Activin, inhibin and the human breast

Presepsin in Human Milk Is Delivery Mode and Gender Dependent

Breast milk (BM) is a unique food due to its nutritional composition and anti-inflammatory characteristics. Evidence has emerged on the role of Presepsin (PSEP) as a reliable marker of early sepsis diagnosis. In the present study, we aimed to investigate the measurability of PSEP in BM according to different maturation stages (colostrum, C; transition, Tr; and mature milks, Mt) and corrected for delivery mode and gender. We conducted a multicenter prospective case-control study in women who had delivered 22 term (T) and 22 preterm (PT) infants. A total of 44 human milk samples were collected and stored at -80 °C. BM PSEP (pg/mL) levels were measured by using a rapid chemiluminescent enzyme immunoassay. PSEP was detected in all samples analyzed. Higher (p < 0.05) BM PSEP concentrations were observed in the PT compared to the T infants. According to the grade of maturation, higher (p < 0.05) levels of PSEP in C compared to Tr and Mt milks were observed in the whole study population. The BM subtypes' degrees of maturation were delivery mode and gender dependent. We found that PSEP at high concentrations supports its antimicrobial action both in PT and T infants. These results open the door to further studies investigating the role of PSEP.

Dual Roles of the Activin Signaling Pathway in Pancreatic Cancer

Activin, a member of the TGF-β superfamily, is involved in many physiological processes, such as embryonic development and follicle development, as well as in multiple human diseases including cancer. Genetic mutations in the activin signaling pathway have been reported in many cancer types, indicating that activin signaling plays a critical role in tumorigenesis. Recent evidence reveals that activin signaling may function as a tumor-suppressor in tumor initiation, and a promoter in the later progression and metastasis of tumors. This article reviews many aspects of activin, including the signaling cascade of activin, activin-related proteins, and its role in tumorigenesis, particularly in pancreatic cancer development. The mechanisms regulating its dual roles in tumorigenesis remain to be elucidated. Further understanding of the activin signaling pathway may identify potential therapeutic targets for human cancers and other diseases.

Down-regulated FST expression is involved in the poor prognosis of triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) is more commonly associated with young patients, featuring high histological grade, visceral metastasis, and distant recurrence. Follistatin (FST) is a secreted extracellular regulatory protein that antagonizes TGF-β superfamily such as activin and TGF-β related superfamily such as bone morphogenetic protein (BMP). The implication of FST in the proliferation, angiogenesis, and metastasis of solid tumors documents good or poor outcome of patients with BC. However, the role of FST in TNBC remains unclear.

Methods

Data of 935 patients with breast cancer (BC) were extracted from TCGA. Case–control study, Kaplan–Meier, uni-multivariate COX, and ROC curve were utilized to investigate the relationship between FST expression and the clinical characteristics and prognosis of BC. Functional studies were used to analyze the effect of FST expression on proliferation, apoptosis, migration, and invasion of TNBC cell lines. Bioinformatic methods such as volcanoplot, GO annd KEGG enrichment, and protein–protein interactions (PPI) analyses were conducted to further confirm the different roles of FST in the apoptotic pathways among mesenchymal and mesenchymal stem-like cells of TNBC.

Results

Data from TCGA showed that low FST expression correlated with poor prognosis (for univariate analysis, HR = 0.47, 95% CI: 0.27–0.82, p = 0.008; for multivariate analysis, HR = 0.40, 95% CI: 0.21–0.75, p = 0.004). Low FST expression provided high predicted value of poor prognosis in TNBC amongst BCs. FST knockdown promoted the proliferation, migration and invasion of BT549 and HS578T cell lines. FST inhibited the apoptosis of mesenchymal cells by targeting BMP7.

Conclusions

Low FST expression is associated with poor prognosis of patients with TNBC. FST expressions exhibit the anisotropic roles of apoptosis between mesenchymal and mesenchymal stem-like cells but promote the proliferation, migration, invasion in both of two subtypes of TNBC in vitro. FST may be a subtype-heterogeneous biomarker for monitoring the progress of TNBC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01977-x.

Gene Selection for the Discrimination of Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide. Cancer discrimination is a typical application of gene expression analysis using a microarray technique. However, microarray data suffer from the curse of dimensionality and usual imbalanced class distribution between the majority (tumor samples) and minority (normal samples) classes. Feature gene selection is necessary and important for cancer discrimination.

OBJECTIVES

To select feature genes for the discrimination of CRC.

METHODS

We improve the feature selection algorithm based on differential evolution, DEFSw by using RUSBoost classifier and weight accuracy instead of the common classifier and evaluation measure for selecting feature genes from imbalance data. We firstly extract differently expressed genes (DEGs) from the CRC dataset of the TCGA and then select the feature genes from the DEGs using the improved DEFSw algorithm. Finally, we validate the selected feature gene sets using independent datasets and retrieve the cancer related information for these genes based on text mining through the Coremine Medical online database.

RESULTS

We select out 16 single-gene feature sets for colorectal cancer discrimination and 19 single-gene feature sets only for colon cancer discrimination.

CONCLUSIONS

In summary, we find a series of high potential candidate biomarkers or signatures, which can discriminate either or both of colon cancer and rectal cancer with high sensitivity and specificity.

The Activin Social Network: Activin, Inhibin, and Follistatin in Breast Development and Cancer

Activins and inhibins are closely related protein heterodimers with a similar tissue distribution; however, these two complexes have opposing functions in development and disease. Both are secreted cytokine hormones, with activin the primary inducer of downstream signaling cascades and inhibin acting as a rheostat that exquisitely governs activin function. Adding to the complexity of activin signaling, follistatin, a highly glycosylated monomeric protein, binds activin with high affinity and restrains downstream pathway activation but through a mechanism distinct from that of inhibin. These three proteins were first identified as key ovarian hormones in the pituitary-gonadal axis that direct the synthesis and secretion of FSH from the pituitary, hence controlling folliculogenesis. Research during the past 30 years has expanded the roles of these proteins, first by discovering the ubiquitous expression of the trio and then by implicating them in a wide array of biological functions. In concert, these three hormones govern tissue development, homeostasis, and disease in multiple organ systems through diverse autocrine and paracrine mechanisms. In the present study, we have reviewed the actions of activin and its biological inhibitors, inhibin, and follistatin, in mammary gland morphogenesis and cancer.

Human Wharton's Jelly Mesenchymal Stem Cells Show Unique Gene Expression Compared with Bone Marrow Mesenchymal Stem Cells Using Single-Cell RNA-Sequencing

Human Wharton's jelly stem cells (hWJSCs) isolated from the human umbilical cord are a unique population of mesenchymal stem cells (MSCs) with significant clinical utility. Their broad differentiation potential, high rate of proliferation, ready availability from discarded cords, and prolonged maintenance of stemness properties in culture make them an attractive alternative source of MSCs with therapeutic value compared with human bone marrow MSCs (hBMMSCs). We aimed to characterize the differences in gene expression profiles between these two stem cell types using single-cell RNA sequencing (scRNA-Seq) to determine which pathways are involved in conferring hWJSCs with their unique properties. We identified 436 significantly differentially expressed genes between the two cell types, playing roles in processes, including immunomodulation, angiogenesis, wound healing, apoptosis, antitumor activity, and chemotaxis. Expression of immune molecules is particularly high in hWJSCs compared with hBMMSCs. These differences in gene expression may help to explain many of the advantages that hWJSCs have over hBMMSCs for clinical application. Although cell surface protein marker expression indicates that isolated hWJSCs and hBMMSCs are both homogenous populations, using scRNA-Seq we can clearly identify extreme variability in expression levels between individual cells within a certain cell type. If the cells are examined as bulk populations, it is not possible to appreciate that a single cell may be making a major unique contribution to the apparent overall expression level. We demonstrated how the fine tuning of expression within hWJSCs and hBMMSCs may be achieved by expression of molecules with opposing function between two cells. We hypothesize that a greater understanding of these differences in gene expression between the two cell types may aid in the development of new therapies using hWJSCs.

