Genetics of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the human cancers clearly linked to viral infections. Although the major viral and environmental risk factors for HCC development have been unravelled, the oncogenic pathways leading to malignant transformation of liver cells have long remained obscure. Recent outcomes have been provided by extensive allelotype studies which resulted in a comprehensive overview of the main genetic abnormalities in HCC, including DNA copy gains and losses. The differential involvement of the p53 tumor-suppressor gene in tumors associated with various risk factors has been largely clarified. Evidence for a crucial role of the reactivation of the Wnt/beta-catenin pathway, through mutations in the beta-catenin and axin genes in 30-40% of liver tumors, represents a major breakthrough. It has also been shown that the Rb pathway is frequently disrupted by methylation-dependent silencing of the p16INK4A gene and stimulation of Rb degradation by a proteosomal subunit. Presently, the identification of candidate oncogenes and tumor suppressors in the most frequently altered chromosomal regions is a major challenge. Great insights will come from integrating the signals from different pathways operating at preneoplastic and neoplastic stages. This search might, in time, permit an accurate evaluation of the major targets for therapeutic treatments.     

Late results of mitral valve replacement with the Bj?rk-Shiley prosthesis in children under 16 years of age

The late results of isolated mitral valve replacement were evaluated in 37 children under 16 years of age receiving a Bj?rk-Shiley prosthesis for the treatment of rheumatic mitral lesions. Three patients died, one during the operation and the others 2 months postoperatively. Of the latter two, one had a cerebral hemorrhage and the second had septicemia. The survivors were followed up for a mean of 4.7 years (range 2.8 to 8.9 years). After the operation, all patients were placed on a strict anticoagulant regimen with acenocoumarol. The actuarial survival rate was 92% at the end of the follow-up period. Before valve replacement two patients were in New York Heart Association Class I, 15 in Class II, 18 in Class III, and two in Class IV. After treatment 33 were in Class I and one in Class II. No instances of thromboembolism or infective endocarditis were observed in the survivors. Twenty-one patients underwent cardiac catheterization 2 to 7 years after the operation for evaluation of surgical results. The mean pulmonary artery systolic pressure decreased significantly after operation (p = 0.001), and the mean pulmonary artery wedge pressure decreased to normal values (p = 0.001). A mild mean diastolic gradient across the mitral valve at rest was found after the operation (4.9 +/- 2.4 mm Hg). During isometric exercise this gradient increased to 6.5 +/- 4.6 mm Hg. In two patients a discrete paravalvular leak was demonstrated by cineangiography, but the pulmonary wedge pressure was normal in both. The overall results with the Bj?rk-Shiley prosthesis are encouraging in patients in whom reconstructive operations cannot be performed.     

The adult patient with Ebstein anomaly. Outcome in 72 unoperated patients

Knowledge of the long-term outcome in unoperated adult patients with Ebstein anomaly is limited, and the therapeutic approach is still controversial. We studied unoperated adult patients with Ebstein anomaly to define the patterns of presentation, anatomic characteristics, outcome, and predictive factors for survival. Seventy-two unoperated survivors of Ebstein anomaly aged over 25 years attended from 1972 to 1997 were reviewed and followed-up from 1.6 to 22.0 years. Patients were classified in 3 groups of severity according to the echocardiographic appearance of the septal leaflet attachment of tricuspid valve. The mean age at diagnosis was 23.9 +/- 10.4 years, and the most common clinical presentation was an arrhythmic event (51.4%). There were 30 (42%) deaths, including 6 from arrhythmia, 12 related to heart failure, 7 sudden, 2 unrelated, and 3 unascertained. According to Cox regression analysis, predictors of cardiac-related death included age at diagnosis (hazard ratio 0.89 for each year of age, 95% confidence intervals CI[ 0.84-0.94), male sex (3.93, 95% CI, 1.50-10.29), degree of echocardiographic severity (3.34, 95% CI, 1.78-6.24), and cardiothoracic ratio > or = 0.65 (3.57, 95% CI, 1.15-11.03). During follow-up, morbidity was mainly related to arrhythmia and refractory late hemodynamic deterioration. The magnitude of tricuspid regurgitation, cyanosis, and the New York Heart Association (NYHA) functional class at time zero were significant risk factors according to the univariate analysis, but not after multivariable confrontation. The results of this study suggest that pattern of presentation, clinical course, and prognosis of unoperated adult patients with Ebstein anomaly are influenced by several factors. Although the initial symptoms are usually mild and commonly related to supraventricular arrhythmias, these are not associated with the long-term outcome. The severity of the morbid anatomy was the main determinant of survival only in extreme cases, but not in those with mild or moderate deformations, which are more common in adults. Other independent risk factors such as cardiothoracic ratio, sex, age at diagnosis, and the echocardiographic evaluation may help to determine the therapeutic approach. Adult patients with Ebstein anomaly should not be considered as a simple low-risk group.     

