Ota, Takayo

Abstract Recent molecular and pathologic evidence indicate that high-grade serous carcinomas of the ovary, which are the most common type of epithelial carcinomas, may arise from the distal part of fallopian tubes or tubal carcinoma implants. Oviductal glycoprotein 1 (Ovgp1), a glycosylated protein found in the epithelial cells in the oviduct, is the only specific tubal marker so far. Ovgp1 promoter-driven SV40 large T-antigen transgenic mice develop tumors in the female reproductive organs. To characterize these tumors, we performed immunohistochemical analysis in paraffin-embedded sections. Mice were sacrificed at 8 or 13 weeks old. Macroscopically we observed large tumors in the uterus and cervix and markedly enlarged region in the oviduct. Due to the large tumor in the uterus and cervix, we could not keep the mice longer than 13 weeks. Histologically, there were no major differences in these affected regions between 8 weeks old and 13 weeks old mice. We observed, (i) relatively small ovaries and ovarian follicular hyperplasia, (ii) intact ovarian surface epithelium showing no atypical histology, (iii) atypical epithelial hyperplasia within the oviduct (with endometrioid architectural and cytologic features), (iv) leiomyosarcomatous proliferation in the myometrium, and (v) squamous carcinoma in situ in the cervix or early invasive cervical cancer with extensive papillary architecture. We did not detect metastasis from the tumor to other organs. The atypical abnormalities of the oviduct were more significant in the proximal site to the uterus than the distal site. The proximal oviduct demonstrated weak and spotty p53 expression, beneath the epithelium, similar to p53 signature in the human oviduct. We hypothesized that stem cell components may contribute to the tumor development and that putative cancer stem cells could be identified by stem cell markers. In the oviduct epithelium, Bmi1 expression was not detectable. Cytoplasmic expression of Sox2 was observed in all epithelial cells of the oviduct. There was little correlation between Sox2/Bmi1 staining and p53 staining in the oviduct. Interestingly, Sox2 and Bmi1 staining in the wild-type control mice showed immunoreactive cells interspersed between glandular structures, a pattern similar to previously described label-retaining cells in the endometrium. The expression pattern in Ovgp1-SV40 mice, Bmi1 and Sox2 expression were more obvious in the endometrial stromal area but not in the leiomyosarcoma region, which implies that stem cell components in the endometrial region may support the leiomyosarcoma progression in this mouse model. In conclusion, Ovgp1-SV40 transgenic mouse is a useful model for studies involving fallopian and lower genital tract carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3272. doi:1538-7445.AM2012-3272

Abstract Recent RNA-sequencing studies have identified variant transcripts, fusion transcripts and novel transcripts in cancer. However, little is known about the role of these variant transcripts in tumor development. To identify a specific role of these variant transcripts in tumor development toward chemotherapy resistance, we generated a custom retroviral cDNA expression library from 10 ovarian tumors with resistance to chemotherapy. Retrovirues were generated from the custom library, and they were used to transduced exogenous genes into ovarian cancer cell line A1847, a cell line chosen for its sensitivity to paclitaxel. A1847 cells transduced with retroviruses carrying alkaline phosphatase was used as a control. Transuced cells were selected with 25 nM paclitaxel. 87 clones survived the selection in library-tranduced cells whereas none survived the selection in alkaline phosphatase-tranduced control cells. Forty seven clones survive the secondary screens. Sequence analysis of transduced genes in these surviving clones indicate that 4 paclitaxel-resistant clones contain RABL3 splice variant. Although 195 accessions corresponding to wildtype transcripts are reported in AceView, there is a single accession corresponding to RABL splice variant that we identified in this screen. RNAi-mediated downregulation of RABL3 resulted in enhance sensitivity toward paclitaxel in these resistant clones. Ectopic expression of RABL3 splice variant resulted in increased resistant to paclitaxel. Collectively, these results demonstrate the feasibility of performing functional genetic screens to identify novel splice variants involved in tumor development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5120. doi:1538-7445.AM2012-5120

