Paul A. Drew

An autocrine TGF-β/ZEB/miR-200 signaling network regulates establishment and maintenance of epithelial-mesenchymal transition

Epithelial-mesenchymal transition is a form of cellular plasticity that is critical for embryonic development and tumor metastasis. This study shows that a signaling network involving autocrine TGF-β signaling, ZEB transcription factors, and the miR-200 family regulates interconversion between epithelial and mesenchymal states.

Epigenetic modulation of the miR-200 family is associated with transition to a breast cancer stem-cell-like state

Summary The miR-200 family is a key regulator of the epithelial–mesenchymal transition, however, its role in controlling the transition between cancer stem-cell-like and non-stem-cell-like phenotypes is not well understood. We utilized immortalized human mammary epithelial (HMLE) cells to investigate the regulation of the miR-200 family during their conversion to a stem-like phenotype. HMLE cells were found to be capable of spontaneous conversion from a non-stem to a stem-like phenotype and this conversion was accompanied by the loss of miR-200 expression. Stem-like cell fractions isolated from metastatic breast cancers also displayed loss of miR-200 indicating similar molecular changes may occur during breast cancer progression. The phenotypic change observed in HMLE cells was directly controlled by miR-200 because restoration of its expression decreased stem-like properties while promoting a transition to an epithelial phenotype. Investigation of the mechanisms controlling miR-200 expression revealed both DNA methylation and histone modifications were significantly altered in the stem-like and non-stem phenotypes. In particular, in the stem-like phenotype, the miR-200b-200a-429 cluster was silenced primarily through polycomb group-mediated histone modifications whereas the miR-200c-141 cluster was repressed by DNA methylation. These results indicate that the miR-200 family plays a crucial role in the transition between stem-like and non-stem phenotypes and that distinct epigenetic-based mechanisms regulate each miR-200 gene in this process. Therapy targeted against miR-200 family members and epigenetic modifications might therefore be applicable to breast cancer.

Reversal and Prevention of Arsenic-Induced Human Bronchial Epithelial Cell Malignant Transformation by microRNA-200b

Arsenic is a well-recognized human carcinogen, yet the mechanism by which it causes human cancer has not been elucidated. MicroRNAs (miRNAs) are a big family of small noncoding RNAs and negatively regulate the expression of a large number of protein-coding genes. We investigated the role of miRNAs in arsenic-induced human bronchial epithelial cell malignant transformation and tumor formation. We found that prolonged exposure of immortalized p53-knocked down human bronchial epithelial cells (p53(low)HBECs) to low levels of arsenite (NaAsO₂, 2.5 μM) caused malignant transformation that was accompanied by epithelial to mesenchymal transition (EMT) and reduction in the levels of miR-200 family members. Stably reexpressing miR-200b in arsenite-transformed cells (As-p53(low)HBECs) completely reversed their transformed phenotypes, as evidenced by inhibition of colony formation in soft agar and prevention of xenograft tumor formation in nude mice. Moreover, stably expressing miR-200b alone in parental nontransformed p53(low)HBECs was sufficient to completely prevent arsenite exposure from inducing EMT and malignant transformation. Further mechanistic studies showed that depletion of miR-200 in arsenite-transformed cells involved induction of the EMT-inducing transcription factors zinc-finger E-box-binding homeobox factor 1 (ZEB1) and ZEB2 and increased methylation of miR-200 promoters. Stably expressing ZEB1 alone in parental nontransformed p53(low)HBECs was sufficient to deplete miR-200, induce EMT and cause cell transformation, phenocopying the oncogenic effect of 16-week arsenite exposure. These findings establish for the first time a causal role for depletion of miR-200b expression in human cell malignant transformation and tumor formation resulting from arsenic exposure.

Genome-wide copy number analysis in esophageal adenocarcinoma using high-density single-nucleotide polymorphism arrays

We applied whole-genome single-nucleotide polymorphism arrays to define a comprehensive genetic profile of 23 esophageal adenocarcinoma (EAC) primary tumor biopsies based on loss of heterozygosity (LOH) and DNA copy number changes. Alterations were common, averaging 97 (range, 23-208) per tumor. LOH and gains averaged 33 (range, 3-83) and 31 (range, 11-73) per tumor, respectively. Copy neutral LOH events averaged 27 (range, 7-57) per EAC. We noted 126 homozygous deletions (HD) across the EAC panel (range, 0-11 in individual tumors). Frequent HDs within FHIT (17 of 23), WWOX (8 of 23), and DMD (6 of 23) suggest a role for common fragile sites or genomic instability in EAC etiology. HDs were also noted for known tumor suppressor genes (TSG), including CDKN2A, CDKN2B, SMAD4, and GALR1, and identified PDE4D and MGC48628 as potentially novel TSGs. All tumors showed LOH for most of chromosome 17p, suggesting that TSGs other than TP53 may be targeted. Frequent gains were noted around MYC (13 of 23), BCL9 (12 of 23), CTAGE1 (14 of 23), and ZNF217 (12 of 23). Thus, we have confirmed previous reports indicating frequent changes to FHIT, CDKN2A, TP53, and MYC in EAC and identified additional genes of interest. Meta-analysis of previous genome-wide EAC studies together with the data presented here highlighted consistent regions of gain on 8q, 18q, and 20q and multiple LOH regions on 4q, 5q, 17p, and 18q, suggesting that more than one gene may be targeted on each of these chromosome arms. The focal gains and deletions documented here are a step toward identifying the key genes involved in EAC development.

