Expression and action of transforming growth factor alpha in normal ovarian surface epithelium and ovarian cancer

High-fat diet and obesity are associated with differential angiogenic gene expression in epithelial ovarian cancer

OBJECTIVE

We sought to evaluate the association between diet and angiogenic biomarkers in KpB mice, and the association between these markers, body mass index (BMI), and overall survival (OS) in high-grade serous cancers (HGSC).

METHODS

Tumors previously obtained from KpB mice subjected to high-fat diets (HFD, n = 10) or low-fat diets (LFD, n = 10) were evaluated for angiogenesis based on CD-31 microvessel density (MVD). Data from prior microarray analysis (Agilent 244 K arrays) conducted in 10 mice were utilized to assess associations between diet and angiogenetic biomarkers. Agilent (mouse) and Affymetrix Human Genome U133a probes were linked to 162 angiogenic-related genes. The associations between biomarkers, BMI, and OS were evaluated in an HGSC internal database (IDB) (n = 40). Genes with unadjusted p < 0.05 were evaluated for association with OS in the TCGA-OV database (n = 339).

RESULTS

There was no association between CD-31 and diet in mice (p = 0.66). Sixteen angiogenic-related genes passed the p < 0.05 threshold for association with HFD vs. LFD. Transforming growth factor-alpha (TGFA) demonstrated 72% higher expression in HFD vs. LFD mice (p = 0.04). Similar to the mouse study, in our HGSC IDB, higher TGFA expression correlated with higher BMI (p = 0.01) and shorter survival (p = 0.001). In the TCGA-OV dataset, BMI data was not available and there was no association between TGFA and OS (p = 0.48).

CONCLUSIONS

HFD and obesity may promote tumor progression via differential modulation of TGFA. We were unable to confirm this finding in the TCGA dataset. Further evaluation of TGFA is needed to determine if this is a target unique to obesity-driven HGSC.

Ovarian cancer cells direct monocyte differentiation through a non-canonical pathway

BACKGROUND

Alternatively-activated macrophages (AAMs), an anti-inflammatory macrophage subpopulation, have been implicated in the progression of high grade serous ovarian carcinoma (HGSOC). Increased levels of AAMs are correlated with poor HGSOC survival rates, and AAMs increase the attachment and spread of HGSOC cells in vitro. However, the mechanism by which monocytes in the HGSOC tumor microenvironment are differentiated and polarized to AAMs remains unknown.

METHODS

Using an in vitro co-culture device, we cultured naïve, primary human monocytes with a panel of five HGSOC cell lines over the course of 7 days. An empirical Bayesian statistical method, EBSeq, was used to couple RNA-seq with observed monocyte-derived cell phenotype to explore which HGSOC-derived soluble factors supported differentiation to CD68+ macrophages and subsequent polarization towards CD163+ AAMs. Pathways of interest were interrogated using small molecule inhibitors, neutralizing antibodies, and CRISPR knockout cell lines.

RESULTS

HGSOC cell lines displayed a wide range of abilities to generate AAMs from naïve monocytes. Much of this variation appeared to result from differential ability to generate CD68+ macrophages, as most CD68+ cells were also CD163+. Differences in tumor cell potential to generate macrophages was not due to a MCSF-dependent mechanism, nor variance in established pro-AAM factors. TGFα was implicated as a potential signaling molecule produced by tumor cells that could induce macrophage differentiation, which was validated using a CRISPR knockout of TGFA in the OVCAR5 cell line.

CONCLUSIONS

HGSOC production of TGFα drives monocytes to differentiate into macrophages, representing a central arm of the mechanism by which AAMs are generated in the tumor microenvironment.

