Consensus statement. Workshop on therapeutic resistance in breast cancer: impact of growth factor signalling pathways and implications for future treatment.

Anti-hormones (notably tamoxifen), chemotherapy and modern radiotherapeutic approaches are invaluable in the management of breast cancer, and collectively have contributed substantially to the improved survival in this disease. Moreover, there is promise that these successes will continue with the emergence of other endocrine agents (for example, aromatase inhibitors and pure anti-oestrogens). However, de novo and acquired resistance comprises a significant problem with all treatment approaches examined to date. This Workshop aimed to evaluate the contribution made by growth factor signalling pathways in the various resistant states, primarily focusing on resistance to anti-hormonal strategies and spanning experimental models and, where possible, clinical breast cancer data. The successes and limitations of therapeutic targeting of these pathways with various signal transduction inhibitors (STIs) were evaluated in model systems and from emerging clinical trials (including epidermal growth factor receptor inhibitors such as gefitinib). It was concluded that growth factor signalling is an important contributor in the development of endocrine resistance in breast cancer and that use of STIs provides a promising therapeutic strategy for this disease. However, the cancer cell is clearly able to harness alternative growth factor signalling pathways for growth and cell survival in the presence of STI monotherapy and, as a consequence, the efficacy of STIs is likely to be limited by the acquisition of resistance. A number of strategies were proposed from studies in model systems that appeared to enhance anti-tumour actions of existing STI monotherapy, notably including combination therapies targeting multiple pathways. With the increased availability of diverse STIs and improved drug delivery, there is much hope that the more complex therapeutic strategies proposed may ultimately be achievable in clinical practice.

Inhibitors of growth factor signalling.

The therapeutic utility of trastuzumab ('Herceptin') in breast cancer patients with tumours that overexpress erbB2 established the principle that targeted inhibition of specific signal transduction pathways can provide a new approach to cancer treatment. The ErbB family of protein tyrosine kinases, in particular the epidermal growth factor receptor (EGFR), are commonly overexpressed in many solid human tumours and EGFR was the initial target for a drug discovery programme seeking small molecule inhibitors of the EGFR tyrosine kinase (TK) enzyme activity. The description of the anilinoquinazoline class of potent and selective TK inhibitors led to several candidate drugs from this chemical class, for example gefitinib ('Iressa') and erlotinib ('Tarceva'), which are being evaluated in breast cancer patients. Rapid advances in cancer molecular genetics have identified numerous potential drug targets associated with abnormal control of cell division either downstream of the ErbBs, for example Ras and MEK, or in erbB-associated signalling networks, like Src kinase, which affect the tumour cell motility and invasiveness. Candidate drugs for several of these targets are currently being evaluated; for example, the prenylation inhibitor AZD3409, a mimetic of the CAAX box of K-Ras, inhibits protein farnesyl and geranylgeranyl tranferases and a novel, selective, orally active Src kinase inhibitor AZD0530 have entered Phase I clinical trials and may have utility in breast cancer therapy.

Insulin-like growth factor-I receptor signalling and acquired resistance to gefitinib (ZD1839; Iressa) in human breast and prostate cancer cells.

