OBJECTIVETo study the effects of phytoestrogen alpha-zearalanol (alpha-ZAL) on normal human breast.

METHODSTen specimens of normal human breast tissues were subcutaneously implanted into 30 athymic nude mice aged 9-10 weeks, one for 3 mice. These mice were then randomly divided into three groups: control group (without hormone treatment, n = 10), 1 mg/kg alpha-ZAL group (n = 10), and 5 mg/kg alpha-ZAL group (n = 10). All breast tissues were taken out 6 weeks later. Immunohistochemistry was used to determine the protein expressions of proliferating cell nuclear antigen (PCNA), inhibiting apoptosis gene Bcl-2, estrogen receptor (ER), and progesterone receptor (PR). Reverse transcription polymerase chain reaction (RT-PCR) was used to measure the expression levels of estrogen sulfotransferase (EST) mRNA and bridging integrator protein-1 (BIN1) mRNA. Morphological features of grafts before and after treatment were also observed.

RESULTSAlpha-ZAL had no significant effects on Bcl-2, PCNA, ER, and PR expression of mammary epithelial cells in graft specimens. Alpha-ZAL upregulated BIN1 mRNA expression in grafts, but had no significant effect on ESTmRNA expression.

CONCLUSIONSAlpha-ZAL does not affect the morphology, proliferating, and apoptosis of epithelial cells in normal human breast tissues implanted into nude mice, but it may increase the gene expression of tumor-inhibiting BIN1, suggesting that alpha-ZAL may have potential proteotive effect on normal human breast.