Connective tissue growth factor as a novel therapeutic target in high grade serous ovarian cancer

Ovarian cancer is the most common cause of death among women with gynecologic cancer. We examined molecular profiles of fibroblasts from normal ovary and high-grade serous ovarian tumors to identify novel therapeutic targets involved in tumor progression. We identified 2,300 genes that are significantly differentially expressed in tumor-associated fibroblasts. Fibroblast expression of one of these genes, connective tissue growth factor (CTGF), was confirmed by immunohistochemistry. CTGF protein expression in ovarian tumor fibroblasts significantly correlated with gene expression levels. CTGF is a secreted component of the tumor microenvironment and is being pursued as a therapeutic target in pancreatic cancer. We examined its effect in in vitro and ex vivo ovarian cancer models, and examined associations between CTGF expression and clinico-pathologic characteristics in patients. CTGF promotes migration and peritoneal adhesion of ovarian cancer cells. These effects are abrogated by FG-3019, a human monoclonal antibody against CTGF, currently under clinical investigation as a therapeutic agent. Immunohistochemical analyses of high-grade serous ovarian tumors reveal that the highest level of tumor stromal CTGF expression was correlated with the poorest prognosis. Our findings identify CTGF as a promoter of peritoneal adhesion, likely to mediate metastasis, and a potential therapeutic target in high-grade serous ovarian cancer. These results warrant further studies into the therapeutic efficacy of FG-3019 in high-grade serous ovarian cancer.

High levels of EGFR expression in tumor stroma are associated with aggressive clinical features in epithelial ovarian cancer

PURPOSE

The aim of this study was to investigate the clinical significance and biological function of epidermal growth factor receptor (EGFR) expressed in tumor stroma of epithelial ovarian cancer.

METHODS

Immunohistological staining of EGFR was evaluated in 242 patients with epithelial ovarian cancer. The correlations of EGFR expression in tumor stroma with clinicopathological features and with the expression level of Ki-67 were analyzed by SPSS software. Kaplan-Meier analysis and the Cox proportional hazard model were used to analyze the effect of EGFR expression in tumor stroma on the prognosis of patients with epithelial ovarian cancer. Meanwhile, the activities of proliferation and migration of tumor cells were detected when EGFR overexpressed in stroma cells.

RESULTS

EGFR expression in tumor stroma correlated significantly with clinical stage (χ (2)=7.002, P=0.008) and distant metastases (χ (2)=16.59, P<0.001). Furthermore, there was a significantly positive correlation between the level of EGFR expressed in tumor stroma and the level of Ki-67 expressed in tumor cells (χ (2)=6.120, P=0.013). Patients with high EGFR expression level in tumor stroma showed poor survival (P=0.002). Multivariate analysis showed that high expression of EGFR in tumor stroma was an independent predictor for epithelial ovarian cancer patients (hazard ratio =1.703; 95% confidence interval 1.125-2.578, P=0.012). Furthermore, stroma cells overexpressing EGFR could promote the proliferation and migration of adjacent tumor cells.

CONCLUSION

High expression of EGFR in tumor stroma correlates with aggressive clinical features in epithelial ovarian cancer, and is an independent prognostic factor.

Ovary and fimbrial stem cells: biology, niche and cancer origins

The mammalian ovary is covered by a single-layered epithelium that undergoes rupture and remodelling following each ovulation. Although resident stem cells are presumed to be crucial for this cyclic regeneration, their identity and mode of action have been elusive. Surrogate stemness assays and in vivo fate-mapping studies using recently discovered stem cell markers have identified stem cell pools in the ovary and fimbria that ensure epithelial homeostasis. Recent findings provide insights into intrinsic mechanisms and local extrinsic cues that govern the function of ovarian and fimbrial stem cells. These discoveries have advanced our understanding of stem cell biology in the ovary and fimbria, and lay the foundations for evaluating the contribution of resident stem cells to the initiation and progression of human epithelial ovarian cancer.