Growth factor genes and change in mammographic density after stopping combined hormone therapy in the California Teachers Study

Background

The contribution of genetic polymorphisms to the large inter-individual variation in mammographic density (MD) changes following starting and stopping use of estrogen and progestin combined therapy (EPT) has not been well-studied. Previous studies have shown that circulating levels of insulin-like growth factors are associated with MD and cross-talk between estrogen signaling and growth factors is necessary for cell proliferation in the breast. We evaluated single nucleotide polymorphisms (SNPs) in growth factor genes in association with MD changes after women stop EPT use.

Methods

We genotyped 191 SNPs in 13 growth factor pathway genes in 284 non-Hispanic white California Teachers Study participants who previously used EPT and collected their mammograms before and after quitting EPT. Percent MD was assessed using a computer-assisted method. Change in percent MD was calculated by subtracting percent MD of an ‘off-EPT’ mammogram from percent MD of an ‘on-EPT’ (i.e. baseline) mammogram. We used multivariable linear regression analysis to investigate the association between SNPs and change in percent MD. We calculated P-values corrected for multiple testing within a gene (P_adj).

Results

Rs1983210 in INHA and rs35539615 in IGFBP1/3 showed the strongest associations. Per minor allele of rs1983210, the absolute change in percent MD after stopping EPT use decreased by 1.80% (a difference in absolute change in percent MD) (P_adj= 0.021). For rs35539615, change in percent MD increased by 1.79% per minor allele (P_adj= 0.042). However, after applying a Bonferroni correction for the number of genes tested, these associations were no longer statistically significant.

Conclusions

Genetic variation in growth factor pathway genes INHA and IGFBP1/3 may predict longitudinal MD change after women quit EPT. The observed differences in EPT-associated changes in percent MD in association with these genetic polymorphisms are modest but may be clinically significant considering that the magnitude of absolute increase in percent MD reported from large clinical trials of EPT ranged from 3% to 7%.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4981-6) contains supplementary material, which is available to authorized users.

Follistatin Expression in Human Invasive Breast Tumors: Pathologic and Clinical Associations

Follistatin is a potent native activin antagonist that is expressed in the normal mammary gland and in different breast proliferative diseases. Despite experimental evidence that follistatin can modulate the breast cancer cell cycle, the clinical significance of follistatin expression in these tumors is unknown. The aim of this study was to correlate the intensity of follistatin expression in invasive breast cancer with some of its clinical and pathologic features, such as the disease stage and the hormonal receptor status. Paraffin blocks of tumor samples that had been fixed in buffered formalin were obtained from 154 women subjected to surgery for breast cancer between 2008 and 2012. Sections from all paraffin blocks were cut and processed together by immunohistochemistry using a commercial monoclonal antibody to human follistatin. The intensity of follistatin staining was unrelated to the menopausal status, the disease stage, the grade, progesterone receptor expression, and local or systemic recurrence. However, follistatin immunoreactivity was significantly stronger in estrogen receptor (ER)-negative tumors than in ER-positive tumors. These findings suggest that follistatin expression in invasive breast cancer is unrelated to the disease severity and the risk of recurrence, but is more intense in ER-negative tumors.

Prognostic value of follistatin-like 3 in human invasive breast cancer

Follistatin-like 3 (FSTL3) binds and inactivates activin, a growth factor involved with cell growth and differentiation. We have previously shown FSTL3 overexpression in invasive breast cancers, but its clinical relevance remained unexplored. Here we evaluate FSTL3 as a prognostic tool and its relation with clinical and pathological features of breast cancer. A cohort of 154 women diagnosed with invasive breast cancer between 2008 and 2012 was followed up for 5 years. Tumor samples were processed by immunohistochemistry to detect FSTL3 expression in tumor epithelium. FSTL3 expression was classified semiquantitatively and tested for possible correlation with age, menopause status, stage, tumor histological type and grade, estrogen receptor, progesterone receptor, and HER2 expression. Survival plots with Kaplan-Mayer statistics were used to assess whether FSTL3 expression predicted disease-free survival. Our findings show that FSTL3 staining was unrelated to menopausal status, histological type, disease stage, or receptor profile. However, the intensity of FSTL3 immunostaining correlated inversely with tumor size (r = -0.366, p<0.001) and with nuclear grade (p<0.01). The intensity of FSTL3 expression in the tumoral epithelium was not predictive of the disease-free survival (p = 0.991, log-rank test), even though the follow-up length and the study size were sufficient to detect a significant reduction in disease-free survival among women with stage III-IV compared to stage I-II disease (p<0.001). FSTL3 expression in invasive breast cancer is inversely associated with tumor size and nuclear grade but it does not predict disease relapse in the short term.

Increased Expression of Follistatin in Breast Cancer Reduces Invasiveness and Clinically Correlates with Better Survival

BACKGROUND/AIM

Activin and its antagonist follistatin (FST) have been implicated in several solid tumours. This study investigated the role of FST in breast cancer.

MATERIALS AND METHODS

FST expression was examined using reverse transcription polymerase chain reaction (RT-PCR), real-time quantitative polymerase chain reaction (qPCR) and immunohistochemistry in a cohort of breast cancer samples. Expression was correlated to pathological and prognostic parameters in our patient cohort. FST was overexpressed in MCF-7 cells and assays for growth and invasion were performed.

RESULTS

FST is expressed in breast tissue, in the cytoplasm of mammary epithelial cells. Expression was decreased in breast cancer tissue in comparison to normal mammary tissue. Over-expression of FST in vitro led to significantly increased growth rate and reduced invasion. Higher FST associates with lower-grade tumours and better survival.

CONCLUSION

Our results suggest a role for FST as a suppressor of invasion and metastasis in breast cancer.

Testes-specific protease 50 promotes cell proliferation via inhibiting activin signaling

Testes-specific protease 50 (TSP50), a novelly identified oncogene, has the capacity to induce cell proliferation, cell invasion and tumor growth. Further studies indicated that CAGA-luc (an activin-responsive reporter construct) reporter activity could be significantly suppressed by TSP50 overexpression, implying that the activin signaling may participate in TSP50-mediated cell proliferation. Here, we reported that TSP50 had an inhibitory effect on activin signaling. Mechanistic studies revealed that TSP50 could interact with ActRIIA, inhibit activin typeIreceptor (ActRIB) phosphorylation, repress Smad2/3 nuclear accumulation and finally promote cell proliferation by reducing the expression of activin signal target gene p27. Additionally, we found that ActRIB activation could reverse TSP50-mediated cell proliferation and tumor growth. Furthermore, analysis of human breast cancer specimens by immunohistochemistry indicated that TSP50 expression was negatively related to p-Smad2/3 and p27 protein levels. Most importantly, breast cancer diagnosis-related indicators such as tumor size, tumor grade, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER-2) levels, were correlated well with TSP50/p-Samd2/3 and TSP50/p27 expression status. Thus, our studies revealed a novel regulatory mechanism underlying TSP50-induced cell proliferation and provided a new favorable intervention target for the treatment of breast cancer.

