The MDM‐2 (murine double minute 2) gene codes for a cellular protein that can bind to the p53 tumor suppressor gene product, thereby functioning as a negative regulator of p53. In order to define the role of the MDM‐2 gene in the pathogenesis of human acute myeloid leukemia, the expression and the sequence of the MDM‐2 gene were examined in samples of bone marrow and/or peripheral mononuclear cells of 38 patients by using immunostaining, polymerase chain reaction (PCR), single strand conformation polymorphism, and sequencing. Immunohistochemical staining detected a weak accumulation of the MDM‐2 protein in AML patients of FAB classification M4 and M5. RT‐PCR analysis revealed a heterogeneous expression pattern of MDM‐2 mRNA in AML samples of different FAB classification. An increased level of MDM‐2 mRNA expression was observed in 17 of 38 AML patients when compared to normal controls. No structural changes in a 488 bp region extending from nucleotide 890 to 1378 of the MDM‐2 cDNA were detected using RT‐SSCP and sequence analysis. In addition, heterogeneous expression of p53 transcripts was found with the highest p53 mRNA levels in AML M4 and M5. Interestingly, there seems to be a correlation between the relative ratios of p53 and MDM‐2 mRNA levels in AML M4 and M5: in 15 of 23 cases high p53 mRNA expression was directly associated with high levels of MDM‐2 transcripts. An exclusively intranuclear p53 immunostaining pattern was found in 10 of 16 (58%) AML FAB M4 and M5, whereas the remaining AML samples tested were negative for p53 (0/10). Using RT‐SSCP analysis and direct sequencing of the RT‐PCR amplification products of p53 exon 5–8, we observed that only 1 of 38 AML patients showed a point mutation in the p53 gene. This missense mutation occurred in the evolutionary highly conserved region of p53 at codon 255 (Ile to Phe). These data indicated that structural alterations of the p53 gene do not play an important role in the initiation and progression of AML. However, abrogation of p53 tumor suppressor function due to MDM‐2 overexpression may be an alternative molecular mechanism by which a subset of AMLs may escape from p53‐regulated growth control.

Erythropoietin (EPO) is a potent regulator of the viability, proliferation and differentiation of erythroid progenitor cells. Its effect is mediated by binding to the erythropoietin receptor (EPO-R), a member of a new cytokine receptor family. Alterations of the EPO/EPO-R system have recently been shown to be involved in the pathogenesis of familial erythrocytosis and polycythaemia vera (PV). In order to define whether genetic changes in the EPO-R gene and its ligand play a role in the development of PV, the structure and expression levels of the EPO-R and EPO genes were examined in samples from bone marrow and/or peripheral blood mononuclear cells of 24 patients with PV. As expected, EPO serum levels were low and no detectable level of EPO mRNA was found by reverse polymerase chain reaction (RT-PCR) in the peripheral blood mononuclear cells of our PV patients. To search for structural alterations of the EPO-R, cDNA samples were subjected to PCR and SSCP analysis as well as sequencing. Heterogenous expression of EPO-R mRNA was observed without any structural changes, as revealed by RT-SSCP analysis using overlapping primers spanning the whole coding region of the EPO-R gene. Structural integrity of the EPO-R was further confirmed by sequencing of cloned PCR products. These data suggest that the mechanisms for the development of PV do not involve structural changes of the EPO-R gene.

In this randomised prospective study we investigated whether treatment results of maximal androgen blockade (MAB) in patients with metastatic prostatic cancer can be further improved by additional Methotrexate therapy (MTX). A total number of 61 patients (stage T1 or '1"2) have been included and 31 were randomised to arm A receiving MAB, i.e. orchiectemy + flutamide (3x250 rag/d). In group B 30 patients were treated with MAB + 50 mg{m 2 MTX (once weekly for 4 months). 53 patients are evahiable for response criteria.