Regulation by heat shock protein 22 (HSPB8) of transforming growth factor-α-induced ovary cancer cell migration

Accumulating evidence suggests that heat shock proteins (HSPs) are implicated in progression of cancer. HSP22 (HSPB8), a small HSP, is recognized to be ubiquitously expressed in various tissues. However, the expression and the role of HSP22 in ovarian cancer remain to be clarified. In the present study, we investigated the involvement of HSP22 in transforming growth factor (TGF)-α-induced migration of ovarian cancer cells. The expression of HSP22 was detected in a serous ovarian cancer cell line, SKOV3.ip1. The migration was reduced by down-regulation of HSP22 expression. The TGF-α-induced migration was reduced by SB203580 (a p38 MAP kinase inhibitor), SP600125 (a SAPK/JNK inhibitor) and Y27632 (a Rho-kinase inhibitor). However, down-regulation of HSP22 had little effect on the TGF-α-induced phosphorylation of p38 MAP kinase, SAPK/JNK and MYPT, a target protein of Rho-kinase. The HSP22 expression was further analyzed in 20 resected specimens of human ovarian serous carcinoma. The expression of HSP22 was detected in all the twenty tissues (8.24-109.22 pg/mg protein), and the cases with highly expression of HSP22 showed a tendency to acquire the progressive ability. Our results strongly suggest that HSP22 acts as a positive regulator in TGF-α-induced migration of ovarian cancer cells, subsequently directing ovarian cancer toward progression.

Repeat estradiol exposure differentially regulates protein expression patterns for estrogen receptor and E-cadherin in older mouse ovarian surface epithelium: implications for replacement and adjuvant hormone therapies?

BACKGROUND

Estrogen replacement therapy increases risk for ovarian epithelial cancer, a cancer of mainly older women, yet the response of older ovarian surface epithelium (OSE) to repeat estrogen exposure overtime has not been studied. We have previously reported significant reductions in estrogen receptor (ER) protein expression, particularly the ERβ1 isoform, in older mouse OSE following a single depot estradiol injection. The current study examined OSE from older mice following a single, and repeat estradiol injection, given 14 days apart over 28 days.

METHODS

Cohorts of mice were sacrificed 48 hours following each estradiol injection, and at three other equidistant time points. Serum and ovarian tissue estradiol concentration was correlated to immunohistochemical and morphometric parameters used to identify evidence of OSE hyperplasia and hypertrophy. Using immunohistochemistry, E-cadherin expression was investigated in OSE 48 hours following both estradiol injections, while ERα and ERβ1 expression was examined in OSE following repeat estradiol exposure only.

RESULTS

First exposure to exogenous estradiol resulted in OSE hypertrophy and hyperplasia, and high levels of E-cadherin expression. In contrast, repeat estradiol exposure resulted in no OSE hyperplasia or hypertrophy, low levels of E-cadherin expression, high ERα and reduced ERβ1 protein expression in OSE, and low stromal ERα expression. Blood and ovarian tissue estradiol levels following repeat estradiol injection were half those recorded after a first dose equivalent injection, but remained significantly elevated above controls.

CONCLUSION

Repeat estradiol exposure leads to accumulation of estradiol in ovarian tissue, differentially regulating protein expression patterns for E-cadherin in OSE and ER in OSE and stroma.

In vitro regulation of sheep ovarian surface epithelium (OSE) proliferation by local ovarian factors

The ovarian surface epithelium (OSE) forms a lining around the entire ovary and actively participates in the ovulatory cycle. To investigate how specific growth factors and hormones affect OSE proliferation, the present study used sheep as a model to examine the effects of follicular and luteal products on the proliferation of sheep OSE cells in culture, and to analyse the influences of large antral follicles and corpora lutea (CL) on the expression of gonadotrophin receptors (FSHR and LHR) in the OSE. In the present study, follicular fluids from medium and large follicles, and extracts of corpora lutea stimulated the growth of OSE cells. The results of the present study showed that factors in the follicular fluid can induce OSE proliferative activity, and this stimulation effect could not be attributed to steroids in the follicular fluid since oestrogen and progesterone treatments failed to stimulate OSE cells. The expression of LH and FSH receptors over large follicles (5 mm or larger) was two and four times higher than those over stroma and CL, respectively. In conclusion, OSE proliferation in cycling sheep is associated with underlying developing follicles and CL, mediated by, at least in part, the up-regulation of gonadotrophin receptors, and facilitated by the action of mitogenic glycopeptides and growth factors, but not steroids.

