Establishment and characterization of human ovarian carcinoma cell lines

Inhibition of Poly ADP-Ribose Glycohydrolase Sensitizes Ovarian Cancer Cells to Poly ADP-Ribose Polymerase Inhibitors and Platinum Agents

Background

Poly ADP-ribose glycohydrolase (PARG) is responsible for the catabolism of PARP-synthesized PAR to free ADP-ribose. Inhibition of PARG leads to DNA repair interruption and consequently induces cell death. This study aims to evaluate the effect of a PARG inhibitor (PARGi) on epithelial ovarian cancer (OC) cell lines, alone and in combination with a PARP inhibitor (PARPi) and/or Cisplatin.

Methods

PARG mRNA levels were studied in three different OC datasets: TCGA, Hendrix, and Meyniel. PARG protein levels were assessed in 100 OC specimens from our bio-bank. The therapeutic efficacy of PARGi was assessed using cell migration and clonogenic formation assays. Flow cytometry was used to evaluate the cell apoptosis rate and the changes in the cell cycle.

Results

PARG protein was highly expressed in 34% of the OC tumors and low expression was found in another 9%. Similarly, Hendrix, Meyneil and TCGA databases showed a significant up-regulation in PARG mRNA expression in OC samples as compared to normal tissue (P=0.001, P=0.005, P=0.005, respectively). The use of PARGi leads to decreased cell migration. PARGi in combination with PARPi or Cisplatin induced decreased survival of cells as compared to each drug alone. In the presence of PARPi and Cisplatin, PARG knockdown cell lines showed significant G2/M cell cycle arrest and cell death induction.

Conclusions

PARG inhibition appears as a complementary strategy to PARP inhibition in the treatment of ovarian cancer, especially in the presence of homologous recombination defects.

BRCA1 intronic Alu elements drive gene rearrangements and PARP inhibitor resistance

BRCA1 mutant carcinomas are sensitive to PARP inhibitor (PARPi) therapy; however, resistance arises. BRCA1 BRCT domain mutant proteins do not fold correctly and are subject to proteasomal degradation, resulting in PARPi sensitivity. In this study, we show that cell lines and patient-derived tumors, with highly disruptive BRCT domain mutations, have readily detectable BRCA1 protein expression, and are able to proliferate in the presence of PARPi. Peptide analyses reveal that chemo-resistant cancers contain residues encoded by BRCA1 intron 15. Mechanistically, cancers with BRCT domain mutations harbor BRCA1 gene breakpoints within or adjacent to Alu elements in intron 15; producing partial gene duplications, inversions and translocations, and terminating transcription prior to the mutation-containing BRCT domain. BRCA1 BRCT domain-deficient protein isoforms avoid mutation-induced proteasomal degradation, support homology-dependent DNA repair, and promote PARPi resistance. Taken together, Alu-mediated BRCA1 gene rearrangements are responsible for generating hypomorphic proteins, and may represent a biomarker of PARPi resistance.

BRCA1-No Matter How You Splice It

BRCA1 (breast cancer 1, early onset), a well-known breast cancer susceptibility gene, is a highly alternatively spliced gene. BRCA1 alternative splicing may serve as an alternative regulatory mechanism for the inactivation of the BRCA1 gene in both hereditary and sporadic breast cancers, and other BRCA1-associated cancers. The alternative transcripts of BRCA1 can mimic known functions, possess unique functions compared with the full-length BRCA1 transcript, and in some cases, appear to function in opposition to full-length BRCA1 In this review, we will summarize the functional "naturally occurring" alternative splicing transcripts of BRCA1 and then discuss the latest next-generation sequencing-based detection methods and techniques to detect alternative BRCA1 splicing patterns and their potential use in cancer diagnosis, prognosis, and therapy.

Chemosensitivity of BRCA1-Mutated Ovarian Cancer Cells and Established Cytotoxic Agents

OBJECTIVE

Serous adenocarcinomas that arise in patients with inherited mutations in the tumor suppressor genes BRCA1 and BRCA2 are initially well treatable with platinum/paclitaxel. For recurrent disease in patients with BRCA1 or BRCA2 mutations, olaparib treatment is available. To study additional therapeutic regimens, a better understanding of the cellular and molecular mechanisms of the tumors in in vitro models is important.

METHODS/MATERIALS

From a high-grade serous ovarian tumor of a BRCA1 mutation carrier, we established 3 distinct cell line subclones, OVCA-TR3.1, -2, and -3. Immunohistochemical characterization, flow cytometric analyses, chemosensitivity, and somatic mutation profiling were performed.

