MAPK1 and skin basal cell carcinoma: Growth factors coupled to tyrosine kinase-containing membrane receptors (e.g., EGF, IGF-1, prolactin, the heregulin family, insulin, and TGF-α and TGF-β) serve as major regulators of ERK.49 Our results show that pERK1/2+ osteoblasts can induce BCC growth, enabling these BCCs to adapt to the bone microenvironment through the release of inflammatory cytokines and growth factors (Fig. S4).