Ethanol-TGFalpha-MEK signaling promotes growth of human hepatocellular carcinoma

BACKGROUND

Chronic ethanol intake is a significant risk factor for the development of cirrhosis and hepatocellular carcinoma (HCC). The effects of ethanol on extracellular signal-regulated kinase (ERK) activation, transforming growth factor alpha (TGF-alpha), and HCC growth were examined in this study.

METHODS

HepG2, SKHep, Hep3B human HCC cells, or normal human hepatocytes were treated with ethanol (0-100 mM), exogenous TGF-alpha, TGF-alpha neutralization antibody or the MEK inhibitor U0126. TGF-alpha levels were quantified by ELISA. Growth was determined by trypan blue-excluded cell counts. Cell cycle phase distribution was determined by flow cytometry. Protein expression was determined by Western blot.

RESULTS

Ethanol treatment (10-40 mM) increased ERK activation in HepG2 and SKHep HCC cells but not in Hep3B or human hepatocyte cells. Growth increased in HepG2 (174 +/- 29%, P < 0.05) and SKHep (149 +/- 12%, P < 0.05) cells in response to ethanol treatment. Correspondingly, ethanol increased S phase distribution in these cells. U0126 suppressed ethanol-induced growth increases. Ethanol treatment for 24 h also raised TGF-alpha levels in HepG2 cells (118%-198%) and SKHep cells (112%-177%). Exogenous administration of recombinant TGF-alpha mimicked the ethanol-induced growth in HepG2 and SKHep cells; TGF-alpha neutralization antibody effectively abrogated this effect. The TGF-a neutralization antibody also prevented ERK activation by ethanol in HepG2 cells.

CONCLUSIONS

These data demonstrate that clinically relevant doses of ethanol stimulate ERK-dependent proliferation of HCC cells. Ethanol up-regulates TGF-alpha levels in HCC cells and enhances growth through cell cycles changes, which appear to be mediated through TGF-alpha-MEK-ERK signaling. Ethanol-MEK signaling in normal hepatocytes is absent, suggesting that ethanol promotion of HCC growth may in part depend upon the acquisition of cancer-specific signaling by hepatocytes.

Clinical implications of the ErbB/epidermal growth factor (EGF) receptor family and its ligands in ovarian cancer

The ERBB or EGF receptor (EGFR) proto-oncogene family, which consists of four structurally-related transmembrane receptors (i.e., EGFR, ErbB2, ErbB3, and ErbB4), plays an etiological role in the molecular pathogenesis of cancer and is a key therapeutic target in many types of cancer, including ovarian cancer. These ErbB/EGF receptor tyrosine kinases play important physiologic roles in cell proliferation, survival, adhesion, motility, invasion, and angiogenesis. It is, therefore, not surprising that gene amplification, genetic mutation, and altered transcription/translation result in aberrant ErbB/EGF receptor expression and/or signal transduction, contributing to the development of malignant transformation. Clinically, the diagnostic, prognostic, and theragnostic significance of any single ErbB receptor and/or ErbB ligand is controversial, but generally, ErbB receptor overexpression has been correlated with poor prognosis and decreased therapeutic responsiveness in ovarian cancer patients. Thus, anticancer agents targeting ErbB/EGF receptors hold great promise for personalized cancer treatment. Yet, challenges remain in designing prospective clinical trials to assess the clinical utility of ErbB receptors and their ligands to diagnose cancer; to predict progression-free and overall survival, therapeutic responsiveness, and disease recurrence; and to monitor treatment responsiveness. Here, we review the tissue expression and serum biomarker studies that have evaluated the diagnostic, prognostic, and theragnostic utility of ErbB/EGF receptors, their circulating soluble isoforms (sEGFR/sErbBs), and their cognate ligands in ovarian cancer patients.

