WT1 and BCR-ABL specific small interfering RNA have additive effects in the induction of apoptosis in leukemic cells.

BACKGROUND AND OBJECTIVES: The Wilms' tumor gene (WT1) is aberrantly over-expressed in leukemic cells. Therefore, we wanted to study the effect of small interfering (siRNA) targeting WT1 in leukemic cells and normal CD34-positive cells with regard to proliferation, induction of apoptosis, and cell differentiation. Furthermore, we wanted to evaluate whether the additional use of BCR-ABL siRNA could increase the anti-leukemic effects of WT1 siRNA in chronic myeloid leukemia (CML) cells. DESIGN AND METHODS: We measured WT1 expression by reverse transcription polymerase chain reaction (RT-PCR) in various cell lines and in leukemic cells from patients, then transfected the cells with WT1-specific and BCR-ABL-specific siRNA before carrying out microarray analysis. We used the tunnel assay to measure apoptotic cells. RESULTS: We observed a reduction of WT1 gene expression, measured by real-time RT-PCR, in all studied cell lines: K-562, Kasumi-1, MV 4-11 and NB-4, as well as in cells of AML and CML patients. The results also demonstrated that WT1 siRNA significantly induced apoptosis and inhibited proliferation in MV4-11 cells, NB-4 cells, Kasumi-1 cells (p<0.01) and in K-562 cells (p<0.02) versus controls. In normal CD34-positive cells, the proliferation was only slightly inhibited (by about 20%) and no induction of apoptosis was found. Combined transfection with WT1 and BCR-ABL siRNA together in K-562 cells increased the inhibition of the rate of proliferation and the rate of induced apoptosis compared to transfection with BCR-ABL siRNA or WT1 siRNA alone (p<0.01). We found that most genes involved in cell signaling and protein metabolism were regulated by the WT1 gene in K-562 cells in a microarray analysis. INTERPRETATION AND CONCLUSIONS: In conclusion, WT1 might be a suitable target for new therapeutic strategies using siRNAs in leukemic cells.

Total-body irradiation--role and indications: results from the German Registry for Stem Cell Transplantation (DRST).

BACKGROUND AND PURPOSE: Total-body irradiation (TBI) is a key part of the conditioning regimen before hematopoietic stem cell transplantation (HSCT). The exact role of TBI as part of the conditioning regimen is largely unclear. In order to determine the relevance of TBI, the status of TBI utilization was analyzed on the basis of a nationwide registry. MATERIAL AND METHODS: 14,371 patients (1998-2002) documented in the German Stem Cell Transplantation Registry (DRST) were analyzed regarding TBI utilization prior to autologous or allogeneic transplantation, underlying disorder, type of donor, stem cell source, and size of the treatment center. RESULTS: For autologous HSCT approximately 10% of the patients (873/8,167) received TBI, with chronic lymphocytic leukemia (CLL, approximately 80%, 171/214) and low-grade non-Hodgkin's lymphoma (l-NHL, approximately 35%, 330/929) being the most important disorders. In the allogeneic setting 50% of the patients (2,399/4,904) received TBI, with acute lymphocytic leukemia (ALL, 85%, 794/930), acute myeloid leukemia (AML, 45%, 662/1,487) and chronic myeloid leukemia (CML, 49%, 561/1,156) being the key indications. The type of donor, stem cell source and center size did not strongly influence the use of TBI. CONCLUSION: TBI has only a limited role for the conditioning prior to autologous HCST. For allogeneic HSCT TBI is widely accepted with no major changes over the observation time. The use of TBI is generally accepted for ALL, whereas approximately half of the patients with CML or AML received TBI. Although a considerably large database was analyzed, no clear determinants for the use of TBI could be distinguished.