Hoi Yan Chan

Aberrant activation of hedgehog signaling pathway in ovarian cancers: effect on prognosis, cell invasion and differentiation

Abstract Aberrant activation of hedgehog (HH) pathway has been implicated in the development of human malignancies. This study aimed at investigating the role of HH molecules in human ovarian carcinogenesis. The expression profiles of HH molecules were examined in ovarian tumor samples and ovarian cancer cell lines and the in vitro effects of HH molecules on cell proliferation, apoptosis, migration, invasion and cell differentiation as well as related downstream target genes were assessed. Overexpression of Patched and Gli1 protein in ovarian cancers correlated with poor survival of the patients (P = 0.008; P = 0.004). Significantly elevated expression of Sonic hedgehog messenger RNA was observed in ovarian cancers compared with normal tissues and benign ovarian tumors and such differential expression was specific to histological types (P < 0.05). Ectopic Gli1 overexpression in ovarian cancer cells conferred increased cell proliferation, cell mobility, invasiveness and change in differentiation in association with increased expression of E-cadherin, vimentin, Bcl-2, caspases as well as β1 integrin, membrane type 1 matrix metalloproteinase (MT1-MMP) and vascular endothelial growth factor (VEGF). Treatment with 3-keto-N-(aminoethyl-aminocaproyl-dihydrocinnamoyl)-cyclopamine induced cancer cell apoptosis, suppressed cell growth, mobility and invasiveness and induced cancer cell dedifferentiation with decreased expression of E-cadherin, cytokeratin 7, Snail, calretinin, vimentin, Bcl-2, caspases, β1 integrin, MT1-MMP and VEGF. Our data suggested that abnormal HH signaling activation plays important roles in the development and progression of ovarian cancers. Gli1 expression is an independent prognostic marker. Inhibition of the HH pathway molecules might be a valid therapeutic strategy for ovarian cancers.

p21-activated kinase 4 regulates ovarian cancer cell proliferation, migration, and invasion and contributes to poor prognosis in patients

Ovarian cancer is a lethal gynecological malignancy, and to improve survival, it is important to identify novel prognostic and therapeutic targets. In this study, we present a role for p21-activated kinase 4 (Pak4) in ovarian cancer progression. We show a significant association between increased expression of Pak4 and its activated form, phosphorylated (p)-Pak4 Ser474, with metastasis of ovarian cancers, shorter overall and disease-free survival, advanced stage and high-grade cancers, serous/clear cell histological subtypes, and reduced chemosensitivity. Pak4 overexpression was also observed in ovarian cancer cell lines. Pak4 and p-Pak4 expression were detected both in the nucleus and cytoplasm of ovarian cancer cells, in vitro as well as in vivo. Stable knockdown of Pak4 in ovarian cancer cell lines led to reduced cell migration, invasion, and proliferation, along with reduced c-Src, ERK1/2, and epidermal growth factor receptor (EGFR) activation and decreased matrix metalloproteinase 2 (MMP2) expression. Conversely, Pak4 overexpression promoted ovarian cancer cell migration and invasion in a c-Src, MEK-1, MMP2, and kinase-dependent manner, and induced cell proliferation through the Pak4/c-Src/EGFR pathway that controls cyclin D1 and CDC25A expression. Stable knockdown of Pak4 also impeded tumor growth and dissemination in nude mice. This report reveals the association between Pak4 and important clinicopathologic parameters, suggesting Pak4 to be a significant prognostic marker and potential therapeutic molecular target in ovarian cancer. The implied possible cross-talk between Pak4 and EGFR suggests the potential of dual targeting of EGFR and Pak4 as a unique therapeutic approach for cancer therapy.

Stem cell transcription factor NANOG controls cell migration and invasion via dysregulation of E-cadherin and FoxJ1 and contributes to adverse clinical outcome in ovarian cancers

