Roles of transforming growth factor-alpha in mammary development and disease

ERBB Receptors and Their Ligands in the Developing Mammary Glands of Different Species: Fifteen Characters in Search of an Author

The ERBB tyrosine kinase receptors and their ligands belong to a complex family that has diverse biological effects and expression profiles in the developing mammary glands, where its members play an essential role in translating hormone signals into local effects. While our understanding of these processes stems mostly from mouse models, there is the potential for differences in how this family functions in the mammary glands of other species, particularly in light of their unique histomorphological features. Herein we review the postnatal distribution and function of ERBB receptors and their ligands in the mammary glands of rodents and humans, as well as for livestock and companion animals. Our analysis highlights the diverse biology for this family and its members across species, the regulation of their expression, and how their roles and functions might be modulated by varying stromal composition and hormone interactions. Given that ERBB receptors and their ligands have the potential to influence processes ranging from normal mammary development to diseased states such as cancer and/or mastitis, both in human and veterinary medicine, a more complete understanding of their biological functions should help to direct future research and the identification of new therapeutic targets.

Association of serum interleukin-10, interleukin-17A and transforming growth factor-α levels with human benign and malignant breast diseases

Interleukin-10 (IL-10), interleukin-17A (IL-17A) and transforming growth factor α (TGF-α) have been implicated in the progression of breast cancer. However, the diagnostic and prognostic roles of these cytokines in ductal carcinoma remain unclear. The present study therefore aimed to determine the serum levels of IL-10, IL-17 and TGF-α in subjects with benign and malignant breast diseases and to evaluate the clinical significance of these cytokines in ductal carcinoma. Pre-operative serum samples were collected from 378 patients with breast disease and 70 healthy subjects. IL-10, IL-17A and TGF-α levels were measured using ELISA. Serum levels of these cytokine in patients with different breast diseases were evaluated. Furthermore, correlations between levels of these cytokines and the expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) in ductal carcinoma were determined. The results demonstrated that serum levels of IL-10 and IL-17A were significantly increased in subjects with atypical hyperplasia and ductal carcinoma. Furthermore, IL-10 and IL-17A levels were increased in patients with a more serious clinical tumor stage and tumors that were ER^- and PR^-. Furthermore, high serum levels of TGF-α were associated with HER2⁺ tumors. A strong positive correlation was identified between TGF-α and IL-17A levels. Therefore, the results of the current study revealed that elevated serum IL-10, IL-17A and TGF-α levels are strongly associated with ductal carcinoma, specifically with tumor stage. High serum levels of IL-10 and IL-17A were also associated with the negative expression of ER and PR in ductal carcinoma, and high serum levels of TGF-α were associated with the positive expression of HER2 in ductal carcinoma. Thus, serum cytokine levels may be measured to identify patients with a poor prognosis who may benefit from more aggressive management and treatment.

Epithelial cell identity in hyperplastic precursors of breast cancer

Introduction

In the adult human breast, hyperplastic enlarged lobular unit (HELU) and atypical ductal hyperplasia (ADH) are two common abnormalities that frequently coexist with ductal carcinoma in situ (DCIS). For this reason, they have been proposed as the early steps in a biological continuum toward breast cancer.

Methods

We investigated in silico the expression of 369 genes experimentally recognized as involved in establishing and maintaining epithelial cell identity and mammary gland remodeling, in HELUs or ADHs with respect to the corresponding patient-matched normal tissue.

Results

Despite the common luminal origin, HELUs and ADHs proved to be characterized by distinct gene profiles that overlap for 5 genes only. While HELUs were associated with the overexpression of progesterone receptor (PGR), ADHs were characterized by the overexpression of estrogen receptor 1 (ESR1) coupled with the overexpression of some proliferation-associated genes.

