Multiple clonal abnormalities in the bronchial epithelium of patients with lung cancer

Repeat treatment of organotypic airway cultures with ethyl methanesulfonate causes accumulation of somatic cell mutations without expansion of bronchial-carcinoma-specific cancer driver mutations

The human in vitro organotypic air-liquid-interface (ALI) airway tissue model is structurally and functionally similar to the human large airway epithelium and, as a result, is being used increasingly for studying the toxicity of inhaled substances. Our previous research demonstrated that DNA damage and mutagenesis can be detected in human airway tissue models under conditions used to assess general and respiratory toxicity endpoints. Expanding upon our previous proof-of-principle study, human airway epithelial tissue models were treated with 6.25-100 µg/mL ethyl methanesulfonate (EMS) for 28 days, followed by a 28-day recovery period. Mutagenesis was evaluated by Duplex Sequencing (DS), and clonal expansion of bronchial-cancer-specific cancer-driver mutations (CDMs) was investigated by CarcSeq to determine if both mutation-based endpoints can be assessed in the same system. Additionally, DNA damage and tissue-specific responses were analyzed during the treatment and following the recovery period. EMS exposure led to time-dependent increases in mutagenesis over the 28-day treatment period, without expansion of clones containing CDMs; the mutation frequencies remained elevated following the recovery. EMS also produced an increase in DNA damage measured by the CometChip and MultiFlow assays and the elevated levels of DNA damage were reduced (but not eliminated) following the recovery period. Cytotoxicity and most tissue-function changes induced by EMS treatment recovered to control levels, the exception being reduced proliferating cell frequency. Our results indicate that general, respiratory-tissue-specific and genotoxicity endpoints increased with repeat EMS dosing; expansion of CDM clones, however, was not detected using this repeat treatment protocol. DISCLAIMER: This article reflects the views of its authors and does not necessarily reflect those of the U.S. Food and Drug Administration. Any mention of commercial products is for clarification only and is not intended as approval, endorsement, or recommendation.

Mathematical Modeling of Field Cancerization through the Lens of Cancer Behavioral Ecology

Field cancerization is a process in which a normal tissue is replaced with pre-cancerous but histologically normal tissue. This transformed field can give rise to malignancy and contribute to tumor relapse. In this paper, we create a mathematical model of field cancerization from the perspective of cancer behavioral ecology. In our model, field cancerization arises from a breakdown in signaling integrity and control, and investigate implications for acute wounding, chronic wounding, aging, and therapeutic interventions. We find that restoration of communication networks can lead to cancer regression in the context of acute injury. Conversely, long term loss of controls, such as through chronic wounding or aging, can promote oncogenesis. These results are paralleled in therapeutic interventions: those that simply target cells in cancerous states may be less effective than those that reestablish signaling integrity. Viewing cancer as a corruption of communication systems rather than as a corruption of individual cells may lead to novel approaches for understanding and treating this disease.

Game of clones: Battles in the field of carcinogenesis

Recent advances in bulk sequencing approaches as well as genomic decoding at the single-cell level have revealed surprisingly high somatic mutational burdens in normal tissues, as well as increased our understanding of the landscape of "field cancerization", that is, molecular and immune alterations in mutagen-exposed normal-appearing tissues that recapitulated those present in tumors. Charting the somatic mutational landscapes in normal tissues can have strong implications on our understanding of how tumors arise from mutagenized epithelium. Making sense of those mutations to understand the progression along the pathologic continuum of normal epithelia, preneoplasias, up to malignant tissues will help pave way for identification of ideal targets that can guide new strategies for preventing or eliminating cancers at their earliest stages of development. In this review, we will provide a brief history of field cancerization and its implications on understanding early stages of cancer pathogenesis and deviation from the pathologically "normal" state. The review will provide an overview of how mutations accumulating in normal tissues can lead to a patchwork of mutated cell clones that compete while maintaining an overall state of functional homeostasis. The review also explores the role of clonal competition in directing the fate of normal tissues and summarizes multiple mechanisms elicited in this phenomenon and which have been linked to cancer development. Finally, we highlight the importance of understanding mutations in normal tissues, as well as clonal competition dynamics (in both the epithelium and the microenvironment) and their significance in exploring new approaches to combatting cancer.

DNA repair as an emerging target for COPD-lung cancer overlap

Cigarette smoking is the leading cause of lung cancer and chronic obstructive pulmonary disease (COPD). Many of the detrimental effects of cigarette smoke have been attributed to the development of DNA damage, either directly from chemicals contained in cigarette smoke or as a product of cigarette smoke-induced inflammation and oxidative stress. In this review, we discuss the environmental, epidemiological, and physiological links between COPD and lung cancer and the likely role of DNA damage and repair in COPD and lung cancer development. We explore alterations in DNA damage repair by DNA repair proteins and pathways. We discuss emerging data supporting a key role for the DNA repair protein, xeroderma pigmentosum group C (XPC), in cigarette smoke-induced COPD and early lung cancer development. Understanding the interplay between cigarette smoke, DNA damage repair, COPD, and lung cancer may lead to prognostic tools and new, potentially targetable, pathways for lung cancer prevention and treatment.

Is mitochondrial dysfunction a driving mechanism linking COPD to nonsmall cell lung carcinoma?

Chronic obstructive pulmonary disease (COPD) patients are at increased risk of developing nonsmall cell lung carcinoma, irrespective of their smoking history. Although the mechanisms behind this observation are not clear, established drivers of carcinogenesis in COPD include oxidative stress and sustained chronic inflammation. Mitochondria are critical in these two processes and recent evidence links increased oxidative stress in COPD patients to mitochondrial damage. We therefore postulate that mitochondrial damage in COPD patients leads to increased oxidative stress and chronic inflammation, thereby increasing the risk of carcinogenesis.The functional state of the mitochondrion is dependent on the balance between its biogenesis and degradation (mitophagy). Dysfunctional mitochondria are a source of oxidative stress and inflammasome activation. In COPD, there is impaired translocation of the ubiquitin-related degradation molecule Parkin following activation of the Pink1 mitophagy pathway, resulting in excessive dysfunctional mitochondria. We hypothesise that deranged pathways in mitochondrial biogenesis and mitophagy in COPD can account for the increased risk in carcinogenesis. To test this hypothesis, animal models exposed to cigarette smoke and developing emphysema and lung cancer should be developed. In the future, the use of mitochondria-based antioxidants should be studied as an adjunct with the aim of reducing the risk of COPD-associated cancer.

