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Charis Eng

Publications and source records attributed to Charis Eng.

At least 37 records · Page 2Linked to original sources
PubMed2006

Comprehensive mutation scanning of NF1 in apparently sporadic cases of pheochromocytoma.

BACKGROUND: Pheochromocytoma is a rare manifestation in patients with neurofibromatosis type 1 (NF 1). The 57-exon susceptibility gene NF1 has so far not been systematically scanned for unexpected germline mutations in individuals with sporadic pheochromocytoma. METHODS: Twenty-seven patients with bilateral adrenal and/or extraadrenal abdominal pheochromocytoma not carrying germline mutations of the genes VHL, RET, SDHB, and SDHD were selected from the European-American pheochromocytoma registry. All 57 exons and flanking intronic regions of the NF1 gene were PCR amplified using newly designed primer pairs to exclude the amplification of pseudogenes. Intragenic mutation scanning was performed using denaturing HPLC and bidirectional direct sequencing. RESULTS: Of the 27 apparently sporadic cases, one (4%) was found to have a pathogenic germline NF1 mutation, Leu303Arg. Clinical reevaluation of this individual, who had bilateral pheochromocytoma, revealed classic, but very mild, features of NF 1, one cutaneous neurofibroma, axillary freckling, and Lisch nodules of the iris as well as a few café-au-lait spots. CONCLUSIONS: In the absence of germline mutations in VHL, RET, SDHD, and SDHB, patients with pheochromocytoma, especially with bilateral disease, should be checked thoroughly for clinical lesions suggestive of underlying syndromes such as the cutaneous and ophthalmological features characteristic of NF 1.

Adolescent↗
PubMed2006

p53 down-regulates phosphatase and tensin homologue deleted on chromosome 10 protein stability partially through caspase-mediated degradation in cells with proteasome dysfunction.

There has been intense investigation regarding the interaction between the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and p53 tumor suppressors. p53 has been shown to up-regulate PTEN expression as a transcriptional activator. However, clinical observations by immunohistochemistry studies indicate that significant increases in p53 protein levels coexist with reduced or absent expression of PTEN protein in a variety of neoplasias. In this study, we propose a mechanism that begins to explain how p53 can both up-regulate and down-regulate PTEN. We have found that PTEN protein is down-regulated under proteasome dysfunction induced by proteasome inhibitor MG132 in both human lymphoblast cells and MCF7 cells. The reduction of PTEN is coincident with elevated p53 protein levels and the association between PTEN and p53 but independent of its phosphatase activities. Quantitative reverse transcription-PCR indicates that proteasome inhibition does not reduce PTEN message levels but affects PTEN protein stability. The p53 inhibitor, pifithrin-alpha, is able to attenuate the effect of proteasome inhibition. Using ectopic expression studies in p53-null mouse embryonic fibroblasts and p53/PTEN-null PC3 cells, we show that PTEN is more stable in p53-null cells compared with p53-expressing cells. Inhibition of caspases, the downstream targets of p53, particularly caspase-3, can partially restore the stability of PTEN. This study provides the first evidence that p53 is able to down-regulate PTEN protein stability in stressed cells. Our study sheds some light on the mechanisms that regulate PTEN protein stability, which is important to fully elucidate to comprehend the broad neoplastic manifestations of Cowden syndrome/Bannayan-Riley-Ruvalcaba and sporadic cancers.

Breast Neoplasms↗
PubMed2006

EPHB2 germline variants in patients with colorectal cancer or hyperplastic polyposis.

BACKGROUND: Ephrin receptor B2 (EPHB2) has recently been proposed as a novel tumor suppressor gene in colorectal cancer (CRC). Inactivation of the gene has been shown to correlate with progression of colorectal tumorigenesis, and somatic mutations have been reported in both colorectal and prostate tumors. METHODS: Here we have analyzed the EPHB2 gene for germline alterations in 101 individuals either with 1) CRC and a personal or family history of prostate cancer (PC), or 2) intestinal hyperplastic polyposis (HPP), a condition associated with malignant degeneration such as serrated adenoma and CRC. RESULTS: Four previously unknown missense alterations were observed, which may be associated with the disease phenotype. Two of the changes, I361V and R568W, were identified in Finnish CRC patients, but not in over 300 Finnish familial CRC or PC patients or more than 200 population-matched healthy controls. The third change, D861N, was observed in a UK HPP patient, but not in additional 40 UK HPP patients or in 200 UK healthy controls. The fourth change R80H, originally identified in a Finnish CRC patient, was also found in 1/106 familial CRC patients and in 9/281 healthy controls and is likely to be a neutral polymorphism. CONCLUSION: We detected novel germline EPHB2 alterations in patients with colorectal tumors. The results suggest a limited role for these EPHB2 variants in colon tumor predisposition. Further studies including functional analyses are needed to confirm this.