Conclusions

This unexpected finding contradicts the notion that in differentiated luminal cells the expression of estrogen receptor (ER) is dissociated from cell proliferation and suggests that the establishing of an ER-dependent signaling is able to sustain cell proliferation in an autocrine manner as an early event in tumor initiation. Although clinical evidence indicates that only a fraction of HELUs and ADHs evolve to invasive cancer, present findings warn that exposure to synthetic progestins, frequently administered as hormone-replacement therapy, and estrogens, when abnormally produced by adipose cells and persistently present in the stroma surrounding the mammary gland, may cause these hyperplastic lesions.

Modeling prolactin actions in breast cancer in vivo: insights from the NRL-PRL mouse

Elevated exposure to prolactin (PRL) is epidemiologically associated with an increased risk of aggressive ER+ breast cancer. To understand the underlying mechanisms and crosstalk with other oncogenic factors, we developed the NRL-PRL mouse. In this model, mammary expression of a rat prolactin transgene raises local exposure to PRL without altering estrous cycling. Nulliparous females develop metastatic, histotypically diverse mammary carcinomas independent from ovarian steroids, and most are ER+. These characteristics resemble the human clinical disease, facilitating study of tumorigenesis, and identification of novel preventive and therapeutic approaches.

The role of cytokines in breast cancer development and progression

Cytokines are highly inducible, secretory proteins that mediate intercellular communication in the immune system. They are grouped into several protein families that are referred to as tumor necrosis factors, interleukins, interferons, and colony-stimulating factors. In recent years, it has become clear that some of these proteins as well as their receptors are produced in the organisms under physiological and pathological conditions. The exact initiation process of breast cancer is unknown, although several hypotheses have emerged. Inflammation has been proposed as an important player in tumor initiation, promotion, angiogenesis, and metastasis, all phenomena in which cytokines are prominent players. The data here suggest that cytokines play an important role in the regulation of both induction and protection in breast cancer. This knowledge could be fundamental for the proposal of new therapeutic approaches to particularly breast cancer and other cancer-related disorders.

Genetically engineered ERα-positive breast cancer mouse models

The majority of human breast cancers are estrogen receptor-positive (ER+), but this has proven challenging to model in genetically engineered mice. This review summarizes information on 21 mouse models that develop ER+ mammary cancer. Where available, information on cancer pathology and gene expression profiles is referenced to assist in understanding which histological subtype of ER+ human cancer each model might represent. ESR1, CCDN1, prolactin, TGFα, AIB1, ESPL1, and WNT1 overexpression, PIK3CA gain of function, as well as loss of P53 (Trp53) or STAT1 are associated with ER+ mammary cancer. Treatment with the PPARγ agonist efatutazone in a mouse with Brca1 and p53 deficiency and 7,12-dimethylbenz(a)anthracene exposure in combination with an activated myristoylated form of AKT1 also induce ER+ mammary cancer. A spontaneous mutant in nude mice that develops metastatic ER+ mammary cancer is included. Age of cancer development ranges from 3 to 26 months and the percentage of cancers that are ER+ vary from 21 to 100%. Not all models are characterized as to their estrogen dependency and/or response to anti-hormonal therapy. Strain backgrounds include C57Bl/6, FVB, BALB/c, 129S6/SvEv, CB6F1, and NIH nude. Most models have only been studied on one strain background. In summary, while a range of models are available for studies of pathogenesis and therapy of ER+ breast cancers, many could benefit from further characterization, and opportunity for development of new models remains.

From wavy hair to naked proteins: the role of transforming growth factor alpha in health and disease

Since its discovery in 1978 and cloning in 1984, transforming growth factor-alpha (TGF-α, TGFA) has been one of the most extensively studied EGF receptor (EGFR) ligands. In this review, we provide a historical perspective on TGFA-related studies, highlighting what we consider important advances related to its function in normal and disease states.

