The role for a substantially purified human growth factor preparation is shown to contain a distinct polypeptide with apparent M.sub.r on SDS/PAGE of about 220 kD, and to be distinct from bFGF, with a most active fraction at about 220 kD. A human growth factor polypeptide of 157 kD was identified, in human bone marrow aspirates and from bone stromal cells, by immunoblotting with the mAb MS 329, and by affinity isolation using a MS 329 antibody column. A PSA stimulating autocrine factor, PSAF, that is precipitable in ammonium sulfate at between 60-80% saturation is able to induce PSA expression and secretion, and serves as an indicator of androgen independent prostate cell growth.