Adolescent↗
PubMed2006

Distinct expression profiles for PTEN transcript and its splice variants in Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome.

Cowden syndrome (CS) and Bannayan-Riley-Ruvalcaba syndrome (BRRS) are autosomal dominant hamartoma syndromes. Germline PTEN mutations have been associated with 85% of CS cases and 65% of BRRS cases and also with other disorders, which are collectively referred to as the "PTEN hamartoma tumor syndrome." The human PTEN gene has been previously found to express two naturally occurring splice variants (SVs). Recently, we identified eight novel naturally occurring PTEN SVs that result in different downstream signaling effects: SV3a, SV3b, SV3c (inclusion of various lengths of intron 3 3' of exon 3), SV5a, SV5b, SV5c, SV5d (inclusion of various lengths of intron 5 3' of exon 5), and SV Delta Ex6 (deletion of exon 6). We therefore sought to characterize the relative expression of 5', middle, and 3' full-length PTEN mRNA (FL-PTEN) and also of these eight PTEN SVs in 85 (65 female and 20 male) patients with CS/BRRS (with or without PTEN mutations) compared with 27 controls, using a SYBR green quantitative polymerase chain reaction method. Significantly reduced FL-PTEN levels were found in the probands, compared with those of controls (P < .01). Apart from FL-PTEN, SV3a is the most consistently relatively underexpressed in patients compared with controls. The patients showed relative underexpression of SV3a and SV3b and overexpression of SV5b (P = .005, P = .02, and P = .04, respectively). Indeed, there appears to be an SV expressional genotype-phenotype correlation in which the SV expressional profiles are distinct among CS, CS-like, and BRRS. The reduced FL-PTEN transcript expression, associated with differential expression of PTEN SVs, regardless of PTEN mutation status, supports the concept that modulation of PTEN inactivation may also occur at the transcription level influencing the specific phenotypes seen in these syndromes.

Base Sequence↗
PubMed2006

Increased PTEN expression due to transcriptional activation of PPARgamma by Lovastatin and Rosiglitazone.

Germline mutations in the tumor suppressor gene PTEN (protein phosphatase and tensin homolog located on chromosome ten) predispose to heritable breast cancer. The transcription factor PPARgamma has also been implicated as a tumor suppressor pertinent to a range of neoplasias, including breast cancer. A putative PPARgamma binding site in the PTEN promoter indicates that PPARgamma may regulate PTEN expression. We show here that the PPARgamma agonist Rosiglitazone, along with Lovastatin, induce PTEN in a dose- and time-dependent manner. Lovastatin- or Rosiglitazone-induced PTEN expression was accompanied by a decrease in phosphorylated-AKT and phosphorylated-MAPK and an increase in G1 arrest. We demonstrate that the mechanism of Lovastatin- and Rosiglitazone-associated PTEN expression was a result of an increase in PTEN mRNA, suggesting that this increase was transcriptionally-mediated. Compound-66, an inactive form of Rosiglitazone, which is incapable of activating PPARgamma, was unable to elicit the same response as Rosiglitazone, signifying that the Rosiglitazone response is PPARgamma-mediated. To support this, we show, using reporter assays including dominant-negative constructs of PPARgamma, that both Lovastatin and Rosiglitazone specifically mediate PPARgamma activation. Additionally, we demonstrated that cells lacking PTEN or PPARgamma were unable to induce PTEN mediated cellular events in the presence of Lovastatin or Rosiglitazone. These data are the first to demonstrate that Lovastatin can signal through PPARgamma and directly demonstrate that PPARgamma can upregulate PTEN at the transcriptional level. Since PTEN is constitutively active, our data indicates it may be worthwhile to examine Rosiglitazone and Lovastatin stimulation as mechanisms to increase PTEN expression for therapeutic and preventative strategies including cancer, diabetes mellitus and cardiovascular disease.

Antineoplastic Agents↗
PubMed2006

Contiguous gene deletion within chromosome arm 10q is associated with juvenile polyposis of infancy, reflecting cooperation between the BMPR1A and PTEN tumor-suppressor genes.

We describe four unrelated children who were referred to two tertiary referral medical genetics units between 1991 and 2005 and who are affected with juvenile polyposis of infancy. We show that these children are heterozygous for a germline deletion encompassing two contiguous genes, PTEN and BMPR1A. We hypothesize that juvenile polyposis of infancy is caused by the deletion of these two genes and that the severity of the disease reflects cooperation between these two tumor-suppressor genes.

