OmoMYC blunts promoter invasion by oncogenic MYC to inhibit gene expression characteristic of MYC-dependent tumors.

MYC genes have both essential roles during normal development and exert oncogenic functions during tumorigenesis. Expression of a dominant-negative allele of MYC, termed OmoMYC, can induce rapid tumor regression in mouse models with little toxicity for normal tissues. How OmoMYC discriminates between physiological and oncogenic functions of MYC is unclear. We have solved the crystal structure of OmoMYC and show that it forms a stable homodimer and as such recognizes DNA in the same manner as the MYC/MAX heterodimer. OmoMYC attenuates both MYC-dependent activation and repression by competing with MYC/MAX for binding to chromatin, effectively lowering MYC/MAX occupancy at its cognate binding sites. OmoMYC causes the largest decreases in promoter occupancy and changes in expression on genes that are invaded by oncogenic MYC levels. A signature of OmoMYC-regulated genes defines subgroups with high MYC levels in multiple tumor entities and identifies novel targets for the eradication of MYC-driven tumors.

Off-pump coronary artery bypass grafting does not reduce lymphocyte activation.

OBJECTIVE: In this study, we test the hypothesis that off-pump coronary bypass surgery might result in less lymphocyte activation than on-pump coronary surgery. We also study the behavior of lymphocyte activation markers during and after surgery. BACKGROUND: Coronary artery bypass surgery is known to be associated with changes of inflammatory mediators, immune function, and early phase lymphocyte activation, which could cause postoperative lymphopenia and lymphocyte unresponsiveness. METHODS: We studied lymphocyte activation response in 28 patients randomized to off-pump (n = 13) or on-pump (n = 15) coronary artery bypass surgery. Expression of CD25, CD26, CD69, and DR on T (CD3+) and B (CD19+) lymphocytes on peripheral blood was assessed through flow cytometry. RESULTS: The response of T lymphocytes and their activation markers, as well as B lymphocytes and their activation markers, was similar after on- and off-pump surgery. Overall, T lymphocytes decreased to the lowest level 9 h after surgery and tended to increase later. For B lymphocytes, there was early reduction with increase on the 1st postoperative day. There was early activation of CD69+ and late activation of CD25+ on T lymphocytes. For B lymphocytes, there was early activation of CD69+ and late activation of DR+. CONCLUSIONS: (1) Compared to on-pump cardiopulmonary bypass, off-pump surgery does not reduce lymphocyte activation. (2) Coronary bypass surgery causes the early activation of lymphocytes, as evidenced by the increased expression of lymphocyte activation markers.

[Reinfusion of shed blood after heart surgery]. / Reinfusão de sangue drenado em pós-operatório de cirurgia cardíaca.

PURPOSE: To asses effectivity of postoperative reinfusion of shed mediastinal blood in reduction of homologous transfusions at cardiac surgery and to study the possibility of side effects. METHODS: Fifteen patients submitted to cardiac surgery that had their shed mediastinal blood reinfused after surgery were compared to another group of 15 patients. The two groups were compared in relation to: volume of shed blood, number of units of blood used in postoperative period, culture of shed blood, postoperative complications, number of days of hospitalization, hematocrit at the end of hospitalization and mortality. RESULTS: The use of whole blood and packed blood cells decreased from 25 to 10 units with reinfusion of shed mediastinal blood (p < 0.01). Volume of shed blood, postoperative complications, period of hospitalization, hematocrit at the end of hospitalization and mortality were not different in both groups. Culture of shed blood, in 8 patients of control group and all patients of study group were negative. CONCLUSION: Reinfusion of shed mediastinal blood in postoperative of cardiac surgery proved to be very efficient in decreasing homologous blood transfusions. This procedure is also safe, with no additional risk to patients.

Analysis of chromatin structure in vivo.

A number of important nuclear processes including replication, recombination, repair, and transcription involve the interaction of soluble nuclear proteins with DNA assembled as chromatin. Recent progress in a number of experimental systems has focused attention on the influence chromatin structure may exert on gene regulation in eukaryotes. With the advent of new technologies for the analysis of chromatin structure in vivo, studies evaluating the influence of chromatin structure on gene transcription have become feasible for a number of systems. This article serves as an introduction to the use of restriction endonucleases to define nucleosomal organization and characterize changes in this organization that accompany transcriptional activation in vivo. The procedure includes the isolation of intact transcriptionally competent nuclei, limited digestion with specific restriction endonucleases, and purification of the DNA. This DNA serves as the substrate for a linear amplification using single primers that generate enzyme-specific DNA fragments, which are then resolved by electrophoresis. Specific examples related to our studies of the influence of chromatin structure on steroid hormone regulation of transcription from the mouse mammary tumor virus promoter are provided to illustrate this technique and several novel variations. Alternative methods for analysis of chromatin architecture using DNase I, micrococcal nuclease, permanganate, and methidiumpropyl-EDTA-iron(II) are also described. Through the use of these methodologies one is able to determine both the translational and the rotational positions for a given nucleosome as well as quantify changes at a specific nucleosome in response to regulatory and developmental signals.