De novo and acquired resistance to the anti-tumour drug gefitinib (ZD1839; Iressa), a specific epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) has been reported. We have determined whether signalling through the IGF-I receptor (IGF-1R) pathway plays a role in the gefitinib-acquired resistance phenotype. Continuous exposure of EGFR-positive MCF-7-derived tamoxifen resistant breast cancer cells (TAM-R) to 1 microM gefitinib resulted in a sustained growth inhibition (90%) for 4 months before the surviving cells resumed proliferation. A stable gefitinib-resistant subline (TAM/TKI-R) was established after a further 2 months and this showed no detectable basal phosphorylated EGFR activity. Compared with the parental TAM-R cells, the TAM/ TKI-R cells demonstrated (a) elevated levels of activated IGF-1R, AKT and protein kinase C (PKC)delta, (b) an increased sensitivity to growth inhibition by the IGF-1R TKI AG1024 and (c) an increased migratory capacity that was reduced by AG1024 treatment. Similarly, the EGFR-positive androgen-independent human prostate cancer cell line DU145 was also continuously challenged with 1 microM gefitinib and, although substantial growth inhibition (60%) was seen initially, a gefitinib-resistant variant (DU145/TKI-R) developed after 3 months. Like their breast cancer counterparts, the DU145/TKI-R cells showed increases in the levels of components of the IGF-1R signalling pathway and an elevated sensitivity to growth inhibition by AG1024 compared with the parent DU145 cell line. Additionally, DU145/TKI-R cell migration was also decreased by this inhibitor. We have therefore concluded that in breast and prostate cancer cells acquired resistance to gefitinib is associated with increased signalling via the IGF-1R pathway, which also plays a role in the invasive capacity of the gefitinib-resistant phenotype.

Fulvestrant: an oestrogen receptor antagonist with a novel mechanism of action.

Due to their favourable tolerability profiles, endocrine therapies have long been considered the treatment of choice for hormone-sensitive metastatic breast cancer. However, the oestrogen agonist effects of the available selective oestrogen receptor modulators, such as tamoxifen, and the development of cross-resistance between endocrine therapies with similar modes of action have led to the need for new treatments that act through different mechanisms. Fulvestrant ('Faslodex') is the first of a new type of endocrine treatment--an oestrogen receptor (ER) antagonist that downregulates the ER and has no agonist effects. This article provides an overview of the current understanding of ER signalling and illustrates the unique mode of action of fulvestrant. Preclinical and clinical study data are presented in support of the novel mechanism of action of this new type of ER antagonist.

The antiepidermal growth factor receptor agent gefitinib (ZD1839/Iressa) improves antihormone response and prevents development of resistance in breast cancer in vitro.

Although many estrogen receptor-positive breast cancers initially respond to antihormones, responses are commonly incomplete with resistance ultimately emerging. Delineation of signaling mechanisms underlying these phenomena would allow development of therapies to improve antihormone response and compromise resistance. This in vitro investigation in MCF-7 breast cancer cells examines whether epidermal growth factor receptor (EGFR) signaling limits antiproliferative and proapoptotic activity of antihormones and ultimately supports development of resistance. It addresses whether the anti-EGFR agent gefitinib (ZD1839/Iressa; TKI: 1 mum) combined with the antihormones 4-hydroxytamoxifen (TAM: 0.1 mum) or fulvestrant (Faslodex; 0.1 mum) enhances growth inhibition and prevents resistance. TAM significantly suppressed MCF-7 growth over wk 2-5, reducing proliferation detected by immunocytochemistry and fluorescence-activated cell sorter cell cycle analysis. A modest apoptotic increase was observed by fluorescence-activated cell sorter and fluorescence microscopy, with incomplete bcl-2 suppression. EGFR induction occurred during TAM response, as measured by immunocytochemistry and Western blotting, with EGFR-positive, highly proliferative resistant growth subsequently emerging. Although TKI alone was ineffective on growth, TAM plus TKI cotreatment exhibited superior antigrowth activity vs. TAM, with no viable cells by wk 12. Cotreatment was more effective in inhibiting proliferation, promoting apoptosis, and eliminating bcl-2. Cotreatment blocked EGFR induction, markedly depleted ERK1/2 MAPK and protein kinase B phosphorylation, and prevented emergence of EGFR-positive resistance. Faslodex plus TKI cotreatment was also a superior antitumor strategy. Thus, increased EGFR evolves during treatment with antihormones, limiting their efficacy and promoting resistance. Gefitinib addition to antihormonal therapy could prove more effective in treating estrogen receptor-positive breast cancer and may combat development of resistance.

