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The evolution of chemoresistance is a fundamental characteristic of cancer that ultimately hampers its clinical management. However, it may be possible to improve patient outcomes significantly by a better understanding of resistance mechanisms, which cancers rely upon during the evolution to an untreatable state. Here we report an essential role of the stem cell reprogramming factor, PBX1, in mediating chemoresistance in ovarian carcinomas. In the clinical setting, high levels of PBX1 expression correlated with shorter survival in post-chemotherapy ovarian cancer patients. In tumor cells with low endogenous levels of PBX1, its enforced expression promoted cancer stem cell-like phenotypes, including most notably an increase in resistance to platinum-based therapy used most commonly for treating this disease. Conversely, silencing PBX1 in platinum-resistant cells that overexpressed PBX1 sensitized them to platinum treatment and reduced their stem-like properties. An analysis of published genome-wide chromatin immunoprecipitation data indicated that PBX1 binds directly to promoters of genes involved in stem cell maintenance and the response to tissue injury. We confirmed direct regulation of one of these genes, STAT3, demonstrating that the PBX1 binding motif at its promoter acted to positively regulate STAT3 transcription. We further demonstrated that a STAT3/JAK2 inhibitor could potently sensitize platinum-resistant cells to carboplatin and suppress their growth in vivo. Our findings offer a mechanistic rationale to target the PBX1/STAT3 axis to antagonize a key mechanism of chemoresistance in ovarian cancers and possibly other human cancers. Cancer Res; 76(21); 6351–61. ©2016 AACR.

Supplementary Tables 1-3, Supplementary Figures 1-7. Supplementary Table 1: Oligonucleotide primers used for qRT-PCR analysis. Supplementary Table 2: GSEA enrichment of KEGG functional pathways in lovastatin-regulated genes. Supplementary Table 3: Lovastatin affects expression of genes in glycolysis/gluconeogenesis pathway. Supplementary Figure 1: Daily administration of lovastatin prevents tumor growth in mogp-TAg transgenic mice. Supplementary Figure 2: Body weight and serum levels of cholesterol and triglyceride in mogp-TAg, SKOV3-IP, and OVCAR5 mouse tumor models. Supplementary Figure 3: Atorvastatin treatment delays growth of ovarian tumor xenografts. Supplementary Figure 4: Statin treatment increases transcript levels of LC3A and LC3B. Supplementary Figure 5: Scheme of the mevalonate pathway. Supplementary Figure 6: Applying GGPP or FPP as a single agent does not affect ovarian cancer cell proliferation. Supplementary Figure 7: Real-time qRT-PCR confirms knockdown efficiency of each siRNA.

Gene promoters identified by PBX1 ChIP-on-chip.

Including Supplementary Figures and Methods

Purpose: Statins are among the most frequently prescribed drugs because of their efficacy and low toxicity in treating hypercholesterolemia. Recently, statins have been reported to inhibit the proliferative activity of cancer cells, especially those with TP53 mutations. Because TP53 mutations occur in almost all ovarian high-grade serous carcinoma (HGSC), we determined whether statins suppressed tumor growth in animal models of ovarian cancer.Experimental Design: Two ovarian cancer mouse models were used. The first one was a genetically engineered model, mogp-TAg, in which the promoter of oviduct glycoprotein-1 was used to drive the expression of SV40 T-antigen in gynecologic tissues. These mice spontaneously developed serous tubal intraepithelial carcinomas (STICs), which are known as ovarian cancer precursor lesions. The second model was a xenograft tumor model in which human ovarian cancer cells were inoculated into immunocompromised mice. Mice in both models were treated with lovastatin, and effects on tumor growth were monitored. The molecular mechanisms underlying the antitumor effects of lovastatin were also investigated.Results: Lovastatin significantly reduced the development of STICs in mogp-TAg mice and inhibited ovarian tumor growth in the mouse xenograft model. Knockdown of prenylation enzymes in the mevalonate pathway recapitulated the lovastatin-induced antiproliferative phenotype. Transcriptome analysis indicated that lovastatin affected the expression of genes associated with DNA replication, Rho/PLC signaling, glycolysis, and cholesterol biosynthesis pathways, suggesting that statins have pleiotropic effects on tumor cells.Conclusions: The above results suggest that repurposing statin drugs for ovarian cancer may provide a promising strategy to prevent and manage this devastating disease. Clin Cancer Res; 21(20); 4652–62. ©2015 AACR.

Endometrium-related malignancies including uterine endometrioid carcinoma, ovarian clear cell carcinoma and ovarian endometrioid carcinoma are major types of gynecologic cancer, claiming more than 13,000 women’s lives annually in the United States. In vitro cell models that recapitulate “normal” endometrial epithelial cells and their malignant counterparts are critically needed to facilitate the studies of pathogenesis in endometrium-related carcinomas. To achieve this objective, we have established a human endometrial epithelial cell line, hEM3, through immortalization and clonal selection from a primary human endometrium culture. hEM3 exhibits stable growth in vitro without senescence. hEM3 expresses protein markers characteristic of the endometrial epithelium, and they include PAX8, EpCAM, cytokeratin 7/8, and ER. hEM3 does not harbor pathogenic germline mutations in genes involving DNA mismatch repair (MMR) or homologous repair (HR) pathways. Despite its unlimited capacity of in vitro proliferation, hEM3 cells are not transformed, as they are not tumorigenic in immunocompromised mice. The cell line is amenable for gene editing, and we have established several gene-specific knockout clones targeting ARID1A, a tumor suppressor gene involved in the SWI/SNF chromatin remodeling. Drug screening demonstrates that both HDAC inhibitor and PARP inhibitor are effective in targeting cells with ARID1A deletion. Together, our data support the potential of hEM3 as a cell line model for studying the pathobiology of endometrium-related diseases and for developing effective precision therapies. This study describes the characterization of a human endometrial epithelial cell line, hEM3. hEM3 is not transformed, can grow organoids, and does not harbor pathogenic mutations in genes involving DNA mismatch repair (MMR). hEM3 with ARID1A knockout has been generated for drug screening in an ARID1A-deficient and MMR-proficient context. In conclusion, hEM3 can be a model for studying endometrial pathogenesis.

