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Biomedical subjects

Thomas W Prior

Publications and source records attributed to Thomas W Prior.

At least 19 recordsLinked to original sources
PubMed2006

Screening for Lynch syndrome (hereditary nonpolyposis colorectal cancer) among endometrial cancer patients.

Endometrial cancer is the most common cancer in women with Lynch syndrome. The identification of individuals with Lynch syndrome is desirable because they can benefit from increased cancer surveillance. The purpose of this study was to determine the feasibility and desirability of molecular screening for Lynch syndrome in all endometrial cancer patients. Unselected endometrial cancer patients (N = 543) were studied. All tumors underwent microsatellite instability (MSI) testing. Patients with MSI-positive tumors underwent testing for germ line mutations in MLH1, MSH2, MSH6, and PMS2. Of 543 tumors studied, 118 (21.7%) were MSI positive (98 of 118 MSI high and 20 of 118 MSI low). All 118 patients with MSI-positive tumors had mutation testing, and nine of them had deleterious germ line mutations (one MLH1, three MSH2, and five MSH6). In addition, one case with an MSI-negative tumor had abnormal MSH6 immunohistochemical staining and was subsequently found to have a mutation in MSH6. Immunohistochemical staining was consistent with the mutation result in all seven truncating mutation-positive cases but was not consistent in two of the three missense mutation cases. We conclude that in central Ohio, at least 1.8% (95% confidence interval, 0.9-3.5%) of newly diagnosed endometrial cancer patients had Lynch syndrome. Seven of the 10 Lynch syndrome patients did not meet any published criteria for hereditary nonpolyposis colorectal cancer, and six of them were diagnosed at age >50. Studying all endometrial cancer patients for Lynch syndrome using a combination of MSI and immunohistochemistry for molecular prescreening followed by gene sequencing and deletion analysis is feasible and may be desirable.

Adaptor Proteins, Signal Transducing↗
PubMed2006

A feasibility study for the newborn screening of spinal muscular atrophy.

PURPOSE: The natural history of spinal muscular atrophy suggests that for maximum effect, therapeutics will need to be administered in the earliest phases of the disease. This will require the adoption of techniques for the genetic analysis of affected individuals at the newborn stage. Our objective was to examine the feasibility surrounding the newborn screening for spinal muscular atrophy. METHODS: We investigated the application of real-time polymerase chain reaction technology for newborn screening. A multiplex assay was designed to identify homozygous deletions in SMN1 exon 7 and validated using 266 samples with defined SMN1 and SMN2 copy numbers. Sensitivity and specificity were then evaluated as part of a newborn screening strategy using DNA from 153 blood spots. RESULTS: Real-time technology validation demonstrated correct exclusion of all normal and carrier samples, and identified the homozygous SMN1 exon 7 deletions in all 32 affected samples. In the series of blood spots, all 59 affected samples were correctly identified yielding an analytic sensitivity of 100%; 56 normal and 39 carrier samples were correctly excluded yielding an analytic specificity of 100% for this blood spot series. CONCLUSION: We demonstrate that effective molecular technology exists and that ethics may soon warrant the newborn screening of spinal muscular atrophy.

Computer Systems↗
PubMed2006

Detection of common disease-causing mutations in mitochondrial DNA (mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes MTTL1 3243 A>G and myoclonic epilepsy associated with ragged-red fibers MTTK 8344A>G) by real-time polymerase chain reaction.

The 3243A>G mutation in the MTTL1 (tRNA(Leu)) gene and the 8344A>G mutation in the MTTK (tRNA(Lys)) gene are the most common mutations found in mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes and myoclonic epilepsy associated with ragged-red fibers, respectively. These mitochondrial DNA mutations are usually detected by conventional polymerase chain reaction followed by restriction enzyme digestion and gel electrophoresis. We developed a LightCycler real-time polymerase chain reaction assay to detect these two mutations based on fluorescence resonance energy transfer technology and melting curve analysis. Primers and fluorescence-labeled hybridization probes were designed so that the sensor probe spans the mutation site. The observed melting temperatures differed in the mutant and wild-type DNA by 9 degrees C for the MTTL1 gene and 6 degrees C for the MTTK gene. This method correctly identified all 10 samples that were 3243A>G mutation-positive, all 4 samples that were 8344A>G mutation-positive, and all 30 samples that were negative for both mutations, as previously identified by traditional gel-based methods. This LightCycler assay is a rapid and reliable technique for molecular diagnosis of these mitochondrial gene mutations.