Bronchial airway gene expression signatures in mouse lung squamous cell carcinoma and their modulation by cancer chemopreventive agents

Due to exposure to environmental toxicants, a “field cancerization” effect occurs in the lung resulting in the development of a field of initiated but morphologically normal appearing cells in the damaged epithelium of bronchial airways with dysregulated gene expression patterns. Using a mouse model of lung squamous cell carcinoma (SCC), we performed transcriptome sequencing (RNA-Seq) to profile bronchial airway gene expression and found activation of the PI3K and Myc signaling networks in cytologically normal bronchial airway epithelial cells of mice with preneopastic lung SCC lesions, which was reversed by treatment with the PI3K Inhibitor XL-147 and pioglitazone, respectively. Activated MYC signaling was also present in premalignant and tumor tissues from human lung SCC patients. In addition, we identified a key microRNA, mmu-miR-449c-5p, whose suppression significantly up-regulated Myc expression in the normal bronchial airway epithelial cells of mice with early stage SCC lesions. We developed a novel bronchial genomic classifier in mice and validated it in humans. In the classifier, Ppbp (pro-platelet basic protein) was overexpressed 115 fold in the bronchial airways of mice with preneoplastic lung SCC lesions. This is the first report that demonstrates Ppbp as a novel biomarker in the bronchial airway for lung cancer diagnosis.

Fixed-Dose Combinations of Pioglitazone and Metformin for Lung Cancer Prevention

Combination treatment with pioglitazone and metformin is utilized clinically in the treatment of type II diabetes. Treatment with this drug combination reduced the development of aerodigestive cancers in this patient population. Our goal is to expand this treatment into clinical lung cancer chemoprevention. We hypothesized that dietary delivery of metformin/pioglitazone would prevent lung adenoma formation in A/J mice in a benzo[a]pyrene (B[a]P)-induced carcinogenesis model while modulating chemoprevention and anti-inflammatory biomarkers in residual adenomas. We found that metformin (500 and 850 mg/kg/d) and pioglitazone (15 mg/kg/d) produced statistically significant decreases in lung adenoma formation both as single-agent treatments and in combination, compared with untreated controls, after 15 weeks. Treatment with metformin alone and in combination with pioglitazone resulted in statistically significant decreases in lung adenoma formation at both early- and late-stage interventions. Pioglitazone alone resulted in significant decreases in adenoma formation only at early treatment intervention. We conclude that oral metformin is a viable chemopreventive treatment at doses ranging from 500 to 1,000 mg/kg/d. Pioglitazone at 15 mg/kg/d is a viable chemopreventive agent at early-stage interventions. Combination metformin and pioglitazone performed equal to metformin alone and better than pioglitazone at 15 mg/kg/d. Because the drugs are already FDA-approved, rapid movement to human clinical studies is possible. Cancer Prev Res; 10(2); 116-23. ©2017 AACR.

Early Events in the Molecular Pathogenesis of Lung Cancer

The majority of cancer-related deaths in the United States and worldwide are attributed to lung cancer. There are more than 90 million smokers in the United States who represent a significant population at elevated risk for lung malignancy. In other epithelial tumors, it has been shown that if neoplastic lesions can be detected and treated at their intraepithelial stage, patient prognosis is significantly improved. Thus, new strategies to detect and treat lung preinvasive lesions are urgently needed in order to decrease the overwhelming public health burden of lung cancer. Limiting these advances is a poor knowledge of the earliest events that underlie lung cancer development and that would constitute markers and targets for early detection and prevention. This review summarizes the state of knowledge of human lung cancer pathogenesis and the molecular pathology of premalignant lung lesions, with a focus on the molecular premalignant field that associates with lung cancer development. Lastly, we highlight new approaches and models to study genome-wide alterations in human lung premalignancy in order to facilitate the discovery of new markers for early detection and prevention of this fatal disease. Cancer Prev Res; 9(7); 518-27. ©2016 AACR.

The clonal evolution and therapeutic approaches of lung cancer

According to the World Cancer Research Foundation, the newly diagnosed annual lung cancer cases all over the world are alarmingly high at 12.5 %. It also shows the highest mortality rate among all the cancer types. Nearly 225,000 new lung cancer patients are reported annually in the USA. The lung cancer cells also have very fast growth rates. As a result of this rapid proliferation rate, the lung cancer cells are sensitive to the available therapeutics like the radiation, surgical, or chemo therapy. Notwithstanding all the advances in the field of tumor biology, the mortality rate with lung cancer has remained significantly high. Precise and early diagnosis of the disease can be an important step in the proper and successful setting up of the treatment modalities. There are no comprehensive reviews available that discusses all the basic and updated aspects of lung cancer. This review focuses on the basic aspects of lung cancer like the etiology, risk factors, and clonal evolution. Exposure to smoking comes up as a single major environmental cause of the disease. The classification of lung cancer has also been discussed in detail based on immunohistochemistry. The existing therapeutic approaches as well as the upcoming modern day interventions have been discussed with their pros and cons. Recent techniques like molecular profiling can prove to be highly beneficial if properly standardized. With such advancements in therapy in conjunction with the updated diagnostics, there is a real hope in the treatment of lung cancer.

Airway basal cells of healthy smokers express an embryonic stem cell signature relevant to lung cancer

Activation of the human embryonic stem cell (hESC) signature genes has been observed in various epithelial cancers. In this study, we found that the hESC signature is selectively induced in the airway basal stem/progenitor cell population of healthy smokers (BC-S), with a pattern similar to that activated in all major types of human lung cancer. We further identified a subset of 6 BC-S hESC genes, whose coherent overexpression in lung adenocarcinoma (AdCa) was associated with reduced lung function, poorer differentiation grade, more advanced tumor stage, remarkably shorter survival, and higher frequency of TP53 mutations. BC-S shared with hESC and a considerable subset of lung carcinomas a common TP53 inactivation molecular pattern which strongly correlated with the BC-S hESC gene expression. These data provide transcriptome-based evidence that smoking-induced reprogramming of airway BC toward the hESC-like phenotype might represent a common early molecular event in the development of aggressive lung carcinomas in humans.