Amplification and overexpression of the MYC oncogene in tumor cells, including ovarian cancer cells, correlates with poor responses to chemotherapy. As MYC is not directly targetable, we have analyzed molecular pathways downstream of MYC to identify potential therapeutic targets. Here we report that ovarian cancer cells overexpressing glutaminase (GLS), a target of MYC and a key enzyme in glutaminolysis, are intrinsically resistant to platinum-based chemotherapy and are enriched with intracellular antioxidant glutathione. Deprivation of glutamine by glutamine-withdrawal, GLS knockdown, or exposure to the GLS inhibitor CB-839 resulted in robust induction of reactive oxygen species in high GLS-expressing but not in low GLS-expressing ovarian cancer cells. Treatment with CB-839 rendered GLShigh cells vulnerable to the poly(ADP-ribose) polymerase (PARP) inhibitor, olaparib, and prolonged survival in tumor-bearing mice. These findings suggest consideration of applying a combined therapy of GLS inhibitor and PARP inhibitor to treat chemoresistant ovarian cancers, especially those with high GLS expression. Significance: Targeting glutaminase disturbs redox homeostasis and nucleotide synthesis and causes replication stress in cancer cells, representing an exploitable vulnerability for the development of effective therapeutics.

Although cancer has classically been regarded as a genetic disease of uncontrolled cell growth, the importance of the tumor microenvironment (TME) [1, 2] is continuously emphasized by the accumulating evidence that cancer growth is not simply dependent on the cancer cells themselves [3, 4] but also dependent on angiogenesis [5–8], inflammation [9, 10], and the supporting roles of cancer-associated fibroblasts (CAFs) [11–13]. After the discovery that CAFs are able to remodel the tumor matrix within the TME and provide the nutrients and chemicals to promote cancer cell growth [14], many studies have aimed to uncover the cross talk between cancer cells and CAFs. Moreover, a new paradigm in cancer metabolism shows how cancer cells act like “metabolic parasites” to take up the high-energy metabolites, such as lactate, ketone bodies, free fatty acids, and glutamine from supporting cells, including CAFs and cancer-associated adipocytes (CAAs) [15, 16]. This chapter provides an overview of the metabolic coupling between CAFs and cancer cells to further define the therapeutic options to disrupt the CAF-cancer cell interactions.

SUMMARY N-acetyl-aspartyl-glutamate (NAAG) is a peptide-based neurotransmitter that has been extensively studied in many neurological diseases. In this study, we show a specific role of NAAG in cancer. We found that NAAG is more abundant in higher grade cancers and is a source of glutamate in cancers expressing glutamate carboxypeptidase II (GCPII), the enzyme that hydrolyzes NAAG to glutamate and N-acetyl-aspartate (NAA). Knocking down GCPII expression through genetic alteration or pharmacological inhibition of GCPII results in a reduction of both glutamate concentrations and cancer growth. Moreover, targeting GCPII in combination with glutaminase inhibition accentuates these effects. These findings suggest that NAAG serves as an important reservoir to provide glutamate to cancer cells through GCPII when glutamate production from other sources is limited. Thus, GCPII is a viable target for cancer therapy, either alone or in combination with glutaminase inhibition., In Brief Nguyen et al. show that NAAG is more abundant in higher grade cancers and a source of glutamate in cancers expressing GCPII, the enzyme that hydrolyzes NAAG to glutamate and NAA. The results suggest that GCPII is a viable target for cancer therapy, either alone or in combination with glutaminase inhibition., Graphical Abstract

The tumor microenvironment (TME) is a complex biological structure surrounding tumor cells and includes blood vessels, immune cells, fibroblasts, adipocytes, and extracellular matrix (ECM) [1, 2]. These heterogeneous surrounding structures provide nutrients, metabolites, and signaling molecules to provide a cancer-friendly environment. The metabolic interplay between immune cells and cancer cells in the TME is a key feature not only for understanding tumor biology but also for discovering cancer cells’ vulnerability. As cancer immunotherapy to treat cancer patients and the use of metabolomics technologies become more and more common [3], the importance of the interplay between cancer cells and immune cells in the TME is emerging with respect to not only cell-to-cell interactions but also metabolic pathways. This interaction between immune cells and cancer cells is a complex and dynamic process in which immune cells act as a determinant factor of cancer cells’ fate and vice versa. In this chapter, we provide an overview of the metabolic interplay between immune cells and cancer cells and discuss the therapeutic opportunities as a result of this interplay in order to define targets for cancer treatment. It is important to understand and identify therapeutic targets that interrupt this cancerpromoting relationship between cancer cells and the surrounding immune cells, allowing for maximum efficacy of immune checkpoint inhibitors as well as other genetic and cellular therapies.

