Researchers from Brazil, England and the United States have identified a new biochemical pathway that regulates cell proliferation and the development of tumors. They have discovered that in mice that carry a prostate tumor implant the protein CRKL, generally found inside mammal cells,it also appears in the extra-cell environment, where it causes neighboring cells to divide. This is an unusual way of controlling cell proliferation. Until now, proteins from the intracellular communication system linked to cancer that act in transmitting chemical signals between tumorous cells were unknown. It is still not known how CRKL ends up outside the cells. But there are two hypotheses: the protein is secreted by the live cell or liberated after the cell dies, suggest the researchers in an article in the Proceedings of the National Academy of Sciences (PNAS). While the work is coordinated by Wadih Arap and Renata Pasqualini, from the University of Texas, Marco Arap, from USP, and Ricardo Brentani, from the A. C. Camargo Hospital, have both been involved in it.