Persistence of Bronchial Dysplasia Is Associated with Development of Invasive Squamous Cell Carcinoma

Biomarkers in Cancer Screening: Promises and Challenges in Cancer Early Detection

Cancer continues to be one the leading causes of death worldwide, primarily due to the late detection of the disease. Cancers detected at early stages may enable more effective intervention of the disease. However, most cancers lack well-established screening procedures except for cancers with an established early asymptomatic phase and clinically validated screening tests. There is a critical need to identify and develop assays/tools in conjunction with imaging approaches for precise screening and detection of the aggressive disease at an early stage. New developments in molecular cancer screening and early detection include germline testing, synthetic biomarkers, and liquid biopsy approaches.

Pre-clinical lung squamous cell carcinoma mouse models to identify novel biomarkers and therapeutic interventions

Primary lung carcinoma or lung cancer (LC) is classified into small-cell or non-small-cell (NSCLC) lung carcinoma. Lung squamous cell carcinoma (LSCC) is the second most common subtype of NSCLC responsible for 30% of all LCs, and its survival remains low with only 24% of patients living for five years or longer post-diagnosis primarily due to the advanced stage of tumors at the time of diagnosis. The pathogenesis of LSCC is still poorly understood and has hampered the development of effective diagnostics and therapies. This review highlights the known risk factors, genetic and epigenetic alterations, miRNA biomarkers linked to the development and diagnosis of LSCC and the lack of therapeutic strategies to target specifically LSCC. We will also discuss existing animal models of LSCC including carcinogen induced, transgenic and xenograft mouse models, and their advantages and limitations along with the chemopreventive studies and molecular studies conducted using them. The importance of developing new and improved mouse models will also be discussed that will provide further insights into the initiation and progression of LSCC, and enable the identification of new biomarkers and therapeutic targets.

Interrogating the precancerous evolution of pathway dysfunction in lung squamous cell carcinoma using XTABLE

Lung squamous cell carcinoma (LUSC) is a type of lung cancer with a dismal prognosis that lacks adequate therapies and actionable targets. This disease is characterized by a sequence of low- and high-grade preinvasive stages with increasing probability of malignant progression. Increasing our knowledge about the biology of these premalignant lesions (PMLs) is necessary to design new methods of early detection and prevention, and to identify the molecular processes that are key for malignant progression. To facilitate this research, we have designed XTABLE (Exploring Transcriptomes of Bronchial Lesions), an open-source application that integrates the most extensive transcriptomic databases of PMLs published so far. With this tool, users can stratify samples using multiple parameters and interrogate PML biology in multiple manners, such as two- and multiple-group comparisons, interrogation of genes of interests, and transcriptional signatures. Using XTABLE, we have carried out a comparative study of the potential role of chromosomal instability scores as biomarkers of PML progression and mapped the onset of the most relevant LUSC pathways to the sequence of LUSC developmental stages. XTABLE will critically facilitate new research for the identification of early detection biomarkers and acquire a better understanding of the LUSC precancerous stages.

PPARgamma agonism inhibits progression of premalignant lesions in a murine lung squamous cell carcinoma model

The N-nitroso-trischloroethylurea (NTCU)-induced mouse model of squamous lung carcinoma recapitulates human disease from premalignant dysplasia through invasive tumors, making it suitable for preclinical chemoprevention drug testing. Pioglitazone is a peroxisome proliferator-activated receptor γ (PPARγ) agonist shown to prevent lung tumors in preclinical models. We investigated pioglitazone's effect on lesion development and markers of potential preventive mechanisms in the NTCU model. Female FVB/N mice were exposed to vehicle, NTCU or NTCU + oral pioglitazone for 32 weeks. NTCU induces the appearance of basal cells in murine airways while decreasing/changing their epithelial cell makeup, resulting in development of bronchial dysplasia. H&E and keratin 5 (KRT5) staining were used to detect and grade squamous lesions in formalin fixed lungs. mRNA expression of epithelial to mesenchymal transition (EMT) markers and basal cell markers were measured by qPCR. Dysplasia persistence markers desmoglein 3 and polo like kinase 1 were measured by immunohistochemistry. Basal cell markers KRT14 and p63, club cell specific protein and ciliated cell marker acetylated tubulin were measured by immunofluorescence. Pioglitazone treatment significantly reduced squamous lesions and the presence of airway basal cells, along with increasing normal epithelial cells in the airways of NTCU-exposed mice. Pioglitazone also significantly influenced EMT gene expression to promote a more epithelial, and less mesenchymal, phenotype. Pioglitazone reduced the presence of squamous dysplasia and maintained normal airway cell composition. This work increases the knowledge of mechanistic pathways in PPARγ agonism for lung cancer interception and provides a basis for further investigation to advance this chemoprevention strategy.