Modulation of epidermal growth factor receptor in endocrine-resistant, estrogen-receptor-positive breast cancer.

An increasing body of evidence demonstrates that growth factor networks are highly interactive with estrogen receptor signaling in the control of breast cancer growth. As such, tumor responses to antihormones are likely to be a composite of the estrogen receptor and growth factor inhibitory activity of these agents. The modulation of growth factor networks during endocrine response is examined, and in vitro and clinical evidence is presented that epidermal growth factor receptor signaling, maintained in either an estrogen receptor-dependent or a receptor-independent manner, is critical to antihormone-resistant breast cancer cell growth. The considerable potential of the epidermal growth factor receptor-selective tyrosine kinase inhibitor Iressa (ZD 1839) to efficiently treat, and perhaps even prevent, endocrine-resistant breast cancer is highlighted.

Fulvestrant ('Faslodex')--a new treatment option for patients progressing on prior endocrine therapy.

Since its introduction more than 30 years ago, tamoxifen has been the most widely used endocrine therapy for the treatment of women with advanced breast cancer. More recently, a number of alternative endocrine treatments have been developed, including several selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs) and, most recently, fulvestrant ('Faslodex'). Fulvestrant is an estrogen receptor (ER) antagonist, which, unlike the SERMs, has no known agonist (estrogenic) effect and downregulates the ER protein. Tamoxifen is effective and well tolerated, although the non-steroidal AIs, anastrozole and letrozole, are more effective treatments for advanced disease than tamoxifen. Fulvestrant has recently gained US Food and Drug Administration approval for the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression following antiestrogen therapy. In two global phase III clinical trials fulvestrant was at least as effective and as equally well tolerated as anastrozole for the treatment of postmenopausal women with advanced and metastatic breast cancer. In a retrospective analysis of the combined data from these trials, mean duration of response was significantly greater for fulvestrant compared with anastrozole. These new hormonal treatments expand the choice of endocrine therapy for women with advanced breast cancer and offer new options for sequencing and combining treatments.

Modulation of epidermal growth factor receptor in endocrine-resistant, oestrogen receptor-positive breast cancer.

There is an increasing body of evidence demonstrating that growth factor networks are highly interactive with oestrogen receptor (ER) signalling in the control of breast cancer growth. As such, tumour responses to anti- hormones are likely to be a composite of the ER and growth factor inhibitory activity of these agents. The current article examines the modulation of growth factor networks during endocrine response, and presents in vitro and clinical evidence that epidermal growth factor receptor signalling, maintained in either an ER-dependent or -independent manner, is critical to anti- hormonal-resistant breast cancer cell growth. The considerable potential of the epidermal growth factor receptor-selective tyrosine kinase inhibitor, ZD 1839 (Iressa; AstraZeneca) to efficiently treat, and perhaps even prevent, endocrine-resistant breast cancer is highlighted.

Comparison of the short-term biological effects of 7alpha-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)-nonyl]estra-1,3,5, (10)-triene-3,17beta-diol (Faslodex) versus tamoxifen in postmenopausal women with primary breast cancer.

