Type I insulin-like growth factor receptor gene expression in normal human breast tissue treated with oestrogen and progesterone

The Role of Metabolic Factors in Renal Cancers

An increasing number of evidence indicates that metabolic factors may play an important role in the development and progression of certain types of cancers, including renal cell carcinoma (RCC). This tumour is the most common kidney cancer which accounts for approximately 3–5% of malignant tumours in adults. Numerous studies indicated that concomitant diseases, including diabetes mellitus (DM) and hypertension, as well as obesity, insulin resistance, and lipid disorders, may also influence the prognosis and cancer-specific overall survival. However, the results of studies concerning the impact of metabolic factors on RCC are controversial. It appears that obesity increases the risk of RCC development; however, it may be a favourable factor in terms of prognosis. Obesity is closely related to insulin resistance and the development of diabetes mellitus type 2 (DM2T) since the adipocytes in visceral tissue secrete substances responsible for insulin resistance, e.g., free fatty acids. Interactions between insulin and insulin-like growth factor (IGF) system appear to be of key importance in the development and progression of RCC; however, the exact role of insulin and IGFs in RCC pathophysiology remains elusive. Studies indicated that diabetes increased the risk of RCC, but it might not alter cancer-related survival. The risk associated with a lipid profile is most mysterious, as numerous studies provided conflicting results. Even though large studies unravelling pathomechanisms involved in cancer growth are required to finally establish the impact of metabolic factors on the development, progression, and prognosis of renal cancers, it seems that the monitoring of health conditions, such as diabetes, low body mass index (BMI), and lipid disorders is of high importance in clear-cell RCC.

Timing of breast cancer surgery during the menstrual cycle-is there an optimal time of the month?

An intriguing relationship between menstrual cycle phase at the time of breast cancer surgery and clinical outcomes was first proposed in the late 1980s. Despite a number of clinical studies conducted to address this, as well as meta-analyses and systematic reviews, there remains significant controversy surrounding the effect of menstrual cycle phase at time of surgery on the prognosis of premenopausal breast cancer. While some studies have suggested that surgery performed during the luteal phase results in the most favourable outcome, other studies report the follicular phase is more favourable, and others show no association. Given the conflicting results, there remains insufficient evidence to determine whether there is an optimal time of the month to perform surgery. This issue has dogged breast cancer surgery for decades; knowledge of an optimal time of the month to conduct surgery would be a simple approach to improving patient outcomes. This review explores the potential biological mechanisms through which the hormonal milieu might contribute to differences in prognosis, and why clinical findings are so variable. It is concluded that a significant problem with current clinical research is the lack of insight from mechanistic studies. While there are a number of plausible biological mechanisms that could lead to altered survival, supporting evidence is limited. There are also variable approaches to defining the menstrual cycle phase and hormone receptor status of the tumour and few studies controlled for prognostic factors such as tumour size and stage, or addressed the impact of adjuvant treatments. Elucidation of the specific confounding factors, as well as biological mechanistic pathways that could explain the potential relationship between timing of surgery and survival, will greatly assist in designing robust well-controlled prospective clinical studies to evaluate this paradigm.

The association between BMI and kidney cancer risk: An updated dose-response meta-analysis in accordance with PRISMA guideline

OBJECTIVE

Obesity is considered as one of the risk factors of kidney cancer. However, the results are not consistent in reported original studies, as well as in published meta-analysis. This study aims to clarify the relationship between overweight/obesity and kidney cancer by an updated overall and dose-response meta-analysis.

METHODS

This meta-analysis was conducted in accordance with PRISMA guideline. Relevant studies were searched using PubMed, Embase, and Web of Science databases. The studies were limited to human cohort studies in English and Chinese language. Random-effect models and dose-response meta-analysis were used to synthesize the results. Subgroup analyses were also conducted based on the characteristics of participants.

RESULTS

Twenty-four cohort studies with 8,953,478 participants were included in our meta-analysis. Compared to the normal weight, the pooled RRs of kidney cancer was 1.35 (1.27-1.43) in overweight and 1.76 (1.61-1.91) in obese participants. An increased kidney cancer risk of 1.06 (1.05-1.06) for each 1 kg/m increase in BMI was showed in dose-response meta-analysis. No significant heterogeneity was found across studies with I = 39.4% for overweight, and I = 43.3% for obesity.

CONCLUSION

The overall and dose-response meta-analysis suggested that overweight/obesity increases the risk of kidney cancer both in men and women.

Assessment of Multifactor Gene-Environment Interactions and Ovarian Cancer Risk: Candidate Genes, Obesity, and Hormone-Related Risk Factors

BACKGROUND

Many epithelial ovarian cancer (EOC) risk factors relate to hormone exposure and elevated estrogen levels are associated with obesity in postmenopausal women. Therefore, we hypothesized that gene-environment interactions related to hormone-related risk factors could differ between obese and non-obese women.

METHODS

We considered interactions between 11,441 SNPs within 80 candidate genes related to hormone biosynthesis and metabolism and insulin-like growth factors with six hormone-related factors (oral contraceptive use, parity, endometriosis, tubal ligation, hormone replacement therapy, and estrogen use) and assessed whether these interactions differed between obese and non-obese women. Interactions were assessed using logistic regression models and data from 14 case-control studies (6,247 cases; 10,379 controls). Histotype-specific analyses were also completed.

RESULTS

SNPs in the following candidate genes showed notable interaction: IGF1R (rs41497346, estrogen plus progesterone hormone therapy, histology = all, P = 4.9 × 10(-6)) and ESR1 (rs12661437, endometriosis, histology = all, P = 1.5 × 10(-5)). The most notable obesity-gene-hormone risk factor interaction was within INSR (rs113759408, parity, histology = endometrioid, P = 8.8 × 10(-6)).

CONCLUSIONS

We have demonstrated the feasibility of assessing multifactor interactions in large genetic epidemiology studies. Follow-up studies are necessary to assess the robustness of our findings for ESR1, CYP11A1, IGF1R, CYP11B1, INSR, and IGFBP2 Future work is needed to develop powerful statistical methods able to detect these complex interactions.

IMPACT

Assessment of multifactor interaction is feasible, and, here, suggests that the relationship between genetic variants within candidate genes and hormone-related risk factors may vary EOC susceptibility. Cancer Epidemiol Biomarkers Prev; 25(5); 780-90. ©2016 AACR.

Timing of breast cancer surgery, menstrual phase, and prognosis: Systematic review and meta-analysis

BACKGROUND

For over 25 years, there has been a debate revolving around the timing of breast cancer surgery, menstrual cycle, and prognosis.

METHODS

This systematic review synthesizes and evaluates the body of evidence in an effort to inform evidence-based practice. A keyword and reference search was performed in PubMed and Web of Science to identify human studies that met the inclusion criteria. A total of 58 studies (48 international and 10 U.S.-based) were identified. We provided a narrative summary on study findings and conducted a meta-analysis on a subset of studies where quantitative information was available.

RESULTS

Findings from both qualitative and quantitative analyses were inconclusive regarding performing breast cancer surgery around a specific phase of the menstrual cycle.

CONCLUSION

Based on the Institute of Medicine criteria, evidence is insufficient to recommend a change in current primary breast cancer surgery practice based on menstrual phase.

Luminal B breast cancer: molecular characterization, clinical management, and future perspectives

Gene expression profiling has reshaped our understanding of breast cancer by defining and characterizing four main intrinsic molecular subtypes: human epidermal growth factor receptor 2-enriched, basal-like, luminal A, and luminal B subtypes. Luminal B breast cancer has been reported to have lower expression of hormone receptors, higher expression of proliferation markers, and higher histologic grade than luminal A. It also exhibits worse prognosis and has a distinct profile of response to hormone therapy and chemotherapy. Although luminal cancers share similarities, the studies conducted in recent years using next-generation sequencing technology show that luminal A and B breast cancers should be perceived as distinct entities, with specific oncogenic drivers, rather than more proliferative varieties of luminal tumors. This review discusses the definition and molecular characterization of luminal B breast cancer and presents the available clinical evidence for chemotherapy and endocrine therapy patterns of response. It also provides an overview of ongoing research on molecularly targeted agents for this disease.

