Expression and potential role of Fas-associated phosphatase-1 in ovarian cancer

Oncolytic virotherapy with human telomerase reverse transcriptase promoter regulation enhances cytotoxic effects against gastric cancer

Currently, gastric cancer is the third most common cause of cancer-associated mortality worldwide. Oncolytic virotherapy using herpes simplex virus (HSV) has emerged as a novel therapeutic strategy against cancer. Telomerase is activated in >90of malignant tumors, including gastric cancer, and human telomerase reverse transcriptase (hTERT) is one of the major components of telomerase enzyme. Therefore, in oncolytic HSV, placing the essential genes under the regulation of the hTERT promoter may enhance its antitumor efficacy. The present study examined the antitumor effect of fourth-generation oncolytic HSVs, which contain the ICP6 gene under the regulation of the hTERT promoter (T-hTERT). To examine the association between hTERT expression and prognosis in patients with gastric cancer, immunohistochemical analysis of resected tumor specimens was performed. The enhanced efficacy of T-hTERT was determined in human gastric cancer cell lines in vitro and in human gastric adenocarcinoma specimens in vivo. In in vitro experiments, enhanced cytotoxicity of T-hTERT was observed in MKN1, MKN28 and MKN45 cells compared with that of a third-generation oncolytic HSV, T-null. In particular, the cytotoxicity of T-hTERT was markedly enhanced in MKN45 cells. Furthermore, in vivo experiments demonstrated that 36.7 and 54.9% of cells were found to be lysed 48 h after infection with T-null or T-hTERT viruses at 0.01 pfu/cell, respectively. The T-hTERT-treated group exhibited considerably lower cell viability than the control [phosphate-buffered saline (-)] group. Therefore, employing oncolytic HSVs that contain the ICP6 gene under the regulation of the hTERT promoter may be an effective therapeutic strategy for gastric cancer. To the best of our knowledge, the present study was the first to describe the effect of an oncolytic HSV with ICP6 expression regulated by the hTERT promoter on gastric cancer cells.

Dual Role of the PTPN13 Tyrosine Phosphatase in Cancer

In this review article, we present the current knowledge on PTPN13, a class I non-receptor protein tyrosine phosphatase identified in 1994. We focus particularly on its role in cancer, where PTPN13 acts as an oncogenic protein and also a tumor suppressor. To try to understand these apparent contradictory functions, we discuss PTPN13 implication in the FAS and oncogenic tyrosine kinase signaling pathways and in the associated biological activities, as well as its post-transcriptional and epigenetic regulation. Then, we describe PTPN13 clinical significance as a prognostic marker in different cancer types and its impact on anti-cancer treatment sensitivity. Finally, we present future research axes following recent findings on its role in cell junction regulation that implicate PTPN13 in cell death and cell migration, two major hallmarks of tumor formation and progression.

PTPN13 induces cell junction stabilization and inhibits mammary tumor invasiveness

Clinical data suggest that the protein tyrosine phosphatase PTPN13 exerts an anti-oncogenic effect. Its exact role in tumorigenesis remains, however, unclear due to its negative impact on FAS receptor-induced apoptosis.

Methods: We crossed transgenic mice deleted for PTPN13 phosphatase activity with mice that overexpress human HER2 to assess the exact role of PTPN13 in tumor development and aggressiveness. To determine the molecular mechanism underlying the PTPN13 tumor suppressor activity we developed isogenic clones of the aggressive human breast cancer cell line MDA-MB-231 overexpressing either wild type or a catalytically-inactive mutant PTPN13 and subjected these to phosphoproteomic and gene ontology analyses.

We investigated the PTPN13 consequences on cell aggressiveness using wound healing and Boyden chamber assays, on intercellular adhesion using videomicroscopy, cell aggregation assay and immunofluorescence.