Adenosine↗
PubMed2006

Mutation screening in juvenile polyposis syndrome.

Juvenile polyposis syndrome (JPS) is an autosomal dominant cancer predisposition syndrome characterized by congenital anomalies, hamartomatous polyps in the gastrointestinal tract, and the development of tumors in these tissues. The diagnosis of JPS is often difficult because of the phenotypic overlap with other hamartomatous polyposis syndromes. Germline mutations have been identified in MADH4 and BMPR1A, aiding in presymptomatic genetic testing. In this study, we describe the results from 3 years of molecular diagnostic screening in JPS. Seventy unrelated individuals referred to our lab for JPS testing were examined through the sequence analysis of coding regions and exon-intron boundaries in both genes. Germline mutations were identified in 30% of cases, with 11.4% in BMPR1A and 18.6% in MADH4. All mutation-positive individuals were negative for cancer at testing, and a single pulmonary valve stenosis was the only congenital anomaly reported. A majority of mutations identified were novel including the first splice site alteration in MADH4. Based on the limited number of exons in each gene, low polymorphism frequency, and high frequency of frameshift or nonsense mutations identified, direct sequence analysis is a suitable methodology for mutation screening if all coding regions and exon-intron boundaries are examined in both genes.

Adult↗
PubMed2005

Molecular classification of patients with unexplained hamartomatous and hyperplastic polyposis.

CONTEXT: Significant proportions of patients with hamartomatous polyposis or with hyperplastic/mixed polyposis remain without specific clinical and molecular diagnosis or present atypically. Assigning a syndromic diagnosis is important because it guides management, especially surveillance and prophylactic surgery. OBJECTIVE: To systematically classify patients with unexplained hamartomatous or hyperplastic/mixed polyposis by extensive molecular analysis in the context of central rereview of histopathology results. DESIGN, SETTING, AND PATIENTS: Prospective, referral-based study of 49 unrelated patients from outside institutions (n = 28) and at a comprehensive cancer center (n = 21), conducted from May 2, 2002, until December 15, 2004. Germline analysis of PTEN, BMPR1A, STK11 (sequence, deletion), SMAD4, and ENG (sequence), specific exon screening of BRAF, MYH, and BHD, and rereview of polyp histology results were performed. MAIN OUTCOME MEASURES: Molecular, clinical, and histopathological findings in patients with unexplained polyposis. RESULTS: Of the 49 patients, 11 (22%) had germline mutations. Of 14 patients with juvenile polyposis, 2 with early-onset disease had mutations in ENG, encoding endoglin, previously only associated with hereditary hemorrhagic telangiectasia; 1 had hemizygous deletion encompassing PTEN and BMPR1A; and 1 had an SMAD4 mutation. One individual previously classified with Peutz-Jeghers syndrome had a PTEN deletion. Among 9 individuals with an unknown hamartomatous polyposis, 4 had mutations in STK11 (1), BMPR1A (2), and SMAD4 (1). Of the 23 patients with hyperplastic/mixed polyposis, 2 had PTEN mutations. Substantial discrepancies in histopathology results were seen. CONCLUSIONS: Systematic molecular classification of 49 patients with unexplained hamartomatous or hyperplastic polyposis uncovered a potential novel susceptibility gene, ENG, for juvenile polyposis. Importantly, given the substantial proportion of patients found to have germline mutations, more extensive analysis of the known susceptibility genes is indicated. Rereview of histology results by a dedicated gastrointestinal pathologist should be considered routinely, as organ-specific surveillance rests on defining syndromic diagnosis.

