The invention provides novel polynucleotides and polypeptides encoded by such polynucleotides and mutants or variants thereof that correspond to a novel human secreted stem cell growth factor-like polypeptide. These polynucleotides comprise nucleic acid sequences isolated from cDNA libraries prepared from human fetal liver spleen, ovary, adult brain, lung tumor, spinal cord, cervix, ovary, endothelial cells, umbilical cord, lymphocyte, lung fibroblast, fetal brain, and testis. Other aspects of the invention include vectors containing processes for producing novel human secreted stem cell growth factor-like polypeptides, and antibodies specific for such polypeptides.