Philippa M. O'Brien

Dual-specificity phosphatases: critical regulators with diverse cellular targets

DUSPs (dual-specificity phosphatases) are a heterogeneous group of protein phosphatases that can dephosphorylate both phosphotyrosine and phosphoserine/phosphothreonine residues within the one substrate. DUSPs have been implicated as major modulators of critical signalling pathways that are dysregulated in various diseases. DUSPs can be divided into six subgroups on the basis of sequence similarity that include slingshots, PRLs (phosphatases of regenerating liver), Cdc14 phosphatases (Cdc is cell division cycle), PTENs (phosphatase and tensin homologues deleted on chromosome 10), myotubularins, MKPs (mitogen-activated protein kinase phosphatases) and atypical DUSPs. Of these subgroups, a great deal of research has focused on the characterization of the MKPs. As their name suggests, MKPs dephosphorylate MAPK (mitogen-activated protein kinase) proteins ERK (extracellular-signal-regulated kinase), JNK (c-Jun N-terminal kinase) and p38 with specificity distinct from that of individual MKP proteins. Atypical DUSPs are mostly of low-molecular-mass and lack the N-terminal CH2 (Cdc25 homology 2) domain common to MKPs. The discovery of most atypical DUSPs has occurred in the last 6 years, which has initiated a large amount of interest in their role and regulation. In the past, atypical DUSPs have generally been grouped together with the MKPs and characterized for their role in MAPK signalling cascades. Indeed, some have been shown to dephosphorylate MAPKs. The current literature hints at the potential of the atypical DUSPs as important signalling regulators, but is crowded with conflicting reports. The present review provides an overview of the DUSP family before focusing on atypical DUSPs, emerging as a group of proteins with vastly diverse substrate specificity and function.

DNA methylation changes in ovarian cancer: Implications for early diagnosis, prognosis and treatment

OBJECTIVE To review epigenetic changes identified in ovarian cancer, focusing on their potential as clinical markers for detection, monitoring of disease progression and as markers of therapeutic response. METHODS A comprehensive review of English language scientific literature on the topics of methylation and ovarian cancer was conducted. RESULTS Genome-wide demethylation of normally methylated and silenced chromosomal regions, and hypermethylation and silencing of genes including tumor suppressors are common features of cancer cells. Epigenetic alterations, including CpG island DNA methylation, occur in ovarian cancer and the identification of specific genes that are altered by epigenetic events is an area of intense research. Aberrant DNA methylation in ovarian cancer is observed in early cancer development, can be detected in DNA circulating in the blood and hence provides the promise of a non-invasive cancer detection test. In addition, identification of ovarian cancer-specific epigenetic changes has promise in molecular classification and disease stratification. CONCLUSIONS The detection of cancer-specific DNA methylation changes heralds an exciting new era in cancer diagnosis as well as evaluation of prognosis and therapeutic responsiveness and warrants further investigation.

Cyclin D1, p53, and p21Waf1/Cip1 Expression Is Predictive of Poor Clinical Outcome in Serous Epithelial Ovarian Cancer

Purpose: Dysregulation of cell cycle control, in particular G1-S-phase transition, is implicated in the pathogenesis of most human cancers, including epithelial ovarian cancer (EOC). However, the prognostic significance of aberrant cell cycle gene expression in EOC remains unclear. Experimental Design: The expression of selected genes from the pRb pathway that regulates G1-S-phase progression, including cyclin D1, p16Ink4a, cyclin E, p27Kip1, p21Waf1/Cip1, and p53, was examined in a consecutive series of 134 serous EOC using immunohistochemistry and the results correlated to disease outcome. Results: Molecular markers predictive of reduced overall survival in univariate analysis were overexpression of cyclin D1 (P = 0.03) and p53 (P = 0.03) and reduced expression of p27Kip1 (P = 0.05) and p21Waf1/Cip1 (P = 0.02), with the latter three also being prognostic for a shorter progression-free interval. In addition, patients displaying overexpression of p53 with concurrent loss of p21Waf1/Cip1 had a significantly shorter overall (P = 0.0008) and progression-free survival (P = 0.0001). On multivariate analysis, overexpression of cyclin D1 and combined loss of p21Waf1/Cip1 in the presence of p53 overexpression were independent predictors of overall survival. Similarly, the combination of p21Waf1/Cip1 loss and p53 overexpression was independently predictive of a shorter progression-free interval. Overexpression of p53 and cyclin E and reduced expression of p27Kip1 and p21Waf1/Cip1 were significantly associated with increasing tumor grade. Conclusions: This study confirms that dysregulation of cell cycle genes is common in EOC, and that aberrant expression of critical cell cycle regulatory proteins can predict patient outcome in serous EOC.

A distinct molecular profile associated with mucinous epithelial ovarian cancer.