Synthetic retinoid fenretinide in breast cancer chemoprevention

Preclinical models suggest that retinoids inhibit mammary carcinogenesis. The induction of apoptosis is a unique feature of fenretinide, the most-studied retinoid in clinical trials of breast cancer chemoprevention, owing to its selective accumulation in breast tissue and its favorable toxicological profile. In a Phase III breast cancer prevention trial, fenretinide showed a strong trend of reduction of incidence of second breast malignancies in premenopausal women, which was confirmed by 15 years of follow-up. This warrants further research on the mechanisms of action and potential efficacy of fenretinide and provides the rationale for a Phase III primary prevention trial in young women at high risk for breast cancer. This review will highlight the role of fenretinide in breast cancer chemoprevention.

Insulin-like growth factor - oestradiol crosstalk and mammary gland tumourigenesis

Development and differentiation of the mammary gland are dependent on the appropriate temporal expression of both systemically acting hormones and locally produced growth factors. A large body of evidence suggests that molecular crosstalk between these hormonal and growth factor axes is crucial for appropriate cell and tissue function. Two of the most important trophic factors involved in this process are the oestrogen (E) and insulin-like growth factor (IGF) molecular axes. The reciprocal crosstalk that exists between these pathways occurs at transcriptional/post-transcriptional and translational/post-translational levels regulate the expression and activity of genes involved in this process. In a clinical context an important consequence of such crosstalk in the mammary gland is the role which it may play in the aetiology, maintenance and development of breast tumours. Although oestradiol (E2) acting through oestrogen receptors α and β (ERα/β) is important for normal mammary gland function it can also provide a mitogenic drive to ER+ breast tumours. Therefore over several years anti-oestrogen therapeutic regimens in the form of selective oestrogen receptor modulators (SERMs - e.g. tamoxifen), aromatase inhibitors (AI e.g. anastrozole) or selective oestrogen receptor down regulators (SERDs - e.g. fulvestrant) have been used in an adjuvant setting to control tumour growth. Although initial response is usually encouraging, large cohorts of patients eventually develop resistance to these treatments leading to tumour recurrence and poor prognosis. There are potentially many routes by which breast cancer (BC) cells could escape anti-oestrogen based therapeutic strategies and one of the most studied is the possible growth factor mediated activation of ER(s). Because of this, growth factor modulation of ER activity has been an intensively studied route of molecular crosstalk in the mammary gland. The insulin-like growth factors (IGF-1 and -2) are amongst the most potent mitogens for mammary epithelial cells and there is accumulating evidence that they interact with the E2 axis to regulate mitogenesis, apoptosis, adhesion, migration and differentiation of mammary epithelial cells. Such interactions are bi-directional and E2 has been shown to regulate the expression and activity of IGF axis genes with the general effect of sensitising breast epithelial cells to the actions of IGFs and insulin. In this short review we discuss the evidence for the involvement of crosstalk between the insulin-like growth factor (IGF) and oestrogen axes in the mammary gland and comment on the relevance of such studies in the aetiology and treatment of BC.

An induction of microRNA, miR-7 through estrogen treatment in breast carcinoma

Background

Estrogen plays an important role in the development of estrogen-dependent breast carcinoma. Recently, several studies demonstrated a possible involvement of several micro RNAs (miRNAs) in the development of resistance to endocrine therapy in breast cancer patients, but the correlation between estrogen actions and miRNA expression in breast carcinoma still remains largely unknown. Therefore, in this study, we examined the in vitro effects of estrogen upon miRNA expression profiles in breast carcinoma.

Methods

We first screened the miRNA expression profiles induced by 17β-Estradiol (E2) using RT² miRNA PCR Array in the ER-positive breast carcinoma cell line MCF-7. We identified miR-7 as the important miRNA associated with estrogen actions in these cells and further examined the changes of estrogen-dependent EGFR expression by miR-7 in ER-positive or -negative breast carcinoma cell lines including MCF-7. We also evaluated the correlation between miR-7 and EGFR expression in breast carcinoma cells derived from 21 patients using laser capture microdissection combined with quantitative reverse transcriptase-PCR.

Results

Seventeen miRNAs were significantly induced by E2 treatment in the MCF-7 cell line. Among 17 miRNAs induced by estradiol treatment, only miR-7 expression was significantly decreased by subsequent ICI treatment. The expression of miR-7 was up-regulated 2.94-fold by E2 treatment. miR-7 was reported to suppress epidermal growth factor receptor (EGFR) expression in several human malignancies. Transfection of miR-7 significantly suppressed EGFR mRNA levels in MCF-7 cells. Depletion of E2 from cell culture media also increased the expression level of EGFR mRNA in MCF-7 and T-47D cells but not in ER-negative, MDA-MB-231 and SK-BR-3 cells. We also evaluated the status of miR-7 in breast carcinoma tissues, but the correlation between the status of miR-7 and EGFR in carcinoma cells isolated by laser capture microscopy was not detected.

Conclusions

These results suggest that miR-7 may play a role in the development of resistance to endocrine therapy in breast cancer patients through regulating EGFR expression of carcinoma cells.

Emerging targeted agents in metastatic breast cancer

Extensive preclinical experimentation has conceptually changed the way we perceive breast cancer, with the wide spectrum of genomic alterations governing its malignant progression now being recognized. Functional genomics has helped us identify important genetic defects that can be pharmaceutically targeted in the setting of metastatic disease. Rationally chosen combination regimens are now under clinical investigation. Recent data underline the functional importance of the tumour-associated stroma, with several candidate molecular targets now emerging. Data elucidating a cellular hierarchy within the breast cancer cellular compartment support the existence of a therapy-resistant subpopulation of breast cancer stem cells. Identification of the developmental pathways that dictate their malignant phenotype and use of high-throughput screening techniques are leading to new therapeutic avenues. In this Review, we present the biological rationale for the clinical development of more than 15 different classes of targeted agents in breast cancer, along with evidence supporting rational combinations. However, metastatic breast cancer resembles a Darwinian evolutionary system, with 'driver' mutations and epigenetic changes determining clonal selection according to branching trajectories. This evolution is reflected in the molecular heterogeneity of the disease and poses severe impediments to the successful clinical development of emerging targeted agents.

Indole-3-carbinol disrupts estrogen receptor-alpha dependent expression of insulin-like growth factor-1 receptor and insulin receptor substrate-1 and proliferation of human breast cancer cells

We previously established that Indole-3-Carbinol (I3C), a natural hydrolysis product of glucobrassicin in cruciferous vegetables, arrests the proliferation of estrogen-dependent human breast cancer cells and induces protein degradation of Estrogen Receptor-alpha (ERα). We demonstrate in human MCF-7 breast cancer cells that I3C ablates expression of Insulin-like Growth Factor Receptor-1 (IGF1R) and Insulin Receptor Substrate-1 (IRS1), downstream effectors of the IGF1 signaling pathway. Exogenous ERα reversed the I3C mediated loss of IGF1R and IRS1 gene expression demonstrating that down-regulation of ERα is functionally linked to I3C control of IGF1R and IRS1 expression. I3C disrupted binding of endogenous ERα, but not Sp1, to ERE-Sp1 composite elements within the IGF1R/IRS1 promoters. Exogenous ERα abrogated, and combined expression of IGF1R and IRS1 attenuated, the I3C mediated cell cycle arrest. Therefore, I3C inhibits proliferation of estrogen-sensitive breast cancer cells through disruption of ERα-mediated transcription of cell signaling components within the IGF1 cascade.

