The expression of Ki-S1 and BCL-2 and the response to primary tamoxifen therapy in elderly patients with breast cancer

Ki-S1, a marker of proliferation, and bcl-2, thegene product of which is an antagonist ofapoptosis, have been measured in 51 ER-positive primarybreast cancers before and during tamoxifen treatment andthen related to clinical response. Both markers weredetected in the majority of tumours before treatmentand, quantitatively, initial expression of Bcl-2 protein, butnot Ki-S1, was significantly related to the percentagereduction in tumour volume as assessed by ultrasound.Staining for both markers was lower in posttreatment samples than in those taken prior totreatments, but concordant decreases in staining indices wereseen in only 11 of the 51 tumours.The results demonstrate, using clinical material, that theresponse to tamoxifen may involve changes in proliferationand/or susceptibility to cell-death.