The use of metabolomics technologies and stable isotope labeling recently enabled us to discover an unexpected role of N-acetyl-aspartyl-glutamate (NAAG): NAAG is a glutamate reservoir for cancer cells. In the current study, we first found that glucose carbon contributes to the formation of NAAG and its precursors via glycolysis, demonstrating the existence of a glucose-NAAG-glutamate cycle in cancer cells. Second, we found that glucose carbon and, unexpectedly, glutamine carbon contribute to the formation of lactate via glutaminolysis. Importantly, lactate carbon can be incorporated into glucose via gluconeogenesis, demonstrating the existence of a glutamine-lactate-glucose cycle. While a glucose-lactate-glucose cycle was expected, the finding of a glutamine-lactate-glucose cycle was unforeseen. And third, we discovered that glutamine carbon is incorporated into γ-aminobutyric acid (GABA), revealing a glutamate-GABA-succinate cycle. Thus, NAAG, lactate, and GABA can play important roles as storage molecules for glutamate, glucose, and succinate carbon in oncogenic MYC-transformed P493 lymphoma B cells (MYC-ON cells) but not in non-oncogenic MYC-OFF cells. Altogether, examining the isotopic labeling patterns of metabolites derived from labeled 13C6-glucose or 13C515N2-glutamine helped reveal the presence of what we have named “metabolic reservoir cycles” in oncogenic cells.

The evolution of chemoresistance is a fundamental characteristic of cancer that ultimately hampers its clinical management. However, it may be possible to improve patient outcomes significantly by a better understanding of resistance mechanisms, which cancers rely upon during the evolution to an untreatable state. Here we report an essential role of the stem cell reprogramming factor, PBX1, in mediating chemoresistance in ovarian carcinomas. In the clinical setting, high levels of PBX1 expression correlated with shorter survival in post-chemotherapy ovarian cancer patients. In tumor cells with low endogenous levels of PBX1, its enforced expression promoted cancer stem cell-like phenotypes, including most notably an increase in resistance to platinum-based therapy used most commonly for treating this disease. Conversely, silencing PBX1 in platinum-resistant cells that overexpressed PBX1 sensitized them to platinum treatment and reduced their stem-like properties. An analysis of published genome-wide chromatin immunoprecipitation data indicated that PBX1 binds directly to promoters of genes involved in stem cell maintenance and the response to tissue injury. We confirmed direct regulation of one of these genes, STAT3, demonstrating that the PBX1 binding motif at its promoter acted to positively regulate STAT3 transcription. We further demonstrated that a STAT3/JAK2 inhibitor could potently sensitize platinum-resistant cells to carboplatin and suppress their growth in vivo. Our findings offer a mechanistic rationale to target the PBX1/STAT3 axis to antagonize a key mechanism of chemoresistance in ovarian cancers and possibly other human cancers. Cancer Res; 76(21); 6351–61. ©2016 AACR.

Motivation NGS techniques have been widely applied in genetic and epigenetic studies. Multiple ChIP-seq and RNA-seq profiles can now be jointly used to infer functional regulatory networks (FRNs). However, existing methods suffer from either oversimplified assumption on transcription factor (TF) regulation or slow convergence of sampling for FRN inference from large-scale ChIP-seq and time-course RNA-seq data. Results We developed an efficient Bayesian integration method (CRNET) for FRN inference using a two-stage Gibbs sampler to estimate iteratively hidden TF activities and the posterior probabilities of binding events. A novel statistic measure that jointly considers regulation strength and regression error enables the sampling process of CRNET to converge quickly, thus making CRNET very efficient for large-scale FRN inference. Experiments on synthetic and benchmark data showed a significantly improved performance of CRNET when compared with existing methods. CRNET was applied to breast cancer data to identify FRNs functional at promoter or enhancer regions in breast cancer MCF-7 cells. Transcription factor MYC is predicted as a key functional factor in both promoter and enhancer FRNs. We experimentally validated the regulation effects of MYC on CRNET-predicted target genes using appropriate RNAi approaches in MCF-7 cells. Availability and implementation R scripts of CRNET are available at http://www.cbil.ece.vt.edu/software.htm. Supplementary information Supplementary data are available at Bioinformatics online.

Purpose: Statins are among the most frequently prescribed drugs because of their efficacy and low toxicity in treating hypercholesterolemia. Recently, statins have been reported to inhibit the proliferative activity of cancer cells, especially those with TP53 mutations. Because TP53 mutations occur in almost all ovarian high-grade serous carcinoma (HGSC), we determined whether statins suppressed tumor growth in animal models of ovarian cancer. Experimental Design: Two ovarian cancer mouse models were used. The first one was a genetically engineered model, mogp-TAg, in which the promoter of oviduct glycoprotein-1 was used to drive the expression of SV40 T-antigen in gynecologic tissues. These mice spontaneously developed serous tubal intraepithelial carcinomas (STICs), which are known as ovarian cancer precursor lesions. The second model was a xenograft tumor model in which human ovarian cancer cells were inoculated into immunocompromised mice. Mice in both models were treated with lovastatin, and effects on tumor growth were monitored. The molecular mechanisms underlying the antitumor effects of lovastatin were also investigated. Results: Lovastatin significantly reduced the development of STICs in mogp-TAg mice and inhibited ovarian tumor growth in the mouse xenograft model. Knockdown of prenylation enzymes in the mevalonate pathway recapitulated the lovastatin-induced antiproliferative phenotype. Transcriptome analysis indicated that lovastatin affected the expression of genes associated with DNA replication, Rho/PLC signaling, glycolysis, and cholesterol biosynthesis pathways, suggesting that statins have pleiotropic effects on tumor cells. Conclusions: The above results suggest that repurposing statin drugs for ovarian cancer may provide a promising strategy to prevent and manage this devastating disease. Clin Cancer Res; 21(20); 4652–62. ©2015 AACR.