Human breast cell proliferation and its relationship to steroid receptor expression

The steroidal regulation of proliferation and differentiation in the rodent mammary gland is well described, but how ovarian hormones regulate these processes in the human remains poorly understood. To investigate this, we developed the athymic nude mouse model in which intact normal human breast tissue is grafted subcutaneously and treated with estrogen and/or progesterone at human physiological serum levels. We demonstrated, first, that estrogen and not progesterone is the major epithelial cell mitogen in the adult non-pregnant, non-lactating breast, second, that estrogen induces progesterone receptor (PR) expression and, third, that PR expression is maximally induced at low estrogen concentrations while a higher amount of estrogen was required to induce proliferation. These data raised the question of whether one cell type possessed differential responses to high and low estrogen concentrations or whether PR expression and proliferation occurred in two cell populations. Using double-label immunofluorescence, we demonstrated that steroid receptor expression and cell proliferation (Ki67 antigen) occurred in separate cell populations in normal human breast epithelium, and that cells expressing the estrogen receptor-alpha (ERalpha) invariably contained the PR. We also found that this dissociation between steroid receptor expression and cell proliferation in normal epithelium was disrupted at an early stage in breast tumor formation. Recent findings presented herein support the proposal that some ERalpha/PR-positive epithelial cells are quiescent breast stem cells that act as 'steroid hormone sensors'. Such hormone sensor cells are likely to secrete positive or negative paracrine/juxtacrine factors dependent on the prevailing estrogen or progesterone concentration to influence the proliferative activity of adjacent ERalpha/PR-negative epithelial cells.

Cell density-dependent transcriptional activation of endocrine-related genes in human adipose tissue-derived stem cells

Adipose tissue is recognized as an endocrine organ that plays an important role in human diseases such as type II diabetes and cancer. Human adipose tissue-derived stem cells (ASCs), a distinct cell population in adipose tissue, are capable of differentiating into multiple lineages including adipogenesis. When cultured in vitro under a confluent condition, ASCs reach a commitment stage for adipogenesis, which can be further induced into terminally differentiated adipocytes by a cocktail of adipogenic factors. Here we report that the confluent state of ASCs triggers transcriptional activation cascades for genes that are responsible for the endocrine function of adipose tissue. These include insulin-like growth factor 1 (IGF-1) and aromatase (Cyp19), a key enzyme in estrogen biosynthesis. Despite similar adipogenic potentials, ASCs from different individuals display huge variations in activation of these endocrine-related genes. Bioinformatics and experimental data suggest that transcription factor Foxo1 controls a large number of "early" confluency-response genes, which subsequently induce "late" response genes. Furthermore, siRNA-mediated knockdown of Foxo1 substantially compromises the ability of committed ASCs to stimulate tumor cell migration in vitro. Thus, our work suggests that cell density is an important determinant of the endocrine potential of ASCs.

Serum insulin-like growth factor-I and mammary tumor development in ad libitum-fed, chronic calorie-restricted, and intermittent calorie-restricted MMTV-TGF-alpha mice

The effect of chronic (CCR) and intermittent (ICR) caloric restriction on serum insulin-like growth factor (IGF)-I levels and mammary tumor (MT) development was investigated. Ten-week-old MMTV-TGF-alpha female mice were assigned to ad libitum-fed (AL; AIN-93M diet), ICR [3-week 50% caloric restriction using AIN-93M-mod diet, 2x protein, fat, vitamins, and minerals followed by 3 weeks of daily 100% AL consumption of AIN-93M ( approximately 75% of AL for each 6-week cycle)], and CCR (calorie and nutrient intake matched for each 6-week ICR cycle) groups. Half of the mice from each group were sacrificed at 79 (end of restriction) or 82 (end of refeeding) weeks of age. Serum was obtained at euthanasia and in cycles 1, 3, 5, 8, and 11. MT incidence was 71.0%, 35.4%, and 9.1% for AL, CCR, and ICR mice. ICR-Restricted mice had significantly lower terminal serum IGF-I and IGF-I/IGF binding protein-3 (IGFBP-3) ratio than CCR, ICR-Refed, and AL mice. There were no differences in terminal IGFBP-3. Final body, internal, and mammary fat pad weights correlated positively with IGF-I and negatively with IGFBP-3. Few changes were found for protein expression of IGF-IRalpha and IGFBP-3 in mammary tissue and MTs. During the study, IGF-I levels of ICR-Restricted mice were reduced, whereas refeeding allowed partial recovery. For all groups, elevated IGF-I levels preceded MT detection, although not all values were significant versus mice without MTs. However, the specific role of IGF-I in the protective effect of calorie restriction remains to be determined. These results confirm that ICR prevents MT development to a greater extent than CCR.

Flavonoids as RTK inhibitors and potential anticancer agents

Tyrosine kinase receptors (RTKs) play a crucial role in the regulation of the cell division cycle. Currently more than 50 RTKs divided into several subfamilies have been described. The inhibition of these enzymes has emerged as an important research-area. Compounds able to inhibit the activity of these enzymes are expected to display antiproliferative properties. Flavonoids are representative of various small molecules acting as RTK inhibitors. These naturally occurring compounds are able to bind to the ATP-binding site of several kinases. The most plausible current hypothesis explaining the action of these substances on kinases is that the chromenone moiety of the flavonoid acts as a mimetic of the adenine moiety of ATP, the receptor co-factor. In this review, we report recent results on the activity of natural and synthetic derivatives of flavonoids as inhibitors of RTKs. Mechanistic aspects, the therapeutic usefulness, and the potential clinical use are discussed.

Role of the insulin-like growth factor system on an estrogen-dependent cancer phenotype in the MCF-7 human breast cancer cell line

We previously established that exposure of the estrogen receptor (ER) alpha positive MCF-7 human breast cancer cell line to 17-beta-estradiol (E2) results in the post-confluent development of multilayered cellular aggregates (foci) which is consistent with the in vivo cancer phenotype of uncontrolled cellular proliferation. In this investigation, the interaction between the insulin-like growth factor receptor (IGF-IR) and ER-signaling systems in regard to post-confluent focus development was studied. We demonstrated that focus development requires the presence of E2 and insulin-like growth factor I (IGF-I) or insulin-like growth factor II (IGF-II), as well as intact ER and IGF-IR. Focus development in MCF-7 cultures, which occurs only after formation of a confluent monolayer, coincides with E2 regulation of key members of the IGF-signaling system such as IGF-IR, IGF-II, insulin receptor substrate 1 (IRS-1), and insulin-like growth factor binding protein 3 (IGFBP-3), as demonstrated by real-time polymerase chain reaction (PCR). To establish the relevancy of an intact IGF-signaling system for foci formation, we generated stable clones from MCF-7 with IGF-IR suppressed by siRNA. Results from these studies implicate signaling through the IGF-IR to be an integral requirement for E2-dependent post-confluent proliferation and focus formation. In summary, these studies establish the interactive roles of IGFs and E2 in the post-confluent development of foci, and will allow subsequent identification of targets for therapeutic intervention in the control and treatment of estrogen-dependent breast cancer.

