Effect of sodium butyrate on estrogen receptor and epidermal growth factor receptor gene expression in human breast cancer cell lines

HDAC inhibitors modulate Hippo pathway signaling in hormone positive breast cancer

Breast cancer has constantly been the leading causes of death in women, and hormone receptor (HR) positive, HER2 negative is the majority subtype. Histone deacetylase (HDAC) inhibitors (HDACi) have shown clinical benefit in HR ( +) breast cancer patients. The Hippo pathway is an important cellular pathway involving proliferation, cell contact, and cancer. Hippo pathway proteins YAP/TAZ are often viewed as pro-tumorigenic; however, recent studies support a role of YAP as a tumor suppressor in HR ( +) breast cancer. Few studies have investigated the link between HDACi and the Hippo pathway. In our study, we demonstrate that HDACi induces transcriptional downregulation of YAP expression, while conversely activating a TEAD-mediated transcriptional program with upregulation of canonical Hippo pathway genes. We subsequently identified four Hippo canonical genes (CCDC80, GADD45A, F3, and TGFB2) that were upregulated by HDACi and associated with significantly improved survival in a HR ( +) breast cancer cohort. We further validated experimentally that HR ( +) breast cancer cells treated with HDACi resulted in upregulation of CCDC80 and GADD45A. A pan-cancer analysis of TCGA database demonstrated lower CCDC80 and GADD45A expression in tumor tissue compared to non-tumor samples in BRCA (breast cancer), LAML (acute myeloid leukemia), and UCS (uterine carcinosarcoma). Further analysis of HR ( +) breast cancer patients in the METABRIC dataset revealed high CCDC80 and/or GADD45A expression associated with significantly better survival outcomes compared to patients with low expression. Our study provides evidence for a novel mechanism of HDACi clinical activity, as well as a potential role for CCDC80 and GADD45A in HR ( +) breast cancer.

From Gut to Brain: The Impact of Short-Chain Fatty Acids on Brain Cancer

The primary source of short-chain fatty acids (SCFAs), now recognized as critical mediators of host health, particularly in the context of neurobiology and cancer development, is the gut microbiota's fermentation of dietary fibers. Recent research highlights the complex influence of SCFAs, such as acetate, propionate, and butyrate, on brain cancer progression. These SCFAs impact immune modulation and the tumor microenvironment, particularly in brain tumors like glioma. They play a critical role in regulating cellular processes, including apoptosis, cell differentiation, and inflammation. Moreover, studies have linked SCFAs to maintaining the integrity of the blood-brain barrier (BBB), suggesting a protective role in preventing tumor infiltration and enhancing anti-tumor immunity. As our understanding of the gut-brain axis deepens, it becomes increasingly important to investigate SCFAs' therapeutic potential in brain cancer management. Looking into how SCFAs affect brain tumor cells and the environment around them could lead to new ways to prevent and treat these diseases, which could lead to better outcomes for people who are dealing with these challenging cancers.

Butyrate as a Potential Modulator in Gynecological Disease Progression

This review investigates the therapeutic potential of butyrate, a short-chain fatty acid (SCFA) produced by gut microbiota, in the prevention and treatment of various gynecological diseases, including polycystic ovary syndrome (PCOS), endometriosis, and gynecologic cancers like cervical and ovarian cancer. These conditions often pose treatment challenges, with conventional therapies offering limited and temporary relief, significant side effects, and a risk of recurrence. Emerging evidence highlights butyrate's unique biological activities, particularly its role as a histone deacetylase (HDAC) inhibitor, which allows it to modulate gene expression, immune responses, and inflammation. In PCOS, butyrate aids in restoring hormonal balance, enhancing insulin sensitivity, and reducing chronic inflammation. For endometriosis, butyrate appears to suppress immune dysregulation and minimize lesion proliferation. Additionally, in cervical and ovarian cancers, butyrate demonstrates anticancer effects through mechanisms such as cell cycle arrest, apoptosis induction, and suppression of tumor progression. Dietary interventions, particularly high-fiber and Mediterranean diets, that increase butyrate production are proposed as complementary approaches, supporting natural microbiota modulation to enhance therapeutic outcomes. However, butyrate's short half-life limits its clinical application, spurring interest in butyrate analogs and probiotics to maintain stable levels and extend its benefits. This review consolidates current findings on butyrate's multifaceted impact across gynecological health, highlighting the potential for microbiota-centered therapies in advancing treatment strategies and improving women's reproductive health.

Uncovering a novel mechanism: Butyrate induces estrogen receptor alpha activation independent of estrogen stimulation in MCF-7 breast cancer cells

Butyrate is a promising candidate for an antitumoral drug, as it promotes cancer cell apoptosis and reduces hormone receptor activity, while promoting differentiation and proliferation in normal cells. However, the effects of low-dose butyrate on breast cancer cell cultures are unclear. We explored the impact of sub-therapeutic doses of butyrate on estrogen receptor alpha (ERα) transcriptional activity in MCF-7 cells, using RT-qPCR, Western blot, wound-healing assays, and chromatin immunoprecipitation. Our results showed that sub-therapeutic doses of sodium butyrate (0.1 - 0.2 mM) increased the transcription of ESR1, TFF1, and CSTD genes, but did not affect ERα protein levels. Moreover, we observed an increase in cell migration in wound-healing assays. ChIP assays revealed that treatment with 0.1 mM of sodium butyrate resulted in estrogen-independent recruitment of ERα at the pS2 promoter and loss of NCoR. Appropriate therapeutic dosage of butyrate is essential to avoid potential adverse effects on patients' health, especially in the case of estrogen receptor-positive breast tumors. Sub-therapeutic doses of butyrate may induce undesirable cell processes, such as migration due to low-dose butyrate-mediated ERα activation. These findings shed light on the complex effects of butyrate in breast cancer and provide insights for research in the development of antitumoral drugs.

A Comparative Study of Serum Butyric Acid in Subjects with Tongue Cancer

Aim:

The aim of the study was to study the level of butyric acid in tongue cancer subjects.

Materials and Methods:

Thirty controls and 30 tongue cancer subjects were recruited for the study. Serum butyric acid levels were estimated using ELISA kits. Statistical analyses were done using SPSS vs 22. The Mann–Whitney U and Kruskal–Wallis tests were used. P ≤ 0.05 was considered statistically significant.

Results:

Butyric acid levels were significantly higher in control subjects when compared to case subjects.

Conclusion:

Butyric acid could be used as a potential anticancer agent in tongue cancer treatment.