Angiogenin and vascular endothelial growth factor expression in lungs of lung cancer patients

BACKGROUND.: Lung cancer is the leading cause of cancer deaths. Angiogenesis is crucial process in cancer growth and progression. This prospective study evaluated expression of two central regulatory molecules: angiogenin and vascular endothelial growth factor (VEGF) in patients with lung cancer. PATIENTS AND METHODS.: Clinical data, blood samples and broncho-alveolar lavage (BAL) from 23 patients with primary lung carcinoma were collected. BAL fluid was taken from part of the lung with malignancy, and from corresponding healthy side of the lung. VEGF and angiogenin concentrations were analysed by an enzyme-linked immunosorbent assay. Dilution of bronchial secretions in the BAL fluid was calculated from urea concentration ratio between serum and BAL fluid. RESULTS.: We found no statistical correlation between angiogenin concentrations in serum and in bronchial secretions from both parts of the lung. VEGF concentrations were greater in bronchial secretions in the affected side of the lung than on healthy side. Both concentrations were greater than serum VEGF concentration. VEGF concentration in serum was in positive correlation with tumour size (p = 0,003) and with metastatic stage of disease (p = 0,041). There was correlation between VEGF and angiogenin concentrations in bronchial secretions from healthy side of the lung and between VEGF and angiogenin concentrations in bronchial secretions from part of the lung with malignancy. CONCLUSION.: Angiogenin and VEGF concentrations in systemic, background and local samples of patients with lung cancer are affected by different mechanisms. Pro-angiogenic activity of lung cancer has an important influence on the levels of angiogenin and VEGF.

The topography of DNA methylation in the non-neoplastic colonic mucosa surrounding colorectal cancers

The degree of gene hypermethylation in non-neoplastic colonic mucosa (NNCM) is a potentially important event in the development of colorectal cancer (CRC), particularly for the subgroup with a CpG island methylator phenotype (CIMP). In this study, we aimed to use an unbiased and high-throughput approach to evaluate the topography of DNA methylation in the non-neoplastic colonic mucosa (NNCM) surrounding colorectal cancer (CRC). A total of 61 tissue samples comprising 53 NNCM and 8 tumor samples were obtained from hemicolectomy specimens of two CRC patients (Cases 1 and 2). NNCM was stripped from the underlying colonic wall and samples taken at varying distances from the tumor. The level of DNA methylation in NNCM and tumor tissues was assessed at 1,505 CpG sites in 807 cancer-related genes using Illumina GoldenGate® methylation arrays. Case 1 tumor showed significantly higher levels of methylation compared to surrounding NNCM samples (P < 0.001). The average level of methylation in NNCM decreased with increasing distance from the tumor (r = -0.418; P = 0.017), however this was not continuous and "patches" with higher levels of methylation were observed. Case 2 tumor was less methylated than Case 1 tumor (average β-value 0.181 vs. 0.415) and no significant difference in the level of methylation was observed in comparison to the surrounding NNCM. No evidence was found for a diminishing gradient of methylation in the NNCM surrounding CRC with a high level of methylation. Further work is required to determine whether CIMP+ CRC develop from within "patches" of NCCM that display high levels of methylation.

Preneoplasia of lung cancer

As with other epithelial cancers, lung cancer develops over a period of several years or decades via a series of progressive morphological changes accompanied by molecular alterations that commence in histologically normal epithelium. However the development of lung cancer presents certain unique features that complicates this evaluation. Anatomically the respiratory tree may be divided into central and peripheral compartments having different gross and histological anatomies as well as different functions. In addition, there are three major forms of lung cancer and many minor forms. Many of these forms arise predominantly in either the central or peripheral compartments. Squamous cell and small cell carcinomas predominantly arise in the central compartment, while adenocarcinomas predominantly arise peripherally. Large cell carcinomas are not a single entity but consist of poorly differentiated forms of the other types and, possibly, some truly undifferentiated "stem cell like" tumors. The multistage origin of squamous cell carcinomas, because of their central location, can be followed more closely than the peripherally arising adenocarcinomas. Squamous cell carcinomas arise after a series of reactive, metaplastic, premalignant and preinvasive changes. However, long term observations indicate that not all tumors follow a defined histologic course, and the clinical course, especially of early lesions, is difficult to predict. Peripheral adenocarcinomas are believed to arise from precursor lesions known as atypical adenomatous hyperplasias and may have extensive in situ growth before becoming invasive. Small cell carcinomas are believed to arise from severely molecularly damaged epithelium without going through recognizable preneoplastic changes. The molecular changes that occur prior to the onset on invasive cancers are extensive. As documented in this chapter, they encompass all of the six classic Hallmarks of Cancer other than invasion and metastasis, which by definition occur beyond preneoplasia. A study of preinvasive lung cancer has yielded much valuable biologic information that impacts on clinical management.

Heterogeneity and degree of TIMP4, GATA4, SOX18, and EGFL7 gene promoter methylation in non-small cell lung cancer and surrounding tissues

We used methylation-sensitive high resolution melting analysis to assess methylation of CpG islands within the promoters of the TIMP4, GATA4, SOX18, and EGFL7 genes in samples of non-small cell lung cancer and surrounding apparently normal tissue and noncancerous lung tissues. We found that the promoter methylation was heterogeneous in both tumor and surrounding normal tissue. This is in contrast to healthy lung tissue, where the promoters were normally either non- or hypomethylated, and the heterogeneity of methylation was low. An increased heterogeneity of methylation in the normal tissues surrounding the tumor may suggest an early start of epigenetic processes preceding genetic and morphologic changes and can be used as a biomarker of early cancerization events. This analysis is an easy and sensitive tool for studying epigenetic heterogeneity and could be used in clinical practice.

Ice-COLD-PCR enables rapid amplification and robust enrichment for low-abundance unknown DNA mutations

Identifying low-abundance mutations within wild-type DNA is important in several fields of medicine, including cancer, prenatal diagnosis and infectious diseases. However, utilizing the clinical and diagnostic potential of rare mutations is limited by sensitivity of the molecular techniques employed, especially when the type and position of mutations are unknown. We have developed a novel platform that incorporates a synthetic reference sequence within a polymerase chain reaction (PCR) reaction, designed to enhance amplification of unknown mutant sequences during COLD-PCR (CO-amplification at Lower Denaturation temperature). This new platform enables an Improved and Complete Enrichment (ice-COLD-PCR) for all mutation types and eliminates shortcomings of previous formats of COLD-PCR. We evaluated ice-COLD-PCR enrichment in regions of TP53 in serially diluted mutant and wild-type DNA mixtures. Conventional-PCR, COLD-PCR and ice-COLD-PCR amplicons were run in parallel and sequenced to determine final mutation abundance for a range of mutations representing all possible single base changes. Amplification by ice-COLD-PCR enriched all mutation types and allowed identification of mutation abundances down to 1%, and 0.1% by Sanger sequencing or pyrosequencing, respectively, surpassing the capabilities of other forms of PCR. Ice-COLD-PCR will help elucidate the clinical significance of low-abundance mutations and our understanding of cancer origin, evolution, recurrence-risk and treatment diagnostics.

