The potential role of bcl-2 mRNA and protein exression in hepatocellular carcinomas

BACKGROUND: The bcl-2 gene regulates programmed cell death by providing a survival advantage to rapidly proliferating cells. In several malignant tumors bcl-2 presence has been associated with favorable prognosis. In the liver, bcl-2 is expressed in bile ductular cells and tumors of biliary origin. This study investigates the expression of bcl-2 mRNA and protein in hepatocellular carcinomas (HCC). MATERIALS AND METHODS: The study comprised 35 primary HCC resected from 35 patients; 21 males and 14 females, aged from 43-59 years. The tumors were graded according to Edmondson criteria. In 28 cases HCC was developed on the background of cirrhotic liver. In 9 instances the patients received chemoembolization before surgery. The presence of bcl-2 mRNA was assessed on paraffin-embedded, 4 microm-thick sections, using a standard in situ hybridization method with a commercially available bcl-2 probe (Maxim Biotech, USA), while the streptavidin-biotin immunohistochemical technique was employed to detect bcl-2 protein expression using the monoclonal anti-bcl-2 antibody (DAKO, USA). The results were expressed as % of tumor-positive cells following morphometric analysis. RESULTS: The in situ hybridization study revealed bcl-2 mRNA expression in 25 out of 35 (70%) HCC. In addition, bcl-2 mRNA was detected in hyperplastic cholangioles within fibrous septae in the periphery of the tumors. Immunohistochemical staining failed to reveal any bcl-2 protein expression in tumor cells of HCC, whereas hyperplastic cholangioles of the fibrous septae, in the periphery of the tumors and intratumoral lymphocytes displayed a strong-positive cytoplasmic (perinuclear) stain. No significant correlations were recorded between bcl-2 mRNA expression and tumor histological pattern, grade, stage and the use of previous chemoembolization. CONCLUSION: In hepatocellular carcinomas, the bcl-2 gene is frequently present but its protein product is absent. This suggests a post-translational mechanism of bcl-2 protein degradation, indicating that bcl-2 does not play a substantial role in the progress of hepatocellular carcinoma.     

Tumor necrosis factor-alpha promotes malignant pleural effusion

Tumor necrosis factor (TNF)-alpha is present in the microenvironment of human tumors, including malignant pleural effusion (MPE). Although the cytokine is produced in the pleural cavity by both tumor and host cells, its effects on MPE formation are unknown. In these studies, we sought to determine the role of TNF-alpha in the pathogenesis of MPE and to assess the therapeutic effects of its neutralization in a preclinical model. For this, MPEs were generated in immunocompetent mice using intrapleural injection of mouse lung adenocarcinoma cells. The roles of tumor- and host-derived TNF-alpha were assessed using combined experimentation with TNF-alpha gene-deficient mice and in vivo TNF-alpha neutralization. To expand the scope of preclinical data, TNF-alpha and vascular endothelial growth factor (VEGF) expression were determined in human cancer cell lines and human MPE. In the MPE model, TNF-alpha of host and tumor origin was present. TNF-alpha neutralization significantly limited tumor dissemination, effusion formation, vascular hyperpermeability, TNF-alpha and VEGF expression, and angiogenesis, thereby improving survival. In contrast, these variables were not different between TNF-alpha gene-sufficient and TNF-alpha gene-deficient mice. In mouse cancer cells, TNF-alpha functioned via nuclear factor-kappaB- and neutral sphingomyelinase-dependent pathways to induce TNF-alpha and VEGF, respectively. These results were recapitulated in human cancer cells, and a correlation was detected between TNF-alpha and VEGF content of human MPE. We conclude that tumor-derived TNF-alpha is important in the development of MPE in mice, and provide preclinical evidence supporting the efficacy of TNF-alpha blockade against malignant pleural disease.     

Inosine monophosphate dehydrogenase and myeloid cell maturation

In previous studies of purine ribonucleotide metabolism in the human myeloid leukemia cell line HL-60, we observed that there is a down- regulation of guanine ribonucleotide biosynthesis from the central intermediate, inosine monophosphate (IMP) and a depletion of intracellular guanosine triphosphate (GTP) and guanosine diphosphate (GDP) pools that occur during the induced maturation of these cells. We also found that inhibitors of IMP dehydrogenase, the enzyme that catalyzes the first step of guanylate synthesis from IMP, are potent inducers of HL-60 maturation. Because of these observations we specifically investigated the activity of IMP dehydrogenase in HL-60 cells and in a new inducible human myeloid leukemia cell line, RDFD2- 25, both during maintenance culture and during induced maturation of the cells. Enzyme activity was examined directly in cell extracts with a radiometric assay that measures free 3H2O formed from [2-3H] IMP during the conversion of IMP to XMP. Uninduced HL-60 and RDFD2 cells in maintenance culture were found to have high levels of IMPD activity (5.2 to 5.7 pmol IMP metabolized/10(7) cells/min) compared with normal neutrophils and monocytes that had been purified from blood (less than 1.5 pmol IMP metabolized/10(7) cells/min). However, when HL-60 and RDFD2-25 cells were induced to mature with retinoic acid (10(-6) mol/L), dimethylformamide (6 X 10(-2) mol/L), or a known IMPD inhibitor, tiazofurin (10(-6) mol/L), IMPD activity in the cells fell by 51% to 80% within three to six hours. These changes in IMPD activity preceded detectable functional and antigenic maturation of the cells by at least 12 hours and were not temporally related to changes in cellular proliferation. These findings are consistent with the concept that the regulation of myeloid cell maturation may be influenced by intracellular concentrations of guanine ribonucleotides because IMP dehydrogenase activity is known to be rate limiting for the production of these nucleotides.     

Presence of a platelet aggregating factor in the plasma of patients with thrombotic thrombocytopenic purpura (TTP) and its inhibition by normal plasma

Three patients with thrombotic thrombocytopenic purpura (TTP) were treated by infusion of normal plasma with dramatic responses. The plasmas collected from these patients during relapse induced in vitro aggregation of washed platelets from both normal donors and the patients during remission. The platelet aggregating factor was not dialyzable or adsorbable by Al(OH)3 and was not inactivated by diisopropylfluorophosphate, hirudin, or heparin in the presence of normal amounts of antithrombin. In contrast to the platelet aggregation induced by platelet isoantibody, the platelet aggregating activity of TTP plasma diminished as a function of time when it was incubated with normal plasma at 37 degrees C. These observations suggest that at least some instances of TTP appear to be due to deficiency of a plasma inhibitor to counteract a platelet aggregating factor demonstrated to be present in the plasma of these patients.