Endocrine-resistant Tumors Research Articles

Incidence of chemotherapy-induced amenorrhea in hormone-sensitive breast cancer patients: the impact of addition of taxanes to anthracycline-based regimens

Adjuvant chemotherapy prolongs survival in patients with breast cancer, but it also causes side effects such as ovarian-function suppression. The incidence of chemotherapy-induced amenorrhea (CIA) varies depending on the patients' age, dose and the type of chemotherapy that they receive. CIA produced by anthracycline-based regimens has been widely studied, but less is known about the incidence of CIA caused by the combined use of taxanes and anthracyclines. It has been suggested that tamoxifen might influence the maintenance of amenorrhea. However, most studies of CIA have explored series of patients with hormone-sensitive and hormone-resistant tumors, so data about CIA could be strongly influenced by endocrine adjuvant therapy. The aims of our study were to assess the incidence of CIA with the addition of taxanes to anthracyclines regimens in pre- or perimenopausal patients diagnosed with hormone-sensitive breast cancer and to determine predictive factors for CIA. A retrospective non-randomized study was conducted in the Hospital Clinico Universitario of Valencia, Spain. Three hundred and five premenopausal and perimenopausal patients were recruited between January 1998 and May 2005, 212 of whom had been treated with anthracycline-based regimens and 93 with a combination of anthracyclines and taxanes. Amenorrhea was permanent in 222 patients (93.7%) and menses returned in 6.3%. CIA was present in 75.5% of patients treated with anthracyclines and in 82.7% of patients treated with anthracyclines and taxanes. This difference did not reach statistical significance (p = 0.16). CIA appeared in 95% of patients older than 45 years, while the proportion of CIA decreased to 52% in patients younger than 40 years. This suggests age as an important predictive factor for CIA (p < 0.001). Although a slightly superior incidence of CIA in patients with hormone-sensitive tumors treated with combination regimens was observed, no statistically significant difference in incidence was found. Age was found to be the main predictive factor for CIA in both groups.

Estrogen-Related Receptor α Expression and Function Is Associated with the Transcriptional Coregulator AIB1 in Breast Carcinoma

The significance of the estrogen-related receptor alpha (ERRalpha) as prognostic marker for poor clinical outcome in breast carcinoma has recently been reported. Transcriptional activity of nuclear receptors such as ERRalpha depends on coregulatory proteins. Thus, we compared the expression of different receptors, coregulators, and target genes on RNA and protein level in identical primary breast tumor samples (n = 48). We found a positive correlation between the transcripts of ERRalpha and AIB1 (amplified in breast cancer-1), a coactivator overexpressed in breast cancers and associated with resistance to antihormone treatment. These data were confirmed on protein level, studying an independent patient collection (n = 257). Expression of the estrogen-regulated gene pS2 was associated with ERRalpha only in tumors, where estrogen receptor (ERalpha) expression was low or absent. In ERalpha high expressing tumors, no correlation of ERRalpha and pS2 was observed. AIB1 interacts directly with ERRalpha as shown by fluorescence-resonance energy transfer, mammalian two-hybrid, and coimmunoprecipitation assays with endogenous proteins. It enhances ERRalpha transcriptional activity in ERalpha-negative breast cancer cell lines as shown in functional reporter gene assays. Blocking ERRalpha with an inverse agonist abolished interaction and coactivation by AIB1. Recruitment of both proteins to ERRalpha target gene promoters further supports the significance of their interaction. Our findings identify AIB1 as functionally relevant cofactor for ERRalpha in breast carcinoma. ERRalpha/AIB1 complexes may control estradiol-regulated genes in a hormone-independent manner. Accordingly, ERRalpha might be a rewarding target for treatment of endocrine-resistant tumors.

