Production of PDGF-like growth factors by embryonal carcinoma cells and binding of PDGF to their endoderm-like differentiated cells

In this report, we demonstrate that F9 and PC-13 embryonal carcinoma (EC) cells do not bind significant amounts of platelet-derived growth factor (PDGF), whereas the endoderm-like differentiated cells derived from EC cells do. The F9-differentiated cells exhibit approximately 8300 receptors per cell, with an apparent dissociation constant of 30 pM. Two endoderm-like cell lines, PSA-5E and PYS-2, also bind PDGF and exhibit approximately 4800 and 23,500 receptors per cell, respectively. The lack of PDGF binding by the parental EC cells is consistent with their release of a factor(s) that is closely related to PDGF. This factor(s) competes with PDGF for binding to membrane receptors and is recognized by antibodies raised against PDGF. However, this factor(s) does not appear to be antigenically identical to PDGF. We also show that production of this PDGF-like factor(s) is reduced more than 90% when F9 EC cells differentiate into cells that bind PDGF. Thus, our findings indicate that EC cells release a factor(s) that should be capable of binding to their differentiated cells. This raises the possibility that PDGF, or a closely related factor, can influence cell proliferation and/or cell behavior of early embryonic cells.