Functional analysis and consequences of Mdm2 E3 ligase inhibition in human tumor cells.

Mdm2 is the major negative regulator of p53 tumor-suppressor activity. This oncoprotein is overexpressed in many human tumors that retain the wild-type p53 allele. As such, targeted inhibition of Mdm2 is being considered as a therapeutic anticancer strategy. The N-terminal hydrophobic pocket of Mdm2 binds to p53 and thereby inhibits the transcription of p53 target genes. Additionally, the C-terminus of Mdm2 contains a RING domain with intrinsic ubiquitin E3 ligase activity. By recruiting E2 ubiquitin-conjugating enzyme(s), Mdm2 acts as a molecular scaffold to facilitate p53 ubiquitination and proteasome-dependent degradation. Mdmx (Mdm4), an Mdm2 homolog, also has a RING domain and hetero-oligomerizes with Mdm2 to stimulate its E3 ligase activity. Recent studies have shown that C-terminal residues adjacent to the RING domain of both Mdm2 and Mdmx contribute to Mdm2 E3 ligase activity. However, the molecular mechanisms mediating this process remain unclear, and the biological consequences of inhibiting Mdm2/Mdmx co-operation or blocking Mdm2 ligase function are relatively unexplored. This study presents biochemical and cell biological data that further elucidate the mechanisms by which Mdm2 and Mdmx co-operate to regulate p53 level and activity. We use chemical and genetic approaches to demonstrate that functional inhibition of Mdm2 ubiquitin ligase activity is insufficient for p53 activation. This unexpected result suggests that concomitant treatment with Mdm2/Mdmx antagonists may be needed to achieve therapeutic benefit.

[A heap of trouble. Resistant hypertension and aneurysm of the renal artery]. / Un sacco di guai.

A 47-year-old female, was referred to our renal and vascular ultrasound unit by the cardiologists, because of a long history of uncontrolled hypertension resistant to multiple antihypertensive drug treatment. The question was if the patient had a secondary form of hypertension, i.e. a renal artery stenosis. An accurate evaluation by echo-color Doppler ultrasound displayed an aneurysm located at the bifurcation of the right renal artery. The surgical correction of the aneurysm normalized the arterial pressure and avoided a rupture, which is always a dramatic event.

[Changes is Th1/Th2 balance in hemodialysis patients: effect of different membranes]. / Alterazione del bilancio Th1/Th2 nei pazienti in trattamento emodialitico: effetto di differenti membrane.

BACKGROUND: Hemodialysis (HD) patients present an immunodeficiency that is mainly related to the defect of cell-mediated immunity. We have previously shown the polarisation of T-helper cells toward the phenotype in HD treatment with cuprophan membrane. In the present study, we have examined the effect of a Vitamin E-coated dialyser (Excebrane, VE) on the activity of the two Th subsets. METHODS: We studied 8 healthy controls and 10 patients on RDT for at least 6 months with cellulose membrane (AC), then switched to HD-VE. Blood was collected from HD patients while on treatment with AC, and after 1 year of treatment with VE. CD4+ cells were isolated from peripheral blood mononuclear cells (PBMC) by negative selection, treating PBMC with a cocktail of anti-CD8, -CD16, -CD19, -CD36 and -CD56 antibodies labelled with magnetic beads, and passing them through a magnetic field. The collected Th cells were cultured for 48 h with and without phytohemagglutinin (PHA). IFNgamma and IL-4 were measured in the supernatant using the ELISA assay. RESULTS: The constitutive release of IL-4 by CD4+ cells was abated significantly by treatment with VE. IFNgamma released by mitogen-stimulated CD4+ recovered with VE. CONCLUSIONS: This study demonstrates that treatment with vitamin E-coated dialyser improves the defect of PBMC function associated with cellulose membrane dialyser consisting of altered spontaneous and mitogen-stimulated cytokine release. The effects of vitamin E-coated filter, in particular the recovery of reactive IFNgamma production by Th1 cells and the restriction of spontaneous IL-4 release by Th2 cells may have clinical importance.

[Diverticulosis of the small intestine. A case report]. / Diverticolosi dell'intestino tenue. Descrizione di un caso.

Non-Meckel's diverticula of the small bowel are a rare occurrence. They may be divided into true diverticula and pseudodiverticula. In general they are diagnosed intraoperatively following the onset of secondary complications. The authors describe a case which was brought to their attention.

[A case of splanchnic rhabdomyosarcoma]. / Descrizione di un caso di rabdomiosarcoma a localizzazione splancnica.

Rhabdomyosarcoma is a typical tumor of the skeletal musculature. A case personally observed, with possible splenic origin is presented.