High-Risk Human Papillomavirus in Esophageal Squamous Cell Carcinoma

Background: Although most cases of esophageal squamous cell carcinoma (ESCC) in western populations have been attributed to high levels of exposure to tobacco and alcohol, infectious agents have been postulated as possible causes, particularly human papillomavirus (HPV). Methods: To explore this issue, we analyzed HPV DNA prevalence and HPV types together with lifestyle factors, in relation to tumor stage and survival in a low-incidence population. Archived tumor samples from a nationwide cohort of 222 ESCC patients were tested for the presence of HPV DNA by PCR; positive samples were sequenced to determine HPV type, and p16INK4a status was assessed by immunohistochemistry. Results: Of 222 ESCC patients, 8 tested HPV positive (prevalence, 3.6%; 95% confidence interval, 1.1-6.1%), of which 6 were HPV-16 positive and 2 were HPV-35 positive. Four of the eight HPV-positive tumors overexpressed p16INK4a. None of 55 normal esophageal tissue samples from healthy participants had any detectable HPV. Although the numbers were low, it seemed that patients with HPV-positive ESCC tumors were younger than those with HPV-negative tumors (mean age, 60.8 versus 65.3 years, P = 0.18) and had higher body mass index (BMI) throughout life (mean current BMI of 25.1 for HPV positive, 22.2 for HPV negative, P = 0.08; mean BMI at 20 years of 25.8 for HPV positive, 22.1 for HPV negative, P = 0.003). We found no difference between patients with HPV-positive and HPV-negative tumors with respect to other lifestyle factors. Conclusions: These findings suggest a very low prevalence of HPV DNA in human ESCC. Impact: HPV is very unlikely to be a common cause of ESCC in Australia. Cancer Epidemiol Biomarkers Prev; 19(8); 2080–7. ©2010 AACR.

Similarity of aberrant DNA methylation in Barrett's esophagus and esophageal adenocarcinoma

BackgroundBarretts esophagus (BE) is the metaplastic replacement of squamous with columnar epithelium in the esophagus, as a result of reflux. It is the major risk factor for the development of esophageal adenocarcinoma (EAC). Methylation of CpG dinucleotides of normally unmethylated genes is associated with silencing of their expression, and is common in EAC. This study was designed to determine at what stage, in the progression from BE to EAC, methylation of key genes occurs.ResultsWe examined nine genes (APC, CDKN2A, ID4, MGMT, RBP1, RUNX3, SFRP1, TIMP3, and TMEFF2), frequently methylated in multiple cancer types, in a panel of squamous (19 biopsies from patients without BE or EAC, 16 from patients with BE, 21 from patients with EAC), BE (40 metaplastic, seven high grade dysplastic) and 37 EAC tissues. The methylation frequency, the percentage of samples that had any extent of methylation, for each of the nine genes in the EAC (95%, 59%, 76%, 57%, 70%, 73%, 95%, 74% and 83% respectively) was significantly higher than in any of the squamous groups. The methylation frequency for each of the nine genes in the metaplastic BE (95%, 28%, 78%, 48%, 58%, 48%, 93%, 88% and 75% respectively) was significantly higher than in the squamous samples except for CDKN2A and RBP1. The methylation frequency did not differ between BE and EAC samples, except for CDKN2A and RUNX3 which were significantly higher in EAC. The methylation extent was an estimate of both the number of methylated alleles and the density of methylation on these alleles. This was significantly greater in EAC than in metaplastic BE for all genes except APC, MGMT and TIMP3. There was no significant difference in methylation extent for any gene between high grade dysplastic BE and EAC.ConclusionWe found significant methylation in metaplastic BE, which for seven of the nine genes studied did not differ in frequency from that found in EAC. This is also the first report of gene silencing by methylation of ID4 in BE or EAC. This study suggests that metaplastic BE is a highly abnormal tissue, more similar to cancer tissue than to normal epithelium.