A chronic obstructive pulmonary disease related signature in squamous cell lung cancer

The epidemiological relationship between squamous cell lung cancer (SCC) and chronic obstructive pulmonary disease (COPD), both smoking-related diseases, suggests that they have also a genetic basis. We compared 35 SCC patients with and without COPD with whole-genome gene expression profiles of laser microdissected tissue. Validation of differential expression was performed for 25 genes using quantitative (q)RT-PCR. Subsequently, we performed array-based CGH on the same tumor samples. We found that 374 probes were differentially expressed in SCC from patients with and without COPD. Forty-four probes were derived from genes with mitochondrial functions and 34 probes were located on 5q. All these probes showed a lower expression level in SCC from non-COPD patients. For a random selection of 25 mitochondrial and 5q genes, we confirmed the differential expression by qRT-PCR. Loss of 3p, 5q and 9p was observed, via array-CGH, to be more frequent in SCC from non-COPD patients as compared to SCC from COPD patients. Combination of chromosomal aberrations and the location of the differentially expressed genes showed significant association for loss of the 5q31.2-31.3 region and reduced expression of the 5q genes. In conclusion, a more frequent loss of 5q and a low expression of genes located on 5q in SCC tumors of non-COPD patients compared to tumors from COPD patients was identified suggesting that different oncogenetic pathways are operational in patients with and without COPD.

Two-round coamplification at lower denaturation temperature-PCR (COLD-PCR)-based sanger sequencing identifies a novel spectrum of low-level mutations in lung adenocarcinoma

Reliable identification of cancer-related mutations in TP53 is often problematic, as these mutations can be randomly distributed throughout numerous codons and their relative abundance in clinical samples can fall below the sensitivity limits of conventional sequencing. To ensure the highest sensitivity in mutation detection, we adapted the recently described coamplification at lower denaturation temperature-PCR (COLD-PCR) method to employ two consecutive rounds of COLD-PCR followed by Sanger sequencing. Using this highly sensitive approach we screened 48 nonmicrodissected lung adenocarcinoma samples for TP53 mutations. Twenty-four missense/frameshift TP53 mutations throughout exons 5 to 8 were identified in 23 out of 48 (48%) lung adenocarcinoma samples examined, including eight low-level mutations at an abundance of approximately 1 to 17%, most of which would have been missed using conventional methodologies. The identified alterations include two rare lung adenocarcinoma mutations, one of which is a "disruptive" mutation currently undocumented in the lung cancer mutation databases. A sample harboring a low-level mutation ( approximately 2% abundance) concurrently with a clonal mutation (80% abundance) revealed intratumoral TP53 mutation heterogeneity. The ability to identify and sequence low-level mutations in the absence of elaborate microdissection, via COLD-PCR-based Sanger sequencing, provides a platform for accurate mutation profiling in clinical specimens and the use of TP53 as a prognostic/predictive biomarker, evaluation of cancer risk, recurrence, and further understanding of cancer biology.

Epigenetic inactivation of Homeobox A5 gene in nonsmall cell lung cancer and its relationship with clinicopathological features

Promoter methylation is an important mechanism in gene silencing and is a key epigenetic event in cancer development. Homeobox A5 (HOXA5) is a master regulator of the morphogenesis and cell differentiation to be implicated as a tumor suppressor gene in breast cancer, but its role in lung cancer is still unknown. In this study, we have investigated the methylation status of the promoter region of the HOXA5 gene in nonsmall cell lung cancers (NSCLCs) using nested and standard methylation-specific PCR (MSP) and correlated the methylation status with clinicopathological features. With standard MSP analysis, HOXA5 methylation were found in 113 (81.3%) of 139 NSCLCs and 72 (51.8%) in their corresponding nonmalignant lung tissues. RT-PCR and immunohistochemical analysis showed that HOXA5 methylation correlates with gene expression. Moreover, in the patients with stage I disease, HOXA5 methylation was more frequent in smokers than in never-smokes (P = 0.01). There was no influence of HOXA5 methylation on survival in all NSCLCs or at stages II-IV. However, in the patients with stage I disease, HOXA5 methylation was associated with a borderline significantly worse survival (P = 0.09). These findings suggest that downregulation of the HOXA5 gene by aberrant promoter methylation occurs in the vast majority of NSCLCs and that it may play a role in the pathogenesis of NSCLC. Additional studies with larger sample sizes are required to evaluate the prognostic value of HOXA5 methylation in patients with stage I NSCLC.

Evidence for common clonal origin of multifocal lung cancers

BACKGROUND

Lung cancer is the most common cause of cancer death in the United States. Multiple anatomically separate but histologically similar lung tumors are often found in the same patient. The clonal origin of multiple lung tumors is uncertain.

METHODS

We analyzed 70 lung tumors from 30 patients (23 females and seven males) who underwent surgical resection for lung epithelial tumors, of whom 26 had non-small cell carcinomas and four had carcinoid/atypical carcinoid tumors. All patients had multiple tumors (two to five) involving one or both lungs. Genomic DNA was extracted from paraffin-embedded tissue sections using laser capture microdissection and analyzed for loss of heterozygosity, TP53 mutations, and X-chromosome inactivation status. The percentage (95% confidence interval [CI]) of patients in whom there were concordant patterns of genetic alteration was calculated.

RESULTS

All 30 case subjects showed loss of heterozygosity (LOH) in at least one and at most four of the six polymorphic microsatellite markers. Completely concordant LOH patterns between synchronous and metachronous cancers in individual patients were seen in 26 (87%) of 30 informative patients (95% CI = 75% to 99%). Identical point mutations were present in eight of 10 patients who exhibited TP53 mutation by sequencing. Tumors in 18 (78%) of 23 female patients (95% CI = 67% to 98%) showed identical X-chromosome inactivation patterns. Combining the results of LOH studies, TP53 mutation screening analyses, and X-chromosome inactivation data, we demonstrated that the multiple separate tumors in 23 (77%) of 30 patients (95% CI = 62% to 92%) had identical genetic changes, consistent with monoclonal origin of the separate tumors.