Development of Resistance to Targeted Therapies Transforms the Clinically Associated Molecular Profile Subtype of Breast Tumor Xenografts

The effectiveness of therapies targeting specific pathways in breast cancer, such as the estrogen receptor or HER2, is limited because many tumors manifest resistance, either de novo or acquired, during the course of treatment. To investigate molecular mechanisms of resistance, we used two xenograft models of estrogen receptor-positive (ER+) breast cancer, one with and one without HER2 overexpression (MCF7/HER2-18 and MCF7 wt, respectively). Mice with established tumors were assigned to the following treatment groups: estrogen supplementation (E2), estrogen deprivation (ED), ED plus tamoxifen (Tam), all with or without the epidermal growth factor receptor tyrosine kinase inhibitor gefitinib (G). Another group received ED plus the antiestrogen fulvestrant (MCF7 wt only). Tumors with acquired or de novo resistance to these endocrine therapies were profiled for gene expression and compared with tumors in the E2 control group. One class of genes underexpressed in endocrine-resistant tumors (relative to E2-treated tumors) were estrogen inducible in vitro and associated with ER+ human breast cancers (luminal subtype). Another class of genes overexpressed in tumors with acquired resistance in both models represented transcriptional targets of HER2 signaling and was associated with ER-/HER2+ human cancers (ERBB2+ subtype). A third class of genes overexpressed in MCF7/HER2-18 tumors exhibiting de novo resistance to tamoxifen was associated with ER+ human cancers but not with estrogen-regulated genes. Thus, in response to various endocrine therapy regimens, these xenograft breast tumors shut down classic estrogen signaling and activate alternative pathways such as HER2 that contribute to treatment resistance. Over time, the molecular phenotype of breast cancer can change.

Prostate Cancer Cells Increase Androgen Sensitivity by Increase in Nuclear Androgen Receptor and Androgen Receptor Coactivators; A Possible Mechanism of Hormone-Resistance of Prostate Cancer Cells

Although androgen-hypersensitivity is one of the possible pathways of hormone-resistance in prostate cancer, the mechanisms of androgen-hypersensitivity are still largely unknown. Using androgen-hypersensitive prostate cancer cells LN-TR2, established from androgen-sensitive LNCaP cells by the long term treatment with tumor necrosis factor α, we explored the mechanisms of androgen-hypersensitivity in prostate cancer cells which may thus play a role in hormone-resistance. We examined the androgen receptor (AR) DNA sequence and the expression levels of AR and 8 AR cofactors in LNCaP and LN-TR2 cells. As a result, no novel mutation was developed in AR DNA in LN-TR2 cells. We observed higher expressions of nuclear AR upon androgen-treatment and 2 AR coactivators, ARA55 and TIF2, in LN-TR2 compared to LNCaP cells. An overexpression of ARA55 or TIF2 enhanced androgen-induced AR transcriptional activity in LNCaP cell. In the presence of those AR coactivators, AR activity was observed even at low concentrations of androgen. In 2 of 6 patients, the expression level of ARA55 was higher in cancer cells in hormone-resistant tumor than those in hormone-sensitive tumor. Taken together, our results suggest that prostate cancer cells change androgen-sensitivity by an overexpression of nuclear AR and AR coactivators, thus, resulting in transition from androgen-dependent to androgen-independent prostate cancer cells. An increase in nuclear AR and AR coactivators may cause androgen-hypersensitivity of prostate cancer cells and thus play a role in hormone-resistance, at least in some patients with prostate cancer.

Combination therapy with aromatase inhibitors: the next era of breast cancer treatment?

