Purging of myeloma cells using all-trans retinoic acid in a mouse model.
OBJECTIVE
The 5T33 murine model of multiple myeloma was used to investigate the potential of all-trans retinoic acid (ATRA) to purge clonogenic myeloma cells from autologous hemopoietic stem-cell harvests by differentiating immature 5T33 cells into terminal-stage plasma cells with limited repopulation capacity.


METHODS
5T33 cells were treated with 10 microM ATRA and the effect on cell clonogenicity was determined by measuring the time to paraprotein detection in C57Bl/KaLwRij mice compared to control animals. Cell differentiation and apoptosis following ATRA treatment were investigated using flow cytometry and caspase-3 assay. Treatment with ATRA resulted in a 33% reduction in the in vitro cloning efficiency of 5T33 cells. Reduced in vitro clonogenicity of 5T33 cells following ATRA treatment was supported by a 16-49% increase in the time taken for C57Bl/KaLwRij mice to develop paraprotein following injection of 5T33 cells pretreated with ATRA for 8 days. Although ATRA was shown not to alter the in vitro growth characteristics of 5T33 cells, significant inhibition of apoptosis was observed.


RESULTS
Treatment with ATRA also resulted in an increase in the proportion of 5T33 cells expressing the CD54 adhesion molecule, which is known to be highly expressed on mature myeloma cells.


CONCLUSIONS
The ability of ATRA to decrease the clonogenicity of 5T33 cells in vitro and increase the time to disease development in vivo suggests that this drug may be useful for purging autologous stem cell harvests in the clinical setting.
Department of Haematology and Genetic Pathology, Flinders University of South Australia and Flinders Medical Centre, Bedford Park, South Australia 5042, Australia.
J M
JM
Henry
A A
AA
Morley
P J
PJ
Sykes
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016465:Bone Marrow Purging / Q000379:methods*; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D009101:Multiple Myeloma / Q000097:blood / Q000473:pathology*; D009194:Myeloma Proteins / Q000032:analysis; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000187:drug effects; D010950:Plasma Cells / Q000187:drug effects; D014182:Transplantation, Autologous; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014410:Tumor Stem Cell Assay
D009194:Myeloma Proteins; D018799:Intercellular Adhesion Molecule-1; D014212:Tretinoin