International cancer seminars: a focus on kidney cancer.

Recent years have seen important advances in our understanding of the etiology, biology and genetics of kidney cancer. To summarize important achievements and identify prominent research questions that remain, a workshop was organized by IARC and the US NCI. A series of 'difficult questions' were formulated, which should be given future priority in the areas of population, genomic and clinical research.

Endocrine and neurogenic regulation of the orphan nuclear receptors Nur77 and Nurr-1 in the adrenal glands.

nurr77 and nurr-1 are growth factor-inducible members of the steroid/thyroid hormone receptor gene superfamily. In order to gain insight into the potential roles of nur77 in the living organism, we used pharmacologic treatments to examine the expression of nur77 in the mouse adrenal gland. We found that nur77 and nurr-1 are induced in the adrenal gland upon treatment with pentylene tetrazole (Ptz; Metrazole). This induction is separable into distinct endocrine and neurogenic mechanisms. In situ hybridization analysis demonstrates that nur77 expression upon Ptz treatment in the adrenal cortex is localized primarily to the inner cortical region, the zona fasciculata-reticularis, with minimal induction in the zona glomerulosa. This induction is inhibitable by pretreatment with dexamethasone, indicating involvement of the hypothalamic-pituitary-adrenal axis in the activation of adrenal cortical expression. When mice were injected with adrenocorticotrophic hormone (ACTH), nur77 expression in the adrenal gland spanned all cortical layers including the zona glomerulosa, but medullary expression was not induced. Ptz also induces expression of both nur77 and nurr-1 in the adrenal medulla. Medullary induction is likely to have a neurogenic origin, as nur77 expression was not inhibitable by dexamethasone pretreatment and induction was seen after treatment with the cholinergic neurotransmitter nicotine. nur77 is also inducible by ACTH, forskolin, and the second messenger analog dibutyryl cyclic AMP in the ACTH-responsive adrenal cortical cell line Y-1. Significantly, Nur77 isolated from ACTH-stimulated Y-1 cells bound to its response element whereas Nur77 present in unstimulated cells did not. Moreover, Nur77 in ACTH-treated Y-1 cells was hypophosphorylated at serine 354 compared with that in untreated cells. These results, taken together with the previous observation that dephosphorylation of serine 354 affects DNA binding affinity in vitro, show for the first time that phosphorylation of Nur77 at serine 354 is under hormonal regulation, modulating its DNA binding affinity. Thus, ACTH regulates Nur77 in two ways: activation of its gene and posttranslational modification. A promoter analysis of nur77 induction in Y-1 cells indicates that the regulatory elements mediating ACTH induction differ from those required for induction in the adrenal medullary tumor cell line PC12 and in 3T3 fibroblasts.

Nur77 is differentially modified in PC12 cells upon membrane depolarization and growth factor treatment.

The rat pheochromocytoma cell line PC12 can be induced by growth factors to undergo proliferation and neuronal differentiation. These cells also have excitable membranes that can be depolarized by neurotransmitters or elevated levels of extracellular KCl. Treatment of PC12 cells with growth factors or membrane-depolarizing agents rapidly activates the expression of specific genes whose products are thought to mediate the subsequent biological responses. One such gene, nur77, is a member of the steroid and thyroid hormone receptor gene superfamily. We have identified the Nur77 protein and shown that it is synthesized rapidly and transiently in PC12 cells following stimulation, has a short half-life of 30 to 40 min, and is located in both the nucleus and the cytoplasm. Nur77 is posttranslationally modified, primarily by phosphorylation on serine residues. Phosphopeptide analysis reveals that Nur77 is modified differently upon membrane depolarization than after treatment with growth factors. We hypothesize that the activity of Nur77 is regulated by both differential gene expression and posttranslational modification and that these modes of regulation contribute to distinct downstream responses specific to membrane depolarization and growth factor treatment.

Transcriptional activation by Nur77, a growth factor-inducible member of the steroid hormone receptor superfamily.

nur77 is a growth factor-inducible immediate early gene that encodes a protein with extensive sequence homology to members of the steroid/thyroid hormone receptor superfamily. By analogy to steroid receptors, the Nur77 protein is thought to act as a ligand-dependent transcription factor that regulates the genomic response to growth factors. Using chimeric gene constructs, we show that Nur77 can indeed function as a transcription activator. Furthermore, Nur77 chimeras can activate transcription in the absence of an exogenously added ligand.

Functional domains and phosphorylation of the orphan receptor Nur77.

