Adenoma Formation Research Articles

AIMP2 Controls Intestinal Stem Cell Compartments and Tumorigenesis by Modulating Wnt/β-Catenin Signaling.

Wnt/β-catenin (CTNNB1) signaling is crucial for the proliferation and maintenance of intestinal stem cells (ISC), but excessive activation leads to ISC expansion and eventually colorectal cancer. Thus, negative regulators are required to maintain optimal levels of Wnt/β-catenin signaling. Aminoacyl-tRNA synthetase-interacting multifunctional proteins (AIMP) function in protein synthesis, but have also been implicated in signaling cascades affecting angiogenesis, immunity, and apoptosis. In this study, we investigated the relationship between AIMP2 and Wnt/β-catenin signaling in a murine model of intestinal homeostasis and tumorigenesis. Hemizygous deletion of Aimp2 resulted in enhanced Wnt/β-catenin signaling, increased proliferation of cryptic epithelial cells, and expansion of ISC compartments. In an Apc(Min/+) background, Aimp2 hemizygosity increased adenoma formation. Mechanistically, AIMP2 disrupted the interaction between AXIN and Dishevelled-1 (DVL1) to inhibit Wnt/β-catenin signaling by competing with AXIN. Furthermore, AIMP2 inhibited intestinal organoid formation and growth by suppressing Wnt/β-catenin signaling in an Aimp2 gene dosage-dependent manner. Collectively, our results showed that AIMP2 acts as a haploinsufficient tumor suppressor that fine-tunes Wnt/β-catenin signaling in the intestine, illuminating the regulation of ISC abundance and activity. Cancer Res; 76(15); 4559-68. ©2016 AACR.

Abstract LB-168: MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer

Abstract Lung cancer is the leading cause of cancer deaths and yet the genes that drive this malignancy are not entirely known. MicroRNA (miRNA) are important regulators of gene expression and aberrant miRNA expression has been linked to lung oncogenesis; however, little known about their contribution in tumor initiation. We’ve determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. miR-31 promotes lung cell proliferation and adenocarcinoma growth in vivo. We also developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. We identified 6 negative regulators of RAS/MAPK signaling (RASA1, SPRED1, SPRED2, SPRY1, SPRY3, SPRY4) as direct targets of miR-31. Analysis of human lung adenocarcinoma revealed that high miR-31 expression correlated to decreased target mRNA expression. miR-31 overexpression in lung cells results in increased RAS signaling and pharmacologic inhibition of MEK ablates miR-31 induced lung cell proliferation. Induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. Our study demonstrates for the first time that a miRNA can drive an epithelial cancer. Specifically we identified miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and demonstrate that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling. Citation Format: Mick D. Edmonds, Kelli L. Boyd, Tamara K. Moyo, Ramkrishna Mitra, Robert J. Duszynski, Maria P. Arrate, Xi Chen, Zhongming Zhao, Timothy S. Blackwell, Christine M. Eischen. MicroRNA-31 initiates lung tumorigenesis and promotes mutant KRAS-driven lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-168.

Increased variability in Apc(Min)/+ intestinal tissue can be measured with microultrasound.

Altered tissue structure is a feature of many disease states and is usually measured by microscopic methods, limiting analysis to small areas. Means to rapidly and quantitatively measure the structure and organisation of large tissue areas would represent a major advance not just for research but also in the clinic. Here, changes in tissue organisation that result from heterozygosity in Apc, a precancerous situation, are comprehensively measured using microultrasound and three-dimensional high-resolution microscopy. Despite its normal appearance in conventionally examined cross-sections, both approaches revealed a significant increase in the variability of tissue organisation in Apc heterozygous tissue. These changes preceded the formation of aberrant crypt foci or adenoma. Measuring these premalignant changes using microultrasound provides a potential means to detect microscopically abnormal regions in large tissue samples, independent of visual examination or biopsies. Not only does this provide a powerful tool for studying tissue structure in experimental settings, the ability to detect and monitor tissue changes by microultrasound could be developed into a powerful adjunct to screening endoscopy in the clinic.