Short-chain fatty acids in cancer pathogenesis

Cancer is a multi-step process that can be viewed as a cellular and immunological shift away from homeostasis in response to selected infectious agents, mutations, diet, and environmental carcinogens. Homeostasis, which contributes importantly to the definition of "health," is maintained, in part by the production of short-chain fatty acids (SCFAs), which are metabolites of specific gut bacteria. Alteration in the composition of gut bacteria, or dysbiosis, is often a major risk factor for some two dozen tumor types. Dysbiosis is often characterized by diminished levels of SCFAs in the stool, and the presence of a "leaky gut," permitting the penetration of microbes and microbial derived molecules (e.g., lipopolysaccharides) through the gut wall, thereby triggering chronic inflammation. SCFAs attenuate inflammation by inhibiting the activation of nuclear factor kappa B, by decreasing the expression of pro-inflammatory cytokines such as tumor necrosis factor alpha, by stimulating the expression of anti-inflammatory cytokines such as interleukin-10 and transforming growth factor beta, and by promoting the differentiation of naïve T cells into T regulatory cells, which down-regulate immune responses by immunomodulation. SCFA function epigenetically by inhibiting selected histone acetyltransferases that alter the expression of multiple genes and the activity of many signaling pathways (e.g., Wnt, Hedgehog, Hippo, and Notch) that contribute to the pathogenesis of cancer. SCFAs block cancer stem cell proliferation, thereby potentially delaying or inhibiting cancer development or relapse by targeting genes and pathways that are mutated in tumors (e.g., epidermal growth factor receptor, hepatocyte growth factor, and MET) and by promoting the expression of tumor suppressors (e.g., by up-regulating PTEN and p53). When administered properly, SCFAs have many advantages compared to probiotic bacteria and fecal transplants. In carcinogenesis, SCFAs are toxic against tumor cells but not to surrounding tissue due to differences in their metabolic fate. Multiple hallmarks of cancer are also targets of SCFAs. These data suggest that SCFAs may re-establish homeostasis without overt toxicity and either delay or prevent the development of various tumor types.

Rapid identification of sepsis in the emergency department

Objectives

Recent research has helped define the complex pathways in sepsis, affording new opportunities for advancing diagnostics tests. Given significant advances in the field, a group of academic investigators from emergency medicine, intensive care, pathology, and pharmacology assembled to develop consensus around key gaps and potential future use for emerging rapid host response diagnostics assays in the emergency department (ED) setting.

Methods

A modified Delphi study was conducted that included 26 panelists (expert consensus panel) from multiple specialties. A smaller steering committee first defined a list of Delphi statements related to the need for and future potential use of a hypothetical sepsis diagnostic test in the ED. Likert scoring was used to assess panelists agreement or disagreement with statements. Two successive rounds of surveys were conducted and consensus for statements was operationally defined as achieving agreement or disagreement of 75% or greater.

Results

Significant gaps were identified related to current tools for assessing risk of sepsis in the ED. Strong consensus indicated the need for a test providing an indication of the severity of dysregulated host immune response, which would be helpful even if it did not identify the specific pathogen. Although there was a relatively high degree of uncertainty regarding which patients would most benefit from the test, the panel agreed that an ideal host response sepsis test should aim to be integrated into ED triage and thus should produce results in less than 30 minutes. The panel also agreed that such a test would be most valuable for improving sepsis outcomes and reducing rates of unnecessary antibiotic use.

Conclusion

The expert consensus panel expressed strong consensus regarding gaps in sepsis diagnostics in the ED and the potential for new rapid host response tests to help fill these gaps. These finding provide a baseline framework for assessing key attributes of evolving host response diagnostic tests for sepsis in the ED.

Butyrate mitigates metabolic dysfunctions via the ERα-AMPK pathway in muscle in OVX mice with diet-induced obesity

The higher prevalence of metabolic syndrome (MetS) in women after menopause is associated with a decrease in circulating 17β-oestradiol. To explore novel treatments for MetS in women with oestrogen deficiency, we studied the effect of exogenous butyrate on diet-induced obesity and metabolic dysfunctions using ovariectomized (OVX) mice as a menopause model. Oral administration of sodium butyrate (NaB) reduced the body fat content and blood lipids, increased whole-body energy expenditure, and improved insulin sensitivity. Additionally, NaB induced oestrogen receptor alpha (ERα) expression, activated the phosphorylation of AMPK and PGC1α, and improved mitochondrial aerobic respiration in cultured skeletal muscle cells. In conclusion, oral NaB improves metabolic parameters in OVX mice with diet-induced obesity. Oral supplementation with NaB might provide a novel therapeutic approach to treating MetS in women with menopause. Video Abstract.

Mechanistic basis and preliminary practice of butyric acid and butyrate sodium to mitigate gut inflammatory diseases: a comprehensive review

A key event featured in the early stage of chronic gut inflammatory diseases is the disordered recruitment and excess accumulation of immune cells in the gut lamina propria. This process is followed by the over-secretion of pro-inflammatory factors and the prolonged overactive inflammatory responses. Growing evidence has suggested that gut inflammatory diseases may be mitigated by butyric acid (BA) or butyrate sodium (NaB). Laboratory studies show that BA and NaB can enhance gut innate immune function through G-protein-mediated signaling pathways while mitigating the overactive inflammatory responses by inhibiting histone deacetylase. The regulatory effects may occur in both epithelial enterocytes and the immune cells in the lamina propria. Prior to further clinical trials, comprehensive literature reviews and rigid examination concerning the underlying mechanism are necessary. To this end, we collected and reviewed 197 published reports regarding the mechanisms, bioactivities, and clinical effects of BA and NaB to modulate gut inflammatory diseases. Our review found insufficient evidence to guarantee the safety of clinical practice of BA and NaB, either by anal enema or oral administration of capsule or tablet. The safety of clinical use of BA and NaB should be further evaluated. Alternatively, dietary patterns rich in "fruits, vegetables and beans" may be an effective and safe approach to prevent gut inflammatory disease, which elevates gut microbiota-dependent production of BA. Our review provides a comprehensive reference to future clinical trials of BA and NaB to treat gut inflammatory diseases.

