Abstract
Platelet-derived growth factor (PDGF) was partially purified from platelet lysate by isoelectric focusing and gel filtraction. Platelet lysate had three growth promoting factors for a human tumor cell line (K 562) which consisted of acidic (pI 3.1-3.5), neutral (PI 6.5-7.0) and basic (pI 8.8-10.4) substances. The activity of acidic growth factor in platelet lysate was higher than the activities of the other two factors. This acidic factor had a molecular weight of about 30, 000 daltons and was extremely stable to treatments with heat (90°C 10min), alkali or acid, but was inactivated by pepsin digestion.
Growth promoting activity was studied in vivo by means of a biological assay. The intramuscular administration of acidic factor purified by DE 52 chromatography had a marked potentiating effect on the growth of Lewis lung carcinoma in Balb/c mice.
It was, therefore, suggested that not only did PDGF enhance the growth of primaly tumor cells, but also that the PDGF released by platelet aggregation during the process of formation of the tumor thrombus activated the growth of metastatic tumor cells.
