Immunohistochemical Study of Mitosis-regulatory Proteins in Gastroenteropancreatic Neuroendocrine Neoplasms.

Background/aim: Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are rare and heterogeneous tumors. Therapeutic targets remain to be identified and apart from the proliferation marker Ki-67, useful prognostic markers are rare. Mitotic proteins, such as forkheadbox protein M1 (FOXM1), survivin and aurora kinases, play a role in GEP-NEN progression.

Loss of nuclear p27 expression and its prognostic role in relation to cyclin E and p53 mutation in gastroenteropancreatic neuroendocrine tumors.

Purpose: Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are classified by the WHO, yet its prognostic value needs to be confirmed. Therefore, we aimed to determine the prognostic role of cell cycle key regulatory genes p53, p27kip1 (p27), and cyclin E in this tumor entity.

Experimental Design: Tumor specimen from 89 patients with a complete follow-up were studied immunohistochemically for p27 and cyclin E expression and for p53 mutations.

Molecular characteristics and predictors of survival in patients with malignant neuroendocrine tumors.

To better understand the molecular pathogenesis of neuroendocrine tumors (NET), we investigated the molecular and clinical characteristics of malignant poorly differentiated colorectal NET and compared these findings with sporadic CRC and well-differentiated benign and malignant fore-/midgut NET. Tumors were analyzed and correlated for microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP). NET were scored for proliferation using Ki-67.

Analysis of molecular pathways in sporadic neuroendocrine tumors of the gastro-entero-pancreatic system.

Little is known about the molecular pathogenesis of neuroendocrine tumors (NET) of the gastro-entero-pancreatic (GEP) system. We analyzed genetic and epigenetic alterations as well as the CpG island methylator phenotype (CIMP). The study comprised 118 well-differentiated fore- and mid-gut GEP-NET from 71 patients.

The CpG island methylator phenotype and chromosomal instability are inversely correlated in sporadic colorectal cancer.

Background & Aims: The CpG island methylator phenotype (CIMP) is one of the mechanisms involved in colorectal carcinogenesis (CRC). Although CIMP is probably the cause of high-frequency microsatellite instability (MSI-H) sporadic CRCs, its role in microsatellite stable (MSS) tumors is debated. The majority of MSS CRCs demonstrate chromosomal instability (CIN) with frequent loss of heterozygosity (LOH) at key tumor suppressor genes.

Octreotide versus octreotide plus interferon-alpha in endocrine gastroenteropancreatic tumors: a randomized trial.

Background & Aims: The effect of octreotide plus interferon-alpha versus octreotide monotherapy on the primary study end points of time to treatment failure (progression, death, stop of study treatment) and long-term survival was investigated in patients with progressive metastatic neuroendocrine foregut (mainly pancreatic) and midgut tumors.

Methods: One hundred nine of 125 registered patients were randomized starting in January 1995, and 105 patients (51 monotherapy, 54 combination treatment) were finally analyzed in March 2000. Tumor growth was assessed at 3-month intervals by computed tomography or magnetic resonance imaging.

Molecular pathogenesis of colorectal cancer: implications for molecular diagnosis.

Colorectal cancer is the third leading cause of cancer-related death in both men and woman in industrialized countries. Major advances have been made in our understanding of molecular events leading to formation of adenomatous polyps and cancer. Most colorectal cancers are sporadic, but a significant proportion (5-6%) has a clear genetic background.

Nuclear survivin is a powerful novel prognostic marker in gastroenteropancreatic neuroendocrine tumor disease.

Gastroenteropancreatic neuroendocrine tumors represent a heterogeneous tumor entity. The growth pattern ranges from very slowly to fast growing, aggressive types of tumors. Survivin, a member of the family of apoptosis inhibitors, is a bifunctional protein that suppresses apoptosis and regulates cell division.

Epigenetic inactivation of RUNX3 in microsatellite unstable sporadic colon cancers.

