Annie Ny Cheung

Somatic mutations in the BRCA1 gene in Chinese sporadic breast and ovarian cancer

Inherited mutations in the BRCA1 gene confer increased susceptibility to breast and ovarian cancer. Its role in sporadic carcinogenesis is not well defined. Somatic mutations in breast cancers have not been reported and to date there are only three reports of somatic mutations in sporadic ovarian cancers. To investigate the contribution of BRCA1 mutations to sporadic breast and ovarian cancer in the Chinese population, we analysed 62 samples from Chinese women using the protein truncation test. There were 40 cases of breast cancer under age 50 and 22 cases of ovarian cancer, all unselected for family history. There was no age selection for the ovarian cancers. We found two somatic BRCA1 mutations in exon 11, one in a breast cancer and the other in an ovarian cancer, both of which result in truncated proteins. Our results indicate that somatic BRCA1 mutations, like somatic mutations in the BRCA2 gene, though very rare, can be found in both breast and ovarian cancers and support a tumor suppressor function for BRCA1 in sporadic tumors.

Barriers and facilitators to human papillomavirus vaccination among Chinese adolescent girls in Hong Kong: a qualitative–quantitative study

Objectives: To explore perceptions towards cervical cancer, human papillomavirus (HPV) infection and HPV vaccination and to identify factors affecting the acceptability of HPV vaccination among Chinese adolescent girls in Hong Kong. Methods: Six focus groups were conducted with Chinese adolescent girls (median age 16 years, age range 13–20, n  =  64) in Hong Kong in April 2007. Thematic analysis was employed to identify major themes related to cervical cancer and HPV vaccination. A supplementary questionnaire was administered to all participants before and after group discussion to assess their knowledge, attitudes and intention to be vaccinated and to collect demographic information. Results: Participants’ knowledge on cervical cancer was limited and HPV was largely unheard of. They had difficulty understanding the mechanism linking cervical cancer with HPV infection. Participants held a favourable attitude towards HPV vaccination but the perceived timing of vaccination varied. Barriers to vaccination include high monetary cost, uncertain length of vaccine effectiveness, low perceived risk of HPV infection, no immediate perceived need of vaccination, anticipated family disapproval and fear of the pain of injection. Factors conducive to vaccination include perceived family and peer support and medical reassurance on safety and efficacy of vaccine. The differences on knowledge, attitudes, intention to be vaccinated now and willingness to conform to significant others before and after the discussion were statistically significant, with an increased tendency towards favouring vaccination after the focus group. Conclusions: Participants favoured HPV vaccination despite not feeling an immediate need to be vaccinated. Interventions could focus on providing professional information on HPV vaccination and raising adolescents’ perceived need to take preventive measures against HPV infection.

Loss of Programmed cell death 4 (Pdcd4) associates with the progression of ovarian cancer

BackgroundProgrammed cell death 4 (Pdcd4) is a novel tumour suppressor and originally identified as a neoplastic transformation inhibitor. The aim of this study was to investigate the expression, prognostic significance and potential function of Pdcd4 in ovarian cancer.ResultsThe expression of Pdcd4 was examined in 30 normal ovarian tissues, 16 borderline and 93 malignant ovarian tissues. A continuous down regulation of Pdcd4 expression in the sequence of normal, borderline and malignant tissues was observed. The expressions of Pdcd4 in both ovarian borderline tissues and carcinomas were significantly lower than the expression in normal ovarian tissues (p < 0.001). Furthermore, patients with lower Pdcd4 expressions were found to have shorter disease-free survival (p = 0.037). The expression of Pdcd4 was also assessed by immunohistochemical analysis in 13 ovarian normal tissues and 44 carcinomas. Different subcellular localization of Pdcd4 was observed in normal compared to malignant cells. Predominant nuclear localization of Pdcd4 was found in normal ovarian tissues while ovarian carcinomas showed mainly cytoplasmic localization of Pdcd4.ConclusionOur study demonstrated that the loss of Pdcd4 was a common abnormality at molecular level in ovarian cancer and it might be a potential prognostic factor in ovarian cancer patients.

