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No description available.

Oncolytic adenoviral gene therapy has potential as a novel anti-cancer agent for ovarian cancer. Host immune responses are thought to contribute to its therapeutic effects. However further evaluation has been hampered by the lack of an immunocompetent animal model. This is predominantly because human adenovirus is highly species-specific and replicates poorly in murine cells. The second generation human adenovirus (hAd5) type 5 mutant dl922-947 contains a deletion in the E1A CR2 region which allows it to replicate selectively in cells with Rb pathway abnormalities, a finding observed in >90% of human cancers. Previous work has shown that dl922-947 has considerable activity in ovarian cancer and is more potent than E1A wild-type adenoviruses and the E1B-55K mutant dl1520 (Onyx-015, H101). Unfortunately, like its wild-type counterpart, dl922-947 replicates poorly in murine cells and infectious virion progeny are not generated. Mechanisms for the failure of infectious virion formation remain unclear and have been investigated as part of this project. I have found that murine malignant cells can be infected readily with hAd5 vectors. Both early and late viral genes are transcribed and there is evidence of viral genome replication. However, a profound failure of infective virion production is observed together with low levels of late viral protein expression. Ribosome fractionation assays show reduced viral mRNA loading in murine cells, resulting in failure of translation, especially of late transcripts. Aberrant function of the non-structural L4 protein 100K has been identified as a major hurdle to successful viral replication in murine cells. Ectopic expression of L4 100K promotes translation of viral late mRNA and increases expression of late viral proteins and virion production. However, these increases are only partial.

Tumour suppressor 73 (Trp73) gene shares structural and functional homology with p53. Trp73 encodes multiple isoforms with opposing effects. The TAp73 isoform is a transcription factor and is classified as a tumour suppressor where as the DNp73 isoform is a putative oncogene. Imbalance of the two opposing isoforms has been reported in human malignancies including ovarian cancer. TAp73 deficiency results in a dramatic increase in the DNp73 isoform, mimicking the altered isoform balance observed in human ovarian cancer. The effects of TAp73 deficiency in mouse OSE cells were assessed. TAp73 deficiency is not sufficient to induce ovarian cancer in mice. However, TAp73 deficiency compromises cellular proliferation in OSE cell lines. Furthermore, expression of p73 isoforms and epithelial markers is altered in TAp73 deficient cell line. Further studies are needed to determine if TAp73 deficiency in conjunction with other molecular alterations can mediate transformation of OSE cells leading to ovarian cancer.

Tumour suppressor 73 (Trp73) gene shares structural and functional homology with p53. Trp73 encodes multiple isoforms with opposing effects. The TAp73 isoform is a transcription factor and is classified as a tumour suppressor where as the DNp73 isoform is a putative oncogene. Imbalance of the two opposing isoforms has been reported in human malignancies including ovarian cancer. TAp73 deficiency results in a dramatic increase in the DNp73 isoform, mimicking the altered isoform balance observed in human ovarian cancer. The effects of TAp73 deficiency in mouse OSE cells were assessed. TAp73 deficiency is not sufficient to induce ovarian cancer in mice. However, TAp73 deficiency compromises cellular proliferation in OSE cell lines. Furthermore, expression of p73 isoforms and epithelial markers is altered in TAp73 deficient cell line. Further studies are needed to determine if TAp73 deficiency in conjunction with other molecular alterations can mediate transformation of OSE cells leading to ovarian cancer.

Linker histone H1 associates with nucleosomes, facilitating folding and packaging of DNA into higher order chromatin structure. With 11 variants in mammals, histone H1 is the most divergent histone class. Histone H1 variants are differentially expressed during development and cellular differentiation, and regulate specific gene expression in vivo. Ample studies have established the role of linker histone H1 in chromatin compaction and gene expression regulation; however, its role in diseases, such as cancer, remain understudied. In this study, we explore the role of H1 in ovarian cancer, one of the most devastating gynecological cancers due to its poor prognosis and difficulty in early diagnosis. Although mutations of genes responsible for cell proliferation, differentiation and survival have been found in ovarian cancers, ample evidence also suggests an important role of epigenetic changes in the disease occurrence and progression. Because epigenetic changes do not alter DNA sequence and can be reversed or reprogrammed, they offer an attractive avenue for therapeutic intervention in cancer treatment. Using quantitative RT-PCR assays, we systematically examined the expression of 7 H1 genes in 33 human epithelial ovarian tumors. By clustering analysis, we found that ovarian malignant adenocarcinomas and benign adenomas exhibited characteristic expression patterns. We demonstrate that expression profiling of 7 H1 genes in tumor samples discriminates adenocarcinomas vs. adenomas with high accuracy. These findings indicate that the expression of H1 variants is exquisitely regulated and may serve as potential epigenetic biomarkers for ovarian cancer. To further investigate the role of H1 subtypes in ovarian cancer cells, we employ an over-expression approach to test the function of H1 subtypes in an ovarian cancer cell line OVCAR-3. We found that histone H1.3 over-expression significantly suppresses the growth and colony formation of OVCAR-3 cells. Gene expression arrays identified many genes affected by H1.3 over-expression, and oncogene H19 is among the genes most dramatically repressed by H1.3 over-expression. Over-expression of several other H1 subtypes does not lead to significant reduction of H19 expression, suggesting a specific effect by H1.3. Consistently, knockdown of H1.3 increases H19 expression. Furthermore, increased expression of H1.3 leads to accumulation of H1.3 as well as increased DNA methylation at the regulatory regions of H19. Finally we identified a synergistic effect of H1.3 over-expression and H19 knockdown on inhibition of ovarian cancer cell growth. These results establish oncogene H19 as a direct target of histone H1.3, identify a novel role of H1 variants in ovarian cancer mediated through regulating oncogene H19 expression, and may offer new approaches for ovarian cancer therapeutics.