Regulation of MDMX expression by mitogenic signaling

MDMX is an important regulator of p53 transcriptional activity and stress response. MDMX overexpression and gene amplification are implicated in p53 inactivation and tumor development. Unlike MDM2, MDMX is not inducible by p53, and little is known about its regulation at the transcriptional level. We found that MDMX levels in tumor cell lines closely correlate with promoter activity and mRNA level. Activated K-Ras and insulin-like growth factor 1 induce MDMX expression at the transcriptional level through mechanisms that involve the mitogen-activated protein kinase and c-Ets-1 transcription factors. Pharmacological inhibition of MEK results in down-regulation of MDMX in tumor cell lines. MDMX overexpression was detected in approximately 50% of human colon tumors and showed strong correlation with increased extracellular signal-regulated kinase phosphorylation. Therefore, MDMX expression is regulated by mitogenic signaling pathways. This mechanism may protect normal proliferating cells from p53 but also hamper p53 response during tumor development.

Randomized Dose-Ranging Trial of Tamoxifen at Low Doses in Hormone Replacement Therapy Users

Purpose

The combination of hormone replacement therapy (HRT) and low-dose tamoxifen may retain the benefits while reducing the risks of either agent. We assessed the optimal biologic dose and schedule of tamoxifen in HRT users using surrogate end point biomarkers and menopausal symptoms.

Subjects and Methods

Two hundred ten current or de novo HRT users were randomly assigned to one of the following four arms: tamoxifen 1 mg/day and placebo/week, placebo/day and tamoxifen 10 mg/week, tamoxifen 5 mg/day and placebo/week, or both placebos for 12 months. The primary end point was the change of plasma insulinlike growth factor 1 (IGF-I) through 12 months, and secondary end points were IGF-I/IGF binding protein-3 (IGFBP-3) ratio, fibrinogen, antithrombin III, C reactive protein, C-telopeptide, mammographic percent density, and endometrial thickness. Endometrial proliferation was assessed by Pipelle biopsy in superficial, deep glandular, and stromal compartments after 12 months.

Results

Compared with placebo, IGF-I declined in all tamoxifen arms (P = .005), with a greater change on 5 mg/day (P = .019 v 10 mg/week or 1 mg/day). Tamoxifen increased IGFBP-3 and lowered antithrombin-III, C reactive protein, and mammographic density, with greater effects of 5 mg/day. Tamoxifen increased endometrial thickness but not Ki-67 expression, which was lower on 5 mg/day among the three doses. Menopausal symptoms were not significantly worsened by tamoxifen.

Conclusion

Doses of tamoxifen ≤ 5 mg/day modulate favorably biomarkers of breast carcinogenesis and cardiovascular risk in HRT users with no increase of endometrial proliferation and menopausal symptoms. A dose of 5 mg/day was the most effective and has been selected for a phase III trial in HRT users.

What clinicians need to know about antioestrogen resistance in breast cancer therapy

Tamoxifen is the drug most used for early breast cancer treatment in oestrogen receptor (ER) positive patients. Unfortunately, despite high ER tumour levels in a tumour, resistance to endocrine therapy, either de novo or acquired after prolonged treatment, can occur. In this review, we will try to summarise the postulated mechanisms of hormonal-resistance, namely, the role of co-regulators and the crosstalk between the HER-2, IGF-IR, Cox-2 and ER pathways. Other predictive markers of tamoxifen-resistance/response, such as cyclin E and UPA/PAI-1, are also discussed.

Does the timing of breast cancer surgery in pre-menopausal women affect clinical outcome? An update

There is some evidence that breast cancer surgery during the luteal phase in pre-menopausal women is associated with a better clinical outcome, however the evidence for this is still equivocal.

In this paper, after summarizing the normal physiology of the menstrual cycle, we examine how such an association may occur and provide a comprehensive review of the literature in the area.

Ovarian steroids and the human breast: regulation of stem cells and cell proliferation

Ovarian steroidal control of mammary gland proliferation and differentiation is not well defined in the human. We therefore developed the athymic nude mouse model in which intact normal human breast tissue is xenografted subcutaneously and treated with human physiological serum levels of oestrogen (E) and/or progesterone (P). We showed that: (i) E, and not P, is the major steroid hormone inducing proliferation of epithelial cells in the adult non-pregnant, non-lactating breast; (ii) E induces progesterone receptor (PR) expression; and (iii) PR expression is maximally induced at low E concentrations while a higher amount of E was required to induce proliferation. Using double label immuno-fluorescence, we demonstrated that cells expressing the oestrogen receptor-alpha (ER alpha) invariably contained the PR but that steroid receptor expression and cell proliferation (Ki67 antigen) were dissociated. Recently, we have demonstrated that some ER alpha/PR-positive epithelial cells are quiescent breast stem cells suggesting that they act as "steroid hormone sensors" that secrete paracrine factors to regulate the proliferative activity of adjacent ER alpha/PR-negative epithelial cells. The dissociation between steroid receptor expression and cell proliferation in normal epithelium was lost at an early stage in ER alpha/PR-positive breast tumour formation perhaps indicating that they arise from deregulation of the normally quiescent breast stem cells.

Extranuclear expression of hormone receptors in primary breast cancer

BACKGROUND

Hormone receptor (HR)-positive breast cancer cells grow through estrogen receptor (ER)-signaling pathways that mediate both genomic and nongenomic actions, which cross-talk with growth factors associated with resistance to tamoxifen. The aim of this study was to explore the cross-talk between extranuclear expression of ER and progesterone receptor (PR) and growth factor signaling pathways in primary breast cancer.

PATIENTS AND METHODS

The extranuclear expression of ER and PR was examined in 219 primary breast cancers by immunohistochemical staining. Specimens showing such expression were further examined for the expression of pAkt and aromatase. Staining reactions were scored on the basis of intensity and distribution in the tumors.

RESULTS

Extranuclear expression of ER or PR was observed in 21 cases (9.5%), which included four cases for ER and 20 cases for PR. Among these patients, HER-2, pAkt, and aromatase-positivity were observed in 14 cases (66.6%), 13 cases (61.9%), and 14 cases (66.6%), respectively. On the basis of nuclear HR expression, 11 of these cases were categorized as ER-positive/PR-negative, while two were ER-negative/PR-positive. Of these 13 cases, increased pAkt staining was found in 11 cases (84.6%). In particular, among the 11 ER-positive/PR-negative cases, elevated pAkt and aromatase were found in 10 (90.9%; P<0.01) and nine cases (81.8%), respectively.

CONCLUSIONS

PR is expressed extranuclearly more frequently than ER in primary breast cancer, and extranuclear HRs cross-talk with the Akt/HER-2-signaling pathways and activation of aromatase. These observations may explain the more beneficial effects of aromatase inhibitors than tamoxifen for ER-positive/PR-negative patients.

Estradiol increases VEGF in human breast studied by whole-tissue culture

Sex steroid exposure constitutes a risk factor for breast cancer, but little is known about the effects of sex steroids on the normal breast, largely because of the lack of convenient models. We have developed a method of culturing normal breast tissue ex vivo. We have applied this method to investigate the effects of estradiol and progesterone on the key angiogenic mediator, vascular endothelial growth factor (VEGF), in the breast. Whole breast tissue was obtained from routine reduction mammoplasty. Tissue biopsies were cultured in vitro for 1-3 weeks, and the expression of luminal cytokeratin 18 was determined by immunohistochemistry. As an application, tissue biopsies were treated in vitro for 1 week with or without estradiol or estradiol and progesterone. Estrogen receptor, progesterone receptor, and Ki-67 were analyzed, and VEGF levels were examined by quantitative immunoassay and immunohistochemistry. Whole breast tissue was cultured ex vivo for 1 week with preserved morphology. Increased detachment of the luminal epithelium was observed after 2 weeks. Estradiol increased extracellular levels of VEGF in normal breast tissue biopsy medium. The addition of progesterone had neither stimulatory nor inhibitory effects on secreted VEGF. The method of whole breast tissue culturing thus provide a means by which to explore the biology of normal breast tissue. Our results suggest that estradiol exerts pro-angiogenic effects in normal breast by increasing levels of biologically active VEGF.