Gonadotropins and ovarian cancer

Ovarian epithelial cancer (OEC) accounts for 90% of all ovarian cancers and is the leading cause of death from gynecological cancers in North America and Europe. Despite its clinical significance, the factors that regulate the development and progression of ovarian cancer are among the least understood of all major human malignancies. The two gonadotropins, FSH and LH, are key regulators of ovarian cell functions, and the potential role of gonadotropins in the pathogenesis of ovarian cancer is suggested. Ovarian carcinomas have been found to express specific receptors for gonadotropins. The presence of gonadotropins in ovarian tumor fluid suggests the importance of these factors in the transformation and progression of ovarian cancers as well as being prognostic indicators. Functionally, there is evidence showing a direct action of gonadotropins on ovarian tumor cell growth. This review summarizes the key findings and recent advances in our understanding of these peptide hormones in ovarian cancer development and progression and their role in potential future cancer therapy. We will first discuss the supporting evidence and controversies in the "gonadotropin theory" and the use of animal models for exploring the involvement of gonadotropins in the etiology of ovarian cancer. The role of gonadotropins in regulating the proliferation, survival, and metastasis of OEC is next summarized. Relevant data from ovarian surface epithelium, which is widely believed to be the precursor of OEC, are also described. Finally, we will discuss the clinical applications of gonadotropins in ovarian cancer and the recent progress in drug development.

Ultrafast photoinduced deligation and ligation dynamics: DCM in micelle and micelle-enzyme complex

We report studies on diffusion controlled deligation and ligation dynamics of a probe ligand 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl) 4H-pyran (DCM) with cationic cetyltrimethylammonium bromide (CTAB) micelles. In order to investigate the effect of spatial heterogeneity on the dynamics we study the DCM labeled micelle upon complexation with an enzyme alpha-chymotrypsin (CHT). The variation of fluorescence line-width (Gamma(t)) of DCM in the complex and also in the micelle indicates the diffusion dynamics of DCM through various environments of different polarities. The temporal behavior of Gamma(t) reveals that at 50 mM CTAB concentration the excited DCM traverses 6.5 Angstrom distance from the surface of a host micelle (deligation) before entering to a stern layer of another adjacent micelle (ligation). From neutron scattering experiment the distance 6.5 Angstrom is found to be the thickness of a stern layer of CTAB micelle. No indication of ligation has been found at 2 mM CTAB concentration as the intermicellar distance is estimated to be very large (416 Angstrom) compared to the previous case. The dynamical behavior of Gamma(t) is also indicative of significantly slower diffusion of the ligand molecules (DCM) at the surface of the micelle in presence and absence of the enzyme compared to that in the bulk buffer. We have also studied the dynamics of solvation and local geometrical restriction on the probe DCM at the micellar surface with and without CHT. With picosecond time resolution, we found time constants of the solvation relaxation processes of the DCM labeled enzyme-micelle complex to be 230 ps (45%) and 870 ps (55%), which were comparable to those of the micelle without the enzyme. The time dependent anisotropy revealing local orientational motions of the probe in the complex was also found to be similar to that of DCM at the micellar surface in absence of CHT. These studies attempt to link the dynamical features for insight into the ligand mediated intercellular communication and the biological function of the enzyme alpha-chymotrypsin upon complexation with the CTAB micelle.

Apoptosis of bovine ovarian surface epithelial cells by Fas antigen/Fas ligand signaling