Chromatin immunoprecipitation with massively parallel DNA sequencing (ChIP-seq) has greatly improved the reliability with which transcription factor binding sites (TFBSs) can be identified from genome-wide profiling studies. Many computational tools are developed to detect binding events or peaks, however the robust detection of weak binding events remains a challenge for current peak calling tools. We have developed a novel Bayesian approach (ChIP-BIT) to reliably detect TFBSs and their target genes by jointly modeling binding signal intensities and binding locations of TFBSs. Specifically, a Gaussian mixture model is used to capture both binding and background signals in sample data. As a unique feature of ChIP-BIT, background signals are modeled by a local Gaussian distribution that is accurately estimated from the input data. Extensive simulation studies showed a significantly improved performance of ChIP-BIT in target gene prediction, particularly for detecting weak binding signals at gene promoter regions. We applied ChIP-BIT to find target genes from NOTCH3 and PBX1 ChIP-seq data acquired from MCF-7 breast cancer cells. TF knockdown experiments have initially validated about 30% of co-regulated target genes identified by ChIP-BIT as being differentially expressed in MCF-7 cells. Functional analysis on these genes further revealed the existence of crosstalk between Notch and Wnt signaling pathways.

ARID1A is a tumor suppressor gene that belongs to the switch/sucrose non-fermentable chromatin remodeling gene family. It is mutated in many types of human cancer with the highest frequency in endometrium-related ovarian and uterine neoplasms including ovarian clear cell, ovarian endometrioid, and uterine endometrioid carcinomas. We have previously reported that mutations in the promoter of human telomerase reverse transcriptase (TERT) rarely co-occur with the loss of ARID1A protein expression, suggesting a potential role of ARID1A in telomere biology. In this study, we demonstrate that ARID1A negatively regulates TERT transcriptional regulation and activity via binding to the regulatory element of TERT and promotes a repressive histone mode. Induction of ARID1A expression was associated with increased occupancy of SIN3A and H3K9me3, known transcription repressor and histone repressor marks, respectively. Thus, loss of ARID1A protein expression caused by inactivating mutations reactivates TERT transcriptional activity and confers a survival advantage of tumor cells by maintaining their telomeres.

Chicken oviductal epithelium produces large quantities of egg white protein in daily cycles. In this study, we cultured and characterized oviductal epithelial cells (OECs) from juvenile (10-wk-old) chickens and from actively laying (30-wk-old) hens. The juvenile OECs were maintained over passage 25 and were positive for toluidine blue, lectin-ConA, HPA, UEA-1, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR, whereas the adult OECs were cultured over passage 6 and were positive for toluidine blue, periodic acid-Schiff, lectin-ConA, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR. To investigate the optimal concentration of steroid hormones for inducing egg white protein genes in vitro, we examined the effects of estrogen, diethylstilbestrol, progesterone, and corticosterone on OECs. Results showed that oviduct-specific levels of avidin, ovalbumin, ovomucin, lysozyme, ESR1, and PGR gene expression were significantly elevated in steroid hormone-treated OECs compared with those of untreated cells (P < 0.05). Ovalbumi...

We recently developed bimodal germline chimera production approaches by transfer of primordial germ cells (PGCs) or embryonic germ cells (EGCs) into embryos and by transplantation of spermatogonial stem cells (SSCs) or germline stem cells (GSCs) into adult testes. This study was undertaken to investigate the reversible developmental unipotency of chicken germ cells using our established germline chimera production systems. First, we transferred freshly isolated SSCs from adult testis or in vitro cultured GSCs into stage X and stage 14–16 embryos, and we found that these transferred SSCs/GSCs could migrate to the recipient embryonic gonads. Of the 527 embryos that received SSCs or GSCs, 135 yielded hatchlings. Of 17 sexually mature males (35.3%), six were confirmed as germline chimeras through testcross analysis resulting in an average germline transmission efficiency of 1.3%. Second, PGCs/EGCs, germ cells isolated from embryonic gonads were transplanted into adult testes. The EGC transplantation induced germline transmission, whereas the PGC transplantation did not. The germline transmission efficiency was 12.5 fold higher (16.3 vs 1.3%) in EGC transplantation into testis (EGCs to adult testis) than that in SSC/GSC transfer into embryos (testicular germ cells to embryo stage). In conclusion, chicken germ cells from different developmental stages can (de)differentiate into gametes even after the germ cell developmental clock is set back or ahead. Use of germ cell reversible unipotency might improve the efficiency of germ cell-mediated germline transmission.

Although chicken spermatogonial stem cells (SCs) are important in spermatogenesis and transgenic research, little is known about these cells. Recently, our group constructed an in vitro culture system to establish germline stem cells (GSCs). To examine the mechanism of chicken spermatogonial SC development, we constructed a proteome map of GSCs from 4-week-old chicken testes. Soluble extracts of the GSCs were fractionated by 2-dimensional gel electrophoresis (pH 4-7). Several protein spots, including those that displayed significantly high levels, were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and liquid chromatography-tandem mass spectrometry. Of the 82/250 GSC spots examined, 56 yielded mass spectra that matched avian proteins found in the on-line databases. All of the identified proteins were classified into functional groups. This type of proteome map is an important resource for research on spermatogenesis and transgenesis.

