In living bodies, there are many cell-cell interactions, including epithelial-mesenchymal interactions, to control cell growth and differentiation, and disturbances to such systems are believed to be a critical reason for many diseases, including cancer. Recently, many growth factors mediating epithelial-mesenchymal interactions have been revealed by molecular biological research. These growth factors are critical tools for both basic research and medical applications. However, obtaining purified forms of such growth factor proteins is difficult. To conveniently analyze the biological effects of such factors on keratinocytes, in this protocol, we describe how to introduce ectopic genes of growth factors of interest (sonic hedgehogandwnt-3genes as examples) into Swiss-3T3 cells, one of the most widely used feeder cells for epithelial cell culture, and how to coculture the keratinocytes with them.
