Objective: To evaluate the mechanism and influence of thalidomide on interleukin-6 (IL-6), IL-6 receptor (IL-6R) and its transmitting chain in multiple myeloma patients.
Methods: Serum level of IL-6, expression of IL-6R on myeloma cells and IL-6R beta mRNA in multiple myeloma patients were measured by enzyme linked immunosorbent assay (Elisa), flow cytometry and reverse transcription polymerase chain reaction (RT-PCR).
Results: Serum level of IL-6 in multiple myeloma patients was 564.8 +/- 319.4 ng/L, with a positive rate on the myeloma cells of 33.6% before oral 200 mg/d thalidomide. They were 560.3 +/- 414.8 ng/L and 31.8% on D14 after oral 200 mg/d thalidomide, which were not significantly different as compared with those before (P > 0.05). On D14, 28, 42, 56 and 84 after oral 400 mg/d thalidomide, the serum level of IL-6 in multiple myeloma patients were 516.7 +/- 131.9 ng/L, 426.7 +/- 180.4 ng/L, 387.9 +/- 187.4 ng/L, 350.1 +/- 85.5 ng/L and 212.3 +/- 92.5 mg/L, with positive rates on the myeloma cells of 28.5%, 24.3%, 21.3%, 12.6% and 10.1%, which were all lower than those before oral 200 mg/d thalidomide (P < 0.05 or P < 0.01). Ratios before and on D14 after oral 200 mg/d thalidomide were 7.8 and 6.9, with no statistical significance (P > 0.05). Ratios on D14, 28 after oral 400 mg/d thalidomide were 5.3 and 2.7, which were lower than those before oral 200 mg/d thalidomide (P < 0.01).
Conclusion: Reduction of serum level of IL-6 in multiple myeloma patients and decrease in IL-6R expression on the myeloma cells and IL-6R beta mRNA occur on D14 after oral 400 mg/d thalidomide. These changes become more obvious with time. The antitumor mechanism of thalidomide may be related to reduction of IL-6 serum level in multiple myeloma patients and decrease in IL-6R expression on the myeloma cells and IL-6R beta mRNA.