AMP-Activated Protein Kinase Kinases↗
PubMed2005

Somatic acquisition and signaling of TGFBR1*6A in cancer.

CONTEXT: TGFBR1*6A is a common polymorphism of the type I transforming growth factor beta receptor (TGFBR1). Epidemiological studies suggest that TGFBR1*6A may act as a tumor susceptibility allele. How TGFBR1*6A contributes to cancer development is largely unknown. OBJECTIVES: To determine whether TGFBR1*6A is somatically acquired by primary tumors and metastases during cancer development and whether the 3-amino acid deletion that differentiates TGFBR1*6A from TGFBR1 is part of the mature receptor or part of the signal sequence and to investigate TGFBR1*6A signaling in cancer cells. DESIGN, SETTING, AND PATIENTS: Tumor and germline tissues from 531 patients with a diagnosis of head and neck, colorectal, or breast cancer recruited from 3 centers in the United States and from 1 center in Spain from June 1, 1994, through June 30, 2004. In vitro translation assays, MCF-7 breast cancer cells stably transfected with TGFBR1*6A, TGFBR1, or the vector alone, DLD-1 colorectal cancer cells that endogenously carry TGFBR1*6A, and SW48 colorectal cancer cells that do not carry TGFBR1*6A. MAIN OUTCOME MEASURES: TGFBR1*6A somatic acquisition in cancer. Determination of the amino terminus of the mature TGFBR1*6A and TGFBR1 receptors. Determination of TGF-beta-dependent cell proliferation. RESULTS: TGFBR1*6A was somatically acquired in 13 of 44 (29.5%) colorectal cancer metastases, in 4 of 157 (2.5%) of colorectal tumors, in 4 of 226 (1.8%) head and neck primary tumors, and in none of the 104 patients with breast cancer. TGFBR1*6A somatic acquisition is not associated with loss of heterozygosity, microsatellite instability, or a mutator phenotype. The signal sequences of TGFBR1 and TGFBR1*6A are cleaved at the same site resulting in identical mature receptors. TGFBR1*6A may switch TGF-beta growth inhibitory signals into growth stimulatory signals in MCF-7 breast cancer cells and in DLD-1 colorectal cancer cells. CONCLUSIONS: TGFBR1*6A is somatically acquired in 29.5% of liver metastases from colorectal cancer and may bestow cancer cells with a growth advantage in the presence of TGF-beta. The functional consequences of this conversion appear to be mediated by the TGFBR1*6A signal sequence rather than by the mature receptor. The results highlight a new facet of TGF-beta signaling in cancer and suggest that TGFBR1*6A may represent a potential therapeutic target in cancer.

Activin Receptors, Type I↗
PubMed2005

Genetically characterized positive control cell lines derived from residual clinical blood samples.

BACKGROUND: Positive control materials for clinical diagnostic molecular genetic testing are in critically short supply. High-quality DNA that closely resembles DNA isolated from patient specimens can be obtained from Epstein-Barr virus (EBV)-transformed peripheral blood lymphocyte cell lines. Here we report the development of a process to (a) recover residual blood samples with clinically important mutations detected during routine medical care, (b) select samples likely to provide viable lymphocytes for EBV transformation, (c) establish stable cell lines and confirm the reported mutation(s), and (d) validate the cell lines for use as positive controls in clinical molecular genetic testing applications. METHODS: A network of 32 genetic testing laboratories was established to obtain anonymous, residual clinical samples for transformation and to validate resulting cell lines for use as positive controls. Three panel meetings with experts in molecular genetic testing were held to evaluate results and formulate a process that could function in the context of current common practices in molecular diagnostic testing. RESULTS: Thirteen laboratories submitted a total of 113 residual clinical blood samples with mutations for 14 genetic disorders. Forty-one EBV-transformed cell lines were established. Thirty-five individual point and deletion mutations were shown to be stable after 20 population doublings in culture. Thirty-three cell lines were characterized for specific mutations and validated for use as positive controls in clinical diagnostic applications. CONCLUSIONS: A process for producing and validating positive control cell lines from residual clinical blood samples has been developed. Sustainable implementation of the process could help alleviate the current shortage of positive control materials.

