CXCR4 sustains proliferation through direct activation of MAPK, PI3K, Wnt, and HH1 signaling (343), where HH additionally induces SDF1 expression in the tumor surrounding (344) and activation of the intrinsic anti-apoptotic pathway via ERK and Akt1 (344, 345). The gene discussed is AKT1; the disease is neoplasm.