Mdm2 and Mdm4 loss regulates distinct p53 activities.

Mutational inactivation of p53 is a hallmark of most human tumors. Loss of p53 function also occurs by overexpression of negative regulators such as MDM2 and MDM4. Deletion of Mdm2 or Mdm4 in mice results in p53-dependent embryo lethality due to constitutive p53 activity. However, Mdm2(-/-) and Mdm4(-/-) embryos display divergent phenotypes, suggesting that Mdm2 and Mdm4 exert distinct control over p53. To explore the interaction between Mdm2 and Mdm4 in p53 regulation, we first generated mice and cells that are triple null for p53, Mdm2, and Mdm4. These mice had identical survival curves and tumor spectrum as p53(-/-) mice, substantiating the principal role of Mdm2 and Mdm4 as negative p53 regulators. We next generated mouse embryo fibroblasts null for p53 with deletions of Mdm2, Mdm4, or both; introduced a retrovirus expressing a temperature-sensitive p53 mutant, p53A135V; and examined p53 stability and activity. In this system, p53 activated distinct target genes, leading to apoptosis in cells lacking Mdm2 and a cell cycle arrest in cells lacking Mdm4. Cells lacking both Mdm2 and Mdm4 had a stable p53 that initiated apoptosis similar to Mdm2-null cells. Additionally, stabilization of p53 in cells lacking Mdm4 with the Mdm2 antagonist nutlin-3 was sufficient to induce a cell death response. These data further differentiate the roles of Mdm2 and Mdm4 in the regulation of p53 activities.

Síndrome de kawasaki: presentación de un caso poco común / Kawasaki syndrome: presentation of an uncommon case

La enfermedad de Kawasaki es un proceso vasculítico multisistémico cuya etiología es poco conocida. La presentación clínica es florida y su evolución está condicionada al inicio temprano de la terapia específica con gammaglobulinas, de allí la importancia de un diagnóstico precoz. Habitualmente estos casos cursan con dilatación del lecho arterial coronario siendo excepcional la aparición de alteraciones a nivel de arterias de mayor calibre, menos común aneurismas a nivel cerebral, que confiere un peor pronóstico para estos pacientes. Presentamos el caso de lactante de 3 meses de edad con aneurisma de ambas arterias coronarias, arteria subclavia izquierda, cerebral media derecha y ambas Iliacas, y obstrucción de las mismas.

Kawasaki disease, a multisystem vasculitis of unknown etiology can present in various ways. It is crucial to make an early diagnosis, and consequently give gamma globulin in order to abort its insidious evolution and not infrequently fatal outcome. Aneurysms and obstruction of the coronary arteries are the most characteristic presentations. Other large vessels may be involved, with the cerebral circulation being affected least often but having the worst prognosis. We present a clinical case of a 3 month old breast fed infant with aneurysms and obstructions in both coronary arteries, the left subclavian, right middle cerebral, and both iliac arteries.

High levels of the p53 inhibitor MDM4 in head and neck squamous carcinomas.

The p53 tumor suppressor is mutated in most human tumors. MDM2, a well-known inhibitor of p53, is overexpressed in a large number of tumors, suggesting that increased levels of MDM2 also contribute to tumorigenesis. A novel p53 inhibitor, MDM4, was more recently identified. The role of MDM4 in cancer development is not well understood. We set out to examine the levels of MDM4 by immunohistochemistry in head and neck squamous carcinomas (HNSC) to ask whether high MDM4 levels could contribute to its development and progression. In addition, MDM2 and p53 levels were examined to identify overlapping expression patterns. MDM4 is present at high levels in 50% of HNSC. In addition, overexpression of MDM2 was detected in 80% of tumors, many of which were also positive for MDM4. A subset of tumors displayed high levels of all 3 proteins. Sequencing of the p53 gene revealed that tumors with positive immunoreactivity for MDM2 or MDM4, some of which also had high levels of p53, did not carry mutations in this gene. Thus, the detection of p53 by immunohistochemistry was not synonymous with the presence of p53 mutations. Expression of both MDM2 and MDM4 in tumors without p53 mutations strongly suggests that MDM2 and MDM4 inhibit the activity of this tumor suppressor in HNSC.