Abstract The Yin Yang 1 (YY1) transcription factor is a member of Polycomb protein family, with important roles in development, differentiation, replication and cell proliferation. While YY1 expression is correlated with survival in serous ovarian cancer, its role in chemotherapeutic agent-mediated cytotoxicity is not known. Immunoblot analysis revealed that YY1 is highly expressed in ovarian cancer cell lines, but not in immortalized ovarian surface epithelial (OSE) cell lines, suggesting a possible role of YY1 in ovarian carcinogenesis. shRNA mediated stable downregulation of YY1 resulted in inhibition of proliferation by CyQuant assay in SKOV3 and SKOV3ip cells. While YY1 downregulation increased the sensitivity against paclitaxel in both cell lines compared to nontargeted cells (NTC) as determined by MTT and clonogenic assays, it had no effect on sensitivity to cisplatin-mediated cytotoxicity. YY1 downregulated clones treated with paclitaxel resulted in an increase in cleavage of poly (ADP-ribose) polymerase and caspase-3/7 activity compared to NTC clones treated with it in SKOV3 and SKOV3ip1 cells. To determine the mechanism of paclitaxel sensitivity modulated by YY1, we performed cell cycle analysis and determined the expression of microtubules at protein level. Cell cycle analysis showed that downregulation of YY1 decreased the proportion of G0/G1 phase with corresponding increase in cells accumulating both S and G2/M phases in SKOV3 and SKOV3ip1 cells. Using nocodazole which synchronizes cells into mitotic phase, we found that blocking mitotic exit by YY1 knockdown slowed the cyclin B1 proteolysis, thus allowing more time for death initiation by paclitaxel. Immunoblot analysis showed that downregulation of YY1 increased the acetylation of alpha-tubulin and attenuated betaIII-tubulin expression compared to NTC cells. Immunoprecipitation and immunofluorescence assays revealed that YY1 interacts with HDAC6 which deacetylates alpha-tubulin and these proteins co-localized in mitotic phase, suggesting that dysfunction of HDAC6 by downregulation of YY1 could lead to microtubules stabilization, resulting in the paclitaxel-induced apoptosis by blocking mitotic exit. Moreover, nude mice bearing xenografts with stable downregulation of YY1 in SKOV3ip1 were more sensitive to paclitaxel-induced cytotoxicity compared to xenografts of NTC cells. Additionally immunohistchemical staining showed a decrease in betaIII-tubulin expression in tumor of YY1 downregulated clones compared to that of NTC clones. Collectively, these results indicate that YY1 acts as a modulator of microtubules expression and might be therapeutically targeted against epithelial ovarian cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4960. doi:1538-7445.AM2012-4960

Abstract It was well accepted for many years that ovarian surface epithelium is the origin of epithelial ovarian carcinomas. However, recent molecular and pathologic evidence indicate that high-grade serous carcinomas of the ovary, which are the most common type of epithelial carcinomas, may also arise from the distal part of fallopian tubes or tubal carcinoma implants. Gene expression profiles of tubal epithelium from BRCA mutation carriers resemble those of high-grade serous carcinomas of the ovary, and ovarian carcinomas and tubal intraepithelial carcinomas have identical p53 mutations. Oviductal glycoprotein 1 (Ogp1) is a glycosylated protein found in the epithelial cells in the oviduct. So far, Ogp1 is the only specific tubal marker for the oviduct. Ogp1 promoter-driven SV40 large T-antigen transgenic mice develop tumors in the female reproductive organs. To characterize these tumors, we did immunohistochemical analysis in frozen and paraffin-embedded sections. Mice were sacrificed at 8 weeks old. Macroscopically the cervico-vaginal region and the fallopian tubes were markedly enlarged. Histologically, three distinct abnormal proliferations were observed; (i) epithelial hyperplasia with cytologic atypia in the oviduct (with endometrioid architectural and cytologic features), (ii) leiomyosarcomatous proliferation in the myometrium, and (iii) squamous carcinoma in situ in the cervix with extensive papillary architecture. SV40 was expressed in these tumor sites. The oviduct demonstrated weak and spotty p53 expression. The expression of Ogp1 and Pax8 (a marker of the salpingeal secretory cells) in the oviduct epithelium showed patchy pattern. Ogp1 expression was not associated with cellular atypia, while Pax8 was expressed in normal cells. Expression of DNA replication licensing factor, Mini-chromosome maintenance protein 7(MCM7), was also mixed. MCM7 expression was higher in neoplastic cells, but atypical cells had less MCM7 expression. A serous marker, WT1, and a Müllerian-specific epithelial marker, Pax2, showed lower expressions in Ogp1-SV40 transgenic mouse compared to wild type control mouse. WT1 and Pax2 expression were uniform. In ovarian surface epithelium, there was no malignant transformation and no different expression of these markers in control and Ogp1-SV40 mice. In conclusion, this study demonstrated that Ogp1-SV40 transgenic mouse develops abnormal oviductal, myometrial, and cervical proliferations with no involvement of ovaries. Weak and spotty p53 expression in the oviduct indicates that p53 pre-dysfunction status in non-malignant precursor lesions. These results indicate that Ogp1-SV40 transgenic mouse is a useful model for studies involving fallopian and low genital tract carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3276.