Iloprost requires the Frizzled-9 receptor to prevent lung cancer

Prevention of premalignant lesion progression is a promising approach to reducing lung cancer burden in high-risk populations. Substantial preclinical and clinical evidence has demonstrated efficacy of the prostacyclin analogue iloprost for lung cancer chemoprevention. Iloprost activates peroxisome proliferator-activated receptor gamma (PPARG) to initiate chemopreventive signaling and in vitro, which requires the transmembrane receptor Frizzled9 (FZD9). We hypothesized a Fzd 9 -/- mouse would not be protected by iloprost in a lung cancer model. Fzd 9 -/- mice were treated with inhaled iloprost in a urethane model of lung adenoma. We found that Fzd 9 -/- mice treated with iloprost were not protected from adenoma development compared to wild-type mice nor did they demonstrate increased activation of iloprost signaling pathways. Our results established that iloprost requires FZD9 in vivo for lung cancer chemoprevention. This work represents a critical advancement in defining iloprost's chemopreventive mechanisms and identifies a potential response marker for future clinical trials.

Lung cancer: Premalignant biology and medical prevention

Lung cancer (both adenocarcinoma and squamous cell) progress through a series of pre-malignant histologic changes before the development of invasive disease. Each of these carcinogenic cascades is defined by genetic and epigenetic alterations in pulmonary epithelial cells. Additionally, alterations in the immune response, progenitor cell function, mutational burden, and microenvironmental mediated survival of mutated clones contribute to the risk of pre-malignant lesions progressing to cancer. Medical preventions studies have been completed and current and future trials are informed by the improved understanding of pre-malignancy. This will lead to precision chemoprevention trials based on lesional biology and histologic characteristics.

Elevated T cell repertoire diversity is associated with progression of lung squamous cell premalignant lesions

Objective

The immune response to invasive carcinoma has been the focus of published work, but little is known about the adaptive immune response to bronchial premalignant lesions (PMLs), precursors of lung squamous cell carcinoma. This study was designed to characterize the T cell receptor (TCR) repertoire in PMLs and its association with clinical, pathological, and molecular features.

Methods

Endobronchial biopsies (n=295) and brushings (n=137) from high-risk subjects (n=50), undergoing lung cancer screening at approximately 1-year intervals via autofluorescence bronchoscopy and CT, were profiled by RNA-seq. We applied the TCR Repertoire Utilities for Solid Tissue/Tumor tool to the RNA-seq data to identify TCR CDR3 sequences across all samples. In the biopsies, we measured the correlation of TCR diversity with previously derived immune-associated PML transcriptional signatures and PML outcome. We also quantified the spatial and temporal distribution of shared and clonally expanded TCRs. Using the biopsies and brushes, the ratio of private (ie, found in one patient only) and public (ie, found in two or more patients) TCRs was quantified, and the CDR3 sequences were compared with those found in curated databases with known antigen specificities.

Results

We detected 39,303 unique TCR sequences across all samples. In PML biopsies, TCR diversity was negatively associated with a transcriptional signature of T cell mediated immune activation (p=4e-4) associated with PML outcome. Additionally, in lesions of the proliferative molecular subtype, TCR diversity was decreased in regressive versus progressive/persistent PMLs (p=0.045). Within each patient, TCRs were more likely to be shared between biopsies sampled at the same timepoint than biopsies sampled at the same anatomic location at different times. Clonally expanded TCRs, within a biopsied lesion, were more likely to be expanded at future time points than non-expanded clones. The majority of TCR sequences were found in a single sample, with only 3396 (8.6%) found in more than one sample and 1057 (2.7%) found in two or more patients (ie, public); however, when compared with a public database of CDR3 sequences, 4543 (11.6%) of TCRs were identified as public. TCRs with known antigen specificities were enriched among public TCRs (p<0.001).

Conclusions

Decreased TCR diversity may reflect nascent immune responses that contribute to PML elimination. Further studies are needed to explore the potential for immunoprevention of PMLs.

