ZEB1 Defines the Interaction Between Breast Cancer Cells and Macrophages by Upregulating the Expression of CCL2 Cytokine

The survival of disseminating tumor cells at the invasive edge and in metastatic foci depends on their ability to counteract anti-tumor immunity. The epithelial–mesenchymal transition (EMT) process is associated with the recruitment of immune-suppressive myeloid cells. The onset of the EMT gene expression program is controlled by several transcriptional master-regulators, including ZEB1. Using engineered breast cancer cell lines with different statuses of ZEB1, we examined the effects of ZEB1 on the expression of different pro-inflammatory cytokines. Our results suggest that ZEB1 plays an important role in regulating the expression of CCL2 (C-C motif ligand 2, a.k.a. MCP-1), the main chemoattractant of monocytes. Forced expression of ZEB1 in epithelial MCF-7 cells significantly increased the expression level of CCL2, which was further enhanced by TNF-α. On the contrary, knock-out of ZEB1 in pseudo-mesenchymal MDA-MB-231 cells led to a complete loss of CCL2 expression. Moreover, this effect was not restored by TNF-α induction. Also, positive ZEB1 status in breast cancer cells promoted the chemoattraction of THP-1 macrophages in co-culture experiments. Analysis of publicly available ChIP-seq data implicated ZEB1 in the regulation of CCL2 gene transcription. Taken together, these data suggest that ZEB1 is involved in the formation of the EMT-associated pro-tumor immune microenvironment.