The effects of the administration of tamoxifen, ethynyloestradiol, and prednisolone on the activities of certain enzymes of carbohydrate metabolism in primary human breast carcinomas in vivo.

Postmenopausal patients with primary breast cancer were treated with tamoxifen, ethynyloestradiol or prednisolone for up to 12 days before mastectomy and the effects of pretreatments with these drugs on the activities of phosphofructokinase (PFK), 6-phosphogluconate dehydrogenase (6PGDH) and alpha-glycerolphosphate dehydrogenase (alpha-GPDH) in the carcinomas were compared with age, stage and menopausal status matched untreated controls. The administration of tamoxifen or prednisolone resulted in a significant increase in the activity of alpha-GPDH and the alpha-GPDH/6PGDH ratio, whereas ethynyl-oestradiol treatment produced a significant decrease in the activity of the enzyme and the ratio. When tamoxifen and ethynyl-oestradiol were administered together, it was found that tamoxifen failed to reverse the oestrogen-induced reduction in the activity of alpha-GPDH. Since increased activity of the enzyme or a higher alpha-GPDH/6PGDH ratio are associated with a lower risk of recurrence (Deshpande et al., 1981), it is postulated that the beneficial effects of tamoxifen or prednisolone in terms of prolongation of the relapse free interval might be mediated via alterations in the activity of alpha-GPDH in micrometastases. The activities of PFK and 6PGDH remained unaffected by these treatments.