Aberrant activation of hedgehog signaling pathway contributes to endometrial carcinogenesis through β -catenin

The hedgehog and Wnt signaling pathways play important roles in human cancers with possible interaction. This study aimed at analysis and correlation of the expression of Gli1, a transcriptional factor and target gene of hedgehog signaling pathway, with clinicopathological parameters and expression of β-catenin, an important member of the Wnt pathway, in normal, hyperplastic and malignant endometrium. Immunohistochemical study on 15 normal endometrium, 14 simple and complex hyperplasia without atypia, 37 atypical complex hyperplasia and 80 endometrial cancers showed significant Gli1 overexpression and β-catenin nuclear immunoreactivity in endometrial cancers and atypical endometrial hyperplasia when compared with normal endometrium (P<0.05). Overexpression of Gli1 in endometrial cancers correlated with well-differentiated histological grade (P<0.001), non-myometrial invasion (P=0.004) and superficial myometrial invasion (P=0.041). β-Catenin nuclear immunoreactivity was also associated with well-differentiated histology (P=0.013). Gli1 overexpression positively correlated with β-catenin nuclear immunoreactivity in atypical complex hyperplasia (P=0.013) and endometrial carcinoma (P=0.017). Similar Gli1 and β-catenin protein expression pattern was observed in normal and endometrial cancer cell lines by western blotting. We further showed a complex formation between Gli1 and β-catenin protein in endometrial cancer cell lines in an immunoprecipitation study. Ectopic overexpression of Gli1 into endometrial cancer cells led to reduced expression of β-catenin in cell cytoplasm and increased expression of β-catenin in the nuclei. In summary, overexpression of Gli1 was an early event in endometrial carcinogenesis. Aberrant activation of hedgehog pathway may play important roles in endometrial cancer through β-catenin nuclear accumulation.

Targeting Estrogen-Related Receptor Alpha Inhibits Epithelial-to-Mesenchymal Transition and Stem Cell Properties of Ovarian Cancer Cells

Epithelial-mesenchymal transition represents a key event in cancer progression and has emerged as a promising anticancer target. Estrogen-related receptor alpha (ERRα) is frequently elevated in advanced-stage ovarian cancer, but its potential role in tumor progression is not known. Here we show that ERRα functions in epithelial-mesenchymal transition and in subsequent stem cell traits responsible for the acquisition of high degree of aggressiveness and potential for metastasis that are characteristic of ovarian cancer. Importantly, targeted inhibition of ERRα also inhibited the expression of Snail, a repressor of E-cadherin and an inducer of epithelial-mesenchymal transition. Interestingly, induction of Snail resulted from not only changes in mRNA transcription rate but also mRNA stability. We thus identified the miR-200 family as a new player in the ERRα-mediated posttranscriptional regulation of Snail, and antagonism of miR-200a/b could revert the decreased expression of Snail and reversal of epithelial-mesenchymal transition and stem cell characteristics due to ERRα depletion. Finally, we showed that RNA interference-mediated inhibition of ERRα significantly reduced tumor burden, ascites formation, and metastatic peritoneal nodules in vivo in an orthotopic model of ovarian cancer. These results suggest ERRα activation as a mechanism of tumor aggressiveness and imply that targeting ERRα may be a promising approach in ovarian cancer treatment.

Pathogenesis of choriocarcinoma: clinical, genetic and stem cell perspectives

Choriocarcinoma is a unique malignant neoplasm composed of mononuclear cytotrophoblasts and multinucleated syncytiotrophoblasts that produce human chorionic gonadotrophin. Choriocarcinoma can occur after a pregnancy, as a component of germ cell tumors, or in association with a poorly differentiated somatic carcinoma, each with distinct clinical features. Cytogenetic and molecular studies, predominantly on gestational choriocarcinoma, revealed the impact of oncogenes, tumor suppressor genes and imprinting genes on its pathogenesis. The role of stem cells in various types of choriocarcinoma has been studied recently. This review will discuss how such knowledge can enhance our understanding of the pathogenesis of choriocarcinoma, enable exploration of novel anti-choriocarcinoma targeted therapy and possibly improve our insight on embryological and placental development.

Zic2 synergistically enhances Hedgehog signalling through nuclear retention of Gli1 in cervical cancer cells

Aberrant activation of Hedgehog (Hh) signalling has been implicated in the pathogenesis of human cancers. However, the cognate molecular mechanisms contributing to this disregulated pathway are incompletely understood. In this study, we showed that Zic2 was frequently over‐expressed and associated with high‐grade cervical cancer (p = 0.032), high levels of Gli1 (p < 0.001) and CyclinD1 (p < 0.001) by immunohistochemical and quantitative RT–PCR analyses. Further biochemical studies using luciferase reporter, co‐immunoprecipitation, subcellular fractionation and immunofluorescence analyses demonstrated that Zic2 can physically interact with Gli1 and retain it in the nucleus, which in turn increases Gli‐mediated transcriptional activity. Gain‐ and loss‐of‐function analyses of Zic2 showed that Zic2 could increase Hh signalling activity, cell proliferation and anchorage‐independent growth ability in cervical cancer cells. Conversely, deletion of the zinc finger domain at C‐terminus of Zic2 significantly abrogated its interaction with Gli1, the retention of Gli1 in the nucleus, effects on Hh signalling activity and oncogenic properties in cervical cancer cells. Our findings suggest that Zic2 is a positive modulator increasing Gli1 transcriptional and oncogenic activity by retaining Gli1 in the nucleus of cervical cancer cells. Copyright

TrkB as a therapeutic target for ovarian cancer.

