Mechanisms to respond correctly by extracellular signals such as soluble factors and adhesion are provided in multicellular organisms. The mechanisms are the signal transduction system, and its disorder causes various diseases. We examine the roles of signal transduction in cell proliferation, differentiation, migration, and polarization and try to elucidate the pathogenesis of diseases based on their abnormality and to develop new diagnostic and therapeutic devices. In particular, we are currently focusing on Wnt signaling from the perspective of cross-talk between other signaling pathways and exploring novel findings that contributes to life sciences research field.