Results: The development, growth and invasiveness of breast tumors were strongly increased by deletion of the PTPN13 phosphatase activity in transgenic mice. We observed that PTPN13 phosphatase activity is required to inhibit cell motility and invasion in the MDA-MB-231 cell line overexpressing PTPN13. In vivo, the negative PTPN13 effect on tumor invasiveness was associated with a mesenchymal-to-epithelial transition phenotype in athymic mice xenografted with PTPN13-overexpressing MDA-MB-231 cells, as well as in HER2-overexpressing mice with wild type PTPN13, compared to HER2-overexpressing mice that lack PTPN13 phosphatase activity. Phosphoproteomic and gene ontology analyses indicated a role of PTPN13 in the regulation of intercellular junction-related proteins. Finally, protein localization studies in MDA-MB-231 cells and HER2-overexpressing mice tumors confirmed that PTPN13 stabilizes intercellular adhesion and promotes desmosome formation.

Conclusions: These data provide the first evidence for the negative role of PTPN13 in breast tumor invasiveness and highlight its involvement in cell junction stabilization.

Polyubiquitination of p62/SQSTM1 is a prerequisite for Fas/CD95 aggregation to promote caspase-dependent apoptosis in cadmium-exposed mouse monocyte RAW264.7 cells

Cadmium(Cd) induces cytotoxicity via autophagy-induced apoptosis in non-activated mouse monocytes; however, the molecular mechanism remains unclear. Here, we show that autophagy induces Fas (CD95/APO-1)-mediated apoptosis by promoting accumulation of p62/SQSTM1 in response to Cd. Cd produced tumor necrosis factor (TNF)-α, peaking at 6 h, and exhibiting a concentration-dependent increase. Immunoblot analysis revealed polyubiquitinated (polyUb) full-length Fas (antibody clone G-9) and reduced cytosolic Fas (antibody clone M-20) in Cd-exposed RAW264.7 cells. The accumulation of polyUb-Fas was transient and positively correlated with polyUb-p62 and polyUb-proteins. Autophagy inhibition via chemical and genetic modulation suppressed Cd-induced polyUb-p62, polyUb-Fas, and polyUb-protein levels, whereas the level of cytosolic Fas recovered to that of the control. Immunofluorescence (IF) staining for full-length Fas, p62, and ubiquitin revealed an aggregated pattern in Cd-induced apoptotic cells, which was inhibited by blocking autophagy. Fas colocalized with microtubule-associated protein 1 light chain (LC)-3B. IF staining and immunoprecipitation assays revealed colocalization and interaction among p62, Ub, and Fas. Knockdown of p62 reduced the binding of Ub and Fas. Together, these data suggest that polyUb-p62 targets Fas and recruits it to autophagosomes, where Fas transiently aggregates to promote apoptosis and is degraded with polyUb-p62. In conclusion, autophagy regulates C-terminal cytosolic Fas aggregation via p62 polyubiquitination, which is required for apoptosis and may play a critical role in the production of select cytokines.

Apoptotic signalling targets the post-endocytic sorting machinery of the death receptor Fas/CD95

Fas plays a major role in regulating ligand-induced apoptosis in many cell types. It is well known that several cancers demonstrate reduced cell surface levels of Fas and thus escape a potential control system via ligand-induced apoptosis, although underlying mechanisms are unclear. Here we report that the endosome associated trafficking regulator 1 (ENTR1), controls cell surface levels of Fas and Fas-mediated apoptotic signalling. ENTR1 regulates, via binding to the coiled coil domain protein Dysbindin, the delivery of Fas from endosomes to lysosomes thereby controlling termination of Fas signal transduction. We demonstrate that ENTR1 is cleaved during Fas-induced apoptosis in a caspase-dependent manner revealing an unexpected interplay of apoptotic signalling and regulation of endolysosomal trafficking resulting in a positive feedback signalling-loop. Our data provide insights into the molecular mechanism of Fas post-endocytic trafficking and signalling, opening possible explanations on how cancer cells regulate cell surface levels of death receptors.

Fas is a death receptor that regulates apoptosis in many cell types and is downregulated on the cell surface in many cancers. Here, Sharma et al. show that endosome associated trafficking regulator ENTR1 regulates delivery of Fas to lysosomes, thereby controlling its degradation and signalling.

