Biomedical subjects

Stanley R Hamilton

Publications and source records attributed to Stanley R Hamilton.

60 records · Page 4Linked to original sources

PubMed2002

Sporadic fundic gland polyps with epithelial dysplasia : evidence for preferential targeting for mutations in the adenomatous polyposis coli gene.

Gastric fundic gland polyps (FGPs) occur in two distinct clinicopathological scenarios: sporadic and familial adenomatous polyposis (FAP) associated. FAP-associated FGPs arise through somatic second hit alterations of the adenomatous polyposis coli (APC) gene and frequently demonstrate epithelial dysplasia (Am J Pathol 2000, 157:747-754). Sporadic FGPs, in contrast, tend to contain beta-catenin gene mutations and only infrequently show dysplasia (Am J Pathol 2001, 158:1005-1010). However, sporadic FGPs with dysplasia have not been previously investigated. We studied 13 sporadic FGPs with surface/foveolar low-grade dysplasia or changes indefinite for dysplasia for alterations in the APC/beta-catenin pathway, using chromosome 5q allelic loss assays and direct DNA sequencing of the mutation cluster region in exon 15 of APC and the phosphorylation region in exon 3 of beta-catenin. In addition, to evaluate for possible additional genetic alterations in FGPs, all cases were evaluated for microsatellite instability using fluorescent-based amplification of a standard panel of five microsatellite markers. Alterations in APC were present in seven (53.8%) FGPs, including two cases with bi-allelic APC inactivation (truncating intragenic mutation plus 5q allelic loss), two cases with APC mutation only, and three cases with 5q allelic loss only. In contrast, only two (15.4%) FGPs contained stabilizing beta-catenin mutations. All 13 FGPs were microsatellite stable. These results indicate that sporadic FGPs with dysplasia/indefinite for dysplasia are molecularly similar to FAP-associated FGPs, and are dissimilar to the more common sporadic nondysplastic FGPs. Mutations in APC and beta-catenin, despite occurring in the same genetic pathway, show differing biological properties, a phenomenon that has previously been demonstrated in colorectal neoplasms. The lack of microsatellite instability in FGPs in this study and of K-ras mutations in a previous study suggests that secondary genetic alterations are rare in both dysplastic and nondysplastic FGPs.

Adult↗

PubMed2002

Evaluation of non-formalin tissue fixation for molecular profiling studies.

Using a general strategy for evaluating clinical tissue specimens, we found that 70% ethanol fixation and paraffin embedding is a useful method for molecular profiling studies. Human prostate and kidney were used as test tissues. The protein content of the samples was analyzed by one-dimensional gel electrophoresis, immunoblot, two-dimensional gel electrophoresis, and layered expression scanning. In each case, the fixed and embedded tissues produced results similar to that obtained from snap-frozen specimens, although the protein quantity was somewhat decreased. Recovery of mRNA was reduced in both quantity and quality in the ethanol-fixed samples, but was superior to that obtained from formalin-fixed samples and sufficient to perform reverse transcription polymerase chain reactions. Recovery of DNA from ethanol-fixed specimens was superior to formalin-fixed samples as determined by one-dimensional gel electrophoresis and polymerase chain reaction. In conclusion, specimens fixed in 70% ethanol and embedded in paraffin produce good histology and permit recovery of DNA, mRNA, and proteins sufficient for several downstream molecular analyses. Complete protocols and additional discussion of relevant issues are available on an accompanying website (http://cgap-mf.nih.gov/).

Actins↗

PubMed2002

Concordant CpG island methylation in hyperplastic polyposis.

The CpG island methylator phenotype (CIMP) is a newly described mechanism for carcinogenesis in colorectal carcinomas and adenomas characterized by methylation of multiple CpG islands. The causes of CIMP are unknown. We studied CIMP in hyperplastic polyps (HPs), with emphasis on patients with multiple HPs (5 to 10 HPs), large HPs (one HP >1 cm) or hyperplastic polyposis (>20 HPs). Methylation of p16, MINT1, MINT2, MINT31, and hMLH1 was analyzed by methylation-specific polymerase chain reaction in 102 HPs, 8 serrated adenomas, 19 tubular adenomas, and 9 adenocarcinomas from 17 patients, with multiple/large HPs or hyperplastic polyposis and in 16 sporadic HPs from 14 additional patients. Sporadic HPs were CIMP-negative (not methylated at any locus), but 43% of HPs from multiple/large HPs, or hyperplastic polyposis were CIMP-high (two or more methylated loci, P = 0.00001). Methylation among the four loci was correlated within HPs (odds ratio, 3.41; P = 0.002), and the methylation status of HPs within the same patient was also correlated (odds ratio, 5.92; P = 0.0001). CIMP-high HPs were present primarily in patients with a predominance of HPs in the right colon and/or serrated adenomas (P = 0.0009) and were associated with the absence of K-ras proto-oncogene mutations (odds ratio, 5.08; P = 0.03). Our findings of concordant CpG island methylation of HPs in multiple/large HPs or hyperplastic polyposis supports the concept that some patients have a hypermethylator phenotype characterized by methylation of multiple HPs and other colorectal lesions. The hypermethylator phenotype is related to patient-specific factors, such as carcinogenic exposure or genetic predisposition.

