[Salidroside induces anti-tumor effect in dendritic cells via ERK pathway]

Objective To investigate the role of mitogen activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway in the salidroside (SAL)-regulated antitumor immunity of dendritic cells (DCs). Methods Lewis lung cancer-bearing mouse model was established and treated with normal saline (NS) (0.2 mL/d), SAL [500 mg/(kg.d)] and cyclophosphamide (CTX) [10 mg/(kg.d)] in corresponding groups. Then their survival and tumor quality were recorded. Meanwhile, the bone marrow-derived DCs from the Lewis lung cancer-bearing mice were isolated in vitro and cultured for 7 days before collection. After sorted with magnetic beads, cells were co-cultured with PBS, SAL (0.05 mg/mL), LPS (200 ng/mL) or SAL combined with ERK inhibitor U0126 separately for 48 hours, followed by detection of the expression of phosphorylated ERK (p-ERK) by flow cytometry. In addition, after the stimulation of DCs by SAL, the expression of p38 MAPK and phosphorylated c-jun N-terminal kinase (p-JNK) was detected by flow cytometry. Moreover, after sorted with magneticbeads, DCs were co-cultured with PBS, SAL (0.05 mg/mL), LPS (200 ng/mL) or SAL combined with U0126. Then, the supernatant was collected, and IL-12p70 secretion ability of DCs was detected by ELISA. Finally, sensitized bone marrow-derived DCs from Lewis lung cancer-bearing mice were stimulated with SAL and co-cultured with spleen T lymphocytes purified by nylon fiber column from C57BL/6 mice as effector cells. 3LL target cells were then added at the target ratio of 10:1, 25:1, 50:1, followed by the detection of cell viability of cytotoxic T lymphocytes (CTLs) using CCK-8 assay. Results SAL could significantly inhibit tumor growth and improve the survival rate. Compared with PBS group, the phosphorylation of ERK protein on DC was enhanced significantly, and then reduced significantly after U0126 treatment. The phosphorylation of p38MAPK and c-jun N-terminal kinase (JNK) protein was not statistically affected by SAL. The level of IL-12p70 significantly increased in SAL group, and became remarkably higher after U0126 treatment. Finally, the killing ability of CTL was significantly enhanced by SAL. Conclusion SAL can inhibit the tumor growth of Lewis lung cancer-bearing mice and activate the ERK signaling pathway, thereby promoting IL-12p70 secretion in DCs and enhancing the cytotoxicity of CTL.