We recently succeeded in inducing germline transmission by transferring chicken testicular cells into heterologous testes. This study was designed subsequently to identify pluripotent cells in the testicular cells, which would induce the germline transmission. Testicular cells retrieved from juvenile (4-wk-old) or adult (24-wk-old) White Leghorn (WL) chickens were stained with germ cell-specific markers anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-EMA1, anti-ITGA6, and anti-ITGB1 antibodies; 2C9; and lectin-Solanum tuberosum agglutinin (STA). The percentages of the cells that were positive for each marker were within the ranges of 0.33% -0.44% and 0.029%-0.072% of the total testicular cell population in the juvenile and adult, respectively, and significant (P < 0.0002) differences were detected between the ages. When 1 x 10(6) testicular cells were cultured in Dulbecco minimum essential medium-based medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (FGF2), and/or insulinlike growth factor 1 (IGF1), colony formation was detected only in LIF++FGF2-containing or LIF+FGF2+IGF1-containing medium during primary culture, and the supplementation of LIF+FGF2+IGF1 was the most efficient for maintaining the colony-forming cells through subculture. The established cells retrieved at the end of the primary culture or the 20th subpassage were positive for chicken germ cell-specific periodic acid-Schiff (PAS), EMA1, 2C9, SSEA1, SSEA3, SSEA4, ITGA6, and ITGB1; and lectin-STA markers (evaluated after 11th subpassage). Double staining of lectin-STA with anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-ITGA6, and anti-ITGB1 also was possible. They differentiated spontaneously into embryoid bodies after being cultured in LIF-free medium. We conclude that germline stem cell-like cells are present in chicken testicular cells retrieved from both juvenile and adult testes, which can be identified with the specific markers for primordial germ cells or embryonic germ cells.

In this study, we proposed a testis-mediated germline chimera production system based on the transplantation of testicular cells directly into heterologous testes. The testicular cells of juvenile (4-wk-old) or adult (24-wk-old) Korean Ogol chickens with a recessive pigmentation inhibitory gene, with or without prior culture, were injected (2 x 10(7) cells/head) into the seminiferous tubules of juvenile or adult recipients with White Leghorn with a dominant pigmentation inhibitory gene in a 2 x 2 factorial arrangement. The localization of transplanted cells into the inner space of the seminiferous tubules was confirmed within 24 h after injection. Subsequent testcross analyses showed that 7.8% (5/64) of the recipients had chimeric status in their testes. The periods of time from transfer to hatching of the first progeny with black feathers were 38 and 45 days for adult cells transplanted into an adult recipient, 188 days for adult cells into a juvenile recipient, and 137 days for juvenile cells into a juvenile recipient. Culture of the testicular cells derived both colony-forming and monolayer-forming cells. The colony-forming cells were stained positively for periodic acid Schiff solution, and further reacted with anti-SSEA-1, anti-SSEA-3, and anti-SSEA-4 antibodies both before and after culture for 15 days. In conclusion, it may be possible to develop the testis-mediated germline chimera production technique, which extends the feasibility of genetic manipulations in avian species.

The developmental similarity between the chicken and pheasant (Phasianus colchicus) allows the novel biotechnologies developed in the chicken to be applied to the production of transgenic pheasants and interspecies germline chimeras. To detect pheasant primordial germ cells (PGCs) efficiently, which is important for inducing germline transmission, the ultrastructure of PGCs and their reactivity to several antibodies (2C9, QB2, anti-SSEA-1, and QCR1) and periodic acid-Schiff's solution (PAS) were examined. To obtain PGCs, blood was taken from embryos incubated for 62-72 h or from gonads from embryos incubated for 156-216 h. The PGCs collected from both sources had the typical ultrastructure of pluripotent cells: a large nucleus with a distinct nucleolus, a high ratio of nuclear to cytoplasmic volume, and a distinct cytoplasmic membrane. In comparing the morphology of PGCs collected from different sites, more mitochondria and better-developed membrane microvilli were found in gonadal PGCs than in circulating PGCs. The nucleus of gonadal PGCs was flattened and had a large eccentrically positioned nucleolus. Of the antibodies tested, only QCR1 antibody reacted with an epitope in pheasant PGCs, and no specific signal was detected to other antibodies. The temporal change in the PGC populations in the blood and gonads of embryos was examined. In blood, the population was greater (P < 0.0001) in embryos incubated for 64 h than in embryos incubated for 62 or 66-72 h (31.4 versus 5.6-16.2 microL(-1)). In embryonic gonads, the number of PGCs increased continuously from 156 to 216 h of incubation (193-2,718 cells/embryo), although the ratio of PGCs to total gonadal cells did not change significantly (0.50-0.61%). In conclusion, pheasant PGCs have typical germ cell morphology and possess the QCR1 epitope. Circulating blood and the gonads of embryos incubated for 64 and 216 h, respectively, are good sources of PGCs.

SPIN90 is a widely expressed Nck-binding protein that contains one Src homology 3 (SH3) domain, three Pro-rich motifs, and a serine/threonine-rich region, and is known to participate in sarcomere assembly during cardiac myocyte differentiation. We used in vitro binding assays and yeast two-hybrid screening analysis to identify Nck, betaPIX, Wiscott-Aldrich syndrome protein (WASP), and ERK1 as SPIN90-binding proteins. It appears that betaPIX, WASP, and SPIN90 form a complex that interacts with Nck in a manner dependent upon cell adhesion to extracellular matrix. The betaPIX.WASP.SPIN90.Nck interaction was abolished in suspended and cytochalasin D-treated cells, but was recovered when cells were replated on fibronectin-coated dishes. The SPIN90.betaPIX.WASP complex was stable, even in suspended cells, suggesting SPIN90 serves as an adaptor molecule to recruit other proteins to Nck at focal adhesions. In addition, we found that overexpression of the SPIN90 SH3 domain or Pro-rich region, respectively, abolished SPIN90.Nck and SPIN90.betaPIX interactions, resulting in detachment of cells from extracellular matrix. SPIN90 was phosphorylated by ERK1, which was, itself, activated by cell adhesion and platelet-derived growth factor. Such phosphorylation of SPIN90 likely promotes the interaction of the SPIN90.betaPIX.WASP complex and Nck. It thus appears that the interaction of the betaPIX.WASP.SPIN90 complex with Nck is crucial for stable cell adhesion and can be dynamically modulated by SPIN90 phosphorylation that is dependent on cell adhesion and ERK activation.