Long-term endocrine therapy with either aromatase inhibitors (AIs) or tamoxifen may lead to endocrine resistance and disease progression. Recent years have seen advances in our understanding of the complex biological mechanisms associated with resistance. Growth factor signaling pathways appear to be upregulated in hormone-resistant tumours and interact with oestrogen-receptor (ER) signaling, which remains functional even after long-term endocrine deprivation. Signaling through the human epidermal and insulin-like growth-factor receptor (HER and IGFR, respectively) pathways may promote ligand-independent ER gene transcription and stimulate growth factor signaling. Therapeutic agents that inhibit these signal transduction pathways, when combined with AIs, may offer breast cancer patients new hope for more robust, longer-term remissions. Preliminary data from phase II studies of combination therapies are encouraging. There is a large programme of ongoing randomised, controlled trials, the results of which should pave the way for integrating combination therapies into clinical practice. To identify which patients will respond best to particular combinations of treatments, biomarkers and gene expression profiles are being investigated as predictors of sensitivity or resistance. In time, breast cancer treatment will become truly individualised because physicians will be able to match patients with a variety of disease phenotypes to optimal combination therapies.

Biological characteristics of the pure antiestrogen fulvestrant: overcoming endocrine resistance.

Understanding the underlying mechanisms responsible for endocrine resistance remains a challenge in improving the treatment of breast cancer. The discovery that growth factor and estrogen receptor (ER) signaling pathways interact in endocrine resistant breast cancer has provided a rationale for disrupting these signaling cascades in ER-positive, endocrine-resistant tumors. In postmenopausal women, the ER signaling pathway may be targeted using fulvestrant ('Faslodex'), a new type of ER antagonist with no agonist effects. Fulvestrant binds, blocks and causes degradation of the ER, culminating in complete abrogation of estrogen-sensitive gene transcription. This unique mechanism of action may result in a lack of cross-resistance with other endocrine agents. Preclinical studies have confirmed the potential of fulvestrant to inhibit the growth of tamoxifen-resistant, as well as tamoxifen-sensitive, human breast cancer cell lines. Clinical studies have demonstrated that fulvestrant is an effective treatment option in postmenopausal women with advanced breast cancer who have progressed on prior endocrine therapy. Furthermore, preclinical studies indicate that combining fulvestrant with growth factor targeted agents, such as the epidermal growth factor receptor (EGFR/HER1) tyrosine kinase inhibitor gefitinib (IRESSA) or the anti-human HER2 monoclonal antibody trastuzumab ('Herceptin'), may result in greater anti-tumor activity than either agent alone. A range of clinical trials are now ongoing to determine whether the combination of growth factor-targeting agents with fulvestrant will delay the onset of endocrine resistance and so provide new strategy for women with hormone receptor-positive advanced breast cancer.

Possible Involvement of Prolactin in Endocrine-Resistant Metastatic Prostate Cancer

The hormone resistance of prostate cancer has been proved to depend at least in part on enhanced neuroendocrine activity and the resultant increase in blood concentrations of chromogranin A. Other experimental observations have suggested the involvement of prolactin (PRL), which appears to be a potential growth factor for prostate cancer. Abnormally high levels of PRL have been detected in metastatic prostate cancer, but the clinical significance of this finding has still to be clarified. In an attempt to explain the prognostic significance of serum PRL levels in prostate cancer, in this preliminary study we have analyzed the PRL levels in a group of metastatic prostate cancer patients with hormone-dependent or hormone-resistant cancer. The study included 50 patients with metastatic prostate cancer, 15 of whom had hormone-resistant tumors. The serum levels of PRL were measured by the RIA method. Abnormally high concentrations of PRL were found in 11/50 (22%) patients. Moreover, the percent of patients with cancer-related hyperprolactinemia was significantly higher in the hormone-resistant group than in the hormone-dependent group (8/15 vs 3/35, p < 0.01). This study confirms the possible existence of a hyperprolactinemic state in metastatic prostate cancer, as previously reported by other authors. Moreover, it appears to demonstrate that the occurrence of hyperprolactinemia is more frequent in hormone-resistant neoplasms, suggesting the possible involvement of PRL in hormone independence. Further studies concomitantly evaluating PRL and chromogranin A blood concentrations will be necessary to establish whether the hyperprolactinemia precedes and promotes the onset of hormone resistance in prostate cancer, or whether it is simply a consequence of the hormone independence.

