Effect of everolimus on skin lesions in patients treated for subependymal giant cell astrocytoma and renal angiomyolipoma: final 4-year results from the randomized EXIST-1 and EXIST-2 studies

BACKGROUND

Tuberous sclerosis complex (TSC) is a genetic disorder associated with tumour growth in various organs, including the brain, kidneys, heart and skin. Cutaneous lesions are prevalent manifestations of TSC, occurring in up to 90% of patients. Oral mammalian target of rapamycin inhibitors, such as everolimus, is believed to be effective for treatment of TSC-associated lesions because they act on the underlying disease pathophysiology.

OBJECTIVE

We evaluated the long-term effect of oral everolimus on TSC-associated skin lesions as a secondary objective in the phase III studies EXIST-1 (NCT00789828) and EXIST-2 (NCT00790400) after approximately 4 years of treatment.

MATERIALS AND METHODS

Everolimus was dosed 4.5 mg/m² /day (titrated to trough 5-15 ng/mL) in patients with TSC-associated subependymal giant cell astrocytoma in EXIST-1, and 10 mg/day initially in adult patients with TSC- or sporadic lymphangioleiomyomatosis-associated renal angiomyolipoma in EXIST-2. Following positive results from the core phase, remaining patients were offered open-label everolimus in an extension. Skin lesion response rate was the proportion of patients achieving complete or partial clinical response.

RESULTS

A total of 105 patients in EXIST-1 and 107 in EXIST-2 received everolimus and had ≥1 skin lesion at baseline. Skin lesion response rate (95% confidence interval) was 58.1% (48.1-67.7%) in EXIST-1 and 68.2% (58.5-76.9%) in EXIST-2; most were partial responses. At week 192 (EXIST-1: n = 55; EXIST-2: n = 56), 69% and 66% had a response. Most common drug-related adverse event was stomatitis (41-45%).

CONCLUSION

Oral everolimus improved TSC-related skin lesions, with responses sustained over 4 years of treatment in EXIST-1 and EXIST-2.

Tuberous sclerosis complex: neurological, renal and pulmonary manifestations

Tuberous sclerosis complex (TSC) is an important cause of epilepsy and autism, as well as renal and pulmonary disease in adults and children. Affected individuals are subject to hamartomas in various organ systems which result from constitutive activation of the protein kinase mTOR (mammalian target of rapamycin). The clinical course, prognosis and appropriate therapy for TSC patients are often different from that for individuals with epilepsy, renal tumors, or interstitial lung disease, from other causes. Additionally, TSC serves as a model for other conditions in which the mTOR pathways are also up-regulated. This article reviews the molecular pathophysiology and management of neurological, renal and pulmonary manifestations of the disorder. The use of mTOR inhibitors such as rapamycin and everolimus is discussed and recent clinical trials of these drugs in TSC are reviewed.

Hematuria in children

Children with hematuria require a thorough history and physical examination. Not all children with hematuria require the same investigations. The only laboratory test uniformly required for children with the various presentations of hematuria is a complete urinalysis with a microscopic examination. The rest of the evaluation is tailored according to the pertinent history, physical examination, and other abnormalities on the urinalysis. This article has provided a brief summary of the more common causes of pediatric hematuria and suggestions for tailoring the patient's evaluation according to the presentation. Most causes of hematuria in pediatrics represent medical conditions that often require referral to a pediatric nephrologist. Indications for referral to a urologist are more limited and include stones that do not pass spontaneously or are more than 5 mm in diameter, renal injury from trauma, anatomic abnormalities, or gross hematuria that seems to originate from the urinary tract and is without an identified cause.

Hemolytic uremic syndrome in an adolescent with Fusobacterium necrophorum bacteremia

Microorganisms may produce substances that disrupt the interaction between platelets and vascular endothelium, which has been associated with atypical hemolytic uremic syndrome (HUS). We present the first reported case of Fusobacterium necrophorum bacteremia that presented initially with atypical HUS. Antimicrobial therapy eradicated the patient's bacteremia, and plasmapheresis restored platelet-endothelial homeostasis. Understanding the pathophysiologic mechanisms involved in atypical HUS would guide the development of more precise therapies.

