In a previous study we demonstrated high expression of the non-coding BIC gene in the vast majority of Hodgkin's lymphomas (HLs). Evidence suggesting that BIC is a primary microRNA transcript containing the mature microRNA-155 (miR-155) as part of a RNA hairpin is now accumulating. We therefore analysed HL cell lines and tissue samples to determine whether miR-155 is also expressed in HL. High levels of miR-155 could be demonstrated, indicating that BIC is processed into a microRNA in HL. Most non-HL subtypes were negative for BIC as determined by RNA-ISH. However, in diffuse large B cell lymphoma (DLBCL) and primary mediastinal B cell lymphoma (PMBL), significant percentages of positive tumour cells were observed in 12/18 and 8/8 cases. A higher proportion of tumour cells were positive for BIC in DLBCL with activated B cell-like phenotype than in DLBCL with germinal centre B cell-like phenotype. Differential BIC expression was confirmed by qRT-PCR analysis. Northern blot analysis showed expression of miR-155 in all DLBCL and PMBL derived cell lines and tissue samples analysed. In summary, we demonstrate expression of primary microRNA BIC and its derivative miR-155 in HL, PMBL and DLBCL.

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Allogeneic transplantation of peripheral blood progenitor cells (PBPC) makes the general anaesthesia of the donor unnecessary and may result in more rapid engraftment and faster recovery of the immune system. We have studied G-CSF-mediated PBPC mobilization in healthy donors and analysed the cellular composition of the resulting PBPC grafts. PBPC grafts were obtained from nine healthy donors (18-67 years old) for allogeneic or syngeneic transplantation. Six donors received 10 micrograms/kg G-CSF per day, the others 5-6 micrograms/kg. Mobilization and harvesting were well tolerated except for moderate bone pain which occurred in all donors primed with 10 micrograms/kg. With 10 micrograms/kg, a 31-fold (9-62) enrichment of circulating CD34+ cells was observed with peak values constantly occurring on day 5 after the start of G-CSF administration. Starting harvest on day 5, one to three collections on consecutive days yielded 5.5 x 10(6)/kg (0.9-10.7) CD34+ cells, 219 x 10(6)/kg (106-314) T cells, and 34 x 10(6)/kg (23-67) NK cells per 10 litres leukapheresis volume. Altogether, PBPC grafts contained 3 times more CD34+ cells, 7 times more T cells, and 20 times more NK cells than five allogeneic marrow grafts that were analysed for comparison. The yield of CD34+ cells per 10 litres apheresis volume as well as the height of the CD34+ peak in peripheral blood were inversely correlated to the age of the donor. In the donors primed with 5-6 micrograms/kg G-CSF the increase of circulating CD34+ cells (4-7-fold enrichment) and the CD34+ cell yield per 10 litres leukapheresis volume (1 x 10(6)/kg [0.8-2.2]) was much smaller compared with the 10 micrograms/kg group. In conclusion, sufficient amounts of PBPC capable of restoring haemopoiesis in allogeneic recipients can be mobilized safely by administration of G-CSF (10 micrograms/kg s.c. for 5 d) in healthy donors, and harvested with one or two leukapheresis procedures. Whether the large numbers of T-cells and NK cells that are contained in the collection products may influence graft-versus-host and graft-versus-leukaemia reactivities of PBPC grafts remains to be determined.

In a search for genes specifically expressed in Reed-Sternberg (RS) cells of Hodgkin lymphoma (HL), we applied the serial analysis of gene expression (SAGE) technique on the HL-derived cell line DEV. Genes highly expressed in DEV were subjected to an RT-PCR analysis to confirm the SAGE results. For one of the genes, a high expression was observed in DEV and other HL-derived cell lines but not in non-Hodgkin lymphoma (NHL)-derived cell lines and normal controls, suggesting an HL-specific expression. This gene corresponds to the human BIC gene, a member of the noncoding mRNA-like molecules. RNA in situ hybridization (ISH) indicated an exclusive nucleolar localization of BIC transcripts in all RS cells in 91% of HL cases, including nodular lymphocyte predominance (NLP) HL and classical HL. Analyses of normal human tissues revealed BIC transcripts in only a small number of CD20-positive B-cells in lymph node and tonsil tissue, albeit at a much lower level compared to that of RS cells. BIC RT-PCR in the Burkitt lymphoma-derived cell line Ramos demonstrated a significant up-regulation upon cross-linking of the B-cell receptor (BcR). IkappaBalpha-mediated blocking of NF-kappaB translocation in Ramos did not effect the up-regulation of BIC expression upon BcR triggering, suggesting that activation of NF-kappaB is not involved in regulation of BIC expression. In summary, our data show that expression of BIC is specific for RS cells of HL. In normal tissue, BIC is expressed weakly in a minority of germinal center B cells. Expression of BIC can be modified/influenced by BcR triggering, indicating that BIC might play a role in the selection of B cells.