CONCLUSIONS

Our data indicate that the great majority of multifocal lung cancers have a common clonal origin and that multifocality in lung cancer represents local and regional intrapulmonary metastasis.

Confocal fluorescence microendoscopy of bronchial epithelium

Confocal microendoscopy permits the acquisition of high-resolution real-time confocal images of bronchial mucosa via the instrument channel of an endoscope. We report here on the construction and validation of a confocal fluorescence microendoscope and its use to acquire images of bronchial epithelium in vivo. Our objective is to develop an imaging method that can distinguish preneoplastic lesions from normal epithelium to enable us to study the natural history of these lesions and the efficacy of chemopreventive agents without biopsy removal of the lesion that can introduce a spontaneous regression bias. The instrument employs a laser-scanning engine and bronchoscope-compatible confocal probe consisting of a fiber-optic image guide and a graded-index objective lens. We assessed the potential of topical application of physiological pH cresyl violet (CV) as a fluorescence contrast-enhancing agent for the visualization of tissue morphology. Images acquired ex vivo with the confocal microendoscope were first compared with a bench-top confocal fluorescence microscope and conventional histology. Confocal images from five sites topically stained with CV were then acquired in vivo from high-risk smokers and compared to hematoxylin and eosin stained sections of biopsies taken from the same site. Sufficient contrast in the confocal imagery was obtained to identify cells in the bronchial epithelium. However, further improvements in the miniature objective lens are required to provide sufficient axial resolution for accurate classification of preneoplastic lesions.

Smoking and lung cancer: the role of inflammation

Worldwide over 1 million people die due to lung cancer each year. It is estimated that cigarette smoking explains almost 90% of lung cancer risk in men and 70 to 80% in women. Clinically evident lung cancers have multiple genetic and epigenetic abnormalities. These abnormalities may result in activation of oncogenes and inactivation of tumor-suppressor genes. Chronic inflammation, which is known to promote cancer, may result both from smoking and from genetic abnormalities. These mediators in turn may be responsible for increased macrophage recruitment, delayed neutrophil clearance, and increase in reactive oxygen species (ROS). Thus, the pulmonary environment presents a unique milieu in which lung carcinogenesis proceeds in complicity with the host cellular network. The pulmonary diseases that are associated with the greatest risk for lung cancer are characterized by abundant and deregulated inflammation. Pulmonary disorders such as chronic obstructive pulmonary disease (COPD)/emphysema are characterized by profound abnormalities in inflammatory and fibrotic pathways. The cytokines and growth factors aberrantly produced in COPD and the developing tumor microenvironment have been found to have deleterious properties that simultaneously pave the way for both epithelial-mesenchymal transition (EMT) and destruction of specific host cell-mediated immune responses. Full definition of these pathways will afford the opportunity to intervene in specific inflammatory events mediating lung tumorigenesis and resistance to therapy.

Could removing arsenic from tobacco smoke significantly reduce smoker risks of lung cancer?

If a specific biological mechanism could be determined by which a carcinogen increases lung cancer risk, how might this knowledge be used to improve risk assessment? To explore this issue, we assume (perhaps incorrectly) that arsenic in cigarette smoke increases lung cancer risk by hypermethylating the promoter region of gene p16INK4a, leading to a more rapid entry of altered (initiated) cells into a clonal expansion phase. The potential impact on lung cancer of removing arsenic is then quantified using a three-stage version of a multistage clonal expansion (MSCE) model. This refines the usual two-stage clonal expansion (TSCE) model of carcinogenesis by resolving its intermediate or "initiated" cell compartment into two subcompartments, representing experimentally observed "patch" and "field" cells. This refinement allows p16 methylation effects to be represented as speeding transitions of cells from the patch state to the clonally expanding field state. Given these assumptions, removing arsenic might greatly reduce the number of nonsmall cell lung cancer cells (NSCLCs) produced in smokers, by up to two-thirds, depending on the fraction (between 0 and 1) of the smoking-induced increase in the patch-to-field transition rate prevented if arsenic were removed. At present, this fraction is unknown (and could be as low as zero), but the possibility that it could be high (close to 1) cannot be ruled out without further data.

Automated detection of genetic abnormalities combined with cytology in sputum is a sensitive predictor of lung cancer

Detection of lung cancer by sputum cytology has low sensitivity but is noninvasive and, if improved, could be a powerful tool for early lung cancer detection. To evaluate whether the accuracy of diagnosing lung cancer by evaluating sputa for cytologic atypia and genetic abnormalities is greater than that of conventional cytology alone, automated scoring of genetic abnormalities for 3p22.1 and 10q22.3 (SP-A) by fluorescence in situ hybridization (FISH) and conventional cytology was done on sputa from 35 subjects with lung cancer, 25 high-risk smokers, and 6 healthy control subjects. Multivariate analysis was performed to select variables that most accurately predicted lung cancer. A model of probability for the presence of lung cancer was derived for each subject. Cells exfoliated from patients with lung cancer contained genetic aberrations and cytologic atypias at significantly higher levels than in those from control subjects. When combined with cytologic atypia, a model of risk for lung cancer was derived that had 74% sensitivity and 82% specificity to predict the presence of lung cancer, whereas conventional cytology achieved only 37% sensitivity and 87% specificity. For diagnosing lung cancer in sputum, a combination of molecular and cytologic variables was superior to using conventional cytology alone.

In vivo optical coherence tomography imaging of preinvasive bronchial lesions

PURPOSE

Optical coherence tomography (OCT) is an optical imaging method that can visualize cellular and extracellular structures at and below tissue surface. The objective of the study was to determine if OCT could characterize preneoplastic changes in the bronchial epithelium identified by autofluorescence bronchoscopy.

EXPERIMENTAL DESIGN

A 1.5-mm fiberoptic probe was inserted via a bronchoscope into the airways of 138 volunteer heavy smokers participating in a chemoprevention trial and 10 patients with lung cancer to evaluate areas that were found to be normal or abnormal on autofluorescence bronchoscopy. Radial scanning of the airways was done to generate OCT images in real time. Following OCT imaging, the same sites were biopsied for pathologic correlation.