Low miR-143/miR-145 Cluster Levels Induce Activin A Overexpression in Oral Squamous Cell Carcinomas, Which Contributes to Poor Prognosis

Deregulated expression of activin A is reported in several tumors, but its biological functions in oral squamous cell carcinoma (OSCC) are unknown. Here, we investigate whether activin A can play a causal role in OSCCs. Activin A expression was assessed by qPCR and immunohistochemistry in OSCC tissues. Low activin A-expressing cells were treated with recombinant activin A and assessed for apoptosis, proliferation, adhesion, migration, invasion and epithelial-mesenchymal transition (EMT). Those phenotypes were also evaluated in high activin A-expressing cells treated with follistatin (an activin A antagonist) or stably expressing shRNA targeting activin A. Transfections of microRNA mimics were performed to determine whether the overexpression of activin A is regulated by miR-143/miR-145 cluster. Activin A was overexpressed in OSCCs in comparison with normal oral mucosa, and high activin A levels were significantly associated with lymph node metastasis, tumor differentiation and poor survival. High activin A levels promoted multiple properties associated with malignant transformation, including decreased apoptosis and increased proliferation, migration, invasion and EMT. Both miR-143 and miR-145 were markedly downregulated in OSCC cell lines and in clinical specimens, and inversely correlated to activin A levels. Forced expression of miR-143 and miR-145 in OSCC cells significantly decreased the expression of activin A. Overexpression of activin A in OSCCs, which is controlled by downregulation of miR-143/miR-145 cluster, regulates apoptosis, proliferation and invasiveness, and it is clinically correlated with lymph node metastasis and poor survival.

Activin-A signaling promotes epithelial-mesenchymal transition, invasion, and metastatic growth of breast cancer

Background:

Activins belong to the transforming growth factor-β (TGF-β) superfamily of cytokines. Although the role of TGF-β in cancer progression has been highly advocated, the role of activin signaling in cancer is not well known. However, overexpression of activin-A has been observed in several cancers.

Aims:

The gene expression profile indicated higher expression of Activin-A in breast tumors. Hence the aim of this study was to evaluate the status and role of Activin signaling pathway in these tumors.

Methods:

Microarray analysis was performed to reveal gene expression changes in breast tumors. The results were validated by quantitative PCR and immunohistochemical analysis in two independent sets of normal and tumor samples. Further, correlation of activin expression with survival and distant metastasis was performed to evaluate its possible role in tumor progression. We used recombinant activin-A, inhibitors, overexpression, and knockdown strategies both in vitro and in vivo, to understand the mechanism underlying the protumorigenic role of this signaling pathway.

Results:

We report that activin-A signaling is hyperactivated in breast cancers as indicated by higher activin-A, phosphoSMAD2, and phosphoSMAD3 levels in advanced breast cancers. Bone morphogenetic proteins and molecules involved in this signaling pathway were downregulated, suggesting its suppression in breast cancers. Activin-A expression correlates inversely with survival and metastasis in advanced breast cancers. Further, activin-A promotes anchorage-independent growth, epithelial–mesenchymal transition, invasion, angiogenesis, and stemness of breast cancer cells. We show that activin-A-induced phenotype is mediated by SMAD signaling pathway. In addition, activin-A expression affects the tumor-forming ability and metastatic colonization of cancer cells in nude mice.

Conclusions:

These results suggest that activin-A has a critical role in breast cancer progression and, hence, targeting this pathway can be a valuable strategy in treating breast cancer patients.

The differential anti-tumour effects of zoledronic acid in breast cancer - evidence for a role of the activin signaling pathway

Background

Neo-adjuvant breast cancer clinical trials of zoledronic acid (ZOL) have shown that patients with oestrogen negative (ER-ve) tumours have improved disease outcomes. We investigated the molecular mechanism behind this differential anti-tumour effect according to ER status, hypothesising it may in part be mediated via the activin signaling pathway.

Methods

The effects of activin A, its inhibitor follistatin and zoledronic acid on proliferation of breast cancer cells was evaluated using either an MTS proliferation assay or trypan blue. Secretion of activin A and follistatin in conditioned medium (CM) from MDA-MB-231, MDA-MB-436, MCF7 and T47D cell lines were measured using specific ELISAs. The effects of ZOL on phosphorylation domains of Smad2 (pSmad2c + pSmad2L) were evaluated using immunofluorescence. Changes seen in vitro were confirmed in a ZOL treated subcutaneous ER-ve MDA-MB-436 xenograft model.

Results

Activin A inhibits proliferation of both ER-ve and oestrogen positive (ER + ve) breast cancer cells, an effect impaired by follistatin. ZOL significantly inhibits proliferation and the secretion of follistatin from ER-ve cells only, which increases the biological activity of the canonical activin A pathway by significantly increasing intracellular pSmad2c and decreasing nuclear accumulation of pSmad2L. In vivo, ZOL significantly decreases follistatin and pSmad2L expression in ER-ve subcutaneous xenografts compared to saline treated control animals.

Conclusions

This is the first report showing a differential effect of ZOL, according to ER status, on the activin pathway and its inhibitors in vitro and in vivo. These data suggest a potential molecular mechanism contributing to the differential anti-tumour effects reported from clinical trials and requires further evaluation in clinical samples.

Engineering TGF-β superfamily ligands for clinical applications

TGF-β superfamily ligands govern normal tissue development and homeostasis, and their dysfunction is a hallmark of many diseases. These ligands are also well defined both structurally and functionally. This review focuses on TGF-β superfamily ligand engineering for therapeutic purposes, in particular for regenerative medicine and musculoskeletal disorders. We describe the key discovery that structure-guided mutation of receptor-binding epitopes, especially swapping of these epitopes between ligands, results in new ligands with unique functional properties that can be harnessed clinically. Given the promising results with prototypical engineered TGF-β superfamily ligands, and the vast number of such molecules that remain to be produced and tested, this strategy is likely to hold great promise for the development of new biologics.

Inhibin at 90: from discovery to clinical application, a historical review

When it was initially discovered in 1923, inhibin was characterized as a hypophysiotropic hormone that acts on pituitary cells to regulate pituitary hormone secretion. Ninety years later, what we know about inhibin stretches far beyond its well-established capacity to inhibit activin signaling and suppress pituitary FSH production. Inhibin is one of the major reproductive hormones involved in the regulation of folliculogenesis and steroidogenesis. Although the physiological role of inhibin as an activin antagonist in other organ systems is not as well defined as it is in the pituitary-gonadal axis, inhibin also modulates biological processes in other organs through paracrine, autocrine, and/or endocrine mechanisms. Inhibin and components of its signaling pathway are expressed in many organs. Diagnostically, inhibin is used for prenatal screening of Down syndrome as part of the quadruple test and as a biochemical marker in the assessment of ovarian reserve. In this review, we provide a comprehensive summary of our current understanding of the biological role of inhibin, its relationship with activin, its signaling mechanisms, and its potential value as a diagnostic marker for reproductive function and pregnancy-associated conditions.