Lymphocyte populations in Parkinson's disease and in rat models of parkinsonism

To assess the involvement of the immune system in Parkinson's disease we studied the phenotype of circulating lymphocytes in 30 untreated and 34 treated patients. We found a numeric decrease in helper T cells (higher in CD4(+)CD45RA(+) than in CD4(+)CD29(+)) and B cells, and a rise in activated, CD4(+)CD25(+) lymphocytes that was correlated with lymphocyte depletion. All these alterations were independent of levodopa treatment. In addition, we performed striatal dopamine depletion in rats with either MPP(+) or 6-OHDA, showing that MPP(+) but not 6-OHDA can increase CD4(+)CD25(+) lymphocytes. Thus, mechanisms other than dopamine deficit may explain the immune activation in Parkinson's disease.     

ARID1A‐deficient cells require HDAC6 for progression of endometrial carcinoma

AT‐rich interactive domain‐containing protein 1A (ARID1A) loss‐of‐function mutation accompanied by a loss of ARID1A protein expression is frequently observed in endometrial carcinomas. However, the molecular mechanisms linking these genetic changes to the altered pathways regulating tumour initiation, maintenance and/or progression remain poorly understood. Thus, the main aim of this study was to analyse the role of ARID1A loss of function in endometrial tumorigenesis. Here, using different endometrial in vitro and in vivo models, such as tumoral cell lines, 3D primary cultures and metastatic or genetically modified mouse models, we show that altered expression of ARID1A is not enough to initiate endometrial tumorigenesis. However, in an established endometrial cancer context, ARID1A loss of function accelerates tumoral progression and metastasis through the disruption of the G2/M cell cycle checkpoint and ATM/ATR‐mediated DNA damage checkpoints, increases epithelial cell proliferation rates and induces epithelial mesenchymal transition through the activation of histone deacetylase 6 (HDAC6). Next, we demonstrated that the inhibition of HDAC6 function, using the HDAC6‐specific inhibitor ACY1215 or by transfection with HDAC6 short hairpin RNA (shRNA), can reverse the migratory and invasive phenotype of ARID1A‐knockdown cells. Further, we also show that inhibition of HDAC6 activity causes an apoptotic vulnerability to etoposide treatments in ARID1A‐deficient cells. In summary, the findings exposed in this work indicate that the inhibition of HDAC6 activity is a potential therapeutic strategy for patients suffering from ARID1A‐mutant endometrial cancer diagnosed in advanced stages.     

The hepatitis B virus X protein abrogates Bcl-2-mediated protection against Fas apoptosis in the liver

The role of the hepatitis B virus protein HBx in liver cell proliferation and apoptosis remains controversial. Using a transgenic mouse model, we have recently shown that HBx stimulates the apoptotic turnover of hepatocytes, independently of p53. In this paper, we tested whether the proapoptotic function of HBx can interfere with Bcl-2 during hepatic apoptosis in vivo. HBx transgenic mice were crossed with PK-hBcl-2 mice that are protected against Fas killing by constitutive overexpression of Bcl-2 in hepatocytes. In a lethal challenge with Fas antibodies, HBx expressed at low levels restored sensitivity to Fas-mediated apoptosis and fulminant hepatic failure in mice overexpressing Bcl-2. Furthermore, cytochrome c release from mitochondria and caspase 3 activation were restored to normal levels in HBx/Bcl-2 mice during transduction of the Fas signal. Thus, the proapoptotic activity of HBx overcomes or bypasses the inhibitory effect of Bcl-2 against Fas cytotoxicity. This effect was not apparently mediated through downregulation of the PK-hBcl-2 transgene or via delocalization of the Bcl-2 protein, and a direct interaction of HBx with Bcl-2, Bcl-X(L) or Bax could not be evidenced in yeast two-hybrid assays. We further show that apoptosis induced by ectopic expression of HBx is associated with mitochondrial membrane alterations and caspase 3 activation. Our data indicate that the dominant function of HBx upon Bcl-2-regulated control of apoptosis might play an important role in the pathogenesis of chronic hepatitis B.     

An anti-ICAM-2 (CD102) monoclonal antibody induces immune-mediated regressions of transplanted ICAM-2-negative colon carcinomas

Monoclonal antibodies (mAbs) can mediate antitumor effects by indirect mechanisms involving antiangiogenesis and up-regulation of the cellular immune response rather than by direct tumor cell destruction. From mAbs raised by immunization of rats with transformed murine endothelial cells, a mAb (EOL4G8) was selected for its ability to eradicate a fraction of established colon carcinomas that did not express the EOL4G8-recognized antigen. The antigen was found to be ICAM-2 (CD102). Antitumor effects of EOL4G8, which required a functional T-cell compartment, were abrogated by depletion of CD8(+) cells and correlated with antitumor CTL activity, whereas only a mild inhibition of angiogenesis was observed. Interestingly, we found that EOL4G8 acting on endothelial ICAM-2 markedly enhances leukotactic factor activity-1-independent adhesion of immature dendritic cells to endothelium-an effect that is at least in part mediated by DC-SIGN (CD209).