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Whole exome sequence analysis of serous borderline tumors of the ovary.

ABSTRACT: OBJECTIVE:Serous borderline tumor (SBT) is a unique histopathologic entity of the ovary, believed to be intermediate between benign cystadenoma and invasive low-grade serous carcinoma. While somatic mutations in the KRAS or BRAF, and rarely ERBB2, genes have been well characterized in SBTs, other genetic alterations have not been described. Toward a more comprehensive understanding of the molecular genetic architecture of SBTs, we undertook whole exome sequencing of this tumor type. METHODS:Following pathologic review and laser capture microdissection to enrich for tumor cells, whole exomes were prepared from DNA of two independent SBTs and subjected to massively parallel DNA sequencing. RESULTS:Both tumors contained an activating mutation of the BRAF gene. A total of 15 additional somatic mutations were identified, nine in one tumor and six in the other. Eleven were missense mutations and four were nonsense or deletion mutations. Fourteen of the 16 genes found to be mutated in this study have been reported to be mutated in other cancers. Furthermore, 12 of these genes are mutated in ovarian cancers. The FBXW7 and KIAA1462 genes are noteworthy candidates for a pathogenic role in serous borderline tumorigenesis. CONCLUSIONS:These findings suggest that a very small number of somatic genetic mutations are characteristic of SBTs of the ovary, thus supporting their classification as a relatively genetically stable tumor type. The mutant genes described herein represent novel candidates for the pathogenesis of ovarian SBT.

SUBMITTER: Boyd J

PROVIDER: S-EPMC4083840 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Whole exome sequence analysis of serous borderline tumors of the ovary.

Boyd Jeff J Luo Biao B Peri Suraj S Wirchansky Beth B Hughes Lucinda L Forsythe Caitlin C Wu Hong H

Gynecologic oncology 20130614 3

<h4>Objective</h4>Serous borderline tumor (SBT) is a unique histopathologic entity of the ovary, believed to be intermediate between benign cystadenoma and invasive low-grade serous carcinoma. While somatic mutations in the KRAS or BRAF, and rarely ERBB2, genes have been well characterized in SBTs, other genetic alterations have not been described. Toward a more comprehensive understanding of the molecular genetic architecture of SBTs, we undertook whole exome sequencing of this tumor type.<h4>M ...[more]

PMID: 23774303

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Project description:BACKGROUND: We showed there are specific ALDH1 autoantibodies in ovarian autoimmune disease and ovarian cancer, suggesting a role for ALDH1 in ovarian pathology. However, there is little information on the ovarian expression of ALDH1. Therefore, we compared ALDH1 expression in normal ovary and benign and malignant ovarian tumors to determine if ALDH1 expression is altered in ovarian cancer. Since there is also recent interest in ALDH1 as a cancer stem cell (CSC) marker, we assessed co-expression of ALDH1 with CSC markers in order to determine if ALDH1 is a potential CSC marker in ovarian cancer. METHODS: mRNA and protein expression were compared in normal human ovary and serous ovarian tumors using quantitative Reverse-Transcriptase PCR, Western blot (WB) and semi-quantitative immunohistochemistry (IHC). ALDH1 enzyme activity was confirmed in primary ovarian cells by flow cytometry (FC) using ALDEFLUOR assay. RESULTS: ALDH1 mRNA expression was significantly reduced (p < 0.01; n = 5) in malignant tumors compared to normal ovaries and benign tumors. The proportion of ALDH1+ cells was significantly lower in malignant tumors (17.1 ± 7.61%; n = 5) compared to normal ovaries (37.4 ± 5.4%; p < 0.01; n = 5) and benign tumors (31.03 ± 6.68%; p < 0.05; n = 5). ALDH1+ cells occurred in the stroma and surface epithelium in normal ovary and benign tumors, although surface epithelial expression varied more in benign tumors. Localization of ALDH1 was heterogeneous in malignant tumor cells and little ALDH1 expression occurred in poorly differentiated malignant tumors. In benign tumors the distribution of ALDH1 had features of both normal ovary and malignant tumors. ALDH1 protein expression assessed by IHC, WB and FC was positively correlated (p < 0.01). ALDH1 did not appear to be co-expressed with the CSC markers CD44, CD117 and CD133 by IHC. CONCLUSIONS: Total ALDH1 expression is significantly reduced in malignant ovarian tumors while it is relatively unchanged in benign tumors compared to normal ovary. Thus, ALDH1 expression in the ovary does not appear to be similar to breast, lung or colon cancer suggesting possible functional differences in these cancers. SIGNIFICANCE: These observations suggest that reduced ALDH1 expression is associated with malignant transformation in ovarian cancer and provides a basis for further study of the mechanism of ALDH1 in this process.

Project description:Objectives and goals: The causes and molecular pathology of ovarian cancer are essentially unknown. However, it is generally understood that serous ovarian borderline tumors (SBOT) and well differentiated (WD) serous ovarian carcinomas (SC) have a similar tumorigenetic pathway, distinct from moderately (MD) and poorly differentiated (PD) SC. The aim of this study was to identify mRNAs differentially expressed between MD/PD SC, SBOT and superficial scrapings from normal ovaries (SNO),and to correlate these mRNAs with clinical parameters. Results: From the global gene expression analyses, thirty mRNAs differentially expressed between MD/PD SC, SBOT and SNO were selected and validated by RT-qPCR, verifying 21 mRNAs to be significantly differentially expressed (p<0.01). Of these, 13 mRNAs were differentially expressed in MD/PD SC compared with SNO (p<0.01) and were correlated with clinical parameters. VEGFA was significantly upregulated (FC=6.1, p=6.0x10-6), and correlated with progression-free survival (p=0.037). ZNF385B was significantly downregulated (FC=-130.5, p=1.2x10-7), and correlated with overall survival (p=0.03). An increased TPX2 (p=0.03) and FOXM1 (p=0.044) expression correlated with optimal normalization of serum CA125 after treatment. Furthermore, we present a common molecular pathway for MD/PD SC, including VEGFA, FOXM1, TPX2, BIRC5 and TOP2A, all significantly upregulated and interacting with TP53. Conclusions: We have identified 21 mRNAs differentially expressed (p<0.01) between MD/PD SC, SBOT and SNO. Thirteen were differentially expressed in MD/PD SC, including VEGFA and ZNF385B, correlating with survival, and FOXM1 and TPX2, correlating with normalization of serum CA125. By the use of oligonucleotid microarrays (Affymetrix U133 Plus 2.0 Arrays) differences in mRNA expression between eleven MD/PD SC, eight SBOT and four SNO samples were analyzed. Differentially expressed mRNAs were selected for validation by RT-qPCR in additional samples totaling 21 MD/PD SC, 13 SBOT and seven samples of SNO. Each mRNA was run in quadruple. The mRNAs differentially expressed in MD/PD SC compared with SNO were correlated with clinical parameters.

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Whole exome sequence analysis of serous borderline tumors of the ovary.

Publications

Whole exome sequence analysis of serous borderline tumors of the ovary.

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