Increased cyclooxygenase-2 expression in juvenile polyposis syndrome.

BACKGROUND & AIMS: Gastrointestinal juvenile polyps may occur in juvenile polyposis syndrome (JPS) or sporadically. JPS is an autosomal-dominant condition caused by a germline defect in SMAD4 or BMPR1A in 50% to 60% of cases, and is characterized by multiple juvenile polyps, predominantly in the colorectum. JPS has an increased risk of gastrointestinal malignancy but sporadic juvenile polyps do not. Cyclooxygenase-2 (COX-2) expression is increased in gastrointestinal tumorigenesis and familial adenomatous polyposis. Inhibition of COX-2 leads to regression of colorectal adenomas in familial adenomatous polyposis patients and inhibits gastrointestinal tumorigenesis. To investigate the role of COX-2 in juvenile polyps, we compared the expression of COX-2 in juvenile polyps from a well-defined group of juvenile polyposis patients and sporadic juvenile polyps. METHODS: COX-2 expression was assessed in 24 genetically well-defined JPS patients and 26 patients with sporadic juvenile polyps using tissue microarray analysis. Two additional markers, Hu-antigen R, a stabilizer of messenger RNA, and CCAAT/enhancer-binding protein beta, a transcription factor, both associated with increased COX-2 expression, also were investigated. RESULTS: Increased COX-2 expression in JPS patients was noted compared with patients with sporadic juvenile polyps (P < .001). Also, JPS patients with a BMPR1A germline defect had higher COX-2 expression than did JPS patients in whom no germline mutation was detected. High COX-2 levels correlated with increased cytoplasmic Hu-antigen R expression in JPS polyps (P = .022), but not in sporadic juvenile polyps. CONCLUSIONS: Juvenile polyposis and sporadic juvenile polyps show distinctive expression profiles of COX-2 that may have clinical implications.

Molecular analysis of primary gastric cancer, corresponding xenografts, and 2 novel gastric carcinoma cell lines reveals novel alterations in gastric carcinogenesis.

We report the molecular characterization of 8 primary gastric carcinomas, corresponding xenografts, and 2 novel gastric carcinoma cell lines. We compared the tumors and cell lines, with respect to histology, immunohistochemistry, copy number, and hypermethylation of up to 38 genes using methylation-specific multiplex ligation-dependent probe amplification, and TP53 and CDH1 mutation analysis where relevant. The primary tumors and xenografts were histologically comparable and shared expression of 11 of 14 immunohistochemical markers (E-cadherin, beta-catenin, COX-2, p53, p16, TFF1, cyclin E, MLH1, SMAD4, p27, KLK3, CASR, CHFR, and DAPK1). Gains of CASR, DAPK1, and KLK3--not yet described in gastric cancer--were present in the primary tumors, xenografts, and cell lines. The most prominent losses occurred at CDKN2A (p16), CDKN2B (p15), CDKN1B (p27/KIP1), and ATM. Except for ATM, these losses were found only in the cell line or xenograft, suggesting an association with tumor progression. However, examination of p16 and p27 in 174 gastric cancers using tissue microarrays revealed no significant correlation with tumor stage or lymph node status. Further losses and hypermethylation were detected for MLH1, CHFR, RASSF1, and ESR, and were also seen in primary tumors. Loss of CHFR expression correlated significantly with the diffuse phenotype. Interestingly, we found the highest rate of methylation in primary tumors which gave rise to cell lines. In addition, both cell lines harbored mutations in CDH1, encoding E-cadherin. Xenografts and gastric cancer cell lines remain an invaluable research tool in the uncovering of the multistep progression of cancer. The frequent gains, losses, and hypermethylation reported in this study indicate that the involved genes or chromosomal regions may be relevant to gastric carcinogenesis.

Exclusion of RUNX3 as a tumour-suppressor gene in early-onset gastric carcinomas.