Sex steroid regulation of angiogenesis in breast tissue

Angiogenesis is essential for normal function in the female reproductive tract and a prerequisite for growth and metastasis of solid tumors. Several factors, both inducers and inhibitors, play essential roles in the regulation of the angiogenic process. Exposure to sex steroids increases the risk of breast cancer but the mechanisms are poorly understood and the importance of angiogenesis in breast carcinogenesis is undefined. In the female reproductive tract ovarian hormones tightly regulate angiogenesis. The breast is also a target organ for sex steroids but very little is known about sex steroid effects on angiogenesis in normal breast tissue and breast cancer. In this review several regulators of angiogenesis, and their relation to sex steroids, in breast tissue are discussed. Increased knowledge in this area is of utmost importance for future therapeutic treatment options and for breast cancer prevention.

Role of insulin-like growth factor 1 receptor signalling in cancer

The insulin-like growth factor (IGF-1) signalling is highly implicated in cancer. In this signalling the IGF-1 receptor (IGF-1R) is unquestionable, the predominating single factor. IGF-1R is crucial for tumour transformation and survival of malignant cell, but is only partially involved in normal cell growth. This is in part due to the interactions with oncogenes. Recent findings suggest a close interplay with the p53/MDM2 pathway. Disturbances in components in the p53/MDM2/IGF-1R network may cause IGF-1R upregulation and growth advantage for the cancer cell. Targeting of IGF-1R is more and more seen as a promising option for future cancer therapy. Single chain antibodies and small molecules with selective effects on IGF-1R dependent malignant growth are of particular interest. Forthcoming clinical trials are welcome and will indeed be the only way to evaluate the impact of IGF-1R targeting in human cancer.

Hormonal regulation of hepatic IGF-I and IGF-II gene expression in the marine teleost Sparus aurata

The present work aimed to determine whether GnRH potentiates the effect of growth hormone (GH) on insulin-like growth factors (IGF-I and IGF-II) hepatic gene expression in Sparus aurata liver. Since several hepatic genes were shown to underlie direct regulation via the hepatic estrogen receptor, another aim was to extend our understanding of direct estrogen effects on liver IGFs gene expression. Pre-reproductive sea bream females were treated with GH, GnRH, estradiol-17beta, GH plus GnRH, and estradiol-17beta plus GH. After 72 hr, all treatment induced an increase of plasma estradiol well correlated with the increase of plasma vitellogenin (VTG) levels. IGF-I and IGF-II expression in the liver of treated females was determined by semi-quantitative RT-PCR, using beta-actin as internal standard. The results reported here show that GH significantly stimulates hepatic transcription of IGF-I and IGF-II genes. Surprisingly, E2 and GnRH treatments decreased both IGF-I and IGF-II mRNA levels. In fishes treated with GH plus GnRH, the GnRH contrasted the GH effect: the IGF-I mRNA levels were still significantly higher than in controls, while the effect of GH on IGF-II gene expression was totally abolished. At the same time, in the combined treatment with GH plus E2, the E2 counteracted the stimulatory effect of GH on both IGF-I and IGF-II genes expression.

Factors associated with circulating levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in 740 women at risk for breast cancer

Prospective studies have shown an association between elevated plasma levels of insulin-like growth factor-I (IGF-I) and/or decreased levels of its major circulating carrier protein insulin-like growth factor binding protein-3 (IGFBP-3) and increased risk of major cancers. Identifying the factors which affect these biomarkers is of particular interest as subjects at increased risk could benefit from lifestyle changes, and/or chemoprevention intervention. We evaluated the association between constitutional, hormonal and clinical factors and IGF-I and IGFBP-3 in 740 women, including 376 unaffected women and 364 women with intraepithelial neoplasia (IEN) or early invasive breast cancer enrolled in breast cancer chemoprevention trials, conducted at a single institution. Age, body mass index (BMI), height, waist to hip girth ratio (WHR), parity, menopausal status, age at menarche, number of affected first degree relatives, number of biopsies and breast cancer status were considered in the analysis. Women with early breast cancer had 21% higher IGF-I levels (p = 0.033) and 19% higher IGF-I/IGFBP-3 molar ratio (p = 0.047) than unaffected women. In unaffected women, age was negatively associated with IGF-I (p = 0.002) and IGF-I/IGFBP-3 (p = 0.001), while age at menarche was negatively associated with IGFBP-3 levels (p = 0.043). In women with IEN or early breast cancer, IGF-I levels were negatively associated with age (p < 0.001), and positively associated with prior biopsies for benign disease (p = 0.013), while age, parity and menopausal status were significant predictors of IGF-I/IGFBP-3 molar ratio. We conclude that circulating IGF-I levels are higher in women with prior breast cancer compared to unaffected women, and that IGF-I and/or IGFBP-3 levels are influenced by age and by reproductive and hormonal factors. These findings support their putative role as breast cancer risk biomarker.

A two-by-two factorial trial comparing oral with transdermal estrogen therapy and fenretinide with placebo on breast cancer biomarkers

PURPOSE

Oral conjugated equine estrogen (CEE) and medroxyprogesterone acetate (MPA) increase breast cancer risk, whereas the effect of transdermal estradiol (E2) and MPA is less known. Fenretinide may decrease second breast malignancies in premenopausal women but not in postmenopausal women, suggesting a hormone-sensitizing effect. We compared the 6 and 12-month changes in insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), IGF-I:IGFBP-3 ratio, sex-hormone binding-globulin, and computerized mammographic percent density during oral CEE or transdermal E2 with sequential MPA and fenretinide or placebo.

EXPERIMENTAL DESIGN

A total of 226 recent postmenopausal healthy women were randomly assigned in a two-by-two factorial design to either oral CEE 0.625 mg/day (n = 111) or transdermal E2, 50 microg/day (n = 115) and to fenretinide 100 mg/twice a day (n = 112) or placebo (n = 114) for 12 months. Treatment effects were investigated by the Kruskall-Wallis test and analysis of covariance. P values were two-sided.

RESULTS

After 12 months, oral CEE decreased IGF-I by 26% [95% confidence interval (CI), 22-30%] and increased sex-hormone binding-globulin by 96% (95% CI, 79-112%) relative to baseline, whereas no change occurred with transdermal E2 (P < 0.001 between groups). Fenretinide decreased IGFBP-3 relative to placebo (P = 0.04). Percentage of breast density showed an absolute increase of 3.5% (95% CI, 2.5-4.6%) during hormone therapy without differences between groups (P = 0.39).

CONCLUSIONS

Oral CEE has more favorable changes than transdermal E2 on circulating breast cancer risk biomarkers but gives similar effects on mammographic density. Fenretinide exerted little modulation on most biomarkers. The clinical implications of these findings require additional studies.

Cellular homeostasis and the breast

Increasing our knowledge regarding the control of cellular homeostasis in the normal human breast is important in understanding how breast tumours arise and whether compounds used for hormone replacement therapy are able to promote tumour formation In our studies on tissue from pre-menopausal, non-pregnant, non-lactating women, oestradiol is the main ovarian steroid mitogen for the breast epithelium whereas progesterone has little or no effect. Oestradiol appears to influence proliferative activity indirectly via oestrogen-receptor positive cells which control the activity of adjacent division competent cells by means of paracrine or juxtacrine growth factors. After the menopause, however, a mitogenic effect of progesterone becomes apparent which may be due to the reduction in endogenous oestradiol levels or, possibly, to tissue specific alterations in steroid sensitivity. Whatever the mechanism, the proliferative effects of progesterone on the post-menopausal breast have implications for the use of HRT.

