Anti-alpha-fetoprotein activity of L-4-oxalysine

Effect of L-4-oxalysine (OXL) on the growth stimulatory action and Ts cell induc tion activity of alpha-fetoprotein (AFP) was studied in vitro. When compared with 5-fluorouracil (5-FU), single treatment of OXL presented a weaker cytotoxic activity against mouse ascites hepatoma-22 (H-22) cells. Moreover, lower concentrations of OXL (less than 25 mu g ml(-1)) had no marked antagonistic action on the growth stimulation of H-22 cells by AFP (100 mu g ml(-1)). But, higher concentrations of OXL (25-100 mu g ml(-1)) could significantly abolish the action of AFP. On the other side, when 12.5 mu g ml(-1) of OXL was used in combination with 3.1 mu g ml(-1) of 5-FU, the percentage of suppression on hepatoma growth stimulated by AFP (50 mu g ml(-1)) was increased to 42.8% from 8.3% (OXL alone) or 20.2% (5-FU alone). When 25 mu g ml(-1) of OXL was combined with 6.3 mu g ml(-1) of 5-FU, the inhibition percentage was increased to 63.1% from 35.7% (OXL alone) or 48.8% (5-FU alone). In addition, it was observed by one-way mixed lymphocyte reactions that OXL (12.5 or 50 mu g ml(-1)) produced an inhibitory action on the activity of suppressor T cells induced by AFP (200 mu g ml(-1)).