RESULTS

A total of 281 OCT images and the corresponding bronchial biopsies were obtained. The histopathology of these areas includes 145 normal/hyperplasia, 61 metaplasia, 39 mild dysplasia, 10 moderate dysplasia, 6 severe dysplasia, 7 carcinoma in situ, and 13 invasive carcinomas. Quantitative measurement of the epithelial thickness showed that invasive carcinoma was significantly different than carcinoma in situ (P=0.004) and dysplasia was significantly different than metaplasia or hyperplasia (P=0.002). In addition, nuclei of the cells corresponding to histologic results became more discernible in lesions that were moderate dysplasia or worse compared with lower-grade lesions.

CONCLUSION

Preliminary data suggest that autofluorescence bronchoscopy-guided OCT imaging of bronchial lesions is technically feasible. OCT may be a promising nonbiopsy tool for in vivo imaging of preneoplastic bronchial lesions to study their natural history and the effect of chemopreventive intervention.

Chromosome 9 instability and alterations of p16 gene in squamous cell carcinoma of the lung and in adjacent normal bronchi: FISH and immunohistochemical study

AIMS

p16, a tumour suppressor gene located at 9p21 chromosome and involved in cell cycle regulation, is often inactivated in lung carcinoma. Inactivation is also supported by the loss of p16 protein, a strong inhibitor of cyclin-dependent kinase (CDK) 4 and 6. The aim of this study was to examine alterations of p16 both in pulmonary squamous cell carcinoma (SCC) and in morphological normal bronchi contiguous with neoplasia.

METHODS AND RESULTS

p16 gene and chromosome 9 alterations were examined by fluorescence in situ hybridization and the expression of p16 protein by immunohistochemistry in pulmonary surgical specimens from 31 patients with SCC. As controls, surgical specimens from 13 patients with non-neoplastic pathology were examined. Tumours showed molecular alterations for p16 gene and chromosome 9 abnormalities in, respectively, 29/31 and 19/31 cases respectively. p16 protein was unexpressed in 29/31 cases. In morphologically normal bronchi p16 gene and chromosome 9 alterations occurred in, respectively, 13/31 and 4/31 cases respectively; loss of protein immunoreactivity occurred in 14/31 cases. No alterations were seen in any of the control cases.

CONCLUSIONS

Inactivation of p16 gene in histologically normal bronchi could aid the identification of individuals at risk of developing SCC of the lung.

Lung cancer preneoplasia

From histological and biological perspectives, lung cancer is a complex neoplasm. Although the sequential preneoplastic changes have been defined for centrally arising squamous carcinomas of the lung, they have been poorly documented for the other major forms of lung cancers, including small cell lung carcinoma and adenocarcinomas. There are three main morphologic forms of preneoplastic lesions recognized in the lung: squamous dysplasias, atypical adenomatous hyperplasia, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. However, these lesions account for the development of only a subset of lung cancers. Several studies have provided information regarding the molecular characterization of lung preneoplastic changes, especially for squamous cell carcinoma. These molecular changes have been detected in the histologically normal and abnormal respiratory epithelium of smokers. Two different molecular pathways have been detected in lung adenocarcinoma pathogenesis: smoking-associated activation of RAS signaling, and nonsmoking-associated activation of EGFR signaling; the latter is detected in histologically normal respiratory epithelium.

Symmetry, identifiability, and prediction uncertainties in multistage clonal expansion (MSCE) models of carcinogenesis

Many models of exposure-related carcinogenesis, including traditional linearized multistage models and more recent two-stage clonal expansion (TSCE) models, belong to a family of models in which cells progress between successive stages-possibly undergoing proliferation at some stages-at rates that may depend (usually linearly) on biologically effective doses. Biologically effective doses, in turn, may depend nonlinearly on administered doses, due to PBPK nonlinearities. This article provides an exact mathematical analysis of the expected number of cells in the last ("malignant") stage of such a "multistage clonal expansion" (MSCE) model as a function of dose rate and age. The solution displays symmetries such that several distinct sets of parameter values provide identical fits to all epidemiological data, make identical predictions about the effects on risk of changes in exposure levels or timing, and yet make significantly different predictions about the effects on risk of changes in the composition of exposure that affect the pharmacodynamic dose-response relation. Several different predictions for the effects of such an intervention (such as reducing carcinogenic constituents of an exposure) that acts on only one or a few stages of the carcinogenic process may be equally consistent with all preintervention epidemiological data. This is an example of nonunique identifiability of model parameters and predictions from data. The new results on nonunique model identifiability presented here show that the effects of an intervention on changing age-specific cancer risks in an MSCE model can be either large or small, but that which is the case cannot be predicted from preintervention epidemiological data and knowledge of biological effects of the intervention alone. Rather, biological data that identify which rate parameters hold for which specific stages are required to obtain unambiguous predictions. From epidemiological data alone, only a set of equally likely alternative predictions can be made for the effects on risk of such interventions.

The convergent development of molecular-targeted drugs for cancer treatment and prevention

Advances in our understanding of multistep and field carcinogenesis are erasing the clear demarcation of intraepithelial neoplasia from invasive neoplasia. The growing ability to define a very high risk of cancer is forging important commonalities between prevention and therapy, such as in potential prognostic/predictive markers, agents, and side effects that patients would be willing to tolerate, and the logistics of definitive trials. The emergence of promising new molecular-targeted agents and new technologies for screening and early detection provides new opportunities for applying clinical trial designs that integrate therapy and prevention end points. Such trials may be used to facilitate targeted drug development and help identify strategies for both cancer prevention and advanced cancer therapy. These several advances are creating a convergence of cancer therapy with cancer prevention that promises to streamline the development of targeted drugs and improve the control of major cancers.

Lung Cancer Chemoprevention

BACKGROUND

Lung cancer is the most common cause of cancer death in the United States. Cigarette smoking is the main risk factor. Former smokers are at a substantially increased risk for lung cancer compared with lifetime never-smokers. Chemoprevention is the use of specific agents to reverse, suppress, or prevent the process of carcinogenesis. This article reviews the major agents that have been studied for chemoprevention.

METHODS

Articles of primary, secondary, and tertiary prevention trials were reviewed and summarized to obtain recommendations.

