DIRECT TUMOR-GROWTH SUPPRESSIVE EFFECT OF MELANOIDIN EXTRACTED FROM IMMUNOMODULATOR-PSK

Melanoidin, which belongs to the melanin group of molecules, was extra cted from the polysaccharide biological response modifier PSK. Melanoi din was cultured together with HCT-15 cells derived from om human colo n cancer and with AGS cells derived from om human gastric carcinoma. A fter four days of culture, cell count was compared with that of the co ntrol cells. Significant suppression was observed, that is, 50% suppre ssion was shown at concentrations of melanoidin between 200 and 100 mu g/ml. A histogram generated by flow cytometry showed elevation of the tetraploid peak and of that between diploid and tetraploid peaks, sug gesting blockage of S phase and G2 to M phase of the cell cycle. Thus, melanoidins contained in the immunomodulator PSK revealed to have a d irect tumor cell growth inhibitory effect.