Timothy T. Stenzel

Mutations in the activin receptor–like kinase 1 gene in hereditary haemorrhagic telangiectasia type 2

Hereditary haemorrhagic telangiectasia, or Osler–Rendu–Weber (ORW) syndrome, is an autosomal dominant vascular dysplasia. So far, two loci have been demonstrated for ORW. Linkage studies established an ORW locus at chromosome 9q3; endoglin was subsequently identified as the ORW1 gene. A second locus, designated ORW2, was mapped to chromosome 12. Here we report a new 4 cM interval for ORW2 that does not overlap with any previously defined. A 1.38–Mb YAC contig spans the entire interval. It includes the activin receptor like kinase 1 gene (ACVRLK1 or ALKI), a member of the serine–threonine kinase receptor family expressed in endothelium. We report three mutations in the coding sequence of the ALK1 gene in those families which show linkage of the ORW phenotype to chromosome 12. Our data suggest a critical role for ALK1 in the control of blood vessel development or repair.

Phase II Trial of Gefitinib in Recurrent Glioblastoma

PURPOSE To evaluate the efficacy and tolerability of gefitinib (ZD1839, Iressa; AstraZeneca, Wilmington, DE), a novel epidermal growth factor receptor tyrosine kinase inhibitor, in patients with recurrent glioblastoma. PATIENTS AND METHODS This was an open-label, single-center phase II trial. Fifty-seven patients with first recurrence of a glioblastoma who were previously treated with surgical resection, radiation, and usually chemotherapy underwent an open biopsy or resection at evaluation for confirmation of tumor recurrence. Each patient initially received 500 mg of gefitinib orally once daily; dose escalation to 750 mg then 1,000 mg, if a patient received enzyme-inducing antiepileptic drugs or dexamethasone, was allowed within each patient. RESULTS Although no objective tumor responses were seen among the 53 assessable patients, only 21% of patients (11 of 53 patients) had measurable disease at treatment initiation. Seventeen percent of patients (nine of 53 patients) underwent at least six 4-week cycles, and the 6-month event-free survival (EFS) was 13% (seven of 53 patients). The median EFS time was 8.1 weeks, and the median overall survival (OS) time from treatment initiation was 39.4 weeks. Adverse events were generally mild (grade 1 or 2) and consisted mainly of skin reactions and diarrhea. Drug-related toxicities were more frequent at higher doses. Withdrawal caused by drug-related adverse events occurred in 6% of patients (three of 53 patients). Although the presence of diarrhea positively predicted favorable OS from treatment initiation, epidermal growth factor receptor expression did not correlate with either EFS or OS. CONCLUSION Gefitinib is well tolerated and has activity in patients with recurrent glioblastoma. Further study of this agent at higher doses is warranted.

Molecular Genetic Aspects of Oligodendrogliomas Including Analysis by Comparative Genomic Hybridization

Oligodendroglial neoplasms are a subgroup of gliomas with distinctive morphological characteristics. In the present study we have evaluated a series of these tumors to define their molecular profiles and to determine whether there is a relationship between molecular genetic parameters and histological pattern in this tumor type. Loss of heterozygosity (LOH) for 1p and 19q was seen in 17/23 (74%) well-differentiated oligodendrogliomas, in 18/23 (83%) anaplastic oligodendrogliomas, and in 3/8 (38%) oligoastrocytomas grades II and III. LOH for 17p and/or mutations of the TP53 gene occurred in 14 of these 55 tumors. Only one of the 14 cases with 17p LOH/TP53 gene mutation also had LOH for 1p and 19q, and significant astrocytic elements were seen histologically in the majority of these 14 tumors. LOH for 9p and/or deletion of the CDKN2A gene occurred in 15 of these 55 tumors, and 11 of these cases were among the 24 (42%) anaplastic oligodendrogliomas. Comparative genomic hybridization (CGH) identified the majority of cases with 1p and 19q loss and, in addition, showed frequent loss of chromosomes 4, 14, 15, and 18. These findings demonstrate that oligodendroglial neoplasms usually have loss of 1p and 19q whereas astrocytomas of the progressive type frequently contain mutations of the TP53 gene, and that 9p loss and CDKN2A deletions are associated with progression from well-differentiated to anaplastic oligodendrogliomas.

Progress Report of a Phase I Study of the Intracerebral Microinfusion of a Recombinant Chimeric Protein Composed of Transforming Growth Factor (TGF)-α and a Mutated form of the Pseudomonas Exotoxin Termed PE-38 (TP-38) for the Treatment of Malignant Brain Tumors

TP-38 is a recombinant chimeric targeted toxin composed of the EGFR binding ligand TGF-α and a genetically engineered form of the Pseudomonas exotoxin, PE-38. After in vitro and in vivo animal studies that showed specific activity and defined the maximum tolerated dose (MTD), we investigated this agent in a Phase I trial. The primary objective of this study was to define the MTD and dose limiting toxicity of TP-38 delivered by convection-enhanced delivery in patients with recurrent malignant brain tumors. Twenty patients were enrolled in the study and doses were escalated from 25ng/mL to 100 with a 40mL infusion volume delivered by two catheters. One patient developed Grade IV fatigue at the 100ng/mL dose, but the MTD has not been established. The overall median survival after TP-38 for all patients was 23 weeks whereas for those without radiographic evidence of residual disease at the time of therapy, the median survival was 31.9 weeks. Overall, 3 of 15 patients, with residual disease at the time of therapy, have demonstrated radiographic responses and one patient with a complete response and has survived greater than 83 weeks.

