Objectives: To investigate the mechanism of Xuanhusuo powder (XHSP) inhibiting the differentiation of spleen myeloid-derived suppressor cells (MDSCs) in breast cancer mice.
Methods: Forty-eight BALB/c female mice aged 4-5 weeks were selected, 6 of them were in normal control group, while others were in tumor-bearing models established by orthotopic injection of 4T1 cells into the subcutaneous fat pad of the second pair of left mammary glands. The tumor-bearing mice were divided into granulocyte colony stimulating factor (G-CSF) control group, G-CSF knock-down group, model control group, XHSP small dose group, XHSP medium dose group, XHSP high dose group, and cyclophosphamide (CTX) group, with 6 mice in each group. G-CSF control group and G-CSF knock-down group were constructed by stably transfecting 4T1 cells established by shRNA lentivirus combined with puromycin selection. 48 h after the model was established, XHSP small, medium, high dose group were given 2, 4, 8 g·kg－1·d－1 intragastric administration once a day, respectively. CTX was given 30 mg/kg by intraperitoneal injection, once every other day. The other groups were given an equal volume of 0.5% hydroxymethylcellulose sodium. The drugs in each group were continuously administered for 25 d. Histological changes in spleen were observed by HE staining, the proportion of MDSCs subsets in the spleen were detected by flow cytometry, the co-expression of CD11b and Ly6G in the spleen was detected by immunofluorescence, and the concentration of G-CSF in peripheral blood was detected by ELISA. The spleen of tumor-bearing mice was co-cultured with 4T1 stably transfected cell lines in vitro, treated with XHSP (30 μg/mL) for 24 h, and the co-expression of CD11b and Ly6G in the spleen was detected by immunofluorescence. 4T1 cells were treated by XHSP (10, 30, 100 μg/mL) for 12 h. The mRNA level of G-CSF was detected by realtime RT-PCR.
Results: Compared with normal mice, the red pulp of the spleen in tumor-bearing mice was widened with megakaryocyte infiltration. The proportion of spleen polymorphonucleocyte-like MDSCs (PMN-MDSCs) was significantly increased (P<0.01) and the co-expression of CD11b and Ly6G was increased, and the concentration of G-CSF in peripheral blood was significantly increased (P<0.01). However, XHSP could significantly reduce the proportion of PMN-MDSCs (P<0.05) and the co-expression of CD11b and Ly6G in the spleen, down-regulate the mRNA level of G-CSF in 4T1 cells (P<0.01). The concentration of G-CSF in peripheral blood of tumor-bearing mice also decreased (P<0.05) and tumor volume was reduced and splenomegaly was improved (all P<0.05).
Conclusions: XHSP may play an anti-breast cancer role by down-regulating G-CSF, negatively regulating the differentiation of MDSCs, and reconstruct the spleen myeloid microenvironment.
目的: 探讨玄胡索散抑制乳腺癌小鼠脾脏髓源抑制细胞（MDSC）分化的作用机制。方法: 4~5周龄BALB/c雌性小鼠48只，其中6只为正常对照组，其他42只采用小鼠左侧第二对乳腺皮下脂肪垫接种4T1细胞构建乳腺癌荷瘤小鼠模型，分为粒细胞集落刺激因子（G-CSF）对照组、G-CSF敲减组、模型对照组、玄胡索散小剂量组、玄胡索散中剂量组、玄胡索散大剂量组和环磷酰胺组，每组6只。其中G-CSF对照组和G-CSF敲减组分别采用shRNA慢病毒转染联合嘌呤霉素构建相应4T1稳转细胞模型。各组造模48 h后，玄胡索散小剂量组、玄胡索散中剂量组、玄胡索散大剂量组分别按2、4、8 g·kg－1·d－1玄胡索散灌胃，每天一次；环磷酰胺组按30 mg/kg腹腔注射环磷酰胺，隔天一次；其他组给予等体积0.5%羟甲基纤维素纳。各组连续给药25 d。苏木精-伊红染色观察脾脏组织病理学改变，流式细胞术测定脾脏MDSC亚群比例，免疫荧光法检测脾脏CD11b、Ly6G共表达，酶联免疫吸附测定外周血G-CSF浓度。在体外，建立荷瘤小鼠脾脏与4T1稳转株共培养体系，玄胡索散（30 μg/mL）处理24 h，免疫荧光检测脾脏CD11b、Ly6G共表达；不同浓度的玄胡索散（10、30、100 μg/mL）处理4T1细胞12 h，实时逆转录PCR检测G-CSF mRNA水平。结果: 与正常对照组比较，模型鼠脾脏红髓增宽伴巨核细胞浸润，脾脏多形核细胞样MDSC（PMN-MDSC）比例增加（P<0.01），脾脏CD11b、Ly6G共表达增多，外周血G-CSF浓度上升（P<0.01）。玄胡索散干预后脾脏PMN-MDSC比例减小（P<0.05），脾脏CD11b、Ly6G共表达减少，4T1细胞G-CSF mRNA水平下调（P<0.01），模型鼠外周血G-CSF浓度减少（P<0.05），肿瘤体积缩小，脾脏增大情况改善（均P<0.05）。结论: 玄胡索散可能通过下调G-CSF，阻碍MDSC向PMN-MDSC分化，重建脾脏髓系微环境，从而发挥抗乳腺癌作用。.
Keywords: 4T1 cells; Breast cancer; Granulocyte colony stimulating factor; Mice; Myeloid-derived suppressor cells; Spleen; Xuanhusuo powder.