Expression of Bcl-2 in node-negative breast cancer is associated with various prognostic factors, but does not predict response to one course of perioperative chemotherapy

Abstract

Summary The aim of this study was to assess relationships between Bcl-2 expression, response to chemotherapy and a number of pathological and biological tumour parameters in premenopausal, lymph node-negative breast cancer patients. Expression of Bcl-2 was determined using immunohistochemistry on paraffin-embedded sections in a series of 441 premenopausal, lymph node-negative breast cancers of patients randomised to receive perioperative chemotherapy (5-fluorouracil, doxorubicin, cyclophosphamide) or no perioperative chemotherapy. Immunohistochemistry of Bcl-2 was evaluated by scoring both staining intensity (0-3) and number of positive cells (0-2). Using these scores tumours were grouped into categories 0-6. It was found that 9.2% of the tumours were completely negative (0), 17.2% weakly (1 + 2), 41.6% moderately (3 + 4) and 31.9% strongly positive (5+6) for Bcl-2. A positive correlation was found between high Bcl-2 expression and oestrogen (P<0.001) and progesterone receptor positivity (P<0.001) and low tumour grade (P<0.001), whereas high Bcl-2 expression was negatively correlated with p53 (P<0.001) and c-erb-B-2 positivity (P<0.001), high Ki-67 index (P<0.001), mitotic index (P<0.001) and large tumour size (P=0.006). Patients with tumours expressing high levels of Bcl-2 (overall score 3-6) had a significantly better disease-free (P=0.004) and overall (P=0.009) survival. However, in a multivariate model this association no longer remained significant. There was a trend for an effect of adjuvant chemotherapy on disease-free survival both for patients with Bcl-2-positive (HR-0.61, 95% CI 0.35-1.06, P=0.07) and negative (HR=0.55, 95% CI 0.27-1.12, P=0.09) breast tumours at a median follow-up of 49 months. The level of Bcl-2 expression does not seem to predict response to perioperative chemotherapy in premenopausal, lymph node-negative breast cancer patients. High levels of Bcl-2 are preferentially expressed in well-differentiated tumours and are associated with favourable prognosis. However, Bcl-2 expression is not an independent prognostic factor in this patient series.

Genetic factors influencing Pyrimidine-antagonist chemotherapy

“…The most extensively studied genes with regard to pyrimidine antagonist chemotherapy are bcl-2, bax, c-myc and p53. [160][161][162][163][164][165][166][167][168] Here, we will only briefly report on the putative role of p53 with respect to 5-FU efficacy, as this relationship has been most extensively studied. Mutations in the p53 gene and p53 overexpression have been associated with 5-FU chemoresistance both in vitro [169][170][171] and in vivo in colorectal, 124,[172][173][174][175] head and neck, 176,177 and breast cancer.…”

Loss of Bcl-2 in invasive breast cancer is associated with high rates of cell death, but also with increased proliferative activity

“…From a series of 441 node-negative, premenopausal breast cancer patients, previously analysed for Bcl-2 immunostaining (van Slooten et al, 1996), a subset of 49 tumours (including 41 ductal carcinomas) was selected, in which Bcl-2 was either absent (n = 23) or strongly stained (n = 26). Apart from Bcl-2, various prognostic factors (including p53, ER, Ki-67, mitotic index) have been analysed previously (Clahsen et al, 1997).…”

“…The median (0.77%) was used as a cutoff value for apoptotic index, whereas for necrosis the cut-off was none vs low, intermediate and high. Bax and Bcl-XL expression were scored using the scoring system previously described for Bcl-2 (van Slooten et al, 1996). Bax-negative tumours and Bcl-X -negative tumours were defined as those tumours with a staining score of 3 and 2 respectively.…”

“…Staining was visualized using diaminobenzidine (Sigma, St Louis, MO, USA). Depending on the antibody, sections were scored either semiquantitatively (Bcl-2, p53, ER) or quantitatively (Ki-67) as described previously (Clahsen et al, 1997;van Slooten et al, 1996). The mitotic index was determined by counting the number of mitosis per ten high-power fields in H&E sections.…”

“…We wanted to test this in our series of tumours from 441 node-negative, premenopausal breast cancer patients, previously analysed for Bcl-2 immunostaining (van Slooten et al, 1996). However, apoptosis is a difficult variable to adequately quantitate in tissue sections.…”