Pre-metastatic expression array day 7

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. To follow the earliest transcriptional changes in pre-metastatic tissues, we orthotopically injected 4T1 cells into the mammary fat pad of female nude mice. Control mice were orthotopically injected with PBS. 7 days post tumor engraftment, the mice were sacrificed and thoroughly perfused with ice cold PBS, and lung and liver samples were flash frozen in liquid nitrogen. Following RNA extraction, the lung and liver RNA samples were analyzed on MOE430A2 Affymetrix arrays using R/Bioconductor software.