Biomedical subjects

Ie-Ming Shih

Publications and source records attributed to Ie-Ming Shih.

At least 37 records · Page 2Linked to original sources

PubMed2005

Molecular pathogenesis of ovarian borderline tumors: new insights and old challenges.

Ovarian borderline (low malignant potential) tumors are a puzzling group of neoplasms that do not fall neatly into benign or malignant categories. Their behavior is enigmatic, their pathogenesis unclear, and their clinical management controversial, especially for serous borderline tumors (SBT), the most common type of ovarian borderline tumor. Clarifying the nature of borderline tumors and their relationship to invasive carcinoma has puzzled investigators since the category was created over 30 years ago. Much of the confusion and controversy concerning these tumors is due to a lack of understanding of their pathogenesis and an absence of a model for the development of ovarian carcinoma. This review summarizes recent molecular studies of ovarian borderline tumors with special emphasis on the role of SBT in tumor progression and its relationship to ovarian serous carcinoma.

Cystadenoma, Serous↗

PubMed2005

Amplification of a chromatin remodeling gene, Rsf-1/HBXAP, in ovarian carcinoma.

A genomewide technology, digital karyotyping, was used to identify subchromosomal alterations in ovarian cancer. Amplification at 11q13.5 was found in three of seven ovarian carcinomas, and amplicon mapping delineated a 1.8-Mb core of amplification that contained 13 genes. FISH analysis demonstrated amplification of this region in 13.2% of high-grade ovarian carcinomas but not in any of low-grade carcinomas or benign ovarian tumors. Combined genetic and transcriptome analyses showed that Rsf-1 (HBXAPalpha) was the only gene that demonstrated consistent overexpression in all of the tumors harboring the 11q13.5 amplification. Patients with Rsf-1 amplification or overexpression had a significantly shorter overall survival than those without. Overexpression of Rsf-1 gene stimulated cell proliferation and transform nonneoplastic cells by conferring serum-independent and anchorage-independent growth. Furthermore, Rsf-1 gene knockdown inhibited cell growth in OVCAR3 cells, which harbor Rsf-1 amplification. Taken together, these findings indicate an important role of Rsf-1 amplification in ovarian cancer.

Carcinoma↗

PubMed2005

Nuclear size distinguishes low- from high-grade ovarian serous carcinoma and predicts outcome.

A dualistic model for ovarian serous carcinogenesis based on morphological and molecular genetic studies has recently been proposed. This model divides serous carcinoma into low- and high-grade tumors, which develop along distinct molecular pathways. In this report, we evaluated computerized morphometry to determine its utility in distinguishing low- and high-grade serous carcinoma. The mean nuclear area (MNA) and the volume percentage of epithelium (VPE) in 93 high-grade serous carcinomas was measured and compared with 16 low-grade serous carcinomas and 21 serous borderline tumors, the putative precursor of low-grade serous carcinoma. We found that both MNA and VPE were significantly higher in high-grade serous carcinoma compared with low-grade serous carcinoma and serous borderline tumors (P < .001 and P = .02, respectively). There was no significant difference in MNA and VPE between low-grade carcinoma and serous borderline tumors (P > .3). Among high-grade serous carcinomas, those with an MNA of 46 microm2 or higher had a poorer survival (P = .035) than those with an MNA below 46 microm2. In contrast, VPE and tumor grade (moderately versus poorly differentiated) had no significant prognostic value. The morphometry findings lend further support to the dualistic model of ovarian serous carcinogenesis and suggest that MNA is an excellent adjunctive tool for distinguishing low- from high-grade serous carcinomas. In addition, MNA is an independent prognostic factor for high-grade serous carcinoma.

Cell Nucleus↗

PubMed2005

Identification and characterization of membralin, a novel tumor-associated gene, in ovarian carcinoma.

Identification of new genes in cancer is the key to understand the molecular basis of tumor development as well as provide potential diagnostic markers and therapeutic targets. A novel gene, membralin (GeneBank accession number: DQ005958), was cloned from a human ovarian cancer cell line. Human membralin is unique and does not share significant sequence homology with other human genes, only membralins of other species. The gene contains 11 exons which encode at least two spliced variants in human cancer. The long form of membralin (membralin-1) comprises all 11 exons, encoding a protein of 620-amino acids long and the short form of membralin (membralin-3) contains all exons except for exon 10, encoding a protein of 408 amino acids. Expression of different membralin isoforms depends on tissue type. The long form, membralin-1, is expressed in ovarian and colorectal carcinomas but not in breast or pancreatic carcinomas, which express only the short splice form, membralin-3. Membralin-1-GFP fusion protein demonstrates exclusive cytoplasmic localization. Based on quantitative real-time PCR, in situ hybridization and Western blot analysis, membralin was highly expressed in ovarian serous carcinomas as compared to ovarian surface epithelium (P<0.001). Ovarian carcinomas in effusions demonstrated a significantly higher level of membralin expression than in solid tumors (P<0.001). In conclusion, these findings represent the first characterization of human membralin and suggest that membralin is a novel tumor-associated marker in ovarian serous carcinomas.