Background: In many countries, ovarian cancer is the most lethal gynecological malignancy. Its poor prognosis is mainly due to the late stage of disease with metastasis at presentation. The significant failure rate of chemotherapy in patients with advanced stage disease is also a main concern. As such, developing novel therapeutic targets is essential to improve long-term survival. Overexpression of Tropomyosin-related kinase B (TrkB), a tyrosine kinase receptor, has been documented in ovarian cancer and is found to be correlated with poor prognosis. Objective/methods: We discuss the functional roles and the related downstream signaling pathways of TrkB and its ligand brain-derived neurotrophic factor (BDNF) in ovarian cancer. The possible crosstalk between TrkB/BDNF and other putative molecular targets in ovarian cancer is also discussed. Results/conclusions: All these latest findings shed light on the application of TrkB as a therapeutic target for ovarian cancer.

Stem cell transcription factor NANOG in cancers – is eternal youth a curse?

ABSTRACT Introduction: Targeting cancer stem cells can be a more effective approach to treat cancer. NANOG is one of the key factors for maintaining the self-renewal ability and pluripotency of stem cells, including cancer stem cells. Overexpression of NANOG has been observed in various human malignancies. Several reports have suggested that NANOG contributes to carcinogenesis by initiating and preserving cancer stem cells. It is obvious that NANOG is also involved in establishing other hallmarks of cancer such as uncontrolled cell growth, chemoresistance, metastasis, and immune evasion. Areas covered: This review will discuss the molecular properties and oncogenic roles of NANOG. The idea of using agents that inhibit the transcription factor to treat cancer is presented. Interfering with NANOG-mediated transcriptions using small interfering RNA, transcription factor decoy, genome editing, and small-molecule inhibitors may provide novel strategies to target cancer stem cells. Expert opinion: As a pivotal controller in cancer stem cell maintenance and a positive regulator of various oncogenic pathways, NANOG may be an important target for cancer therapy. However, as a transcription factor, it is inherently difficult to target by pharmacological means. Novel approaches need to be explored before the inhibition of NANOG can be applied in a clinical setting.

Abstract 5006: Pdcd4 as a prognostic factor and a modulator of cell proliferation, migration and invasion in ovarian cancer

Programmed cell death 4 (Pdcd4), a novel gene and originally identified as the neoplastic transformation inhibitor, is down regulated in human colon, breast and lung cancer cells and considered as a diagnostic and prognostic marker in lung cancer. It has been shown to have tumor suppressor properties such as inhibition of cell invasion and proliferation, as well as induction of apoptosis. However, those properties of Pdcd4 are tissue specific. The mechanisms of function of Pdcd4 are largely unknown and its function and modulation in ovarian cancer is still elusive. The objectives of our present study are firstly to investigate the expression of Pdcd4 in normal and malignant ovarian tissues and the role of Pdcd4 in ovarian carcinogenesis; and secondly, to study the function of Pdcd4 in the regulation of cell proliferation, migration and invasion and modulation of Pdcd4 in ovarian cancer. Using both western blot and real-time quantitative PCR analyses, we demonstrated that Pdcd4 expression was continuously down-regulated in the sequence of normal-borderline-malignant ovarian tissue samples. Higher Pdcd4 expression was found to be associated with longer disease-free survival (p=0.037). Using immunohistochemical staining approach, we found the subcellular localization of Pdcd4 differed in the way that, normal ovarian tissues showed distinctive nuclear localization while malignant ovarian tissues showed mainly cytoplasmic staining. To further explore the function of Pdcd4 in ovarian cancer cells, we developed Pdcd4 over-expression stable clones in ovarian cancer cell lines. Our in vitro studies demonstrated that ectopic Pdcd4 expression significantly inhibited ovarian cancer cell proliferation by inducing cell cycle arrest at G0/G1 stage and the upregulation of cell cycle regulators p27 and p21. The induction of p21 by Pdcd4 was not mediated through p53. Using wound healing, transwell migration and invasion assay, we demonstrated Pdcd4 significantly inhibited ovarian cancer cell migration and invasion. In conclusion, loss of Pdcd4 was a common abnormality at molecular level in ovarian cancer and it might be a potential prognostic factor in ovarian cancer patients. In addition, our results also provided first evidence for the tumor suppressor properties of Pdcd4 in inhibition of cell proliferation by inducing cell cycle arrest and modulating cell cycle regulators, as well as inhibition of cell migration and invasion in ovarian cancer cells. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. 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 5006.