Base Sequence↗
PubMed2006

Total-genome analysis of BRCA1/2-related invasive carcinomas of the breast identifies tumor stroma as potential landscaper for neoplastic initiation.

We have shown that the tumor microenvironment of sporadic breast cancer is diverse in genetic alterations and contributes to the cancer phenotype. The dynamic morphology of the mammary gland might be of special interest in hereditary breast/ovarian cancer syndrome (HBOC). We hypothesized that hotspots of loss of heterozygosity or allelic imbalance (LOH/AI) within the tumor stroma of BRCA1/2-related breast cancers provide an impaired mammary stroma that could facilitate later malignant transformation of the breast epithelium. We conducted a total genome LOH/AI scan of DNA derived from the epithelium and stroma of 51 BRCA1/2-related breast cancers, using 372 microsatellite markers. We compared these data with those from a set of 134 sporadic breast cancers. HBOC-related breast cancers accumulated significantly more genetic alterations than did sporadic breast cancers. BRCA1/2-related breast cancer stroma showed LOH/AI at 59.7% of all loci analyzed, similar to the average frequency of LOH/AI observed in the epithelium (66.2%). This is remarkably different from sporadic breast cancers, for which the average epithelial LOH/AI frequency (36.7%) far exceeds the average stromal LOH/AI frequency (28.4%) (P=.03). We identified 11 hotspot loci of LOH/AI in the BRCA1/2 stroma, encompassing genes such as POLD1, which functions in DNA replication, and SDHB. In a subset of samples, enriched for BRCA1 cases, we found 45.0% overall LOH/AI in the stroma, which was significantly higher than the 41.8% LOH/AI observed in corresponding epithelium (P=.04). Together, our data indicate that, in HBOC-related breast cancers, the accumulation of genomic instability in the cancer stroma coincides with that in the neoplastic epithelium, and we postulate that such a genetically unstable stroma might facilitate a microenvironment that functions as a landscaper that promotes genomic instability in the epithelium and, subsequently, neoplastic transformation.

Adult↗
PubMed2006

Spontaneous and therapeutic abortions and the risk of breast cancer among BRCA mutation carriers.

INTRODUCTION: BRCA1 and BRCA2 mutation carriers are at increased risk for developing both breast and ovarian cancer. It has been suggested that carriers of BRCA1/2 mutations may also be at increased risk of having recurrent (three or more) miscarriages. Several reproductive factors have been shown to influence the risk of breast cancer in mutation carriers, but the effects of spontaneous and therapeutic abortions on the risk of hereditary breast cancer risk have not been well studied to date. METHODS: In a matched case-control study, the frequencies of spontaneous abortions were compared among 1,878 BRCA1 mutation carriers, 950 BRCA2 mutation carriers and 657 related non-carrier controls. The rates of spontaneous and therapeutic abortions were compared for carriers with and without breast cancer. RESULTS: There was no difference in the rate of spontaneous abortions between carriers of BRCA1 or BRCA2 mutations and non-carriers. The number of spontaneous abortions was not associated with breast cancer risk among BRCA1 or BRCA2 mutation carriers. However, BRCA2 carriers who had two or more therapeutic abortions faced a 64% decrease in the risk of breast cancer (odds ratio = 0.36; 95% confidence interval 0.16-0.83; p = 0.02). CONCLUSION: Carrying a BRCA1 or BRCA2 mutation is not a risk factor for spontaneous abortions and spontaneous abortions do not appear to influence the risk of breast cancer in carriers of BRCA1 or BRCA2 mutations. However, having two or more therapeutic abortions may be associated with a lowered risk of breast cancer among BRCA2 carriers.

Abortion, Spontaneous↗
PubMed2006

Differential expression of novel naturally occurring splice variants of PTEN and their functional consequences in Cowden syndrome and sporadic breast cancer.