Long-term Lung Cancer Risk Associated with Sputum Atypia: A 27-Year Follow-up Study of an Occupational Lung Screening Cohort in Yunnan, China

BACKGROUND

Sputum cytologic atypia is associated with increased lung cancer risk. However, little is known about the long-term magnitude and temporal trend of this risk.

METHODS

An extended follow-up was conducted in a prospective screening cohort among occupational tin miners in Yunnan, China. Sputum samples were collected prospectively at baseline and 7 annual screenings since enrollment. The associations between sputum cytologic results from baseline screening, the first 4 consecutive rounds of sputum screening, and lung cancer risk were analyzed by time-varying covariate Cox regression model.

RESULTS

A moderate or worse cytologic result was associated with a significantly increased lung cancer risk. This relative hazard significantly decreased over time. Compared with negative screening results, the adjusted hazard ratios of baseline-moderate or worse atypia, at least one moderate or worse atypia in the first 4 consecutive screening rounds during the first 10 years of follow-up were 3.11 [95% confidence interval (CI): 2.37-4.07], 3.25 (95% CI: 2.33-4.54) respectively. This association was stronger for persistent atypia (adjusted hazard ratio = 17.55, 95% CI: 8.32-37.03); atypia identified in the recent screening rounds (adjusted HR = 4.14, 95% CI: 2.70-6.35), and those were old in age, had higher level of smoking, occupational radon, and arsenic exposure. In terms of histology, this increased risk was significant for squamous cell carcinoma and small cell lung cancer.

CONCLUSIONS

Although decreasing over time, an increased lung cancer risk concerning moderate or worse sputum atypia can continue at least for 10 years.

IMPACT

Sputum atypia might be helpful for identifying high-risk individuals for screening, surveillance, or chemoprevention of lung cancer.

Spontaneous regression of incidentally diagnosed bronchial squamous cell lung carcinoma after severe bronchitis: A case report

Spontaneous regression of lung cancer is exceptionally rare. But there have been several intriguing cases reported in early and even advanced stages of lung cancer. Although the exact mechanism remains to be elucidated, the inflammation and immunologic response have been suggested as one of the means of spontaneous regression. Chronic inflammation is generally known to induce and aggravate tumorigenesis, but the relationship between cancer and inflammation highly depends on the contexts. Here, we present a case of a 60-year-old male ex-smoker who complained of recurrent hemoptysis, cough, and purulent sputum. The initial chest CT scan revealed diffuse bronchial thickening and an endobronchial mass-like lesion in the left lingular segment. The bronchoscopic and pathological findings also suggested a diagnosis of squamous cell carcinoma with severe mucosal inflammation. He was treated with antibiotics for the bronchitis during the first 1 week and his symptoms markedly improved. After 3 weeks, he underwent a follow-up examination. Chest computed tomography and bronchoscopy revealed the significant improvement of the bronchial narrowing and mucosal edema. Biopsy was performed several times around the lesion where the tissue was initially taken. However, the pathological results showed only chronic inflammation of bronchi, not cancer cells. Fortunately, there was no recurrence of lung cancer in follow-up chest computed tomography or bronchoscopy for almost 5 years. In this case, the incidentally diagnosed bronchial squamous cell carcinoma disappeared after severe inflammatory reaction of the bronchial wall. The clinician should remind the risk of early lung cancer accompanied with bronchitis in high-risk patients of lung cancer and also be aware that although it is very rare, the lesions could spontaneously regress.

Aberrant epithelial polarity cues drive the development of precancerous airway lesions

Molecular events that drive the development of precancerous lesions in the bronchial epithelium, which are precursors of lung squamous cell carcinoma (LUSC), are poorly understood. We demonstrate that disruption of epithelial cellular polarity, via the conditional deletion of the apical determinant Crumbs3 (Crb3), initiates and sustains precancerous airway pathology. The loss of Crb3 in adult luminal airway epithelium promotes the uncontrolled activation of the transcriptional regulators YAP and TAZ, which stimulate intrinsic signals that promote epithelial cell plasticity and paracrine signals that induce basal-like cell growth. We show that aberrant polarity and YAP/TAZ-regulated gene expression associates with human bronchial precancer pathology and disease progression. Analyses of YAP/TAZ-regulated genes further identified the ERBB receptor ligand Neuregulin-1 (NRG1) as a key transcriptional target and therapeutic targeting of ERBB receptors as a means of preventing and treating precancerous cell growth. Our observations offer important molecular insight into the etiology of LUSC and provides directions for potential interception strategies of lung cancer.