DNA Hypomethylation Contributes to Genomic Instability and Intestinal Cancer Initiation.

Intestinal cancer is a heterogeneous disease driven by genetic mutations and epigenetic changes. Approximately 80% of sporadic colorectal cancers are initiated by mutation and inactivation of the adenomatous polyposis coli (APC) gene, which results in unrestrained intestinal epithelial growth and formation of adenomas. Aberrant DNA methylation promotes cancer progression by the inactivation of tumor suppressor genes via promoter methylation. In addition, global DNA hypomethylation is often seen before the formation of adenomas, suggesting that it contributes to neoplastic transformation. Previous studies employed mice with a hypomorphic mutation in DNA methyltransferase 1 (Dnmt1), which exhibited constitutive global DNA hypomethylation and decreased tumorigenesis in the Apc(Min/+) mouse model of intestinal cancer. However, the consequences of intestinal epithelial-specific acute hypomethylation during Apc(Min/+) tumor initiation have not been reported. Using temporally controlled intestinal epithelial-specific gene ablation, we show that total loss of Dnmt1 in the Apc(Min/+) mouse model of intestinal cancer causes accelerated adenoma initiation. Deletion of Dnmt1 precipitates an acute response characterized by hypomethylation of repetitive elements and genomic instability, which surprisingly is followed by remethylation with time. Two months post-Dnmt1 ablation, mice display increased macroadenoma load, consistent with a role for Dnmt1 and DNA methylation in maintaining genomic stability. These data suggest that DNA hypomethylation plays a previously unappreciated role in intestinal adenoma initiation. Cancer Prev Res; 9(7); 534-46. ©2016 AACRSee related article by Lee and Laird, p. 509.

All Things in Moderation: Prevention of Intestinal Adenomas by DNA Hypomethylation.

DNA hypomethylation can prevent intestinal tumorigenesis, presumably by reducing epigenetic silencing of tumor-suppressor genes. A study in this issue by Sheaffer and colleagues challenges this notion by showing that severe DNA hypomethylation by tissue-specific Dnmt1 knockout can actually promote intestinal adenoma formation. Cancer Prev Res; 9(7); 509-11. ©2016 AACRSee related article by Sheaffer, et al., p. 534.

Block-Centric Visualization Of Histological Whole Slide Images With Application To Revealing Growth-Patterns Of Early Colorectal Adenomas And Aberrant Crypt Foci

Introduction/ Background Comfortable navigation through diagnostic images is a prospective challenge for the acceptance of virtual microscopy applications in routine pathology [1],[2]. Tracing different regions of interest through multiple sections on one or several slides is a typical task in diagnostic slide examination. This laborious and time-consuming co-localization is currently executed by pathologists. Retaining the relative positions of tissue structures while alternating between multiple slides is still not feasible in a satisfactory manner in conventional nor virtual microscopy. Aims To address this issue we present a more comfortable and intuitive method to read slides using computer-assisted navigation. Furthermore, we demonstrate the strengths of our method by applying it to large series of serial colorectal tissue sections, creating new kinds of visualizations of different adenomatous mucosal architectures in human tissue, while looking for human correlates of lesions recently described in mice [3]. Methods Histological images contain multiple distortions from different sources in the laboratory and digitalization process. An interconnection model was created to describe distortions by several layers, providing a normalized tissue representation. Layers were associated with specific distortions with each layer serving as a new level of abstraction. The first layers enabled a coarse alignment of tissue sections. Further alignment is achieved by piecewise, multi-resolution, SIFT-based [4] correspondence extraction and refinement. Inside the convex hull of all fiducial points local affine transformations were applied whereas a global affine transformation was used on the outside. Animated stacks were generated for regions of interest using local rigid transformations to preserve exact morphological coherences. For subsequent creation of 3D models, the relevant histological objects within these images were annotated by pathologists, partly using computer assisted segmentation based on active contours [5]. These annotations were used subsequently to create simplified 3D models by applying VTK [6]. Results The presented methods provide an efficient means to retrieve correspondences and additional spatial information from serial sections of histological slides. They also show good applicability for specimen from different origin. Alignment methods can be applied to generate block-centric visualizations such as parallel and transparent viewing of multiple stains. Moreover, the generated stack videos and 3D models demonstrate the very good accuracy of section alignment even in large series. The visualizations enable pathologists and researchers to grasp the 3D structural relationships in the tissue at a glance, providing an excellent tool to communicate more complex histomorphological findings. Interestingly, we see two kinds of tubular adenomas, which could imply multiple ways to tubular adenoma formation in FAP-patients, possibly akin to the recent observations in mice [3].