RESULTS

The cell lines expressed AE1/AE3, Pax8, WT-1, OC125, estrogen receptor (ER), and p53, comparable to the primary tumor. Synergism could be shown in the combination treatment eremophila-1-(10)-11(13)-dien-12,8β-olide (EPD), with cisplatin, whereas combination with olaparib did not show synergism. Eremophila-1-(10)-11(13)-dien-12,8β-olide, a sesquiterpene lactone, is a novel chemotherapeutic agent. The inherited BRCA1 c.2989_2990dupAA mutation was confirmed in the cell lines. Loss of heterozygosity of BRCA1 was detected in each cell line, as well as a homozygous TP53 c.722C>A mutation. Flow cytometry showed that all cell lines had a distinct DNA index.

CONCLUSIONS

Three new isogenic ovarian cancer cell lines were developed from a patient with a germ line BRCA1 mutation. Chemosensitivity profiling of the cell lines showed high tolerance for olaparib. Treatment with EPD proved synergistic with cisplatin. The effects of EPD will be further investigated for future clinical efficacy.

DNA hypomethylation-mediated activation of Cancer/Testis Antigen 45 (CT45) genes is associated with disease progression and reduced survival in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is a highly lethal malignancy due to a lack of early detection approaches coupled with poor outcomes for patients with clinically advanced disease. Cancer-testis (CT) or cancer-germline genes encode antigens known to generate spontaneous anti-tumor immunity in cancer patients. CT45 genes are a recently discovered 6-member family of X-linked CT genes with oncogenic function. Here, we determined CT45 expression in EOC and fully defined its epigenetic regulation by DNA methylation. CT45 was silent and hypermethylated in normal control tissues, but a large subset of EOC samples showed increased CT45 expression in conjunction with promoter DNA hypomethylation. In contrast, copy number status did not correlate with CT45 expression in the TCGA database for EOC. CT45 promoter methylation inversely correlated with both CT45 mRNA and protein expression, the latter determined using IHC staining of an EOC TMA. CT45 expression was increased and CT45 promoter methylation was decreased in late-stage and high-grade EOC, and both measures were associated with poor survival. CT45 hypomethylation was directly associated with LINE-1 hypomethylation, and CT45 was frequently co-expressed with other CT antigen genes in EOC. Decitabine treatment induced CT45 mRNA and protein expression in EOC cells, and promoter transgene analyses indicated that DNA methylation directly represses CT45 promoter activity. These data verify CT45 expression and promoter hypomethylation as possible prognostic biomarkers, and suggest CT45 as an immunological or therapeutic target in EOC. Treatment with decitabine or other epigenetic modulators could provide a means for more effective immunological targeting of CT45.

In vitro Development of Chemotherapy and Targeted Therapy Drug-Resistant Cancer Cell Lines: A Practical Guide with Case Studies

The development of a drug-resistant cell line can take from 3 to 18 months. However, little is published on the methodology of this development process. This article will discuss key decisions to be made prior to starting resistant cell line development; the choice of parent cell line, dose of selecting agent, treatment interval, and optimizing the dose of drug for the parent cell line. Clinically relevant drug-resistant cell lines are developed by mimicking the conditions cancer patients experience during chemotherapy and cell lines display between two- and eight-fold resistance compared to their parental cell line. Doses of drug administered are low, and a pulsed treatment strategy is often used where the cells recover in drug-free media. High-level laboratory models are developed with the aim of understanding potential mechanisms of resistance to chemotherapy agents. Doses of drug are higher and escalated over time. It is common to have difficulty developing stable clinically relevant drug-resistant cell lines. A comparative selection strategy of multiple cell lines or multiple chemotherapeutic agents mitigates this risk and gives insight into which agents or type of cell line develops resistance easily. Successful selection strategies from our research are presented. Pulsed-selection produced platinum or taxane-resistant large cell lung cancer (H1299 and H460) and temozolomide-resistant melanoma (Malme-3M and HT144) cell lines. Continuous selection produced a lapatinib-resistant breast cancer cell line (HCC1954). Techniques for maintaining drug-resistant cell lines are outlined including; maintaining cells with chemotherapy, pulse treating with chemotherapy, or returning to master drug-resistant stocks. The heterogeneity of drug-resistant models produced from the same parent cell line with the same chemotherapy agent is explored with reference to P-glycoprotein. Heterogeneity in drug-resistant cell lines reflects the heterogeneity that can occur in clinical drug resistance.

Response to microtubule-interacting agents in primary epithelial ovarian cancer cells

Background

Ovarian cancer constitutes nearly 4% of all cancers among women and is the leading cause of death from gynecologic malignancies in the Western world. Standard first line adjuvant chemotherapy treatments include Paclitaxel (Taxol) and platinum-based agents. Taxol, epothilone B (EpoB) and discodermolide belong to a family of anti-neoplastic agents that specifically interferes with microtubules and arrests cells in the G2/M phase of the cell cycle. Despite initial success with chemotherapy treatment, many patients relapse due to chemotherapy resistance. In vitro establishment of primary ovarian cancer cells provides a powerful tool for better understanding the mechanisms of ovarian cancer resistance. We describe the generation and characterization of primary ovarian cancer cells derived from ascites fluids of patients with epithelial ovarian cancer.

