AKT1 and breast cancer: Moreover, the activation of protein kinase B (AKT)/mammalian target of rapamycin complex 1 (mTORC1) signaling within luminal breast cancer cells, which were in direct contact with osteoblasts at the “pre-metastatic niche”, promoted osteoblast-induced breast cancer proliferation and the progression to macrometastases, leading to a transition from a pre-osteolytic phase to an osteolytic phase.