Mucinous epithelial ovarian cancers (MOC) are clinically and morphologically distinct from the other histological subtypes of ovarian cancer. To determine the genetic basis of MOC and to identify potential tumour markers, gene expression profiling of 49 primary ovarian cancers of different histological subtypes was performed using a customised oligonucleotide microarray containing >59 000 probesets. The results show that MOC express a genetic profile that both differs and overlaps with other subtypes of epithelial ovarian cancer. Concordant with its histological phenotype, MOC express genes characteristic of mucinous carcinomas of varying epithelial origin, including intestinal carcinomas. Differences in gene expression between MOC and other histological subtypes of ovarian cancer were confirmed by RT–PCR and/or immunohistochemistry. In particular, galectin 4 (LGALS4) was highly and specifically expressed in MOC, but expressed at lower levels in benign mucinous cysts and borderline (atypical proliferative) tumours, supporting a malignant progression model of MOC. Hence LGALS4 may have application as an early and differential diagnostic marker of MOC.

Prognostic and diagnostic significance of DNA methylation patterns in high grade serous ovarian cancer

OBJECTIVE Altered DNA methylation patterns hold promise as cancer biomarkers. In this study we selected a panel of genes which are commonly methylated in a variety of cancers to evaluate their potential application as biomarkers for prognosis and diagnosis in high grade serous ovarian carcinoma (HGSOC); the most common and lethal subtype of ovarian cancer. METHODS The methylation patterns of 10 genes (BRCA1, EN1, DLEC1, HOXA9, RASSF1A, GATA4, GATA5, HSULF1, CDH1, SFN) were examined and compared in a cohort of 80 primary HGSOC and 12 benign ovarian surface epithelium (OSE) samples using methylation-specific headloop suppression PCR. RESULTS The genes were variably methylated in primary HGSOC, with HOXA9 methylation observed in 95% of cases. Most genes were rarely methylated in benign OSE, with the exception of SFN which was methylated in all HGSOC and benign OSE samples examined. Methylation of DLEC1 was associated with disease recurrence, independent of tumor stage and suboptimal surgical debulking (HR 3.5 (95% CI:1.10-11.07), p=0.033). A combination of the methylation status of HOXA9 and EN1 could discriminate HGSOC from benign OSE with a sensitivity of 98.8% and a specificity of 91.7%, which increased to 100% sensitivity with no loss of specificity when pre-operative CA125 levels were also incorporated. CONCLUSIONS This study provides further evidence to support the feasibility of detecting altered DNA methylation patterns as a potential diagnostic and prognostic approach for HGSOC.

The E3 ubiquitin ligase EDD is an adverse prognostic factor for serous epithelial ovarian cancer and modulates cisplatin resistance in vitro.

Despite a high initial response rate to first-line platinum/paclitaxel chemotherapy, most women with epithelial ovarian cancer relapse with recurrent disease that becomes refractory to further cytotoxic treatment. We have previously shown that the E3 ubiquitin ligase, EDD, a regulator of DNA damage responses, is amplified and overexpressed in serous ovarian carcinoma. Given that DNA damage pathways are linked to platinum resistance, the aim of this study was to determine if EDD expression was associated with disease recurrence and platinum sensitivity in serous ovarian cancer. High nuclear EDD expression, as determined by immunohistochemistry in a cohort of 151 women with serous ovarian carcinoma, was associated with an approximately two-fold increased risk of disease recurrence and death in patients who initially responded to first-line chemotherapy, independently of disease stage and suboptimal debulking. Although EDD expression was not directly correlated with relative cisplatin sensitivity of ovarian cancer cell lines, sensitivity to cisplatin was partially restored in platinum-resistant A2780-cp70 ovarian cancer cells following siRNA-mediated knockdown of EDD expression. These results identify EDD as a new independent prognostic marker for outcome in serous ovarian cancer, and suggest that pathways involving EDD, including DNA damage responses, may represent new therapeutic targets for chemoresistant ovarian cancer.

Expression of urokinase plasminogen activator and its receptor in advanced epithelial ovarian cancer patients

BACKGROUND The urokinase plasminogen activator (uPA) system has been implicated in progression and poor prognosis in epithelial ovarian cancer (EOC) patients. The present study investigated the distribution of uPA and its receptor (uPAR) in EOC cell lines, primary and metastatic tumors, and the relationship between uPA/uPAR and matrix metalloproteinase (MMP) expression using immunohistochemistry. We also studied the association between uPA/uPAR expression and clinical and pathological parameters including disease progression free survival (PFS). METHODS The expression of uPA/uPAR was examined on paraffin-embedded tissue sections from primary EOC (n=100), and matched metastatic lesions (n=30) of untreated patients, normal ovarian tissues (n=20) as well as 8 primary and metastatic EOC cell lines by immunohistochemistry. Co-immunolabeling of uPA and MMP-1, -2, -9 or MT1-MMP was examined using confocal microscopy. RESULTS The expression of uPA/uPAR was found in most primary (92% and 88% positive, respectively), metastatic ovarian tumors (93% and 90% positive, respectively), and all of examined EOC cell lines. The majority of specimens showed moderate to strong immunostaining of tumor and stromal cells; for primary specimens, this was significantly associated with tumor stage, grade and time to relapse (P<0.01). Overexpression of uPA/uPAR was found to be associated with an unfavorable prognosis with significantly reduced median disease PFS of 16 vs. 33 months for uPA (P<0.001), and 15 vs. 28 months for uPAR (P<0.001). Co-localization of uPA with MMP-1, -2, -9 or MT1-MMP was also seen in primary tumors and metastatic lesions. CONCLUSIONS The expression of uPA/uPAR was associated with EOC progression. uPA/uPAR are useful markers for EOC prognosis and could be promising therapeutic targets for treating incurable, recurrent EOC.

