Project description:Recent evidence suggests that ovarian high-grade serous carcinoma (HGSC) originates from the epithelium of the fallopian tube. However, most mouse models are based on the previous prevailing view that ovarian cancer develops from the transformation of the ovarian surface epithelium. Here, we report the extensive histological and molecular characterization of the mogp-TAg transgenic mouse, which expresses the SV40 large T-antigen (TAg) under the control of the mouse müllerian-specific Ovgp-1 promoter. Histologic analysis of the fallopian tubes of mogp-TAg mice identified a variety of neoplastic lesions analogous to those described as precursors to ovarian HGSC. We identified areas of normal appearing p53-positive epithelium that are similar to “p53 signatures” in the human fallopian tube. More advanced proliferative lesions with nuclear atypia and epithelial stratification were also identified that were morphologically and immunohistochemically reminiscent of human serous tubal intraepithelial carcinoma (STIC), a potential precursor of ovarian HGSC. Beside these noninvasive precursor lesions, we also identified invasive adenocarcinoma in the ovary of 56% of the mice. Microarray analysis revealed several genes differentially expressed between the fallopian tube of mogp-TAg and WT C57BL/6. One of these genes, Top2a, which encodes topoisomerase II-alpha, was shown by immunohistochemistry to be concurrently expressed with elevated p53 and specifically elevated in mouse STICs, but not in surrounding tissues. TOP2A protein was also found elevated in human STICs, low-grade, and high-grade serous carcinoma. The mouse model reported here displays a progression from normal tubal epithelium to invasive HGSC in the ovary, and therefore closely simulates the current emerging model of human ovarian HGSC pathogenesis. This mouse therefore has the potential to be a very useful new model for elucidating the mechanisms of serous ovarian tumorigenesis, as well as for developing novel approaches for the prevention, diagnosis, and therapy of this disease. Keywords: transgenic mouse model, ovarian cancer, fallopian tube, intraepithelial carcinoma 6 mouse fallopian tubes (FT) were analyzed with experimental repeats; 3 wildtype C57BL6 mice (FT) and 3 transgenic mogp-TAg (FT), with one set of each at 7, 8 and 9 weeks of age.

Project description:Ovarian cancer is the fifth leading cause of cancer death among US women. Evidence supports the hypothesis that high-grade serous ovarian cancers (HGSC) may originate in the distal end of the fallopian tube. Although a heterogeneous disease, 96% of HGSC contain mutations in p53. In addition, the “p53 signature”, or overexpression of p53 protein (usually associated with mutation), is a potential precursor lesion of fallopian tube derived HGSC suggesting an essential role for p53 mutation in early serous tumorigenesis. To further clarify p53-mutation dependent effects on cells, murine oviductal epithelial cells (MOE) were stably transfected with a construct encoding for the R273H DNA binding domain mutation in p53, the most common mutation in HGSC. Mutation in p53 was not sufficient to transform MOE cells, but did significantly increase cell migration. A similar p53 mutation in murine ovarian surface epithelium (MOSE), another potential progenitor cell for serous cancer, was not sufficient to transform the cells nor change migration suggesting tissue specific effects of p53 mutation. Microarray data confirmed expression changes in pro-migratory genes in p53R273H MOE compared to parental cells, which could be reversed by suppressing Slug expression. Combining p53R273H with KRASG12V activation caused transformation of MOE into high-grade sarcomatoid carcinoma when xenografted into nude mice. Elucidating the specific role of p53R273H in the fallopian tube will improve understanding of changes at the earliest stage of transformation and could help develop chemopreventative strategies to prevent the accumulation of additional mutations and reverse progression of the “p53 signature” thereby, improving survival rates. We used a microarray to determine global changes in gene expression as a result of the p53 mutation specifically in mouse oviductal epithelium. Murine oviductal cells (MOE) were obtained from Dr. Barbara Vanderhyden at the University of Ottawa. Stable cell lines were generated using antibiotic resistant plasmids containing p53 R273H (Addgene, plasmid: 16439, donated by Dr. Vogelstein, Johns Hopkins University school of Medicine, Baltimore, MD) or pCMV-Neo (Origene PCMV6XL4, Rockville, MD). Total RNA was extracted from cell pellets collected from consecutive passages.