Developmental changes in insulin-like growth factor I receptor gene expression in the mouse mammary gland

The insulin-like growth factor I receptor (IGF-IR), which mediates the mitogenic action of IGF-I, has been shown to play an essential role in normal growth and development. However, the precise role of IGF-IR in the growth and differentiation of the mammary gland has not been elucidated. This study examines the profile of the IGF-IR gene and protein expression during normal postnatal mammary gland development in order to gain further insight into the role of the IGF-I/IGF-IR during mammary gland morphogenesis. Gene and protein expression were examined in developing mouse mammary glands (virgin, pregnant, lactating, involuting) by real time PCR analysis and Western blotting. Both IGF-IR gene and protein expression levels were high during early pregnancy. Interestingly, the level of gene expression was significantly down-regulated during late pregnancy (5.4 fold) and lactation (9-13 fold) and significantly up-regulated (3.9 fold) during late involution, to the level observed in the virgin mammary gland. By in situ hybridization, the IGF-IR transcripts were localized to the proliferating ductal epithelium of the mammary glands of virgin mice and to the differentiating ductal and alveolar epithelium of the mammary glands during pregnancy and lactation. In the involuting gland, the transcripts were localized to the regressing ductal epithelium. These data are direct evidence that IGF-IR expression is important for alveolar cell proliferation and suggest that the progression of involution may require the down-regulation of IGF-IR gene expression. Altogether, these results demonstrate that a developmental IGF-IR gene expression pattern exists in the mouse mammary gland and that increases in gene expression at specific phases of development may reflect an important role for IGF-I/IGF-IR at those phases of development.

Steroid receptors and proliferation in the human breast

Despite recent gains in our knowledge of the hormonal control of proliferation and differentiation in the rodent mammary gland, the factors regulating these processes in the human are poorly understood. We have developed a model in which intact normal human breast tissue is grafted subcutaneously into adult female athymic nude mice and treated with oestrogen (E) and/or progesterone (P) at human physiological serum levels. We have shown that (i) E and not P is the major epithelial cell mitogen in the adult non-pregnant, non-lactating breast, (ii) E induces progesterone receptor (PR) expression and (iii) PR expression is maximally induced at low E concentrations while a higher amount of E is required to stimulate proliferation. These data raised the question of whether one cell type demonstrated two different responses to the two different E concentrations or whether PR expression and proliferation occurred in separate cell populations. Using dual label immunofluorescence, we showed that steroid receptor expression and proliferation (Ki67 antigen) are detected in separate cell populations in normal human breast epithelium, and that cells expressing the oestrogen receptor-alpha (ERalpha) invariably contained the PR. We also reported that this separation between steroid receptor expression and proliferation observed in the normal human epithelium is disrupted at an early stage in breast tumourigenesis. One interpretation supported by our recent findings is that some ERalpha/PR-positive epithelial cells are quiescent breast stem cells that act as "steroid hormone sensors". Such hormone sensor cells might secrete positive or negative paracrine/juxtacrine factors dependent on the prevailing E or P concentration to influence the proliferative activity of adjacent ERalpha/PR-negative epithelial cells.

Increase of free insulin-like growth factor-1 in normal human breast in vivo late in the menstrual cycle

Prolonged exposure to endogenous and exogenous sex steroids increases the risk of breast cancer but the mechanisms are poorly understood. Increased levels of circulating insulin-like growth factor-1 (IGF-1) and low levels of IGF binding protein are associated with increased risk of breast cancer suggesting that IGF-1 has to be in its free form to be biologically active. Little is known about sex steroid regulation of IGF-1 locally in the breast. In this study microdialysis was used to determine the local levels of free IGF-1 in normal human breast tissue in healthy female volunteers during the menstrual cycle. The results showed that the extracellular levels of free IGF-1 locally in the breast were doubled in the luteal phase, when estradiol and progesterone levels were elevated, compared with the follicular phase. In plasma, free IGF-1 levels also exhibited a cyclic variation but to a less extent. The increased local levels of the free form of IGF-1 may promote proliferation in the breast epithelium. This could be important in sex steroid dependent breast cancer development.

Variability of vascular endothelial growth factor in normal human breast tissue in vivo during the menstrual cycle

Exposure to sex steroids increases the risk of breast cancer, but the mechanisms are poorly understood. Angiogenesis is crucial in tumor development and progression. Very little is known about the regulation of angiogenesis in the normal breast. Vascular endothelial growth factor (VEGF) has a key stimulatory role in angiogenesis. Interferon-inducible protein 10 (IP-10) is a potent inhibitor of angiogenesis in vivo. These factors function in autocrine/paracrine pathways; therefore, direct measurements in the target tissue are needed. I measured VEGF and IP-10 in normal human breast tissue in situ in healthy women, using microdialysis, in the follicular and luteal phase of the menstrual cycle. In breast tissue, VEGF levels increased in the luteal phase, compared with the follicular phase (17.8 +/- 4 pg/ml to 34 +/- 9 pg/ml, P < 0.05). Plasma VEGF did not show a cyclic variation (10.6 +/- 2.8 pg/ml vs. 14.6 +/- 3.5 pg/liter, P = 0.3). IP-10 levels did not vary during the menstrual cycle either in breast tissue (65 +/- 17 pg/ml vs. 75 +/- 21 pg/ml, P = 0.6) or in plasma (64 +/- 7 pg/ml vs. 81 +/- 10 pg/ml, P = 0.06). The data suggests that, in the luteal phase, VEGF and IP-10, in the normal human breast, exhibit a proangiogenic profile. This may be one mechanism by which sex steroids contribute to breast cancer development.

Breast cancer prevention trials using retinoids

Retinoids have been studied as chemopreventive agents in clinical trials. Given their ability to inhibit mammary carcinogenesis in preclinical models. Fenretinide has extensively been investigated because of its favorable toxicological profile in humans. In a phase III secondary prevention trial, fenretinide showed a trend to a reduction of second breast malignancies in premenopausal women but not in postmenopausal women. This pattern was associated with a similar modulation of circulating IGF-I. A trend towards a reduction of ovarian cancer was also noted. Biomarker studies of fenretinide or novel selective retinoids alone and in combination with different nuclear receptor ligands are being conducted. These studies provide a model for testing the safety and tolerability, pharmacokinetics and pharmacodynamics, and biomarker modulation in high-risk women, and offer clues as to both the pathophysiology of carcinogenesis and the drug mechanisms of action, and help select new compounds and doses for testing in large randomized studies.

Molecular prognostic factors for breast cancer metastasis and survival

The biological characteristics of the tumor are used to estimate prognosis and select appropriate systemic therapy for patients with early-stage breast cancer. Well-established molecular prognostic factors include the estrogen and progesterone receptors, proliferation markers, and the HER2 gene. Novel tumor markers with potential clinical utility include molecules involved in cell transformation, invasion, and metastases. We review the available data supporting the utility of established prognostic and predictive molecular factors, and discuss challenges for integrating novel molecular markers into clinical practice.

Insulin-like growth factors and insulin-like growth factor binding proteins in mammary gland function

Insulin-like growth factor (IGF)-mediated proliferation and survival are essential for normal development in the mammary gland during puberty and pregnancy. IGFs interact with IGF-binding proteins and regulate their function. The present review focuses on the role of IGFs and IGF-binding proteins in the mammary gland and describes how modulation of their actions occurs by association with hormones, other growth factors and the extracellular matrix. The review will also highlight the involvement of the IGF axis in breast cancer.