Overcoming a barrier for DNA polymerization in triplex-forming sequences

Folded structures in the DNA template, such as hairpins and multi-stranded structures, often serve as pause and arrest sites for DNA polymerases. DNA polymerization is particularly difficult on mirror-repeated homopurine.homopyrimidine templates where triple-stranded (triplex) structures may form between the nascent and folded template strands. In order to use a linear PCR amplification approach for the structural analysis of DNA in mirror-repeated sequences we modified a conventional protocol. The barrier for DNA synthesis can be eliminated using an oligonucleotide that hybridizes with the template to prevent its folding and is subsequently displaced by the progressing polymerase. The described approach is potentially useful for sequencing and analysis of chemical adducts and point mutations in a variety of sequences prone to the formation of folded structures, such as long hairpins and quadruplexes.

DNA structural transitions within the PKD1 gene

Autosomal dominant polycystic kidney disease (ADPKD) affects over 500 000 Americans. Eighty-five percent of these patients have mutations in the PKD1 gene. The focal nature of cyst formation has recently been attributed to innate instability in the PKD1 gene. Intron 21 of this gene contains the largest polypurine. polypyrimidine tract (2.5 kb) identified to date in the human genome. Polypurine.polypyrimidine mirror repeats form intramolecular triplexes, which may predispose the gene to mutagenesis. A recombinant plasmid containing the entire PKD1 intron 21 was analyzed by two-dimensional gel electrophoresis and it exhibited sharp structural transitions under conditions of negative supercoiling and acidic pH. The superhelical density at which the transition occurred was linearly related to pH, consistent with formation of protonated DNA structures. P1 nuclease mapping studies of a plasmid containing the entire intron 21 identified four single-stranded regions where structural transitions occurred at low superhelical densities. Two-dimensional gel electrophoresis and chemical modification studies of the plasmid containing a 46 bp mirror repeat from one of the four regions demonstrated the formation of an H-y3 triplex structure. In summary, these experiments demonstrate that a 2500 bp polypurine.polypyrimidine tract within the PKD1 gene is capable of forming multiple non-B-DNA structures.

The promoter of the C1 inhibitor gene contains a polypurine.polypyrimidine segment that enhances transcriptional activity

The C1 inhibitor (C1INH) promoter is unusual in two respects: 1) It contains no TATA sequence, but instead contains a TdT-like initiator element (Inr) at nucleotides -3 to +5; 2) it contains a polypurine.polypyrimidine tract between nucleotides -17 and -45. Disruption of the Inr by the introduction of point mutations reduced promoter activity by 40%. A TATA element inserted at nucleotide -30 in the wild-type promoter and in promoter constructs containing the mutated Inr led to a 2-fold increase in basal promoter activity. Previous studies suggested that the potential hinged DNA-forming polypurine.polypyrimidine tract might be important in the regulation of C1INH promoter activity. The present studies indicate that this region is capable of such intramolecular triple helix formation. Disruption of the polypurine.polypyrimidine sequence by substitution of 5 of the 23 cytosine residues with adenine prevented triple helix formation. Site-directed mutagenesis experiments demonstrate that the regulation of promoter activity is independent of hinged DNA-forming capacity but requires an intact AC box (ACCCTNNNNNACCCT) or the overlapping PuF binding site (GGGTGGG). The C1INH gene also contains a number of potential regulatory elements, including an Sp-1 and an hepatocyte nuclear factor-1 binding site and a CAAT box. The role of these elements in regulation of the C1INH promoter was examined. Elimination of the hepatocyte nuclear factor-1 site at nucleotides -94 to -81 by truncation reduced the activity of the promoter by approximately 50%. Similarly, site-directed mutations that disrupt this site reduce promoter activity by 70%.

C1 inhibitor gene sequence facilitates frameshift mutations

Mutations disrupting the function or production of C1 inhibitor cause the disease hereditary angioneurotic edema. Patient mutations identified an imperfect inverted repeat sequence that was postulated to play a mechanistic role in the mutations. To test this hypothesis, the inverted repeat was cloned into the chloramphenicol acetyltransferase gene in pBR325 and its mutation rate was studied in four bacterial strains. These strains were selected to assay the effects of recombination and superhelical tension on mutation frequency. Mutations that revert bacteria to chloramphenicol resistance (Cmr) were scored. Both pairs of isogenic strains had reversion frequencies of approximately 10(-8). These rare reversion events in bacteria were most often a frameshift that involved the imperfect inverted repeat with a deletion or a tandem duplication, an event very similar to the human mutations. Increased DNA superhelical tension, which would be expected to enhance cruciform extrusion, did not accentuate mutagenesis. This finding suggests that the imperfect inverted repeat may form a stem-loop structure in the single-stranded DNA created by the duplex DNA melting prior to replication. Models explaining the slippage can be drawn using the lagging strand of the replication fork. In this model, the formation of a stem-loop structure is responsible for bringing the end of the deletion or duplication into close proximity.

