Gj. Zhang et al., CORRELATION BETWEEN THE EXPRESSION OF APOPTOSIS-RELATED BCL-2 AND P53ONCOPROTEINS AND THE CARCINOGENESIS AND PROGRESSION OF BREAST CARCINOMAS, Clinical cancer research, 3(12), 1997, pp. 2329-2335
The proto-oncogene bcl-2, which is implicated in the regulation of cel
l death by inhibiting apoptosis, is reported to be expressed in breast
tissues. The wild-type p53 has been shown to induce apoptosis, which
can be inhibited by bcl-2 expression, However, the role of bcl-2 and p
53 expression in breast carcinogenesis has not been clarified. The pur
pose of this study was to evaluate bcl-2 and p53 expression in normal
breast epithelia cells, as well as in intraductal and invasive cancero
us lesions of breast cancer tissue using an immunohistochemical method
and to clarify their role in the development of breast cancer. The nu
clear accumulation of p53 was also evaluated by quantitative image ana
lysis. Expression of bcl-2 was found in 79 of 82 (96%) normal ductal e
pithelial cells, in 50 of 63 (79%) intraductal carcinomas, and in 62 o
f 137 (45%) invasive carcinomas, respectively. Higher bcl-2 expression
was observed in normal epithelial cells than in intraductal and invas
ive cancerous cells (P < 0.0001). Furthermore, bcl-2 positivity in int
raductal lesions was significantly higher than in invasive cancerous l
esions (P < 0.05). No p53 nuclear accumulation was observed in normal
breast epithelial cells. Fifteen of 63 (23.8%) intraductal cancerous l
esions and 41 of 137 (30%) invasive cancerous lesions were positive fo
r p53 expression. An inverse relationship was shown between bcl-2 and
p53 expression in invasive carcinomas. We demonstrated that bcl-2 expr
ession exists in most of normal ductal epithelial cells and gradually
decreases during the development of breast cancer, i.e., from a normal
epithelium to intraductal carcinoma, and from intraductal to invasive
carcinoma, and that p53 expression may occur early in breast cancer d
evelopment and increases during progression.