High Grade Serous Carcinoma is the most aggressive tubal/ovarian histotype. The Rb pathway, which functions to preserve cell cycle regulation and genomic stability, is frequently deregulated in HGSC. The aim of this study was to identify non-redundant mechanisms of Rb pathway deregulation with clinical relevance. Immunohistochemistry analysis of P16 and RB1 expression identified a P16 homogeneous/RB1+ subgroup with the shortest recurrence free survival, while P16 heterogeneous/RB1+ and P16 homogenous/RB1- subgroups showed longer recurrence free survival. These P16/RB1 categories were shared between precursor lesions and the associated HGSC. Characterization of the Rb pathway in the three subgroups revealed CCNE1 amplification and highest protein expression in the P16 homogeneous/RB1+, high cyclin D1 protein expression in P16 heterogeneous/RB1+, and E2F3 amplification and highest Ki67 protein expression in P16 homogeneous/RB1- subgroup. Rb pathway deregulation is common in HGSC, occurs early in tumor development, and results from multiple non-redundant mechanisms that correlate with clinical outcome.

High Grade Serous Carcinoma is the most aggressive tubal/ovarian histotype. The Rb pathway, which functions to preserve cell cycle regulation and genomic stability, is frequently deregulated in HGSC. The aim of this study was to identify non-redundant mechanisms of Rb pathway deregulation with clinical relevance. Immunohistochemistry analysis of P16 and RB1 expression identified a P16 homogeneous/RB1+ subgroup with the shortest recurrence free survival, while P16 heterogeneous/RB1+ and P16 homogenous/RB1- subgroups showed longer recurrence free survival. These P16/RB1 categories were shared between precursor lesions and the associated HGSC. Characterization of the Rb pathway in the three subgroups revealed CCNE1 amplification and highest protein expression in the P16 homogeneous/RB1+, high cyclin D1 protein expression in P16 heterogeneous/RB1+, and E2F3 amplification and highest Ki67 protein expression in P16 homogeneous/RB1- subgroup. Rb pathway deregulation is common in HGSC, occurs early in tumor development, and results from multiple non-redundant mechanisms that correlate with clinical outcome.

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Gonadotrophin surge attenuating factor (GnSAF) is a non-steroidal ovarian factor which reduces pituitary responsiveness to GnRH both <I>in vitro</I> and <I>in vivo</I>. GnSAF is present in serum from superovulated women in a 141 kDa molecular weight form. GnSAF bioactivity (suppression of GnRH-induced LH secretion from cultured rat pituitary cells) in serum from superovulated women is not overcome by incubation with an inhibin antibody, demonstrating that it is distinct from inhibin. Under the culture conditions used, the ovarian steroids had no significant suppressive effects on GnRH-induced LH secretion, showing that GnSAF bioactivity is not due oestradiol or progesterone. GnSAF is also present in serum from the follicular phase of spontaneously cycling women with maximal levels being produced during the mid follicular phase. It has been suggested that GnSAF production during the follicular phase suppresses LH release from the pituitary until the levels of oestradiol produced by the developing follicle are high enough to overcome the effects of GnSAF and the LH surge occurs. However, suppression of LH secretion by an enriched GnSAF preparation is potentiated by oestradiol and progesterone, both individually and in combination. This suggests that it is not a rise in steroid positive feedback but a decrease in GnSAF negative feedback which enables the LH surge to occur. Follistatin and GnSAF in combination have additive effects on the suppression of GnRH-induced LH secretion, whereas GnSAF and inhibin in combination cause no greater suppression than they do individually. GnSAF present in inhibin-stripped human follicular fluid is also able to reduce both the GnRH self-priming response, and its augmentation by progesterone, by rat pituitary cells in culture after only 90 minutes exposure. Inhibin and follistatin have no such effects under the same conditions.