The culture conditions and outputs from breast cancer cell line in vitro experiments

One of the major cancer types that have gained significant importance globally is the breast cancer due to its socio-economic impact. Breast cancer research is an area of considerable importance and several types of material are available for research applications. These include cancer cell lines which can be utilized in several ways. Cell lines are convenient to use and recently about 84 human breast cancer cell lines were classified by molecular sub-typing. These cells lines come under five major molecular subtypes namely the luminal A and B, HER-2⁺, triple^- A and B subtypes. These cell lines have been well characterized and were utilized for understanding various aspects of breast cancers. Also, apart from providing an understanding of the molecular mechanisms associated with breast cancers, these cell lines have contributed significantly to areas such as drug testing. We present in this review the features of these cell lines, the studies conducted using them and the outcome of such studies. Also, the details about the culture conditions and study outcomes of the cell lines grown in 3-dimensional (3D) systems are presented.

Combined histone deacetylase inhibition and tamoxifen induces apoptosis in tamoxifen-resistant breast cancer models, by reversing Bcl-2 overexpression

INTRODUCTION

The emergence of hormone therapy resistance, despite continued expression of the estrogen receptor (ER), is a major challenge to curing breast cancer. Recent clinical studies suggest that epigenetic modulation by histone deacetylase (HDAC) inhibitors reverses hormone therapy resistance. However, little is known about epigenetic modulation of the ER during acquired hormone resistance. Our recent phase II study demonstrated that HDAC inhibitors re-sensitize hormone therapy-resistant tumors to the anti-estrogen tamoxifen. In this study, we sought to understand the mechanism behind the efficacy of this combination.

METHODS

We generated cell lines resistant to tamoxifen, named TAMRM and TAMRT, by continuous exposure of ER-positive MCF7 and T47D cells, respectively to 4-hydroxy tamoxifen for over 12 months. HDAC inhibition, along with pharmacological and genetic manipulation of key survival pathways, including ER and Bcl-2, were used to characterize these resistant models.

RESULTS

The TAMRM cells displayed decreased sensitivity to tamoxifen, fulvestrant and estrogen deprivation. Consistent with previous models, ER expression was retained and the gene harbored no mutations. Compared to parental MCF7 cells, ER expression in TAMRM was elevated, while progesterone receptor (PGR) was lost. Sensitivity of ER to ligands was greatly reduced and classic ER response genes were suppressed. This model conveyed tamoxifen resistance through transcriptional upregulation of Bcl-2 and c-Myc, and downregulation of the cell cycle checkpoint protein p21, manifesting in accelerated growth and reduced cell death. Similar to TAMRM cells, the TAMRT cell line exhibited substantially decreased tamoxifen sensitivity, increased ER and Bcl-2 expression and significantly reduced PGR expression. Treatment with HDAC inhibitors reversed the altered transcriptional events and reestablished the sensitivity of the ER to tamoxifen resulting in substantial Bcl-2 downregulation, growth arrest and apoptosis. Selective inhibition of Bcl-2 mirrored these effects in presence of an HDAC inhibitor.

CONCLUSIONS

Our model implicates elevated ER and Bcl-2 as key drivers of anti-estrogen resistance, which can be reversed by epigenetic modulation through HDAC inhibition.

The niacin/butyrate receptor GPR109A suppresses mammary tumorigenesis by inhibiting cell survival

GPR109A, a G-protein-coupled receptor, is activated by niacin and butyrate. Upon activation in colonocytes, GPR109A potentiates anti-inflammatory pathways, induces apoptosis, and protects against inflammation-induced colon cancer. In contrast, GPR109A activation in keratinocytes induces flushing by activation of Cox-2-dependent inflammatory signaling, and the receptor expression is upregulated in human epidermoid carcinoma. Thus, depending on the cellular context and tissue, GPR109A functions either as a tumor suppressor or a tumor promoter. However, the expression status and the functional implications of this receptor in the mammary epithelium are not known. Here, we show that GPR109A is expressed in normal mammary tissue and, irrespective of the hormone receptor status, its expression is silenced in human primary breast tumor tissues, breast cancer cell lines, and in tumor tissues of three different murine mammary tumor models. Functional expression of this receptor in human breast cancer cell lines decreases cyclic AMP production, induces apoptosis, and blocks colony formation and mammary tumor growth. Transcriptome analysis revealed that GPR109A activation inhibits genes, which are involved in cell survival and antiapoptotic signaling, in human breast cancer cells. In addition, deletion of Gpr109a in mice increased tumor incidence and triggered early onset of mammary tumorigenesis with increased lung metastasis in MMTV-Neu mouse model of spontaneous breast cancer. These findings suggest that GPR109A is a tumor suppressor in mammary gland and that pharmacologic induction of this gene in tumor tissues followed by its activation with agonists could be an effective therapeutic strategy to treat breast cancer.

HDAC3 regulates stability of estrogen receptor α mRNA

Estrogen receptor alpha (ERα) expression is a risk factor for breast cancer. HDAC inhibitors have been demonstrated to down-regulate ERα expression in ERα-positive breast cancer cell lines, but the molecular mechanisms are poorly understood. Here, we showed that HDAC inhibitors decrease the stability of ERα mRNA, and that knockdown of HDAC3 decreases the stability of ERα mRNA and suppresses estrogen-dependent proliferation of ERα-positive MCF-7 breast cancer cells. In the Oncomine database, expression levels of HDAC3 in ERα-positive tumors are higher than those in ERα-negative tumors, thus suggesting that HDAC3 is necessary for ERα mRNA stability, and is involved in the estrogen-dependent proliferation of ERα-positive tumors.

Fatty acids derived from royal jelly are modulators of estrogen receptor functions

Royal jelly (RJ) excreted by honeybees and used as a nutritional and medicinal agent has estrogen-like effects, yet the compounds mediating these effects remain unidentified. The possible effects of three RJ fatty acids (FAs) (10-hydroxy-2-decenoic-10H2DA, 3,10-dihydroxydecanoic-3,10DDA, sebacic acid-SA) on estrogen signaling was investigated in various cellular systems. In MCF-7 cells, FAs, in absence of estradiol (E₂), modulated the estrogen receptor (ER) recruitment to the pS2 promoter and pS2 mRNA levels via only ERβ but not ERα, while in presence of E₂ FAs modulated both ERβ and ERα. Moreover, in presence of FAs, the E₂-induced recruitment of the EAB1 co-activator peptide to ERα is masked and the E₂-induced estrogen response element (ERE)-mediated transactivation is inhibited. In HeLa cells, in absence of E₂, FAs inhibited the ERE-mediated transactivation by ERβ but not ERα, while in presence of E₂, FAs inhibited ERE-activity by both ERβ and ERα. Molecular modeling revealed favorable binding of FAs to ERα at the co-activator-binding site, while binding assays showed that FAs did not bind to the ligand-binding pocket of ERα or ERβ. In KS483 osteoblasts, FAs, like E₂, induced mineralization via an ER-dependent way. Our data propose a possible molecular mechanism for the estrogenic activities of RJ's components which, although structurally entirely different from E₂, mediate estrogen signaling, at least in part, by modulating the recruitment of ERα, ERβ and co-activators to target genes.

