To determine whether migration of 4T1 breast cancer cells toward osteoblasts is affected by PTH1R signaling, primary calvarial osteoblasts were isolated from neonatal mice with a conditional ablation of either PTH1R (PTH1ROsxKO mice) or the Gs α subunit (Gsα) (GsαOsxKO mice) in osteoprogenitors, and cocultured with 4T1 cells in a transwell migration assay system. Here, GNAS is linked to breast cancer.