Linkage between retinoid and fatty acid receptors: implications for breast cancer prevention

Certain dietary retinoids and polyunsaturated fatty acids (PUFAs) consistently inhibit progression of mammary carcinogenesis both in animal studies and cell culture, but clinically, their effect is inconsistent. New evidence of synergistic interaction between the nuclear receptors for the two groups of nutritional agents suggests that appropriate selective ligands from each group might be combined in breast cancer chemoprevention studies. Peroxisome proliferator-activated receptor (PPAR) gamma is a nuclear receptor that is activated by PUFAs, eicosanoids and antidiabetic agents such as troglitazone. Such activation can cause growth inhibition in human mammary cancer cells in culture and the effect is enhanced by ligands of retinoic acid receptor (RAR) and retinoid X receptor (RXR). In mouse mammary tissue in organ culture, an RXR-selective ligand has been shown to enhance the effect of troglitazone in suppressing carcinogen-induced pre-neoplastic changes. A PPAR/RXR heterodimer is involved in tumour growth inhibition and has been shown to bind directly to nuclear oestrogen response elements (ERE) independently of oestrogen receptor (ER) activity. A combination of an RXR-selective retinoid with either troglitazone or else a long-chain n-3 PUFA, is proposed for a short-term study in postmenopausal women after primary surgery for intraductal breast cancer. The resulting activation of PPAR/RXR expression may increase response to retinoid administration, especially in the presence of obesity and insulin resistance, because of the ability of PPAR gamma ligands to reduce insulin-like growth factor I (IGF-I) concentrations. Serial core biopsies of breast tissue over a short term are proposed to identify changes in phenotype, which may influence progression to invasiveness. In addition to cytomorphological criteria, expression of ER alpha and beta, RAR alpha and beta, and IGF-I receptor in the nucleus should be examined.

Upper abdominal obesity, insulin resistance and breast cancer risk

PURPOSE

A majority of prospective studies show breast cancer risk to be higher in obese postmenopausal women with upper abdominal adiposity than in those with overall adiposity. The evidence is more limited and inconsistent in the case of premenopausal women. The review examines evidence that aberrant insulin signalling may be involved in the promotion of mammary carcinogenesis. The aetiology and concomitants of abdominal visceral obesity are examined.

MECHANISMS

Clinical and experimental evidence suggests that the higher breast cancer risk associated with greater abdominal visceral obesity may be related to aberrant insulin signalling through the insulin receptor substrate 1 pathway, leading to insulin resistance, hyperinsulinaemia and increased concentrations of endogenous oestrogen and androgen. The putative role of aberrant insulin signalling in the promotion of mammary carcinogenesis may help to explain clinical relationships between breast cancer risk and age at menarche, pregnancies and onset of obesity.

CONCLUSION

Overall adiposity in women adversely affects breast cancer risk mainly by greater exposure of mammary epithelial tissue to endogenous oestrogen. Upper abdominal adiposity appears to involve an additional effect related to the presence of insulin resistance. Aetiological factors in the development of hyperinsulinaemic insulin resistance are still uncertain but may involve aberrant susceptibility genes in adipocyte insulin receptors or in the insulin receptor substrate 1 pathway. Epigenetic factors are also likely to contribute, including high free fatty acid levels and obesity. Dietary fatty acids, particularly polyunsaturated fatty acids, are known to regulate adipocyte differentiation through the nuclear peroxisome proliferator-activated receptor gamma, and may also have a role in insulin resistance. These aetiological factors are likely to be relevant to the high risk of postmenopausal breast cancer in industrialised Western populations.

Oestrogen/insulin-like growth factor-I receptor interaction in early breast cancer: clinical implications

The expression of oestrogen receptor (ER) and that of the insulin-like growth factor-I receptor (IGF-IR) are positively correlated in breast cancer specimens. Their function is strongly linked in enhancing proliferative activity in normal and malignant human mammary epithelial cells in culture. This review examines the likely role of such a mechanism in the increased breast cancer risk reported in postmenopausal women with abdominal obesity. Precancerous breast lesions show an increased proportion of ER-positive cells with high proliferative activity, and recent studies suggest that genetic mutations or epigenetic variants in the ER alpha gene may increase the ER's sensitivity to oestrogen stimulation. Abdominal obesity in women is associated with higher concentrations both of free oestradiol and free IGF-I. Activation of their respective receptors may induce synergistic stimulation of mammary carcinogenesis. However, there is clinical evidence that progression in precancerous breast lesions may be delayed or reversed. Involution occurs spontaneously in a proportion of duct carcinoma in situ (DCIS) (intraductal) lesions as women approach the menopause, and antioestrogen therapy has been shown to reduce recurrence and progression of DCIS lesions.

CONCLUSIONS

Intervention trials in breast cancer prevention would greatly benefit from surrogate response markers which could predict long-term benefit. Changes in ER and IGF-IR expression apart from those in standardised cytomorphological criteria, might predict the likelihood of DCIS involution in cancer prevention trials. Future studies could involve examination of serial core biopsies from normal breast tissue during trials of antioestrogens, retinoids or weight-reduction interventions. Correlation of changes in these markers with changes in circulating IGF-I and oestradiol concentrations may help to clarify the roles of the markers.

Insulin-like growth factors and insulin-like growth factor binding proteins in mammary gland function

Insulin-like growth factor (IGF)-mediated proliferation and survival are essential for normal development in the mammary gland during puberty and pregnancy. IGFs interact with IGF-binding proteins and regulate their function. The present review focuses on the role of IGFs and IGF-binding proteins in the mammary gland and describes how modulation of their actions occurs by association with hormones, other growth factors and the extracellular matrix. The review will also highlight the involvement of the IGF axis in breast cancer.

Effects of the anti-androgen finasteride on the modulatory actions of oestradiol on androgen metabolism by human gingival fibroblasts

5 alpha-Reduction of androgen substrates results in the formation of the biologically active androgen 5 alpha-dihydrotestosterone (DHT), while 17 beta-hydroxysteroid dehydrogenase metabolises androgen substrates to 4-androstenedione or testosterone. The aim here was to study the effect of the anti-androgen finasteride on 5 alpha-reduction of androgens by human gingival fibroblasts (HGF) and its modulation by oestradiol-17 beta. Duplicate cultures of HGF were incubated with [14C]testosterone/[14C]4-androstenedione in Eagle minimum essential medium (n=6) in the presence or absence of oestradiol-17 beta (O) or finasteride (F; 0.1-3 microg/ml) for 24 h. The steroid metabolites were analysed and quantified using a radioisotope scanner. With [14C]testosterone as substrate, oestradiol stimulated the formation of DHT by 63% (n=6; P<0.01). In contrast, finasteride inhibited this activity by 61% (n=6; P<0.01). The combination of O+F produced 43% less inhibition than finasteride alone (n=6; P<0.01). There were 200-300% increases in the formation of 4-androstenedione in response to O and F, being less pronounced in combination. Oestradiol stimulated the formation of DHT from [14C]4-androstenedione by 300-600% and finasteride reduced the yield of DHT by 40-64%; there was less inhibition in combination with O. There were 300-700% increases in the formation of testosterone in response to F and O alone and in combination (n=6; P<0.01). Oestradiol-induced stimulation of 5 alpha-reductase activity on androgen substrates by HGF is suggestive of hormone modulatory mechanisms in the healing periodontium of both sexes. Its inhibition by finasteride is suggestive of type 2 isoenzyme activity, confirming target-tissue functions in the gingiva.

Primate mammary gland insulin-like growth factor system: cellular localization and regulation by sex steroids

BACKGROUND

Insulin-like growth factor 1 (IGF1) plays a critical role in estrogen-induced uterine proliferation, but it is unclear whether this estromedin function occurs in other estrogen-sensitive tissues such as the mammary gland. To elucidate this possibility, we investigated the cellular localization and hormonal regulation of mRNAs for IGF1 and 2, their cognate receptors (IGF1R, IGF2R), and IGF binding proteins 2-5 (BPs 2-5) in the rhesus monkey mammary gland.