Manipulating protein acetylation in breast cancer: a promising approach in combination with hormonal therapies?

Estrogens play an essential role in the normal physiology of the breast as well as in mammary tumorigenesis. Their effects are mediated by two nuclear estrogen receptors, ERα and β, which regulate transcription of specific genes by interacting with multiprotein complexes, including histone deacetylases (HDACs). During the past few years, HDACs have raised great interest as therapeutic targets in the field of cancer therapy. In breast cancer, several experimental arguments suggest that HDACs are involved at multiple levels in mammary tumorigenesis: their expression is deregulated in breast tumors; they interfere with ER signaling in intricate ways, restoring hormone sensitivity in models of estrogen resistance, and they clinically represent new potential targets for HDACs inhibitors (HDIs) in combination with hormonal therapies. In this paper, we will describe these different aspects and underline the clinical interest of HDIs in the context of breast cancer resistance to hormone therapies (HTs).

Short-chain fatty acids and trichostatin A alter tight junction permeability in human umbilical vein endothelial cells

OBJECTIVE

The short-chain fatty acids (SCFAs), butyrate, propionate, and acetate, produced by bacterial fermentation of dietary fiber, can modulate the transcription of certain genes by inhibiting histone deacetylase in colonocytes and several other cell types in vitro. We previously reported that butyrate decreases tight junction permeability by activating lipoxygenase (LOX) in intestinal monolayer cells. In the present study, we evaluated the effects of SCFAs on tight junction permeability in an endothelial cell culture and their possible mechanisms of action via histone deacetylase inhibitor activity. We also investigated the factors modulating tight junction permeability.

METHODS

The effects of butyrate, propionate, and acetate on tight junction permeability in human umbilical vein endothelial cells were examined using Transwell chamber cultures. The contributions of inducible nitric oxide synthase (NOS), endothelial NOS, estrogen receptor, cyclo-oxygenase, and LOX to SCFAs' effects were also evaluated. The effects of SCFAs were compared with those of trichostatin A, a typical histone deacetylase inhibitor.

RESULTS

Low concentrations of butyrate and propionate decreased paracellular permeability without inducing cell damage. However, acetate decreased paracellular permeability in a concentration-dependent manner. An estrogen receptor antagonist attenuated the effects of SCFAs on tight junction permeability. The influences of inducible NOS, cyclo-oxygenase, and LOX inhibitors and the expressions of cyclo-oxygenase and LOX mRNAs were different for each SCFA. Trichostatin A slightly decreased paracellular permeability when used at lower concentrations, but higher concentrations of trichostatin A increased permeability.

CONCLUSION

The SCFAs play an important role in the assembly of tight junctions in normal vascular endothelial cells.

Visualization of polarized membrane type 1 matrix metalloproteinase activity in live cells by fluorescence resonance energy transfer imaging

Membrane type 1 matrix metalloproteinase (MT1-MMP) plays a critical role in cancer cell biology by proteolytically remodeling the extracellular matrix. Utilizing fluorescence resonance energy transfer (FRET) imaging, we have developed a novel biosensor, with its sensing element anchoring at the extracellular surface of cell membrane, to visualize MT1-MMP activity dynamically in live cells with subcellular resolution. Epidermal growth factor (EGF) induced significant FRET changes in cancer cells expressing MT1-MMP, but not in MT1-MMP-deficient cells. EGF-induced FRET changes in MT1-MMP-deficient cells could be restored after reconstituting with wild-type MT1-MMP, but not MMP-2, MMP-9, or inactive MT1-MMP mutants. Deletion of the transmembrane domain in the biosensor or treatment with tissue inhibitor of metalloproteinase-2, a cell-impermeable MT1-MMP inhibitor, abolished the EGF-induced FRET response, indicating that MT1-MMP acts at the cell surface to generate FRET changes. In response to EGF, active MT1-MMP was directed to the leading edge of migrating cells along micropatterned fibronectin stripes, in tandem with the local accumulation of the EGF receptor, via a process dependent upon an intact cytoskeletal network. Hence, the MT1-MMP biosensor provides a powerful tool for characterizing the molecular processes underlying the spatiotemporal regulation of this critical class of enzymes.

Colocalization of somatostatin receptors and epidermal growth factor receptors in breast cancer cells

BACKGROUND

Somatostatin receptor (SSTR) expression is positively correlated with tumor size and inversely correlated with epidermal growth factor receptor (ErbB) levels and tumor differentiation. In the present study, we compared SSTR1-5 and ErbB1-4 mRNA and protein expression in two breast cancer cell lines: MCF-7 (ER+) and MDA-MB-231 (ERalpha-).

RESULTS

All five SSTRs and four ErbBs were variably expressed as both cell surface and cytoplasmic proteins. In both cell lines, SSTR4 and SSTR1 were highly expressed, followed by SSTR2 and SSTR5 with SSTR3 being the least expressed subtype, at the protein level. ErbBs were variably expressed with ErbB1 as the predominant subtype in both cell lines. ErbB1 is followed by ErbB3, ErbB2 and ErbB4 in MCF-7 at both the protein and mRNA levels. In MDA-MB-231 cells, ErbB1 is followed by ErbB2, ErbB4 and ErbB3. Our results indicate significant correlations at the level of mRNA and protein expression in a cell and receptor-specific manner. Using indirect immunofluorescence, we found that, in MCF-7 cells, SSTR5 was the most prominent subtype coexpressed with ErbBs followed by SSTR3, SSTR4, SSTR1 and SSTR2, respectively. In MDA-MB-231 cells, SSTR1 colocalized strongly with ErbBs followed by SSTR5, SSTR4, SSTR3 and SSTR2. ErbBs displayed higher levels of colocalization amongst themselves in MCF-7 cells than in MDA-MB-231 cells.

CONCLUSION

These findings may explain the poor response to endocrine therapy in ER-cancer. Differential distribution of SSTR subtypes with ErbBs in breast cancer cells in a receptor-specific manner may be considered as a novel diagnosis for breast tumors.