Possible involvement of prolactin in endocrine-resistant metastatic prostate cancer

The hormone resistance of prostate cancer has been proved to depend at least in part on enhanced neuroendocrine activity and the resultant increase in blood concentrations of chromogranin A. Other experimental observations have suggested the involvement of prolactin (PRL), which appears to be a potential growth factor for prostate cancer. Abnormally high levels of PRL have been detected in metastatic prostate cancer, but the clinical significance of this finding has still to be clarified. In an attempt to explain the prognostic significance of serum PRL levels in prostate cancer, in this preliminary study we have analyzed the PRL levels in a group of metastatic prostate cancer patients with hormone-dependent or hormone-resistant cancer. The study included 50 patients with metastatic prostate cancer, 15 of whom had hormone-resistant tumors. The serum levels of PRL were measured by the RIA method. Abnormally high concentrations of PRL were found in 11/50 (22%) patients. Moreover, the percent of patients with cancer-related hyperprolactinemia was significantly higher in the hormone-resistant group than in the hormone-dependent group (8/15 vs 3/35, p<0.01). This study confirms the possible existence of a hyperprolactinemic state in metastatic prostate cancer, as previously reported by other authors. Moreover, it appears to demonstrate that the occurrence of hyperprolactinemia is more frequent in hormone-resistant neoplasms, suggesting the possible involvement of PRL in hormone independence. Further studies concomitantly evaluating PRL and chromogranin A blood concentrations will be necessary to establish whether the hyperprolactinemia precedes and promotes the onset of hormone resistance in prostate cancer, or whether it is simply a consequence of the hormone independence. (Int J Biol Markers 2005; 20: 123-5).

Androgen receptor gene amplification and protein expression in hormone refractory prostate cancer.

This study examined androgen receptor (AR) gene amplification and protein expression in 102 matched paired hormone sensitive and resistant tumours from 51 patients. AR gene amplification and X chromosome copy number were assessed by fluorescent in situ hybridisation, and protein expression was assessed by immunohistochemistry. All tumours were stained for PSA protein expression. Significantly more tumours exhibited AR amplification following the development of hormone resistance (20%, 10 out of 49) compared to matched hormone-sensitive tumours from the same patient (2%, one out of 48) (P=0.0085). The level of AR expression was significantly higher in hormone-resistant tumours compared to matched hormone-sensitive tumours from the same patient (130, interquartile range, 55–167 vs 94.5 interquartile range, 55–120, P=0.019). AR expression levels in hormone-resistant tumours with and without AR amplification were not significantly different. However, an increase in AR expression was seen with the development of AR amplification in paired tumours. The rate of AR gene amplification and/or an increase in AR protein expression during androgen resistant is too low to wholly explain the development of androgen resistance. Alternative mechanisms for modulating the function of the AR, or other signalling pathways, must be considered as key factors in the development of hormone-resistant prostate.

Human hormone-refractory prostate cancers can harbor mutations in the O(2)-dependent degradation domain of hypoxia inducible factor-1alpha (HIF-1alpha).