PTEN, a dual-phosphatase tumor suppressor, is inactivated in Cowden syndrome (CS), characterized by high risk of breast and thyroid cancer, and in variety of sporadic cancers. Despite the importance of alternative splicing, very limited information on its role in PTEN and associated cancers is available. We identified eight novel PTEN splice variants (SVs) that retained intron 3 regions (3a, 3b, 3c); intron 5 regions (5a, 5b, 5c); excluded part of exon 5 (DelE5) or all of exon 6 (DelE6), respectively. Analysis of SVs in 12 sporadic breast cancers revealed full-length (FL)-PTEN transcript reduction in 10; SVs 3b, 3c and 5c not expressed in 7, 6 and 4, respectively, and under-expressed in the rest. In contrast, SV-5b was over-expressed in breast cancers. PTEN SV analysis in 16 CS/CS-like patients and eight controls revealed that SV-5a is under-expressed and SV-3a over-expressed in the germline of CS/CS-like individuals when compared with controls. Although SV-5a expression decreased P-Akt level and cyclin D1 promoter activity, SVs 5b and 5c increased cyclin D1 promoter activity. Thus, SV-5a behaving like FL-PTEN corroborates our observation that SV-5a is under-expressed in CS when compared with controls. Similarly, SV-5b functionally counters PTEN's action and is over-expressed in sporadic breast cancers. Furthermore, we demonstrate that expression of these SVs is under the regulation of p53. Our observations suggest that differential expression of PTEN and its SVs could play a role in the pathogenesis of sporadic breast cancers and CS, and may lend a novel way of making a rapid molecular diagnosis of CS without mutation analysis.

Alternative Splicing↗
PubMed2006

PTEN autoregulates its expression by stabilization of p53 in a phosphatase-independent manner.

PTEN (phosphatase and tensin homologue, deleted on chromosome 10) is a tumor suppressor with dual phosphatase activity and mutations of its gene, PTEN, have been associated with many sporadic cancers and heritable neoplasia syndromes, including Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome. However, accumulating evidence now shows that PTEN may have novel functions other than as a phosphatase. In the present study, we show that PTEN is able to autoregulate its expression through the stabilization of another tumor suppressor p53. We further show that PTEN enhances p53 transactivation, a relationship that requires the interaction between PTEN and p53 and is PTEN phosphatase independent. We show that cell lines from Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome patients with germ line PTEN promoter mutations in the vicinity of the p53-binding motifs have altered p53 regulation. This seems to be due to reduced PTEN stability and decreased PTEN-p53 interactions. Our data provide clues to better understand the regulation of PTEN expression and the possible mechanisms of the pathogenesis of the subset of Cowden syndrome individuals with germ line promoter variation and who lack mutations in the PTEN coding region and splice sites. Importantly, this mechanism also holds for those sporadic tumors that lack intragenic mutations but have hemizygous deletion of PTEN, which includes the promoter region as manifested by loss-of-heterozygosity of 10q markers. The importance of our observations is underlined by the broad spectrum of neoplasias that harbor somatic PTEN or p53 alterations, or both.

Gene Expression Regulation↗
PubMed2006

Coffee consumption and breast cancer risk among BRCA1 and BRCA2 mutation carriers.

Although there are several plausible biologic mechanisms whereby coffee consumption might influence the risk of breast cancer, epidemiologic evidence is limited. We assessed the association between coffee consumption and breast cancer risk among high-risk women who carry BRCA mutations. We performed a matched case-control analysis on 1,690 women with a BRCA1 or BRCA2 mutation from 40 centers in 4 countries. Average lifetime coffee consumption was estimated via a self-administered questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. After adjustment for potential confounders, the ORs for breast cancer in BRCA carriers who habitually drank 0, 1-3, 4-5 and 6 or more cups of coffee were 1.00, 0.90 (95% CI 0.72-1.12), 0.75 (95% CI 0.47-1.19) and 0.31 (95% CI 0.13-0.71; p-trend = 0.02). The effect was limited to the consumption of caffeinated coffee. These results suggest that among women with BRCA gene mutation, coffee consumption is unlikely to be harmful and that high levels of consumption may in fact be related to reduced breast cancer risk.

Adult↗
PubMed2006

A complex additive model of inheritance for Hirschsprung disease is supported by both RET mutations and predisposing RET haplotypes.

PURPOSE: The RET proto-oncogene is considered to be the major susceptibility gene involved in Hirschsprung disease. Traditional RET germline mutations account for a small subset of Hirschsprung disease patients, but several studies have shown that there is a specific haplotype of RET associated with the sporadic forms of Hirschsprung disease. We have investigated for RET germline mutations and analyzed the RET haplotypic distribution in carriers versus noncarriers of RET germline mutations. METHODS: We have screened the coding region of RET in 106 Spanish Hirschsprung disease patients using dHPLC technology. Statistical comparisons of the distribution of RET haplotypes between sporadic patients with and without a RET germline mutation were performed. RESULTS: Nine novel germline mutations and one previously described were identified. A significant over-transmission of the "Hirschsprung disease haplotype" was detected when comparing transmitted versus nontransmitted alleles in the group of Hirschsprung disease triads without mutation. However, no distortion of the transmission of alleles was found in the group of mutated families. CONCLUSIONS: These results would be concordant with a complex additive model of inheritance. The whole findings seem to suggest that low-penetrance mutations would be necessary but not sufficient and the additional presence of the "Hirschsprung disease haplotype" could contribute to the manifestation of the disease.