Protein tyrosine phosphatases: promising targets in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. It is the fourth leading cause of cancer-related death and is associated with a very poor prognosis. KRAS driver mutations occur in approximately 95% of PDAC cases and cause the activation of several signaling pathways such as mitogen-activated protein kinase (MAPK) pathways. Regulation of these signaling pathways is orchestrated by feedback loops mediated by the balance between protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), leading to activation or inhibition of its downstream targets. The human PTPome comprises 125 members, and these proteins are classified into three distinct families according to their structure. Since PTP activity description, it has become clear that they have both inhibitory and stimulatory effects on cancer-associated signaling processes and that deregulation of PTP function is closely associated with tumorigenesis. Several PTPs have displayed either tumor suppressor or oncogenic characteristics during the development and progression of PDAC. In this sense, PTPs have been presented as promising candidates for the treatment of human pancreatic cancer, and many PTP inhibitors have been developed since these proteins were first associated with cancer. Nevertheless, some challenges persist regarding the development of effective and safe methods to target these molecules and deliver these drugs. In this review, we discuss the role of PTPs in tumorigenesis as tumor suppressor and oncogenic proteins. We have focused on the differential expression of these proteins in PDAC, as well as their clinical implications and possible targeting for pharmacological inhibition in cancer therapy.

Protein tyrosine phosphatase L1 inhibits high-grade serous ovarian carcinoma progression by targeting IκBα

Background

High-grade serous ovarian cancer (HGSOC) represents most of the ovarian cancers and accounts for 70%-80 % of related deaths. The overall survival of HGSOC has not been remarkably improved in the past decades, due to the tumor dissemination in peritoneal cavity and invasion of adjacent organs. Therefore, identifying molecular biomarkers is invaluable in helping predicting clinical outcomes and developing targeted chemotherapies. Although there have been studies revealing the prognostic significance of protein tyrosine phosphatase L1 (PTPL1) in breast cancer and lung cancer, its involvement and functions in HGSOC remains to be elucidated.

Methods

We retrospectively enrolled a cohort of HGSOC patients after surgical resection. And analyzed the mRNA and protein levels of PTPL1 in tissue samples.

Results

We found that PTPL1 presented a lower expression in HGSOC tissues than in adjacent normal ovarian tissues. Besides, the PTPL1 level was negatively correlated with tumor stage, implying its potential role as a tumor suppressor. Univariate and multivariate analyses identified that patients with higher PTPL1 showed a better overall survival compared to those with lower PTPL1 expression. In addition, cellular experiments confirmed the role of PTPL1 in suppressing tumor proliferation and invasion. Furthermore, we demonstrated that PTPL1 negatively regulated phosphorylation of tyrosine 42 on IκBα (IκBα-pY42). To our knowledge, this is the initial finding on PTPL1 targeting IκBα-pY42 site. Finally, our data indicated that PTPL1 suppressed tumor progression by dephosphorylating IκBα-pY42, which stabilized IκBα and attenuated nucleus translocation of NF-κB.

Conclusion

Our study revealed a tumor-suppressing role of PTPL1 in HGSOC by targeting IκBα.

High PTPN13 expression in high grade serous ovarian carcinoma is associated with a better patient outcome

Background

Chromosome 4q loss of heterozygosity (LOH) is frequently observed in high-grade serous ovarian carcinoma (HGSOC). However, this LOH has not been clearly associated with the inactivation of any tumor suppressor gene(s). As the tumor suppressor gene PTPN13 is located on chromosome 4q21, we investigated its expression in HGSOC.

Methods

PTPN13 protein expression was investigated by immunohistochemistry (IHC) in normal ovary epithelium and in 30 HGSOC samples, whereas PTPN13 mRNA expression was quantified by RT-PCR in another independent cohort of 28 HGSOC samples. Patients in both cohorts were followed for more than 8.5 years.

