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

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.

The potential role of leptin in tumor invasion and metastasis

“…Fascinatingly, TAMs have been considered as M2 macrophages, which could promote the EMT [145–147]. A recent study has shown that leptin may promote breast cancer progression by stimulating M2 macrophages [148]. Using a different approach Strong et al [11] co-cultured adipose stromal/stem cells isolated from obese women with either ER+ MCF-7, ZR75, or T47D human breast cancer cells, which resulted in enhanced expression of EMT and metastasis related genes, SERPINE1, MMP-2, and IL-6.…”

“…Some of the well-studied signaling pathways/molecules include: MAPK/ERK, PI3K/AKT, STAT, TGF-β, and Wnt/β-Catenin [205]. Fascinatingly, many of these molecules are linked with the signal transduction pathways of leptin (Table 4 [14,108,109,113,118,120,129,142,144,148,152,153,206–222]).…”

“…On the other hand, evidence suggests that obesity can favor M2 polarization [228,229]. Furthermore, leptin has been shown to influence M2 macrophages [148,230]. Nonetheless, macrophages are highly specialized cells having character of plasticity/adaptability in diverse microenvironments.…”

Leptin Signaling Contributes to Aromatase Inhibitor Resistant Breast Cancer Cell Growth and Activation of Macrophages

“…It is well known that inflammation is involved in almost all tumor processes. Notably, leptin, in addition to its direct effects on breast cancer epithelial cells, has been demonstrated to stimulate the function of macrophages, one of the most abundant and critical immune cell types within the breast tumor microenvironment [22,[50][51][52]. Thus, we investigated whether an enhanced production of leptin from AnaR cells may impact the macrophage phenotype to support malignant progression further.…”

Leptin-LepRb Expressed in Gastric Cancer Patients and Related to Cancer-Related Depression

“…Its tumorigenic action is mediated by JAK/STAT, PI3K/PTEN/Akt/mTOR, Raf/MER/ERK pathways [20, 21]. Serum leptin has been detected in various cancers with conflicting results.…”