DNA Mutational Analysis↗
PubMed2006

Functioning paraganglioma and gastrointestinal stromal tumor of the jejunum in three women: syndrome or coincidence.

Functioning paraganglioma and gastrointestinal stromal tumor (GIST) are uncommon tumors that occur mostly in a sporadic and isolated form, occasionally as components of multiple neoplasia syndromes, either separately or together. Separately, they occur in several inherited syndromes including multiple endocrine neoplasia 2, and the GIST, lentigines, and mast cell tumor syndrome. Together, they are variably prominent components of three syndromes: the familial paraganglioma and gastric GIST syndrome, neurofibromatosis type 1, and the Carney triad. The two former conditions are inherited as autosomal dominant traits; the latter does not appear to be inherited and affects young women predominantly. This article reports the nonfamilial occurrence of functioning paraganglioma and GIST of the jejunum in 3 women, 1 young (22 years) at initial presentation. The occurrences were unexpected because of the infrequency of the tumors. The neoplasms, respectively, did not show germline SDHA, SDHB, SDHC, and SDHD, and KIT mutations associated with familial paraganglioma and familial GIST. The paraganglioma-jejunal GIST combination may be the harbinger of a rare genetic syndrome, a variant of the Carney triad or the paraganglioma-gastric stromal sarcoma syndrome, or be coincidental.

Adult↗
PubMed2006

Familiality in Barrett's esophagus, adenocarcinoma of the esophagus, and adenocarcinoma of the gastroesophageal junction.

BACKGROUND AND AIM: The familial aggregation of Barrett's esophagus, adenocarcinoma of the esophagus, and adenocarcinoma of the gastroesophageal junction, jointly termed familial Barrett's esophagus, may represent a complex genetic trait. The aim of this study was to determine the proportion of patients with these diseases who have familial Barrett's esophagus. METHODS: Information on gastroesophageal reflux symptoms, known risk factors for Barrett's esophagus, and family history of Barrett's esophagus and cancers, was collected at six hospitals using a structured questionnaire from probands with either long-segment Barrett's esophagus, adenocarcinoma of the esophagus, or adenocarcinoma of the gastroesophageal junction. Family history of Barrett's esophagus or esophageal cancer in a first- or second-degree relative was determined by reviewing medical records of all relatives reported to be affected. RESULTS: Seventy one of 411 (17.3%) probands reported an affected first- and/or second-degree relative. Upon review of medical records of the reportedly affected relatives, familial Barrett's esophagus was definitively determined in the case of 30 (7.3%) probands comprising 17 of 276 (6.2%) with Barrett's esophagus, 11 of 116 (9.5%) with adenocarcinoma of the esophagus, and 2 of 21 (9.5%) with adenocarcinoma of the gastroesophageal junction. The diagnosis in the relative reported by the proband to be affected was found not to be Barrett's esophagus or adenocarcinoma in 15 (3.6%) cases. The diagnosis could not be determined in 26 (6.3%) cases in which the proband reported an affected relative. There were no significant differences in age of disease onset, gender, race, or gastroesophageal reflux symptoms between definitive familial Barrett's esophagus probands and nonfamilial probands. CONCLUSION: Familial Barrett's esophagus can be confirmed in 7.3% of persons presenting with Barrett's esophagus, adenocarcinoma of the esophagus, or adenocarcinoma of the gastroesophageal junction.

Adenocarcinoma↗
PubMed2006

Genetic and clinical investigation of pheochromocytoma: a 22-year experience, from Freiburg, Germany to international effort.

Although deceptively simple, the etio-pathogenesis of pheochromocytoma represents a clinical and molecular genetic investigative challenge. Here, we summarize, from a historical point of view, the 22-year-long studies initiated at the University of Freiburg, which developed from a local experience to a national and finally an international effort. All research activities are translational and clinical and hence, registry based and intended to improve the outcome of the patients, whether by improved detection, prevention, or treatment. Major clinical steps are the prospective study on hormone tests and imaging techniques for adrenal and extra-adrenal abdominal tumors as well as the concept of organ sparing and endoscopic tumor resection. Further, we introduced 18-fluoro-dopa positron emission tomography. Population-based registries were used in order to identify germline mutations in the susceptibility genes VHL, RET, SDHB, and SDHD in non-syndromic pheochromocytoma. We differentiated distinct clinical features of paraganglioma syndromes associated with SDHB and SDHD gene mutations. Finally, we identified predictors and prevalence of paraganglioma syndromes associated with mutations of the SDHC gene.

Adolescent↗