Results

PTPN13 protein expression was lower in one third of HGSOC samples compared with normal ovary epithelium. In both cohorts, high PTPN13 expression level (mRNA or protein) in the tumor was associated with favorable outcome and significantly longer survival (HR=0.27; p=0.0087 and HR=0.42; p=0.03, respectively).

Conclusion

This study demonstrates, for the first time, that high PTPN13 expression level is a prognostic indicator of favorable outcome in patients with HGSOC. This finding, in conjunction with our previous mechanistic studies, suggests that PTPN13 loss, possibly by 4q LOH, enhances HGSOC aggressiveness and highlight the interest of studying PTPN13 signaling in HGSOC to identify new potential therapeutic targets.

Stepping out of the shadows: Oncogenic and tumor-promoting protein tyrosine phosphatases

Protein tyrosine phosphorylation is critical for proper function of cells and organisms. Phosphorylation is regulated by the concerted but generically opposing activities of tyrosine kinases (PTKs) and tyrosine phosphatases (PTPs), which ensure its proper regulation, reversibility, and ability to respond to changing physiological situations. Historically, PTKs have been associated mainly with oncogenic and pro-tumorigenic activities, leading to the generalization that protein dephosphorylation is anti-oncogenic and hence that PTPs are tumor-suppressors. In many cases PTPs do suppress tumorigenesis. However, a growing body of evidence indicates that PTPs act as dominant oncogenes and drive cell transformation in a number of contexts, while in others PTPs support transformation that is driven by other oncogenes. This review summarizes the known transforming and tumor-promoting activities of the classical, tyrosine specific PTPs and highlights their potential as drug targets for cancer therapy.

An unsupervised learning approach to find ovarian cancer genes through integration of biological data

Cancer is a disease characterized largely by the accumulation of out-of-control somatic mutations during the lifetime of a patient. Distinguishing driver mutations from passenger mutations has posed a challenge in modern cancer research. With the advanced development of microarray experiments and clinical studies, a large numbers of candidate cancer genes have been extracted and distinguishing informative genes out of them is essential. As a matter of fact, we proposed to find the informative genes for cancer by using mutation data from ovarian cancers in our framework. In our model we utilized the patient gene mutation profile, gene expression data and gene gene interactions network to construct a graphical representation of genes and patients. Markov processes for mutation and patients are triggered separately. After this process, cancer genes are prioritized automatically by examining their scores at their stationary distributions in the eigenvector. Extensive experiments demonstrate that the integration of heterogeneous sources of information is essential in finding important cancer genes.

Fatty acid synthase overexpression: target for therapy and reversal of chemoresistance in ovarian cancer

Background

Fatty acid synthase (FASN) is crucial to de novo long-chain fatty acid synthesis, needed to meet cancer cells’ increased demands for membrane, energy, and protein production.

Methods

We investigated FASN overexpression as a therapeutic and chemosensitization target in ovarian cancer tissue, cell lines, and primary cell cultures. FASN expression at mRNA and protein levels was determined by quantitative real-time polymerase chain reaction and immunoblotting and immunohistochemistry, respectively. FASN inhibition’s impact on cell viability, apoptosis, and fatty acid metabolism was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide assay, cell death detection enzyme-linked immunosorbent assay, immunoblotting, and ¹⁸ F-fluoromethylcholine uptake measurement, respectively.

Results

Relative to that in healthy fallopian tube tissue, tumor tissues had 1.8-fold average FASN protein overexpression; cell lines and primary cultures had 11-fold–100-fold mRNA and protein overexpression. In most samples, the FASN inhibitor cerulenin markedly decreased FASN expression and cell viability and induced apoptosis. Unlike concomitant administration, sequential cerulenin/cisplatin treatment reduced cisplatin’s half maximal inhibitory concentration profoundly (up to 54%) in a cisplatin-resistant cell line, suggesting platinum (re)sensitization. Cisplatin-resistant cells displayed lower ¹⁸ F-fluoro-methylcholine uptake than did cisplatin-sensitive cells, suggesting that metabolic imaging might help guide therapy.

