Andreas Neubauer

What Role Does Helicobacter pylori Eradication Play in Gastric MALT and Gastric MALT Lymphoma

The concept of mucosa-associated lymphoid tissue (MALT) has been introduced to differentiate biological functions from behavior of nonnodal vs. nodal lymphoid tissues. Lymphomas arising from MALT also behave differently than typical nodal lymphomas. In contrast to other tissues, MALT in the stomach is almost exclusively a result of Helicobacter pylori infection. Thus, MALT is part of the host defense against the pathogen H. pylori. Consequently, lymphomas arising from gastric MALT may be a clonal evolution starting from the infection. In low-grade gastric MALT lymphoma, cure of the infection may induce complete histological remission in the majority of patients. Investigators have recently reported that complete remission rate is between 70% and 80%. In an extended analysis, we have treated 84 patients with low-grade gastric MALT lymphoma in stage El, using a dual regimen to eradicate H. pylori. Complete remission was observed in 68 (80%) patients; a partial remission was found in 4 patients. In contrast, 12 patients showed no change and were referred to alternative treatment. In patients in complete remission, a polymerase chain reaction assay for the rearranged immunoglobulin heavy-chain gene remained positive in many cases. Together with data from the literature, these data suggest that the majority of patients with low-grade gastric MALT lymphomas in stage El respond to eradication of H. pylori. Longer follow-up investigations are necessary to determine if remissions indicate a cure from the disease.

Gastric MALT‐lymphoma and Helicobacter pylori infection

The presence of lymphoid tissue in the gastric mucosa is virtually pathognomonic of Helicobacter pylori infection. This lymphoid tissue has mucosa–associated lymphoid tissue (MALT) characteristics suggesting that H. pylori infection may represent a stimulus for the growth of gastric MALT lymphoma. H. pylori can be detected in more than 90% of patients with low–grade gastric MALT lymphoma supporting the aetiological role of the organism. The strongest evidence for the significance of H. pylori in the pathogenesis of low aetological–grade gastric MALT lymphoma is provided by clinical studies showing that cure of H. pylori infection is followed by a complete regression of these tumours in most patients. This paper reviews the current knowledge about antibacterial treatment of low–grade gastric MALT lymphoma, and immunological and molecular aspects in the pathogenesis of the disease.

Facilitated detection of oncogene mutations from exfoliated tissue material by a PNA-mediated 'enriched PCR' protocol

An ‘enriched polymerase chain reaction (PCR)’ protocol has been established for the sensitive detection of oncogene mutations in body fluid samples from cancer patients. This two‐step protocol combines an allele‐specific PCR clamping step followed by a PCR‐RFLP (restriction fragment length polymorphism) confirmatory step. The method thus resembles a nested PCR technique starting directly from genomic DNA material and, in no more than 54 PCR cycles, allows the sensitive detection of one mutant allele in 103 normal alleles. This protocol was tested on bronchial cytology samples and sputum taken from lung cancer patients and point mutations could be detected both in codon 12 of K‐ras and in three codons (248, 249, and 273) of the p53 gene. Comparing this protocol with a different ‘enriched PCR’ method based on repetitive PCR‐RFLP steps, a high concordance was noted between the two methods. Although the present protocol seems to be less sensitive by approximately one order of magnitude, it is much easier to perform and thus could be applied to the rapid but sensitive detection of allelic subfractions in a population of cells derived from exfoliative material. Copyright

RECENT PROGRESS ON THE ROLE OF AXL, A RECEPTOR TYROSINE KINASE, IN MALIGNANT TRANSFORMATION OF MYELOID LEUKEMIAS

Receptor tyrosine kinases (RTK) play an important role in the signal transduction of normal and malignant cells. There are different families of RTKs which are mainly characterized by differences in the ligang-binding extracellular domains. Axl (or UFO/Ark) is the first member of a new class of RTK with two fibronectin type III domains and two immunoglobulin-like domains present at the extracellular domain. The axl-gene has been isolated by means of gene transfection studies using DNA of patients with chronic myelogeneous leukemia. For a previous and the present study, we used a sensitive reverse-transcriptase polymerase chain reaction assay to detect axls mRNA in cells from normal and malignant hematopoietic tissue. Axls mRNA expression was mainly detected in myelo-monocytic cells, whereas much weaker transcription was seen in lymphatic cells and in lymphatic leukemias. In normal bone marrow, axl was heavily transcribed in marrow stromal cells. Further, we analysed Axl protein expression using monoclonal antibody M50 in peripheral stem cell harvests; in most harvests, no co-expression of CD34 and Axl was detected. However, in one patient with AML in complete remission, Axl was co-expressed on 80% of the CD34-positive population. These data show that axl is preferentially expressed in monocytes and stromal cells. Furthermore, a fraction of CD34-positive progenitor cells may express Axl. The exact mechanism for transformation of myeloid progenitor cells through Axl, however, remains to be determined.

Staphylococcal exoproducts down-regulate cyclooxygenase 1 and 2 in peritoneal macrophages.

Peritoneal macrophages (PMOs) are important components of the host defense against microbial infection in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Incubation of human PMOs with cell-free supernatant (BFS), prepared from Staphylococcus aureus, inhibited prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) production. Slot-blot analysis of cyclooxygenase-1 (Cox-1) and Cox-2 demonstrated a decrease in both Cox-1 (29%) and, to a greater extent, Cox-2 (65%) protein expression after BFS stimulation. When competitive polymerase chain reaction (PCR) was used, the peak levels of Cox-1 and Cox-2 messenger ribonucleic acid (mRNA) in unstimulated PMOs were 0.304+/-0.13 pmol/L and 9.61+/-2.84 pmol/L (mean+/-SEM, n = 3), respectively. After exposure of samples to BFS for 30 minutes, the level of Cox-2 mRNA was reduced to 0.59+/-0.449 pmol/L (16-fold reduction, p < 0.05), and the level of Cox-1 mRNA was reduced to 0.02+/-0.002 pmol/L (15-fold reduction, p < 0.05). In contrast, these same PMOs showed an increased expression of IL-6 mRNA and increased secretion of IL-6 protein. These results indicate that prostaglandin production in PMOs is regulated by alterations in both immunoreactive Cox-1 and Cox-2. The down-regulation of Cox metabolism in these cells is primarily related to the delayed and depressed increase in the Cox-2 gene product.

Potential of Autologous Immunologic Effector Cells for Prediction of Progression of Disease in Patients with Chronic Myelogenous Leukemia

In autologous bone marrow transplantation, immunologic effector cells such as lymphokine activated killer (LAK) cells may be useful for purging of bone marrow since these cells might have an additional in vivo effect on tumor cells in contrast to other purging protocols. Recently, immunologic effector cells termed cytokine-induced killer (CIK) cells have been shown to be more useful than LAK cells for purging of autologous BM in the context of autologous BMT. Here, we show that the expression of bcr/abl in CIK cells generated from patients with CML correlates with progression of disease in individual patients. In addition, progression of disease from chronic phase to accelerated phase could be predicted in two patients by studying the expression of bcr/abl in CIK cells generated from CML patients. Thus, it might be possible to use CIK cell generation for the prediction of progression of disease in CML patients.