Genomic Landscape of Colorectal Mucosa and Adenomas.

The molecular basis of the adenoma-to-carcinoma transition has been deduced using comparative analysis of genetic alterations observed through the sequential steps of intestinal carcinogenesis. However, comprehensive genomic analyses of adenomas and at-risk mucosa are still lacking. Therefore, our aim was to characterize the genomic landscape of colonic at-risk mucosa and adenomas. We analyzed the mutation profile and copy number changes of 25 adenomas and adjacent mucosa from 12 familial adenomatous polyposis patients using whole-exome sequencing and validated allelic imbalances (AI) in 37 adenomas using SNP arrays. We assessed for evidence of clonality and performed estimations on the proportions of driver and passenger mutations using a systems biology approach. Adenomas had lower mutational rates than did colorectal cancers and showed recurrent alterations in known cancer driver genes (APC, KRAS, FBXW7, TCF7L2) and AIs in chromosomes 5, 7, and 13. Moreover, 80% of adenomas had somatic alterations in WNT pathway genes. Adenomas displayed evidence of multiclonality similar to stage I carcinomas. Strong correlations between mutational rate and patient age were observed in at-risk mucosa and adenomas. Our data indicate that at least 23% of somatic mutations are present in at-risk mucosa prior to adenoma initiation. The genomic profiles of at-risk mucosa and adenomas illustrate the evolution from normal tissue to carcinoma via greater resolution of molecular changes at the inflection point of premalignant lesions. Furthermore, substantial genomic variation exists in at-risk mucosa before adenoma formation, and deregulation of the WNT pathway is required to foster carcinogenesis. Cancer Prev Res; 9(6); 417-27. ©2016 AACR.

P62, Upregulated during Preneoplasia, Induces Hepatocellular Carcinogenesis by Maintaining Survival of Stressed HCC-Initiating Cells

p62 is a ubiquitin-binding autophagy receptor and signaling protein that accumulates in premalignant liver diseases and most hepatocellular carcinomas (HCCs). Although p62 was proposed to participate in the formation of benign adenomas in autophagy-deficient livers, its role in HCC initiation was not explored. Here we show that p62 is necessary and sufficient for HCC induction in mice and that its high expression in non-tumor human liver predicts rapid HCC recurrence after curative ablation. High p62 expression is needed for activation of NRF2 and mTORC1, induction of c-Myc, and protection of HCC-initiating cells from oxidative stress-induced death.

Dietary fat overcomes the protective activity of thrombospondin-1 signaling in the ApcMin/+ model of colon cancer

