Considering that tumour-associated neutrophils were found to be major producers of MMP-9 in tumour tissues (Deryugina et al., 2014) and F. nucleatum translocates to breast tissues, colonises them and plays a role in breast cancer metastasis (Guo et al., 2024), the influence of F. nucleatum-stimulated MMP-9 release by neutrophils should not be overlooked in future cancer studies. The gene discussed is MMP9; the disease is breast cancer.