Methods

Chemosensitivity of these cell lines to Taxol, EpoB and discodermolide was tested, and cell cycle analysis was compared to that of immortalized ovarian cancer cell lines SKOV3 and Hey. The relationship between drug resistance and αβ-tubulin and p53 status was also investigated.

Results

All newly generated primary cancer cells were highly sensitive to the drugs. αβ-tubulin mutation was not found in any primary cell lines tested. However, one cell line that harbors p53 mutation at residue 72 (Arg to Pro) exhibits altered cell cycle profile in response to all drug treatments. Immortalized ovarian cancer cells respond differently to EpoB treatment when compared to primary ovarian cancer cells, and p53 polymorphism suggests clinical significance in the anti-tumor response in patients.

Conclusions

The isolation and characterization of primary ovarian cancer cells from ovarian cancer patients’ specimens contribute to further understanding the nature of drug resistance to microtubule interacting agents (MIAs) currently used in clinical settings.

Establishment and characterization of a cell line (NOMH-1) originating from a human endometrioid adenocarcinoma of the ovary

Background

Cell lines are very useful for clinical and basic research. Thus far, only 11 reports have documented the characteristics of ovarian endometrioid adenocarcinoma cell lines in the literature. Due to the scarcity of information, the establishment of an ovarian malignant tumor cell line with distinctive characteristics is particularly important to study this disease. Thus, this study was undertaken to establish and characterize a new human endometrioid adenocarcinoma cell line of the ovary.

Methods

The cell line NOMH-1 was established from an ovarian tumor of a 44-year-old woman. Features of the cell line studied included morphology, chromosome analysis, heterotransplantation, tumor markers, and chemosensitivity.

Results

This cell line has been growing well for 232 months and subcultured more than 50 times. Monolayer cultured cells were polygonal in shape, showing a pavement-like arrangement and a tendency to stack without contact inhibition. They exhibited a human karyotype with a modal chromosomal number in the hypertriploid range. The cells could be transplanted into the subcutis of nude mice and produced tumors resembling the original tumor. NOMH-1 cells expressed both CEA and CA19-9 which were identified immunohistochemically in the original tumor and the heterotransplanted tumor. The cells were sensitive to paclitaxel, an agent commonly used in the treatment of gynecological cancers.

Conclusions

NOMH-1 is the first ovarian endometrioid adenocarcinoma cell line in which CEA and CA19-9 expression have been defined. This newly established cell line should be useful for investigating the characteristics of ovarian endometrioid adenocarcinoma.

BRCA1/2 mutation analysis in 41 ovarian cell lines reveals only one functionally deleterious BRCA1 mutation

Mutations in BRCA1/2 increase the risk of developing breast and ovarian cancer. Germline BRCA1/2 mutations occur in 8.6-13.7% of unselected epithelial ovarian cancers, somatic mutations are also frequent. BRCA1/2 mutated or dysfunctional cells may be sensitive to PARP inhibition by synthetic lethality. The aim of this study is to comprehensively characterise the BRCA1/2 status of a large panel of ovarian cancer cell lines available to the research community to assist in biomarker studies of novel drugs and in particular of PARP inhibitors. The BRCA1/2 genes were sequenced in 41 ovarian cell lines, mRNA expression of BRCA1/2 and gene methylation status of BRCA1 was also examined. The cytotoxicity of PARP inhibitors olaparib and veliparib was examined in 20 cell lines. The cell line SNU-251 has a deleterious BRCA1 mutation at 5564G > A, and is the only deleterious BRCA1/2 mutant in the panel. Two cell lines (UPN-251 and PEO1) had deleterious mutations as well as additional reversion mutations that restored the protein functionality. Heterozygous mutations in BRCA1/2 were relatively common, found in 14.6% of cell lines. BRCA1 was methylated in two cell lines (OVCAR8, A1847) and there was a corresponding decrease in gene expression. The BRCA1 methylated cell lines were more sensitive to PARP inhibition than wild-type cells. The SNU-251 deleterious mutant was more sensitive to PARP inhibition, but only in a long-term exposure to correct for its slow growth rate. Cell lines derived from metastatic disease are significantly more resistant to veliparib (2.0 fold p = 0.03) compared to those derived from primary tumours. Resistance to olaparib and veliparib was correlated Pearsons-R 0.5393, p = 0.0311. The incidence of BRCA1/2 deleterious mutations 1/41 cell lines derived from 33 different patients (3.0%) is much lower than the population incidence. The reversion mutations and high frequency of heterozygous mutations suggest that there is a selective pressure against BRCA1/2 in cell culture similar to the selective pressure seen in the clinic after treatment with chemotherapy. PARP inhibitors may be useful in patients with BRCA1 deleterious mutations or gene methylation.