Ovarian surface epithelial cells (OSEs), a single layer of cells that cover the surface of the ovary, undergo turnover at the site of follicular rupture at ovulation. Greater than 90% of ovarian cancers arise from the OSEs. The objective of this study was to determine whether OSEs have the capacity to regulate their own demise through expression of Fas antigen (Fas) and Fas ligand (FasL) and activation of Fas-mediated apoptosis. In initial experiments, primary cultures of bovine OSEs responded to treatment with recombinant FasL by undergoing apoptosis. The percentage of cell death was not affected by the presence or absence of serum in the media or by co-treatment with interferon-γ, a treatment shown to potentiate Fas-mediated apoptosis in a number of cell types. Subsequent experiments tested the ability of stress-inducing drugs, anisomycin and daunorubicin, to promote apoptosis by stimulating an endogenous Fas–FasL pathway in OSEs. Treatment with FasL, anisomycin or daunorubicin induced cell death and this was suppressed by co-treatment with a peptide inhibitor of caspases, ZVAD. Treatment with anisomycin or daunorubicin in the presence of ZVAD increased expression of FasL mRNA and protein but did not alter expression of Fas mRNA or protein. Treatment of OSEs with a recombinant protein that blocks interaction of FasL with Fas (Fas:Fc) reduced apoptosis in response to anisomycin and daunorubicin, indicating that drug-induced apoptosis was mediated at least partially through endogenous Fas–FasL interactions. In summary, OSEs undergo apoptosis in response to stress-inducing drugs through activation of an endogenous Fas pathway.

Effects of epidermal growth factor/hydrocortisone on the growth and differentiation of human ovarian surface epithelium

OBJECTIVE

Ovarian surface epithelium (OSE), the precursor of the epithelial ovarian carcinomas, has limited growth potential in culture. Epidermal growth factor+hydrocortisone (EGF+HC) enhances its growth but induces epitheliomesenchymal transition (EMT). This study was undertaken to define the effects of EGF+HC and their reversibility, to optimize growth-promoting media, and to relate OSE phenotypes in vitro to physiologic states in vivo.

METHODS

OSE was cultured in media 199/MDCB105 or EBM (Clonetics) with 2% or 10% fetal bovine serum with or without 10 ng/mL EGF, 1.0 microg/mL HC, and 1.0 microg/mL bovine brain extract. Growth rates and growth potentials (population doublings [PD] to senescence) were defined, and growth patterns and expression of keratin and collagen types III and IV were compared with the ovarian cancer cell lines OVCAR3 and SKOV3.

RESULTS

EGF+HC increased growth potentials from 12-14 PD to 40-42 PD and reduced PD time from 53 hours to 20 hours. Without EGF+HC, OSE cells remained uniformly epithelial. EGF+HC induced EMT (mesenchymal shapes, reduced keratin, and production of collagenous extracellular matrix), but the EMT response varied greatly among OSE from different women. EMT was reversed over 1-2 weeks by subculture into EGF+HC-free medium in passage 1, but inconsistently thereafter. EGF+HC had no effect on the differentiation of ovarian carcinoma lines.

CONCLUSION

The phenotype of intact OSE in vivo is most closely reproduced in media without EGF+HC. EGF+HC enhances growth but initiates EMT, which likely mimics a repair response. Variations in EGF+HC-induced phenotypes point to the existence of OSE subpopulations with differing responsiveness to growth factors or steroids, which may relate to their susceptibility to malignant transformation.

Expression of transforming growth factor-α and hepatitis B surface antigen in human hepatocellular carcinoma tissues and its significance

AIM: To evaluate the expression of transforming growth factor-alpha (TGF-α) and hepatitis B surface antigen (HBsAg) in human hepatocellular carcinoma (HCC) tissues and its significance.

METHODS: Seventy specimens of HCC tissues were detected by immunohistochemical method. Five specimens of normal human liver tissues were used as control.

RESULTS: The TGF-α positive expression rates in HCC and its surrounding tissues were 74.3%(52/70) and 88.1%(52/59), respectively. TGF-α positive granules were mainly in the cytoplasm and fewer existed on the karyotheca. The TGF-α positive expressing rate in well differentiated HCC was significantly higher than that in moderately and poorly differentiated HCC (P < 0.05). The TGF-α positive expression also was observed in intrahepatic bile ducts (part of those were hyperplastic ducts). The HBsAg positive expression rates in HCC and its surrounding tissues were 21.4%(15/70) and 79.7%(47/59), respectively. HBsAg positive granules were in the cytoplasm, inclusion and on the karyotheca. There was a prominent positive correlation between TGF-α and HBsAg expression in HCC surrounding tissues (P < 0.05, γ = 0.34). TGF-α was usually existed with HBsAg in regenerated and/or dysplastic liver cells. In the five normal liver tissues, TGF-α and HBsAg were not detectable in hepatocytes and bile ducts.

