[Effect of Doxycycline on Intrinsic Apoptosis of Myeloma Cell Line H929 and Its Mechanism].

To investigate the mechanism of the in vitro toxicity of doxycycline to myeloma cell line H929 and also the possible pathway involved its toxicity.Myeloma cell line H929 was treated with DOX, MEK inhibitor U0126 or RAS agonist ML-098, either alone or in combination. Then, the expression of p-MEK, caspase-3, caspase-9 and c-Jun in H929 were used to detected by Western blot; the cells proliferation and apoptosis were detected by CCK-8 assay and flow cytometry, respectively.DOX significantly increased the levels of cleaved caspase-3 and caspase-9, and down-regulated the level of p-MEK in H929 (P<0.05). MEK antagonist U0126 significantly increased the levels of cleaved caspase-3 and caspase-9, and down-regulated the level of p-MEK (P<0.05). After Dox combined with ML-098 treatment of H929 cells, the apoptosis rate of H929 cells was lower than that of DOX alone treatment group(P<0.05). Compared with DOX alone treatment group, the expressions of p-MEK and p-ERK1/2 in DOX+ML-098 combined treatment group were increased, and the levels of cleaved caspase-3,9 in H929 cells were decreased (P<0.05). The levels of c-Jun mRNA and protein increased in H929 when treated by DOX alone (P<0.05).DOX can induce apoptosis of H929 via intrinsic apoptosis pathway, and MEK/ERK pathway and c-Jun possibly play a role in this process.多西环素对骨髓瘤细胞株H929内源性凋亡的影响及其作用机制.探索多西环素（DOX）诱导骨髓瘤H929细胞株凋亡的作用及其可能机制.用DOX、MEK抑制剂U0126和RAS激动剂ML-098单独或联合处理H929细胞，Western blot检测p-MEK、caspase-3、caspase-9、c-Jun等蛋白的表达；CCK8法检测细胞增殖；Annexin-V-FITC/PI双染法检测细胞凋亡.经DOX处理H929细胞后， p-MEK蛋白表达明显减少（P<0.05），伴有caspase-3、9蛋白剪切体的明显增加（P<0.05）。U0126处理H929细胞后，p-MEK蛋白水平明显下降（P<0.05），伴有caspase-3、9蛋白剪切体的明显增加（P<0.05）。DOX联合ML-098处理H929细胞后，H929细胞凋亡比例较DOX单独处理组减少；两药联合处理组p-MEK及p-Erk1/2蛋白表达明显高于DOX单独处理组（P<0.05）， Caspase-3、9蛋白剪切体的水平较DOX单药处理组均明显下降（P<0.05）。DOX处理H929细胞后，c-Jun mRNA和蛋白表达水平均明显增加（P<0.05）.DOX可诱导H929细胞内源性凋亡途径的激活，而MEK/ERK通路及c-Jun可能参与DOX诱导细胞凋亡.