The effects of anti-estrogen therapy on lymphocyte functions in breast cancer patients.

The effects of anti-estrogen therapy (tamoxifen or toremifene) on in vitro lymphocyte functions were investigated in breast cancer patients. We found that the amount of DNA synthesis, with or without PWM stimulation, was decreased in all cancer patient groups compared to normal controls. The number of Ig-secreting cells was enhanced in unstimulated peripheral blood lymphocyte cultures but decreased in PWM-stimulated cultures. This occurred in all cancer patient groups investigated, with or without anti-estrogen therapy, as compared to healthy controls. On the other hand, subsequent samples with two-month intervals showed that anti-estrogens can increase PFC responses and inhibit DNA synthesis of peripheral blood lymphocytes in more than half of the patients. Interestingly, the enhancing dexamethasone effect, which usually causes an increase in the number of Ig-secreting cells in PWM-stimulated cultures, was also seen more often in anti-estrogen-treated patients. These results suggest that anti-estrogens may have immunoregulatory effects in vivo.