Carcinoma of the extrahepatic biliary tract: surgery and radiotherapy for curative and palliative intent.

Forty-seven patients were treated for carcinoma of the extrahepatic biliary tract between 1962 and 1993: 17 by surgery alone, 20 by surgery and postoperative radiotherapy, and 10 with radiotherapy alone. Initial operations included gross total resection (17 patients), simple cholecystectomy (6 patients), subtotal resection (11 patients), biopsy (3 patients), and percutaneous decompression (10 patients). External-beam radiotherapy (30-60 Gy) was administered to 30 patients: 10 after gross total resection or simple cholecystectomy, 10 after subtotal resection or surgical biopsy, and 10 after percutaneous decompression. Overall survival was 26% at 3 years and 15% at 5 years. The 5-year survival rate was 15% for 17 patients treated by surgery alone and 14% for 30 patients treated with radiotherapy alone or following surgery. After gross total resection, median survival time was 26.1 months for 9 patients treated by surgery alone vs. 43.4 months for 8 patients who received postoperative radiotherapy. After gross total resection or cholecystectomy, 5-year survival rates were 19% for surgery alone and 35% for surgery and postoperative radiotherapy (P=.07). Median survival for 10 patients treated by radiation therapy alone after percutaneous decompression was 6.4 months. Postoperative adjuvant radiotherapy was well tolerated and may improve local-regional control after gross total resection.

End-stage heart failure: is there a role for the Batista procedure?

BACKGROUND: Medically refractory heart failure is traditionally managed with cardiac transplantation although some limited success has also been obtained in selected patients using dynamic cardiomyoplasty or mechanical assist devices. Recently, a new surgical alternative called partial left ventriculectomy (PLV) was introduced by Batista in 1995. The procedure attempts to relieve symptoms of congestive failure by reducing myocardial mass and restoring the normal mass-to-volume ratio of the left ventricle. Despite initial enthusiasm, the results of PLV are not yet known. The aim of this study was to determine survival and clinical outcomes in a group of patients submitted to PLV as a means of surgical treatment for end stage heart disease (ESHD) METHODS: From November 1994 to December 1995, 15 patients with ESHD and dilated cardiomyopathy (DCM) were operated on by the technique described by Randas Batista. We compared preoperative and postoperative assessments of NYHA Functional Class (FC), Quality of Life index (QOL), echocardiographic, ergometric, radioisotopic ventriculography and hemodynamic data at intervals of zero, one, three, six and nine, and twelve months postoperatively. Kaplan-Meier, student t-test and chi-square analysis were applied to the numerical and categoric variables. RESULTS: Survival was 80% at one month, 66% at three months, 53% at six months, 47% at nine months and 40% at one year. We also found that 6 of 7 patients (85%) with tricuspid regurgitation (TR) died compared to 4 of 8 patients (50%) without TR. This was the only risk factor indentified which influenced mortality. Post-operative echocardiographic evaluations demonstrated reduced left ventricular end-diastolic and end-systolic diameters at six months (LVESD 65.5 +/- 8.3 mm preoperatively versus 56.83 +/- 5.74 mm at six months, p=0.007 and LVEDD 73.84 +/- 8.25 mm preoperatively versus 65.33 +/- 5.72 mm at six months, p=0.009). Survivors enjoyed an improved clinical status according to both the NYHA functional class (preoperative Class IV=100% versus postoperative at six months : Class IV = 50%, Class III = 17% and Class II = 33%) and the Quality of Life index (100% were in grade 6 and 7 preoperatively versus 0% at six months). However, statistical significance was not reached in most of these data due to the small number of patients. CONCLUSIONS: Actuarial survival in this series of patients was 53% at six months and 40% at twelve months with survivors showing fewer symptoms and clinical events than preoperatively (100% hospitalized preoperatively versus no patient hospitalized at six months). Therefore, the Batista Operation improves the quality of life patients with dilated cardiomyopathy and can possibly be a new means for bridging to cardiac transplantation in severely ill patients who are not likely to survive long enough to recieve a donor heart. Additional improvements in late results will likely be seen after further experience, evolution of the surgical techniques and better patient selection.