Construction of a sensitive enzyme immunoassay for human fibroblast growth factor 9

Hybridomas secreting monoclonal antibodies (MAbs) against human fibroblast growth factor 9 (FGF-9) were established using recombinant human (rh) FGF-9 N33 as the immunogen. Among these, MAb 150-59 demonstrated a potent neutralizing activity against FGF-9. It arrested the FGF-9-induced growth of BALB/c 3T3 A31 cells at an equimolar dose of the factor. It also abrogated the in vivo thrombopoietic activity of FGF-9. Mitogenic activity of several other FGF family members such as FGF-1, FGF-2, and FGF-4 was not neutralized by this MAb. A sensitive sandwich enzyme immunoassay for FGF-9 was developed employing MAbs 150-59 and 13-3. The detection limit of this system was 3 pg/well. In this assay system, FGF-1 and FGF-2 were not cross-reactive up to 1 microgram/well. Using this system, the distribution of FGF-9 in rat organs was examined. FGF-9 could be detected only in the extract of rat cerebellum. Also, we detected a high amount of FGF-9 in the culture supernatant of certain cell lines originated from human tumor. These findings suggest that this enzyme immunoassay system may be used to clarify biological meaning of FGF-9.