Abstract Mini-Chromosome Maintenance protein 7 (MCM7) is involved in replicative licensing and synthesis of DNA. It is previously identified as over-expressed gene in high-grade serous carcinomas compared to serous borderline tumors of the ovary in cDNA microarray studies. In this study, we sought to validate MCM7 expression in ovarian tumors by applying immunohistochemical analysis on tissue microarrays consisting of 445 ovarian tumors. MCM7 expression was quantified as MCM7 labeling index by determining the tumor nuclei positive for MCM7 staining as a percentage of total tumor nuclei. The labeling index scores were independently generated by two methods: PATH score provided by a manual review of each samples by a pathologist and ACIS score provided by Automated Cell Imaging System. Analyses of both scores indicated high degree of concordance in score distribution between PATH and ACIS. MCM7 expression is significantly higher in high-grade serous carcinomas compared to serous borderline tumors, confirming our previous cDNA microarray studies. In both PATH and ACIS analysis, MCM7 expression is also significantly higher in high-grade serous carcinomas compared to other histology subtypes of ovarian cancer. Finally, to identify the clinical significance of MCM7 expression, we determined the association between MCM7 expression and disease-free survival. MCM7 labeling index was dichotomized into two groups (high and low) using median labeling index as cut-off. For both PATH or ACIS-derived scores, univariate analyses indicate significant association of high MCM7 labeling index with better disease-free survival in high-grade serous carcinomas. These results suggest the clinical significance of MCM7 expression in high-grade serous carcinomas of the ovary and the need for further evaluation of MCM7 as a potential theranostic biomarker. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4637.

AbstractPurpose: The purpose of this study was to determine if loss of serine protease HtrA1 in endometrial cancer will promote the invasive potential of EC cell lines.Experimental design: Western blot analysis and immunohistochemistry methods were used to determine HtrA1 expression in EC cell lines and primary tumors, respectively. Migration, invasion assays and in vivo xenograft experiment were performed to compare the extent of metastasis between HtrA1 expressing and HtrA1 knocked down clones.Results: Western blot analysis of HtrA1 in 13 EC cell lines revealed complete loss of HtrA1 expression in all seven papillary serous EC cell lines. Downregulation of HtrA1 in Hec1A and Hec1B cell lines resulted in a three- to fourfold increase in the invasive potential. Exogenous expression of HtrA1 in Ark1 and Ark2 cells resulted in three- to fourfold decrease in both invasive and migration potential of these cells. There was an increased rate of metastasis to the lungs associated with HtrA1 downregulation in Hec1B cells compared to control cells with endogenous HtrA1 expression. Enhanced expression of HtrA1 in Ark2 cells resulted in significantly less tumor nodules metastasizing to the lungs compared to parental or protease deficient (SA mutant) Ark2 cells. Immunohistochemical analysis showed 57% (105/184) of primary EC tumors had low HtrA1 expression. The association of low HtrA1 expression with high-grade endometrioid tumors was statistically significant (P = 0.016).Conclusions: Collectively, these data indicate loss of HtrA1 may contribute to the aggressiveness and metastatic ability of endometrial tumors. Clin Cancer Res; 17(3); 427–36. ©2010 AACR.

Abstract We previously identified serine protease HtrA1 as a downregulated gene in epithelial ovarian cancer (EOC), but the functional consequence of loss of HtrA1 in EOC remains largely unclear. Here, we report that loss of HtrA1 attenuates anoikis—a critical physiologic barrier for tumor metastasis. In response to loss of anchorage, HtrA1 expression was upregulated in SKOV3 cells, resulting in autocatalytic activation of HtrA1. Stable knockdown of HtrA1 in SKOV3 and TOV21G cells resulted in resistance to anoikis due to enhanced activation of epidermal growth factor receptor (EGFR)/AKT pathway. In suspended SKOV3 cells, enhanced expression of HtrA1 inhibited EGFR/AKT pathway, leading to increased cell death, whereas protease-inactive mutant HtrA1 failed to result in either the inhibition of EGFR/AKT pathway or increased cell death, suggesting the requirement of HtrA1 protease activity in regulating anoikis. Immunoprecipitation and immunofluorescence assays revealed that HtrA1 interacted with EGFR not only on the cell membrane but also in the nucleus. Most importantly, downregulation of HtrA1 significantly enhanced the peritoneal dissemination of SKOV3ip1 cells in nonobese diabetic/severe combined immunodeficient mice, with increased phospho-EGFR level in corresponding tumor nodules compared with that in xenografts originated from the control cells. Taken together, these data reveal for the first time a novel function of HtrA1 in promoting anoikis by attenuating activation of EGFR/AKT pathway that may contribute to its metastasis suppression capacity, thus providing a possible explanation for the aggressive nature of human ovarian tumors with downregulated HtrA1. Cancer Res; 70(8); 3109–18. ©2010 AACR.