Immune Escape Is an Early Event in Pre-Invasive Lesions of Lung Squamous Cell Carcinoma

Bronchial dysplasia is the pre-neoplastic lesion recognized for invasive squamous cell carcinoma. The mechanisms leading to invasive squamous cell carcinoma for this lesion are not fully known. Programmed Death-Ligand 1 (PD-L1) expression by the bronchial dysplasia neoplastic epithelium might suggest a response to immunotherapy. The objective of this work is to further characterize PD-L1 and CD8 expression in bronchial dysplasia and bronchial metaplasia compared to normal bronchial epithelium. Immunohistochemical analysis of PD-L1 and CD8 staining were characterized in bronchial dysplasia of 24 patients and correlated with clinical data. We also compared PD-L1 expression in dysplasia samples to 30 normal epithelium and 20 samples with squamous bronchial metaplasia. PD-L1 was never expressed in normal epithelium and in metaplastic epithelium whereas 37.5% of patients with bronchial dysplasia were stained by PD-L1 (p < 0.001). PD-L1 expression was not related to the degree of dysplasia or a medical history of invasive squamous cell carcinoma, while CD8 expression and its localization were related to medical history of squamous cell carcinoma (p = 0.044). Our results show that PD-L1 is expressed in roughly one third of patients with bronchial dysplasia and is not expressed in normal and metaplastic epithelium. This suggests that PD-L1 is expressed in preneoplastic lesions of squamous cell carcinoma.

Biomarkers of Potential Harm: Summary of an FDA-Sponsored Public Workshop

Introduction

Since 2009, the United States (US) Food and Drug Administration (FDA) Center for Tobacco Products (CTP) has had the authority to regulate the manufacture, distribution, and marketing of tobacco products in order to reduce the death and disease caused by tobacco use. Biomarkers could play an important role across a number of FDA regulatory activities, including assessing new and modified risk tobacco products and identifying and evaluating potential product standards.

Methods

On April 4-5, 2016, FDA/CTP hosted a public workshop focused on biomarkers of potential harm (BOPH) with participants from government, industry, academia, and other organizations. The workshop was divided into five sessions focused on: (1) overview of BOPH; (2) cardiovascular disease (CVD); (3) chronic obstructive pulmonary disease (COPD); (4) cancer; and (5) new areas of research.

Results and Conclusions

The deliberations from the workshop noted some promising BOPH but also highlighted the lack of systematic effort to identify BOPH that would have utility and validity for evaluating tobacco products. Research areas that could further strengthen the applicability of BOPH to tobacco regulatory science include the exploration of composite biomarkers as predictors of disease risk, "omics" biomarkers, and examining biomarkers using existing cohorts, surveys, and experimental studies.

Implications

This paper synthesizes the main findings from the 2016 FDA-sponsored workshop focused on BOPH and highlights research areas that could further strengthen the science around BOPH and their applicability to tobacco regulatory science.

Sequencing the Events That Mediate Progression of Premalignant Lung Lesions

Analysis of a large group of patients with multifocal premalignant disease by Krysan and colleagues in this issue of Cancer Research provides an informative view of the processes that may underlie progression of these lesions to invasive adenocarcinoma of the lung. The identification of the type and distribution of mutational changes reveals that common processes may be occurring within individuals but that these are generally unique between patients at risk for developing lung cancer. Furthermore, predicted neoantigens are identified and associated with characteristics of immune infiltrates supporting the role of alterations in adaptive immune surveillance in progression of these premalignant lesions. These findings provide critical insights that will help establish a foundation of knowledge for developing personalized prevention strategies with the potential to significantly impact overall mortality in lung cancer.See related article by Krysan et al., p. 5022.

