IN-VITRO REACTIVITY TO A PROTEIN-BOUND POLYSACCHARIDE PSK OF PERIPHERAL-BLOOD LYMPHOCYTES FROM PATIENTS WITH GASTROINTESTINAL CANCER

The effect of PSK, a protein-bound polysaccharide and an immunomodulat or, on lymphocytes was examined in vitro for 36 patients with gastric cancer and 26 with colorectal cancer. Cultured lymphocytes with PSK at 100 mu g/ml increased the level of DNA synthesis, as determined by th e H-3-thymidine uptake, from 0.9 to 3.0 fold, compared to the PSK non- treated cells. The increase was 1.36 +/- 0.46 fold for the gastric can cer cases and 1.37 + 0.45 fold for the colorectal cancer cases, and th ese levels were significantly the finding of 1.93 + 0.55 fold for a co ntrol group consisting of 15 healthy volunteers (P<0.01). When the 1.3 fold increase of H-3-thymidine uptake was defined as the PSK-reactive group, 52.8% (19/36) of the patients with gastric cancer and 50.0% (1 3/26) for colorectal cancer were found in the PSK-reactive group. The PSK-reactive group demonstrated no relation to the age and sex of the patients, tissue differentiation type or tumor advancement. Our findin gs thus show that the in vitro activation of lymphocytes by PSK can he lp identify the candidates with either gastric or colorectal cancer wh o are the best suited to undergo immunochemotherapy including treatmen t with PSK.