Stabilization of HIF-2α through redox regulation of mTORC2 activation and initiation of mRNA translation.

Hypoxia inducible factor-2α (HIF-2α) has a critical role in renal tumorigenesis. HIF-2α is stabilized in von Hippel-Lindau (VHL)-deficient renal cell carcinoma through mechanisms that require ongoing mRNA translation. Mammalian target of rapamycin (mTOR) functions in two distinct complexes: Raptor-associated mTORC1 and Rictor-associated mTORC2. Rictor-associated mTORC2 complex has been linked to maintaining HIF-2α protein in the absence of VHL; however, the mechanisms remain to be elucidated. Although Raptor-associated mTORC1 is a known key upstream regulator of mRNA translation, initiation and elongation, the role of mTORC2 in regulating mRNA translation is not clear. Complex assembly of the mRNA cap protein, eukaryotic translation initiation factor 4 (eIF4)E, with activators (eIF4 gamma (eIF4G)) and inhibitors (eIF4E-binding protein 1 (4E-BP1)) are rate-limiting determinants of mRNA translation. Our laboratory has previously demonstrated that reactive oxygen species, mediated by p22(phox)-based Nox oxidases, are enhanced in VHL-deficient cells and have a role in the activation of Akt on S473, a site phosphorylated by the mTORC2 complex. In this study, we examined the role of Rictor-dependent regulation of HIF-2α through eIF4E-dependent mRNA translation and examined the effects of p22(phox)-based Nox oxidases on TORC2 regulation. We demonstrate for the first time that mTORC2 complex stability and activation is redox sensitive, and further defined a novel role for p22(phox)-based Nox oxidases in eIF4E-dependent mRNA translation through mTORC2. Furthermore, we provide the first evidence that silencing of p22(phox) reduces HIF-2α-dependent gene targeting in vitro and tumor formation in vivo. The clinical relevance of these studies is demonstrated.

The clinical spectrum in a large kindred with autoimmune lymphoproliferative syndrome caused by a Fas mutation that impairs lymphocyte apoptosis.

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by chronic, histologically benign splenomegaly and generalized lymphadenopathy, hypergammaglobulinemia, and autoantibody formation. ALPS has been attributed to defective programmed cell death of lymphocytes, most often arising as a result of mutations in the gene encoding the lymphocyte apoptosis receptor Fas/APO-l/CD95. We identified a novel mutation in the intracellular apoptosis signaling domain of Fas in 11 members of a family, individual members of which have been monitored for up to 25 years, with 1 or more features of ALPS. This study of a large number of family members carrying the same Fas defect demonstrates that ALPS is inherited in an autosomal dominant fashion but with a high degree of variability in clinical expression. Although 1 affected individual died of postsplenectomy sepsis and 1 has been treated for lymphoma, the Fas mutation in this family has been compatible with a healthy adulthood, as clinical features of ALPS have receded with increasing age.

Hepatocellular carcinoma in children associated with Gardner syndrome or familial adenomatous polyposis.

PURPOSE: Gardner syndrome, a variant of familial adenomatous polyposis, is characterized by colonic polyps that undergo malignant change and benign and malignant extracolonic lesions. Tumors frequently associated with Gardner syndrome include carcinoma of the ampulla of Vater, papillary carcinoma of the thyroid, and, in children, hepatoblastoma. The childhood malignancies often precede the appearance of other manifestations by several years. PATIENTS AND METHODS: Two patients are described. Gardner syndrome was diagnosed in a 15-year-old girl with fibrolamellar hepatocellular carcinoma after desmoid tumors and colonic polyposis developed. Classic hepatocellular carcinoma was also diagnosed in a 9 1/2-year-old boy with familial adenomatous polyposis. RESULTS: In patient 1, the diagnosis of fibrolamellar hepatocellular carcinoma preceded the diagnosis of Gardner syndrome by almost 2 years. The diagnosis was confirmed by identifying a germline mutation of the adenomatous polyposis coli (APC) gene. This is the first patient reported with fibrolamellar hepatocellular carcinoma associated with Gardner syndrome. Patient 2 had a strong family history of familial adenomatous polyposis but no manifestations of Gardner syndrome. He was not tested for the APC mutation. The current literature and previously reported cases of hepatocellular carcinoma in patients with Gardner syndrome or familial adenomatous polyposis are reviewed. CONCLUSIONS: Because hepatocellular carcinoma is uncommon in the pediatric and adolescent population, it is important to consider the possibility of Gardner syndrome or familial adenomatous polyposis in these patients.