Histone deacetylase inhibition and estrogen signalling in human breast cancer cells

Estrogens are steroid hormones, which act through specific nuclear estrogen receptors (ERalpha and ERbeta) and are important regulators of breast cancer growth. These receptors control gene expression by recruiting transcriptional cofactors that exhibit various enzymatic activities such as histone acetyltransferase or histone deacetylase (HDAC) which target histone as well as non-histone substrates. The ERalpha itself and some of the transcriptional regulators have been shown to be acetylated proteins. Research performed over the last decade has highlighted the role of HDAC inhibitors (HDACi) as modulators of transcriptional activity and as a new class of therapeutic agents. In human cancer cells, inhibition of HDACs controls the expression of the ERalpha gene and the transcriptional activity in response to partial antiestrogens such as 4-hydroxytamoxifen. Various HDACi strongly inhibit breast cancer cell proliferation and ERalpha-negative (ER-) appear less sensitive than ERalpha-positive (ER+) cell lines. p21WAF1/CIP1 gene expression, in relation with ERalpha levels, could play a role in this differential response of breast cancer cells to hyperacetylating agents.

Estrogen/EGF receptor interactions in breast cancer: rationale for new therapeutic combination strategies

In the therapy of estrogen receptor (ER) positive human mammary carcinomas, the treatment with the antiestrogen tamoxifen has been well established. However, the development of hormone resistance is an important factor in breast cancer progression against endocrine therapy. The presence of the receptor for EGF (EGFR) correlates with lack of response towards antiestrogen therapy. The EGFR is not only involved in tumor cell growth, survival signaling, cell migration, metastasis formation and angiogenesis, but also seems to confer reduced responses of tumor cells towards anti-hormones. Concomitant inhibition of both, the receptors for estrogen and EGF may be necessary to improve breast cancer therapy.

[Clinical significance of tumor content of epidermal growth factor receptor in breast cancer]

OBJECTIVE

To determine the content of epidermal growth factor receptor (EGFR) using a radioligand method in breast cancer and to analyze the relationship between the EGFR levels and the characteristics of patients and tumors. Prognostic significance was also analyzed.

MATERIAL AND METHODS

EGFR was measured by a single point radioligand assay in 265 invasive breast carcinomas tissues. In addition, estrogen and progesterone receptors (ER and PR) were measured by enzymatic immunoassays. We analyze the relationship of EGFR levels with the different clinico-pathologic parameters.

RESULTS

EGFR levels in breast carcinomas varied widely (0.1 to 403) with a median at 4 fmol/mg prot. The significantly higher concentrations of EGFR were detected in patients under 60 years old (p = 0.042), undifferentiated tumors (p = 0.04), and carcinomas with negative ER and PR (p < 0.019 y p < 0018, respectively). In addition, there was a negative correlation between EGFR and the ER and PR levels (p < 0.05). EGFR levels did not show any relationship with the patient's prognosis.

CONCLUSIONS

In addition, intratumoral levels of EGFR in breast carcinomas vary widely and the highest concentrations are associated with the most aggresive characteristics of the tumor.

Estrogen suppression of EGFR expression in breast cancer cells: a possible mechanism to modulate growth

Epidermal growth factor receptor (EGFR) is a transmembrane receptor whose overexpression in breast cancer predicts for poor prognosis and is inversely correlated with expression of estrogen receptor (ER). This study was designed to investigate whether estrogen plays an active role in suppression of EGFR expression in estrogen-responsive breast cancer cell lines expressing low levels of EGFR. Upon withdrawal of estrogen, EGFR mRNA and protein increased 3-6 fold in MCF-7, T47D, and BT474 ER+ breast cancer cells. This was reversible upon addition of estradiol back to the culture media, but only after prolonged treatment. Nuclear run-on assays and studies with the transcription inhibitor actinomycin D demonstrated that regulation is at the transcriptional level. These results indicate that in the presence of estrogen, ER+ breast cancer cells possess active mechanisms to suppress EGFR expression. Up-regulation of EGFR in response to estrogen depletion and growth inhibition could represent an attempt to rescue cell growth by utilizing an alternative pathway. Indeed, we found that estrogen-depleted breast cancer cells are more sensitive to the mitogenic effects of EGF and TGF-alpha, and simultaneous blockade of both estrogen and EGFR signaling pathways induced cell death. J. Cell. Biochem. Suppl. 36: 232-246, 2001.

Epidermal growth factor receptor expression in 780 breast cancer patients: a reappraisal of the prognostic value based on an eight-year median follow-up

PURPOSE

Because new therapeutic approaches target tumors expressing epidermal growth factor receptor (EGFR), the aim was to undertake a thorough analysis of the expression profile of EGFR in breast cancer and to reassess its prognostic value.

PATIENTS AND METHODS

Tumor EGFR levels were determined by a specific ligand binding assay in 780 consecutive breast cancer patients followed in our institute between 1980 and 1993. Mean age was 61 years (25-85 years). All patients had undergone tumor resection with axillary lymph node dissection: 373 patients (47.8%) underwent mastectomy, 37 (5%) subcutaneous mastectomy and 370 (47.2%) tumorectomy.

RESULTS

EGFR levels ranged between non-detectable up to 789 fmol/mg protein. EGFR median value was 9 fmol/mg protein and only a small proportion of patients exhibited a relatively marked EGFR expression. There was no link between tumor size, grade, node status and EGFR tumoral levels. There was a constant and significant decrease in EGFR tumoral levels according to patient age. A significant inverse relationship was found between estradiol receptors (ER) and EGFR. Median follow-up was 97 months with a minimum at 4 months and a maximum at 228 months. From univariate analysis it was found that histological grade, tumor size, node status and ER status were all significant predictors of survival, considering metastasis-free as well as overall survival. Using multivariable analysis, only histological grade, tumor size and node status remained independent predictors of survival.

CONCLUSION

EGFR determination is of limited value as a prognostic indicator in breast cancer.

Sodium butyrate induces G2 arrest in the human breast cancer cells MDA-MB-231 and renders them competent for DNA rereplication

When exposed to sodium butyrate (NaBut), exponentially growing cells accumulate in G1 and G2 phases of the cell cycle. In the human breast cancer cell line MDA-MB-231, an arrest in G2 phase was observed when the cells were released from hydroxyurea block (G1/S interface) in the presence of NaBut. The inhibition of G2 progression was correlated with increased contents both of total p21(Waf1) and of p21(Waf1) associated with cyclin A and with an inhibition of cyclin A- and B1-associated histone H1 kinase activities measured in cell lysates, as well as with dephosphorylation of the RB protein. A decrease in the cell contents of cyclins A and B1 was also observed but this decrease was preceded by p21(Waf1) accumulation. When NaBut was removed from the culture medium of cells blocked in G2 phase, p21(Waf1) level decreased and, instead of proceeding to mitosis, these cells resumed a progression toward DNA rereplication. These results suggest that the induction of p21(Waf1) by NaBut leads to the inhibition of the sequential activation of cyclin A- and B1-dependent kinases in this cell line, resulting in the inhibition of G2 progression and rendering the cells competent for a new cell division cycle.

