NF-κB and neutrophil extracellular traps cooperate to promote breast cancer progression and metastasis

Highlights: • Cancer cells–derived factors, such as IL-8 and G-CSF, induce NETs formation via PAD4 and NF-κB. • NETs increase the interaction of NEMO with IKKα/β and enhance NF-κB activation. • Blockade of NETs using PAD4 inhibitor decreases NF-κB and tumor metastasis. • Selective inhibition of NF-κB reduces NETs formation and tumor growth and metastasis. Aberrant NF-κB activation and neutrophil extracellular traps (NETs) are associated with breast cancer progression. How NF-κB and NETs modulate each other in breast cancer development remains unclear. Here, we found that NETs induced by phorbol 12-myristate 13-acetate promote breast cancer cell progression. In turn, cancer cells–derived factors, such as IL-8 and granulocyte colony-stimulating factor, stimulate neutrophils to form NETs. Mechanistically, NETs increased the interaction of NF-κB essential modifier (NEMO) with IκB kinase (IKK)α/β and enhanced NF-κB activation. We then employed a cell-permeable peptide corresponding to the NEMO-binding domain (NBD) of IKKα/β, termed NBD peptide, which disrupts NETs-mediated NEMO interaction with IKKα/β and abolished NF-κB activation in vitro. NBD peptide also reduced IL-8 level and NETs formation, and suppressed primary tumor growth and/or lung metastasis in human breast cancer mouse xenograft models and mouse spontaneous breast cancer model. Blockade of NET formation using a peptidylarginine deiminase 4 (PAD4) pharmacologic inhibitor decreased NF-κB activation and tumor metastasis. Collectively, these data suggest that NF-κB associates with NETs to form a positive loop facilitating breast tumor progression and metastasis, and that selective inhibition of NF-κB and PAD4-dependent NETs provides an effective therapeutic approach for treating breast cancer.