A Pilot Study of a Grape Seed Procyanidin Extract for Lung Cancer Chemoprevention

Grape seed procyanidin extract (GSE) had been reported to exert antineoplastic properties in preclinical studies. A modified phase I, open-label, dose-escalation clinical study was conducted to evaluate the safety, tolerability, MTD, and potential chemopreventive effects of leucoselect phytosome (LP), a standardized GSE complexed with soy phospholipids to enhance bioavailability, in heavy active and former smokers. Eight subjects ages 46-68 years were enrolled into the study and treated with escalating oral doses of LP for 3 months. Bronchoscopies with bronchoalveolar lavage and bronchial biopsies were performed before and after 3 months of LP treatment. Hematoxylin and eosin stain for histopathology grading and IHC examination for Ki-67 proliferative labeling index (Ki-67 LI) were carried out on serially matched bronchial biopsy samples from each subject to determine responses to treatment. Two subjects were withdrawn due to issues unrelated to the study medication, and a total of 6 subjects completed the full study course. In general, 3 months of LP, reaching the highest dose per study protocol was well tolerated and no dosing adjustment was necessary. Such a treatment regimen significantly decreased bronchial Ki-67 LI by an average of 55% (P = 0.041), with concomitant decreases in serum miR-19a, -19b, and -106b, which were oncomirs previously reported to be downregulated by GSE, including LP, in preclinical studies. In spite of not reaching the original enrollment goal of 20, our findings nonetheless support the continued clinical translation of GSE as an antineoplastic and chemopreventive agent against lung cancer.

A Randomized Phase II Trial of Pioglitazone for Lung Cancer Chemoprevention in High-Risk Current and Former Smokers

Lung cancer chemoprevention, especially in high-risk former smokers, has great potential to reduce lung cancer incidence and mortality. Thiazolidinediones prevent lung cancer in preclinical studies, and diabetics receiving thiazolidinediones have lower lung cancer rates which led to our double-blind, randomized, phase II placebo-controlled trial of oral pioglitazone in high-risk current or former smokers with sputum cytologic atypia or known endobronchial dysplasia. Bronchoscopy was performed at study entry and after completing 6 months of treatment. Biopsies were histologically scored, and primary endpoint analysis tested worst biopsy scores (Max) between groups; Dysplasia index (DI) and average score (Avg) changes were secondary endpoints. Biopsies also received an inflammation score. The trial accrued 92 subjects (47 pioglitazone, 45 placebo), and 76 completed both bronchoscopies (39 pioglitazone, 37 placebo). Baseline dysplasia was significantly worse for current smokers, and 64% of subjects had mild or greater dysplasia at study entry. Subjects receiving pioglitazone did not exhibit improvement in bronchial dysplasia. Former smokers treated with pioglitazone exhibited a slight improvement in Max, while current smokers exhibited slight worsening. While statistically significant changes in Avg and DI were not observed in the treatment group, former smokers exhibited a slight decrease in both Avg and DI. Negligible Avg and DI changes occurred in current smokers. A trend toward decreased Ki-67 labeling index occurred in former smokers with baseline dysplasia receiving pioglitazone. While pioglitazone did not improve endobronchial histology in this high-risk cohort, specific lesions showed histologic improvement, and further study is needed to better characterize responsive dysplasia.

Molecular subtyping reveals immune alterations associated with progression of bronchial premalignant lesions

Bronchial premalignant lesions (PMLs) are precursors of lung squamous cell carcinoma, but have variable outcome, and we lack tools to identify and treat PMLs at risk for progression to cancer. Here we report the identification of four molecular subtypes of PMLs with distinct differences in epithelial and immune processes based on RNA-Seq profiling of endobronchial biopsies from high-risk smokers. The Proliferative subtype is enriched with bronchial dysplasia and exhibits up-regulation of metabolic and cell cycle pathways. A Proliferative subtype-associated gene signature identifies subjects with Proliferative PMLs from normal-appearing uninvolved large airway brushings with high specificity. In progressive/persistent Proliferative lesions expression of interferon signaling and antigen processing/presentation pathways decrease and immunofluorescence indicates a depletion of innate and adaptive immune cells compared with regressive lesions. Molecular biomarkers measured in PMLs or the uninvolved airway can enhance histopathological grading and suggest immunoprevention strategies for intercepting the progression of PMLs to lung cancer.

