Objective: To investigate the expression of B7 co-stimulatory molecules in human multiple myeloma (MM) and the immunoregulatory effects of thalidomide on B7.1 co-stimulator.
Methods: The immunoregulatory effects of thalidomide on the expression of B7-1 in human MM cell line was examined by detecting the changes in the expression of B7 co-stimulator on the cells using flow cytometry following the drug treatment.
Results: The expression of B7.1 co-stimulator was lowly expressed in human MM cell line and MM patients, with a positivity rate of 0.8 and (2.19-/+2.13) for B7.1 and a rate of 26.4 and (30.28-/+28.11) for B7.2, respectively. Compared with the control group, the thalidomide-treated cells showed significantly increased percentage of CD-80 positive cells in a dose-dependent manner (but not at 0.1 microg/ml) (P<0.01), with the highest percentage reaching (17.7-/+1.53)% at thalidomide concentration of 5 microg/ml.
Conclusion: MM cells express low or undetectable levels of B7.1. Thalidomide can up-regulate the expression of B7-1 molecules on myeloma cells, which is probably one of the therapeutic mechanisms of thalidomide.