CONCLUSION: Hepatitis B virus infection is closely related with hepatocarcinogenesis. The overexpression of TGF-α in the liver seems to be associated with the regeneration of hepatocytes injured by HBsAg. The continued expression of TGF-α might lead to dysplasia of liver cells and development of HCC. Furthermore, TGF-α might play a role in morphogenesis and regeneration of intrahepatic bile ducts.

Bone morphogenetic protein-4 acts as an ovarian follicle survival factor and promotes primordial follicle development

The growth and development of follicles within the ovary are highly dependent on autocrine and paracrine signaling involving growth factors from granulosa cells, theca cells, stromal interstitial cells, and the oocytes. The growth factor bone morphogenetic protein-4 (BMP-4) and its receptor (BMPR-IB) have been detected in ovaries, and a mutation in BMPR-IB has been associated with abnormal ovulation rate. The objective of the current study was to examine the role that BMP-4 plays in the early stages of primordial follicle development. Ovaries from 4-day-old rats were placed into a whole-ovary organ culture system for 2 wk to investigate the effect that treatment with exogenous BMP-4 has on early follicle development. BMP-4-treated ovaries had a significantly higher proportion of developing primary follicles and fewer arrested primordial follicles than did untreated controls. This indicates that BMP-4 promotes primordial follicle development and the primordial-to-primary follicle transition. Ovaries were also treated with neutralizing antibody against BMP-4 to determine effects of removing endogenously produced BMP-4. Interestingly, ovaries treated with BMP-4 antibody were markedly smaller than controls. This was associated with a progressive loss of oocytes and primordial follicles, a progressive increase in cellular apoptosis, and an accompanying loss of normal ovarian tissue morphology over time. Immunocytochemistry localized BMP-4 protein to isolated stromal cell populations, selected stromal cells (i.e., pretheca cells) associated with developing primordial follicles, and the basement membrane of follicles. Ovaries were treated with BMP-4 and RNA collected after organ culture to determine whether BMP-4 signaling affects expression of other growth factors. Kit ligand and basic fibroblast growth factor expression was unchanged, but TGFalpha expression was decreased in whole ovaries. Taken together, these data suggest that BMP-4 plays an important role in promoting the survival and development of primordial follicles in the neonatal ovary.

Discrete models of autocrine cell communication in epithelial layers

Pattern formation in epithelial layers heavily relies on cell communication by secreted ligands. Whereas the experimentally observed signaling patterns can be visualized at single-cell resolution, a biophysical framework for their interpretation is currently lacking. To this end, we develop a family of discrete models of cell communication in epithelial layers. The models are based on the introduction of cell-to-cell coupling coefficients that characterize the spatial range of intercellular signaling by diffusing ligands. We derive the coupling coefficients as functions of geometric, cellular, and molecular parameters of the ligand transport problem. Using these coupling coefficients, we analyze a nonlinear model of positive feedback between ligand release and binding. In particular, we study criteria of existence of the patterns consisting of clusters of a few signaling cells, as well as the onset of signal propagation. We use our model to interpret recent experimental studies of the EGFR/Rhomboid/Spitz module in Drosophila development.

Long-range signal transmission in autocrine relays

Intracellular signaling induced by peptide growth factors can stimulate secretion of these molecules into the extracellular medium. In autocrine and paracrine networks, this can establish a positive feedback loop between ligand binding and ligand release. When coupled to intercellular communication by autocrine ligands, this positive feedback can generate constant-speed traveling waves. To demonstrate that, we propose a mechanistic model of autocrine relay systems. The model is relevant to the physiology of epithelial layers and to a number of in vitro experimental formats. Using asymptotic and numerical tools, we find that traveling waves in autocrine relays exist and have a number of unusual properties, such as an optimal ligand binding strength necessary for the maximal speed of propagation. We compare our results to recent observations of autocrine and paracrine systems and discuss the steps toward experimental tests of our predictions.