DNA profiling analysis of endometrial and ovarian cell lines reveals misidentification, redundancy and contamination

OBJECTIVES

Cell lines derived from human ovarian and endometrial cancers, and their immortalized non-malignant counterparts, are critical tools to investigate and characterize molecular mechanisms underlying gynecologic tumorigenesis, and facilitate development of novel therapeutics. To determine the extent of misidentification, contamination and redundancy, with evident consequences for the validity of research based upon these models, we undertook a systematic analysis and cataloging of endometrial and ovarian cell lines.

METHODS

Profiling of cell lines by analysis of DNA microsatellite short tandem repeats (STR), p53 nucleotide polymorphisms and microsatellite instability was performed.

RESULTS

Fifty-one ovarian cancer lines were profiled with ten found to be redundant and five (A2008, OV2008, C13, SK-OV-4 and SK-OV-6) identified as cervical cancer cells. Ten endometrial cell lines were analyzed, with RL-92, HEC-1A, HEC-1B, HEC-50, KLE, and AN3CA all exhibiting unique, uncontaminated STR profiles. Multiple variants of Ishikawa and ECC-1 endometrial cancer cell lines were genotyped and analyzed by sequencing of mutations in the p53 gene. The profile of ECC-1 cells did not match the EnCa-101 tumor, from which it was reportedly derived, and all ECC-1 isolates were genotyped as Ishikawa cells, MCF-7 breast cancer cells, or a combination thereof. Two normal, immortalized endometrial epithelial cell lines, HES cells and the hTERT-EEC line, were identified as HeLa cervical carcinoma and MCF-7 breast cancer cells, respectively.

CONCLUSIONS

Results demonstrate significant misidentification, duplication, and loss of integrity of endometrial and ovarian cancer cell lines. Authentication by STR DNA profiling is a simple and economical method to verify and validate studies undertaken with these models.

BRCA1-IRIS overexpression promotes cisplatin resistance in ovarian cancer cells

Evasion of apoptosis plays a key role in cancer development, drug resistance, and recurrence. The BRCA1 locus product protein BRCA1-IRIS is overexpressed in several cisplatin-resistant ovarian cancer cell lines, but its relationship to resistance is uncertain. Here, we show that in human ovarian surface epithelial (HOSE) cells, overexpression of BRCA1-IRIS triggers expression of the antiapoptotic protein survivin. Negative modulation of phosphatidylinositol 3-kinase (PI3K) signaling or AKT silencing reduced survivin expression in this setting. Conversely, silencing BRCA1-IRIS in ovarian cancer cell lines derepressed PTEN expression along with the antiapoptotic AKT targets FOXO1 and FOXO3a, suppressing survivin expression. Cisplatin (≤50 μmol/L) exposure was sufficient to activate expression of the BRCA1-IRIS-AKT-survivin cascade in HOSE cells, whereas under similar conditions cisplatin failed to induce apoptosis in ovarian cancer cell lines expressing this regulatory cascade. Mechanistic investigations indicated that BRCA1-IRIS triggers survivin expression through a PI3K/AKT-dependent pathway involving NF-κB, but also through a PI3K/AKT-independent pathway involving PTEN, FOXO1, and FOXO3a. Our findings indicate how BRCA1-IRIS overexpression prevents chemotherapy-induced cell death by upregulating expression of survivin, and they highlight this regulatory cascade as a candidate focus to improve treatment of advanced drug-resistant ovarian cancers.

Genomic and proteomic characterization of YDOV-157, a newly established human epithelial ovarian cancer cell line

The existence of several model systems with which to investigate a particular disease is advantageous for researchers. This is especially true for ovarian cancer, which, due to its complex and heterogeneous nature, inherently requires a large number of model systems. Here, we report a new ovarian serous adenocarcinoma cell line, designated YDOV-157, and characterized via post genomics and post proteomics. In this study, primary culture of tumor cells from ascites was performed and the cells were immortalized up to at least 60 passages in vitro. We studied the morphologies, cell proliferation, BRCA1/2 mutations, tumorigenesis capacity, and chemosensitivity of YDOV-157. Using a cDNA microarray, differentially expressed genes were identified and some of them were validated. Using proteomic analysis, we identified proteins that were differentially expressed in YDOV-157. The newly derived cell line, designated YDOV-157, grew as a monolayer and the doubling time was 102 h. When transplanted into nude mice, it initiated the formation of tumor masses with microscopic findings identical to those of the primary tumor. Chemosensitivity test showed that paclitaxel induced the highest chemosensitivity index. In microarray analysis, 2,520 probes were differently expressed, compared to human ovarian surface epithelial cells (HOSEs). In SYBR Green real-time PCR, the expression of E2F2 (P = 0.040) and CRABP2 genes (P = 0.030) was significantly higher in the ovarian cancer cell lines than in HOSEs. Furthermore, proteomic analysis showed that expression of 28 spots was significantly altered between YDOV-157 and HOSE. In conclusion, the newly derived YDOV-157 cell line may be an important research resource for studying cancer cell biology and should also be very useful for developing new strategies that inhibit cancer cell growth and progression.