Blood Specimen Collection↗
PubMed2005

Screening for the Lynch syndrome (hereditary nonpolyposis colorectal cancer).

BACKGROUND: Germ-line mutations in the mismatch-repair genes MLH1, MSH2, MSH6, and PMS2 lead to the development of the Lynch syndrome (hereditary nonpolyposis colorectal cancer), conferring a strong susceptibility to cancer. We assessed the frequency of such mutations in patients with colorectal cancer and examined strategies for molecular screening to identify patients with the syndrome. METHODS: Patients with a new diagnosis of colorectal adenocarcinoma at the major hospitals in metropolitan Columbus, Ohio, were eligible for the study. Genotyping of the tumor for microsatellite instability was the primary screening method. Among patients whose screening results were positive for microsatellite instability, we searched for germ-line mutations in the MLH1, MSH2, MSH6, and PMS2 genes with the use of immunohistochemical staining for mismatch-repair proteins, genomic sequencing, and deletion studies. Family members of carriers of the mutations were counseled, and those found to be at risk were offered mutation testing. RESULTS: Of 1066 patients enrolled in the study, 208 (19.5 percent) had microsatellite instability, and 23 of these patients had a mutation causing the Lynch syndrome (2.2 percent). Among the 23 probands with the Lynch syndrome, 10 were more than 50 years of age and 5 did not meet the Amsterdam criteria or the Bethesda guidelines for the diagnosis of hereditary nonpolyposis colorectal cancer (including the use of age and family history to identify patients at high risk for the Lynch syndrome). Genotyping for microsatellite instability alone and immunohistochemical analysis alone each failed to identify two probands. In the families of 21 of the probands, 117 persons at risk were tested, and of these, 52 had Lynch syndrome mutations and 65 did not. CONCLUSIONS: Routine molecular screening of patients with colorectal adenocarcinoma for the Lynch syndrome identified mutations in patients and their family members that otherwise would not have been detected. These data suggest that the effectiveness of screening with immunohistochemical analysis of the mismatch-repair proteins would be similar to that of the more complex strategy of genotyping for microsatellite instability.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Natural history of denervation in SMA: relation to age, SMN2 copy number, and function.

Denervation was assessed in 89 spinal muscular atrophy (SMA) 1, 2, and 3 subjects via motor unit number estimation (MUNE) and maximum compound motor action potential amplitude (CMAP) studies, and results correlated with SMN2 copy, age, and function. MUNE and maximum CMAP values were distinct among SMA subtypes (p < 0.05). Changes in MUNE and maximum CMAP values over time were dependent on age, SMA type, and SMN2 copy number. SMN2 copy number less than 3 correlated with lower MUNE and maximum CMAP values (p < 0.0001) and worse functional outcomes. As SMN2 copy number increases, so does functional status (p < 0.0001). Change in MUNE longitudinally over the time intervals examined in this study was not statistically significant for any SMA cohort. However, a decline in maximum CMAP over time was apparent in SMA2 subjects (p = 0.049). Age-dependent decline in MUNE and maximum CMAP was apparent in both SMA 1 (p < 0.0001) and SMA 2 (p < 0.0001) subjects, with age as an independent factor regardless of type. Maximum CMAP at the time of the initial assessment was most predictive of functional outcome (p < 0.0001). Prospective longitudinal studies in four prenatally diagnosed infants demonstrated significant progressive denervation in association with symptomatic onset or functional decline. These data highlight the potential value of such measures in increasing our understanding of pathophysiological factors involved in denervation in SMA.

Activities of Daily Living↗
PubMed2005

Hydroxyurea enhances SMN2 gene expression in spinal muscular atrophy cells.