Thrombospondin 1 is a glycoprotein that regulates cellular phenotype through interactions with its cellular receptors and extracellular matrix-binding partners. Thrombospondin 1 locally regulates angiogenesis and inflammatory responses that contribute to colorectal carcinogenesis in ApcMin/+ mice. The ability of thrombospondin 1 to regulate responses of cells and tissues to a variety of stresses suggested that loss of thrombospondin 1 may also have broader systemic effects on metabolism to modulate carcinogenesis. ApcMin/+:Thbs1−/− mice exhibited decreased survival and higher tumor multiplicities in the small and large intestine relative to ApcMin/+ mice when fed a low (5%) fat western diet. However, the protective effect of endogenous thrombospondin 1 was lost when the mice were fed a western diet containing 21% fat. Biochemical profiles of liver tissue identified systemic metabolic changes accompanying the effects of thrombospondin 1 and dietary lipid intake on tumorigenesis. A high-fat western diet differentially regulated elements of amino acid, energy and lipid metabolism in ApcMin/+:Thbs1−/− mice relative to ApcMin/+:Thbs1+/+mice. Metabolic changes in ketone body and tricarboxylic acid cycle intermediates indicate functional interactions between Apc and thrombospondin 1 signaling that control mitochondrial function. The cumulative diet-dependent differential changes observed in ApcMin/+:Thbs1−/− versus ApcMin/+ mice include altered amino acid and lipid metabolism, mitochondrial dysfunction, eicosanoids and ketone body formation. This metabolic profile suggests that the protective role of thrombospondin 1 to decrease adenoma formation in ApcMin/+ mice results in part from improved mitochondrial function.

Multiple roles for the hippo effector yap in gut regeneration and cancer initiation

ABSTRACTThe Hippo signaling effector Yes-associated protein (Yap) is known for its potent control of tissue growth. Our recent work now shows that Yap promotes regeneration in the intestine by reprogramming intestinal stem cells and blocking their terminal differentiation. Similarly, in tumor-initiating cells Yap regenerative signaling synergizes with Wnt activation to drive adenoma formation.

The Co-regulatory Role of 5-Lipoxygenase and Cyclooxygenase-2 in the Carcinogenesis and their Promotion by Cigarette Smoking in Colons.

The arachidonic acid metabolizing enzymes, cyclooxygenase-2 (COX-2) and 5- lipoxygenase (5-LOX), are both highly expressed during the carcinogenesis in colons. Cigarette smoking promotes these carcinogenic processes at the early stage during adenoma formation. In this article, the involvement of COX-2 and 5-LOX, alongside with the dual COX/5-LOX inhibitors in colorectal cancer development is introduced. The co-regulation of 5-LOX and COX-2 in colon cancer growth and its relationship with cigarette smoke and hyaluronic acid-CD44v6 is also described. It is envisaged that dual inhibition of 5-LOX/COX could be the most promising therapeutic option for the treatment of colorectal cancer in humans.

Combined changes in Wnt signaling response and contact inhibition induce altered proliferation in radiation-treated intestinal crypts.

Curative intervention is possible if colorectal cancer is identified early, underscoring the need to detect the earliest stages of malignant transformation. A candidate biomarker is the expanded proliferative zone observed in crypts before adenoma formation, also found in irradiated crypts. However, the underlying driving mechanism for this is not known. Wnt signaling is a key regulator of proliferation, and elevated Wnt signaling is implicated in cancer. Nonetheless, how cells differentiate Wnt signals of varying strengths is not understood. We use computational modeling to compare alternative hypotheses about how Wnt signaling and contact inhibition affect proliferation. Direct comparison of simulations with published experimental data revealed that the model that best reproduces proliferation patterns in normal crypts stipulates that proliferative fate and cell cycle duration are set by the Wnt stimulus experienced at birth. The model also showed that the broadened proliferation zone induced by tumorigenic radiation can be attributed to cells responding to lower Wnt concentrations and dividing at smaller volumes. Application of the model to data from irradiated crypts after an extended recovery period permitted deductions about the extent of the initial insult. Application of computational modeling to experimental data revealed how mechanisms that control cell dynamics are altered at the earliest stages of carcinogenesis.

469 Heterozygosity of UPR Repressor Grp78 Reduces Intestinal Stem Cell Regeneration Potential and Protects Against Adenoma Formation

469 Heterozygosity of UPR Repressor Grp78 Reduces Intestinal Stem Cell Regeneration Potential and Protects Against Adenoma Formation

Mo1738 Risk of Adenoma Formation in Solid Organ Transplantation: Role of Immunosuppression

Mo1738 Risk of Adenoma Formation in Solid Organ Transplantation: Role of Immunosuppression

Reduction of Murine Colon Tumorigenesis Driven by Enterotoxigenic Bacteroides fragilis Using Cefoxitin Treatment.