Amino Acid Sequence↗

PubMed2005

Inactivation of the mitogen-activated protein kinase pathway as a potential target-based therapy in ovarian serous tumors with KRAS or BRAF mutations.

Activation of mitogen-activated protein kinase (MAPK) occurs in response to various growth stimulating signals and as a result of activating mutations of the upstream regulators, KRAS and BRAF, which can be found in many types of human cancer. To investigate the roles of MAPK activation in tumors harboring KRAS or BRAF mutations, we inactivated MAPK in ovarian tumor cells using CI-1040, a compound that selectively inhibits MAPK kinase, an upstream regulator of MAPK and thus prevents MAPK activation. Profound growth inhibition and apoptosis were observed in CI-1040-treated tumor cells with mutations in either KRAS or BRAF in comparison with the ovarian cancer cells containing wild-type sequences. Long serial analysis of gene expression identified several differentially expressed genes in CI-1040-treated MPSC1 cells harboring an activating mutation in BRAF (V599L). The most striking changes were down-regulation of cyclin D1, COBRA1, and transglutaminase-2 and up-regulation of tumor necrosis factor-related apoptosis-induced ligand, thrombospondin-1, optineurin, and palladin. These patterns of gene expression were validated in other CI-1040-treated tumor cells based on quantitative PCR. Constitutive expression of cyclin D1 partially reversed the growth inhibitory effect of CI-1040 in MPSC1 cells. Our findings indicate that an activated MAPK pathway is critical in tumor growth and survival of ovarian tumors with KRAS or BRAF mutations and suggest that the CI-1040 induced phenotypes depend on the mutational status of KRAS and BRAF in ovarian tumors.

Apoptosis↗

PubMed2005

Apolipoprotein E is required for cell proliferation and survival in ovarian cancer.

Apolipoprotein E (ApoE) has been recently identified as a potential tumor-associated marker in ovarian cancer by serial analysis of gene expression. ApoE has long been known to play a key role in lipid transport, and its specific isoforms may participate in atherosclerogenesis. However, its role in human cancer is not known. In this study, apoE expression was frequently detected in ovarian serous carcinomas, the most common and lethal type of ovarian cancer. It was not detected in serous borderline tumors and normal ovarian surface epithelium. Inhibition of apoE expression using an apoE-specific siRNA led to G(2) cell cycle arrest and apoptosis in an apoE-expressing ovarian cancer cell line, OVCAR3, but not in apoE-negative cell lines. Furthermore, the phenotype of apoE siRNA-treated OVCAR3 cells was reversed by expressing engineered mutant apoE with introduced silent mutations in the siRNA target sequence. Expression of apoE in nuclei was significantly associated with a better survival in patients who presented peritoneal effusion at the time of diagnosis (5-year follow-up, P = 0.004). This study suggests a new role of apoE in cancer as apoE expression is important for the proliferation and survival in apoE-expressing ovarian cancer cells.

Apolipoproteins E↗

PubMed2005

Differential expression of L-selectin ligand in the endometrium during the menstrual cycle.

OBJECTIVE: To evaluate the expression of L-selectin ligand in the endometrium during the menstrual cycle. DESIGN: Retrospective study. SETTING: University teaching hospital. PATIENT(S): Endometrial samples from regularly cycling women. INTERVENTION(S): Tissue microarray and immunohistochemical staining were performed using L-selectin ligand monoclonal antibody (MECA-79). MAIN OUTCOME MEASURE(S): Expression of L-selectin ligand in the various phases of menstrual cycle was measured by a semiquantitative analysis (HSCORE) for the intensity of immunohistochemical reactivity. RESULT(S): In the luminal epithelium, there were significant differences in L-selectin ligand expression during the proliferative, interval, early secretory, and midsecretory phases. The expression of L-selectin ligand was greatest from the periovulatory interval through midsecretory phase. In the glandular epithelium, the expression of L-selectin ligand was greatest in midsecretory phase with significant differences between proliferative phase and the midsecretory phase and between the interval phase and the midsecretory phase. CONCLUSION(S): Increased expression of L-selectin ligand in the human endometrium during the early and midsecretory phases of the menstrual cycle may be related to the process of implantation.