Recent studies claim a critical role for RUNX3 in gastric epithelial homeostasis. However, conflicting results exist regarding RUNX3 expression in the stomach and its potential role as a tumour-suppressor gene (TSG) in gastric carcinogenesis. Our aim was to evaluate the role of RUNX3 in early-onset gastric carcinomas (EOGCs). We analysed 41 EOGCs for RUNX3 aberrations using loss of heterozygosity (LOH), fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) analyses. LOH of markers flanking RUNX3 was relatively common, indicating that loss of the gene may play a role in gastric carcinogenesis. However, FISH analysis of selected cases and a panel of 14 gastric carcinoma-derived cell lines showed widespread presence of multiple copies of centromere 1. While RUNX3 copy numbers were generally equal to or fewer than those of centromere 1, at least two copies were present in almost all cells analysed. Accordingly, a subpopulation of tumour cells in 12/37 cases showed RUNX3 protein expression. However, expression was not detected in the adjacent nontumorous mucosa of any case. Together, these observations indicate that chromosome 1 aberrations occur frequently in EOGCs and are reflected in the LOH and IHC patterns found. Our findings refute a role for RUNX3 as a TSG in EOGCs.

Inflammatory myofibroblastic tumor with ALK/TPM3 fusion presenting as ileocolic intussusception: an unusual presentation of an unusual neoplasm.

Inflammatory myofibroblastic tumor is a rare spindle cell lesion of indeterminate malignant potential occurring in both pulmonary and extrapulmonary tissues. This report describes an unusual presentation of an unusual tumor at an unusual location: an intramural ileal case of inflammatory myofibroblastic tumor presenting with intussusception in a 29-year-old woman. We characterize this tumor through microscopic and ultrastructural analysis, extensive immunohistochemical analysis, ploidy analysis, and Epstein-Barr virus in situ hybridization, and we report the finding of an ALK/TPM3 fusion using fluorescence in situ hybridization.

Do collision tumors of the gastroesophageal junction exist? A molecular analysis.

Collision tumors are thought to arise from the accidental meeting of two independent tumors. Here we present five gastroesophageal junction tumors consisting of two collision tumors and three composite tumors (characterized by two divergent lineages originating from the same neoplastic clonal proliferation), as diagnosed on histology. In an attempt to prove this distinction at a genetic level, we performed TP53 sequence analysis and p53 immunohistochemistry. In addition, loss of heterozygosity (LOH) analysis using 10 microsatellite markers was carried out. An identical TP53 mutation and a similar pattern of retention and LOH were found in both neoplastic components of the presumed collision tumors, suggesting that both components are derived from a single precursor cell that undergoes divergent differentiation in the evolution of the tumor. In the composite group, 1 case had a genetic basis for the possible diagnosis of a collision tumor, with a TP53 mutation in the adenocarcinoma component only, and a different pattern of retention and loss of heterozygosity. These findings imply that it is not possible to recognize true collision tumors from immunohistologic appearance alone and suggest that the long-standing histologic criteria for the diagnosis of these neoplasms have no molecular basis.

LKB1 as the ghostwriter of crypt history.

Familial cancer syndromes present rare insights into malignant tumor development. The molecular background of polyp formation and the cancer prone state in Peutz-Jeghers syndrome remain enigmatic to this day. Previously, we proposed that Peutz-Jeghers polyps are not pre-malignant lesions, but an epiphenomenon to the malignant condition. However, Peutz-Jeghers polyp formation and the cancer-prone state must both be accounted for by the same molecular mechanism. Our contribution focuses on the histopathology of the characteristic Peutz-Jeghers polyp and recent research on stem cell dynamics and how these concepts relate to Peutz-Jeghers polyposis. We discuss a protracted clonal evolution scenario in Peutz-Jeghers syndrome due to a germline LKB1 mutation. Peutz-Jeghers polyp formation and malignant transformation are separately mediated through the same molecular mechanism played out on different timescales. Thus, a single mechanism accounts for the development of benign Peutz-Jeghers polyps and for malignant transformation in Peutz-Jeghers syndrome.