The integration host factor of Escherichia coli binds to bent DNA at the origin of replication of the plasmid pSC101.

The integration host factor (IHF) of Escherichia coli is necessary for maintenance of pSC101. The protein binds specifically to the replication origin of the plasmid, in the AT-rich region located immediately adjacent to the left, weak binding site for the plasmid-encoded initiator protein. DNAase I and OH- radical footprinting experiments showed that IHF protects 49 bp of the DNA at the origin region. Methylation protection analyses revealed that IHF contacts purine residues in both the major and minor grooves of the DNA. Electrophoretic analyses showed that IHF binds to bent DNA, and the protein binding further enhances the degree of DNA bending. Site-directed mutagenesis of three of the contact points not only abolished binding of the protein to the DNA but also inactivated the replication origin. Therefore, binding of IHF to the ori sequence most probably is necessary for initiation of plasmid replication.

An Information-Rich CGG Repeat Primed PCR That Detects the Full Range of Fragile X Expanded Alleles and Minimizes the Need for Southern Blot Analysis

(CGG)(n) repeat expansion in the FMR1 gene is associated with fragile X syndrome and other disorders. Current methods for FMR1 molecular testing rely on Southern blot analysis to detect expanded alleles too large to be PCR-amplified and to identify female homozygous alleles that often confound interpretations of PCR data. A novel, single-tube CGG repeat primed FMR1 PCR technology was designed with two gene-specific primers that flank the triplet repeat region, as well as a third primer that is complementary to the (CGG)(n) repeat. This PCR was evaluated with 171 unique DNA samples, including a blinded set of 146 clinical specimens. The method detected all alleles reported by Southern blot analysis, including full mutations in 66 clinical samples and comprised up to 1300 CGG. Furthermore, a blinded cohort of 42 female homozygous and heterozygous specimens, including 21 with full mutation alleles, was resolved with 100% accuracy. Last, AGG interrupter sequences, which may influence the risk of (CGG)(n) expansion in the children of some carriers, were each correctly identified in 14 male and female clinical samples as referenced to DNA sequencing. As a result, this PCR provides robust detection of expanded alleles and resolves allele zygosity, thus minimizing the number of samples that require Southern blot analysis and producing more comprehensive FMR1 genotyping data than other methods.

Quality control in molecular genetic testing

DNA-based testing for genetic diseases has developed from nothing into a principal part of laboratory medicine over the past 15 years. In the rush to bring these powerful new technologies into medical use, issues of quality have not always been given sufficient attention. Efforts are now being made to assess the quality of the output of genetic testing laboratories, and the results show that there is room for improvement.

Mutation and expression analysis of the endoglin gene in hereditary hemorrhagic telangiectasia reveals null alleles

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent hemorrhage from the sites of vascular lesions. Two genes have been identified for HHT. Endoglin, a TGF‐β binding protein which maps to chromosome 9q3, is the gene for HHT1. The type and location of most of the previously described mutations in the endoglin (ENG) gene suggested a dominant‐negative model of receptor–complex dysfunction for the molecular basis of this disorder. In this article we describe 11 novel ENG mutations in HHT kindreds, which include missense and splice‐site mutations. Two identical missense mutations in unrelated families disrupt the start codon of the gene. In addition, some frameshift and nonsense mutations lead to very low or undetectable levels of transcript from the mutant allele. These combined data suggest that the nature of most ENG mutations is to create a null (nonfunctional) allele, and that there is no requirement for the synthesis of a truncated endoglin protein in the pathogenesis of HHT. Hum Mutat 11:286–294, 1998.

Burkitt lymphoma arising in organ transplant recipients: a clinicopathologic study of five cases.

We report five cases of Burkitt lymphoma arising in organ transplant recipients. There were four men and one woman with a mean age of 35 years. All were solid organ recipients with three renal, one liver, and one double lung transplantation. The time interval between organ transplantation and lymphoma averaged 4.5 years. Patients typically presented with high-stage disease with generalized lymphadenopathy and bone marrow involvement. Histology showed classic Burkitt lymphoma or atypical variant/Burkitt-like morphology. C-MYC rearrangement, including three cases with immunoglobulin heavy chain and two cases with lambda light chain, and Epstein-Barr virus were detected in all the cases. Additional chromosomal abnormalities were present in two of three cases and p53 mutation was found in one of three cases. Aberrant genotype and phenotype were frequently encountered, including minor monoclonal or oligoclonal T-cell populations and undetectable surface immunoglobulin light chain expression. Four patients received antilymphoma regimens, with combination chemotherapy (three patients) and/or Rituximab (three patients), in addition to reduction of immunosuppression. All four patients achieved complete remission. We conclude that posttransplant Burkitt lymphoma represents a characteristic clinicopathologic entity and occurs later after transplantation. Genotypic and phenotypic aberrations are often present. Rituximab may be an effective alternative to conventional combination chemotherapy in the treatment of a posttransplant Burkitt lymphoma.

Molecular markers of prognosis in astrocytic tumors

Astrocytoma is a primary brain tumor that affects 20,000 Americans each year. To date, only age and histologic grade stand out as independent predictors of survival. There is now increased interest in the use of molecular markers as objective standards against which to establish diagnosis and grade.