Adult↗

PubMed2005

HLA-G expression in effusions is a possible marker of tumor susceptibility to chemotherapy in ovarian carcinoma.

OBJECTIVE: We recently showed that the levels of secreted human leukocyte antigen-G (HLA-G), a nonclassical MHC class I antigen, are significantly elevated in malignant effusions in ovarian carcinoma compared to benign ones. The objective of this study was to evaluate the expression and clinical role of HLA-G in effusions and corresponding solid tumors from patients diagnosed with advanced-stage ovarian carcinoma. METHODS: Effusions (= 148), corresponding primary tumors (= 66), and metastatic lesions (= 122) were analyzed using immunohistochemistry with an anti-HLA-G monoclonal antibody. RESULTS: HLA-G was detected in cancer cells in 49/148 (33%) effusions, 33/66 (50%) primary tumors, and 59/122 (48%) solid metastases. These differences did not reach statistical significance. Expression in effusions and solid metastases significantly correlated (P = 0.029). HLA-G expression in tumor cells was significantly lower in effusions obtained during or following chemotherapy (P = 0.038). The presence of HLA-G-positive tumor cells in effusions obtained prior to the institution of chemotherapy correlated with better overall survival (P = 0.042). HLA-G expression in primary tumors and solid metastases did not correlate with any of the clinicopathologic parameters studied. CONCLUSIONS: HLA-G is expressed in a significant number of ovarian carcinomas at all anatomic sites. The reduced expression of HLA-G in post-chemotherapy effusions and its correlation with improved survival may be related to preferential susceptibility of HLA-G-expressing cells at this site. Our findings suggest a new role for HLA-G as a prognostic indicator in advanced-stage ovarian cancer in effusions.

Adult↗

PubMed2005

Activation of mitogen-activated protein kinase is required for migration and invasion of placental site trophoblastic tumor.

Placental site trophoblastic tumor (PSTT) is a gestational neoplasm derived from the extravillous (intermediate) trophoblast of the implantation site. PSTT is characterized by a highly invasive phenotype, but the molecular mechanisms are poorly understood. In this report, we demonstrate that PSTTs expressed the activated (phosphorylated) form of mitogen-activated protein kinase (MAPK) in 84% of cases, whereas the normal extravillous trophoblastic cells did not. To characterize the role of MAPK activation in PSTT, we established the first PSTT cell culture, IST-2, from a surgically resected PSTT. IST-2 cells expressed HLA-G and Mel-CAM but not E-cadherin, an immunophenotype characteristic of PSTT. IST-2 cells were highly motile and invasive in culture as compared to choriocarcinoma JEG-3 cells and normal extravillous trophoblastic cells. Based on wound assay, time-lapse videomicroscopy for cell tracking, and invasion chamber assays, we found that the motility and invasion of IST-2 cells were significantly reduced (P<0.01) after treatment with the MEK inhibitors CI-1040 and PD 59089, which prevent activation of MAPK. In contrast, neither compound had any effect on normal extravillous trophoblastic cells or JEG-3 cells. In conclusion, our findings demonstrate a functional role of MAPK activation in the motility and invasion of PSTT.

Benzamides↗

PubMed2005

Apply innovative technologies to explore cancer genome.

PURPOSE OF REVIEW: Molecular genetic alterations characterize the development of human cancer. Recent advances in molecular genetic technology and the success of the human genome project have empowered investigators with new tools in dissecting the cancer genome for discovery of new cancer-associated genes. The purpose of this review is to highlight the emerging molecular genetic methodologies and summarize their principles, applications, and potential technical challenges. The critical issue in sample preparation and a strategy that combines different molecular techniques to facilitate the identification of novel cancer-associated genes will be discussed. RECENT FINDINGS: Digital karyotyping and array-based techniques including array comparative genomic hybridization and representational oligonucleotide microarray analysis have been recently developed to study the genomic landscape in human cancer. These innovations provide tools to quantitatively measure DNA copy number changes in cancer and to map those changes directly onto the human genome. Digital karyotyping is based on counting the sequence tags that are distributed in the human genome and thus, it provides a digital readout to precisely outline the amplified and deleted chromosomal regions. Array-based technologies, on the other hand, compare the content of cancer and reference genomes followed by localizing the amplified or deleted signals in chromosomal regions using an array hybridization technique. In addition, a high-throughput mutational analysis platform has been available for a large-scale mutational analysis by using an automated capillary sequencing device and sophisticated bioinformatic tools. A number of examples have demonstrated the promise of these new molecular genetic approaches in identifying several potential new oncogenes and tumor suppressors. SUMMARY: As compared with conventional cytogenetics methods, digital karyotyping, array comparative genomic hybridization, and representational oligonucleotide microarray analysis provide an unprecedented mapping resolution that allows a precise localization of the amplified and deleted chromosomal regions. These technologies can be combined with gene expression profiling and high-throughput mutational analysis to facilitate the search for new cancer-associated genes. It is expected that applying these new technologies will lead to discovery of a host of novel oncogenes and tumor suppressors, which will have a significant impact in our understanding of tumorigenesis and in the clinical management of cancer patients.