Spinal muscular atrophy (SMA) is a motor neuron disease caused by dysfunction of the survival motor neuron (SMN) gene. Human SMN gene is present in duplicated copies: SMN1 and SMN2. More than 95% of patients with SMA lack a functional SMN1 but retain at least one copy of SMN2. Unlike SMN1, SMN2 is primarily transcribed into truncated messenger RNA and produces low levels of SMN protein. We tested a therapeutic strategy by treating cultured lymphocytes from patients with SMA with hydroxyurea to modify SMN2 gene expression and to increase the production of SMN protein. Twenty lymphoblastoid cell lines (15 SMA and 5 control lines) were treated with hydroxyurea at 5 concentrations (0.5, 5, 50, 500, and 5,000 microg/ml) and 3 time points (24, 48, and 72 hours). SMN2 gene copy numbers were determined using real-time quantitative polymerase chain reaction. Hydroxyurea treatment resulted in a time-related and dose-dependent increase in the ratio of full-length to truncated SMN messenger RNA. SMN protein levels and intranuclear gems also were significantly increased in these hydroxyurea-treated cells. The SMN2 gene copy number correlated inversely with the SMA phenotypic severity. This study provides the first evidence for a therapeutic indication of hydroxyurea in SMA.

Blotting, Western↗
PubMed2005

Experience and strategy for the molecular testing of Duchenne muscular dystrophy.

Mutations in the dystrophin gene result in both Duchenne and Becker muscular dystrophies (DMD and BMD). Approximately two-thirds of the affected patients have large deletions or duplications. Using the multiplex polymerase chain reaction and Southern blotting techniques, the detection of these larger mutations is relatively straightforward. Detection of the point mutations in the remaining one-third of the patients has been challenging, mainly due to the large gene size and lack of hotspots or prevalent mutations. However, with the addition of some of the newer molecular screening methods, it is becoming more feasible for clinical laboratories to test for point mutations in the larger genes like dystrophin. Here we review the clinical features, describe the mutation distributions, evaluate current molecular strategies, and illustrate how the genetic findings have impacted the current clinical diagnostics of Duchenne and Becker muscular dystrophies.

Dystrophin↗
PubMed2005

Sphingosine kinase-1 expression correlates with poor survival of patients with glioblastoma multiforme: roles of sphingosine kinase isoforms in growth of glioblastoma cell lines.

Sphingosine-1-phosphate is a bioactive lipid that is mitogenic for human glioma cell lines by signaling through its G protein-coupled receptors. We investigated the role of sphingosine-1-phosphate receptors and the enzymes that form sphingosine-1-phosphate, sphingosine kinase (SphK)-1, and -2 in human astrocytomas. Astrocytomas of various histologic grades expressed three types of sphingosine-1-phosphate receptors, S1P1, S1P2, and S1P3; however, no significant correlation with histologic grade or patient survival was detected. Expression of SphK1, but not SphK2, in human astrocytoma grade 4 (glioblastoma multiforme) tissue correlated with short patient survival. Patients whose tumors had low SphK1 expression survived a median 357 days, whereas those with high levels of SphK1 survived a median 102 days. Decreasing SphK1 expression using RNA interference or pharmacologic inhibition of SphK significantly decreased the rate of proliferation of U-1242 MG and U-87 MG glioblastoma cell lines. Surprisingly, RNA interference to knockdown SphK2 expression inhibited glioblastoma cell proliferation more potently than did SphK1 knockdown. SphK knockdown also prevented cells from exiting G1 phase of the cell cycle and marginally increased apoptosis. Thus, SphK isoforms may be major contributors to growth of glioblastoma cells in vitro and to aggressive behavior of glioblastoma multiforme.

Adult↗
PubMed2004

Homozygous SMN1 deletions in unaffected family members and modification of the phenotype by SMN2.

Spinal muscular atrophy is a common autosomal recessive neuromuscular disorder caused by the homozygous loss of the SMN1 gene. The absence of the SMN1 gene has been shown to occur in all types of SMA, childhood and adult forms. In rare cases, asymptomatic family members have also been found with homozygous mutations in the SMN1 gene, suggesting a role for phenotypic modifiers. We describe three unrelated asymptomatic individuals, with family histories of SMA, who were shown to have the homozygous SMN1 deletion. Quantitative studies indicated that the three individuals all had increased SMN2 copy numbers. These cases not only support the role of SMN2 in modifying the phenotype, but our data also demonstrate that expression levels consistent with five copies of the SMN2 genes maybe enough to compensate for the absence of the SMN1 gene. Lastly, in cases similar to the ones described, the measurement of the SMN2 gene copy number may provide valuable prognostic information.

