Herein is described a cell density signaling protein and its tissue-specific lipid cofactor. Constructs, compositions and methods for isolation, purification and use of the protein and the tissue-specific lipid cofactor are described.
STATEMENT OF GOVERNMENTAL SUPPORT
 This invention was made with government support under Contract No. DE-AC02-05CH11231 awarded by the U.S. Department of Energy, and Grant No. CA064786 awarded by the National Institutes of Health. The government has certain rights in the invention.