Cytogenetics↗

PubMed2005

Patterns of p53 mutations separate ovarian serous borderline tumors and low- and high-grade carcinomas and provide support for a new model of ovarian carcinogenesis: a mutational analysis with immunohistochemical correlation.

The infrequent association of serous borderline tumors (SBTs) with invasive serous carcinoma has led to the view that SBTs are unrelated to invasive serous carcinoma. Nonetheless, mortality associated with SBTs is generally attributed to malignant transformation, and traditionally these tumors have been designated as "carcinomas of low malignant potential." Previous immunohistochemical studies evaluating p53 expression and molecular genetic studies evaluating mutational status have reported that p53 overexpression and mutations are infrequent in SBTs and occur in as many as 50% to 80% of invasive serous carcinomas. The different methodologies for determining p53 status and the failure to correlate the findings with tumor grade make these studies difficult to interpret. The current study was undertaken to overcome these deficiencies and to reconcile the relationship of SBTs to invasive serous carcinoma by performing a morphologic, immunohistochemical, and molecular genetic analysis comparing SBTs with low- and high-grade serous carcinoma. The molecular genetic analysis used a highly stringent, carefully designed nucleotide-sequencing method. A total of 96 sporadic serous tumors including 25 SBTs (11 atypical proliferative serous tumors and 14 intraepithelial low-grade serous carcinomas [noninvasive micropapillary serous carcinomas, MPSCs]), 12 low-grade serous carcinomas (invasive MPSCs), and 59 high-grade serous carcinomas were analyzed for their p53 mutational status of exons 5 to 9. Functional mutations, defined as mutations resulting in the alteration of the structure of the encoded protein, were detected in 30 of 59 (50.8%) high-grade serous carcinomas and 1 (8.3%) of 12 low-grade invasive serous carcinomas compared with 2 (8%) of 25 SBTs, both of these in intraepithelial low-grade serous carcinomas (noninvasive MPSCs). The similar frequency of p53 mutations in SBTs and low-grade invasive serous carcinomas in contrast to the significantly higher frequency of p53 mutations in high-grade serous carcinomas (P < 0.0005) suggests a common lineage for SBTs and low-grade invasive serous carcinomas and supports the view that SBTs are unrelated to the usual type of invasive serous carcinoma, which is a high-grade neoplasm. Mutational status was also correlated with p53 immunoreactivity. Although p53 immunoreactivity is generally higher in those specimens containing mutant p53, immunostaining is neither sufficiently specific nor sensitive enough to predict p53 mutations. The molecular genetic findings confirm our hypothesis of dual pathways of serous carcinogenesis based on previous analyses of KRAS and BRAF mutations on the same set of cases in which KRAS and BRAF mutations were found in 60% of SBTs and low-grade serous carcinoma but not in high-grade serous carcinomas. Based on these studies, we have proposed a model of serous carcinogenesis in which SBTs are the precursors of low-grade serous carcinomas whereas the usual type of invasive serous carcinoma is a high-grade neoplasm that develops "de novo" from in situ alterations in epithelial inclusion cysts.

Base Sequence↗

PubMed2005

Digital single-nucleotide polymorphism analysis for allelic imbalance.

