1) The study examines how and why certain breast cancer cells metastasize to bone through a "seed pre-selection" process.
2) It finds that high Src activity (denoted by a "Src activity signature" or SRS) in primary tumors associates with bone metastasis.
3) In ER-/ERBB2- breast cancers, cytokines CXCL12 and IGF1 in the tumor microenvironment activate Src which promotes cell survival and bone metastasis. Long term exposure to these cytokines in vitro selects for breast cancer cells with higher Src activity and bone metastatic ability.