In addition to these cancer-specific gene sets, the F1 and F2 populations were also significantly enriched for TNFα [48], MAPK [49, 50], IL-1 7[51], ErbB [52], HIF- 1[53], RAS [54], RAP 1[55], PI3K-AKT [56], and mTOR [56] signaling pathways, all of which have previously associated with breast cancer metastasis (Fig. 2e). Here, TNF is linked to breast cancer.