The effects of a COX-2 inhibitor meloxicam on squamous cell carcinoma of the esophagus in vivo

Our previous study showed that aspirin induced apoptosis of esophageal cancer cells in vitro by inhibiting the pathway of NF‐kappaB downstream regulation of cyclooxygenase‐2. The purpose of this study was to determine if similar changes occurred in vivo in the tumors of patients with SCC of the esophagus who were given a preferential COX‐2 inhibitor, meloxicam. Fifty‐three patients who had an esophagectomy for SCC were allocated randomly to either a Treatment group (n = 25) or a control group (n = 28). Patients in the Treatment group were given 7.5 mg/day of meloxicam, for between 10 and 14 days before surgery. Patients in the control group did not take any type of NSAID during this time interval. Samples of the tumor taken from the resected specimens were collected. Proliferation and apoptosis were measured by flow cytometry. The concentration of 6‐keto‐prostaglandin F1α in cancer tissue was determined by radio‐immuno‐assay. Expression of COX‐2 mRNA was measured with RT‐PCR and COX‐2 protein levels with Western blot analysis. Nuclear NF‐kappaB and cytoplasmic IkappaB protein levels were determined by electrophoretic mobility shift assay and Western blot, respectively. There were significantly more apoptotic cells in the tumors of patients who were using meloxicam. It also decreased the levels of COX‐2 mRNA, COX‐2 protein and nuclear NF‐kappaB protein and increased the cytoplasmic IkappaB protein in the cancer. We conclude that meloxicam induces apoptosis in SCC of the esophagus in vivo by inhibiting the pathway of NF‐kappaB downstream regulation of COX‐2.

Whole Genome Expression Array Profiling Highlights Differences in Mucosal Defense Genes in Barrett's Esophagus and Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) has become a major concern in Western countries due to rapid rises in incidence coupled with very poor survival rates. One of the key risk factors for the development of this cancer is the presence of Barretts esophagus (BE), which is believed to form in response to repeated gastro-esophageal reflux. In this study we performed comparative, genome-wide expression profiling (using Illumina whole-genome Beadarrays) on total RNA extracted from esophageal biopsy tissues from individuals with EAC, BE (in the absence of EAC) and those with normal squamous epithelium. We combined these data with publically accessible raw data from three similar studies to investigate key gene and ontology differences between these three tissue states. The results support the deduction that BE is a tissue with enhanced glycoprotein synthesis machinery (DPP4, ATP2A3, AGR2) designed to provide strong mucosal defenses aimed at resisting gastro-esophageal reflux. EAC exhibits the enhanced extracellular matrix remodeling (collagens, IGFBP7, PLAU) effects expected in an aggressive form of cancer, as well as evidence of reduced expression of genes associated with mucosal (MUC6, CA2, TFF1) and xenobiotic (AKR1C2, AKR1B10) defenses. When our results are compared to previous whole-genome expression profiling studies keratin, mucin, annexin and trefoil factor gene groups are the most frequently represented differentially expressed gene families. Eleven genes identified here are also represented in at least 3 other profiling studies. We used these genes to discriminate between squamous epithelium, BE and EAC within the two largest cohorts using a support vector machine leave one out cross validation (LOOCV) analysis. While this method was satisfactory for discriminating squamous epithelium and BE, it demonstrates the need for more detailed investigations into profiling changes between BE and EAC.

Fat distribution and changes in the blood brain barrier in a rat model of cerebral arterial fat embolism

This study was designed to determine the distribution of fat which reaches the brain by the internal carotid artery, and the consequent alterations in the blood brain barrier, in a rat model of cerebral arterial fat embolism. The distribution of the blood flow in this model was determined by the injection of radiolabelled microspheres. Over 44% were trapped in the brain, 43% in the extracerebral tissues of the head and neck, and 7% in the lungs. Over 30% of radiolabelled triolein was present within the brain 30 min after injection, and 4% still remained after 17 days. Approximately 25% of the triolein which went to the brain moved through the cerebral vessels and left within the first 15 min. The majority of the triolein distributed to the ipsilateral cerebral hemisphere, with significantly less to the contralateral cerebral hemisphere, brain stem and cerebellum. The blood brain barrier opened, as measured by uptake of 99mTc, within the first 15 min and remained open for at least 3 days. A significant percentage of fat reaching the brain persists for days, and causes rapid and long-lasting damage to the blood brain barrier.

A comparison of primary oesophageal squamous epithelial cells with HET-1A in organotypic culture

Background Information. Carcinoma of the oesophagus is the sixth leading cause of cancer death in the western world and is associated with a 5‐year survival of less than 15%. Recent evidence suggests that stromal—epithelial interactions are fundamental in carcinogenesis. The advent of co‐culture techniques permits the investigation of cross‐talk between the stroma and epithelium in a physiological setting. We have characterized a histologically representative oesophageal organotypic model and have used it to compare the most commonly used squamous oesophageal cell line, HET‐1A, with primary oesophageal squamous cells for use in studies of the oesophageal epithelium in vitro.