Similarly, to establish that CSF-1 secreted by tumor cells specifically is responsible for the increased trans-endothelial migration, and not the other TMEM doorway cells present in the iTEM assay, we knocked down CSF-1 in MDA-MB-231 cells using siRNA (Supplementary Fig. 3A) and used these tumor cells in the iTEM assay. The gene discussed is CSF1; the disease is neoplasm.