VARIATION OF HORMONAL RECEPTOR, PS2, C-ERBB-2 AND GST-PI CONTENTS IN BREAST CARCINOMAS UNDER TAMOXIFEN - A STUDY OF 74 CASES

Seventy-four post-menopausal patients with primary non-metastatic inva sive ductal carcinomas of the breast were first treated with tamoxifen alone (30 mg p.o. daily) for 5 months. To study changes induced by ta moxifen, core biopsies before treatment and surgical specimens after h ormonal therapy were assayed by immunohistochemistry for oestrogen (ER ) and progesterone receptors (PR), pS2, GST pi and c-erbB-2. After tam oxifen, ER and PR significantly decreased in 60 and 44 cases respectiv ely, whereas 11 and 19 cases showed no variation and 2 and 11 cases sh owed an increase (P<10(-4). GST pi and pS2 showed a significant increa se in 43 and 41 cases, a decrease in 2 and 21 cases and no variation i n 29 and 12 cases (P<10(-4) and P=0.04 respectively). c-erbB-2 showed no significant variation under tamoxifen, increased in only three case s and decreased in 13 cases. No relation was found between these varia tions and efficiency of hormone therapy. Our results allow a better kn owledge of protein expression modifications occurring in breast cancer cells under tamoxifen therapy. They are also more consistent with clo ne selection rather than with phenotype modification.