Activin A balance regulates epithelial invasiveness and tumorigenesis

Activin A (Act A) is a member of the TGFβ superfamily. Act A and TGFβ have multiple common downstream targets and have been described to merge in their intracellular signaling cascades and function. We have previously demonstrated that coordinated loss of E-cadherin and TGFβ receptor II (TβRII) results in epithelial cell invasion. When grown in three-dimensional organotypic reconstruct cultures, esophageal keratinocytes expressing dominant-negative mutants of E-cadherin and TβRII showed activated Smad2 in the absence of functional TβRII. However, we could show that increased levels of Act A secretion was able to induce Smad2 phosphorylation. Growth factor secretion can activate autocrine and paracrine signaling, which affects crosstalk between the epithelial compartment and the surrounding microenvironment. We show that treatment with the Act A antagonist Follistatin or with a neutralizing Act A antibody can increase cell invasion in organotypic cultures in a fibroblast- and MMP-dependent manner. Similarly, suppression of Act A with shRNA increases cell invasion and tumorigenesis in vivo. Therefore, we conclude that maintaining a delicate balance of Act A expression is critical for homeostasis in the esophageal microenvironment.

Pubertal high fat diet: effects on mammary cancer development

INTRODUCTION

Epidemiological studies linking dietary fat intake and obesity to breast cancer risk have produced inconsistent results. This may be due to the difficulty of dissociating fat intake from obesity, and/or the lack of defined periods of exposure in these studies. The pubertal mammary gland is highly sensitive to cancer-causing agents. We assessed how high fat diet (HFD) affects inflammation, proliferative, and developmental events in the pubertal gland, since dysregulation of these can promote mammary tumorigenesis. To test the effect of HFD initiated during puberty on tumorigenesis, we utilized BALB/c mice, for which HFD neither induces obesity nor metabolic syndrome, allowing dissociation of HFD effects from other conditions associated with HFD.

METHODS

Pubertal BALB/c mice were fed a low fat diet (12% kcal fat) or a HFD (60% kcal fat), and subjected to carcinogen 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumorigenesis.

RESULTS

HFD elevated mammary gland expression of inflammatory and growth factor genes at 3 and 4 weeks of diet. Receptor activator of nuclear factor kappa-B ligand (RANKL), robustly induced at 4 weeks, has direct mitogenic activity in mammary epithelial cells and, as a potent inducer of NF-κB activity, may induce inflammatory genes. Three weeks of HFD induced a transient influx of eosinophils into the mammary gland, consistent with elevated inflammatory factors. At 10 weeks, prior to the appearance of palpable tumors, there were increased numbers of abnormal mammary epithelial lesions, enhanced cellular proliferation, increased growth factors, chemokines associated with immune-suppressive regulatory T cells, increased vascularization, and elevated M2 macrophages. HFD dramatically reduced tumor latency. Early developing tumors were more proliferative and were associated with increased levels of tumor-related growth factors, including increased plasma levels of HGF in tumor-bearing animals. Early HFD tumors also had increased vascularization, and more intra-tumor and stromal M2 macrophages.

CONCLUSIONS

Taken together in this non-obesogenic context, HFD promotion of inflammatory processes, as well as local and systemically increased growth factor expression, are likely responsible for the enhanced tumorigenesis. It is noteworthy that although DMBA mutagenesis is virtually random in its targeting of genes in tumorigenesis, the short latency tumors arising in animals on HFD showed a unique gene expression profile, highlighting the potent overarching influence of HFD.

Cell-extrinsic consequences of epithelial stress: activation of protumorigenic tissue phenotypes

Introduction

Tumors are characterized by alterations in the epithelial and stromal compartments, which both contribute to tumor promotion. However, where, when, and how the tumor stroma develops is still poorly understood. We previously demonstrated that DNA damage or telomere malfunction induces an activin A-dependent epithelial stress response that activates cell-intrinsic and cell-extrinsic consequences in mortal, nontumorigenic human mammary epithelial cells (HMECs and vHMECs). Here we show that this epithelial stress response also induces protumorigenic phenotypes in neighboring primary fibroblasts, recapitulating many of the characteristics associated with formation of the tumor stroma (for example, desmoplasia).

Methods

The contribution of extrinsic and intrinsic DNA damage to acquisition of desmoplastic phenotypes was investigated in primary human mammary fibroblasts (HMFs) co-cultured with vHMECs with telomere malfunction (TRF2-vHMEC) or in HMFs directly treated with DNA-damaging agents, respectively. Fibroblast reprogramming was assessed by monitoring increases in levels of selected protumorigenic molecules with quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and immunocytochemistry. Dependence of the induced phenotypes on activin A was evaluated by addition of exogenous activin A or activin A silencing. In vitro findings were validated in vivo, in preinvasive ductal carcinoma in situ (DCIS) lesions by using immunohistochemistry and telomere-specific fluorescent in situ hybridization.

Results

HMFs either cocultured with TRF2-vHMEC or directly exposed to exogenous activin A or PGE₂ show increased expression of cytokines and growth factors, deposition of extracellular matrix (ECM) proteins, and a shift toward aerobic glycolysis. In turn, these "activated" fibroblasts secrete factors that promote epithelial cell motility. Interestingly, cell-intrinsic DNA damage in HMFs induces some, but not all, of the molecules induced as a consequence of cell-extrinsic DNA damage. The response to cell-extrinsic DNA damage characterized in vitro is recapitulated in vivo in DCIS lesions, which exhibit telomere loss, heightened DNA damage response, and increased activin A and cyclooxygenase-2 expression. These lesions are surrounded by a stroma characterized by increased expression of α smooth muscle actin and endothelial and immune cell infiltration.

Conclusions

Thus, synergy between stromal and epithelial interactions, even at the initiating stages of carcinogenesis, appears necessary for the acquisition of malignancy and provides novel insights into where, when, and how the tumor stroma develops, allowing new therapeutic strategies.

Genetic variants associated with breast size also influence breast cancer risk

BACKGROUND

While some factors of breast morphology, such as density, are directly implicated in breast cancer, the relationship between breast size and cancer is less clear. Breast size is moderately heritable, yet the genetic variants leading to differences in breast size have not been identified.

METHODS

To investigate the genetic factors underlying breast size, we conducted a genome-wide association study (GWAS) of self-reported bra cup size, controlling for age, genetic ancestry, breast surgeries, pregnancy history and bra band size, in a cohort of 16,175 women of European ancestry.

RESULTS

We identified seven single-nucleotide polymorphisms (SNPs) significantly associated with breast size (p<5.10(-8)): rs7816345 near ZNF703, rs4849887 and (independently) rs17625845 flanking INHBB, rs12173570 near ESR1, rs7089814 in ZNF365, rs12371778 near PTHLH, and rs62314947 near AREG. Two of these seven SNPs are in linkage disequilibrium (LD) with SNPs associated with breast cancer (those near ESR1 and PTHLH), and a third (ZNF365) is near, but not in LD with, a breast cancer SNP. The other three loci (ZNF703, INHBB, and AREG) have strong links to breast cancer, estrogen regulation, and breast development.