Androgen ablation, the preferred therapy for advanced prostate cancer, reduces blood flow and induces hypoxia in androgen-dependent tissues. Given the transient effectiveness of this therapy, we must consider whether a hypoxia-resistance mechanism might be involved in the development of therapeutic resistance by prostate cancer cells. The transcription factor protein, hypoxia-inducible factor 1alpha (HIF-1alpha), helps increase the expression of gene products that enable cells to survive conditions of hypoxic stress. Enhanced HIF-1alpha expression during hypoxia results from a drastic reduction of its degradation rate within a critical region of the protein referred to as the "oxygen-dependent degradation (ODD) domain". We sequenced HIF-1alpha cDNAs amplified from human prostate cancer cell lines and from hormone resistant prostate cancer specimens to determine whether prostate cancer cells might harbor mutations within the HIF-1alpha ODD domain. HIF-1alpha cDNAs were RT-PCR amplified from three prostate cancer cell lines (LNCaP, PC-3, and DU145), from five different human hormone-resistant prostate cancers and one normal prostate, all microdissected, and were sequenced to determine whether the HIF-1alpha gene products were wildtype or mutant. One specimen containing a hormone-resistant prostate tumor that expressed a mutated HIF-1alpha cDNA was further microdissected into benign and tumorous regions and DNAs extracted from these regions were directly amplified by PCR and sequenced to determine whether the HIF-1alpha mutation was specific to the tumor. Although the HIF-1alpha cDNAs of all cell lines, the normal prostate, and three of the tumors were found to have a wildtype sequence, HIF-1alpha cDNAs amplified from two hormone-resistant tumors had nucleic acid substitutions that resulted in significant amino acid changes within the ODD domain of the HIF-1alpha protein. Analysis of the DNA extracted from a benign or tumorous region of one of these specimens showed that only the wildtype (nonmutated) form of the HIF-1alpha gene was amplified from the normal DNA whereas only the mutated form of the HIF-1alpha gene was amplified from the tumor. Some human hormone-refractory prostate cancers have mutations in a critical regulatory domain of the HIF-1alpha protein. We believe that these mutations might enable expression of this protein under inappropriate conditions and contribute to the development of therapeutic resistance by the cancer cells. This hypothesis is currently being tested.

Transdifferentiation of cultured human prostate cancer cells to a neuroendocrine cell phenotype in a hormone-depleted medium

Neuroendocrine (NE) cells are enigmatically found in association with human prostate cancers and their numbers are reported to increase in advanced and hormoneresistant tumors. The origin of this cell type and the reason for their appearance in prostate tumors remains unresolved. Previously, Bang et al. (Proc Natl Acad Sci USA 1994;91:5330) reported that dibutyryl adenosine 3′,5′-cyclic phosphate (db-cAMP), an agent that upregulates intracellular cAMP, was able to induce a NE cell-like phenotype of cultured human prostate cancer cells, including the androgen-sensitive LNCaP line. Here we report that chronic incubation of LNCaP cells in a medium containing 10% charcoal-stripped fetal bovine serum (CSFBS) likewise induces NE differentiation of these cells. Within 5 days of switching low density cultures of LNCaP cells to this modified medium, the cells growth arrest and acquire an altered morphology with numerous cytoplasmic secretory granules and elongated processes that resemble cultured neurons. This morphology predominates at 10 days with complete transformation seen by 20 days of culture. Electron microscopic analysis of sections of CS-FBS maintained cells showed the presence of abundant dense core secretory granules characteristic of NE cells. Immunohistochemical staining identified the upregulation of the expression of NE markers bombesin, neuron-specific enolase, and S-100 in this modified culture medium. Once established, the NE cell-like phenotype was found to be reversible upon replacement with a medium containing unmodified fetal bovine serum, but not by direct supplementation of CS-FBS medium with dihydrotestosterone (DHT) (I nM). DHT supplementation did, however, suppress the development of the NE cell-like phenotype when it was present at the initiation of exposure to CS-FBS medium. In contrast to db-cAMP treatment, which did not affect prostate specific antigen (PSA) or androgen receptor (AR) expression of LNCaP cells, NE-differentiated LNCaP cells derived in this hormone-deficient medium showed marked downregulation of PSA and AR expression. These in vitro results further support the concept that prostate cancer cells can tranform in vivo to cells with a NE phenotype and suggest that this transformation might be accelerated in patients by certain therapies for prostate cancer.

Entropy-based texture analysis of chromatin structure in advanced prostate cancer.