Nur77 represents a unique class within the steroid receptor superfamily since its synthesis is tightly regulated by extracellular signals and it is capable of potent transactivation activity in the absence of an exogenously added ligand. In this study, we sought to dissect the functional domains regulating the activities of Nur77 by deletion mapping. We demonstrate that whereas the transactivation activity of Nur77 resides in the amino-terminal domain, the carboxy-terminal domain regulates this activity. A short deletion from the carboxy terminus eliminates transactivation activity while a further deletion restores the activity. Deletion of the domain immediately carboxyl to the zinc fingers motif eliminates both DNA binding activity and nuclear localization, thus abolishing transactivation. Nur77 is posttranslationally modified predominantly by phosphorylation, which occurs primarily at the N-terminal domain. The growth-related kinase pp90rsk, but neither the pp44mapk nor the pp70s6k, can phosphorylate recombinant Nur77 in vitro. Furthermore, we have identified a site within the region required for sequence-specific DNA binding, Ser-354, that is phosphorylated by pp90rsk in vitro; this site is also phosphorylated in vivo. The possibility that phosphorylation might affect DNA binding is discussed.

Dietary calcium, calcium supplementation, and blood pressure in African American adolescents.

BACKGROUND: Intake of calcium from the diet is inversely associated with blood pressure in observational studies and animal models but randomized trials in humans have found only small effects of calcium supplementation on blood pressure. A blood pressure-lowering effect of calcium supplementation may thus be restricted to persons with a low intake of calcium from the diet and specific genetic or other characteristics. OBJECTIVE: A randomized trial was conducted to assess the effect of calcium supplementation on blood pressure in African American adolescents. Rapid growth during adolescence may increase calcium requirements, and avoidance of milk and milk products by some African Americans can result in low intake of calcium. DESIGN: One hundred sixteen adolescents (65 girls, 51 boys; mean age: 15.8 y) were given calcium (1.5 g/d) or placebo for 8 wk in a randomized, double-blind, crossover design. Blood pressure was measured after 2, 4, and 8 wk. Dietary calcium was determined with a validated food-frequency questionnaire. RESULTS: The net effect (+/-SE) of calcium supplementation on diastolic blood pressure was a reduction of 1.9 +/- 1.1 mm Hg (P = 0.04, one-tailed t test). Blood pressure reduction was greater in adolescents with lower intake of calcium from the diet (P = 0.003, one-tailed t test for interaction): -4.9 +/- 1.6, -2.3 +/- 1.6, and 1.4 +/- 1.8 mm Hg for change in the lower (0.024-0.067 g Ca/MJ), middle (0.069-0.091 g Ca/MJ), and upper (0.093-0.217 g Ca/MJ) tertiles, respectively. No main effect on systolic blood pressure was detected. CONCLUSION: These findings suggest that calcium supplementation may lower diastolic blood pressure in African American adolescents with low dietary intakes of calcium.

The effects of calcium supplementation on ambulatory blood pressure in African-American adolescents.

This longitudinal trial investigated the effects of calcium supplementation on the mean 24-hour blood pressure in African-American adolescents. Subjects were self-identified African-American adolescents from a high school in a suburb of Los Angeles, California. The subjects were randomly placed in a placebo or treatment group (placebo versus 1.5 g of calcium/day x 4 weeks). Follow-up mean 24-hour ambulatory blood pressure (ABP) for both the treatment and control groups was lower than the baseline mean 24-hour ABP. In the treatment group, there was a decrease of 2.2 mm Hg in the mean systolic blood pressure and 0.7 mm Hg in the diastolic blood pressure. Relative to the placebo group, the net change in ABP was -1.7 mm Hg for systolic blood pressure and -0.5 mm Hg for the diastolic blood pressure. There was no statistically significant effect of calcium supplementation on the 24-hour mean ABP. The net effect of supplementation on ABP during waking and sleeping hours also was not significant.

Isolation of silver- and antibiotic-resistant Enterobacter cloacae from teeth.

Antibiotic-resistant bacteria pose a serious threat to human health; hence the mechanisms that lead to their selection need to be investigated. One possible mechanism is that the silver and mercury in amalgam dental restorations may select for bacteria that contain heavy metal and antibiotic-resistance determinants, leading to the spread of these resistances, particularly if they are contained on the same mobile genetic element. The incidence of silver-resistant bacteria on teeth is investigated in this work. Two silver-resistant Enterobacter cloacae isolates were isolated from infected teeth containing dental restorations. Both isolates were also resistant to ampicillin, erythromycin, and clindamycin. The silE gene, which is encoded on the silver resistance operon, has been sequenced from both isolates. Results suggest that the silver resistance operon is encoded on plasmid DNA.

Neonatal jaundice, animal-based injuries, and immunizations.