Chronic inflammation and composition of the colon microbiota have been associated with colorectal cancer in humans. The human commensal enterotoxigenic Bacteroides fragilis (ETBF) is linked to both inflammatory bowel disease and colorectal cancer and, in our murine model, causes interleukin 17A (IL-17A)-dependent colon tumors. In these studies, we hypothesized that persistent colonization by ETBF is required for tumorigenesis. We established a method for clearing ETBF in mice, using the antibiotic cefoxitin. Multiple intestinal neoplasia mice were colonized with ETBF for the experiment duration or were cleared of infection after 5 or 14 days. Gross tumors and/or microadenomas were then evaluated. In parallel, IL-17A expression was evaluated in wild-type littermates. Cefoxitin treatment resulted in complete and durable clearance of ETBF colonization. We observed a stepwise increase in median colon tumor numbers as the duration of ETBF colonization increased before cefoxitin treatment. ETBF eradication also significantly decreased mucosal IL-17A expression. The timing of ETBF clearance profoundly influences colon adenoma formation, defining a period during which the colon is susceptible to IL-17A-dependent tumorigenesis in this murine model. This model system can be used to study the microbiota-dependent and molecular mechanisms contributing to IL-17A-dependent colon tumor initiation.

Colonoscopic screening shows increased early incidence and progression of adenomas in cystic fibrosis

BackgroundColorectal cancer is an emerging problem in cystic fibrosis (CF). The goal of this study was to evaluate adenoma detection by systematic colonoscopic screening and surveillance. MethodsWe analyzed prospectively collected results of colonoscopies initiated at age 40years from 88 CF patients at a single Cystic Fibrosis Center. We also reviewed results of diagnostic colonoscopies from 27 patients aged 30–39years performed during the same time period at the Center. ResultsThe incidence of polyp detection increased markedly after age 40 in CF patients. Greater than 50% were found to have adenomatous polyps; approximately 25% had advanced adenomas as defined by size and/or histopathology; 3% were found to have colon cancer. Multivariate analysis demonstrated specific risk factors for adenoma formation and progression. ConclusionsEarly screening and more frequent surveillance should be considered in patients with CF due to early incidence and progression of adenomas in this patient population.

Low rate of advanced adenoma formation during a 5-year colonoscopy surveillance period after adequate polypectomy of non-advanced adenoma.

Patients with non-advanced adenoma (NAA) underwent surveillance colonoscopy at intervals shorter than the interval recommended by the guidelines. We aimed to assess the incidence of recurrent advanced adenoma (AA) over a 5-year period and to identify risk factors for recurrence. Patients with and without NAA identified at baseline colonoscopy who had had at least two colonoscopy examinations during the subsequent 5 years were included in the study. Data on the patients' demographics and colorectal findings were extracted from a specially designed colonoscopy database. The primary outcome was the finding of recurrent AA formation. Multivariate analysis was used to identify factors that predict subsequent AA formation at surveillance colonoscopy. Among 43 155 colonoscopy procedures, 828 cases were identified with NAA (374) and without an adenoma (454). Forty-eight (51.1%) of 94 received a follow-up colonoscopy within 1 year due to an inadequate baseline colonoscopy. Patients with NAA at baseline had a low incidence of AA at an interval of 1-5 years which was not statistically different from patients without adenoma formation at the initial baseline colonoscopy (1.5% vs 2.2%, P = 0.51). The incidence of AA at follow-up colonoscopy performed at 1-3 years and 3-5 years in patients with a baseline NAA was 1.7% and 1.4% (P = 0.59). Age over 50 years and male gender were independent risk factors for AA recurrence within 5 years. Surveillance colonoscopy within 5 years is of little benefit to patients who had an adequate polypectomy of an NAA at baseline. Too frequent reexamination due to concerns about AA recurrence should be avoided.