METHODS

Ovariectomized monkeys were treated with placebo, estradiol (E2), and E2 plus progesterone (E2/P4) for 3 days, after which mammary tissue was harvested for in situ hybridization and immunohistochemical analyses.

RESULTS

IGF1 and IGF2 mRNA levels were significantly increased and BP2 mRNA decreased by E2 and by E2/P4 treatment. IGF1R mRNA was increased by combined E2/P treatment but not by E2 alone. BP5 mRNA was decreased by E2/P4. No differences in IGF2R, BP3, and BP4 mRNA levels were detected in any treatment group. Mammary IGF1 and IGF2 mRNA levels were both positively correlated with local epithelial proliferation, assessed by immunodetection of the proliferation-specific antigen, Ki67.IGF1 and IGF1R expression were negatively correlated with local programmed cell death, as assessed by the in situ TUNEL method. In contrast, BP2 expression was negatively correlated with epithelial proliferation and positively correlated with programmed cell death. IGF2R, BP3, BP4, and BP5 levels were not significantly correlated with either proliferation or death.

CONCLUSIONS

Thus, E2-induced proliferation is associated with upregulation of both IGF1 and IGF2 expression and downregulation of BP2 expression. These data suggest that the local mammary IGF system is involved in sex steroid-induced mammary epithelial cell hyperplasia.

Xenograft models of premalignant breast disease

Dysplastic and hyperplastic proliferative lesions with graded severity of atypia are recognized in a number of tissues and are generally suspected to be premalignant, that is to say at high risk for further progressing to carcinoma in situ and invasive cancer. However, few xenograft models of premalignancy for any organ site have been successfully developed. A good model of human premalignant breast disease would lead to lesions which resemble high risk human breast disease in xenografts and sporadically progress to invasive cancer with time. In this chapter the use of breast tissue pieces and epithelial cells for establishment of xenografts and the development of human breast epithelial cell lines that form premalignant xenograft lesions are described. MCF10AT cells not only form simple differentiated ducts which persist in xenografts and sporadically progress to carcinoma, but also form intermediate proliferative lesions resembling proliferative disease without atypia, atypical hyperplasia, and carcinoma in situ.

A quantitative reverse transcription and polymerase chain reaction assay for human IGF-II allows direct comparison of IGF-II mRNA levels in cancerous breast, bladder, and prostate tissues

Previously, we showed by in situ hybridization that insulin-like growth factor (IGF)-II is upregulated in approximately 50% of prostate, breast, and bladder tumours. In this study, a quantitative competitive reverse transcription and polymerase chain reaction (QC RT-PCR) assay was established and used to quantify human IGF-II mRNA levels in cells and tissues. In this QC RT-PCR assay, a competitor IGF-II RNA, prepared from a newly constructed plasmid encoding the human IGF-II sequence with a 110-bp fragment inserted, was added to RNA samples prior to RT-PCR. The human IGF-II specific QC RT-PCR assay has allowed us to readily compare the levels of IGF-II mRNA in human tissues and cultured cells. Consistent with our previous observations by in situ hybridization, IGF-II mRNA was up-regulated in 50% of cancerous breast tissues examined as compared to the matching benign tissues, and IGF-II mRNA levels were higher in bladder tumours than breast and prostate tumours. In summary, we present here quantitative data confirming that a subclass of breast cancer samples has elevated levels of IGF-II transcripts by the new competitive RT-PCR assay.

Expression of sex steroid receptors and IGF-1 mRNA in breast tissue--effects of hormonal treatment

The mechanisms behind increased breast tissue proliferation and a possibly increased breast cancer risk in women using hormonal contraception (HC) and hormonal replacement therapy (HRT) are incompletely understood. We analyzed breast tissue from 20 premenopausal and seven postmenopausal women undergoing reduction mammoplasties for estrogen receptor (ER) and progesterone receptor (PR) content as well as mRNA levels for ER, PR and insulin-like growth factor-1 (IGF-1). The receptor values were correlated to IGF-1 mRNA concentrations and levels of steroid and peptide hormones and SHBG. In women using HC, we found significantly lower ER values (p = 0.02) but non-significantly lower ER mRNA levels compared to those in naturally cycling women. PR and PR mRNA were no different. Women on HC displayed a higher breast tissue proliferation (p = 0.05) expressed as Ki-67, MIB-1 positivity, which was correlated with IGF-1 mRNA (r(s) = 0.82, p = 0.04). Since the concentration of sex steroid receptors in breast tissue is comparatively low and steroid receptors are down-regulated during hormonal treatment, mechanisms other than direct sex steroid receptor action are likely to be present. Our results suggest a role for IGF-1 in the proliferative response of breast tissue during exogenous hormonal treatment.

Modulation of androgen metabolism by estradiol-17beta and progesterone, alone and in combination, in human gingival fibroblasts in culture

BACKGROUND

Androgens, particularly 5alpha-dihydrotestosterone (DHT), have anabolic effects on connective tissues and bone with implications on periodontal healing. This can be enhanced by estradiol-17beta (E-17beta), in synergy with androgen action. The effects of progesterone (P) contribute to plaque-induced inflammatory changes. The aim of this investigation was to study the modulation of androgen metabolism by E-17beta and P, alone and in combination.

METHODS

Human gingival fibroblasts were established in monolayer culture and duplicate incubations were performed in Eagle's MEM for 24 hours with either 14C-testosterone (14C-T) or 14C-4-androstenedione (14C-4-A) as substrate and serial concentrations of E-17beta, P and E-17beta + P. The medium was solvent extracted for steroid metabolites, analyzed, and quantified using a radioisotope scanner. The androgen substrates were converted mainly to DHT and 4-androstenedione/testosterone from 14C-T and 14C-4-A respectively.

RESULTS

At concentrations of 0.1 and 0.5 microg/ml, E-17beta stimulated DHT synthesis from 14C-T by 18% and 12%, respectively, decreasing to control values at 0.1 microg/ml. While the effect of similar concentrations of P on the same substrates was inhibitory by 18, 70, and 82% (n = 4; P <0.01). E-17beta + P showed a 12% increase in DHT synthesis over controls at 0.1 microg/ml, similar to that of E-17beta alone, despite the inhibitory effects of P (n = 4; P <0.01) with 12% and 77% decreases at 0.5 and 1 microg/ml (n = 4; P <0.01). The inhibitory effect of P on DHT synthesis was less apparent when E-17beta was present in combination. The formation of 4-androstenedione from 14C-T was stimulated by E-17beta (12.5%), inhibited by P (50%) and showed an intermediate response with E + P (33% stimulation). At the concentrations used, E-17beta stimulated DHT synthesis from 14C-4-A by 3.6-, 3- and 2.6-fold. P also stimulated this conversion from the same substrate by 16%, 2-fold, and 1.6-fold increases, partly due to the low yields at baseline. The combination of E + P stimulated the synthesis of DHT from 14C-4-A by 4-fold at 0.1 and 0.5 microg/ml and a 2.3-fold increase at 1 microg/ml. The formation of T from 14C-4-A was stimulated by E-17beta (50%) and inhibited by P (40%), with 93% stimulation by E + P at 0.1 microg/ml.

CONCLUSIONS

The modulatory effects of estradiol-17beta and progesterone on androgen metabolism may influence disease presentation and the progress of healing responses in the inflamed periodontium.

The insulin-like growth factor (IGF) system and gonadotropin regulation: actions and interactions

Insulin-like growth factors (IGF) are polypeptides that regulate growth, differentiation and survival in a multitude of cells and tissues. The IGF system consists of ligands, receptors, binding proteins and binding protein proteases. The influence of the IGF system on reproductive parameters, specifically gonadotropin release and interactions between the IGF system and other effectors of gonadotropin release will be examined in this review.