HDM4 (HDMX) is widely expressed in adult pre-B acute lymphoblastic leukemia and is a potential therapeutic target.

Human homolog of murine double minute 2 (HDM2) and HDM4 (or HDMX) are negative regulators of p53. HDM4 has not been assessed in precursor B (pre-B) lymphoblastic leukemia (ALL). We examined bone marrow samples obtained at time of diagnosis from 55 adults with pre-B ALL. A tissue microarray composed of 2 cores per specimen was constructed and immunohistochemical techniques were used to assess HDM4, HDM2, p53, and p21. HDM4 was expressed in 39 of 49 (80%) cases. HDM2 was expressed in 14 of 54 (26%). All HDM2-positive cases were also positive for HDM4 (P<0.05). We confirmed expression of HDM4 and HDM4 variants by Western blotting and sequencing of reverse transcription-polymerase chain reaction products in a subset of ALL tumors. Results were correlated with the presence of the Philadelphia chromosome (Ph). p53 (P<0.05) and p21 (P<0.001) were expressed significantly more often in Ph+ pre-B ALL. HDM4 and HDM2 showed no correlation with Ph status. HDM4 expression in most cases of adult pre-B ALL suggests that HDM4 is a potential therapeutic target.

p21 delays tumor onset by preservation of chromosomal stability.

The p53 protein suppresses tumorigenesis by initiating cellular functions such as cell cycle arrest and apoptosis in response to DNA damage. A p53 mutant, p53R172P, which is deficient for apoptosis but retains a partial cell cycle arrest function, delays tumor onset in mice. Remarkably, lymphomas arising in Trp53(515C/515C) mice (encoding p53R172P) retain stable genomes. Given the dominant role of p21 in p53 cell cycle control, we crossed Trp53(515C/515C) mice onto a p21-null background to determine whether p21 was required for maintaining chromosomal stability and delaying tumor onset. Loss of p21 completely abolished the cell cycle arrest function of p53R172P and accelerated tumor onset in Trp53(515C/515C) mice. Cytogenetic examination of Trp53(515C/515C) p21(-/-) sarcomas and lymphomas revealed aneuploidy and chromosomal aberrations that were absent in Trp53(515C/515C) malignancies. Thus, p21 coupled p53-dependent checkpoint control and preservation of chromosomal stability, and cooperated with apoptosis in suppressing tumor onset in mice.

Generation and characterization of a constitutively active Stat3 protein.

Stats are latent transcription factors involved in normal cellular signaling in response to cytokine or growth factor stimulation. Constitutive activation of Stats (primarily Stat3 and Stat5) has been implicated in growth dysregulation and oncogenesis. Furthermore, increased activation of Stats has been observed in several human tumors and tumor-derived cell lines. To assess the contribution of aberrant Stat activation in oncogenesis, we have created a chimeric molecule between Stat3beta and a portion of the Herpes simplex virus VP16 activation domain. The resulting protein, Stat3beta-VAD (VP16 activation domain), is tyrosine phosphorylated on Y705 and can bind DNA in the absence of upstream activation by c-Src or epidermal growth factor (EGF). Unlike Stat3alpha and Stat3beta, Stat3beta-VAD robustly activates transcription of several reporter genes without cytokine or growth factor stimulation. In addition, we show marked upregulation of the endogenous c-myc and c-fos genes upon inducible expression of Stat3beta-VAD in COS-7 cells. Our protein displays the constitutive transcriptional activation of Stat3alpha seen in human tumors and will be a valuable tool in screens for Stat3-regulated genes. In response to the established Stat3 involvement in human cancers, Stat3beta-VAD will also facilitate assessing the contribution of other cancer signaling cascades in the context of aberrant Stat3alpha activity in cancer development and progression.

Sympathetic nervous system activation, antivenin administration and cardiovascular manifestations of scorpion envenomation.