Digital single-nucleotide polymorphism (SNP) analysis is developed to amplify a single template from a pool of DNA samples, thereby generating the amplicons that are homogeneous in sequence. Different fluorophores are then applied as probes to detect and discriminate different alleles (paternal vs maternal alleles or wild-type vs mutant), which can be readily counted. In this way, digital SNP analysis transforms the exponential and analog signals from conventional polymerase chain reaction (PCR) to linear and digital ones. Digital SNP analysis has the following advantages. First, statistical analysis of the PCR products becomes available as the alleles can be directly counted. Second, this technology is designed to generate PCR products of the same size; therefore, DNA degradation would not be a problem as it commonly occurs when microsatellite markers are used to assess allelic status in clinical samples. Last, digital SNP analysis is designed to amplify a relatively small amount of DNA samples, which is available in some clinical samples. Digital SNP analysis has been applied in quantification of mutant alleles and detection of allelic imbalance in clinical specimens and it represents another example of the power of PCR and provides unprecedented opportunities for molecular genetic analysis.

Allelic Imbalance↗

PubMed2004

Mutations of BRAF and KRAS precede the development of ovarian serous borderline tumors.

Molecular genetic changes that are associated with the initiating stage of tumor development are important in tumorigenesis. Ovarian serous borderline tumors (SBTs), putative precursors of low-grade serous carcinomas, are among the few human neoplasms with a high frequency of activating mutations in BRAF and KRAS genes. However, it remains unclear as to how these mutations contribute to tumor progression. To address this issue, we compared the mutational status of BRAF and KRAS in both SBTs and the adjacent epithelium from cystadenomas, the presumed precursor of SBTs. We found that three of eight SBTs contained mutant BRAF, and four SBTs contained mutant KRAS. All specimens with mutant BRAF harbored wild-type KRAS and vice versa. Thus, seven (88%) of eight SBTs contained either BRAF or KRAS mutations. The same mutations detected in SBTs were also identified in the cystadenoma epithelium adjacent to the SBTs in six (86%) of seven informative cases. As compared to SBTs, the cystadenoma epithelium, like ovarian surface epithelium, lacks cytological atypia. Our findings provide cogent evidence that mutations of BRAF and KRAS occur in the epithelium of cystadenomas adjacent to SBTs and strongly suggest that they are very early events in tumorigenesis, preceding the development of SBT.

Cystadenoma, Serous↗

PubMed2004

Characterization of active mitogen-activated protein kinase in ovarian serous carcinomas.

PURPOSE: Mitogen-activated protein kinase (MAPK) plays a pivotal role in signal transduction. Activation of MAPK is regulated by upstream kinases including KRAS and BRAF, which are frequently mutated in low-grade ovarian serous carcinoma. This study evaluates the expression of active MAPK in ovarian serous carcinomas, with response to treatment and survival. EXPERIMENTAL DESIGN: Expression of active MAPK was assessed by immunohistochemistry in 207 cases of ovarian serous tumors. Immunoreactivity was correlated with tumor grade, mutational status of KRAS and BRAF, in vitro drug resistance, and clinical outcome. RESULT: There was a lower frequency of expression of active MAPK in high-grade ovarian serous carcinomas as compared with low-grade serous tumors, including borderline tumors and low-grade serous carcinoma (P < 0.001). Active MAPK was present in all of the 19 low-grade tumors with either KRAS or BRAF mutations as well as in 14 (41%) of 34 tumors with wild-type KRAS and BRAF in both low- and high-grade carcinomas. Expression of active MAPK alone served as a good survival indicator in the 2-year follow-up (P = 0.037) but not in the 5-year follow-up (P = 0.145). However, a combination of expression of active MAPK and in vitro sensitivity of paclitaxel significantly correlated with a better prognosis in 5-year survival rate (P = 0.048) in patients with advanced-stage high-grade serous carcinoma. CONCLUSIONS: Active MAPK is more frequently expressed in low-grade than in high-grade ovarian serous carcinoma. Active MAPK serves as a good prognostic marker in patients with high-grade serous carcinomas.

Adult↗

PubMed2004

Digital karyotyping identifies thymidylate synthase amplification as a mechanism of resistance to 5-fluorouracil in metastatic colorectal cancer patients.

Resistance to chemotherapy is a major cause of mortality in advanced cancer patients. In this study, digital karyotyping was used to search for genomic alterations in liver metastases that were clinically resistant to 5-fluorouracil (5-FU). In two of four patients, we identified amplification of an approximately 100-kb region on 18p11.32 that was of particular interest because it contained the gene encoding thymidylate synthase (TYMS), a molecular target of 5-FU. Analysis of TYMS by fluorescence in situ hybridization identified TYMS gene amplification in 23% of 31 5-FU-treated cancers, whereas no amplification was observed in metastases of patients that had not been treated with 5-FU. Patients with metastases containing TYMS amplification had a substantially shorter median survival (329 days) than those without amplification (1,021 days, P <0.01). These data suggest that genetic amplification of TYMS is a major mechanism of 5-FU resistance in vivo and have important implications for the management of colorectal cancer patients with recurrent disease.

