivity and 91% specificity. In comparison, cytology alone in this set provided 43% sensitivity at 100% specificity. The diagnostic efficiency of the panel did not show any biases with age, gender, smoking, and the presence of a nonlung neoplasm. However, sensitivity was predictably higher in central (squamous and small cell) than peripheral (adenocarcinomas) tumors, as well as in stage 2 or greater tumors. These findings clearly show the impact of DNA methylation-based assays in the diagnosis of cytologically occult lung neoplasms. A prospective trial is currently imminent in the LLP study to provide data on the enhancement of diagnostic accuracy in a clinical setting, including by additional markers.