Modeling and computational analysis of EGF receptor-mediated cell communication in Drosophila oogenesis

Autocrine signaling through the Epidermal Growth Factor Receptor (EGFR) operates at various stages of development across species. A recent hypothesis suggested that a distributed network of EGFR autocrine loops was capable of spatially modulating a simple single-peaked input into a more complex two-peaked signaling pattern, specifying the formation of a pair organ in Drosophila oogenesis (two respiratory appendages on the eggshell). To test this hypothesis, we have integrated genetic and biochemical information about the EGFR network into a mechanistic model of transport and signaling. The model allows us to estimate the relative spatial ranges and time scales of the relevant feedback loops, to interpret the phenotypic transitions in eggshell morphology and to predict the effects of new genetic manipulations. We have found that the proposed mechanism with a single diffusing inhibitor is sufficient to convert a single-peaked extracellular input into a two-peaked pattern of intracellular signaling. Based on extensive computational analysis, we predict that the same mechanism is capable of generating more complex patterns. At least indirectly, this can be used to account for more complex eggshell morphologies observed in related fly species. We propose that versatility in signaling mediated by autocrine loops can be systematically explored using experiment-based mechanistic models and their analysis.

EGF/ErbB receptor family in ovarian cancer

In summary, the EGF/ErbB family of receptor tyrosine kinases has been shown to play a key role in normal ovarian follicle development, and cell growth regulation of the ovarian surface epithelium. Disregulation of these normal growth regulatory pathways, including overexpression and/or mutation of EGFR/ErbB receptor family members, as well as elements of their downstream signalling pathways, have been shown to contribute to the etiology and progression of epithelial ovarian cancer. It is, therefore, not surprising that these gene products, and their related soluble receptor isoforms may have clinical utility as tumor and/or serum biomarkers of disease activity. Moreover, since several of these soluble receptor isoforms have potent growth inhibitory activity, and are naturally occurring in the circulation, they are ideal candidates for the development of novel therapeutics for the treatment of ovarian cancer patients.

Estrogen receptor beta in the sheep ovary during the estrous cycle and early pregnancy

Objectives were to sequence and examine the expression of the estrogen receptor beta (ERbeta) in the sheep ovary. The sequence of the ovine ERbeta (oERbeta) was determined using reverse-transcription polymerase chain reaction (RT-PCR) and cloning techniques. The reading frame of oERbeta contained 527 amino acids and exhibited high overall homology with cow (98%), rat (88%), and human (88%) ERbeta. In addition, an oERbeta isoform having a 139-base pair deletion (oERbeta1) was identified. The predicted amino acid sequence of this isoform is lacking the ligand-binding and carboxyl-terminal transactivation domains. The oERbeta protein and mRNA were determined in ovaries obtained from ewes on Days 0 (first day of estrus), 2, 6, and 10 of the estrous cycle and Day 30 of gestation. Immunohistochemistry showed that oERbeta protein was located in granulosa cells, the ovarian surface epithelium, endothelium, and Day 2 corpus luteum (CL). Weak immunostaining for ERbeta was detected in the theca interna. Relative steady-state amounts of oERbeta mRNA in the CL were determined using semiquantitative RT-PCR. Amounts of oERbeta mRNA were greater (P < 0.05) during CL formation (Day 2) than at later stages. The oERbeta to oERbeta1 mRNA ratio was lower (P < 0.05) on Day 2 than on Day 10 or Day 30 due to a decrease in amounts of oERbeta1. Results indicate that the oERbeta is a 527-amino acid protein expressed in specific cells of the ovary. Changes in relative amounts of full-length oERB and a deletion isoform in CL occurred during the estrous cycle, suggesting that these two types of ERbeta might regulate estrogen actions during early CL development in sheep.