The authors describe current investigation in three areas of pediatrics commonly faced by the office practitioner. Despite the fact that changes in medical practice and in patient demographics have resulted in the reemergence of severe hyperbilirubinemia and bilirubin encephalopathy, clinical assessment and evaluation of discharge bilirubin levels may help predict those infants at greatest risk. Progress in the use of inhibitors of bilirubin production may eventually decrease the need for phototherapy. Although dog-associated injuries continue to affect children disproportionately, additional attention to anticipatory guidance may prove beneficial. The practice of routine immunization has reshaped our view of pediatric illness. The development of pneumococcal, meningococcal, and rotaviral vaccines will alter significantly the prevalence of common pediatric infectious disease. However, with the advent of additional vaccines, attention to pain control will take on increasing urgency.

Neonatal jaundice, animal-based injuries, and immunizations.

This review presents in a clinically relevant context the past year's investigations in three areas of pediatrics that commonly face the office-based pediatric provider. Although transcutaneous quantification of jaundice may help discern which patients warrant further evaluation, thereby saving patients pain and expense, this technology has not yet significantly changed clinical management of the hyperbilirubinemic infant. A brief overview of animal bites demonstrates that although most are innocuous, proper treatment of these potentially serious injuries is critical in preventing further complications. The number of immunizations given in the first 2 years of life has increased, and although new combination vaccines may eventually simplify the schedule, persistent vigilance is more important than ever to avoid delays in vaccine administration.

Gastric emptying: a study to compare the effects of intrathecal morphine and i.m. papaveretum analgesia.

Gastric emptying was studied in two groups of 10 patients who underwent elective cholecystectomy. The groups were comparable for age, weight and duration of operation. Gastric emptying was measured with a radioisotopic technique using Tc99m-DTPA (diethylene triamine pentaacetic acid) before, and 24 h after, surgery. Analgesia was provided by intrathecal morphine 0.8 mg alone (group A) or by i.m. papaveretum 10 mg, administered as required, plus one additional dose 1 h before the postoperative measurement (group B). Control gastric emptying rates were not significantly different in the two groups (mean +/- SD: A = 76.6 +/- 23.0 ml; B = 81.8 +/- 16.3 ml in 30 min). After surgery, gastric emptying was significantly greater in group A (42.9 +/- 35.6 ml) than in group B (11.0 +/- 27.9 ml) (P less than 0.05).

Upper respiratory tract carcinoma with chromosomal translocation 15;19: evidence for a distinct disease entity of young patients with a rapidly fatal course.

BACKGROUND: Carcinoma of the upper respiratory tract is rare in childhood, and cytogenetic aberrations have not been characterized in this population. The chromosomal translocation 15;19 has been reported four times previously. All patients were young and had tumors arising in the thorax. The three reports that provide clinical follow-up all describe superior vena cava syndrome and death soon after presentation. All tumors were diagnosed as carcinoma (three undifferentiated, one mucoepidermoid), and the authors suggested thymus, lung, or germ cell origin. METHODS: The authors investigated the clinical and pathologic findings in two patients with poorly differentiated carcinoma showing evidence of t(15;19). This included a 13-year-old girl with a rapidly growing epiglottic mass, leading to superior vena cava syndrome and death and a 12-year-old girl with an aggressive nasopharyngeal mass showing intracranial extension. RESULTS: The laryngeal tumor was poorly differentiated, with vesicular nuclei, prominent nucleoli, extensive necrosis, and a lymphoplasmacytic infiltrate; cells were positive for cytokeratin and negative for lymphoma, melanoma, germ cell, and endocrine markers. Electron microscopy showed rare intermediate junctions and basal lamina. The nasopharyngeal tumor was poorly differentiated with areas of obvious squamous differentiation observed histologically, immunophenotypically, and ultrastructurally. Cytogenetic and fluorescent in situ hybridization studies were consistent with t(15;19)(q13;p13.1) in both cases. Both children received chemo- and radiotherapy. The first child died of disease after 36 weeks; autopsy revealed tumor in the larynx with spread to the skin/subcutis (neck and thorax) and lymph nodes (cervical, subcarinal, and pulmonary hilar). The second child developed widespread bony metastases and died of disease after 13 weeks. CONCLUSIONS: In conjunction with previous reports, the authors' findings show that t(15;19) is part of a distinct clinicopathologic entity characterized by young age, midline carcinoma of the neck or upper thorax, and a rapidly fatal course. Female gender and superior vena cava syndrome are common. The histogenesis of these distinctive tumors is unknown. The authors' findings suggest origin in the upper airway, perhaps from submucosal glands.