Project description:Recent evidence suggests that ovarian high-grade serous carcinoma (HGSC) originates from the epithelium of the fallopian tube. However, most mouse models are based on the previous prevailing view that ovarian cancer develops from the transformation of the ovarian surface epithelium. Here, we report the extensive histological and molecular characterization of the mogp-TAg transgenic mouse, which expresses the SV40 large T-antigen (TAg) under the control of the mouse müllerian-specific Ovgp-1 promoter. Histologic analysis of the fallopian tubes of mogp-TAg mice identified a variety of neoplastic lesions analogous to those described as precursors to ovarian HGSC. We identified areas of normal appearing p53-positive epithelium that are similar to “p53 signatures” in the human fallopian tube. More advanced proliferative lesions with nuclear atypia and epithelial stratification were also identified that were morphologically and immunohistochemically reminiscent of human serous tubal intraepithelial carcinoma (STIC), a potential precursor of ovarian HGSC. Beside these noninvasive precursor lesions, we also identified invasive adenocarcinoma in the ovary of 56% of the mice. Microarray analysis revealed several genes differentially expressed between the fallopian tube of mogp-TAg and WT C57BL/6. One of these genes, Top2a, which encodes topoisomerase II-alpha, was shown by immunohistochemistry to be concurrently expressed with elevated p53 and specifically elevated in mouse STICs, but not in surrounding tissues. TOP2A protein was also found elevated in human STICs, low-grade, and high-grade serous carcinoma. The mouse model reported here displays a progression from normal tubal epithelium to invasive HGSC in the ovary, and therefore closely simulates the current emerging model of human ovarian HGSC pathogenesis. This mouse therefore has the potential to be a very useful new model for elucidating the mechanisms of serous ovarian tumorigenesis, as well as for developing novel approaches for the prevention, diagnosis, and therapy of this disease. Keywords: transgenic mouse model, ovarian cancer, fallopian tube, intraepithelial carcinoma

Project description:The cell and tissue of origin of high grade serous ovarian cancer (HGSC) is controversial. While the disease was traditionally assumed to arise from the ovarian surface epithelium (OSE), recent work supports an alternative model implicating the fallopian tube fimbriae epithelium (FTE). We used comparative DNA methylome analyses as a means to test these two competing models, hypothesizing that the HGSC methylome should more closely resemble its tissue of origin. Using two separate analysis methods, analysis within distinct genomic contexts, and validation studies using large-scale publically available HGSC methylome data, we consistently observed that the DNA methylome of HGSC more closely resembles FTE than OSE. These data support the FTE origin model, and suggest DNA methylome analysis as a useful approach to examine cell/tissue lineage origin in cancer. HGSC is the most common and lethal form of epithelial ovarian cancer (EOC). Two distinct tissues have been hypothesized as the tissue of origin of HGSC: OSE and FTE. We hypothesized that the DNA methylome of HGSC would more closely resemble the methylome of its tissue of origin. To test this, we profiled HGSC (n=10), OSE (n=7), and FTE (n=7) primary fresh-frozen tissues, and analyzed DNA methylome using Illumina 450K arrays (n=24) and Agilent Sure Select methyl-seq (n=7). We compared methylomes using statistical analyses of differentially methylated CpG sites (DMC) and differentially methylated regions (DMR), and methylation within a variety of different genomic contexts, including CpG island shores. We also analyzed methylation specifically at Homeobox (HOX) genes, due to their role in tissue specification. We used publically available HGSC methylome data (n=628) to provide additional comparison with FTE and OSE and potential validation. This analysis revealed that HGSC and FTE methylomes were significantly and consistently more highly conserved than were HGSC and OSE. Pearson correlations and hierarchal clustering of genes, promoters, CpG islands, CpG island shores, and HOX genes all revealed the increased relatedness of HGSC and FTE methylomes. In addition, two different large data sets of publically-available HGSC methylome data confirmed these relationships. In summary, our findings support the FTE origin model for HGSC, the most common and deadly EOC subtype. Due to its tissue-specificity and biochemical stability, interrogation of the DNA methylome appears to be a valuable approach to examine cell/tissue lineage in cancer.

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Transformation of the Fallopian Tube Secretory Epithelium Leads to High-grade Serous Ovarian Cancer in BRCA/P53/PTEN Models

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