OBJECTIVETo investigate the apoptosis effect of diffuse large B-cell lymphoma cell line (DLBCL) SUDHL-4 induced by IL-21 and its related mechanism.

METHODSSUDHL-4 cells were treated with IL-21 at different concentration (1000 ng/ml, 100 ng/ml, 10 ng/ml, 1 ng/ml) for 24 h, 48 h, 72 h, respectively. The inhibitory rate of cell proliferation was detected by CCK-8 assay. The cell growth curves were drawn and half inhibitory concentration (IC(50)) values were calculated. The cell apoptosis were detected by flow cytometry (FCM), the expression of the caspase-9, caspase-3, cleaved caspase-3, Bcl-2, Bcl-XL, Bid, Bax and c-myc protein in SUDHL-4 cells treated with IL-21 by western blot, the mRNA expression of Bcl-2, Bcl-XL, Bid, Bax, c-myc by Survivin gene with RT-PCR.

RESULTSIL-21 markedly inhibited SUDHL-4 cell growth in a time- and dose-dependent manner. The 48 hIC(50) was 140.9ng/ml; The FCM showed that the apoptosis proportion of SUDHL-4 cells treated with 100 ng/ml of IL-21 apoptosis (AnnexinV-FITC(+) positive cells) gradually increased (48 h: 19.7 ± 2.3%). The protein expression of caspase-9, caspase-3, Bcl-2 and Bcl-XL decreased in a time-dependent manner. The Bax and c-myc protein markedly increased, but the Bid protein level did not change. IL-21 up regulated c-myc and Bax gene expression, however down regulated Bcl-2 and BCL-XL gene expression, but the gene expression of Bid and Survivin hadn't been changed significantly.

CONCLUSIONSIL-21 can inhibit proliferation and induce apoptosis of SUDHL-4 cell. The mechanism may involve in endogenous mitochondrial pathway mediated by the c-myc and the Bcl-2 genes.