De-regulation of GRP stress protein expression in human breast cancer cell lines

The stress-inducible glucose regulated proteins (GRPs), a class of calcium-binding molecular chaperones localized in the endoplasmic reticulum, have been implicated in the development of tumorigenicity, drug resistance, and cytotoxic immunology. This study investigates the expression pattern of GRP94 and GRP78 in a panel of breast carcinoma cell lines, as compared to two independently derived normal human breast epithelial cell lines. Here we report that a 3- to 5-fold increase in the basal level of the GRP94 protein was observed in all five breast carcinoma cell lines examined. The increase was independent of either the p53 or estrogen receptor status of the breast carcinomas. In carcinoma cells deprived of glucose, mimicking the conditions in poorly vascularized solid tumors, up to 9-fold induction of GRP94 was observed relative to the basal level expressed in a normal breast epithelial cell line. Interestingly, while the majority of the breast cancer cell lines can respond to tunicamycin- and thapsigargin-induced stress by increasing the steady state levels of grp94 and grp78 transcripts, the induction at the GRP protein level is variable and does not always correspond with the transcript level. Further, we discovered that one of the human breast carcinoma cell lines, MCF-7, has specifically lost its ability to respond to tunicamycin stress.

Inhibition of platelet-derived growth factor BB-induced expression of glyceraldehyde-3-phosphate dehydrogenase by sodium butyrate in rat vascular smooth muscle cells

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a key regulatory enzyme of glycolysis, which exists in nuclei and functions as a DNA-binding protein as well as a nuclear protein, appears to be modulated by cellular activities. Exposure of quiescent rat smooth muscle cells (SMCs) to platelet-derived growth factor BB (PDGF-BB), which stimulates SMCs proliferation, caused a time-dependent increase in mRNA for GAPDH and its catalytic activity. Treatment of quiescent SMCs with sodium butyrate (SB), which is shown to inhibit PDGF-BB-induced SMC proliferation, caused a time- and concentration-dependent decrease in PDGF-BB-induced GAPDH mRNA expression and its catalytic activity. Nuclear run-on studies revealed that the PDGF-BB-induced rate of GAPDH gene transcription was reduced by about 50% in the presence of 5 mmol/L SB. The protein synthesis inhibitor, cycloheximide, failed to abolish the SB-inhibited PDGF-BB-induced rate of transcription of GAPDH, suggesting that SB is not dependent on ongoing protein synthesis to exert its effects on PDGF-BB-induced GAPDH transcription. Furthermore, measurement of GAPDH mRNA stability at various times after the inhibition of transcription with actinomycin D indicated that 5 mmol/L SB has no significant effect on the half-life of PDGF-BB-induced mRNA. The reduction in PDGF-BB-induced GAPDH expression by SB is probably caused by a cycloheximide-insensitive transcriptional mechanism. Thus, the inhibition of PDGF-BB-induced expression of GAPDH by SB suggests a link between SMC proliferation, energy consumption, and GAPDH gene upregulation.

Inverse regulation of oestrogen receptor and epidermal growth factor receptor gene expression in MCF-7 breast cancer cells treated with phorbol ester

In human breast cancer cell lines, an inverse relationship exists between the basal levels of oestrogen receptor (ER) and epidermal growth factor receptor (EGF-R) gene expression. In addition, the tumour-promoting phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits ER and stimulates EGF-R expression in MCF-7 breast cancer cells. This study aimed to define further the potential mechanisms involved in the modulation of ER and EGF-R gene expression by TPA. ER mRNA levels were reduced after 3 h and declined to 30% of control between 12 and 72 h after exposure to 10 nM TPA. This decrease in mRNA levels was preceded by an apparent fall in ER transcription rate. There was no effect on the stability of ER mRNA following pretreatment for 3-24 h with TPA, supporting the conclusion that the fall in ER mRNA levels was predominantly due to a decrease in ER transcription rate. Levels of EGF-R mRNA increased 10-fold by 12 h due predominantly to an increased transcription rate. The TPA-induced decrease in ER mRNA was unaffected by the simultaneous administration of the protein synthesis inhibitor cycloheximide, whereas the increase in EGF-R mRNA was inhibited by co-incubation with cycloheximide. These data indicate a requirement for continuing protein synthesis for the TPA effect on EGF-R but not on ER mRNA levels. Because the modulation of ER and EGF-R gene expression by TPA is likely to involve the protein kinase C (PKC) signal transduction pathway, the effects of other known activators of PKC were investigated. The non-phorboid tumour promoter mezerein modulated ER (an 80% decrease) and EGF-R (a 20-fold increase) mRNA levels in a similar manner to TPA. In contrast, neither 1,2-dioctanoyl-sn-glycerol (DiC8) nor 1-oleoyl-2-acetyl-sn-glycerol (OAG), both permeant analogues of the endogenous physiological activators of PKC, affected ER and EGF-R mRNA levels. These latter results were not due to a lack of efficacy because a single administration of DiC8 was as effective as TPA in inducing c-fos mRNA at 30 min. However DiC8 was less active in the later induction of c-myc mRNA. These data demonstrate reciprocal regulation of ER and EGF-R gene expression by TPA, involving effects on transcriptional events, which appear to be mediated by sustained activation of PKC.

Sodium butyrate inhibits the phosphorylation of the retinoblastoma gene product in mouse fibroblasts by a transcription-dependent mechanism

In the chemically transformed mouse fibroblasts BP-A31, the retinoblastoma protein (pRB) is hypophosphorylated at quiescence and becomes hyperphosphorylated after approximately 6 h of serum stimulation. Phosphorylation of pRb was blocked if sodium butyrate was added together with serum or within 3 h afterwards. Actinomycin D added 3 h after serum stimulation did not prevent pRb phosphorylation, but it reversed the inhibitory effect of butyrate. These observations indicate that sodium butyrate acts by turning on the expression of gene(s) coding for proteins which prevent the accumulation of hyperphosphorylated pRb. Such butyrate-induced inhibitor(s) may interfere with the phosphorylation of pRb by cyclin-dependent kinases. Treatment of quiescent BP-A31 cells with serum in the presence of sodium butyrate has led to an increased cell content of the Waf1/CIP1 mRNA (coding for a cyclin-dependent) kinase inhibitory protein) compared with serum alone, suggesting a possible role of p21Waf1/CIP1. In contrast, the mitogen activated protein kinase (enzyme which has been shown to phosphorylate pRb) was constitutively active in BP-A31 cells, and its activity was not significantly affected by a < or = 3h incubation with sodium butyrate.