Age-related Qualitative Histological and Quantitative Stereological Changes in the Equine Pituitary

The aim of this study was to characterize the age-related morphological changes in the equine pituitary and to identify features that allow distinction between pituitary pars intermedia dysfunction (PPID)-associated and non-functional/age-associated pars intermedia (PI) adenoma. Pituitary glands of all horses submitted for necropsy examination at the Institute of Veterinary Pathology, Ludwig Maximilians University Munich, between 2008 and 2012 were examined. The pituitary glands of 124 horses were weighed, cut into ∼2mm slices and examined histologically. A slightly modified grading scheme (grades 1-5) was applied to evaluate histological alterations of the PI semiquantitatively. The volume fractions and total volumes of the three pituitary lobes, PI, pars distalis (PD) and pars nervosa (PN), as well as the total number and mean size of PI cells (PICs), were determined using state-of-the-art quantitative stereological methods. There were significant associations between histological grade, the appearance of PI adenomas, follicles and cysts in the PI, lipofuscin in the PN (P<0.001) and focal hyperplasia of chromophobes in the PD and age. In contrast, the appearance of follicles and cysts in the PD, invasion of basophil cells into the PN, haemorrhage and necrosis were not age dependent. PI adenomas were observed in 18% (22/124) of the animals, but only four horses were evidently suffering from PPID, therefore clinically overt/PPID-associated PI adenomas were found in 3% (4/124) of all horses. Most PI adenomas were incidental and considered non-functional. Pituitary weight, PI volume, total number and mean volume of PICs increased with age in all horses. The total PI volume and the number of PICs of horses exhibiting PPID-associated PI adenomas were significantly higher, while the mean size of PICs was smaller compared with that of horses showing non-PPID-associated adenoma, which suggests that different growth processes are responsible for adenoma formation. The present study demonstrated various age-associated lesions of the PD and PN and revealed a high frequency of incidental, non-PPID-associated PI adenomas in aged horses. Therefore, post-mortem diagnosis of PPID in horses is possible, by determination of pituitary weight and by demonstration of PIC hyperplasia, using quantitative stereological methods.

Exome sequencing identifies potential novel candidate genes in patients with unexplained colorectal adenomatous polyposis.

In up to 30% of patients with colorectal adenomatous polyposis, no germline mutation in the known genes APC, causing familial adenomatous polyposis, MUTYH, causing MUTYH-associated polyposis, and POLE or POLD1, causing Polymerase-Proofreading-associated polyposis can be identified, although a hereditary etiology is likely. To uncover new causative genes, exome sequencing was performed using DNA from leukocytes and a total of 12 colorectal adenomas from seven unrelated patients with unexplained sporadic adenomatous polyposis. For data analysis and variant filtering, an established bioinformatics pipeline including in-house tools was applied. Variants were filtered for rare truncating point mutations and copy-number variants assuming a dominant, recessive, or tumor suppressor model of inheritance. Subsequently, targeted sequence analysis of the most promising candidate genes was performed in a validation cohort of 191 unrelated patients. All relevant variants were validated by Sanger sequencing. The analysis of exome sequencing data resulted in the identification of rare loss-of-function germline mutations in three promising candidate genes (DSC2, PIEZO1, ZSWIM7). In the validation cohort, further variants predicted to be pathogenic were identified in DSC2 and PIEZO1. According to the somatic mutation spectra, the adenomas in this patient cohort follow the classical pathways of colorectal tumorigenesis. The present study identified three candidate genes which might represent rare causes for a predisposition to colorectal adenoma formation. Especially PIEZO1 (FAM38A) and ZSWIM7 (SWS1) warrant further exploration. To evaluate the clinical relevance of these genes, investigation of larger patient cohorts and functional studies are required.

Exposure to Cigarette Smoke Contributes to the Risk of Developing a Colorectal Adenoma, Doesn't It? Are Repeated Exposures to Such Smoke Dangerous?