CONCLUSIONS

These results provide insight into the genetic factors underlying normal breast development and show that some of these factors are shared with breast cancer. While these results do not directly support any possible epidemiological relationships between breast size and cancer, this study may contribute to a better understanding of the subtle interactions between breast morphology and breast cancer risk.

Reduced expression of activin receptor-like kinase 7 in breast cancer is associated with tumor progression

To explore the clinical implication of activin receptor-like kinase 7 (ALK7) expression in breast cancer, we evaluated its protein level in six kinds of human breast tissue samples, including adjacent normal tissues, adenosis, breast fibroadenoma, ductal carcinoma in situ (DCIS), invasive ductal carcinoma (IDC), and lymph node metastases (LNM). Immunohistochemical analyses showed that ALK7 was more frequently and much more intensely expressed in adjacent normal tissues, adenosis, and fibroadenoma tissues than in malignant tissues (DCIS, IDC, and LNM). Furthermore, the ALK7 expression in primary tumors and the corresponding LNM was evaluated in parallel samples from 60 patients with IDC. Results showed that the ALK7 expression status in primary tumors and LNM was concordant in 53 patients (88%), suggesting that ALK7 expression was retained in LNM. Moreover, our results suggested that ALK7 expression inversely correlated with the tumor grade (P=0.009) and clinical stage (P=0.004) in IDC significantly. Finally, the effect of activin-ALK7 pathway on the breast cancer cell growth was elucidated, and results revealed that overexpression of ALK7 could restore the inhibitory effect of activin B on the growth of ALK7-negative breast cancer cell line, ZR-75-30. These findings provide the evidence that the reduction or lack of ALK7 expression may account for the loss of its ligand sensitivity of breast cancer cells, thereby leading to breast tumor progression.

The role of activin in mammary gland development and oncogenesis

TGFβ contributes to mammary gland development and has paradoxical roles in breast cancer because it has both tumor suppressor and tumor promoter activity. Another member of the TGFβ superfamily, activin, also has roles in the developing mammary gland, but these functions, and the role of activin in breast cancer, are not well characterized. TGFβ and activin share the same intracellular signaling pathways, but divergence in their signaling pathways are suggested. The purpose of this review is to compare the spatial and temporal expression of TGFβ and activin during mammary gland development, with consideration given to their functions during each developmental period. We also review the contributions of TGFβ and activin to breast cancer resistance and susceptibility. Finally, we consider the systemic contributions of activin in regulating obesity and diabetes; and the impact this regulation has on breast cancer. Elevated levels of activin in serum during pregnancy and its influence on pregnancy associated breast cancer are also considered. We conclude that evidence demonstrates that activin has tumor suppressing potential, without definitive indication of tumor promoting activity in the mammary gland, making it a good target for development of therapeutics.

The synthesis and secretion of inhibins

Inhibin A and B, dimeric glycoproteins comprising an α- and β((A/B))-subunit, negatively regulate follicle stimulating hormone (FSH) synthesis by the pituitary. The expression of α- and β-subunits within Sertoli cells of the testis and granulosa cells of the ovary is controlled by a range of transcription factors, including CREB, SP-1, Smads, and GATA factors. The inhibin α- and β-subunits are synthesized as precursor molecules consisting of an N-terminal propeptide and a C-terminal mature domain. Recently, we showed that hydrophobic residues within the propeptides of the α- and β-subunits interact noncovalently with their mature domains, maintaining the molecules in a conformation competent for dimerization. Dimeric precursors are cleaved by proprotein convertases and mature inhibins are secreted from the cell noncovalently associated with their propeptides. Propeptides may increase the half-life of inhibin A and B in circulation, but they are readily displaced in the presence of the high-affinity receptors, betaglycan, and ActRII.

LIM homeodomain transcription factor Isl-1 enhances follicle stimulating hormone-beta and luteinizing hormone-beta gene expression and mediates the activation of leptin on gonadotropin synthesis

The Lin-11, Isl-1, and Mec-3 (LIM) homeodomain transcription factor Isl-1 has been reported to be involved in pituitary development in the early stages of mouse embryogenesis. Our recent studies have shown that Isl-1 is mainly located in the pituitary gonadotropes throughout pituitary development and persists to adulthood. We still do not know the physiological functions of Isl-1 expression and its related mechanisms in the pituitary gland. The aim of the present study was to examine the hypothesis that Isl-1 is involved in regulating pituitary gonadotropin hormone (FSH/LH) production by activating FSHβ and LHβ gene expressions. We have shown that Isl-1 activates FSHβ and LHβ subunit promoters and endogenous gene transcription in LβT2 cells. In addition, Isl-1 overexpression significantly increased FSH synthesis and secretion but not LH. The actions of Isl-1 were not observed when the homeodomain or LIM1 domains are mutated. This demonstrates that Isl-1 induction of FSHβ and LHβ is by both direct and indirect binding of Isl-1 to DNA sequences. Furthermore, Isl-1 expressional level was up-regulated in LβT2 cells after exposure to GnRH, activin, and leptin. However, RNA interference-induced knockdown of Isl-1 significantly reduced the effect of leptin but did not obviously influence the stimulating effects of GnRH and activin on LH and FSH production. In conclusion, the results demonstrate that the LIM-homeodomain transcription factor Isl-1 functions to increase FSHβ/LHβ gene transcription, and mediates the effects of leptin on gonadotropin synthesis.

A multilevel data integration resource for breast cancer study

BACKGROUND

Breast cancer is one of the most common cancer types. Due to the complexity of this disease, it is important to face its study with an integrated and multilevel approach, from genes, transcripts and proteins to molecular networks, cell populations and tissues. According to the systems biology perspective, the biological functions arise from complex networks: in this context, concepts like molecular pathways, protein-protein interactions (PPIs), mathematical models and ontologies play an important role for dissecting such complexity.

RESULTS

In this work we present the Genes-to-Systems Breast Cancer (G2SBC) Database, a resource which integrates data about genes, transcripts and proteins reported in literature as altered in breast cancer cells. Beside the data integration, we provide an ontology based query system and analysis tools related to intracellular pathways, PPIs, protein structure and systems modelling, in order to facilitate the study of breast cancer using a multilevel perspective. The resource is available at the URL http://www.itb.cnr.it/breastcancer.

CONCLUSIONS

The G2SBC Database represents a systems biology oriented data integration approach devoted to breast cancer. By means of the analysis capabilities provided by the web interface, it is possible to overcome the limits of reductionist resources, enabling predictions that can lead to new experiments.