Prostacyclin and EMT Pathway Markers for Monitoring Response to Lung Cancer Chemoprevention

Lung cancer is the leading cause of cancer death worldwide and global burden could be reduced through targeted application of chemoprevention. The development of squamous lung carcinoma has been linked with persistent, high-grade bronchial dysplasia. Bronchial histology improved in former smokers in a chemoprevention trial with the prostacyclin analogue iloprost. Prostacyclin acts through peroxisome proliferator-activated receptor gamma (PPARγ) to reverse epithelial to mesenchymal transition and promote anticancer signaling. We hypothesized that the prostacyclin signaling pathway and EMT could provide response markers for prostacyclin chemoprevention of lung cancer. Human bronchial epithelial cells were treated with cigarette smoke condensate (CSC) or iloprost for 2 weeks, CSC for 16 weeks, or CSC for 4 weeks followed by 4 weeks of CSC and/or iloprost, and RNA was extracted. Wild-type or prostacyclin synthase transgenic mice were exposed to 1 week of cigarette smoke or one injection of urethane, and RNA was extracted from the lungs. We measured potential markers of prostacyclin and iloprost efficacy in these models. We identified a panel of markers altered by tobacco carcinogens and inversely affected by prostacyclin, including PPARγ, 15PGDH, CES1, COX-2, ECADHERIN, SNAIL, VIMENTIN, CRB3, MIR34c, and MIR221 These data introduce a panel of potential markers for monitoring interception of bronchial dysplasia progression during chemoprevention with prostacyclin. Chemoprevention is a promising approach to reduce lung cancer mortality in a high-risk population. Identifying markers for targeted use is critical for success in future clinical trials of prostacyclin for lung cancer chemoprevention. Cancer Prev Res; 11(10); 643-54. ©2018 AACR.

Altered Cell-Cycle Control, Inflammation, and Adhesion in High-Risk Persistent Bronchial Dysplasia

Persistent bronchial dysplasia is associated with increased risk of developing invasive squamous cell carcinoma (SCC) of the lung. In this study, we hypothesized that differences in gene expression profiles between persistent and regressive bronchial dysplasia would identify cellular processes that underlie progression to SCC. RNA expression arrays comparing baseline biopsies from 32 bronchial sites that persisted/progressed to 31 regressive sites showed 395 differentially expressed genes [ANOVA, FDR ≤ 0.05). Thirty-one pathways showed significantly altered activity between the two groups, many of which were associated with cell-cycle control and proliferation, inflammation, or epithelial differentiation/cell-cell adhesion. Cultured persistent bronchial dysplasia cells exhibited increased expression of Polo-like kinase 1 (PLK1), which was associated with multiple cell-cycle pathways. Treatment with PLK1 inhibitor induced apoptosis and G2-M arrest and decreased proliferation compared with untreated cells; these effects were not seen in normal or regressive bronchial dysplasia cultures. Inflammatory pathway activity was decreased in persistent bronchial dysplasia, and the presence of an inflammatory infiltrate was more common in regressive bronchial dysplasia. Regressive bronchial dysplasia was also associated with trends toward overall increases in macrophages and T lymphocytes and altered polarization of these inflammatory cell subsets. Increased desmoglein 3 and plakoglobin expression was associated with higher grade and persistence of bronchial dysplasia. These results identify alterations in the persistent subset of bronchial dysplasia that are associated with high risk for progression to invasive SCC. These alterations may serve as strong markers of risk and as effective targets for lung cancer prevention.Significance: Gene expression profiling of high-risk persistent bronchial dysplasia reveals changes in cell-cycle control, inflammatory activity, and epithelial differentiation/cell-cell adhesion that may underlie progression to invasive SCC. Cancer Res; 78(17); 4971-83. ©2018 AACR.

The Making of a PreCancer Atlas: Promises, Challenges, and Opportunities

Many cancers evolve from benign precancerous lesions and have a natural history of progression that provides a window of opportunity for intervention. The biological mechanisms underlying this evolutionary trajectory can only be truly understood through an extensive characterization of the molecular, cellular, and non-cellular properties of premalignant and malignant tumors, and must also recognize how the microenvironment (stromal cells, immune cells, and other types of cells) contributes to this evolution. We describe here the need to develop comprehensive molecular and cellular atlases for organ-specific premalignant lesions while capturing the spatial, structural, and functional changes over time that will provide a greater understanding of how premalignancy transitions to malignancy. The PreCancer Atlas (PCA) initiative, described in this Opinion, will address this need and aims to overcome the many challenges that currently plague the field. The hope is that PCAs will lead to the development of effective and timely interventions to prevent the development of invasive cancers.