Ovarian cancer is the most lethal of all gynecological malignancies, and the identification of novel prognostic and therapeutic targets for ovarian cancer is crucial. It is believed that only a small subset of cancer cells are endowed with stem cell properties, which are responsible for tumor growth, metastatic progression and recurrence. NANOG is one of the key transcription factors essential for maintaining self-renewal and pluripotency in stem cells. This study investigated the role of NANOG in ovarian carcinogenesis and showed overexpression of NANOG mRNA and protein in the nucleus of ovarian cancers compared with benign ovarian lesions. Increased nuclear NANOG expression was significantly associated with high-grade cancers, serous histological subtypes, reduced chemosensitivity, and poor overall and disease-free survival. Further analysis showed NANOG is an independent prognostic factor for overall and disease-free survival. Moreover, NANOG was highly expressed in ovarian cancer cell lines with metastasis-associated property and in clinical samples of metastatic foci. Stable knockdown of NANOG impeded ovarian cancer cell proliferation, migration and invasion, which was accompanied by an increase in mRNA expression of E-cadherin, caveolin-1, FOXO1, FOXO3a, FOXJ1 and FOXB1. Conversely, ectopic NANOG overexpression enhanced ovarian cancer cell migration and invasion along with decreased E-cadherin, caveolin-1, FOXO1, FOXO3a, FOXJ1 and FOXB1 mRNA expression. Importantly, we found Nanog-mediated cell migration and invasion involved its regulation of E-cadherin and FOXJ1. This is the first report revealing the association between NANOG expression and clinical outcome of patients with ovarian cancers, suggesting NANOG to be a potential prognostic marker and therapeutic molecular target in ovarian cancer.

Overexpression of NANOG in gestational trophoblastic diseases: Effect on apoptosis, cell invasion, and clinical outcome

Gestational trophoblastic disease includes choriocarcinoma, a frankly malignant tumor, and hydatidiform mole (HM), which often leads to the development of persistent gestational trophoblastic neoplasia and requires chemotherapy. NANOG is an important transcription factor that is crucial for maintaining embryonic stem cell self-renewal and pluripotency. We postulated that NANOG is involved in the pathogenesis of gestational trophoblastic disease. In this study, significantly higher NANOG mRNA and protein expression levels, by quantitative PCR and immunoblotting, respectively, were demonstrated in HMs, particularly those that developed persistent disease, when compared with normal placentas. In addition, significantly increased nuclear NANOG immunoreactivity was found by immunohistochemistry in HMs (P < 0.001) and choriocarcinoma (P = 0.002). Higher NANOG expression levels were demonstrated in HMs that developed persistent disease, as compared with those that regressed (P = 0.025). Nuclear localization of NANOG was confirmed by confocal microscopy and immunoblotting in choriocarcinoma cell lines. There was a significant inverse correlation between NANOG immunoreactivity and apoptotic index assessed by M30 CytoDeath antibody (P = 0.012). After stable knockdown of NANOG in the choriocarcinoma cell line JEG-3 by an shRNA approach, increased apoptosis was observed in relation to with enhanced caspases and poly(ADP-ribose) polymerase activities. NANOG knockdown was also associated with decreased mobility and invasion of JEG-3 and down-regulation of matrix metalloproteases 2 and 9. These findings suggest that NANOG is involved in the pathogenesis and clinical progress of gestational trophoblastic disease, likely through its effect on apoptosis, cell migration, and invasion.

Differential expression and phosphorylation of Pak1 and Pak2 in ovarian cancer: effects on prognosis and cell invasion

Ovarian cancer is a gynecological malignancy with high mortality. Therefore, the identification of novel prognostic and therapeutic targets is important. p21‐activated kinases (Paks) are involved in cytoskeleton reorganization. This study investigated the clinical significance of total and phosphorylated (p) Pak1 and Pak2 as well as their functional roles in ovarian cancer. Expressions of Pak1, p‐Pak1 Thr212, Pak2 and p‐Pak2 Ser20 in ovarian normal and cancerous cell lines as well as in clinical samples of ovarian tumors were evaluated. The effects of Pak1 and Pak2 on ovarian cancer cell functions were determined. Pak1, p‐Pak1 and p‐Pak2 were overexpressed in ovarian cancer cell lines, and clinical samples of ovarian cancers were compared with benign ovarian lesions/inclusion cysts. Similar Pak2 expression levels were observed among normal and cancerous cell lines and clinical samples. After multiple testing correction, high Pak1 and nuclear p‐Pak1 expression in ovarian cancers was significantly associated with histological type and tumor grade, respectively. Pak1 and p‐Pak1 expression was associated with poor overall and disease‐free survival. Pak1 was an independent prognostic factor. Knockdown of Pak1 and Pak2 in ovarian cancer cell lines reduced cell migration and invasion but did not affect cell proliferation and apoptosis. Knockdown of Pak1 also reduced p38 activation and downregulated vascular endothelial growth factor. Conversely, ectopic Pak1 overexpression enhanced ovarian cancer cell migration and invasion in a kinase‐dependent manner, along with increased p38 activation. Our findings suggest that Pak1, p‐Pak1 and p‐Pak2 play important roles in ovarian carcinogenesis. Pak1 and p‐Pak1 may be potential prognostic markers and therapeutic molecular targets in ovarian cancer.

