Friedhelm Herrmann

The mitogenic response to tumor necrosis factor alpha requires c-Jun/AP-1.

In the present study, we addressed the role of the c-jun proto-oncogene in the mitogenic response of human fibroblasts and primary acute myelogenous leukemia blasts to tumor necrosis factor alpha (TNF-alpha). Our data indicate that TNF-alpha treatment of these cells is associated with transcriptional activation of c-jun, resulting in accumulation of c-jun mRNA and protein expression. In order to elucidate the role of c-Jun/AP-1 in TNF-mediated growth stimulation, the antisense (AS) technique was used. Uptake studies of oligonucleotides were performed with fibroblasts, demonstrating that incorporation of oligomers was maximal at 4 h. Oligodeoxynucleotides remained stable in these cells for up to 24 h. Treatment of fibroblasts with the AS oligonucleotide resulted in intracellular duplex formation followed by an efficient translation blockade of c-Jun/AP-1. In contrast, sense (S) and nonsense (NS) oligodeoxynucleotides failed to form intracellular duplexes and also did not interfere with translation of c-Jun/AP-1, suggesting specific elimination of c-Jun/AP-1 by the AS oligomer. Fibroblasts cultured in the presence of the AS oligonucleotide but not those cultured in the presence of the S or NS oligonucleotide failed to respond proliferatively to TNF-alpha. These findings could be confirmed by experiments with primary acute myelogenous leukemia blasts, which also demonstrated that TNF-induced growth stimulation required c-Jun/AP-1 function. Taken together, our results indicate that activation of c-Jun/AP-1 plays a pivotal role in the signaling cascade initiated by TNF, which leads to a proliferative response of its target cells.

CD30 Ligand, a Member of the TNF Ligand Superfamily, with Growth and Activation Control for CD30+ Lymphoid and Lymphoma Cells*

Hodgkin disease (HD) is characterized by the presence of a small number (usually <1% of total tumor mass) of the typical Hodgkin and Reed-Sternberg (H-RS) cells in a hyperplastic background of normal reactive lymphocytes, plasma cells, histiocytes, neutrophils, eosinophils, and stromal cells. HRS cells produce various cytokines, growth factors, and express cytokine receptors and activation antigens, implying a predominant role for these molecules in the pathophysiology of Hodgkin disease. HD may therefore be regarded as a tumor of cytokine producing cells. The CD30 antigen has been characterized as a marker for cultured and primary Hodgkin and Reed-Sternberg cells, and was found to be overexpressed in Hodgkin disease and a subgroup of non-Hodgkin lymphomas including large cell anaplastic lymphomas and Burkitt lymphomas. The molecular cloning of the CD30 antigen revealed that CD30 is a member of the tumor necrosis factor/nerve growth factor receptor superfamily. The cloning of the cognate for CD30, currently termed CD30 ligand, confirmed that the CD30 antigen functions as a cytokine receptor. Recombinant CD30 ligand is a membrane-bound protein with pleiotropic biological activities for different CD30+ lymphoma types, but also for the immune system, mainly T cells. CD30L belongs to the emerging tumor necrosis factor ligand superfamily. The CD30-CD30 ligand interaction could have a critical pathophysiological role in malignant lymphomas, particularly Hodgkin disease, large cell anaplastic lymphomas and Burkitt lymphomas, and is also involved in activation and functioning of the T cell-dependent immune system.

Ribozymes: biology, biochemistry, and implications for clinical medicine

Ribozymes are a class of ribonucleic acid (RNA) molecules that possess enzymatic properties. Upon binding to complementary nucleic acid strands, catalytic degradation takes place via a cleavage reaction. In effect, inactivation of susceptible substrate RNA molecules takes place at a catalytic rate and with a high degree of substrate specificity. This article reviews the biology and biochemistry of this class of molecules and its potential applications in clinical medicine.

Molecular Mechanisms of Ara-C Signalling: Synergy and Antagonism with Interleukin-3

Cytosine arabinosde (Ara-C) is the most widely used and most effective agent in the treatment of acute myelogenous leukemia [1]. Several lines of evidence have suggested that the efficacy of Ara-C may be enhanced by its combination with hematopoietic growth factors such as Interleukin (IL)-3 or Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) [2]. IL-3 has been shown by several laboratories to enhance Ara-C incoporation into DNA and Ara-C-mediated tumor cell kill by recruiting resting cells into the cell cycle but also by facilitating intracellular Ara-C metabolism into its active compound, Ara-CTP [3,4]. However, other reports have indicated that IL-3 may also confer resistance of acute myelogenous blasts to subsequent Ara-C [5]. It is thought that Ara-C exerts its cytotoxic effects after incorporation into DNA leading to inhibition of chain elongation [6,7]. In addition, more recent reports have indicated that Ara-C also induces features of apoptotic cell death including DNA fragmentation [8]. Ara-C modulates mRNA expression of several proto-oncogenes, such as c-jun, jun-B or c-myc [3,9,10]. Singaling events initiated by Ara-C, however, are still enigmatic. The present article explores signaling cascades initiated by Ara-C and point to their impact in mediating both synergistic and antagonistic effects of Ara-C and IL-3.

Molekulargenetische Grundlagen in der Tumortherapie

Die normale Zelle unterliegt in ihrem biologischen Verhalten der Kontrolle extrazellularer Signale. Die Einsicht in die Prinzipien der Signalerkennung und Verarbeitung, in die Regeln der interzellularen Kommunikation und des intrazellularen Zusammenspiels von Proteinen mit Proteinen und DNS wird zusehends erweitert und vertieft. In Einzelfallen ist es moglich, die Schritte der Signaltransduktion. von der Ligandbindung uber die Rezeptoraktivierung und Aufschlusselung der an der Signalubertragung teilhabendenen Molekule bis hin zur Aktivierung distinkter genetischer Programme im Kern zu verfolgen. Errungen wurde dieser Kenntnisgewinn durch detaillierte biochemische und molekularbiologische Untersuchungen intrazellularer Vorgange und nicht zuletzt mit der durch Kristallographie und NMR-Technologie ermoglichten Aufklarung der dreidimensionalen Struktur von Molekulen und ihren Interaktionen. Entscheidende Hinweise fur die Aufdeckung von Protein-Funktionen und Protein-Interaktionen kamen zudem aus der molekularbiologischen und biochemischen Charakterisierung genetischer Veranderungen, die Tumorentstehung und Tumorprogression begleiten. Dies hat es erlaubt, nicht nur eine grosere Anzahl von (Krebs)genen zu identifizieren, ihre genetische Information zu entschlusseln und die biologische Funktion ihrer Proteine zu charakterisieren, sondern hat auch unser Verstandnis physiologischer Regulationsmechanismen grundlegend erweitert. Die Kenntnis der molekularen Zusammenhange von Krebsentstehung und Krebsprogression ist eine solide Grundlage fur die Entwicklung neuer therapeutischer Interventionsmoglichkeiten, die neben gentherapeutischen Ansatzen auch die Entwicklung neuartiger Wirksubstanzen umfassen.