7Alpha-[9-(4,4,5,5,5-pentafluoropentylsulfinyl)-nonyl]estra-1,3,5, (10)-triene-3,17beta-diol (ICI 182,780; Faslodex) is a novel steroidal antiestrogen. This partially blind, randomized, multicenter study compared the effects of single doses of long-acting ICI 182,780 with tamoxifen or placebo on estrogen receptor (ERalpha) and progesterone receptor (PgR) content, Ki67 proliferation-associated antigen labeling index (Ki67LI), and the apoptotic index in the primary breast tumors of postmenopausal women. Previously untreated patients (stages T(1)-T(3); ER-positive or -unknown) were randomized and received a single i.m. dose of ICI 182,780 50 mg (n = 39), ICI 182,780 125 mg (n = 38), or ICI 182,780 250 mg (n = 44) or oral tamoxifen 20 mg daily (n = 36) or matching tamoxifen placebo (n = 43) for 14-21 days before tumor resection surgery with curative intent. The ER and PgR H-scores, together with the Ki67LI were determined immunohistochemically in the matched pretreatment biopsy and the posttreatment surgical specimens. The apoptotic index was determined by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling on the same samples. The effects of treatment on each of these parameters were compared using analysis of covariance. ICI 182,780 produced dose-dependent reductions in ER and PgR H-scores and in the Ki67LI. The reductions in ER expression were statistically significant at all doses of ICI 182,780 compared with placebo (ICI 182,780 50 mg, P = 0.026; 125 mg, P = 0.006; 250 mg, P = 0.0001), and for ICI 182,780 250 mg compared with tamoxifen (P = 0.024). For PgR H-score, there were statistically significant reductions after treatment with ICI 182,780 125 mg (P = 0.003) and 250 mg (P = 0.0002) compared with placebo. In contrast, tamoxifen produced a significant increase in the PgR H-score relative to placebo, and consequently, all doses of ICI 182,780 produced PgR values that were significantly lower than those in the tamoxifen-treated group. All doses of ICI 182,780 significantly reduced Ki67LI values compared with placebo (ICI 182,780 50 mg, P = 0.046; 125 mg, P = 0.001; 250 mg, P = 0.0002), but there were no significant differences between any doses of ICI 182,780 and tamoxifen. ICI 182,780 did not alter the apoptotic index when compared with either placebo or tamoxifen. Short-term exposure to ICI 182,780 reduces the ERalpha in breast tumor cells in a dose-dependent manner by down-regulating ER protein concentration. The reductions in tumor PgR content by ICI 182,780 demonstrate that ICI 182,780, unlike tamoxifen, is devoid of estrogen-agonist activity. Reductions in tumor cell proliferative activity (as indicated by Ki67LI) show that ICI 182,780 is likely to have antitumor activity in the clinical setting.

Growth factors and their receptors: new targets for prostate cancer therapy.

Stimulation of the signal transduction pathway of the epidermal growth-factor receptor (EGFR) tyrosine kinase family of receptors in tumor cells enhances cellular proliferation, prevents apoptosis, and promotes tumor-cell mobility, adhesion, and invasion. Therapeutic approaches used to target the EGFR and its signal transduction cascade include (1) monoclonal antibodies (eg, cetuximab [IMC-C225]) directed against the extracellular binding domain of the receptor; and (2) trastuzumab, a monoclonal antibody binding to the HER2 receptor; immunotoxin conjugates use an antibody directed against EGFR joined to a cell toxin. All are in clinical trials for a number of cancers, including prostate cancer. Antisense strategies are in preclinical development. Low-molecular-weight inhibitors of the EGFR tyrosine kinase also in clinical development include OSI-774, PD182905, PKI-166, CI-1033, and ZD1839. ZD1839 has shown encouraging results in patients with prostate cancer in phase 1 trials. mn

Prospects for combining hormonal and nonhormonal growth factor inhibition.

In patients with estrogen receptor (ER)-negative disease or ER+ hormone-resistant disease, the dominant influence on tumor cell growth is growth factors, e.g., epidermal growth factor (EGF), heregulins, and insulin-like growth factors acting through specific receptor tyrosine kinases at the cell surface. This superfamily of ligand-activated growth factor receptors triggers cascades of biochemical signals that influence tumor cell motility, invasiveness, angiogenesis, and survival, as well as proliferation. In breast tumors, expression of epidermal growth factor receptor (EGFR) and/or erbB2 is associated with poor prognosis; the therapeutic utility of blocking these receptors has been established using trastuzumab (Herceptin), a monoclonal antibody that blocks erbB2 signaling. An alternative therapeutic approach is offered by small molecule inhibitors of EGFR-TK, exemplified by ZD1839 (Iressa), a potent and selective EGFR-TK inhibitor. Resistance to tamoxifen is associated with up-regulation of the EGFR-TK pathway and mitogen-activated protein kinase activity is substantially increased in tamoxifen-resistant MCF-7 cells. ZD1839 treatment of tamoxifen-resistant MCF-7 cells blocks mitogen-activated protein kinase activity. Furthermore, treatment of wild-type MCF-7 cells with tamoxifen and ZD1839 prevents development of tamoxifen resistance. These data support the potential clinical utility of ZD1839 in tamoxifen-resistant breast cancer and suggest the possibility of preventing resistance by the early use of combination ZD1839 with antiestrogenic agents such as tamoxifen or ICI 182,780.

