Our results showed that breast osteoblast-like cells were able to induce, through the release of biochemical factors into the culture medium, the osteoblastic trans-differentiation of co-cultured breast cancer cells in 2D cell culture systems, leading to a decrease in their proliferation and migration, as evidenced by the down-regulation of p-ERK2 and cyclin D1 expression. The gene discussed is MAPK1; the disease is breast cancer.