Effect of trichosanthin an anti-leukemia protein on normal mouse spleen cells.

Trichosanthin, from Trichosanthes kirilowii is a member of the Cucurbitaceae family. It has been reported to have anti-cancer activity. The effects of Trichosanthin peptides (15 amino acids in length) on ConA stimulated incorporation of 3[H] thymidine into cultured, primary mouse spleen cells and L1210 cells were determined. Both spleen cells and L1210 cells were plated at 7.5 x 10(5) cells/ml in a microtiter plate. Different concentrations of the peptide (0.5, 5, 25, and 50 micrograms/ml) and ConA (1 microgram/ml) were added with serum free media, and half of the samples were labeled with 1 microCi/well of 3[H] thymidine. The additional half of the cell samples were used to determine cell number and % viability. After 24 hours incubation, the N-terminal peptides (amino acid residues #1-15 and 16-30) caused increases in ConA stimulated incorporation of 3[H] thymidine into normal spleen cells at low concentrations of the peptides (5 micrograms/ml). The viability of spleen cells and L1210 cells were not affected by these peptides at 5 micrograms/ml. These N-terminal peptides (#1-15 and 16-30) were tested for in vivo anti-tumor activity. There was a delay of tumor formation in the treated vs control group. The results suggest that N-terminal sequences of trichosanthin have anti-tumor activity.