Drug-induced apoptosis and p53, BCL-2 and BAX expression in breast cancer tissues in vivo and in fibroblast cells in vitro

Abstract

Background: Chemotherapeutic management of breast cancers is a difficult task as they show significant differences in chemosensitivity. The present study was undertaken to determine the usefulness of the apoptosis-related factors as indicators of tumor sensitivity to 5′-deoxyfluorouridine (5′-DFUR) in breast cancers. Methods: (1) Forty-six breast cancer patients were randomly assigned to a group in which oral 5′-DFUR (1200 mg/day) was administered for more than 5 days before operation (24 patients) and a control group who received no preoperative chemotherapy (22 patients). Surgical specimens were examined for the frequency of apoptotic cells [apoptotic index (Al)] by a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling method and for the expression of p53, BCL-2 and BAX by immunohistochemical staining. (2) Normal human diploid fetal lung fibroblast, IMR90 and SV40 transformed IMR90 were exposed to 5-FU. Apoptotic cells were detected by flow cytometry and BCL-2 and BAX mRNAs by real-time quantitative RT-PCR analysis. Results: (1) No significant difference in the Als or in BCL-2 and BAX scores was observed between the 5′-DFUR-treated and control groups. However, in the p53 negative subgroup (n = 36), Al and BAX scores were higher and BCL-2 scores lower in the 5′-DFUR group than in the control group (P = 0.006, 0.008 and 0.050, respectively). (2) The sensitivity of IMR90 was significantly decreased by SV40 transformation and the 5-FU-induced cytotoxicity was mainly due to induction of apoptosis. The BCL-2/BAX mRNA ratio was decreased in response to 5-FU in IMR90. These results correlated with our clinical data. Conclusions: Preoperative treatment with 5′-DFUR induced apoptosis and changes in BCL-2 and BAX expression in p53 negative breast cancers. p53 status, Al and the BCL-2/BAX ratio may be useful information for the choice of postoperative chemotherapy for breast cancer. © 1999 Foundation for Promotion of Cancer Research.