Six1 overexpression in ovarian carcinoma causes resistance to TRAIL-mediated apoptosis and is associated with poor survival

Tumorigenesis can arise from inappropriate activation of developmental genes in mature tissues. Here, we show that the developmental regulator Six1 is overexpressed in ovarian carcinoma cell lines (OCC) compared with normal ovarian surface epithelium. As observed in other cancers, Six1 overexpression in OCC leads to increased A-type cyclin expression and increased proliferation. In addition, Six1 overexpression renders OCC resistant to tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis, and Six1 knockdown in the TRAIL-resistant SKOV3 ovarian carcinoma line dramatically sensitizes the cells to TRAIL. Because inactivation of the TRAIL response has been linked to metastasis, and because antibodies and recombinant ligand that activate the TRAIL pathway are currently in clinical trials against ovarian carcinoma, we screened normal ovarian and carcinoma specimens for Six1 mRNA. Six1 was overexpressed in 50% of the early-stage (stage I) and 63% of the late-stage (stages II, III, and IV) ovarian carcinomas examined, with late-stage carcinomas expressing approximately 3-fold higher Six1 mRNA levels on average compared with early-stage tumors. Importantly, in patients with late-stage disease, high Six1 expression was associated with significantly shortened survival (P = 0.0015). These data suggest that Six1 may contribute to ovarian epithelial carcinogenesis by simultaneously increasing proliferation and decreasing TRAIL-mediated apoptosis and imply that Six1 may be an important determinant of TRAIL therapy response that should be considered in patient selection for TRAIL-related clinical trials.

Functional characterization of a novel BRCA1-null ovarian cancer cell line in response to ionizing radiation

The breast and ovarian cancer susceptibility gene BRCA1 plays a major role in the DNA damage response pathway. The lack of well-characterized human BRCA1-null cell lines has limited the investigation of BRCA1 function, particularly with regard to its role in ovarian cancer. We propagated a novel BRCA1-null human ovarian cancer cell line UWB1.289 from a tumor of papillary serous histology, the most common form of ovarian carcinoma. UWB1.289 carries a germline BRCA1 mutation within exon 11 and has a deletion of the wild-type allele. UWB1.289 is estrogen and progesterone receptor negative and has an acquired somatic mutation in p53, similar to the commonly used BRCA1-null breast cancer cell line HCC1937. We used ionizing radiation to induce DNA damage in both UWB1.289 and in a stable UWB1.289 line in which wild-type BRCA1 was restored. We examined several responses to DNA damage in these cell lines, including sensitivity to radiation, cell cycle checkpoint function, and changes in gene expression using microarray analysis. We observed that UWB1.289 is sensitive to ionizing radiation and lacks cell cycle checkpoint functions that are a normal part of the DNA damage response. Restoration of wild-type BRCA1 function in these cells partially restores DNA damage responses. Expression array analysis not only supports this partial functional correction but also reveals interesting new information regarding BRCA1-positive regulation of the expression of claudin 6 and other metastasis-associated genes and negative regulation of multiple IFN-inducible genes.

BRCA1-IRIS activates cyclin D1 expression in breast cancer cells by downregulating the JNK phosphatase DUSP3/VHR

Cyclin D1 plays an important role in cell cycle progression. In breast cancer, Cyclin D1 expression is deregulated by several mechanisms. We previously showed that in breast cancer cells, overexpression of BRCA1-IRIS induces Cyclin D1 overexpression and increases cell proliferation. BRCA1-IRIS alone or in complex with steroid receptor co-activators was targeted to the cyclin D1 promoter pre-bound by the c-Jun/AP1 and activated its transcription, which could explain the co-overexpression of BRCA1-IRIS and Cyclin D1 in breast cancer cells coupled with their increased proliferation. We report here an alternate or a complementary pathway by which BRCA1-IRIS activates Cyclin D1 expression. BRCA1-IRIS overexpression decreases the expression of the dual specificity phosphatase, DUSP3/VHR, an endogenous inhibitor of several MAPKs, including c-Jun N-terminal kinase. Although, the mechanism by which BRCA1-IRIS overexpression accomplishes that is not yet known, it is sufficient to induce Cyclin D1 overexpression in a human mammary epithelial cell model. Cyclin D1 overexpression could be blocked by co-overexpression of VHR in those cells. Furthermore, in 2 breast cancer cell lines that overexpress both BRCA1-IRIS and Cyclin D1 (MCF-7 and SKBR3) depletion of BRCA1-IRIS by RNA interference attenuated the expression of Cyclin D1 by elevating the expression level of VHR. These data demonstrate a critical role for BRCA1-IRIS in human breast cancer cell-cycle control and suggest that deregulated expression of BRCA1-IRIS is likely to reduce dependence on normal physiological growth stimuli, thereby providing a growth advantage to tumor cells and a potential mechanism of resistance to endocrine therapy.