Periductal mastitis. Masquerading as carcinoma.

Periductal mastitis (mammary duct ectasia) is a little appreciated, often unrecognized entity that may present to the dermatologist. We present our experience with this disease and hope to familiarize the reader with a condition not well known to most dermatologists. Periductal mastitis is a benign mammary duct disease that begins with periductal inflammation and progresses to ductal dilatation with minimal inflammation (ductal ectasia). The clinical and radiographic appearance of this disease can be indistinguishable from carcinoma of the breast.

Primary amoebic meningoencephalitis after swimming in the Rio Grande.

We report a case of fatal primary amoebic meningoencephalitis (PAM) with Naegleria fowleri in a 13-year-old male, and review the clinical course and diagnostic autopsy findings. The boy developed the infection after swimming with relatives in the Rio Grande and in a holding tank containing water pumped from the river. The clinical and neuropathologic features of PAM are presented. The microscopic features of motile unicellular organisms with pathognomonic broad, lobate pseudopodia are diagnostic and, if recognized before death, allow for timely treatment. A public health investigation into this case implicated river water from the Rio Grande polluted with sewage as the infection source. Exposure to polluted river water from some areas of the Rio Grande may represent a risk factor for infection with Naegleria fowerli, because the high levels of coliform bacteria found in sewage and the warm, sluggish water of the river are favorable growth conditions for the amoebae. Because the Rio Grande is an international border, this case illustrates the importance of international cooperation in pollution control in the prevention of a potentially fatal infectious disease.

Hernia uterus inguinale associated with unicornuate uterus.

Hernia uterus inguinale, a condition in which endometrium and myometrium are found in an ectopic location in the inguinal canal, is a rare congenital abnormality in women. A woman with a normal number of chromosomes (46,XX) demonstrated the presence of a uterus, fallopian tube, and ovary in an inguinal hernia associated with a unicornuate uterus. This represents a unique abnormality in the spectrum of lateral fusion defects associated with müllerian ductal development, which normally proceeds as the right and left systems fuse and form the uterus, cervix, and four fifths of the vagina. In this patient, the left müllerian system apparently failed to fuse with the right, instead assuming a location within the patient's inguinal canal.

Clinical relevance of the substitution of different brands of sustained-release theophylline.

In order to assess whether clinically important changes in serum theophylline concentrations occur when patients switch their brand of slow-release (SR) theophylline, 10 subjects with asthma were administered the same dose of four different SR theophylline formulations for 2-week periods in a random, double-blinded, crossover manner. Analysis of the data revealed significant differences in mean peak-to-trough fluctuations of serum theophylline concentrations between the formulations of SR theophylline, which varied from 60% to 106% of trough concentration (p less than 0.0001, analysis of variance). On at least one occasion in every subject, switching between brands of SR theophylline was responsible for raising the serum theophylline concentrations outside the accepted therapeutic range, and this was associated with symptoms of toxicity in five of the subjects. Worsening pulmonary functions were observed in two of the subjects whose switching resulted in lowered theophylline concentrations. Many of the formulation-related changes in theophylline concentrations appeared to be idiosyncratic and could not be predicted by the overall bioavailability differences between the drugs. These results argue against the open substitution of these formulations and suggest that if patients are switched between different brands of SR theophylline, their serum theophylline concentrations need to be closely monitored.