ICI 182,780 (Faslodex): development of a novel, "pure" antiestrogen.

BACKGROUND: The nonsteroidal antiestrogen tamoxifen is well established as an effective treatment for patients with breast carcinoma, both for the treatment of metastatic disease and as an adjuvant to surgery for patients with primary breast carcinoma. In addition to exerting antagonistic effects on the estrogen receptor, tamoxifen and its derivatives act as partial agonists on certain tissues. These agonistic effects, for example, endometrial stimulation and stimulation of tumor growth after previous response to tamoxifen, may limit their clinical efficacy. ICI 182,780 (Faslodex) from AstraZeneca (Cheshire, United Kingdom) is a novel, steroidal estrogen antagonist that was designed to be devoid of estrogen agonist activity in preclinical models. METHODS: ICI 182,780 was tested in a large number of in vitro and in vivo preclinical models, and its value was assessed clinically when administered before surgery for breast carcinoma and hysterectomy for benign conditions and after failure of tamoxifen in patients with advanced breast carcinoma. RESULTS: All data indicated that ICI 182,780 is devoid of agonist activity in preclinical models and in clinical trials. It inhibits growth of the breast and endometrium. In animal models, it does not cross the blood-brain barrier and appears to be neutral with respect to lipids and bone. ICI 182,780 down-regulates the estrogen receptor and is active in tamoxifen-resistant breast carcinoma. In a small, Phase II study, durable responses were seen: Phase III clinical trials are in progress comparing ICI 182,780 with anastrozole and tamoxifen in the treatment of patients with advanced breast carcinoma. CONCLUSIONS: ICI 182,780 specifically down-regulates the estrogen receptor and, thus, represents the first of a new class of therapeutic agents. In this report, the authors present the current evidence that distinguishes ICI 182,780 from tamoxifen and related nonsteroidal compounds and establishes ICI 182,780 as the first in a new class of therapeutic agents.

Delayed G-CSF after autologous progenitor cell transplantation: a prospective randomized trial.

G-CSF is given after autologous progenitor cell transplantation to accelerate neutrophil engraftment. Historically, G-CSF has been started on the day of progenitor cell infusion. To study the timing of the initiation of G-CSF after autologous peripheral blood progenitor cell (PBPC) transplantation, we conducted a prospective, randomized trial comparing the initiation of G-CSF therapy on day 0, day +3 or day +5 after autologous PBPC transplantation. Seventy patients with diagnoses of breast cancer, non-Hodgkin's lymphoma, Hodgkin's disease, or multiple myeloma were prospectively randomized to one of the three treatment arms. All patients were treated with a chemotherapy (only) preparative regimen. The source of hematopoietic reconstitution was PBPC alone (without autologous marrow), and all patients yielded a minimum of 2 x 10(6) CD34+ cells per kilogram. Times to neutrophil engraftment and platelet engraftment were identical in the three treatment groups, with neutrophil engraftment occurring at a median of 10, 11 and 11 days when starting G-CSF on day 0, day 3 or day 5, respectively. Time to platelet transfusion independence was 14, 11 and 14 days by treatment group. We conclude that delaying the initiation of G-CSF from day 0 to day +5 does not affect engraftment and results in cost savings.

