THYMOSTIMULIN INCREASES NATURAL CYTOTOXIC ACTIVITY IN PATIENTS WITH BREAST-CANCER

The effect of thymostimulin on the Natural Killer (NK) cytotoxic activ ity of peripheral blood mononuclear cells (PBMC) was investigated in 1 5 patients with breast cancer after finishing or during chemotherapy ( CAF) and in 10 healthy controls. PBMC from these subjects were incubat ed in the presence of thymostimulin for varying periods of time (18 h or 5 days), and then used as effector cells against Cr-51-radiolabeled NK-sensitive (K-562) and NK-resistant (JY) target cells in cytotoxici ty assays. No significant differences were observed between the NK-act ivity from breast cancer patients and healthy controls. Thymostimulin induced a dose-and time-dependent cytotoxic enhancing effect on the cy totoxic activity of PBMC from these patients against NK-sensitive K562 target cells. The thymostimulin (1000 ng/ml) significantly enhanced c ytotoxic activity in PBMC from breast cancer patients who had previous ly received chemotherapy (p=0.0277) against NK-sensitive cells. This i ncrease was not statistically significant neither in PBMC from patient s receiving chemotherapy nor in healthy controls (p > 0.05 in both cas es). The incubation of PBMC from patients with breast cancer was not a ssociated to a significant enhancement of the cytotoxic activity again st NK-resistant target cells (p > 0.05). We also found that thymostimu lin could synergize with interleukin-2 in inducing NK cytotoxic activi ty in PBMC after 18 h of culture (p=0.0277). In conclusion, we have de monstrated that thymostimulin enhances the natural killer cytotoxic ac tivity of PBMC from patients with breast cancer who have previously re ceived chemotherapy. (C) 1997 International Society for Immunopharmaco logy.