David L. Manning

Epidermal growth factor receptor expression in breast cancer: association with response to endocrine therapy.

Summary106 previously untreated breast cancer patients have been immunohistochemically analysed for EGF-R, ER, Ki67, and c-erbB-2 product. All patients received assessable endocrine therapy following disease progression. Significant associations were observed between EGF-R and ER (inverse) and Ki67 (direct). No association was observed between EGF-R and the c-erbB-2 product. EGF-R expression was significantly associated with the loss of endocrine sensitivity in breast cancer. This was observed in both ER positive and negative disease. In ER positive breast cancers, EGF-R expression had no significant influence on the quality of tumour remissions. Further sub-classification of the ER/EGF-R data by Ki67 immunostaining showed that in ER+/EGF-R- disease, increasing proportions of Ki67 positive cells were associated with a decline in the numbers of women experiencing good quality tumour remissions. A similar trend was also observed in ER+/EGF-R+ tumours. The presence of c-erbB-2 protein product did not influence endocrine sensitivity in any of the ER/EGF-R sub-groups.

Oestrogen-regulated genes in breast cancer: Association of pLIV1 with lymph node involvement

In order to isolate markers of oestrogen responsiveness in breast cancer, we have cloned a number of oestrogen-regulated genes. Two of these, pLIV1 and pLIV2 (pS2), have been shown to be predominantly expressed in oestrogen receptor (ER)+ tumours. In this study, we examined their expression in relation to various clinical and histopathological features of breast cancer, and showed that pLIV1, but not pS2, is significantly associated with lymph node involvement (P < 0.01), while pS2 is more frequently observed in premenopausal patients (P < 0.05). Subdivision of the pLIV1 data by ER and nodal status of the tumour identified a highly significant association between pLIV1 expression and lymph node involvement in ER-positive disease, with 15/24 (63%) ER+ pLIV1+ tumours showing nodal involvement. Conversely, 20/23 (87%) ER+ pLIV1- patients were lymph node-negative (P < 0.001). Subdivision of the pS2 data by ER status did not reach significance. The application of pLIV1 as a marker of lymph node involvement was further exemplified in small tumours (< < 2 cm), where 11/12 (92%) lymph node-positive patients expressed pLIV1, while 17/22 (77%) node-negative patients were pLIV1 negative (P < 0.001). Similarly, pLIV1 expression identified lymph node involvement in moderately differentiated tumours (P < 0.01), but was independent of vascular invasion. pLIV1 may, therefore, represent a candidate gene for metastatic spread in ER+ breast cancer.

Responses to Pure Antiestrogens (ICI 164384, ICI182780) in Estrogen-Sensitive and-Resistant Experimental and Clinical Breast Cancer

The last ten years has seen the emergence of a new class of pharmacological agents termed pure antiestrogens (reviewed in Refs. 1, 2). These compounds, which were originally discovered by ICI Pharmaceuticals Division (now Zeneca Pharmaceuticals) in the UK, have the unique property of binding to the estrogen receptor (ER),3 producing a receptor complex which lacks estrogenic a~tivity.4.~ They are of use in two important areas of breast cancer research. Firstly, as clinical agents, where it is hoped that their ability to induce total estrogen deprivation will improve the effectiveness of endocrine therapy. Secondly, as pharmacological probes to investigate the cellular and molecular actions of estrogens and tamoxifen. Inherent in each of these areas of research are questions associated with the impact pure antiestrogens may have on the therapy of endocrine-resistant states and whether resistance develops as a consequence of incomplete estrogen withdrawal; with tumor cells more efficiently utilizing either a reduced estrogenic pool or the agonistic activity of an antiestrogen,

Effects of short-term antiestrogen treatment of primary breast cancer on estrogen receptor mRNA and protein expression and on estrogen-regulated genes

SummaryEffects of the pure antiestrogen ICI182780 and tamoxifen on ER-protein, ER-mRNA, and estrogen-regulated mRNA expression were analysed using matched pretreatment core-cut biopsies and post-treatment mastectomy samples from 43 ER positive human breast cancers. Sixteen controls received either no preoperative treatment (n = 9) (7 days) or placebo (n = 7) (median 21 days) prior to primary surgery. Nineteen patients received ICI182780 6 mg/day (n = 10) or 18 mg/day (n = 9) for 7 days. Eight patients were given preoperative tamoxifen (4 × 40 mg-day 1, 20 mg/day thereafter, median 21 days). ER-protein expression was assessed on pre and post treatment samples by immunocytochemistry. ER, pS2, pLIV1, and actin-mRNA expression was determined by northern analysis on post-treatment samples only. ER-mRNA levels were similar to controls following ICI182780 or tamoxifen treatment. However ER-protein levels were significantly suppressed by ICI182780, particularly at the higher dosage (p = 0.0013). Tamoxifen had no significant effect on ER-protein levels. The ER-mRNA and ER-protein contents of control tumors were linearly related (Spearman r = 0.719, p = 0.006). A similar relationship between pretreatment protein and post ICI182780 treatment mRNA levels was observed (r = 0.652, p = 0.005). However, comparison of post ICI182780 treatment protein and mRNA results shows a loss of linearity through a reduction in protein without concurrent loss of mRNA (r = 0.28, p = 0.257). pS2 mRNA hybridization was lower in ICI182780 treated samples than controls (Mann-Whitney p = 0.035) but was unaffected by tamoxifen. pLIV1 mRNA hybridization was uninfluenced by either treatment. Short term exposure of breast tumors to ICI182780 appears to produce a greater inhibition of estrogen-induced transcriptional events than tamoxifen. These effects appear to occur without a concurrent reduction in ER mRNA levels.

