Effect of cationic amino acid, L-lysine and its polymers on the growth andsecretion of hybridoma cell line OKT-3

Apart from their pivotal roles in anabolic protein synthesis, cationic amin o acids, particularly, L-lysine HCl and its oligomers, up to molecular weig ht 1000, showed a remarkable property of cellular growth stimulation both i n vitro and in vivo. L- and D-Lysine HCl, at a maximal stimulatory concentr ation of 7 mu g/mL of added load of the amino acid, supported a characteris tic time-scaled cellular expansion ill vitro, and L-lysine-mediated cell ex pansion in batch cultures always showed a stimulation index (S.I.) ranging up to similar to 35, compared with the matched control populations. Variabl e S.I. was possibly due to factors such as seeding density, type of media a dditives, number of passages the cells have undergone before being stimulat ed, etc. Beyond and before maximal stimulatory concentration of the amino a cid, there is a sharp decline in the cellular growth-promoting activity of monomeric L-lysine HCl in vitro, thereby showing a clear concentration wind ow for maximum cellular growth promotion. While the essential amino acid do es not have any dedicated cell surface receptor, the monomeric and oligomer ic amino acid molecule(s) possibly mediates the serum-derived growth factor -receptor binding on the cell membrane by having two cationic charge centre s at two ends of the molecule. Beyond a cutoff molecular weight of 1000, ol igomeric lysines did not show any positive effects on either cell division and secretion.