The CXCR4 antagonist AMD3100 suppresses hypoxia-mediated growth hormone production in GH3 rat pituitary adenoma cells

Pituitary adenomas produce the chemokine stromal cell-derived factor (SDF-1α/CXCL12) and its receptor, CXCR4. A recent study indicated that CXCL12 and CXCR4 are concomitantly up-regulated in hypoxia. The objective of this study was to analyze the molecular mechanism of hypoxia-mediated CXCR4 up-regulation and assess the effect of pharmacological inhibition of CXCR4 by the receptor blocker, AMD3100, on pituitary function. CXCR4 expression in pituitary adenoma tissues was determined by a tissue microarray analysis of 62 pituitary adenoma samples. CXCR4 expression was significantly elevated and positively correlated with Knosp grade in pituitary adenomas (P < 0.005), and was higher in macroadenoma and growth hormone (GH)-producing adenomas. Pre-operative serum GH levels were significantly correlated with CXCR4 levels in the microarray (P < 0.0001). The relative expression of genes/gene categories that were modulated by up-regulated CXCL12/CXCR4 signaling was determined by a comparative transcriptome analysis of wild-type and CXCR4-knockdown cells in normoxia and hypoxia using the rat GH-producing and prolactin-producing pituitary adenoma cell line, GH3. Real-time reverse transcriptase-polymerase chain reaction analysis (RT-PCR) showed that CXCR4 mRNA expression in GH3 cells was increased by hypoxia (1% oxygen), and a cDNA microarray analysis revealed that inhibin β-C expression was diminished. siRNA-mediated CXCR4 knockdown blocked the hypoxia-induced decrease in inhibin β-C mRNA expression, as did inhibition of CXCR4 activity with AMD3100. An ELISA study demonstrated that GH secretion by wild-type GH3 cells was moderately enhanced by hypoxia and further potentiated by exposure to recombinant SDF-1α/CXCL12 protein. Conversely, hypoxia-induced GH secretion was reduced in CXCR4-silenced cells and in cells treated with the CXCR4 antagonist, AMD3100, notwithstanding the presence of SDF-1α/CXCL12 protein. These latter observations reflect the failure of hypoxia to suppress expression of inhibin β-C in cells deficient in CXCR4 or in which CXCR4 signaling was blocked. Together, these results indicate that the SDF-1α/CXCL12-CXCR4 signaling pathway interfaces with the classical endocrine pathway to up-regulate GH production via suppression of inhibin β-C. Because it blocks CXCR4 and prevents hypoxia-induced down-regulation of inhibin β-C expression, AMD3100 has promise as a molecular-targeting agent in the treatment of GH-producing adenomas.

Overexpression of activin A in oral squamous cell carcinoma: association with poor prognosis and tumor progression

BACKGROUND

Both activin A, a member of transforming growth factor beta superfamily, and its inhibitor follistatin have been shown to be overexpressed in various cancers. We examined the potential role of activin A and follistatin in tissue and blood samples from patients with oral squamous cell carcinoma.

METHODS

For activin A and follistatin, the expression of tissue samples from 92 patients was examined by immunohistochemical study, and the serum levels of blood samples from 111 patients and 91 healthy controls were measured by enzyme-linked immunosorbent assay.

RESULTS

We found that overexpression of immunohistochemically detected activin A was correlated with positive N stage, poor histological differentiation, and perineural invasion (P = 0.029, 0.002, and 0.014, respectively). In survival analyses, patients with oral squamous cell carcinoma, whose tumors overexpressed activin A, had a worse prognosis for overall survival and disease-free survival (P = 0.009 and 0.007). However, expression of follistatin in tumor was not correlated with overall survival or disease-free survival. Serum activin A and follistatin levels in 111 untreated patients were neither significantly different from those of 91 control samples nor associated with any clinicopathological manifestations. In vitro suppression of activin A expression in OC3 cells using specific interfering RNA-attenuated cell proliferation, migration, and invasiveness.

CONCLUSIONS

These findings suggest that activin A overexpression in oral squamous cell carcinomas is associated with patients' survival and may contribute to tumor progression and metastasis.

Inhibin/activin-betaE subunit in normal and malignant human cervical tissue and cervical cancer cell lines

Inhibins are dimeric glycoproteins, composed of an alpha-subunit and one of two possible beta-subunits (betaA or betaB), with substantial roles in human reproduction and in endocrine-responsive tumours. Recently a novel beta subunit named betaE was described, although it is still unclear if normal or cancerous cervical epithelial cells as well as cervical cancer cell lines can synthesise the novel inhibin-betaE subunit. About 4 normal cervical tissue samples together with 10 specimens of well-differentiated squamous cervical cancer and adenocarcinoma of the cervix were immunohistochemical analyzed. Additionally, two cervical carcinoma cell lines (HeLa and CaSki) were analyzed by immunofluorescence and RT-PCR for the expression of this novel subunit. We demonstrated for the first time an immunolabelling of the inhibin-betaE subunit in normal and malignant cervical tissue, as well as cervical cancer cells. Although the physiological role is still quite unclear in cervical tissue, inhibin-betaE might play important roles in carcinogenesis. Moreover, the synthesis of this subunit in cervical carcinoma cell lines of squamous and glandular epithelial origins also allows the use of these cell lines in elucidating its functions in cervical cancer pathogenesis. However, since the expression of the inhibin-betaE is minimal in HeLa cells as assessed by immunofluorescence and RT-PCR, the CaSki cell line might be a better model for further functional experiments regarding cervical cancer pathogenesis.

DNA damage drives an activin a-dependent induction of cyclooxygenase-2 in premalignant cells and lesions

Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in the synthesis of prostaglandins. Its overexpression induces numerous tumor-promoting phenotypes and is associated with cancer metastasis and poor clinical outcome. Although COX-2 inhibitors are promising chemotherapeutic and chemopreventative agents for cancer, the risk of significant cardiovascular and gastrointestinal complications currently outweighs their potential benefits. Systemic complications of COX-2 inhibition could be avoided by specifically decreasing COX-2 expression in epithelial cells. To that end, we have investigated the signal transduction pathway regulating the COX-2 expression in response to DNA damage in breast epithelial cells. In variant human mammary epithelial cells that have silenced p16 (vHMEC), double-strand DNA damage or telomere malfunction results in a p53- and activin A-dependent induction of COX-2 and continued proliferation. In contrast, telomere malfunction in HMEC with an intact p16/Rb pathway induces cell cycle arrest. Importantly, in ductal carcinoma in situ lesions, high COX-2 expression is associated with high gammaH2AX, TRF2, activin A, and telomere malfunction. These data show that DNA damage and telomere malfunction can have both cell-autonomous and cell-nonautonomous consequences and can provide a novel mechanism for the propagation of tumorigenesis.

Differential expression of follistatin and FLRG in human breast proliferative disorders

Background

Activins are growth factors acting on cell growth and differentiation. Activins are expressed in high grade breast tumors and they display an antiproliferative effect inducing G0/G1 cell cycle arrest in breast cancer cell lines. Follistatin and follistatin- related gene (FLRG) bind and neutralize activins. In order to establish if these activin binding proteins are involved in breast tumor progression, the present study evaluated follistatin and FLRG pattern of mRNA and protein expression in normal human breast tissue and in different breast proliferative diseases.

Methods

Paraffin embedded specimens of normal breast (NB - n = 8); florid hyperplasia without atypia (FH - n = 17); fibroadenoma (FIB - n = 17); ductal carcinoma in situ (DCIS - n = 10) and infiltrating ductal carcinoma (IDC - n = 15) were processed for follistatin and FLRG immunohistochemistry and in situ hybridization. The area and intensity of chromogen epithelial and stromal staining were analyzed semi-quantitatively.

