Inflammatory environment created by fibroblast aggregates induces growth arrest and phenotypic shift of human myeloma cells.

Multiple myeloma (MM) is characterized by accumulation of clonal plasma cells (PCs) predominantly in the bone marrow but tumor cells appear in the circulation in significant numbers as the disease progress. The occurrence of circulating multiple myeloma cells raises question concerning interactions between these cells and stroma of peripheral organs specifically under certain pathophysiological conditions, e.g., inflammation. Therefore, in the present study we exposed three human multiple myeloma cell lines to sterile inflammation produced in a culture dish by clusters of cell-cell contact-activated dermal fibroblasts. We now observed that myeloma cells responded differently to this particular type of stromal cell activation, nemosis. Two cell lines U-266 and LP-1 were minimally affected by the proinflammatory signalling, while the third cell line RPMI 8226 responded with growth arrest and altered expression of three phenotypic markers CD38, CD45, and CD138, indicating dedifferentiation shift of these cells to less mature PC-like phenotype. In a preliminary study we identified a subclone of cells having similar phenotype in 14 out of 23 analysed specimens of MM patients. This set of data indicates that the observed phenomenon might be clinically relevant. Our results emphasize the potential role of activated stromal fibroblasts and subsequent inflammation in altering phenotype of PCs and directing myeloma progression towards dormancy. Given the significant implication of dormant myeloma cells that might serve as a major cellular basis for the relapse, understanding their unique biology and precise elucidation of the underlying molecular mechanisms for the maintenance of quiescence is important. Therefore, we consider this study as a particular contribution to development of experimental model for in vitro studies of cancer dormancy.

Collection of peripheral hematopoietic stem/progenitor cells.

OBJECTIVES: Several variables possibly affecting collection of peripheral hematopoietic stem/progenitor cells (PBSC) were evaluated: type of apheresis machine (Amicus version 2.5, Baxter vs Cobe Spectra version 7.0, Terumo BCT), venous access (peripheral vein vs central venous catheter, i.g. CVC), and apheresis regimen (standard vs large volume leukapheresis, i.g. SVL vs LVL) with the objective to increase collection efficacy at the site. BACKGROUND: Peripheral blood represents the currently preferred source of hematopoietic stem/progenitor cells (HSCs) for transplantation. METHODS: Data regarding 169 collection procedures performed in healthy donors and patients between January 2008 and December 2011 at the Clinics of Haematology and Transfusiology in St Cyril and Method Hospital in Bratislava (Slovakia) were analysed. RESULTS: With Cobe Spectra apheresis machine it was possible to process larger blood volumes per procedure with higher CD34+ cell collection efficiency (p = 0.0229) and lower RBC contamination of the harvest than with Amicus (p = 0.0116). On the other hand, Amicus helped to limit PLT contamination of the harvest (p < 0.0001), thus minimizing post-procedural decrease in patient´s PLT count. The highest detected advantage of CVC usage was higher flow rate of procedure, thus processing larger blood volumes per unit of time. Interesting finding was the tendency to lower harvest PLT contamination (p = 0.054). When LVL was performed, significantly higher HSCs yields were collected, even in "poor mobilizers" when the pre-run parameters were low. CONCLUSION: Management of PBSC collection requires a particular approach in each subject. Institutionally and individually optimized collection may help to improve the transplantation outcome and decrease the financial costs (Tab. 8, Ref. 15).