BRCA1-IRIS regulates cyclin D1 expression in breast cancer cells

The regulator of cell cycle progression, cyclin D1, is up-regulated in breast cancer cells; its expression is, in part, dependent on ERalpha signaling. However, many ERalpha-negative tumors and tumor cell lines (e.g., SKBR3) also show over-expression of cyclin D1. This suggests that, in addition to ERalpha signaling, cyclin D1 expression is under the control of other signaling pathways; these pathways may even be over-expressed in the ERalpha-negative cells. We previously noticed that both ERalpha-positive and -negative cell lines over-express BRCA1-IRIS mRNA and protein. Furthermore, the level of over-expression of BRCA1-IRIS in ERalpha-negative cell lines even exceeded its over-expression level in ERalpha-positive cell lines. In this study, we show that: (1) BRCA1-IRIS forms complex with two of the nuclear receptor co-activators, namely, SRC1 and SRC3 (AIB1) in an ERalpha-independent manner. (2) BRCA1-IRIS alone, or in connection with co-activators, is recruited to the cyclin D1 promoter through its binding to c-Jun/AP1 complex; this binding activates the cyclin D1 expression. (3) Over-expression of BRCA1-IRIS in breast cells over-activates JNK/c-Jun; this leads to the induction of cyclin D1 expression and cellular proliferation. (4) BRCA1-IRIS activation of JNK/c-Jun/AP1 appears to account for this, because in cells that were depleted from BRCA1-IRIS, JNK remained inactive. However, depletion of SRC1 or SRC3 instead reduced c-Jun expression. Our data suggest that this novel signaling pathway links BRCA1-IRIS to cellular proliferation through c-Jun/AP1 nuclear pathway; finally, this culminates in the increased expression of the cyclin D1 gene.

Establishment and characterization of xenografts and cancer cell cultures derived from BRCA1 -/- epithelial ovarian cancers

The BRCA1 gene is responsible for a high number of hereditary breast and ovarian cancers that cluster in families with a strong genetic predisposition. Despite intense investigation, the accumulating findings on BRCA1 biological functions have not yet been translated into specific therapeutic approaches, also due to the lack of suitable experimental models. The purpose of this study was to establish and characterize cell cultures and xenografts from patients with BRCA1 -/- ovarian cancers. We derived two ovarian cancer cell lines, termed PD-OVCA1 and PD-OVCA2, both from patients previously treated with chemotherapy, that propagate in SCID mice as well as in vitro for a limited number of passages. Both cell lines expressed cytokeratins and the CA125 tumour marker. A detailed molecular characterization highlighted both constitutive and somatic genetic events that abrogate BRCA1 gene function. Both cell lines were shown to lose the wild type BRCA1 allele; intriguingly, these deletions were apparently accompanied by gain of one or more copies of the mutant alleles. Finally, a genomic profile of major chromosomal aberrations was obtained by the Multiplex Ligation-dependent Probe Amplification (MLPA) technique, which disclosed chromosomal imbalances targeting specific genes in each cell line. The PD-OVCA1 and PD-OVCA2 ovarian cancer cell lines will provide a valuable tool for new experimental models for the study of BRCA1-associated tumour biology.

Human epididymis protein 4 (HE4) is a secreted glycoprotein that is overexpressed by serous and endometrioid ovarian carcinomas

Among the genes most commonly identified in gene expression profiles of epithelial ovarian carcinomas (EOC) is the gene for human epididymis protein 4 (HE4). To ascertain its clinical utility, we did a comprehensive assessment of HE4 protein expression in benign and malignant ovarian and nonovarian tissues by immunohistochemistry. In comparison with normal surface epithelium, which does not express HE4, we found that cortical inclusion cysts lined by metaplastic Mullerian epithelium abundantly express the protein. Its expression in tumors was restricted to certain histologic subtype: 93% of serous and 100% of endometrioid EOCs expressed HE4, whereas only 50% and 0% of clear cell carcinomas and mucinous tumors, respectively, were positive. Tissue microarrays revealed that the majority of nonovarian carcinomas do not express HE4, consistent with our observation that HE4 protein expression is highly restricted in normal tissue to the reproductive tracts and respiratory epithelium. HE4 is predicted to encode a secreted protein. Using reverse transcription-PCR, we identified ovarian cancer cell lines that endogenously overexpress HE4. Cultured medium from these cells revealed a secreted form of HE4 that is N-glycosylated. This observation is consistent with the recent report that HE4 circulates in the bloodstream of patients with EOC. Therefore, HE4 is a secreted glycoprotein that is overexpressed by serous and endometrioid EOCs. Its expression in cortical inclusion cysts suggests that formation of Mullerian epithelium is a prerequisite step in the development of some types of EOCs.

