( Department of Biochemistry, Hainan Medical College, Haikou 571101, China; ¹Department of Biochemistry and Molecular Biology, Health Science Center, Peking University, Beijing 100083, China )

Abstract

A lot of investigations showed that alpha-fetoprotein(AFP) could regu late the proliferation of tumors or neoplastic cells. In order to study the enhancement of this function, AFP was extracted from human cord blood serum and was allowed to act on HeLa cell in vitro. The cellular proliferation was investigated by using the MTT assay and the [³H]-incorporation, and the cell c ycle was analy sed with flow cytometry. Radioactive immunosorbent assay was utilized to detect cAMP accumulation, protein kinase A activity and confocal microscopy was used f or scanning intracellular calcium. The expression of mutant p53 and p21^ras protein were analyzed by Western blotting. Our results showed that AFP (>10 mg/L ) had strong effect of enhancement on the proliferation of HeLa cells; AFP (20 mg /L) could significantly increase the concentration of cAMP (300%), Ca²⁺ (154.9%) and protein kinase A activity (100%). It was also shown that the expression of mutant p53 and p21^ras protein of HeLa cells were enhanced after t he treatment with AFP (20 mg/L) for 24 hours. Compared with control, the expres sion of mutant p53 protein was increased by 81.1% (24 h), p21^ras pro tein was increased by 96.2% (24 h) respectively; but the monoclonal antibody to AFP blocked these functions of AFP. In conclusion, AFP enhanced the prolif eration of HeLa cells; AFP may regulate the growth of the cells by influencing the transmembrane signal pathway and enhancing the expression of the oncogenes.