Signaling as an overall cellular process is a prerequisite for the life of normal and cancer cells and is regulated by a multiplicity of mechanisms including "cross-talks" among pathways. Cross-talk is often critical in determining the decision of a cell to go toward a specific biological direction, such as proliferation, apoptosis, or differentiation. Both signaling pathways and cross-talk among them involve such biochemical processes as protein-to-protein interactions and well-regulated phosphorylation and dephosphorylation processes. This symposium was focused on mechanisms of the regulation of signaling with special emphasis on regulatory cross-talk among pathways and on changes that occur in cancer cells. The phenomena discussed were also considered with reference to opportunities that may be offered toward the development of potential therapeutic intervention.