Synergistic Antitumor Effect of Everolimus Combined with Gemcitabine on Diffuse Large B-Cell Lymphoma

Abstract

To investigate the effects of mTOR inhibitors everolimus (EVE) and gemcitabine (GEM) on the proliferation, apoptosis and cell cycle of diffuse large B-cell lymphoma (DLBCL) cell line U2932, and further explore the molecular mechanisms, so as to provide new ideas and experimental basis for the clinical treatment of DLBCL. The effect of EVE and GEM on the proliferation of U2932 cells was detected by CCK-8 assay, the IC50 of the two drugs was calculated, and the combination index (CI=) of the two drugs was calculated by CompuSyn software. The effect of EVE and GEM on apoptosis of U2932 cells was detected by flow cytometry with AnnexinV-FITC/PI staining. Flow cytometry with propidium iodide (PI) staining was used to detect the effect of EVE and GEM on the cell cycle of U2932 cells. Western blot assay was used to detect the effects of EVE and GEM on the channel proteins p-mTOR and p-4EBP1, the anti-apoptotic proteins MCL-1 and Survivin, and the cell cycle protein Cyclin D1. Both EVE and GEM could significantly inhitbit the proliferation of U2932 cells in a time- and dose-dependent manner (r=0.465, 0.848; 0.555, 0.796). According to the calculation of CompuSyn software, EVE combined with GEM inhibited the proliferation of U2932 cells at 24, 48 and 72 h with CI=<1, which had a synergistic effect. After treated U2932 cells with 10 nmol/L EVE, 250 nmol/L GEM alone and in combination for 48 h, both EVE and GEM induced apoptosis, and the difference was statistically significant compared with the control group (P<0.05). The apoptosis rate was significantly enhanced after EVE in combination with GEM compared with single-agent (P<0.05). Both EVE and GEM alone and in combination significantly increased the proportion of cells in G1 phase compared with the control group (P<0.05). The proportion of cells in G1 phase was significantly increased when the two drugs were combined (P<0.05). The expression of p-mTOR and effector protein p-4EBP1 was significantly downregulated in the EVE combined with GEM group, the expression of anti-apoptotic proteins MCL-1, Survivin and cell cycle protein cyclin D1 was downregulated too (P<0.05). EVE combined with GEM can synergistically inhibit the proliferation of U2932 cells, and the mechanism may be that they can synergistically induce apoptosis by downregulating the expression of MCL-1 and Survivin proteins and block the cell cycle progression by downregulating the expression of Cyclin D1.