Regulation of intestinal epithelial permeability by tight junctions

The gastrointestinal epithelium forms the boundary between the body and external environment. It effectively provides a selective permeable barrier that limits the permeation of luminal noxious molecules, such as pathogens, toxins, and antigens, while allowing the appropriate absorption of nutrients and water. This selective permeable barrier is achieved by intercellular tight junction (TJ) structures, which regulate paracellular permeability. Disruption of the intestinal TJ barrier, followed by permeation of luminal noxious molecules, induces a perturbation of the mucosal immune system and inflammation, and can act as a trigger for the development of intestinal and systemic diseases. In this context, much effort has been taken to understand the roles of extracellular factors, including cytokines, pathogens, and food factors, for the regulation of the intestinal TJ barrier. Here, I discuss the regulation of the intestinal TJ barrier together with its implications for the pathogenesis of diseases.

Serum Levels of Epidermal Growth Factor, Transforming Growth Factor, and c-erbB2 in Ovarian Cancer

Objective

This study aimed to investigate serum levels of epidermal growth factor (EGF), transforming growth factor α (TGF-α), and c-erbB2 in patients with ovarian cancer.

Materials and Methods

In this retrospective cohort study, the study and control groups were composed of 43 women with a prediagnosis of ovarian cancer and 43 healthy women, respectively. Blood samples from all women were obtained and studied by enzyme-linked immunosorbent assay kits for EGF, TGF-α, and c-erbB2. After surgery of the study group, ovarian cancer was confirmed and compared with control group. Stage, grade, and histological types were defined after histopathologic examination, and subgroups were constructed and compared.

Results

Serum EGF, TGF-α, and c-erbB2 levels were significantly increased in study group compared with those in the control group (P < 0.001). There were no differences in serum levels of EGF, TGF-α, and c-erbB2 among all stages, grades, and histological types of ovarian cancer. If 47.90 pg/mL was selected as the cutoff value, EGF has an 80% sensitivity and a 65% specificity for detecting ovarian cancer. The cutoff value of 41,095.00 pg/mL for TGF-α has a 90% sensitivity and a 72% specificity for detecting ovarian cancer. The c-erbB2 level of 4.63 pg/mL as the cutoff value has an 83% sensitivity and a 76% specificity for predicting ovarian cancer.

Conclusions

Serum levels of EGF, TGF-α, and c-erbB2 may be used for diagnosing ovarian cancer.

Nucleobindin 2 in human breast carcinoma as a potent prognostic factor

It is well-known that estrogens immensely contribute to the progression of human breast carcinoma, but their detailed molecular mechanisms remain largely unclear. In this study, we identified nucleobindin 2 (NUCB2) as a gene associated with recurrence based on microarray data of estrogen receptor (ER)-positive breast carcinoma cases (n = 10), and subsequent in vitro study showed that NUCB2 expression was upregulated by estradiol in ER-positive MCF-7 cells. However, NUCB2 has not yet been examined in breast carcinoma, and its significance remains unknown. Therefore, we further examined the biological functions of NUCB2 in breast carcinoma using immunohistochemistry and in vitro studies. NUCB2 immunoreactivity was detected in carcinoma cells in 77 of 161 (48%) breast cancer cases, and positively associated with lymph node metastasis and ER status of the patients. In addition, NUCB2 status was significantly associated with an increased risk of recurrence and adverse clinical outcome of the patients using both univariate and multivariate analyses. Results of siRNA transfection experiments showed that NUCB2 significantly increased cell proliferation, and migration and invasion properties in both MCF-7 and ER-negative SK-BR-3 cells. These results suggest that NUCB2 is upregulated by estrogens and plays an important role, especially in the process of metastasis, in breast carcinomas. NUCB2 status is considered a potent prognostic factor in human breast cancer.

Serum cytokine profiles in healthy young and elderly population assessed using multiplexed bead-based immunoassays

Background

Lipid metabolites and cytokines, including chemokines and growth factors, are the key regulators of immune cell function and differentiation, and thus, dysregulation of these regulators is associated with various human diseases. However, previous studies demonstrating a positive correlation of cytokine levels with aging may have been influenced by various environmental factors and underlying diseases. Also, data regarding cytokine profiling in the elderly are limited to a small subset of cytokines.