Background: Cancer recurrence and chemoresistance contribute greatly to the high mortality of ovarian cancers; however, molecular players involved in these processes remain under-determined. Several theories have been proposed to account for the development of resistance to chemotherapeutic agents. One of the emerging concepts is tumor heterogeneity, which argues for the presence of different cell subpopulations in bulk tumor with varying degrees of tumor initiating potential and drug sensitivity. The fractions of cells with enhanced tumor initiating potential are referred to as cancer stem-like cells (CSC). These cells have defining “stemness” phenotypes, including unlimited cell division, repopulation by a minimum cell number and resistance to cytotoxic agents and irradiation. New Findings: To identify embryonic stem cell factors that are potentially involved in tumor recurrence and chemoresistance, we have screened expression levels of four of these factors by immunohistochemistry in pairs of matched recurrent and primary tumor tissues from 41 patients. Our data demonstrated that PBX1 is significantly up-regulated in recurrent/chemoresistant ovarian tumors. Moreover, PBX1 overexpression in ascites tumors correlates with shorter overall survival in post-chemotherapy ovarian cancer patients. When PBX1 is ectopically expressed, it promotes cancer stem cell-like phenotypes, including increased side population and ALDH1 activity, enhanced tumorigenicity at low cell density, and increased resistance to platinum-based therapy. In platinum-resistant cell lines that overexpress PBX1, silencing PBX1 expression using RNA interference sensitizes cells to platinum treatment and reduces their stem cell-like phenotypes. Gene expression and chromatin immunoprecipitation analyses identified PBX1 direct target genes involved in multi-drug resistance, stem cell maintenance, immunomodulation, and DNA damage response. In the TCGA ovarian cancer recurrent series, expression of several PBX1 direct target genes, including ABCA1, Nanog, BMP3, and ATM, is tightly associated with PBX1 expression, further supporting the tissue-level transcriptional regulation of these genes by PBX1. Conclusion: The above findings establish PBX1 as an upstream regulator of key functional networks that mediate cancer stem-like and drug resistant phenotypes. Studies on the hematopoietic system have indicated that PBX1 maintains a viable pool of quiescent stem cells. Recently, in a renal cell carcinoma system, chemotherapy has been shown to induce damage signaling and to stimulate cell division and repopulation of quiescent CSCs. We speculate that chemotherapy in ovarian cancer may induce comparable injury responses and trigger PBX1 signaling, which in turn may activate downstream networks that support CSC survival and create a microenvironment niche that is essential for CSC repopulation at the tissue level. Collectively, the association between PBX1 and a cascade of stemness pathways points to a potential Achilles's heel critical to responding to chemotherapy and developing chemoresistance and argues for the development of antagonists of PBX1 signaling as anticancer agents. Citation Format: Jin-Gyoung Jung, Tae-Hoen Kim, Emily Gerry, Jen-Chun Kuan, Ayse Ayhan, Ben Davidson, Ie-Ming Shih, Tian-Li Wang. PBX1, a transcriptional regulator, promotes stemness and chemoresistance in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A32.

Chicken oviductal epithelium produces large quantities of egg white protein in daily cycles. In this study, we cultured and characterized oviductal epithelial cells (OECs) from juvenile (10-wk-old) chickens and from actively laying (30-wk-old) hens. The juvenile OECs were maintained over passage 25 and were positive for toluidine blue, lectin-ConA, HPA, UEA-1, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR, whereas the adult OECs were cultured over passage 6 and were positive for toluidine blue, periodic acid-Schiff, lectin-ConA, WFA, WGA, anti-OVA, anti-ESR1, and anti-PGR. To investigate the optimal concentration of steroid hormones for inducing egg white protein genes in vitro, we examined the effects of estrogen, diethylstilbestrol, progesterone, and corticosterone on OECs. Results showed that oviduct-specific levels of avidin, ovalbumin, ovomucin, lysozyme, ESR1, and PGR gene expression were significantly elevated in steroid hormone-treated OECs compared with those of untreated cells (P0.05). Ovalbumin protein was also secreted into culture medium from hormone-treated OECs. In addition, to examine the application of OECs for avian transgenesis, we introduced human thrombopoietin (THPO)-expressing lentiviral vector controlled by a 3.5-kb ovalbumin promoter into cultured OECs, and THPO expression was significantly induced with diethylstilbestrol or progesterone in juvenile OECs (P0.05) and in adult OECs (P0.05). In conclusion, these data demonstrate the potential of cultured OECs as a model system for providing a better understanding of the regulation of gene expression and for the production of an avian transgenic bioreactor.

The massively parallel signature sequencing (MPSS) provides a greater depth of coverage than expressed sequence tag scan or microarray and provides a comprehensive expression profile. We used the MPSS technology to uncover gene expression profiling in the early embryonic gonads and primordial germ cells (PGCs) in the chicken. Total numbers of sequenced signatures were 1,012,533 and 995,676 for the PGCs and gonad, respectively. Using a noise distribution model, we found that 1.67% of all signatures are expressed at a higher level in PCGs and 2.81% of all signatures are expressed at a higher level in the gonad. The MPSS data are presented via an interactive web interface available at http://snugenome.snu.ac.kr/MPSS . The MPSS data have been submitted to the Gene Expression Omnibus of the National Center for Biotechnology Information (accession number GSM137300 and GSM137301 for PGCs and gonad, respectively).