Results

Follistatin and FLRG were expressed both in normal tissue and in all the breast diseases investigated. Follistatin staining was detected in the epithelial cytoplasm and nucleus in normal, benign and malignant breast tissue, with a stronger staining intensity in the peri-alveolar stromal cells of FIB at both mRNA and protein levels. Conversely, FLRG area and intensity of mRNA and protein staining were higher both in the cytoplasm and in the nucleus of IDC epithelial cells when compared to NB, while no significant changes in the stromal intensity were observed in all the proliferative diseases analyzed.

Conclusion

The present findings suggest a role for follistatin in breast benign disease, particularly in FIB, where its expression was increased in stromal cells. The up regulation of FLRG in IDC suggests a role for this protein in the progression of breast malignancy. As activin displays an anti-proliferative effect in human mammary cells, the present findings indicate that an increased FST and FLRG expression in breast proliferative diseases might counteract the anti-proliferative effects of activin in human breast cancer.

microRNA miR-196a-2 and breast cancer: a genetic and epigenetic association study and functional analysis

Increasing evidence has suggested that microRNAs (miRNA) play an important role in tumorigenesis. As transcriptional regulators, altered miRNA expression may affect many cancer-related biological pathways, indicating that miRNAs can function as tumor suppressors and/or oncogenes. We first performed a genetic association analysis by screening genetic variants in 15 miRNA genes and detected that a common sequence variant in hsa-miR-196a-2 (rs11614913, C-->T) was significantly associated with decreased breast cancer risk (for homozygous variant: odds ratio, 0.44; 95% confidence interval, 0.28-0.70). Hypermethylation of a CpG island upstream (-700 bp) of the miR-196a-2 precursor was also associated with reduced breast cancer risk (odds ratio, 0.35; 95% confidence interval, 0.15-0.81). By delivering expression vectors containing either wild-type or mutant precursors of miR-196a-2 into breast cancer cells, we showed that this variant led to less efficient processing of the miRNA precursor to its mature form as well as diminished capacity to regulate target genes. A whole-genome expression microarray was done and a pathway-based analysis identified a cancer-relevant network formed by genes significantly altered following enforced expression of miR-196a-2. Mutagenesis analysis further showed that cell cycle response to mutagen challenge was significantly enhanced in cells treated with variant miR-196a-2 compared with cells treated with the wild-type. Taken together, our findings suggest that miR-196a-2 might have a potentially oncogenic role in breast tumorigenesis, and the functional genetic variant in its mature region could serve as a novel biomarker for breast cancer susceptibility.

Gene expression profiling of the tumor microenvironment during breast cancer progression

INTRODUCTION

The importance of the tumor microenvironment in breast cancer has been increasingly recognized. Critical molecular changes in the tumor stroma accompanying cancer progression, however, remain largely unknown. We conducted a comparative analysis of global gene expression changes in the stromal and epithelial compartments during breast cancer progression from normal to preinvasive to invasive ductal carcinoma.

METHODS

We combined laser capture microdissection and gene expression microarrays to analyze 14 patient-matched normal epithelium, normal stroma, tumor epithelium and tumor-associated stroma specimens. Differential gene expression and gene ontology analyses were performed.

RESULTS

Tumor-associated stroma undergoes extensive gene expression changes during cancer progression, to a similar extent as that seen in the malignant epithelium. Highly upregulated genes in the tumor-associated stroma include constituents of the extracellular matrix and matrix metalloproteases, and cell-cycle-related genes. Decreased expression of cytoplasmic ribosomal proteins and increased expression of mitochondrial ribosomal proteins were observed in both the tumor epithelium and the stroma. The transition from preinvasive to invasive growth was accompanied by increased expression of several matrix metalloproteases (MMP2, MMP11 and MMP14). Furthermore, as observed in malignant epithelium, a gene expression signature of histological tumor grade also exists in the stroma, with high-grade tumors associated with increased expression of genes involved in immune response.

CONCLUSIONS

Our results suggest that the tumor microenvironment participates in tumorigenesis even before tumor cells invade into stroma, and that it may play important roles in the transition from preinvasive to invasive growth. The immune cells in the tumor stroma may be exploited by the malignant epithelial cells in high-grade tumors for aggressive invasive growth.

Interactions between microenvironment and cancer cells in two animal models of bone metastasis

The preferential proliferation of cancer cells in the bone microenvironment is poorly characterised. Expression pattern of bone marrow and other organ microenvironment in contact with osteolytic (Walker W256) and osteoblastic (MatLyLu MLL) metastases were investigated. Fisher and Copenhagen rats received, respectively, W256 and MLL cells injection. Bone and soft tissues were analysed by immunochemistry for DKK1, cathepsin K, RANKL, MCSF or IL6 expression. Tartrate-resistant acid phosphatase (TRAcP)-positive cells were detected by a histoenzymatic technique. In bone, expressions of MCSF and DKK1 were shown in stromal cells of the bone marrow, in contact with metastatic foci of both tumours. Many stromal cells were found RANKL positive in the vicinity of the tumours. Cells expressing cathepsin K and multinucleated TRAcP+ cells were found in direct contact with trabeculae but also in bone marrow spaces near metastatic cells. In extraosseous tumours, cells in contact with malignant cells did not expressed DKK1, MCSF, cathepsin K and IL6. Some RANKL+ cells were found in the periphery of subcutaneous tumours but may represent Langerhans cells. Abnormal presence of TRAcP+ cells was never observed in the vicinity of malignant cells. Interaction between stromal and cancer cells induces the expression on the formers of characteristics leading to osteoclastogenesis only in the bone microenvironment.

Silencing of FLRG, an antagonist of activin, inhibits human breast tumor cell growth

Activin, a member of the transforming growth factor beta (TGFbeta) superfamily, regulates diverse processes, such as cellular growth and differentiation. There is increasing evidence that TGFbeta and its signaling effectors are key determinants of tumor cell behavior. Loss of sensitivity to TGFbeta-induced growth arrest is an important step toward malignancy. We previously characterized FLRG as an extracellular antagonist of activin. Here, we show that activin-induced growth inhibition is altered in FLRG-expressing breast cancer lines. Silencing FLRG induced growth inhibition, which is reversible upon addition of exogenous FLRG. We showed that FLRG silencing effects resulted from restoration of endogenous activin functions as shown by increased levels of phosphorylated smad2 and up-regulation of activin target gene transcripts. Furthermore, the growth inhibition induced by FLRG silencing was reversible by treatment with a soluble form of type II activin receptor. Finally, a strong expression of FLRG was observed in invasive breast carcinomas in contrast with the normal luminal epithelial cells in which FLRG was not detected. Our data provide strong evidence that endogenous FLRG contributes to tumor cell proliferation through antagonizing endogenous activin effects.

