Activation of the p53 pathway by small-molecule-induced MDM2 and MDMX dimerization

Activation of p53 tumor suppressor by antagonizing its negative regulator murine double minute (MDM)2 has been considered an attractive strategy for cancer therapy and several classes of p53-MDM2 binding inhibitors have been developed. However, these compounds do not inhibit the p53-MDMX interaction, and their effectiveness can be compromised in tumors overexpressing MDMX. Here, we identify small molecules that potently block p53 binding with both MDM2 and MDMX by inhibitor-driven homo- and/or heterodimerization of MDM2 and MDMX proteins. Structural studies revealed that the inhibitors bind into and occlude the p53 pockets of MDM2 and MDMX by inducing the formation of dimeric protein complexes kept together by a dimeric small-molecule core. This mode of action effectively stabilized p53 and activated p53 signaling in cancer cells, leading to cell cycle arrest and apoptosis. Dual MDM2/MDMX antagonists restored p53 apoptotic activity in the presence of high levels of MDMX and may offer a more effective therapeutic modality for MDMX-overexpressing cancers.     

ATPASE-ASSOCIATED ANTIGEN (M2): MARKER ANTIGEN FOR SEROLOGICAL DIAGNOSIS OF PRIMARY BILIARY CIRRHOSIS

Serum samples from 94 patients with primary biliary cirrhosis (PBC) and 17 patients with chronic cholestatic hepatitis (CCH) were tested in the fluorometric immunoassay (FIAX) against the non-organ-specific ATPase-associated antigen (M2) and against submitochondrial particles (SMP) and sonicated mitochondria from beef heart and rat liver, to evaluate the specificity and sensitivity of the M2 antigen for the diagnosis of PBC. As controls serum samples from 42 patients with other antimitochondrial antibody (AMA) specificity (against M1, M3, M5, and M6) as well as samples from 417 patients with various other hepatic and non-hepatic disorders were used. Serum samples from 91 of the 94 PBC patients (97%) and all 17 with CCH reacted with the M2 antigen. However, when SMP from rat liver and beef heart were tested in parallel in the FIAX, AMA could be detected in all PBC serum samples. None of the 42 patients with different types of AMA had reactions with the M2 antigen but all had reactions with SMP from rat-liver or beef-heart mitochondria or both. Among the other 417 patients with hepatic and non-hepatic disorders only 4 (1%), all with collagen diseases, had anti-M2 antibodies.     

Clinical and molecular genetic findings in a 6-year-old Bosnian boy with triple A syndrome

The triple A syndrome is a rare autosomal recessive disease that is characterised by the triad of adrenocorticotropin (ACTH)-resistant adrenal insufficiency, achalasia and alacrima. In most patients, neurological and dermatological abnormalities are associated features. We report on the first Bosnian patient with triple A syndrome. Endocrine investigation confirmed primary adrenal insufficiency at the age of 5.8 years. Two months lather, achalasia was diagnosed, and in the presence of alacrima, the patient satisfies the diagnostic criteria of triple A syndrome. In addition, a large number of associated neurological and dermatological features were present in this patient. Moreover, he has dysmorphic facial features, which have not been previously described in triple A syndrome. Triple A syndrome was confirmed by molecular analysis, revealing a nonsense mutation p.W84X in the AAAS gene. The parents are both heterozygous carriers of the mutation. The affected twin brother unfortunately died from hypoglycaemic shock, despite a normal cortisol rise in an ACTH stimulation test. Further, triple A syndrome patients carrying the identical homozygous p.W84X mutation have to be studied to assess a genotype–phenotype relationship for this mutation. Publication of these pictures was granted by the parents of the patient.     

Estimated one-yr glomerular filtration rate is an excellent predictor of long-term graft survival in pediatric first kidney transplants

Acute rejection episodes following pediatric renal transplantation have been progressively reduced by recent immunosuppressive regimens. Nevertheless, grafts continue to fail over time and surrogate parameters for long-term RGS are lacking. We investigated post-transplant renal function within the first yr as an independent predictor of long-term RGS in 104 pediatric first kidney transplant recipients (mean age 11.1 +/- 3.9 yr; mean follow-up 8.3 +/- 3.5 yr) transplanted between January 1989 and December 2000. GFR was assessed by use of the Schwartz formula at 30 days and six and 12 months after transplantation, respectively. Patients were further stratified at all times according to GFR: (i) GFR<45 mL/min/1.73 m(2), (ii) GFR 45-80 mL/min/1.73 m(2), and (iii) GFR>80 mL/min/1.73 m(2). Cox regression analysis including factors potentially influencing long-term RGS, e.g., age, gender, transplant yr, HLA-mismatch, underlying renal disease, clinical acute rejection, absolute GFR as well as the change in GFR within the first yr was performed. Graft failure occurred in 24 out of 104 patients (23%) 6.2 yr (mean) after transplantation corresponding to a cumulative five-yr graft survival of 87.5%. GFRs at 30 days and six and 12 months were significantly associated with long-term RGS in the univariate cox regression analysis (GFR at 30 days, p = 0.045; GFR at six months, p = 0.004; GFR at 12 months, p < 0.001). None of the other variables were significant parameters of correlation. Multivariate cox analysis revealed a GFR below 45 mL/min/1.73 m(2) at 12 months after transplantation as the only independent predictor of long-term RGS (hazard ratio 55.9, 95% CI 5.29-591, p = 0.001). GFR at 12 months post-transplant is an excellent surrogate parameter for long-term RGS in children. This parameter might be useful as a primary end-point in short-term pediatric clinical trials.