Leptin promotes migration and invasion of breast cancer cells by stimulating IL-8 production in M2 macrophages

// Hong Cao 1, * , Yunxiu Huang 1, * , Lin Wang 1 , Hong Wang 1 , Xueli Pang 1 , Kuangfa Li 1 , Weiqi Dang 1 , Hao Tang 1 , Lan Wei 1 , Min Su 1 , Cuiping Tang 1 , Tingmei Chen 1 1 Department of Laboratory Medicine, Key Laboratory of Diagnostic Medicine, Ministry of Education Chongqing Medical University, Chongqing, China * These authors contributed equally to this work Correspondence to: Tingmei Chen, email: chentingmei@sohu.com Keywords: breast cancer, IL-8, invasion, leptin, migration Received: January 31, 2016 Accepted: August 13, 2016 Published: August 31, 2016 ABSTRACT This study aims to investigate the mechanisms underlying leptin-mediated crosstalk between tumor-associated macrophages (M2 macrophages) and breast cancer cells. THP1 human leukemic monocytes were induced to differentiate into M2 macrophages by PMA (100 nM) and IL-4 (20 ng/mL). Quantitative RT-PCR and Western blot revealed that leptin (100 nM) significantly increased the expression of leptin receptor (ObR) in the M2 macrophages ( P < 0.01) and stimulated interleukin (IL)-8 expression in the M2 macrophages, mouse macrophage cells RAW264.7, and primary mouse peritoneal macrophages in a dose- and time-dependent manner. Leptin-induced IL-8 production was sensitive to the ERK inhibitor PD980590 (10 μmol/L), p38 MAPK inhibitor SB203580 (20 μmol/L), and anti-ObR neutralizing antibody (4 μg/mL). Leptin (100 ng/mL) substantially increased the phosphorylation of p38 and ERK1/2. Thus, leptin may induce IL-8 production in M2 macrophages by interacting with ObR to activate the p38 and ERK signaling pathways. Scratch and transwell chamber assay showed that both recombinant IL-8 and leptin-induced M2 macrophage-derived IL-8 promoted the migration and invasion of human breast cancer cells MCF7 and MDA-MB-231 (All P < 0.01). In a nude mice xenograft model of breast cancer ( n = 5 per group), injection of leptin (0.1 μg/g) dramatically increased tumor volume and mass, reduced survival, exacerbated pulmonary metastasis, and elevated IL-8 and Ki67 expression in the tumor tissue (All P < 0.05) compared with PBS injection. Depletion of mouse macrophage by Clophosome ® -clodronate liposome and injection of anti-mouse IL-8 neutralizing antibodies in the xenograft tumor significantly attenuated those leptin-mediated stimulations (All P < 0.05). These findings indicate that leptin may promote tumor growth and metastasis by stimulating IL-8 production in tumor-associated macrophage.