DNA inverted repeats and human disease

Inverted repeats are important elements in the human genome. Because of their nature, inverted repeats can engage in intra- and intermolecular basepairing. The ability to adopt hairpin and cruciform secondary structures is associated with frameshift mutations. These sequences also can be utilized by the polymerase allowing both intra- and interstrand switching events. Such mechanisms can involve imperfect inverted repeats and lead to additional mutations. Several human genetic diseases illustrate inverted repeat mediated mutagenesis.

Molecular defects in hereditary angioneurotic edema

Thirty-eight previously unreported, unrelated patients with hereditary angioneurotic edema were studied, and each was found to have a single mutation in the C1 inhibitor gene. On the basis of serine protease inhibitor crystal structure, these and published mutations affect critical domains in the reactive center loop, alpha-helices A, B, C, E, and F, and beta-sheets A and C. Almost all mutations, other than in the reactive center loop, occur at residues that are highly conserved among serine protease inhibitors, and the others are likely to interfere with molecular movement. These mutations begin to identify residues critical for molecular function of the C1 inhibitor molecule.

Antibody to C1-inhibitor in a patient receiving C1-inhibitor infusions for treatment of hereditary angioneurotic edema with systemic lupus erythematosus reacts with a normal allotype of residue 458 of C1-inhibitor

Patients with hereditary C4 deficiency are likely to have severe lupus erythematosus. A patient with hereditary angioneurotic edema (HANE) and systemic lupus erythematosus (SLE) had a chronic deficiency in C4 because the hereditary deficiency in C1-inhibitor allowed the C1 in her serum to become activated and then inactivate C4. An attempt was made to repair the C4 deficiency as well as the deficiency in C1-inhibitor by giving infusions of human C1-inhibitor in the hope of inducing remissions of both HANE and SLE. During treatment, antibody to C1-inhibitor developed in the patient; this cleared when the infusions were stopped. During subsequent treatment with danazol alone, measurable C1-inhibitor developed in the patient's serum, but levels of C4 were never significantly increased. Antibody to normal C1-inhibitor was not expected to develop in the patient because she is heterozygous for this autosomal dominant trait. A normal allotype (VAL or MET 458), which would have been in the preparation used but which the patient does not synthesize because she can produce only one allotype (MET 458), appears to have been immunogenic. The antibody isolated from the patient's serum reacted with C1-inhibitor from a normal individual known to be homozygous for 458-VAL but not with one from a homozygote for MET-458.

Unique C1 inhibitor dysfunction in a kindred without angioedema. II. Identification of an Ala443-->Val substitution and functional analysis of the recombinant mutant protein

We have determined the cause of an unusual C1 inhibitor abnormality in a large kindred. We previously found that half of serum C1 inhibitor molecules in affected kindred members are normal. The other half complexed with C1s but showed little complex formation with C1r. These molecules also appeared to be relatively resistant to digestion by trypsin. Taken together, the findings suggested that members of this kindred are heterozygous for an unusual C1 inhibitor mutation. Sequencing of genomic DNA from the kindred revealed that thymine has replaced cytosine in the codon for Ala443 (P2 residue) in one C1 inhibitor allele, resulting in substitution with a Val residue. To test the effect of this substitution, a mutant C1 inhibitor containing Ala443-->Val was constructed by site-directed mutagenesis and expressed in COS-1 cells. Both the Ala443-->Val mutant and the wild-type C1 inhibitor complexed completely with C1s, kallikrein, and coagulation Factor XIIa after incubation at 37 degrees C for 60 min. In contrast, the mutant inhibitor failed to complex completely with C1r under the same conditions. Time course analysis showed that the ability of the mutant to complex with C1s is also impaired: although it complexed completely in 60 min, the rate of complex formation during a 0-60-min incubation was decreased compared with wild-type C1 inhibitor. The mutant inhibitor also formed a complex with trypsin, a serine protease that cleaves, and is not inhibited by, wild-type C1 inhibitor. The Ala443-->Val mutation therefore converts C1 inhibitor from a substrate to an inhibitor of trypsin. These studies emphasize the role of the P2 residue in the determination of target protease specificity.