We performed two-dimensional echocardiograms and determined plasma norepinephrine levels on admission and at 24h after hospitalization, in 16 children with scorpion envenomation. All patients came from areas where scorpions have been identified as Tityus zulianus and received antivenin at the site of the accident or upon admission. Based on the presence or absence of cardiovascular manifestations, patients were divided into two groups. GROUP A: 10 patients had cardiovascular manifestations of pulmonary edema. Four patients had mild pulmonary edema (Left ventricular ejection fraction: 0.43+/-0.19) and six had moderate to severe pulmonary edema (Ejection fraction: 0.31+/-0.09. p=NS, M+/-SD). Plasma norepinephrine was elevated on admission (1279+/-824) and decreased at 24h in seven of eight patients (474+/-140 pg/ml, p<0.03). GROUP B: Six patients had no cardiovascular manifestations. These patients had normal chest X-rays and normal echocardiograms. Plasma norepinephrine was not elevated (188+/-180 pg/ml). Time interval from the accident to antivenin administration was significantly longer in Group A compared to Group B (4.5+/-3.3 vs 1.2+/-0.4h, p<0.03) and correlated directly with the absolute change in plasma norepinephrine (r=0.76, p<001). Consequently, we strongly recommend very early administration of antivenin in the medical management of scorpion envenomation by T. zulianus.

Anastomosis interorejuelas: nueva técnica para la confección de comunicación interauricular de urgencia / Interorejuelas anastomosis: technical new the confection of communication interauricular of urgency

Se describe una nueva técnica quirúrgica para la realización de comunicación interauricular paliativa, sencilla en su aplicación, mucho menos traumática para el paciente y de eficacia comprobada. Fue aplicada en cuatro niños portadores de atresia tricuspídea con buenos resultados. Considereramos que deberá constituirse en el procedmiento de elección en aquellos pacientes en quienes sea preciso elaborar una comunicación interauricular cuando la atrioseptostomía con balón fracase o no esté indicada

Anatomia angiográfica en 13 pacientes con corazón univentricular / Angiographic anatomy in 13 patients with univentricular heart

Se informan las características angiográficas de 13 pacientes portadores de ventrículo único (VU) del Centro Cardiovascular de la Universidad de los Andes con edades comprendidas entre 1 mes y 18 años (media 2.7) estudiados entre el 01-04-87 hasta el 31-03-92. RESULTADOS: El VU fue más frecuente en el sexo femenino, relación 1,6:1. De ellos hubo 6 (46 por ciento ) casos de VU izq; 5 (38 por ciento ) con VU der y 2 (15 por ciento ) casos con el tipo indeterminado. El situs fue inversus en 3 (23 por ciento ) pacientes, situs ambiguo en 2 (15 por ciento ) pacientes, con dextroisomerismo. MORFOLOGIA VENTRICULAR: De los 6 casos con VU izq, 4 se presentaron con cámara ventricular derecha rudimentaria, de los 5 casos con VU der, 3 presentaron bolsa trabecular (Trabeculated Pouch). RELACION VENTRICULAR ARTERIAL (VA): En VU Izq.:Concordante en 1, discordante 1, tronco común en 2, y 3 doble tracto de salida. En los VU Der: Concordante en 1, discordante en 1 y 3 con doble tracto de salida con malposición de las grandes arterias. Los del tipo indeterminado fueron doble tractos de salida (1D-TGA y 1 LTGA). CONEXIONES AV:Encontramos 4 casos con defecto total del canal atrio-ventricular (DTCAV), 3 asociados a VU Der y 1 al VU Izq. Hubo 1 caso de VU Der con obstrucción de la válvula mitral.ANOMALIASASOCIADAS: La anomalía cardíaca asociada más frecuente fue la estenosis pulmonar (valvular y/o subvascular), en 9 pacientes.CONCLUSIONES: Nuestra serie coincide parcialmentecon las características angiográficas de otras publicaciones y demuestra la utilidad de las técnicas axiales en la definición angiográfica de las anormalidades anatómicas del corazón univentricular