Methods

We compared the profiles of 22 cytokines, including chemokines and growth factors, in a case-controlled study group of a gender-matched, healthy cohort of 55 patients over the age of 65 and 55 patients under the age of 45. Assessment of serum cytokine concentrations was performed using commercially-available multiplex bead-based sandwich immunoassays.

Results

Soluble CD40 ligand (sCD40L) and transforming growth factor alpha (TGF-α) levels were significantly higher in the elderly patients, whereas granulocyte colony-stimulating factor (G-CSF), granulocyte-monocyte colony-stimulating factor (GM-CSF), and monocyte chemoattractant protein-1 (MCP-1) levels were significantly lower in the elderly patients. The partial correlation analysis demonstrating the correlation between cytokine levels when controlled for gender, systolic blood pressure, total cholesterol, HDL cholesterol, triglyceride, and serum creatinine levels further demonstrated that G-CSF, GM-CSF, and MCP-1 had significant negative correlations with age, whereas sCD40L and TGF-α had significant positive correlations.

Conclusions

Future studies will focus on examining the significance of these age-related changes in circulating cytokines and other biological markers and their potential contribution to the development of different age-associated diseases.

The normal microenvironment directs mammary gland development

Normal development of the mammary gland is a multidimensional process that is controlled in part by its mammary microenvironment. The mammary microenvironment is a defined location that encompasses mammary somatic stem cells, neighboring signaling cells, the basement membrane and extracellular matrix, mammary fibroblasts as well as the intercellular signals produced and received by these cells. These dynamic signals take numerous forms including growth factors, steroids, cell-cell or cell-basement membrane physical interactions. Cellular growth and differentiation of the mammary gland throughout the developmental stages are regulated by changes in these signals and interactions. The purpose of this review is to summarize current information and research regarding the role of the mammary microenvironment during normal glandular development.

ErbB/EGF signaling and EMT in mammary development and breast cancer

Activation of the ErbB family of receptor tyrosine kinases via cognate Epidermal Growth Factor (EGF)-like peptide ligands constitutes a major group of related signaling pathways that control proliferation, survival, angiogenesis and metastasis of breast cancer. In this respect, clinical trials with various ErbB receptor blocking antibodies and specific tyrosine kinase inhibitors have proven to be partially efficacious in the treatment of this heterogeneous disease. Induction of an embryonic program of epithelial-to-mesenchymal transition (EMT) in breast cancer, whereupon epithelial tumor cells convert to a more mesenchymal-like phenotype, facilitates the migration, intravasation, and extravasation of tumor cells during metastasis. Breast cancers which exhibit properties of EMT are highly aggressive and resistant to therapy. Activation of ErbB signaling can regulate EMT-associated invasion and migration in normal and malignant mammary epithelial cells, as well as modulating discrete stages of mammary gland development. The purpose of this review is to summarize current information regarding the role of ErbB signaling in aspects of EMT that influence epithelial cell plasticity during mammary gland development and tumorigenesis. How this information may contribute to the improvement of therapeutic approaches in breast cancer will also be addressed.

G protein-coupled receptor 30 expression is up-regulated by EGF and TGF alpha in estrogen receptor alpha-positive cancer cells

In the present study, we evaluated the regulation of G protein-coupled receptor (GPR)30 expression in estrogen receptor (ER)-positive endometrial, ovarian, and estrogen-sensitive, as well as tamoxifen-resistant breast cancer cells. We demonstrate that epidermal growth factor (EGF) and TGF alpha transactivate the GPR30 promoter and accordingly up-regulate GPR30 mRNA and protein levels only in endometrial and tamoxifen-resistant breast cancer cells. These effects exerted by EGF and TGF alpha were dependent on EGF receptor (EGFR) expression and activation and involved phosphorylation of the Tyr(1045) and Tyr(1173) EGFR sites. Using gene-silencing experiments and specific pharmacological inhibitors, we have ascertained that EGF and TGF alpha induce GPR30 expression through the EGFR/ERK transduction pathway, and the recruitment of c-fos to the activator protein-1 site located within GPR30 promoter sequence. Interestingly, we show that functional cross talk of GPR30 with both activated EGFR and ER alpha relies on a physical interaction among these receptors, further extending the potential of estrogen to trigger a complex stimulatory signaling network in hormone-sensitive tumors. Given that EGFR/HER2 overexpression is associated with tamoxifen resistance, our data may suggest that ligand-activated EGFR could contribute to the failure of tamoxifen therapy also by up-regulating GPR30, which in turn could facilitates the action of estrogen. In addition, important for resistance is the ability of tamoxifen to bind to and activate GPR30, the expression of which is up-regulated by EGFR activation. Our results emphasize the need for new endocrine agents able to block widespread actions of estrogen without exerting any stimulatory activity on transduction pathways shared by the steroid and growth factor-signaling networks.

