- A heparin-binding growth factor secreted from breast cancer cells homologous to a developmentally regulated cytokine. Wellstein, A., Fang, W.J., Khatri, A., Lu, Y., Swain, S.S., Dickson, R.B., Sasse, J., Riegel, A.T., Lippman, M.E. J. Biol. Chem. (1992)