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.

Sodium butyrate inhibits platelet-derived growth factor-induced proliferation of vascular smooth muscle cells

Sodium butyrate (SB), a naturally occurring short-chain fatty acid, was investigated for its therapeutic value as an antiproliferative agent for vascular smooth muscle cells (SMCs). At 5-mmol/L concentration, SB had no significant effect on rat SMC proliferation. However, at the same concentration, SB inhibited platelet-derived growth factor (PDGF)-AA-, -AB-, and -BB-induced proliferation of SMCs. Exposure of SMCs to PDGF-BB resulted in activation of receptor intrinsic tyrosine kinase activity and autophosphorylation of beta-PDGF-receptor (beta-PDGFR). The activated beta-PDGFR physically associated and phosphorylated signaling molecules such as ras-GTPase activating protein (GAP) and phospholipase C gamma (PLC gamma). SB, in the absence of PDGF-BB, caused neither beta-PDGFR tyrosine phosphorylation nor phosphorylation and association of GAP and PLC gamma with beta-PDGFR. PDGF-BB-enhanced activation of receptor intrinsic tyrosine kinase activity and autophosphorylation of tyrosine residues of beta-PDGFR were unaffected by SB irrespective of whether SMCs were preincubated with SB before exposure to PDGF-BB plus SB or incubated concomitantly with PDGF-BB plus SB. Likewise, phosphorylation and association of GAP and PLC gamma with PDGF-BB-activated beta-PDGFR were unaffected. In addition, SB did not block PDGF-BB-stimulated, PLC gamma-mediated production of inositol triphosphate. Similarly, PDGF-BB-induced beta-PDGFR degradation was unaffected when SMCs were exposed to PDGF-BB plus SB, and SB by itself had no influence on beta-PDGFR degradation. Unlike beta-PDGFR kinase activity, mitogen-activated protein kinase (MAP-kinase) activity was stimulated by SB by about 2.7-fold. Exposure of SMCs to PDGF-BB caused an approximately 11.4-fold increase in MAP-kinase activity and this increase in activity was not significantly affected when cells were coincubated with PDGF-BB and SB (10.3-fold). However, pretreatment of SMCs with SB for 30 minutes and subsequent incubation in PDGF-BB plus SB abolished most of the PDGF-BB-induced MAP-kinase activity (4.6-fold). Transcription of growth response genes such as c-fos, c-jun, and c-myc were induced by PDGF-BB, and their induction was suppressed, particularly c-myc, by incubating SMCs with PDGF-BB plus SB. Similarly, preincubation of cells with SB for 30 minutes and subsequent incubation in PDGF-BB plus SB diminished PDGF-BB-induced transcription of c-fos, c-jun, and c-myc. However, SB by itself had no significant effect on c-fos, c-jun, and c-myc transcription.(ABSTRACT TRUNCATED AT 400 WORDS)

Histone acetylation: facts and questions

The DNA of eukaryotic cells is organized in a complex with proteins, either as interphase chromatin or mitotic chromosomes. Nucleosomes, the structural subunits of chromatin, have long been considered as static structures, incompatible with processes occurring in chromatin. During the past few years it has become evident that the histone part of the nucleosome has important regulatory functions. Some of these functions are mediated by the N-terminal core histone domains which contain sites for posttranslational modifications, among them lysine residues for reversible acetylation. Recent results indicate that acetylation and deacetylation of N-terminal lysines of nucleosomal core histones represent a means of molecular communication between chromatin and the cellular signal transduction network, resulting in heritable epigenetic information. Data on enzymes involved in acetylation and the pattern of acetylated lysine sites on chromosomes, as well as genetic data on yeast transcriptional repression, suggest that acetylation may lead to structural transitions as well as specific signalling within distinct chromatin domains.

Butyrate enhances the in vitro anti-SRBC (sheep red blood cell) antibody responses in murine splenocytes

Butyrate at concentrations of 200-600 microM markedly enhanced the in vitro antibody productions against sheep red blood cells (SRBC) in murine splenocytes. However, other saturated short-chain fatty acids, including acetate, propionate and valeric acid, and 4-carbon compounds such as butanol, acetoacetate and beta- and gamma-hydroxybutyrate had no such effects. The presence of butyrate in the early phase of the cell culture was crucial for enhancement of the response. Butyrate also augmented the antibody production in T-cell-depleted splenocytes supplemented with the culture supernatant of concanavalin A (Con A)-stimulated lymphocytes. Interleukin (IL)-2 secreted from splenocytes in response to SRBC was increased by adding butyrate to the culture, but IL-1 secretion was not affected. On the other hand, Con A or lipopolysaccharide-stimulated proliferation of splenocytes was partly depressed by the addition of butyrate, while Con A-induced IL-2 production was not effected. These findings suggest that butyrate may act on T and B cells to promote their differentiation during the process of antibody production.

Altered expression of epidermal growth factor receptor and estrogen receptor in MCF-7 cells after single and repeated radiation exposures

PURPOSE

Studies on radiation-induced changes in gene expression are likely to be very important in developing a better understanding of cellular responses to ionizing radiation. While there is some information on the activation of cellular signal transduction pathways after radiation, few late reacting target genes have been identified. This study focuses on the characterization of expression modulation of two critical growth regulatory genes, estrogen receptor and epidermal growth factor-receptor in malignant mammary epithelial cells in response to single and repeated ionizing radiation exposures.

METHODS AND MATERIALS

MCF-7 cells were used for single radiation exposure (2-50 Gy) experiments and MCF-IR-3 cells, generated by exposure to cumulative doses of 60 Gy in 2 Gy fractions, respectively, were used to study the effects of repeated exposures. Steady-state messenger ribonucleic acid levels for estrogen receptor, epidermal growth factor-receptor, and transforming growth factor-alpha were determined by ribonucleic acid protection experiments. Estrogen receptor and epidermal growth factor-receptor protein expression was quantitated by competitive binding studies with 3H-estradiol and 125I-EGF.