Introduction: Resistance to chemotherapy represents a major obstacle to achieving long-term remission in ovarian cancer patients. Thereby, there is an unmet need to understand the pathogenesis of chemoresistance and to develop effective strategy to overcome drug resistance. To better understand the molecular etiology of drug resistance, we previously studied ovarian high-grade serous carcinoma (HGSC) to identify the genes and pathways they controlled in the development of chemoresistance. Toward this goal, we have demonstrated Notch3 pathway as one of the molecular contributors to carboplatin resistance in ovarian cancer cells. We further identified that PBX1, a TALE homeodomain transcription factor and proto-oncogene, mediates the functions of Notch3 signaling. This finding together with the fact that PBX1 is involved in several tumor-promoting functions raises the possibility that PBX1 may play an important role in chemoresistance. Thus, in this study, we aim to determine the roles of PBX1 in the development of carboplatin resistance in ovarian HGSC. Experimental procedures: Western blot and immunohistochemistry were performed to determine the expression levels of PBX1 in primary and recurrent/chemoresistant ovarian HGSC tissues and cell lines. To assess the functional roles of PBX1, PBX1 siRNA or cDNA was transfected into ovarian cancer cell lines. Stem cell-like characteristics were measured using an ALDH1 staining kit and flow cytometry to identify verapamil-sensitive side populations. A small molecule inhibitor targeting the binding between PBX1 and DNA was employed in mouse ovarian cancer xenograft models. Results: Immunohistochemistry demonstrated that PBX1 protein was upregulated in recurrent post-chemotherapy HGSCs as compared to the matched primary tumors. Western blot analysis showed that carboplatin-resistant (CR) ovarian cancer cell lines expressed higher protein levels of PBX1 than both parental cells and paclitaxel resistant cells. Gene knockdown of PBX1 using siRNA significantly suppressed growth in CR cell lines, indicating the dependence of CR cells on PBX1 expression. Since ALDH1, a stem cell marker, was also upregulated in CR cells as compared to the parental cells, we determined whether ectopic expression of PBX1 in PBX1-low ovarian cancer cells enhanced stem-cell phenotypes. Indeed, the fraction of verapamil-sensitive side population and the number of ALDH1 positive cells both increased in ovarian cells transfected with the PBX1-expressing plasmids, as were the stem cell associated markers including ABCB1 and GPR160. Moreover, we designed a novel small molecule inhibitor that disrupted the Pbx1/DNA complex and this PBX1 inhibitor potently interrupted the binding of PBX1 to the consensus DNA motif responsible for PBX1 binding. We observed an anti-proliferative effect of this inhibitor in CR ovarian cancer lines and an anti-tumorigenic effect in ovarian cancer mouse xenografts. Conclusion: This study demonstrates that PBX1 is a marker for recurrent post-chemotherapy HGSCs. Inactivating PBX1 using gene silencing and small molecule inhibitors enhances cytotoxicity of CR-resistant ovarian cancer cells. The above findings should have significant implications in cancer biology, and promise a novel strategy to combat ovarian cancer patients suffering from chemoresistance. Citation Format: Jin G. Jung, Joon T. Park, Alexader Stoeck, Tasmeen Hussain, Ren-Chin Wu, Ie-Ming Shih, Tian-Li Wang. Targeting PBX1 signaling to sensitize carboplatin cytotoxicity in ovarian cancer. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Drug Sensitivity and Resistance: Improving Cancer Therapy; Jun 18-21, 2014; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(4 Suppl): Abstract nr B15.

We recently succeeded in inducing germline transmission by transferring chicken testicular cells into heterologous testes. This study was designed subsequently to identify pluripotent cells in the testicular cells, which would induce the germline transmission. Testicular cells retrieved from juvenile (4-wk-old) or adult (24-wk-old) White Leghorn (WL) chickens were stained with germ cell-specific markers anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-EMA1, anti-ITGA6, and anti-ITGB1 antibodies; 2C9; and lectin-Solanum tuberosum agglutinin (STA). The percentages of the cells that were positive for each marker were within the ranges of 0.33% -0.44% and 0.029%-0.072% of the total testicular cell population in the juvenile and adult, respectively, and significant (P0.0002) differences were detected between the ages. When 1 x 10(6) testicular cells were cultured in Dulbecco minimum essential medium-based medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (FGF2), and/or insulinlike growth factor 1 (IGF1), colony formation was detected only in LIF++FGF2-containing or LIF+FGF2+IGF1-containing medium during primary culture, and the supplementation of LIF+FGF2+IGF1 was the most efficient for maintaining the colony-forming cells through subculture. The established cells retrieved at the end of the primary culture or the 20th subpassage were positive for chicken germ cell-specific periodic acid-Schiff (PAS), EMA1, 2C9, SSEA1, SSEA3, SSEA4, ITGA6, and ITGB1; and lectin-STA markers (evaluated after 11th subpassage). Double staining of lectin-STA with anti-SSEA1, anti-SSEA3, anti-SSEA4, anti-ITGA6, and anti-ITGB1 also was possible. They differentiated spontaneously into embryoid bodies after being cultured in LIF-free medium. We conclude that germline stem cell-like cells are present in chicken testicular cells retrieved from both juvenile and adult testes, which can be identified with the specific markers for primordial germ cells or embryonic germ cells.