RESULTS

None of the phase III trials with the agents beta carotene, retinol, 13-cis-retinoic acid, alpha-tocopherol, N-acetylcysteine, or acetylsalicylic acid has demonstrated beneficial, reproducible results. For facilitating the evaluation of promising agents and for lessening the need for a large sample size, extensive time commitment, and expense, focus is now turning toward the assessment of surrogate end point biomarkers for lung carcinogenesis. With the understanding of important cellular signaling pathways, various inhibitors that may prevent or reverse lung carcinogenesis are being developed.

CONCLUSIONS

By integrating biological knowledge, more trials can be performed in a reasonable time frame. The future of lung cancer chemoprevention should entail the evaluation of single agents or combinations that target various pathways while working toward identification and validation of intermediate end points.

HMGA2 overexpression in non-small cell lung cancer

Lung cancer is still the leading cause of death from cancer worldwide primarily because of the fact that most lung cancers are diagnosed at advanced stages. Overexpression of the high mobility group protein HMGA2 has been observed in a variety of malignant tumors and often correlates with poor prognosis. Herein, HMGA2 expression levels were analyzed in matching cancerous and non-cancerous lung samples of 17 patients with adenocarcinoma (AC) and 17 patients with squamous cell carcinoma (SCC) with real-time quantitative RT-PCR (qRT-PCR). Transcript levels were compared to results obtained by immunohistochemistry (IHC). HMGA2 expression was detectable by qRT-PCR in all samples tested and varied from 5422 to 16 991 545 copies per 250 ng total RNA in the carcinoma samples and from 289 to 525 947 copies in the non-cancerous tissue samples. In 33/34 non-small cell lung cancer (NSCLC) samples tested, an overexpression of HMGA2 was revealed with statistically highly significant differences between non-neoplastic and tumor samples for both AC (P < 0.0001) as well as for SCC (P < 0.0001). Expression varies strongly and is increased up to 911-fold for AC and up to 2504-fold for SCC, respectively, with statistically significant higher increase in SCC (P < 0.05). The results presented herein indicate that HMGA2 overexpression is a common event in NSCLC and could serve as molecular marker for lung cancer.

Genetic deletions in sputum as diagnostic markers for early detection of stage I non-small cell lung cancer

PURPOSE

Analysis of molecular genetic markers in biological fluids has been proposed as a powerful tool for cancer diagnosis. We have characterized in detail the genetic signatures in primary non-small cell lung cancer, which provided potential diagnostic biomarkers for lung cancer. The aim of this study was to determine whether the genetic changes can be used as markers in sputum specimen for the early detection of lung cancer.

EXPERIMENTAL DESIGN

Genetic aberrations in the genes HYAL2, FHIT, and SFTPC were evaluated in paired tumors and sputum samples from 38 patients with stage I non-small cell lung cancer and in sputum samples from 36 cancer-free smokers and 28 healthy nonsmokers by using fluorescence in situ hybridization.

RESULTS

HYAL2 and FHIT were deleted in 84% and 79% tumors and in 45% and 40% paired sputum, respectively. SFTPC was deleted exclusively in tumor tissues (71%). There was concordance of HYAL2 or FHIT deletions in matched sputum and tumor tissues from lung cancer patients (r = 0.82, P = 0.04; r = 0.84, P = 0.03), suggesting that the genetic changes in sputum might indicate the presence of the same genetic aberrations in lung tumors. Furthermore, abnormal cells were found in 76% sputum by detecting combined HYAL2 and FHIT deletions whereas in 47% sputum by cytology, of the cancer cases, implying that detecting the combination of HYAL2 and FHIT deletions had higher sensitivity than that of sputum cytology for lung cancer diagnosis. In addition, HYAL2 and FHIT deletions in sputum were associated with smoking history of cancer patients and smokers (both P < 0.05).

CONCLUSIONS

Tobacco-related HYAL2 and FHIT deletions in sputum may constitute diagnostic markers for early-stage lung cancer.

Clinical implications and utility of field cancerization

Cancer begins with multiple cumulative epigenetic and genetic alterations that sequencially transform a cell, or a group of cells in a particular organ. The early genetic events might lead to clonal expansion of pre-neoplastic daughter cells in a particular tumor field. Subsequent genomic changes in some of these cells drive them towards the malignant phenotype. These transformed cells are diagnosed histopathologically as cancers owing to changes in cell morphology. Conceivably, a population of daughter cells with early genetic changes (without histopathology) remain in the organ, demonstrating the concept of field cancerization. With present technological advancement, including laser capture microdisection and high-throughput genomic technologies, carefully designed studies using appropriate control tissue will enable identification of important molecular signatures in these genetically transformed but histologically normal cells. Such tumor-specific biomarkers should have excellent clinical utility. This review examines the concept of field cancerization in several cancers and its possible utility in four areas of oncology; risk assessment, early cancer detection, monitoring of tumor progression and definition of tumor margins.

OCIA domain containing 2 is highly expressed in adenocarcinoma mixed subtype with bronchioloalveolar carcinoma component and is associated with better prognosis

Although lung adenocarcinoma is a major cause of cancer death worldwide, details of its molecular carcinogenesis and stepwise progression are still unclear. To characterize the sequential progression from bronchioloalveolar adenocarcinoma of the lung (BAC, in situ carcinoma) to adenocarcinoma mixed subtype with BAC component polymerase chain reaction-based cDNA suppression subtractive hybridization (SSH) was carried out using two representative cases of BAC (non-invasive tumors) and adenocarcinoma mixed subtype with BAC (invasive tumors). Through differential screening, virtual reverse northern hybridization and quantitative real-time reverse-transcription-polymerase chain reaction (qRT-PCR) we selected five genes (TncRNA, OCIAD2, ANXA2, TMED4 and LGALS4) that were expressed at significantly higher levels in invasive adenocarcinoma mixed subtype with BAC than in BAC. After in situ hybridization and qRT-PCR analyses, we confirmed that only the OCIAD2 gene showed significantly higher expression in the tumor cells of invasive adenocarcinoma mixed subtype with BAC than in BAC (P = 0.026). We then carried out in situ hybridization of OCIAD2 in 56 adenocarcinoma mixed subtype with BAC component and assessed the correlation between OCIAD2 expression and clinicopathological features. In contrast to our expectation, the patients with OCIAD2 expression showed a better clinical outcome than those without OCIAD2 expression, and OCIAD2 expression showed an inverse correlation with lymphatic invasion, blood vessel invasion and lymph node metastasis. These results suggest that OCIAD2 begins to express at the progression from in situ to invasive carcinoma, and is associated with the favorable prognosis of adenocarcinoma mixed subtype with BAC component.