A new texture operator, gray-level entropy matrix (GLEM), was developed, and nine new textural features were extracted from this matrix. These textural features were applied to light microscopy images of nuclei taken from monolayers of advanced prostate cancer cells representing two different prognostic groups: hormone-sensitive (good prognosis) and hormone-resistant (poor prognosis) tumors. A comparison between the classification results obtained from GLEM features and those obtained from standard textural estimators is also discussed. Single features that gave correct classification rates better than 65% were included in a discriminant analysis in order to find the optimal set of features to discriminate between the two prognostic groups in the training data set. The best combination of features includes three GLEM features together with ENTROPY extracted from gray-level cooccurrence matrix, and this combination gave a correct classification rate of 95% using the leaving-one-out technique. The influences of image sharpness and number of cells were also investigated. The features based on entropy or degree of scatter of minute structures can be used to discriminate between hormone-sensitive and hormone-resistant prostate carcinomas.

Entropy‐based texture analysis of chromatin structure in advanced prostate cancer

A new texture operator, gray-level entropy matrix (GLEM), was developed, and nine new textural features were extracted from this matrix. These textural features were applied to light microscopy images of nuclei taken from monolayers of advanced prostate cancer cells representing two different prognostic groups: hormone-sensitive (good prognosis) and hormone-resistant (poor prognosis) tumors. A comparison between the classification results obtained from GLEM features and those obtained from standard textural estimators is also discussed. Single features that gave correct classification rates better than 65% were included in a discriminant analysis in order to find the optimal set of features to discriminate between the two prognostic groups in the training data set. The best combination of features includes three GLEM features together with ENTROPY extracted from gray-level cooccurrence matrix, and this combination gave a correct classification rate of 95% using the leaving-one-out technique. The influences of image sharpness and number of cells were also investigated. The features based on entropy or degree of scatter of minute structures can be used to discriminate between hormone-sensitive and hormone-resistant prostate carcinomas. © 1996 Wiley-Liss, Inc.

TP53 mutations in prostatic cancer. Analysis of pre- and post-treatment archival formalin-fixed tumour tissue.

The TP53 gene mutation pattern in prostatic cancer was examined in relation to progression and survival, using archival formalin-fixed pre- and post-treatment tumour specimens from 84 prostatic cancer patients. Thirty-four had hormone-sensitive tumours and 50 were hormone-resistant. Six of the 34 (18 per cent) therapy-responding tumours and 19 of the 50 (38 per cent) hormone-resistant tumours showed p53 protein accumulation in the post-treatment specimen. Both pre- and post-treatment specimens from these 25 patients were analysed for mutation of the conserved regions of the TP53 gene (exons 5-8), using constant denaturant gel electrophoresis (CDGE) followed by DNA sequencing. In the post-treatment samples, mutations were detected in three of the six patients with hormone-responsive tumours and in 11 of the 19 patients with hormone-resistant tumours. The three (100 per cent) patients with therapy-responsive tumours with mutations and nine of the 11 (82 per cent) patients with therapy-resistant tumours with mutations died of the disease. Thirteen of the 14 mutations in the post-treatment specimens were transitions, 11 occurring at CpG dinucleotides in which codon 273 was involved in ten. A significantly higher proportion of tumours with mutations were poorly differentiated compared with tumours without mutation (P < 0.04). Our findings indicate that TP53 mutation is a late event in tumour development of the prostate gland and that codon 273 might be a 'hotspot' for mutation in the progression of the disease.

Probleme und Prinzipien der Hormontherapie des fortgeschrittenen Prostatakarzinoms

The availability of hormones with few side effects has enlarged the indication for their use: In the presence of metastases, primary endocrine treatment which includes orchiectomy as standard therapy is employed with palliative intent. Adjuvant endocrine treatment is given after radical prostatectomy when positive margins or lymph nodes were present. A salvage endocrine treatment is administered if the primary tumor persists after radiotherapy or recurred after prostatectomy. The term diagnostic hormone treatment is misleading and should not be used. A secondary hormone application is supported by the observation that allaged hormone resistant tumor progressed after testosterone injection. The problem of early versus delayed endocrine therapy is unsolved, however, it is conceivable that the latter therapy is confronted with a larger tumor burden. The principle of endocrine treatment is properly described as means suppressing the androgenic stimuli. There are 5 different routes of androgen deprivation, among which the antiandrogens and LH RH analogs have the highest priority. Phase III-studies are under way to clarify their efficacy.