Airway brushing as a new experimental methodology to detect airway gene expression signatures in mouse lung squamous cell carcinoma

As a consequence of 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 within a damaged epithelium containing mutations in oncogene or tumor suppressor genes. Unlike humans, whose airway field of injury associated with lung cancer has long been investigated with airway brushings obtained via bronchoscopy, no methods are available for similar studies in the mouse due to the small size of the murine airways. In this protocol, we describe a detailed method for performing airway brushing from a live mouse, which enables repeated sampling from the same mouse and thus, mimicking the bronchoscopy protocol used in humans. Using this approach in the N-nitroso-tris-chloroethylurea (NTCU)-induced mouse lung squamous cell carcinoma (SCC) model, we isolated airway epithelial cells with intact cell membrane structure and then performed transcriptome sequencing (RNA-Seq). We found activation of the PI3K signaling network to be the most significant in cytologically normal bronchial airway epithelial cells of mice with preneoplastic lung SCC lesions. Prolonged exposure to NTCU also induced activation of NF-kappaB (NFƙB), the downstream pathway of PI3K; this NTCU-induced lung SCC progression can be reversed by blocking the NFƙB pathway.

Gene methylation biomarkers in sputum as a classifier for lung cancer risk

CT screening for lung cancer reduces mortality, but will cost Medicare ∼2 billion dollars due in part to high false positive rates. Molecular biomarkers could augment current risk stratification used to select smokers for screening. Gene methylation in sputum reflects lung field cancerization that remains in lung cancer patients post-resection. This population was used in conjunction with cancer-free smokers to evaluate classification accuracy of a validated eight-gene methylation panel in sputum for cancer risk. Sputum from resected lung cancer patients (n=487) and smokers from Lovelace (n=1380) and PLuSS (n=718) cohorts was studied for methylation of an 8-gene panel. Area under a receiver operating characteristic curve was calculated to assess the prediction performance in logistic regressions with different sets of variables. The prevalence for methylation of all genes was significantly increased in the ECOG-ACRIN patients compared to cancer-free smokers as evident by elevated odds ratios that ranged from 1.6 to 8.9. The gene methylation panel showed lung cancer prediction accuracy of 82–86% and with addition of clinical variables improved to 87–90%. With sensitivity at 95%, specificity increased from 25% to 54% comparing clinical variables alone to their inclusion with methylation. The addition of methylation biomarkers to clinical variables would reduce false positive screens by ruling out one-third of smokers eligible for CT screening and could increase cancer detection rates through expanding risk assessment criteria.

Detecting the Presence and Progression of Premalignant Lung Lesions via Airway Gene Expression

Purpose: Lung cancer is the leading cause of cancer-related death in the United States. The molecular events preceding the onset of disease are poorly understood, and no effective tools exist to identify smokers with premalignant lesions (PMLs) that will progress to invasive cancer. Prior work identified molecular alterations in the smoke-exposed airway field of injury associated with lung cancer. Here, we focus on an earlier stage in the disease process leveraging the airway field of injury to study PMLs and its utility in lung cancer chemoprevention.Experimental Design: Bronchial epithelial cells from normal appearing bronchial mucosa were profiled by mRNA-Seq from subjects with (n = 50) and without (n = 25) PMLs. Using surrogate variable and gene set enrichment analysis, we identified genes, pathways, and lung cancer-related gene sets differentially expressed between subjects with and without PMLs. A computational pipeline was developed to build and test a chemoprevention-relevant biomarker.Results: We identified 280 genes in the airway field associated with the presence of PMLs. Among the upregulated genes, oxidative phosphorylation was strongly enriched, and IHC and bioenergetics studies confirmed pathway findings in PMLs. The relationship between PMLs and squamous cell carcinomas (SCC) was also confirmed using published lung cancer datasets. The biomarker performed well predicting the presence of PMLs (AUC = 0.92, n = 17), and changes in the biomarker score associated with progression/stability versus regression of PMLs (AUC = 0.75, n = 51).Conclusions: Transcriptomic alterations in the airway field of smokers with PMLs reflect metabolic and early lung SCC alterations and may be leveraged to stratify smokers at high risk for PML progression and monitor outcome in chemoprevention trials. Clin Cancer Res; 23(17); 5091-100. ©2017 AACR.