New EGF-R selective tyrosine kinase inhibitor reveals variable growth responses in prostate carcinoma cell lines PC-3 and DU-145.

The effect of an EGF-R selective tyrosine kinase inhibitor ZM252868 was evaluated on the proliferation of PC-3 and DU-145 prostate cancer cell lines, which are purported to utilize an EGF-R-mediated autocrine pathway for regulation of cell growth. Basal growth of DU-145 cells was inhibited in a dose-dependent manner by the inhibitor, showing a 70% reduction at 1 microM, whilst the growth of PC-3 cells was not affected at this concentration. In the presence of 0.1 microM inhibitor, EGF and TGF alpha-stimulated DU-145 cell growth was decreased to below basal levels, while only TGF alpha-stimulated PC-3 cell growth was inhibited at a 1-microM concentration. Any growth responses to aFGF, bFGF, KGF, IGF1 and PDGF by DU-145 and PC-3 cells were unaffected by the inhibitor at concentrations of 1 microM or less. Additionally, the distribution of immunoreactive EGF-R varied between DU-145 and PC-3 cells, with EGF-R being predominately located on the cell membrane and in the cytoplasm, respectively.

Cognitive functioning, weight change and therapy in anorexia nervosa.

Anorexia nervosa is associated with impairments in cognitive function which have been hypothesized to be fundamentally attentional in nature. The current study investigated whether therapy and weight gain affect these impairments. A group of anorexics (N = 12) completed a battery of cognitive performance tasks and self-report measures of psychopathology on three occasions, over the course of 12 weeks of in-patient treatment. A non-clinical control population (N = 17) completed the same measures. The anorexics improved on all measures of psychopathology and affective state as a result of therapy. Anorexics displayed poorer recall, reaction times, and motor speed than the control subjects. Although there was a gain in weight over the course of therapy, there was no corresponding improvement in cognitive performance. Impaired task performance in anorexics was not directly related to their psychopathology or affective state.

Epidemiology of anorexia nervosa.

Findings of epidemiological studies of the rates, incidence, and prevalence of eating disorder over time and in different populations are reviewed. Risk factors for anorexia nervosa and bulimia nervosa are also addressed. Methodological recommendations for future directions in epidemiological studies of eating disorders are presented.

Short-term effects of pure anti-oestrogen ICI 182780 treatment on oestrogen receptor, epidermal growth factor receptor and transforming growth factor-alpha protein expression in human breast cancer.

Expression of oestrogen receptor (ER), epidermal growth factor receptor (EGFR) and transforming growth factor-alpha (TGF alpha) proteins was assessed by immunocytochemistry on primary breast cancer specimens obtained before and following short-term (7-day) presurgical exposure to pure anti-oestrogen (7 alpha- [9- (4,4,5,5,5-pentafluoropentylsulphinyl) nonyl] estra-1,3,5, (10)-triene-3,17 beta-diol, ICI 182780) treatment and compared with no-treatment controls. Paired needle-core and mastectomy samples were obtained from 21 patients. Effects of ICI 182780 (10(-7)M) on MCF7 breast cancer cell ER, EGFR and TGF alpha expression were also examined over 14 days. ER protein was significantly suppressed by ICI 182780 in vivo (P = 0.009) and comparative analysis of short term ICI 182780 effects in vitro, using ER-positive MCF7 cells, gave largely equivalent results. EGFR and TGF alpha protein levels were unaltered by treatment. ICI 182780 suppresses ER without a concomitant rise in either EGFR or TGF alpha.

The use of risperidone in treatment-resistant schizophrenia: two case reports.

The role of risperidone in the management of treatment-resistant schizophrenia remains unclear. We describe two patients with treatment-resistant schizophrenia characterized by unremitting delusions, thought disorder and self-neglect who had a sustained improvement in their symptoms soon after starting risperidone. Risperidone may be a suitable alternative to clozapine in some patients unresponsive to conventional antipsychotics.