Her-2/neu testing and therapy in gastroesophageal adenocarcinoma.

Despite ongoing advances in the treatment of gastroesophageal cancer, prognosis remains poor. The best promise to improve this poor survival is provided by new targeted agents. Of these, human epidermal growth factor receptor 2 (HER2) is currently in the spotlight. In this review, we provide an overview of recent developments in HER2 testing and results of clinical trials targeting HER2 in gastroesophageal adenocarcinoma. Based on the encouraging ToGA trial findings it is now expected that routine HER2 testing will be included in the diagnostic work-up of patients with advanced gastric cancer. With regard to this testing, overexpression of the HER2 protein seems to possess the best predictive properties. However, HER2 immunohistochemistry (IHC) is subject to assay and interobserver variability, so standardization and internal and external proficiency testing is an absolute prerequisite, especially as the IHC scoring system in gastric cancer is different from that of breast cancer. Further study is needed to investigate the clinical meaning of the significant heterogeneity observed in both gene amplification and protein overexpression in gastroesophageal cancer. Highly effective therapies for gastroesophageal cancer can only be accomplished by a multi-targeted approach, considering crosstalk between pathways and continuing to optimize chemotherapy.

Pancreatic intraepithelial neoplasia and pancreatic tumorigenesis: of mice and men.

CONTEXT: Pancreatic cancer has a poor prognosis with a 5-year survival of less than 5%. Early detection is at present the only way to improve this outlook. This review focuses on the recent advances in our understanding of pancreatic carcinogenesis, the scientific evidence for a multistaged tumor progression, and the role genetically engineered mouse models can play in recapitulating the natural course and biology of human disease. OBJECTIVES: To illustrate the stepwise tumor progression of pancreatic cancer and genetic alterations within the different stages of progression and to review the findings made with genetically engineered mouse models concerning pancreatic carcinogenesis. DATA SOURCES: A review of recent literature on pancreatic tumorigenesis and genetically engineered mouse models. CONCLUSIONS: Pancreatic cancer develops through stepwise tumor progression in which preinvasive stages, called pancreatic intraepithelial neoplasia, precede invasive pancreatic cancer. Genetic alterations in oncogenes and tumor suppressor genes underlying pancreatic cancer are also found in pancreatic intraepithelial neoplasia. These mutations accumulate during progression through the consecutive stages of pancreatic intraepithelial neoplasia lesions. Also in genetically engineered mouse models of pancreatic ductal adenocarcinoma, tumorigenesis occurs through stepwise progression via consecutive mouse pancreatic intraepithelial neoplasia, and these models provide important tools for clinical applications. Nevertheless differences between mice and men still remain.

A novel region of amplification at 11p12-13 in gastric cancer, revealed by representational difference analysis, is associated with overexpression of CD44v6, especially in early-onset gastric carcinomas.

Diffuse-type gastric carcinomas (GCs) are often difficult to characterize because of contamination of tumor samples by surrounding normal tissue. As such, information regarding chromosomal aberrations in this subtype of GCs is limited. In this study, we used representational difference analysis to pinpoint genomic amplifications occurring in diffuse-type GCs. We found nine differential products from two novel regions of amplification in two tumors: one product mapped to 19p13.1 and eight mapped to a 1.8-Mb region in chromosomal segment 11p12-13. These amplifications were confirmed using Southern blot analysis and occurred in 3/16 and 6/15 diffuse-type GCs, respectively. CD44, a well characterized cellular adhesion molecule involved in several human malignancies, is encoded by a gene located within 200 kb of the 11p12-13 amplification fragments. We confirmed that overexpression of isoform CD44v6 was correlated with amplification at 11p12-13 in 11/12 diffuse-type GCs. Since diffuse-type GCs occur more frequently in early-onset gastric carcinomas (EOGCs, presented at 45 years of age or younger) than in "conventional" GCs, and the tumors carrying the original amplifications were EOGCs, we investigated overexpression of CD44v6 in 107 EOGCs and 88 conventional GCs using tissue microarrays. We found frequent CD44v6 overexpression in both tumor groups (76% and 57% respectively) and, interestingly, significantly more cases with overexpression of CD44v6 in EOGCs than in conventional GCs (P = 0.005), irrespective of histology. These findings provide further evidence for both the relevance of CD44 in GC and for distinct molecular characteristics of EOGCs when compared with those of GCs occurring at a later age.