Biology of SNU cell lines

SNU (Seoul National University) cell lines have been established from Korean cancer patients since 1982. Of these 109 cell lines have been characterized and reported, i.e., 17 colorectal carcinoma, 12 hepatocellular carcinoma, 11 gastric carcinoma, 12 uterine cervical carcinoma, 17 B-lymphoblastoid cell lines derived from cancer patients, 5 ovarian carcinoma, 3 malignant mixed Mllerian tumor, 6 laryngeal squamous cell carcinoma, 7 renal cell carcinoma, 9 brain tumor, 6 biliary tract, and 4 pancreatic carcinoma cell lines. These SNU cell lines have been distributed to biomedical researchers domestic and worldwide through the KCLB (Korean Cell Line Bank), and have proven to be of value in various scientific research fields. The characteristics of these cell lines have been reported in over 180 international journals by our laboratory and by many other researchers from 1987. In this paper, the cellular and molecular characteristics of SNU human cancer cell lines are summarized according to their genetic and epigenetic alterations and functional analysis.

An adenoviral vector containing an arg-gly-asp (RGD) motif in the fiber knob enhances protein product levels from transgenes refractory to expression

Genetic manipulation of the adenovirus type 5 represents one strategy to modify viral transduction properties in vitro and in vivo. In the majority of studies to date, reporter gene activity has been monitored to assess transduction efficiency. BRCA1 is a gene whose protein product is clinically important, biologically toxic, difficult to overexpress, and difficult to detect as an untagged protein species. Thus, it represents an attractive candidate from which to evaluate the efficacy of a gene delivery system. In the present study, transgene expression was assessed employing otherwise isogenic viruses, which differed only in the presence or absence of an RGD integrin-binding motif in the HI loop of the Ad fiber knob. We utilized a combination of BRCA1 expression level comparisons among several human BRCA1/mutant BRCA1/murine Brca1 constructs and reporter gene activity following transduction of a panel of human breast and ovarian tumor cell lines representative of both sporadic and hereditary cases. A general overall concordance in efficiency was observed, whether the biological readout measured was reporter gene activity or steady-state level of ectopic BRCA1 protein produced. Importantly, the expression of full-length wild-type BRCA1 protein, clinically relevant mutant BRCA1 proteins or murine Brca1 was superior when the gene was delivered via the RGD-modified Ad. The ectopic BRCA1 stabilized endogenous BARD1 and this functional effect was evident at lower input viral doses when BRCA1 was delivered via the RGD-modified Ad. Quantitative, noninvasive, real-time image analysis of reporter gene function in nude mice harboring human ovarian tumor xenographs demonstrated a similar enhancement of expression in vivo by the RGD fiber modification, with low levels of transduction of normal mouse mesothelium. These results provide additional evidence supporting the concept that rational modification of viral vectors can result in the delivery of functionally active therapeutic proteins such as BRCA1 that present with technical difficulties with regard to their expression.

Role of BRCA1 in cellular resistance to paclitaxel and ionizing radiation in an ovarian cancer cell line carrying a defective BRCA1

BRCA1, the gene responsible for approximately half of all cases of hereditary breast cancer and almost all cases of combined hereditary breast and ovarian cancer, has been implicated in the maintenance of genomic stability through DNA repair. This function is mediated, at least in part, through two tandem BRCA1 C-terminal (BRCT) repeats. The role of BRCA1 in the development of ovarian cancer is poorly understood, partially owing to the lack of ovarian cancer cell lines with defective BRCA1. The purpose of this study was to further characterize an endometrioid ovarian cancer cell line, SNU-251, which was previously reported to carry a nonsense mutation (from G to A) at amino acid 1815 of BRCA1. In addition, we examined the role of BRCA1 in the cell cycle and in the responses to the chemotherapy drug paclitaxel and ionizing radiation. Loss of the C-terminal 49 amino acids due to this point mutation did not affect the expression of the truncated BRCA1 protein, but caused a loss of transcriptional activation of the endogenous p21(WAF1/CIP1) gene, and could not sustain arrest in the G(2)/M phase of the cell cycle. The BRCA1 mutation in SNU-251 cells inhibited BRCA1 subnuclear assembly for DNA-damage repair and increased cellular sensitivity to ionizing radiation and paclitaxel. This sensitivity was reversed by reintroduction of ectopic wild-type BRCA1. Our results suggest that the deletion of the C-terminal 49 amino acids of BRCA1 results in a loss of BRCA1 function in the SNU-251 cell line. BRCA1 helps to mediate the resistance to both radiation and paclitaxel. Therefore, SNU-251 may be a useful model for studying the molecular mechanism of BRCA1 in the resistance of ovarian cancer to ionizing radiation and chemotherapy treatment and in the development of hereditary human ovarian cancer.