The role of ADAMs in disease pathophysiology

The ADAMs are a family of multidomain transmembrane and secreted proteins involved in both proteolysis and cell adhesion. Altered expression of specific ADAMs is implicated in the pathophysiology of several diseases including rheumatoid arthritis, Alzheimer's disease, cardiac hypertrophy, asthma and cancer. Of these different diseases, it is in cancer where most research has been carried out. Multiple ADAMs, including ADAM-9, ADAM-10, ADAM-12, ADAM-15 and ADAM-17, have been shown to play a role in either cancer formation or progression. Consistent with these findings, increased expression of specific ADAMs in several cancer types was found to correlate with features of aggressive disease and poor prognosis. Currently, selective ADAM inhibitors against ADAM-10 and ADAM-17 are undergoing clinical trials for the treatment of cancer. Further work is required in order to establish a causative role for ADAMs in rheumatoid arthritis, Alzheimer's disease, cardiac hypertrophy and asthma.

Prolactin-growth factor crosstalk reduces mammary estrogen responsiveness despite elevated ERalpha expression

Most breast cancers that occur in women express estrogen receptor alpha (ERalpha). However, a large subset of these cancers either does not initially respond to anti-estrogen therapy or develops resistance to such treatment modalities. One postulated mechanism of this failure is signaling cross talk between hormones and local growth factors. To examine these complex interactions in vivo, we assessed the effects of estrogen on transforming growth factor alpha (TGFalpha)- and prolactin (PRL)-induced mammary tumorigenesis in transgenic mice. Both PRL and estrogen reduced the latency of TGFalpha-induced oncogenesis, resulting in tumors that were variably ERalpha-positive, but were progesterone receptor-negative. However, despite elevated ERalpha levels in NRL-PRL/TGFalpha glands, tumor latency was not reduced with increasing estrogen levels, nor increased after ovariectomy. Furthermore, PRL and TGFalpha in combination blocked the mitogenic effects of estrogen, dramatically reduced progesterone receptor levels, and diminished ERalpha down-regulation in response to circulating estrogen levels, in contrast to the other genotypes. Notably, however, ductal morphology remained responsive to estrogen, indicating that TGFalpha and PRL in combination can inhibit some, but not all, estrogenic signals. Both in vitro and in vivo, PRL and TGFalpha cooperatively enhanced Akt phosphorylation, which is associated with endocrine resistance in human disease. These findings provide insight into the interactions of PRL with growth factors during mammary oncogenesis and suggest combinatorial approaches that may result in improved therapeutic efficacy.

Functional selectivity of EGF family peptide growth factors: implications for cancer

Breast, prostate, pancreatic, colorectal, lung, and head and neck cancers exploit deregulated signaling by ErbB family receptors and their ligands, EGF family peptide growth factors. EGF family members that bind the same receptor are able to stimulate divergent biological responses both in cell culture and in vivo. This is analogous to the functional selectivity exhibited by ligands for G-protein coupled receptors. Here we review this literature and propose that this functional selectivity of EGF family members is due to distinctions in the conformation of the liganded receptor and subsequent differences in the sites of receptor tyrosine phosphorylation and receptor coupling to signaling effectors. We also discuss the roles of divergent ligand activity in establishing and maintaining malignant phenotypes. Finally, we discuss the potential of mutant EGF family ligands as cancer chemotherapeutics targeted to ErbB receptors.

