[Down-regulation of expression of survivin and induction of apoptosis in the human Burkitt lymphomas cells by ligation of CD40-CD40L].

Objective: To study the biological effects of ligation of CD40 mediated by soluble recombinant human CD40 ligand (srhCD40L) on the human malignant hematogenous cells and to explore the molecular mechanism thereof.

Methods: Human Burkitt lymphoma cells of the line CA46 were cultured. Flow cytometry was used to detect the expression of CD40 molecule on the cell surface. CA46 cells were put into 96-well plate and added with solutions of srhCD40L of the terminal concentrations of 0.04 microg/ml, 0.2 microg/ml, 1.0 microg/ml, and 5.0 microg/ml respectively, and 24, 28, 72, 96, and 120 hours later cell growth curve was drawn. MTT assay was used to other CA46 cells co-incubated with srhCD40L of the terminal concentrations of 0.04 microg/ml, 0.2 microg/ml, 1.0 microg/ml, and 5.0 microg/ml respectively so as to calculate the proliferation inhibition rate. CA46 cells were treated with srhCD40L of the concentrations of 1.0 microg/ml for 24, 48, and 72 hours respectively, FCM was used to analyze the DNA cycle and TUNEL was used to calculate the apoptotic rate. Annexin-V labeling method was used to detect the positive rate of apoptotic cells. CA46 cells were treated with srhCD40L of the concentration of 1 microg/ml for 24, 48, 72, or 96 hours, semi-quantitative RT-PCR was used to detect the mRNA expression of survivin, an anti-apoptosis protein, and the protein expression of survivin was detected by Western blotting.

Results: The expression rate of CD40 in the human Burkitt CA46 cells was 99%. srhCD40L dose-dependently inhibited the proliferation of the CD46 cells. Treated by srhCD40L, the progress of cells at S stage into G(2)/M stage was inhibited. TUNEL showed that treated by srhCD40L (1.0 microg/ml) for 24, 48, and 72 hours the apoptotic rates of the cells were 9%, 18%, and 35% respectively. Annexin-V showed that after incubation with srhCD40L (1.0 microg/ml) for 24 h the apoptotic rate was 10.04%. Two apoptotic peaks appeared 48 and 72 hours later. Semi-quantitative RT-PCR and Western blotting showed that the survivin mRNA expression and protein expression were both down-regulated.

Conclusion: Ligation of CD40 by srhCD40L inhibits the proliferation of malignant hematogenous cells and induces their apoptosis. Expression of survivin mRNA and protein may be related to cell growth inhibition and to the apoptosis mediated by Ligation of CD40 by srhCD40L.