Prostacyclin reverses the cigarette smoke-induced decrease in pulmonary Frizzled 9 expression through miR-31

Half of lung cancers are diagnosed in former smokers, leading to a significant treatment burden in this population. Chemoprevention in former smokers using the prostacyclin analogue iloprost reduces endobronchial dysplasia, a premalignant lung lesion. Iloprost requires the presence of the WNT receptor Frizzled 9 (Fzd9) for inhibition of transformed growth in vitro. To investigate the relationship between iloprost, cigarette smoke, and Fzd9 expression, we used human samples, mouse models, and in vitro studies. Fzd9 expression was low in human lung tumors and in progressive dysplasias. In mouse models and in vitro studies, tobacco smoke carcinogens reduced expression of Fzd9 while prostacyclin maintained or increased expression. Expression of miR-31 repressed Fzd9 expression, which was abrogated by prostacyclin. We propose a model where cigarette smoke exposure increases miR-31 expression, which leads to decreased Fzd9 expression and prevents response to iloprost. When smoke is removed miR-31 is reduced, prostacyclin can increase Fzd9 expression, and progression of dysplasia is inhibited. Fzd9 and miR-31 are candidate biomarkers for precision application of iloprost and monitoring of treatment progress. As we continue to investigate the mechanisms of prostacyclin chemoprevention and identify biomarkers for its use, we will facilitate clinical trials and speed implementation of this valuable prevention approach.

Low Prevalence of High-Grade Lesions Detected With Autofluorescence Bronchoscopy in the Setting of Lung Cancer Screening in the Pan-Canadian Lung Cancer Screening Study

BACKGROUND

Lung cancer screening with low-dose CT (LDCT) scan has been demonstrated to reduce lung cancer mortality. Preliminary reports suggested that up to 20% of lung cancers may be CT scan occult but detectable by autofluorescence bronchoscopy (AFB). We evaluated the prevalence of CT scan occult, invasive, and high-grade preinvasive lesions in high-risk participants undergoing screening for lung cancer.

METHODS

The first 1,300 participants from seven centers in the Pan-Canadian Early Detection of Lung Cancer Study who had ≥ 2% lung cancer risk over 5 years were invited to have an AFB in addition to a LDCT scan. We determined the prevalence of CT scan and AFB abnormalities and analyzed the association between selected predictor variables and preinvasive lesions plus invasive cancer.

RESULTS

A total of 776 endobronchial biopsies were performed in 333 of 1,300 (25.6%) participants. Dysplastic or higher-grade lesions were detected in 5.3% of the participants (n = 68; mild dysplasia: n = 36, moderate dysplasia: n = 25, severe dysplasia: n = 3, carcinoma in situ [CIS]: n = 1, and carcinoma: n = 4). Only one typical carcinoid tumor and one CIS lesion were detected by AFB alone, for a rate of CT scan occult cancer of 0.15% (95% CI, 0.0%-0.6%). Fifty-six prevalence lung cancers were detected by LDCT scan (4.3%). The only independent risk factors for finding of dysplasia or CIS on AFB were smoking duration (OR, 1.05; 95% CI, 1.02-1.07) and FEV₁ percent predicted (OR, 0.99; 95% CI, 0.98-0.99).

CONCLUSIONS

The addition of AFB to LDCT scan in a high lung cancer risk cohort detected too few CT occult cancers (0.15%) to justify its incorporation into a lung cancer screening program.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00751660; URL: www.clinicaltrials.gov.

The Case for a Pre-Cancer Genome Atlas (PCGA)

Understanding the earliest molecular and cellular events associated with cancer initiation remains a key bottleneck to transforming our approach to cancer prevention and detection. While TCGA has provided unprecedented insights into the genomic events associated with advanced stage cancer, there have been few studies comprehensively profiling premalignant and early-stage disease or elucidating the role of the microenvironment in premalignancy and tumor initiation. In this article, we make a call for development of a "Pre-Cancer Genome Atlas (PCGA)," a concerted initiative to characterize the molecular alterations in premalignant lesions and the corresponding changes in the microenvironment associated with progression to invasive carcinoma. This initiative will require a multicenter coordinated effort to comprehensively profile (cellular and molecular) premalignant lesions and their corresponding "field of injury" collected longitudinally as the lesion progresses towards or regresses from frank malignancy across multiple tumor types. Genomic characterization of alterations in premalignant lesions and their microenvironment, for both bulk tissue and single cells, will enable development of biomarkers for early detection and risk stratification as well as allow for the development of novel targeted cancer interception strategies. The multi-institutional and multidisciplinary collaborative "big-data" effort underlying the PCGA will help usher in a new era of precision medicine for cancer detection and prevention.