Adult↗
PubMed2003

Establishment of stably EBV-transformed cell lines from residual clinical blood samples for use in performance evaluation and quality assurance in molecular genetic testing.

Positive control materials for clinical molecular genetic testing applications are currently in critically short supply or non-existent for many genetically based diseases of public health importance. Here we demonstrate that anonymous, residual, clinical blood samples are potential sources of viable lymphocytes for establishing Epstein-Barr virus (EBV)-transformed blood lymphocyte cell lines. We attempted to transform 34 residual blood samples, and analyzed transformation success with respect to sample age, anticoagulant, storage temperature, volume, hemolysis, and patient age and sex. In univariate analysis, sample age was significantly associated with transformation success (P = 0.002). The success rate was 67% (6 of 9) for samples 1 to 7 days old, 38% (3 of 8) for samples 8 to 14 days old and 0% for samples 15 to 21 (0 of 11) days old. When we controlled for sample age in multivariate logistic regression, anticoagulant and storage temperature approached significance (P = 0.070 and 0.087, respectively; samples in acid citrate dextrose (ACD) and refrigerated samples were more likely to transform). Based on these findings, we suggest that samples collected in either ACD or ethylene diamine tetraacetic acid, and up to 14 days old (refrigerated) or 7 days old (stored ambient), are reasonable candidates for EBV transformation. The transformation rate for samples that met these criteria was 63% (10 of 16). Implementation of this process could help alleviate the shortage of positive control materials for clinical molecular genetic testing.

Adult↗
PubMed2003

Leigh disease with mitochondrial DNA A8344G mutation: case report and brief review.

Leigh disease, subacute necrotizing encephalomyelopathy, is a neurodegenerative disorder often seen in infancy or childhood but rarely reported in adults. Genetic heterogeneity is well recognized, and the associated etiologies include both mitochondrial and nuclear DNA defects. We describe an infant presenting with developmental delay and then progressive multisystem disorder and neuroradiologic features of Leigh disease. He and his maternal relatives all have the A8344G mitochondrial DNA mutation. However, only minor clinical features are seen in his maternal relatives, with migraine being the most common problem. Additionally the A8344G mitochondrial DNA mutation is associated with spinocerebellar degeneration, other nonspecific mitochondrial encephalomyopathies, atypical Charcot-Marie-Tooth disease, and progressive external ophthalmoplegia. The A8344G mitochondrial DNA mutation may present with Leigh disease or other different atypical clinical features without myoclonic epilepsy and ragged red fibers.

Brain↗
PubMed2002

A 39-bp deletion polymorphism in PTEN in African American individuals: implications for molecular diagnostic testing.

Germline mutations in the PTEN/MMAC1/TEP1 tumor suppressor gene cause Cowden syndrome (CS), a hereditary hamartoma-tumor syndrome with an increased risk of breast, thyroid, and endometrial cancers, and seemingly unrelated developmental disorders, such as Bannayan-Riley-Ruvalcaba (BRR) syndrome, Proteus, and Proteus-like syndromes. Data to date suggest that irrespective of the clinical presentation, the identification of a PTEN mutation should trigger medical management which includes cancer surveillance. Clinic-based molecular diagnostic testing for germline PTEN mutations has been available for at least 2 years. This study reports on the finding of a previously unobserved heterozygous alteration (IVS7-15-->53del39) found in an African American individual who had features of CS. Further investigation revealed that 12 of 42 (28.6%) African American controls, but not individuals of Caucasian or Japanese origin, also carried this heterozygous 39-bp deletion in PTEN. Due to its location immediately upstream of the splicing site of exon 8, this polymorphism could be mistaken for a deleterious mutation in the PTEN.

Base Sequence↗