A cluster of mutations within a short triplet repeat in the C1 inhibitor gene

Mutations in the C1 inhibitor gene that result in low functional levels of C1 inhibitor protein cause hereditary angioneurotic edema. This disease is characterized by episodic edema leading to considerable morbidity and death. Among 60 unreported kindred with the disease, four patients were discovered to have mutations clustered within a 12-bp segment of exon 5 from nucleotide 8449 to nucleotide 8460. This short segment of DNA contains three direct repeats of the triplet CAA and is immediately preceded by a similar adenosine-rich sequence (CAAGAACAC). These triplet repeats make this region susceptible to mutation by a slipped mispairing mechanism. There are two other short triplet repeat elements in the coding region for this gene, but they have not become mutated in any kindred examined. This suggests that the apparent enhanced mutation rate in this region of exon 5 may be influenced by DNA structural characteristics.

Contiguous deletion and duplication mutations resulting in type 1 hereditary angioneurotic edema

Mutations that cause low antigenic and functional levels of C1 inhibitor protein result in type 1 hereditary angioneurotic edema. This disease is characterized by episodic edema leading to considerable morbidity and sometimes death. We present here two novel mutations in the reactive center coding region. One mutation is a deletion of an imperfect palindrome encompassing nucleotides 1395-1428 and the other is a direct duplication of nucleotides 1414-1433. These mutations do not depend on improper pairing of direct repeats, but may form as a consequence of a peculiar consensus sequence or an alternative secondary structure.

Mutations in the C1 inhibitor gene that result in hereditary angioneurotic edema

Mutations in one C1 INH allele result in the autosomal dominant disease, hereditary angioedema. The plasma antigenic level of C1 INH in this disease may be low, normal, or high, while the functional level is uniformly depressed. Investigation of the mutations in the C1 INH gene reveal several key features about the DNA itself as well as protein structure-function relationships. The largest single group of mutations with a defined mechanism are recombinations associated with Alu repetitive DNA elements. Current data suggest that there may be an increased number of mutations within the region encoding the reactive center which, like some other serpins, contains both primary and secondary structure DNA polymerase pause sites. These sites may enhance the rates of mutation and evolution in the reactive center region. Some of the dysfunctional C1 INH proteins that result from hinge region mutations support models for reactive center loop interaction with beta sheet A during complex formation. The analysis of the dysfunctional mutants, therefore, suggest regions of the molecule that are important for inhibitor function.

Hemothorax as a complication following percutaneous renal biopsy

Percutaneous renal biopsy is a routine procedure with a low complication rate. We report a patient who developed shock and respiratory distress secondary to hemothorax following a fluoroscopically guided biopsy.

Cardiomyocyte aging and hypertrophy: atrial and ventricular changes in normal and myopathic Syrian hamsters

Cardiac eccentric hypertrophy is associated with complex architectural and metabolic alterations. Atrial and ventricular myocyte diameters in cardiomyopathic (Bio 14.6) and age-matched control (F1b) Syrian hamsters were compared and histopathology was examined by electron microscopy. The mean diameter of ventricular myocyte diameters increased with age in both F1b and Bio 14.6 hamsters. Significantly greater hypertrophy was noted in the Bio 14.6 left ventricle myocytes than the F1b. Histo- and cytopathologic findings included amitotic myocardial divisions and focal myocyte necrosis in Bio hearts. Sarcomere length appeared to be similar across age and strain; however, wider sarcomeres were found in conjunction with wider diameters of myopathic left ventricle myocytes. Moreover, F1b hamsters' atrial myocytes maintained a static diameter, while those of the Bio 14.6 showed hypertrophy even preceding ventricular changes. These findings indicated that the cardiomyopathic heart is characterized by a continued fiber hypertrophy despite cardiac decompensation. Other histopathological findings included amitotic myocardial divisions, focal necrosis and sarcoplasmic widening of Z-lines. In addition, vascular smooth muscles of Bio 14.6 demonstrated vacuolization.

Alimentary tract duplications in children: case and literature review

This report reviews 11 alimentary tract duplications over a 25-year experience at Children's Hospital Medical Center of Akron, Ohio. The cases are compared and contrasted to the literature with respect to lesion, location, and patient presentation. There were no multiple duplications in this series. Clinical presentations were related to obstruction, abdominal pain, and/or hemorrhage. There were four foregut duplications, five midgut duplications, and two hindgut lesions. All patients were treated by surgical removal and all survived. One case was an incidental finding at appendectomy. Pooled data from five large series of duplications revealed the ileal region to be involved in 41 percent of all duplications, followed by esophageal (21%), gastroduodenal (12%), and jejunal (8%). Diverticular, recanalization, and split notochord theories of pathogenesis are discussed. The curious association between duplications and gastric mucosa is explored.