Differential expression of oestrogen regulated genes in breast cancer.

Pathological endpoints such as tumour size, lymph node status and vascular invasion remain the most useful guides in selecting treatment strategies for breast cancer. There is a need, however, to further investigate the molecular mechanisms that determine the properties of an individual tumour e.g., hormone responsiveness and probability of metastasis. While numerous prognostic factors have now been identified few have contributed to defining clinical response to therapy. Oestrogen-regulated genes are likely to be important since they not only define a functional oestrogen receptor, but alterations in their expression might provide insights into the mechanisms involved in tumour progression and loss of endocrine sensitivity. Recently an oestrogen responsive gene, pLIV1, has been isolated and shown to be expressed in ER+ disease where it appears to predict nodal involvement. The present paper describes aspects of its regulation and discusses the potential role of this and other genes in the development of endocrine resistance.

The role of four oestrogen-responsive genes, pLIV1, pS2, pSYD3 and pSYD8, in predicting responsiveness to endocrine therapy in primary breast cancer

The expression of four oestrogen-responsive genes in 118 immunohistochemically defined primary breast tumours has been determined by northern analysis. While all the genes are induced by oestrogen in oestrogen receptor (ER)-positive cell lines, their behaviour is different in breast tumour biopsies. This behaviour can be divided into two groups; the first containing the genes, pLIV1 and pLIV2 (pS2), which both show a significant association with ER status (P = 0.001) and a corresponding inverse relationship with epidermal growth factor receptors (EGFR) (P = 0.01 and P = 0.08, respectively). In addition, the mRNA levels of both pLIV1 and pS2 are greater in ER-positive compared to ER-negative disease (P = 0.001). While a small number of ER-negative tumours were positive for either pLIV1 (12%) or pS2 (9%), we failed to observe co-expression of pLIV1 and pS2 in ER-negative disease. In ER-positive disease, four tumour populations were identified; ER+pLIV1-pS2-, ER+pLIV1-pS2+, ER+pLIV1+pS2- and ER+pLIV1+pS2+. Interestingly, the levels of pLIV1 and pS2 when co-expressed were significantly greater in ER+pLIV1+pS2+ tumours compared to either of the ER+pLIV1+pS2- (P = 0.03) or ER+pLIV1-pS2+ (P = 0.01) mixed phenotypes. Unlike pLIV1 and pS2, pSYD3 and pSYD8 belong to a group of genes which are expressed in the majority of tumours regardless of ER and EGFR status. However, lower pSYD8 mRNA levels were detected in moderately EGFR-positive disease (P = 0.06) while both pSYD3 positivity (P = 0.01) and mRNA levels (P = 0.001) were increased in highly proliferating tumours as shown by Ki67 immunostaining. These genes provide additional markers which, in conjunction with other parameters, may help to determine the likelihood of a given tumour to respond to endocrine therapy.

Oestrogen-regulated genes in breast cancer: association of pLIV1 with response to endocrine therapy.

Northern hybridization analyses of the oestrogen-inducible mRNAs pLIV1 and pS2 were compared with oestrogen receptor (ER) immunocytochemistry assessments in 40 untreated primary or early recurrent breast tumours. Significant associations were observed between pLIV1/ER (P < 0.03), pS2/ER (P < 0.001) and pLIV1/pS2 (P < 0.04) status. After disease recurrence, patients were treated with assessable courses of endocrine therapies. Positive pLIV1, pS2 and ER statuses in primary disease were consequently found to be predictive of endocrine responsiveness in the secondary lesions (P < 0.03, P < 0.02, P < 0.005 respectively). However, despite these associations, a number of pLIV1- and/or pS2-positive tumours failed to respond to therapy.

Isolation of pMGT1: a gene that is repressed by oestrogen and increased by antioestrogens and antiprogestins.

In order to isolate additional markers of oestrogen responsiveness in breast cancer and to study the mechanisms associated with the development of endocrine resistance, we have searched for oestrogen regulated genes. Differential hybridisation analysis of a cDNA library prepared from oestrogen-stimulated T-47D cells has led to the isolation of a sequence (pMGT1) whose expression is repressed (up to 8-fold) by oestrogen (10(-9) mol/l) and represents the first down-regulated gene to be identified by this methodology. Further studies of pMGT1 expression in MCF-7 cells has revealed that the pure antioestrogens, ICI164384 (10(-7) mol/l) and ICI182780 (10(-7) mol/l) and the antiprogestin Ru38486 (10(-7) mol/l), increase pMGT1 mRNA levels by approximately 40-50-fold relative to the value seen in cells exposed to oestrogens. Under the same conditions, pS2(pLIV2), a gene which is positively regulated by oestradiol, was almost undetectable. Significantly, both tamoxifen (10(-7) mol/l), and 4-hydroxytamoxifen (10(-7) mol/l), failed to increase pMGT1 mRNA levels. Since cell culture studies have indicated that ICI164384 and ICI182780 are more effective than tamoxifen and 4-hydroxytamoxifen at inhibiting the growth of MCF-7 cells by mechanisms that lower their viability and sensitivity to growth factors, it is feasible that pMGT1 plays a central role in mediating these events and instigating pathways associated with cell death.