iASPP and Chemoresistance in Ovarian Cancers: Effects on Paclitaxel-Mediated Mitotic Catastrophe

Purpose: iASPP is a specific regulator of p53-mediated apoptosis. Herein, we provided the first report on the expression profile of iASPP in ovarian epithelial tumor and its effect on paclitaxel chemosensitivity. Experimental Design: Expression and amplification status of iASPP was examined in 203 clinical samples and 17 cell lines using immunohistochemistry, quantitative real-time PCR, and immunoblotting, and correlated with clinicopathologic parameters. Changes in proliferation, mitotic catastrophe, apoptosis, and underlying mechanism in ovarian cancer cells of different p53 status following paclitaxel exposure were also analyzed. Results: The protein and mRNA expression of iASPP was found to be significantly increased in ovarian cancer samples and cell lines. High iASPP expression was significantly associated with clear cell carcinoma subtype (P = 0.003), carboplatin and paclitaxel chemoresistance (P = 0.04), shorter overall (P = 0.003), and disease-free (P = 0.001) survival. Multivariate analysis confirmed iASPP expression as an independent prognostic factor. Increased iASPP mRNA expression was significantly correlated with gene amplification (P = 0.023). iASPP overexpression in ovarian cancer cells conferred resistance to paclitaxel by reducing mitotic catastrophe in a p53-independent manner via activation of separase, whereas knockdown of iASPP enhanced paclitaxel-mediated mitotic catastrophe through inactivating separase. Both securin and cyclin B1/CDK1 complex were involved in regulating separase by iASPP. Conversely, overexpressed iASPP inhibited apoptosis in a p53-dependent mode. Conclusions: Our data show an association of iASPP overexpression with gene amplification in ovarian cancer and suggest a role of iASPP in poor patient outcome and chemoresistance, through blocking mitotic catastrophe. iASPP should be explored further as a potential prognostic marker and target for chemotherapy. Clin Cancer Res; 17(21); 6924–33. ©2011 AACR.

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.

Paradoxical impact of two folate receptors, FRα and RFC, in ovarian cancer: effect on cell proliferation, invasion and clinical outcome.

Despite being an essential vitamin, folate has been implicated to enhance tumor growth, as evidenced by reports on overexpression of folate receptor alpha (FRα) in carcinomas. The role of another folate transporter, reduced folate carrier (RFC), is largely unknown. This study investigated the roles of folate, FRα and RFC in ovarian cancers. We demonstrated FRα mRNA and protein overexpression and reduced RFC expression in association with FRα gene amplification and RFC promoter hypermethylation, respectively. FRα overexpression was associated with tumor progression while RFC expression incurred a favorable clinical outcome. Such reciprocal expression pattern was also observed in ovarian cancer cell lines. Folate was shown to promote cancer cell proliferation, migration and invasion in vitro, and down-regulate E-cadherin expression. This effect was blocked after either stable knockdown of FRα or ectopic overexpression of RFC. This hitherto unreported phenomenon suggests that, RFC can serve as a balancing partner of FRα and confer a protective effect in patients with high FRα-expressing ovarian carcinomas, as evidenced by their prolonged overall and disease-free survivals. In conclusion, we report on the paradoxical impact of FRα (putative oncogenic) and RFC (putative tumor suppressive) in human malignancies. FRα and RFC may potentially be explored as therapeutic target or prognostic marker respectively. We recommend caution and additional research on folate supplements in cancer patients.

Activated Stat3 expression in gestational trophoblastic disease: correlation with clinicopathological parameters and apoptotic indices

Aims:u2002 To assess the expression profile of the activated form of signal transducer and activator of transcription (Stat)3 in gestational trophoblastic disease (GTD) and correlate the findings with clinicopathological parameters.

Overexpression of dedicator of cytokinesis I (Dock180) in ovarian cancer correlated with aggressive phenotype and poor patient survival

Zhao F, Siu M K Y, Jiang L L, Tam K F, Ngan H Y S, Le X‐F, Wong O G W, Wong E S Y, Chan H Y & Cheung A N Y u2028(2011) Histopathology 59, 1163–1172 u2028Overexpression of dedicator of cytokinesis I (Dock180) in ovarian cancer correlated with aggressive phenotype and poor patient survival