Inhibition of human telomerase reverse transcriptase gene expression by BRCA1 in human ovarian cancer cells

Human telomerase reverse transcriptase (hTERT), the catalytic subunit of human telomerase, is responsible for the synthesis and maintenance of the telomeric repeats at the distal ends of human chromosomes. Telomerase expression is repressed in normal human cells and is activated in immortal cells and during tumorigenesis, but the mechanism by which telomerase expression is regulated is not fully understood. Previous studies have shown that c-Myc stimulates hTERT transcription through the binding sites located on the hTERT promoter. In this study, we sought to determine whether BRCA1 inhibits hTERT transcription through its direct interaction with c-Myc. In ovarian cancer cells, c-Myc increased hTERT expression by threefold and BRCA1 completely abrogated this activity. A mutation in the c-Myc-binding site (E-box) of the hTERT promoter resulted in the loss of activation by c-Myc and in the loss of inhibition by BRCA1. Deletion of the c-Myc-binding domain in BRCA1 resulted in the loss of BRCA1's ability to inhibit transcription of the hTERT promoter. In addition, BRCA1 associates with c-Myc and inhibits the binding activity of c-Myc to the hTERT promoter. Our data indicate that BRCA1 is involved in regulating cellular immortalization through the modulation of c-Myc on the hTERT promoter.

Chromosomal aberrations in ovarian malignant brenner tumor cell line using chromosome painting

Cytogenetic changes in an ovarian malignant Brenner tumor cell line, SNU-840, were investigated by chromosome painting and G-banding. All chromosome alterations were confirmed by the use of multiple chromosome paintings, which also demonstrated a number of additional alterations.

Establishment and characterization of a breast cell strain containing a BRCA1 185delAG mutation

OBJECTIVE

The aim of this study was to examine whether cells containing the heterozygous form of a BRCA1 185delAG mutation would exhibit abnormal growth or an altered response to DNA damage.

METHODS

A primary culture of human mammary epithelial cells (90P) was obtained from the nontumor breast tissue of a 35-year-old patient who had undergone a mastectomy for removal of a breast tumor. These cells were immortalized (90PE6E7) following retroviral infection with HPV-16 viral E6/E7. genes. Both the 90P cell strain and the cell line were characterized for their ability to grow in culture, form colonies in soft agar, and produce tumors in athymic nude mice compared to normal breast epithelial cells containing wild-type BRCA1. 90P cells were also analyzed for cellular response to gamma radiation and H(2)O(2).

RESULTS

These cells were confirmed to contain a frameshift mutation, 185delAG, of the BRCA1 gene. Despite being heterozygous for wild-type BRCA1, the 220-kDa full-size BRCA1 protein was abundantly expressed. 90P and 90PE6E7 cells grew at a similar rate and were anchorage dependent. 90PE6E7 also failed to form tumors in athymic nude mice. Finally, 90P cells exhibited a survival response similar to that of normal mammary epithelial cells to radiation damage and exposure to oxidative stress.

CONCLUSION

To our knowledge the 90P cells and the 90PE6E7 cells are the first characterized, non-tumor-derived breast epithelial cells that are heterozygous for the BRCA1 germline mutation 185delAG. Our conclusion is that these BRCA1 mutant cells appear to have growth and stress response characteristics similar to those of normal human breast cells, which is consistent with the hypothesis that loss of heterozygosity must occur to impair putative BRCA1 function.

Epithelial ovarian cancer, infertility and induction of ovulation: possible pathogenesis and updated concepts

Numerous case-control, cohort studies, case reports and reviews have been published during the last 5 years regarding the association between infertility and induction of ovulation and epithelial ovarian cancer. Despite this amount of published material, final conclusions regarding direct linkage between these different aspects of infertility and ovarian cancer, as well as any data relating to a putative pathogenetic mechanism, cannot be drawn. In this review we summarize the available data as well as update a previous review by Shoham published in 1994. We outline some of the information that has become available from basic research which may help to direct investigators to suitable clinical research models that may eventually serve to clarify this enigma. Finally we share ideas that focus on specific high-risk cohorts.