Transforming growth factor-alpha stimulates enterocyte proliferation and accelerates intestinal recovery following methotrexate-induced intestinal mucositis in a rat and a cell culture model

PURPOSE

Recent evidence suggests that transforming growth factor-alpha (TGF-alpha) enhances enterocyte proliferation and exerts a gut trophic effect. The purpose of the present study was to evaluate the effect of TGF-alpha on enterocyte proliferation and intestinal recovery following methotrexate (MTX)-induced intestinal mucositis in rats and in Caco-2 cells.

METHODS

Nonpretreated Caco-2 cells and those pretreated with MTX were incubated with increasing concentrations of TGF-alpha. Cell proliferation was determined by FACS cytometry. Adult rats were divided into three groups: control rats treated with vehicle, MTX rats treated with one dose (20 microg/kg) of MTX given intraperitoneally, and MTX-TGF-alpha rats treated with one dose of MTX followed by two doses of TGF-alpha (75 microg/kg a day). Three days after MTX injection, rats were sacrificed. Intestinal mucosal damage (Park's score), mucosal structural changes, and enterocyte proliferation were measured at sacrifice. Western blotting was used to determine the level of extracellular signal-related kinase (ERK) protein, a marker of cell proliferation. A nonparametric Kruskal-Wallis ANOVA test was used for statistical analysis with P value less than 0.05 considered statistically significant.

RESULTS

The in vitro experiment demonstrated that treatment with TGF-alpha of Caco-2 cells resulted in a significant stimulation of cell proliferation in a dose-dependent manner. The in vivo experiment showed that treatment with TGF-alpha resulted in a significant increase in bowel and mucosal weight, DNA and protein content in jejunum and ileum, villus height in jejunum and ileum, crypt depth in ileum, and increased cell proliferation in jejunum and ileum compared to the MTX group. MTX-TGF-alpha rats also had a significantly lower intestinal injury score in ileum when compared to MTX animals. The increase in levels of cell proliferation in MTX-TGF-alpha rats corresponded with the increase in ERK protein levels in intestinal mucosa.

CONCLUSION

Treatment with TGF-alpha prevents mucosal injury, enhances ERK-induced enterocyte proliferation, and improves intestinal recovery following MTX-induced intestinal mucositis in rats. These findings correlated with the observation that TGF-alpha also caused a significant stimulation of cell proliferation in a Caco-2 cell culture model treated with MTX. These observations may have significant implications for the treatment of patients on chemotherapy who develop severe mucositis.

Expression of transforming growth factor α and Cyclin E and their correlation in chronic gastric lesion tissues from patients with different TCM types

AIM: To explore the expression of transforming growth factor α (TGF-α) and Cyclin E in chronic gastric lesion tissues from patients with different types of traditional Chinese medicine (TCM), and analyze the correlation between TGF-α and Cyclin E expression.

METHODS: The patients (n = 135) with chronic gastric diseases were classified to 4 groups according to different TCM types such as disharmony between liver and stomach (group A), spleen-stomach cold deficiency (group B), stomach-yin deficiency (group C), and mixed cold and heat (group D). Immunohistochemical staining was used to examine the expression of TGF-α and Cyclin E in the lesion tissues and the correlation between TGF-α and Cyclin E expression was also ssessed.

RESULTS: The positive rates of TGF-α expression in the lesion tissues of group A, B, C and D were 25.0%, 18.6%, 47.1% and 42.1%, respectively, and there was significant difference between group B and C (P < 0.05). The positive rates of Cyclin E expression were 20.0%, 7.0%, 26.5% and 31.6%, respectively, and there was marked difference between group B and D (P < 0.05). Both TGF-α and Cyclin E expression were the lowest in group B, and there existed a positive correlation between the expression of TGF-α and Cyclin E.

CONCLUSION: TGF-α and Cyclin E are differentially expressed in chronic gastric lesion tissues of patients with different TCM types, and the expression of TGF-α and Cyclin E are positively correlated.