Early-onset gastric cancers have a different molecular expression profile than conventional gastric cancers.

Many studies examine the molecular genetics of gastric cancer, but few look at young patients in particular and there is no comparison of molecular expression between early-onset gastric cancer (< or = 45 years old) and conventional gastric cancers. Expression of cycloxygenase-2 (COX-2) is elevated in gastric adenocarcinomas compared to non-neoplastic mucosa, and in light of studies showing reduced risk of gastric cancer in nonsteroidal anti-inflammatory drug users, we have chosen to investigate the expression of COX-2 and related molecules in 113 early-onset gastric cancers and compare it with 91 conventional gastric cancers, using tissue microarrays. These markers include molecules known to be important in conventional gastric carcinogenesis, such as E-Cadherin, p53, COX-2, Trefoil Factor-1 (TFF1), beta-catenin, p16 and c-myc; as well as molecules not yet described as being important in gastric cancer, such as the transcription factor c-jun, the COX-2 mRNA stabilizer HuR, and C/EBP-beta, a transcription factor for COX-2. All markers showed a statistically significant difference between early-onset gastric cancers and conventional gastric cancers, using a chi2 test. In particular, early-onset gastric cancers displayed a COX-2 Low, TFF1-expressing phenotype, whereas COX-2 overexpression and loss of TFF1 was found in conventional cancers, and this difference between early-onset gastric cancers and conventional cancers remained statistically significant when adjusted for location and histology (P<0.0001 and P = 0.002 respectively). We found that COX-2 overexpression correlates significantly with loss of TFF1 (P = 0.001), overexpression of C/EBP-beta (P<0.001) and cytoplasmic HuR (P = 0.016). COX-2 was significantly associated with p53 positivity (P = 0.003). Abnormalities in E-Cadherin correlated significantly with diffuse phenotype, whereas high expression of COX-2, loss of TFF1 and overexpression of C/EBP-beta correlated with the intestinal phenotype. Our results provide further evidence that early-onset gastric cancer exhibits a distinctive expression profile that may have practical implications.

Early-onset gastric carcinomas display molecular characteristics distinct from gastric carcinomas occurring at a later age.

Gastric cancer is thought to result from a combination of environmental factors and accumulation of specific genetic alterations, and consequently mainly affects older patients (>50 years of age). Fewer than 10% of patients present with the disease before 45 years of age and these young patients are thought to develop carcinomas with a different molecular genetic profile from that of sporadic carcinomas occurring at a later age. Forty early-onset gastric carcinoma resection specimens were characterized for microsatellite instability (MSI) and loss of heterozygosity status using 22 polymorphic microsatellite markers. Twenty-four biopsies were additionally evaluated for the presence of MSI. No MSI was observed in any of the cases analysed. Losses were infrequent, but were most common for the D1S234 (26.1%) and D1S1676 (17.4%) markers, flanking the RUNX3 gene; for the p53ALU (23.1%) and TP53 (15.4%) markers, near the TP53 gene; and for the D16S2624 (17.2%) marker, near the E-cadherin (CDH1) gene. All cases with loss of CDH1, as well as 6/7 cases with loss of TP53, displayed aberrant staining of the corresponding proteins, pointing to a functional role for these proteins in early-onset gastric carcinogenesis. No germline CDH1, TP53 or RUNX3 mutations were detected in any of the cases analysed. No correlation was observed between non-functional E-cadherin and the histological type of the tumours analysed. Finally, Epstein-Barr virus was not detected in any of the cases analysed. On the basis of these results, early-onset gastric carcinomas appear to have characteristics distinct from gastric carcinomas occurring at a later age.