Signaling pathways influencing SLF and c-Kit-mediated survival and proliferation

Steel factor (SLF) and c-Kit are a ligand-receptor pair that regulates growth and activation of a variety of hemopoietic and non-hemopoietic cells. This review describes our work investigating downstream signaling pathways activated by SLF, with particular emphasis on signaling differences associated with soluble vs membrane-bound ligand, and our identification of an important role for PLC activation and Ca2+ influx in supporting c-Kit positive cells in vitro and in vivo. This work led to the identification of a unique form of cell death termed activation enhanced cell death (AECD) that involves stimulating a cell with a growth or activation signal while concurrently blocking Ca2+ influx. Approaches that we have taken toward identifying cellular factors associated with sensitivity and resistance to AECD are summarized, as is our experience with a variety of experimental models. The use of econazole as a calcium channel blocker and its mechanism of action are described, as is its potential for development as an anticancer therapeutic.