Given the pronounced neutrophilia associated with tumour progression in the MMTV-PyMT model of mammary cancer (Fig. EV2F), and the positive correlation between circulating neutrophil counts and metastatic burden in these mice (Fig. EV2G), we assessed Upp1 expression in neutrophils from MMTV-PyMT mice bearing mammary tumours. The gene discussed is UPP1; the disease is breast cancer.