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Stimulation of tumor‐cell growth by alpha‐fetoprotein

It has been recognized that alpha‐fetoprotein (AFP), as an oncofetal antigen, is re‐expressed in large amounts in adult tumor cells and serves clinically useful purposes in tumor‐marker assays. However, its biological activities are still undefined. In the present study, the ability of AFP to stimulate tumor‐cell growth was observed by an in vitro experimental system. Mouse ascites cancer cells derived from hepatoma‐22(H‐22) or Ehrlich ascites carcinoma(EAC) were extracted intraperitoneally and cultured in RPMI 1640 medium containing 10% newborn calf serum for 48 hr. Cell growth was quantitated by a colorimetric assay using a MTT microculture tetrazolium dye. The results demonstrated that AFP significantly increased H‐22‐cell proliferation, with stimulation percents of 122 to 156%. A similar growth‐promoting effect of AFP was observed using EAC cells, with stimulation percents of 86 to 210%. Moreover, the growth‐stimulatory activity of AFP could be abrogated with anti‐AFP antibodies. In addition, 5‐fluorouracil could obviously inhibit AFP‐induced proliferation of H‐22 or EAC cells in vitro. These results suggest that AFP is associated with tumor‐cell growth and may serve as an important target of tumor therapy. Int. J. Cancer 75:596–599, 1998. © 1998 Wiley‐Liss, Inc.