RESULTS

MCF-IR-3 cells showed a permanent three-fold down-regulation of the estrogen receptor messenger ribonucleic acid and protein, while epidermal growth factor-receptor was upregulated about nine-fold. Epidermal growth factor-receptor was substantially up-regulated in MCF-7 cells, at both the mRNA and protein levels, within 24 h of a single 2 Gy exposures, while there was a two-fold concomitant increase in transforming growth factor-alpha messenger ribonucleic acid expression. A decrease in estrogen receptor messenger ribonucleic acid and protein was suggested only after higher doses of single radiation exposures.

CONCLUSION

Single and repeated radiation exposures modulate the expression of two critical growth promoting genes, estrogen receptor and epidermal growth factor-receptor, in MCF-7 cells. The inverse expression of estrogen receptor and epidermal growth factor-receptor established for estrogen receptor-positive malignant mammary epithelial cells is maintained in MCF-7 cells after single and repeated exposures suggesting that radiation acts through common regulatory circuits and may modulate the cellular phenotype.

Expression of estrogen receptors in estrogen receptor-negative human breast carcinoma cells: modulation of epidermal growth factor-receptor (EGF-R) and transforming growth factor alpha (TGF alpha) gene expression

A number of studies suggest that an inverse correlation exists between the epidermal growth factor-receptor and the estrogen receptor expression in primary human breast carcinoma as well as in established human breast carcinoma cell lines. Recent studies suggest that the epidermal growth factor-receptor does not regulate the estrogen receptor gene expression. Whether the estrogen receptor regulates the epidermal growth factor-receptor gene expression is not known. We addressed this question by stably transfecting the estrogen receptor cDNA into the estrogen receptor-negative human breast carcinoma cell line MDA-MB-231. Constitutive expression of functional estrogen receptors in the transfectants resulted in increased mRNA levels of both epidermal growth factor-receptor and transforming growth factor alpha. Estradiol treatment of transfected cells, although enhancing transforming growth factor alpha mRNA levels, did not modulate epidermal growth factor-receptor mRNA levels. The estrogen receptor-transfected cells grown in estrogenic regular medium, however, exhibited lower constitutive levels of epidermal growth factor-receptor mRNA than in steroid-stripped medium, suggesting that estrogens coupled with some factors normally present in the regular medium may indeed downmodulate epidermal growth factor-receptor mRNA. Sodium butyrate treatment enhanced epidermal growth factor-receptor mRNA levels in nontransfected cells grown in regular estrogenic as well as in steroid stripped medium. Sodium butyrate enhancement of epidermal growth factor-receptor mRNA levels was completely abolished in estrogen receptor-transfected cells grown in regular estrogenic medium and blunted in steroid stripped medium. Using various epidermal growth factor-receptor gene promoter-CAT constructs in transient transfection assays, we further demonstrate that sodium butyrate enhanced transcription of the epidermal growth factor-receptor gene. The putative sodium butyrate responsive element(s) appears to localize within the proximal 384 bp of the epidermal growth factor-receptor gene promoter region. Although the interactions between estrogen receptor and epidermal growth factor-receptor are rather complex, taken together, our data suggest that estrogen receptor can indeed modulate the epidermal growth factor-receptor mRNA expression.

EGF receptor expression, regulation, and function in breast cancer

Epidermal growth factor receptor (EGFR) overexpression correlates with both loss of estrogen receptor (ER) and poor prognosis in breast cancer. Interestingly, in normal breast EGFR appears to be expressed more frequently than in malignant tissue, and there may be a different relationship between ER and EGFR. A variety of cellular regulators, such as EGF, TGF alpha, phorbol esters, and steroid hormones, are capable of altering the level of EGFR expression in breast cells. However, much work remains to be done on the mechanistic details of EGFR regulation in this disease. The significance of EGFR as an oncogene in breast cancer is compounded by its potential interactions with other oncogenes such as c-erbB-2 and c-myc. Additionally, several recent studies have placed EGFR prominently in the signal transduction pathway, demonstrating that the EGFR-ligand system may play important roles throughout the course of malignant progression in breast cancer.

The prognostic value of epidermal growth factor receptor (EGF-R) in primary breast cancer: results of a 10 year follow-up study

In a study on 214 patients with primary breast cancer (median follow-up 8.5 yr, maximum follow-up 15 yr), EGF-R was negatively correlated to estrogen receptor and progesterone receptor, whereas no association was found with age, lymph node status, and tumor size. Initially, after a follow-up of 5 yr, there was a tendency to a significant association between EGF-R levels and tumor recurrence rate (p = 0.08). Patients with tumors containing intermediate levels of EGF-R experienced a longer relapse-free survival (RFS) than did patients with tumors possessing lower or higher levels of EGF-R. This effect was most pronounced in the subgroup of patients with positive axillary lymph nodes. However, after 10 yr follow-up, this association appears to be lost (p = 0.28) as shown in this update. A similar phenomenon was observed for the ER. While at 5 yr follow-up ER status had significant prognostic value (p = 0.01), at 10 yr follow-up this significance also appears to be lost (p = 0.40). However, tumor size, lymph node status, grade, and PgR status maintained significant prognostic value by univariate analysis. Based on 40 separate studies comprising 5232 patients, the mean percentage of EGF-R positivity reported in breast cancer is 45% (range 14-91%). Nine out of 15 different studies showed in some way a significant negative association between EGF-R and RFS by univariate analysis, and 2 others showed a tendency to such a relationship. Of 7 studies applying multivariate analysis, two demonstrated an independent prognostic value of EGF-R for RFS and two others a tendency to a significant correlation, whereas three did not. It may be concluded that EGF-R status has more or less prognostic value in patients with primary breast cancer, but the prognostic power decreases with longer follow-up. Of great clinical significance is the association of EGF-R with hormone resistance. Therefore EGF-R status can be used for selection of type of treatment. Finally, EGF-R might be useful as a target for new treatment modalities.

Mechanisms of EGF receptor regulation in breast cancer cells

Overexpression of the EGF receptor in breast cancer correlates with poor prognosis and failure on endocrine therapy for both ER-/EGFR+ and ER+/EGFR+ tumors, suggesting a role for EGFR in the progression to hormone independence. The identification of specific DNAse I hypersensitive site patterns for the EGFR gene in ER+ vs. ER- cells implicates regions of the EGFR first intron in up-regulation of EGFR, while estrogen regulation studies indicate the involvement of a repressor(s) in the maintenance of low levels of EGFR. Based on these findings, a multi-step model is proposed for the progression of breast cancer from a hormone-dependent, ER+/EGFR-phenotype to an aggressive, hormone-independent, ER-/EGFR+ stage.