Neutrophil expression array

Primary tumors have been shown to prepare distal organs for later colonization of metastatic cells by stimulating organ-specific infiltration of bone marrow-derived cells. Here we demonstrate that neutrophils accumulate in the lung prior to the arrival of metastatic cells in mouse models of breast cancer. Tumor-entrained neutrophils (TENs) inhibit metastatic seeding in the lungs by generating H2O2, and tumor-secreted CCL2 is a critical mediator of optimal anti-metastatic entrainment of G-CSF-stimulated neutrophils. TENs are present in the peripheral blood of breast cancer patients prior to surgical resection but not in healthy individuals. Thus, while tumor-secreted factors contribute to tumor progression at the primary site, they concomitantly induce a neutrophil-mediated inhibitory process at the metastatic site. This experiment was designed to compare the RNA expression profile in resting (control) neutrophils vs. that of TENs (neutrophils purified from tumor-bearing mice). In addition, we also compared the expression profiles of cultured neutrophils in vitro and treated with CCL2, CCL5 and GCSF. Circulating neutrophils were purified from control and 4T1 tumor-bearing mice and flash frozen. For in vitro cultures, circulating neutrophils were purified from control mice, cultured in the presence of chemokines for 2 hours and flash frozen.