Chromosomes, Human, Pair 18↗

PubMed2004

Profiling the activity of G proteins in patient-derived tissues by rapid affinity-capture of signal transduction proteins (GRASP).

The next phase in molecular medicine will require the ability to identify signal transduction events inside a cell, in the biologic context of the disease-host interface and at a given point in time. New technologies are needed to profile the activity of these signaling pathways in patient tissue rather than cultured cell lines since the tumor-host microenvironment influences the cellular proteome. We introduce such a technology, rapid affinity capture of signaling proteins (GRASP), to investigate the activity of signaling pathways from patient-derived carcinomas and benign epithelial surfaces and apply it to studying important signaling events in ovarian carcinoma. During the progression from benign ovarian epithelium to invasive carcinoma, there is loss of repression of Rho A as evidenced by its dissociation from its inhibitor, Rho Guanine Nucleotide Dissociation Inhibitor (RhoGDI). GRASP is more informative than simply profiling transcript or protein levels. Furthermore, GRASP coupled with mass spectrometry allowed us to identify a protein-binding partner of RhoGDI, demonstrating the power of this technology in the discovery of potentially novel protein-protein interactions. GRASP represents an advance in the field of proteomics as it detects protein interactions present in cells as they exist in their native tissue microenvironment.

Carcinoma↗

PubMed2004

Ovarian tumorigenesis: a proposed model based on morphological and molecular genetic analysis.

The pathogenesis of ovarian carcinoma, the most lethal gynecological malignancy, is unknown because of the lack of a tumor progression model. Based on a review of recent clinicopathological and molecular studies, we propose a model for their development. In this model, surface epithelial tumors are divided into two broad categories designated type I and type II tumors that correspond to two main pathways of tumorigenesis. Type I tumors tend to be low-grade neoplasms that arise in a stepwise manner from borderline tumors whereas type II tumors are high-grade neoplasms for which morphologically recognizable precursor lesions have not been identified, so-called de novo development. As serous tumors are the most common surface epithelial tumors, low-grade serous carcinoma is the prototypic type I tumor and high-grade serous carcinoma is the prototypic type II tumor. In addition to low-grade serous carcinomas, type I tumors are composed of mucinous carcinomas, endometrioid carcinomas, malignant Brenner tumors, and clear cell carcinomas. Type I tumors are associated with distinct molecular changes that are rarely found in type II tumors, such as BRAF and KRAS mutations for serous tumors, KRAS mutations for mucinous tumors, and beta-catenin and PTEN mutations and microsatellite instability for endometrioid tumors. Type II tumors include high-grade serous carcinoma, malignant mixed mesodermal tumors (carcinosarcoma), and undifferentiated carcinoma. There are very limited data on the molecular alterations associated with type II tumors except frequent p53 mutations in high-grade serous carcinomas and malignant mixed mesodermal tumors (carcinosarcomas). This model of carcinogenesis reconciles the relationship of borderline tumors to invasive carcinoma and provides a morphological and molecular framework for studies aimed at elucidating the pathogenesis of ovarian cancer.

Carcinoma↗

PubMed2004

Molecular genetic analysis of ovarian serous cystadenomas.

Ovarian serous cystadenomas are common ovarian lesions that may be precursors of serous borderline tumors, which can in turn progress to low-grade serous carcinomas. It has been shown that low-grade serous carcinoma and serous borderline tumors are characterized by frequent mutations in BRAF or KRAS genes, but the mutational status of these genes in serous cystadenomas and the clonal nature of serous cystadenomas have not been fully investigated. We isolated cyst-lining epithelium from 30 consecutive serous cystadenomas, and analyzed their BRAF and KRAS mutational status. Wild-type sequences of BRAF and KRAS were detected in all specimens. Using the human androgen receptor gene as a polymorphic marker, we also examined the clonal status of epithelial cells in all of the serous cystadenomas. Four of 29 (14%) informative specimens were monoclonal based on the methylation pattern. These monoclonal cystadenomas were significantly (P<0.01) larger in size (>8 cm) than the nonclonal cystadenomas. These data indicate that serous cystadenomas do not contain mutations in either BRAF or KRAS genes and that most serous cystadenomas are polyclonal. Accordingly, it appears that serous cystadenomas develop as a hyperplastic expansion from epithelial inclusions with a clonal/neoplastic transformation occurring in a subset of them.

Apoptosis↗