Adenocarcinoma↗

PubMed2002

Mucinous and nonmucinous appendiceal adenocarcinomas: different clinicopathological features but similar genetic alterations.

The genetic alterations of appendiceal carcinomas have not been reported in detail. We studied the clinicopathological factors and genetic alterations including microsatellite instability, p53 overexpression, and mutations of the K-ras proto-oncogene of 30 appendiceal adenocarcinomas, consisting of 23 mucinous and 7 nonmucinous carcinomas. Sixteen (70%) mucinous carcinomas presented with pseudomyxoma peritonei, but 6 of 7 (86%) nonmucinous carcinomas presented with appendicitis (P =.002). All carcinomas were microsatellite stable, and p53 overexpression was present in only 1 of 30 (3%) carcinomas. K-ras mutation was present in 11 of 20 (55%) carcinomas, including 8 of 16 (50%) mucinous and 3 of 4 (75%) nonmucinous carcinomas. The mean survival of patients with mucinous carcinomas was 26 +/- 19 months compared with 13 +/- 9 months for patients with nonmucinous carcinomas (P =.0002). Our findings suggest that mucinous and nonmucinous carcinomas of appendix have similar genetic alterations, but different clinical presentation and prognosis.

Adenocarcinoma↗

PubMed2002

Identification of combination gene sets for glioma classification.

One goal for the gene expression profiling of cancer tissues is to identify signature genes that robustly distinguish different types or grades of tumors. Such signature genes would ideally provide a molecular basis for classification and also yield insight into the molecular events underlying different cancer phenotypes. This study applies a recently developed algorithm to identify not only single classifier genes but also gene sets (combinations) for use as glioma classifiers. Classifier genes identified by this algorithm are shown to be strong features by conservatively and collectively considering the misclassification errors of the feature sets. Applying this approach to a test set of 25 patients, we have identified the best single genes and two- to three-gene combinations for distinguishing four types of glioma: (a) oligodendroglioma; (b) anaplastic oligodendroglioma; (c) anaplastic astrocytoma; and (d) glioblastoma multiforme. Some of the identified genes, such as insulin-like growth factor-binding protein 2, have been confirmed to be associated with one of the tumor types. Using combinations of genes, the classification error rate can be significantly lowered. In many instances, neither of the individual genes of a two-gene set performs well as an accurate classifier, but the combination of the two genes forms a robust classifier with a small error rate. Two-gene and three-gene combinations thus provide robust classifiers possessing the potential to translate expression microarray results into diagnostic histopathological assays for clinical utilization.

Algorithms↗

PubMedDate not supplied

Apoptotic response to 5-fluorouracil treatment is mediated by reduced polyamines, non-autocrine Fas ligand and induced tumor necrosis factor receptor 2.

5-fluorouracil (5-FU) is the major chemotherapeutic agent for treatment of colorectal carcinoma, but the molecular mechanisms of response and resistance are not understood completely. We therefore studied the 5-FU dose response and time course of gene expression transcriptome changes in colon carcinoma cell lines that are relatively sensitive to or resistant to 5-FU (RKO and HT29, respectively. We identified cellular pathways and corroborated functions of selected pathways. Expression of genes for polyamine biosynthesis, i.e., ornithine decarboxylase (ODC) and spermine and spermidine synthases, was repressed in the sensitive line, while the biosynthesis-inhibiting gene ODC antizyme was induced in the resistant line. The rate-limiting gene in catabolism, spermine/spermidine acetyltransferase, was induced in both lines. Polyamine levels showed corresponding drastic decreases after 5-FU treatment, and polyamine replenishment interfered with 5-FU-induced apoptosis. In the sensitive cells which have wild-type p53, the p53 gene and its downstream genes including p21/WAF1, mdm2, Fas, mic-1, EphA2, and ferredoxin reductase as well as genes in the tumor necrosis factor (TNF) pathway including TNF receptor 2 (TNFR2) were induced, but not Fas ligand (FasL). Exposure to exogenous FasL increased 5-FU-induced apoptosis, and anti-TNFR2 antibody, but not anti-TNFR1, partially protected the sensitive cells. Our combination of gene expression profiling and corroborative functional studies revealed that reduced polyamine levels, non-autocrine FasL originating exogenous to tumor cells, and induced TNFR2 are all functional mediators of apoptosis caused by 5-FU in colon carcinoma cells.

Acetyltransferases↗