MAL2 and tumor protein D52 (TPD52) are frequently overexpressed in ovarian carcinoma, but differentially associated with histological subtype and patient outcome

BackgroundThe four-transmembrane MAL2 protein is frequently overexpressed in breast carcinoma, and MAL2 overexpression is associated with gain of the corresponding locus at chromosome 8q24.12. Independent expression microarray studies predict MAL2 overexpression in ovarian carcinoma, but these had remained unconfirmed. MAL2 binds tumor protein D52 (TPD52), which is frequently overexpressed in ovarian carcinoma, but the clinical significance of MAL2 and TPD52 overexpression was unknown.MethodsImmunohistochemical analyses of MAL2 and TPD52 expression were performed using tissue microarray sections including benign, borderline and malignant epithelial ovarian tumours. Inmmunohistochemical staining intensity and distribution was assessed both visually and digitally.ResultsMAL2 and TPD52 were significantly overexpressed in high-grade serous carcinomas compared with serous borderline tumours. MAL2 expression was highest in serous carcinomas relative to other histological subtypes, whereas TPD52 expression was highest in clear cell carcinomas. MAL2 expression was not related to patient survival, however high-level TPD52 staining was significantly associated with improved overall survival in patients with stage III serous ovarian carcinoma (log-rank test, p < 0.001; n = 124) and was an independent predictor of survival in the overall carcinoma cohort (hazard ratio (HR), 0.498; 95% confidence interval (CI), 0.34-0.728; p < 0.001; n = 221), and in serous carcinomas (HR, 0.440; 95% CI, 0.294-0.658; p < 0.001; n = 182).ConclusionsMAL2 is frequently overexpressed in ovarian carcinoma, and TPD52 overexpression is a favourable independent prognostic marker of potential value in the management of ovarian carcinoma patients.

Collagen and calcium-binding EGF domains 1 is frequently inactivated in ovarian cancer by aberrant promoter hypermethylation and modulates cell migration and survival

Background:Collagen and calcium-binding EGF domains 1 (CCBE1) is an uncharacterised gene that has down-regulated expression in breast cancer. As CCBE1 maps to 18q21.32, a region frequently exhibiting loss of heterozygosity in ovarian cancer, the aim of this study was to determine the expression and function of CCBE1 in ovarian cancer.Methods:Expression and methylation patterns of CCBE1 were determined in ovarian cancer cell lines and primary tumours. CCBE1 contains collagen repeats and an aspartic acid/asparagine hydroxylation/EGF-like domain, suggesting a function in extracellular matrix remodelling and migration, which was determined using small-interfering RNA (siRNA)-mediated knockdown and over-expression of CCBE1 in cell lines.Results:CCBE1 is expressed in normal ovary, but is reduced in ovarian cancer cell lines and primary carcinomas. Pharmacological demethylation/deacetylation in ovarian cancer cell lines re-induced CCBE1 expression, indicating that epigenetic mechanisms contribute to its silencing in cancer. CCBE1 promoter hypermethylation was detected in 6/11 (55%) ovarian cancer cell lines and 38/81 (41%) ovarian carcinomas. siRNA-mediated knockdown of CCBE1 in ovarian cancer cell lines enhanced their migration; conversely, re-expression of CCBE1 reduced migration and survival. Hence, loss of CCBE1 expression may promote ovarian carcinogenesis by enhancing migration and cell survival.Conclusions:These data suggest that CCBE1 is a new candidate tumour suppressor in ovarian cancer.

Low meprin alpha expression differentiates primary ovarian mucinous carcinoma from gastrointestinal cancers that commonly metastasise to the ovaries.

Background: Currently, no specific immunohistochemical markers are available to differentiate primary mucinous epithelial ovarian cancer (MOC) from adenocarcinomas originating at other sites that have metastasised to the ovary, which may have an impact on patient management and prognosis. Aim: To investigate the expression of two intestinal markers, galectin 4 and meprin α, in mucinous carcinomas of the ovary and gastrointestinal tract. Methods: Using immunohistochemical analysis, the expression of galectin 4 and meprin α was investigated in 10 MOCs and in 38 mucinous adenocarcinomas of colon, pancreas, stomach and appendix, the most common sites of origin of ovarian metastases. Results: Total cytoplasmic galectin 4 expression was relatively consistent between the different carcinomas. Membranous meprin α expression was significantly lower in MOCs compared with gastrointestinal carcinomas. Moreover, meprin α expression showed greater discrimination between the ovarian and gastrointestinal carcinomas than the cytokeratins CK7 and CK20, the current standard immunohistochemical markers used to determine the tissue origin of mucinous carcinomas involving the ovaries. Conclusions: Meprin α is a useful additional marker in differentiating primary from secondary mucinous adenocarcinomas of the ovary.