In this study, we proposed a testis-mediated germline chimera production system based on the transplantation of testicular cells directly into heterologous testes. The testicular cells of juvenile (4-wk-old) or adult (24-wk-old) Korean Ogol chickens with a recessive pigmentation inhibitory gene, with or without prior culture, were injected (2 x 10(7) cells/head) into the seminiferous tubules of juvenile or adult recipients with White Leghorn with a dominant pigmentation inhibitory gene in a 2 x 2 factorial arrangement. The localization of transplanted cells into the inner space of the seminiferous tubules was confirmed within 24 h after injection. Subsequent testcross analyses showed that 7.8% (5/64) of the recipients had chimeric status in their testes. The periods of time from transfer to hatching of the first progeny with black feathers were 38 and 45 days for adult cells transplanted into an adult recipient, 188 days for adult cells into a juvenile recipient, and 137 days for juvenile cells into a juvenile recipient. Culture of the testicular cells derived both colony-forming and monolayer-forming cells. The colony-forming cells were stained positively for periodic acid Schiff solution, and further reacted with anti-SSEA-1, anti-SSEA-3, and anti-SSEA-4 antibodies both before and after culture for 15 days. In conclusion, it may be possible to develop the testis-mediated germline chimera production technique, which extends the feasibility of genetic manipulations in avian species.

This study was undertaken to develop novel markers for chicken primordial germ cells (PGCs), which are of potentially enormous value in transgenic research. Gonadal cells collected from 5.5-day-old chicken embryos were cultured in a Dulbecco's minimal essential medium and the PGC colonies formed during the primary culture period were subcultured three times. Characterization of the PGCs with the candidate marker reagents was performed on the mixed cell population 2 hours after seeding, after the primary culture period (day 10), and after the third passage (day 40). Mouse embryonic stem (ES) cells were used as controls. The cytochemical reagents investigated included periodic acid-Schiff (PAS) stain, antibodies to stage-specific embryonic antigens (SSEA-1, SSEA-3, and SSEA-4), antibody to epithelial membrane antigen (EMA)-1, antibodies to integrins alpha6 and beta1, several lectins (Solanum tuberosum agglutinin [STA], Dolichos biflorus agglutinin [DBA], concanavalin A agglutinin [ConA], and wheat germ agglutinin [WGA]), and double staining with antibodies to SSEA-1, SSEA-3, SSEA-4, integrin alpha6, or integrin beta1 and then with the lectin STA. Densitometric quantification was used to identify PGC-specific markers. The results showed that chicken PGCs were stained selectively by PAS and by antibodies to SSEA-1, SSEA-3, SSEA-4, EMA-1, integrin alpha6, and integrin beta1. The control mouse ES cells reacted with PAS, anti-SSEA-1, and anti-EMA-1 antibodies, as well as with antibodies to integrins alpha6 and beta1, but not with antibodies to SSEA-3 and SSEA-4. Chicken PGCs reacted with the lectins STA and DBA, but mouse ES cells reacted with STA and WGA. The results of double staining of PGC colonies subcultured three times showed that the intensity of staining was not altered by concomitant use of the marker reagents. This study demonstrated that, in addition to PAS and antibodies to SSEA-1 and EMA-1, new specific markers of chicken PGCs are recognized by the lectins STA and DBA and by antibodies to SSEA-3 and SSEA-4 and integrins alpha6 and beta1. Double staining using these newly developed markers might be the method of choice for rapid characterization of chicken PGCs.

Background Although chicken oviduct is a useful model and target tissue for reproductive biology and transgenesis, little is known because of the highly specific hormonal regulation and the lack of fundamental researches, including lectin-binding activities and glycobiology. Because lectin is attached to secreted glycoproteins, we hypothesized that lectin could be bound to secretory egg-white proteins, and played a crucial role in the generation of egg-white protein in the oviduct. Hence, the purpose of this study was to investigate the structural, histological and lectin-binding characteristics of the chicken oviductal magnum from juvenile and adult hens. Methods The oviductal magnums from juvenile and adult hens were prepared for ultrastructural analysis, qRT-PCR and immunostaining. Immunohistochemistry of anti-ovalbumin, anti-ESR1 and anti-PGR, and mRNA expression of egg-white genes and steroid hormone receptor genes were evaluated. Lectin histochemical staining was also conducted in juvenile and adult oviductal magnum tissues. Results The ultrastructural analysis showed that ciliated cells were rarely developed on luminal surface in juvenile magnum, but not tubular gland cells. In adult magnum, two types of epithelium and three types of tubular gland cells were observed. qRT-PCR analysis showed that egg-white genes were highly expressed in adult oviduct compared with the juvenile. However, mRNA expressions of ESR1 and PGR were considerably higher in juvenile oviduct than adult (P < 0.05). The immunohistochemical analysis showed that anti-ovalbumin antibody was detected in adult oviduct not in juvenile, unlikely anti-ESR1 and anti-PGR antibodies that were stained in both oviducts. In histological analysis, Toluidine blue was stained in juvenile and adult oviductal epithelia, and adult tubular glands located in the outer layer of oviductal magnum. In contrast, PAS was positive only in adult oviductal tubular gland. Lectins were selectively bound to oviductal epithelium, stroma, and tubular gland cells. Particularly, lectin-ConA and WGA were bound to electron-dense secretory granules in tubular gland. Conclusions The observation of ultrastructural analysis, mRNA expression, immunohistochemistry and lectin staining showed structural and physiological characterization of juvenile and adult oviductal magnum. Consequently, oviduct study could be helped to in vitro culture of chicken oviductal cells, to develop epithelial or tubular gland cell-specific markers, and to understand female reproductive biology and endocrinology.