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). Here, EGF is linked to skin basal cell carcinoma.