Genomic signatures in non-small-cell lung cancer: Targeting the targeted therapies

Despite major developments in targeted biologic agents, patients with advanced non-small-cell lung cancer have a poor prognosis. Recent development of targeted biologic agents have given us insight into possibilities of matching therapy with disease; however, the success of these agents has been marginal. In this article, we discuss the use of genomic signatures that have been developed to identify unique aspects of individual lung tumors and provide insight on how novel strategies can be used to identify populations susceptible to specific targeted agents.

Aberrant methylation patterns of theRassf1a gene in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine

To clarify the involvement of the Rassf1a gene in lung carcinogenesis, we investigated the methylation status in the 5' upstream region of the RAS-association domain family 1, isoform A (Rassf1a) gene in rat lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP). Six-week-old male Wistar rats were given 2000 ppm BHP in their drinking water for 12 wk and maintained without further treatment until they were sacrificed at 25 wk. A total of 15 lung adenocarcinomas were obtained and total RNAs were extracted from each for assessment of expression of the Rassf1a gene by reverse transcription (RT)-polymerase chain reaction (PCR) analysis. To measure the methylation status of the Rassf1a gene, five adenocarcinomas with a marked reduction of the Rassf1a expression and two normal lung tissues were used for a bisulfite sequencing analysis. While the normal lung tissue was unmethylated, all five adenocarcinomas were highly methylated in the 5' upstream region. Genomic DNAs were also extracted from 15 adenocarcinomas, and mutation analysis of the Rassf1a was performed with PCR-single-strand conformation polymorphism (SSCP) analysis. No mutations were detected throughout exons 1-6. The present results suggest that the aberrant methylation may be involved in the inactivation of the Rassf1a gene in the development of lung adenocarcinomas induced by BHP in rats.

Interpreting epithelial cancer biology in the context of stem cells: tumor properties and therapeutic implications

Over 90% of all human neoplasia is derived from epithelia. Significant progress has been made in the identification of stem cells of many epithelia. In general, epithelial stem cells lack differentiation markers, have superior in vivo and in vitro proliferative potential, form clusters in association with a specialized mesenchymal environment (the 'niche'), are located in well-protected and nourished sites, and are slow-cycling and thus can be experimentally identified as 'label-retaining cells'. Stem cells may divide symmetrically giving rise to two identical stem cell progeny. Any stem cells in the niche, which defines the size of the stem cell pool, may be randomly expelled from the niche due to population pressure (the stochastic model). Alternatively, a stem cell may divide asymmetrically yielding one stem cell and one non-stem cell that is destined to exit from the stem cell niche (asymmetric division model). Stem cells separated from their niche lose their stemness, although such a loss may be reversible, becoming 'transit-amplifying cells' that are rapidly proliferating but have a more limited proliferative potential, and can give rise to terminally differentiated cells. The identification of the stem cell subpopulation in a normal epithelium leads to a better understanding of many previously enigmatic properties of an epithelium including the preferential sites of carcinoma formation, as exemplified by the almost exclusive association of corneal epithelial carcinoma with the limbus, the corneal epithelial stem cell zone. Being long-term residents in an epithelium, stem cells are uniquely susceptible to the accumulation of multiple, oncogenic changes giving rise to tumors. The application of the stem cell concept can explain many important carcinoma features including the clonal origin and heterogeneity of tumors, the occasional formation of tumors from the transit amplifying cells or progenitor cells, the formation of precancerous 'patches' and 'fields', the mesenchymal influence on carcinoma formation and behavior, and the plasticity of tumor cells. While the concept of cancer stem cells is extremely useful and it is generally assumed that such cells are derived from normal stem cells, more work is needed to identify and characterize epithelial cancer stem cells, to address their precise relationship with normal stem cells, to study their markers and their proliferative and differentiation properties and to design new therapies that can overcome their unusual resistance to chemotherapy and other conventional tumor modalities.

Pathogenesis of lung cancer: 100 year report

Over the past 100 years, our understanding of the pathogenesis of lung cancer has advanced impressively. Environmental carcinogens and a gene locus determining susceptibility have been identified. The pathology of lung cancer has been classified into categories with major clinical implications. The cellular and molecular genetic changes underlying lung cancer have become better understood over the past 25 years, but the stepwise progression of respiratory epithelium from normal to neoplastic is not yet well demarcated, limiting abilities to advance early detection and chemoprevention. The translation of improved understanding of dominant signal transduction pathways in lung cancer to rationally designed therapeutic strategies has had recent successes, demonstrating a proof of principle for targeted therapy in lung cancer. Improvement in overall patient outcomes has been stubbornly slow and will require concerted efforts.

Air pollution and cancer: biomarker studies in human populations

Large cohort studies in the U.S. and in Europe suggest that air pollution may increase lung cancer risk. Biomarkers can be useful to understand the mechanisms and to characterize high-risk groups. Here we describe biomarkers of exposure, in particular DNA adducts as well as markers of early damage, including mutagenicity, other endpoints of genotoxicity and molecular biomarkers of cancer. Several studies found an association between external measures of exposure to air pollution and increased levels of DNA adducts, with an apparent levelling-off of the dose-response relationship. Also, numerous experimental studies in vitro and in vivo have provided unambiguous evidence for genotoxicity of air pollution. In addition, due to the organic extracts of particulate matter [especially various polycyclic aromatic hydrocarbon (PAH) compounds], particulate air pollution induces oxidative damage to DNA. The experimental work, combined with the data on frequent oxidative DNA damage in lymphocytes in people exposed to urban air pollution, suggests 8-oxo-dG as one of the important promutagenic lesions. Lung cancer develops through a series of progressive pathological changes occurring in the respiratory epithelium. Molecular alterations such as loss of heterozygosity, gene mutations and aberrant gene promoter methylation have emerged as potentially promising molecular biomarkers of lung carcinogenesis. Data from such studies relevant for emissions rich in PAHs are also summarized, although the exposure circumstances are not directly relevant to outdoor air pollution, in order to shed light on potential mechanisms of air pollution-related carcinogenesis.