Interestingly, unlike LPS, which upregulates a wide variety of proinflammatory genes in macrophages via Toll-like receptor (TLR) 4, GM-CSF upregulated the expression of a unique set of genes, including CCL2 and CCL7, suggesting that cancer cell-derived GM-CSF plays a critical role in the progression of 4T1 BC by inducing the production of CCL2 by TAMs. Here, CCL2 is linked to cancer.