Advanced breast cancer: response to high dose oral medroxyprogesterone acetate.

We treated 105 patients with advanced breast cancer, using the progestational agent medroxyprogesterone acetate (MPA), 200 mg orally tds in a non-randomised trial. In general they were a poor risk population, since 78 had received prior endocrine therapy (21 more than one type) and 58 prior chemotherapy. Treatment was well tolerated. Side effects included weight gain, muscle cramps, fine tremor and fluid retention, but these were usually mild, resolved if the dose of drug was reduced, and only one patient stopped treatment because of toxicity. Seventeen patients died within six weeks of starting MPA, and disease progression occurred in a further 58. Nine have had stable disease for periods ranging from two to 11 months, and there were 21 who showed disease regression. Response to treatment continues in 13 of these patients, and at the time of writing the median duration of response is 10 months. Response rates were similar in pre- and post-menopausal patients. The dose of MPA was double to 400 mg tds in 16 patients whose disease had progressed on 200 mg tds, but no additional responses were seen in this group. Seven out of 24 (29%) patients who had not received prior endocrine therapy responded to high dose oral MPA, a response rate similar to that seen following other hormonal manipulations, but because the drug also has activity against hormone-resistant tumours and is well tolerated, it should have role in the treatment of advanced breast cancer.

DNA binding ability of estrogen receptor from human breast cancer

DNA binding ability of estrogen receptors (ER) from human breast cancers was examined and clearly demonstrated in 51 of 55 ER positive tumors by using a DNA cellulose slurry. The percentages of ER bound to fixed amounts of DNA varied widely, but the average was lower than that of rat uterine ER. Preheating of ER at 25°C caused increased DNA binding ability in some tumors but significant loss of this ability in other tumors. Mixing rat uterine cytosol with cytosols from 2 tumors, including an endocrine-resistant cancer which showed no DNA binding activity of ER, destroyed DNA binding ability of uterine ER with a minor effect on estradiol binding capacities even at low temperature. Exposure of the tumor cytosol to 56°C for 30 min or dialysis of the tumor cytosol, however, reduced this inhibitory activity. This cytoplasmic factor in the tumor was also found to cleave rat uterine ER into a smaller fragment (3–4S) either in a high salt or in a low salt sucrose density gradient, especially at a relatively high temperature. A significant amount of DNA binding of ER and its enhancement by preheating were observed in all 8 endocrine-responsive tumors, while no DNA binding of ER or temperature-induced decrease in DNA binding ability was observed in 5 of 6 ER positive but endocrine-resistant tumors, suggesting clinical importance of this cytoplasmic factor in the tumor.

Adrenal suppression in the treatment of carcinoma of the prostate.

SummaryExperience of 26 patients with carcinoma of the prostate treated by adrenal suppression with aminoglutethimide is reviewed. 60% of hormone resistant tumours showed some response.A fall in plasma testosterone beyond that achieved by oestrogens was not observed.A high incidence of side‐effects was noted.A limited role for aminoglutethimide in the management of prostatic carcinoma is suggested.Our thanks are due to the Consultant Surgeons, St Peter's Hospitals who referred their cases to us for investigation. We acknowledge with thanks the help of Dr I. F. Sommerville and Mr M. D. Mansfield, Department of Clinical Endocrinology, Chelsea Hospital for Women, who performed testosterone assays. Aminoglutethimide was supplied by Ciba Laboratories Ltd, Horsham, Sussex. This work was supported by a grant from the St Peter's Research Trust.