See Article on Page 51-57 One cigarette contains over 600 ingredients, 4,000 chemicals, 50 cancer-causing agents and many poisonous toxins. In the early 1990s, Zahm et al. [1] of the National Cancer Institute, in a study that used flexible sigmoidoscopy to examine 185 nonsmokers, 229 ex-smokers, and 132 current smokers, reported respective risk ratios for developing adenomatous polyps of 1.0, 1.2, and 2.7. Standardized prevalence rates for polyps increased by smoking category (never smoked: 0.094, ex-smoker: 0.118, current smokers: 0.214). Both adenomatous and hyperplastic polyps showed an association with pack years among both current and ex-smokers. In a meta-analysis of 42 independent observational studies up to 2007 [2], the pooled risks estimated for current and former smokers and those who had always smokers in comparison with those who had never smoked were 2.14 (95% confidence interval [CI], 1.86–2.46), 1.47, and 1.82, respectively. The study provided strong evidence for the detrimental effect of cigarette smoking on the development of adenomatous polyps. Because the risk for developing an adenoma was greater, smoking may be important for both the formation and aggressiveness of adenomas. Anderson et al. [3] screened 600 patient who had high-definition wide-angle colonoscopes. Smoking was associated with having a flat adenoma of any size (adjusted odds ratio, 2.53). Figueiredo et al. [4] conducted a combined analysis of the occurrences of conventional adenomas and serrated polyps by using individual-level data from 2,915 patients participating in three colonoscopy-based clinical trials. Cigarette smoking had only a weak association with adenomas, but was associated with a significantly increased risk of developing serrated polyps, particularly in the left colorectum. The association between cigarette smoking and the risk of developing colorectal cancer in a large prospective cohort from the United States was reported in 2009 [5]. In that prospective study of 184,187 people, the incidence of colorectal cancer was significantly higher in current (hazard ratios [HR], 1.27) and former smokers (HR, 1.23) than it was in lifelong nonsmokers (Table 1). The relative risk was greatest among current smokers with at least 50 years of smoking (HR, 1.38; 95% CI, 1.04–1.84). Among former smokers, the risk of colorectal cancer decreased with greater time since cessation (P = 0.0003) and with earlier age at cessation (P = 0.0014). No association was seen among former smokers who had quit before the age of 40 years or had abstained for 31 years or more. Table 1 Hazard ratios for patients with colorectal cancer caused by cigarette smoking among current and former smokers compared with those who had never smoked (CPS-III nutrition cohort 1992–2005) Liu et al. [6] investigated the effects of exposure to cigarette smoke (CS) on inflammation-associated tumorigenesis in the balb/c mice. During exposure to smoke exposure, the mice were put into a ventilated smoking chamber (39.0 × 23.5 × 21.0 cm3) with 2% CS (v/v, smoke/air). The smoke/air concentration in the chamber was kept constant by the use of peristaltic pumps (Masterflex, Cole Parmer Instrument, Niles, IL, USA), which delivered smoke. Cigarette smoking significantly attenuated the apoptotic effect probably via the induction of antiapoptotic protein bcl-2. Vascular endothelial growth factor and angiogenesis in the colon were also increased in animals with colitis that had been exposed to CS. On the basis of the references mentioned above, the readers have to figure out carefully the purpose of this article, Association Between Exposure to Environmental Tobacco Smoke at the Workplace and Risk of Developing a Colorectal Adenoma: A Cross-Sectional Study, published in this issue [7]. In that research, patients in the nonadenoma group were compared with those in the colorectal adenoma group by using the variables of passive smoking. As a result of that comparison, the fully-adjusted odd ratio for developing a colorectal adenoma as a result of exposure to environmental tobacco smoke was 1.95 (95% CI, 1.08–2.44). The article is encouraging in that it provides evidence to support further study of the effects of environmental hazards on the risks for developing colorectal cancer in this country. Various approaches to one subject can be inspiring in many different ways.