CD34-positive cells were isolated from cord blood ( n = 8), bone marrow ( n = 4) and leukapheresed material ( n = 7), using an immunomagnetic isolation technique, MACS (Miltenyi Biotec, Bergisch Gladbach, Germany). In flow cytometric analysis, cell populations after enrichment revealed a fraction of 96.1% (cord blood), 96.2% (bone marrow) and 98.6% (leukapheresis material) CD34-positive cells. Cells were further stained with antibodies specific for CD44 isoforms: CD44s (SFF-2), CD44v5 (VFF-8) and CD44v6 (VFF-18). CD44-positive cells were detected by directly (FITC, fluorescein isothiocyanate) or indirectly (streptavidin-PE, phycoerythrin)-conjugated fluorochromes in flow cytometric analysis. Analysis was restricted to CD34-positive cells. A high expression of CD44s was noted in all kinds of material under investigation with mean values in the range of 98.6–100%. There was little expression of CD44v6 (mean values in the range of 1.5–3.6%) and very slight expression of CD44v5 (mean values in the range of 0.6–1.4%). The finding that CD34-positive hematopoietic stem cells express CD44v5 and CD44v6 to a very small extent offers the possibility of using antibodies specific to CD44v5 and CD44v6 in immunopurging in the course of autologous stem cell transplantation.

A new human cell line (Wa-2) derived from an extrarenal rhabdoid tumor has been established. The cell line grows as a monolayer consisting of round- and spindle-shaped cells. Injection of cells into nude mice results in the growth of solid tumors within 2 wk of inoculation. These solid tumors have the microscopic appearance similar to that of the original tumor from which the cell line was derived. Moreover, the tumor cells have all the features of rhabdoid tumors, including the intracytoplasmatic hyaline globules, large prominent nucleoli, and inclusion bodies made up of whorls of fibrillary material. Transplanted tumor cells stain positive for vimentin, cytokeratin, actin, and desmin and negative for myoglobin and neuron-specific enolase. Karyotyping of the cell line at different passages and cells derived from the transplant tumors consistently revealed a diploid number of chromosomes with a reciprocal translocation between chromosomes 18 and 22 [t(18;22) (q21;p11.2)]. In fibroblasts derived from the patient, no translocation could be found. Culturing the cells in the presence of 1-beta-D-arabinofuranosylcytosine induces differentiation, characterized by the outgrowth of neuron-like processes and the morphological appearance of cells similar to neuroblasts. Southern blot analysis showed no amplification of the N-myc oncogene. Since no published cell line derived from rhabdoid tumors exists, this cell line should be helpful to further elucidate the biology and histological origin of the malignant rhabdoid tumor.

Sera of human colonic carcinoma xenografted rnunu rats were used to immunize rnu/+rats in order to obtain an immune response against circulating human tumor-associated components. After fusion of rat spleen cells with mouse myeloma cells monoclonal antibody MAB 108 could be established which reacted with two 40 and 45 kD cytokeratins as well as with vimentin, with a soluble 37 kD protein apparently derived from the 45 kD protein and with a 37 kD protein released by tumor cells. The MAB 108-specific epitope was also detected in tissue polypeptide antigen (TPA), a human tumor-associated antigen originally described by Björklund et al. (22).