Progesterone receptor determination in human breast tumors by immunocytochemical and biochemical techniques

int-2 oncogene amplification and prognosis in node-negative breast carcinoma

The role of int-2 oncogene amplification on the prognosis of breast cancer patients was investigated in 128 patients with node-negative primary breast cancers given first-line local-regional treatments until relapse and with a median follow-up of 65 months. Tumours had been previously characterised for oestrogen (ER) and progesterone receptor (PgR) status and proliferative activity (3H-thymidine labelling index). Amplification of the int-2 oncogene occurred in 18% of cases and was significantly related to the presence of hormone receptors and to menopausal status or age, but not to proliferative status. Patients with tumours exhibiting int-2 amplification had a lower probability of disease-free survival than patients with non-amplified tumours and frequently developed local-regional recurrence. Disease-free survival analysis, adjusted for the prognostic contribution provided by tumour size, steroid receptors and proliferative rate, indicated that the association between int-2 amplification and risk of relapse was maintained and remained constant even in the presence of the other co-variates. Interestingly, int-2 amplification was a further prognostic discriminant within subsets of patients with a putatively good (i.e., tumour size <20 mm, ER+ and PgR+) or poor prognosis (i.e., high labelling index). Our exploratory study suggests that within node-negative patients, int-2 amplification could be a valuable and independent prognosticator, useful to identify patients at high risk of local-regional recurrence.

Prognostic relevance of pS2 status in association with steroid receptor status and proliferative activity in node-negative breast cancer

Expression of the oestrogen-regulated pS2 protein was investigated on paraffin-embedded sections of primary breast tumours from 200 node-negative patients. Immunoreactivity was observed in 56% of the cases. pS2 expression was inversely correlated with tumour size and proliferative activity, whereas a direct correlation was observed with steroid receptor. 5-year relapse free survival was influenced by tumour size (P = 0.02), oestrogen receptor status (P less than 0.05), and proliferative activity (P less than 0.01). No difference in relapse-free survival was observed between patients subdivided according to pS2 expression alone. However, among patients with oestrogen-receptor-negative tumors, pS2 expression predicted a shorter relapse-free survival.

Epitope mapping of the anti-human progesterone receptor monoclonal antibody, AB-52

The monoclonal antibody AB-52 has high affinity and specificity for the two natural human progesterone receptor forms, receptor A (hPRA) and receptor B (hPRB), but it does not bind the PR of chick, mice, rats or rabbits. We have used a novel method to map its epitope. Based on a series of site-directed mutants of hPRA, together with immunoblotting, DNA gel mobility shift and antibody super shift assays, we have mapped the epitope of AB-52 to a 17 amino acid sequence lying between Val221 and Leu237 of the 933 amino acid hPRB protein. This N-terminal sequence is common to both hPRB and hPRA but is missing in chick PR and differs extensively from mouse PR. No anti-rabbit PR antibodies map to the homologous rabbit PR sequence which differs from hPR by four amino acids, suggesting that one or more of these four amino acids form a critical subset of residues in hPR that define the human specificity of AB-52. Knowledge of the AB-52 epitope is useful in structural analysis of PR, and in competition studies. Additionally, this 17 amino acid peptide whose antigenicity would not be predicted from computer analysis, should be useful for generating additional hPR specific antibodies.

An immunohistochemical evaluation of progesterone receptor in frozen sections, paraffin sections, and cytologic imprints of breast carcinomas

Two monoclonal antibodies to progesterone receptor (PR), JZB39 and KD68, were used for the immunocytochemical visualization of PR in different kinds of breast cancer specimens including (1) cryostat sections of tumors frozen at -80 degrees C; (2) paraffin sections of tumors fixed in formalin or in Bouin's fixative for varying periods of time at room temperature or at 4 degrees C; and (3) imprints and cryostat sections prepared from the tissue used for frozen section diagnosis and stored at -80 degrees C after fixation in Zamboni's solution. Sections of conventionally frozen specimens as well as imprints and cryostat sections stored for varying periods of time were stained with the peroxidase-antiperoxidase technique, whereas the avidin-biotin technique was used for paraffin sections. In all types of specimens the PR immunostaining was localized to the nuclei of carcinoma cells and displayed considerable heterogeneity both in intensity and in distribution of positive cells. Close correspondence was found between the different immunohistochemical techniques as well as between immunostaining and steroid-binding assays. PR staining was more frequently positive in well-differentiated than in moderately or poorly differentiated carcinomas, whereas no meaningful correlation was found between PR staining and extent of the disease. Similar results were obtained with the immunostaining of estrogen receptor in the same material using monoclonal antibodies H222 and D75P3 gamma. Thus, by choosing the technique that best suits the type of specimen available, it is possible to obtain valid information on the receptor status of any breast carcinoma, regardless of its size and clinical presentation.

Influence of culture conditions on the estrogenic cell growth stimulation of human breast cancer cells

17 beta-Estradiol is a potent mitogen for hormone-dependent cell lines (MCF-7, T47D and ZR 75.1). However, the degree of hormone sensitivity is very much influenced by culture conditions. In order to understand which factors modulate estrogenic effects on cell growth, four different culture conditions were used: (a) medium with dextran-coated charcoal-treated fetal calf serum (DCC-FCS); (b) medium with dextran-coated charcoal-treated growth factor-inactivated serum (DCC-FCSd); (c) serum-free medium, after a 24-h incubation with serum to allow cell attachment; and (d) serum-free medium on collagen IV-treated plates. In all cell lines the highest cell growth stimulation was achieved when estradiol was added in the presence of 5% DCC-FCS, whereas reducing or removing serum from the culture medium resulted in a decrease in cell proliferation stimulation. We postulate that serum contains some still unknown components able to modulate the degree of estrogenic action in endocrine-dependent breast cancer cell lines.