Isogenic normal basal and luminal mammary epithelial isolated by a novel method show a differential response to ionizing radiation

Epithelial cells within the normal breast duct seem to be the primary target for neoplastic transformation events that eventually produce breast cancer. Normal epithelial cells are easily isolated and propagated using standard techniques. However, these techniques almost invariably result in populations of cells that are largely basal in character. Because only approximately 20% of human breast cancers exhibit a basal phenotype, our understanding of the disease may be skewed by using these cells as the primary comparator to cancer. Further, because germ line mutations in BRCA1 yield breast cancers that are most often of the basal type, a comparison of normal basal and luminal cells could yield insight into the tissue and cell type specificity of this hereditary cancer susceptibility gene. In this report, we describe a simplified and efficient method for isolating basal and luminal cells from normal human breast tissue. These isogenic cells can be independently propagated and maintain phenotypic markers consistent with their respective lineages. Using these cultured cells, we show that basal and luminal cells exhibit distinct responses to ionizing radiation. Basal cells undergo a rapid but labile cell cycle arrest, whereas luminal cells show a much more durable arrest, primarily at the G(2)-M boundary. Molecular markers, including p53 protein accumulation, p53-activated genes, and BRCA1 nuclear focus formation all correlate with the respective cell cycle responses. Further, we show that short-term cultures of human breast tissue fragments treated with ionizing radiation show a similar phenomenon as indicated by the biphasic accumulation of p53 protein in the basal versus luminal layer. Together, these results indicate that normal basal cells have a transitory cell cycle arrest after DNA damage that may underlie their increased susceptibility to transformation after the loss of functional BRCA1.

LRH-1/NR5A2 cooperates with GATA factors to regulate inhibin alpha-subunit promoter activity

Inhibin alpha is the common subunit of the dimeric inhibin proteins known for their role in suppressing pituitary FSH secretion. In this study, we have examined the role of GATA factors and the nuclear receptor, LRH-1/NR5A2, in the regulation of inhibin alpha-subunit promoter activity. The inhibin alpha promoter contains two GATA-binding motifs that can be activated by GATA4 or GATA6. The GATA-dependence of the promoter was demonstrated by downregulating GATA expression in MA-10 cells using siRNA technology. We next examined whether GATA factors could cooperate with LRH-1, a factor recently proposed to be an important regulator of inhibin alpha-subunit transcription. Both GATA4 and GATA6 strongly synergized with LRH-1. Consistent with the cAMP-dependence of the inhibin alpha-subunit promoter, GATA/LRH-1 synergism was markedly enhanced by PKA and the co-activator protein CBP. Thus, our results identify LRH-1 as a new transcriptional partner for GATA factors in the regulation of inhibin alpha-subunit gene expression.

Postnatal regulation of germ cells by activin: the establishment of the initial follicle pool

Mammalian females enter puberty with follicular reserves that exceed the number needed for ovulation during a single lifetime. Follicular depletion occurs throughout reproductive life and ends in menopause, or reproductive senescence, when the follicle pool is exhausted. The mechanisms regulating the production of a species-specific initial follicle pool are not well understood. However, the establishment of a follicular reserve is critical to defining the length of reproductive cyclicity. Here we show that activin A (rh-ActA), a known regulator of follicle formation and growth in vitro, increased the number of postnatal mouse primordial follicles by 30% when administered to neonatal animals during the time of germline cyst breakdown and follicle assembly. This expansion in the initial follicle pool was characterized by a significant increase in both germ cell and granulosa cell proliferation. However, the excess follicles formed shortly after birth did not persist into puberty and both adult rh-ActA- and vehicle-treated animals demonstrated normal fertility. A follicle atresia kinetic constant (k(A)) was modeled for the two groups of animals, and consistent with the empirical data, the k(A) for rh-ActA-treated was twice that of vehicle-treated animals. Kinetic constants for follicle formation, follicle loss and follicle expansion from birth to postnatal day 19 were also derived for vehicle and rh-ActA treatment conditions. Importantly, introduction of exogenous rh-ActA revealed an intrinsic ovarian quorum sensing mechanism that controls the number of follicles available at puberty. We propose that there is an optimal number of oocytes present at puberty, and when the follicle number is exceeded, it occurs at the expense of oocyte quality. The proposed mechanism provides a means by which the ovary eliminates excess follicles containing oocytes of poor quality prior to puberty, thus maintaining fertility in the face of abnormal hormonal stimuli in the prepubertal period.

Activin signaling and its role in regulation of cell proliferation, apoptosis, and carcinogenesis

Activins, cytokine members of the transforming growth factor-beta superfamily, have various effects on many physiological processes, including cell proliferation, cell death, metabolism, homeostasis, differentiation, immune responses endocrine function, etc. Activins interact with two structurally related serine/threonine kinase receptors, type I and type II, and initiate downstream signaling via Smads to regulate gene expression. Understanding how activin signaling is controlled extracellularly and intracellularly would not only lead to more complete understanding of cell growth and apoptosis, but would also provide the basis for therapeutic strategies to treat cancer and other related diseases. This review focuses on the recent progress on activin-receptor interactions, regulations of activin signaling by ligand-binding proteins, receptor-binding proteins, and nucleocytoplasmic shuttling of Smad proteins.

Epigenetic remodeling in colorectal cancer results in coordinate gene suppression across an entire chromosome band

We report a new mechanism in carcinogenesis involving coordinate long-range epigenetic gene silencing. Epigenetic silencing in cancer has always been envisaged as a local event silencing discrete genes. However, in this study of silencing in colorectal cancer, we found common repression of the entire 4-Mb band of chromosome 2q.14.2, associated with global methylation of histone H3 Lys9. DNA hypermethylation within the repressed genomic neighborhood was localized to three separate enriched CpG island 'suburbs', with the largest hypermethylated suburb spanning 1 Mb. These data change our understanding of epigenetic gene silencing in cancer cells: namely, epigenetic silencing can span large regions of the chromosome, and both DNA-methylated and neighboring unmethylated genes can be coordinately suppressed by global changes in histone modification. We propose that loss of gene expression can occur through long-range epigenetic silencing, with similar implications as loss of heterozygosity in cancer.

The immunoexpressions and prognostic significance of inhibin alpha and beta human chorionic gonadotrophins (HCG) in breast carcinomas

PURPOSE

Pregnancy and hCG treatments are considered essential for inhibiting breast cancer. The effect of hCG is accompanied by the synthesis of inhibin, a transforming growth factor involved in cell differentiation and proliferation. Inhibin is considered a tumor suppressor, but its role in the breast is unclear. The aim of this study was to determine the frequency and tissue distribution of the expressions of inhibin-alpha and beta-hCG in breast cancer, and their prognostic relevance with other biological parameters.

MATERIALS AND METHODS

334 of formalin-fixed, paraffin embedded tissue blocks were selected, and then immunostained for inhibin-alpha and beta-hCG. The inhibin-alpha expression was compared with those of beta-hCG, ER, PR and HER-2/neu, as well as the tumor characteristics and recurrences.

RESULTS

Inhibin-alpha and beta-hCG were expressed in 87 (26.0%) and 44 cases (13.2%), respectively. Inhibin-alpha was found in 25.1% of infiltrating ductal carcinomas (67/267), 26.7% of intraductal carcinomas (8/30), 33.3% of lobular tumors (3/9), 80.0% of apocrine carcinomas (4/5) and 21.7% of the other types (5/23). Inhibin-alpha was correlated with beta-hCG (p<0.0001), PR (p=0.010) and HER-2/neu (p=0.021). HCG was focally expressed in the cytoplasm of the conventional types, but the apocrine type displayed diffusely intense cytoplasmic staining, which correlated with histological tumor types (p<0.001).

CONCLUSION

Inhibin was significantly correlated with the expressions of hCG, PR and HER-2/neu. Therefore, it might be a useful marker in the prevention and hormonal treatment of breast cancer, such as hCG and progesterone. HCG was expressed significantly higher in the apocrine type than the conventional types, suggesting it can be a useful adjunct in differentiating other cancer types.