Runt domain transcription factors are important targets of TGF-beta superfamily proteins and play a crucial role in mammalian development. Three mammalian runt-related genes, RUNX1, RUNX2 and RUNX3, have been described. RUNX3 has been shown to be a putative tumor suppressor gene localized to chromosome 1p36, a region showing frequent loss of heterozygosity events in colon, gastric, breast and ovarian cancers.

APC promoter hypermethylation contributes to the loss of APC expression in colorectal cancers with allelic loss on 5q.

Introduction: Germ-line mutations of the APC gene are associated with familial adenomatous polyposis, and somatic mutations occur frequently in sporadic colorectal cancer. However, to abrogate APC function, both alleles must be inactivated. Recently, it has been demonstrated that epigenetic modification of the APC promoter influences APC silencing.

Analysis of molecular pathways in neuroendocrine cancers of the gastroenteropancreatic system.

Neuroendocrine gastroenteropancreatic (GEP) tumors are rare and present with variable clinical syndromes. So far, there are no detailed studies concerning the molecular pathogenesis of sporadic GEP tumors. In our study, GEP tumors from 29 patients were assessed for microsatellite instability, aberrant promoter methylation, and LOH of various tumor suppressor genes.

Frequent inactivation of PTEN by promoter hypermethylation in microsatellite instability-high sporadic colorectal cancers.

Loss of PTEN tumor suppressor function is observed in tumors of breast, prostate, thyroid, and endometrial origin. Allelic losses in the proximity of the PTEN locus (10q23) also occur in sporadic colorectal cancers (CRCs), but biallelic inactivation of this site has not been frequently demonstrated. We hypothesized that alternative mechanisms of PTEN allelic inactivation, such as promoter hypermethylation, might be operative in CRC and that PTEN inactivation may be related to recognized forms of genomic instability.

Evaluation of microsatellite instability, hMLH1 expression and hMLH1 promoter hypermethylation in defining the MSI phenotype of colorectal cancer.

Introduction: About 15% of all colorectal cancers (CRCs) demonstrate high levels of microsatellite instability (MSI-H) and are currently best identified by molecular analysis of microsatellite markers. Most sporadic CRCs with MSI-H are known to be associated with the methylation of the hMLH1 promoter. Promoter methylation coincided with lack of hMLH1 expression.

Role of hMLH1 promoter hypermethylation in drug resistance to 5-fluorouracil in colorectal cancer cell lines.

Loss of DNA mismatch repair (MMR) occurs in 10-15% of sporadic colorectal cancer, is usually caused by hMLH1 hypermethylation, and has been shown to confer resistance to various chemotherapeutic reagents, including 5-fluorouracil (5-FU). We tested the hypothesis that demethylation of the hMLH1 promoter in hypermethylated colorectal cancer cells would restore MMR proficiency and drug sensitivity to 5-FU. We used the MMR-deficient cell lines SW48, HCT116, HCT116+chr2 and the -proficient cell line HCT116+chr3.

Characterization of sporadic colon cancer by patterns of genomic instability.

Colorectal cancer (CRC) can progress through two pathways of genomic instability: chromosomal (CIN) and microsatellite instability (MSI). We hypothesized that these two pathways are not always independent and that some tumors therefore show a significant degree of overlap between these two mechanisms. We classified 209 high-risk stage II and stage III sporadic CRCs based on their MSI status, using a National Cancer Institute-recommended panel of microsatellite markers, and also identified MSI-associated mutations of CRC target genes such as TGFbetaRII.

Identification of frame-shift intermediate mutant cells.

Frame-shift mutations at microsatellites occur as a time-dependent function of polymerase errors followed by failure of postreplicational mismatch repair. A cell-culture system was developed that allows identification of intermediate mutant cells that carry the mutation on a single DNA strand after the initial DNA polymerase errors. A plasmid was constructed that contained 13 repeats of a poly(dC-dA).