Conclusions

FASN inhibition induced apoptosis in chemosensitive and platinum-resistant ovarian cancer cells and may reverse cisplatin resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0511-3) contains supplementary material, which is available to authorized users.

Protein tyrosine phosphatases as potential therapeutic targets

Protein tyrosine phosphorylation is a key regulatory process in virtually all aspects of cellular functions. Dysregulation of protein tyrosine phosphorylation is a major cause of human diseases, such as cancers, diabetes, autoimmune disorders, and neurological diseases. Indeed, protein tyrosine phosphorylation-mediated signaling events offer ample therapeutic targets, and drug discovery efforts to date have brought over two dozen kinase inhibitors to the clinic. Accordingly, protein tyrosine phosphatases (PTPs) are considered next-generation drug targets. For instance, PTP1B is a well-known targets of type 2 diabetes and obesity, and recent studies indicate that it is also a promising target for breast cancer. SHP2 is a bona-fide oncoprotein, mutations of which cause juvenile myelomonocytic leukemia, acute myeloid leukemia, and solid tumors. In addition, LYP is strongly associated with type 1 diabetes and many other autoimmune diseases. This review summarizes recent findings on several highly recognized PTP family drug targets, including PTP1B, Src homology phosphotyrosyl phosphatase 2(SHP2), lymphoid-specific tyrosine phosphatase (LYP), CD45, Fas associated phosphatase-1 (FAP-1), striatal enriched tyrosine phosphatases (STEP), mitogen-activated protein kinase/dual-specificity phosphatase 1 (MKP-1), phosphatases of regenerating liver-1 (PRL), low molecular weight PTPs (LMWPTP), and CDC25. Given that there are over 100 family members, we hope this review will serve as a road map for innovative drug discovery targeting PTPs.

The regulatory roles of phosphatases in cancer

The relevance of potentially reversible post-translational modifications required for controlling cellular processes in cancer is one of the most thriving arenas of cellular and molecular biology. Any alteration in the balanced equilibrium between kinases and phosphatases may result in development and progression of various diseases, including different types of cancer, though phosphatases are relatively under-studied. Loss of phosphatases such as PTEN (phosphatase and tensin homologue deleted on chromosome 10), a known tumour suppressor, across tumour types lends credence to the development of phosphatidylinositol 3-kinase inhibitors alongside the use of phosphatase expression as a biomarker, though phase 3 trial data are lacking. In this review, we give an updated report on phosphatase dysregulation linked to organ-specific malignancies.

Autophagy variation within a cell population determines cell fate through selective degradation of Fap-1

Autophagy regulates cell death both positively and negatively, but the molecular basis for this paradox remains inadequately characterized. We demonstrate here that transient cell-to-cell variations in autophagy can either promote cell death or survival depending on the stimulus and cell type. By separating cells with high and low basal autophagy by flow cytometry, we demonstrate that autophagy determines which cells live or die in response to death receptor activation. We have determined that selective autophagic degradation of the phosphatase Fap-1 promotes Fas apoptosis in Type I cells. Conversely, autophagy inhibits apoptosis in Type II cells or upon treatment with TRAIL in either Type I or II cells. These data illustrate that differences in autophagy in a cell population determine cell fate in a stimulus- and cell type-specific manner. This example of selective autophagy of an apoptosis regulator may represent a general mechanism for context-specific regulation of cell fate by autophagy.

Systematic analysis and validation of differential gene expression in ovarian serous adenocarcinomas and normal ovary

PURPOSE

Cancer of the ovary confers the worst prognosis among women with gynecological malignancies, primarily because most ovarian cancers are diagnosed at late stage. Hence, there is a substantial need to develop new diagnostic biomarkers to enable detection of ovarian cancer at earlier stages, which would confer better prognosis. In addition, the identification of druggable targets is of substantial interest to find new therapeutic strategies for ovarian cancer.

METHODS

The expression of 22,500 genes in a series of 67 serous papillary carcinomas was compared with 9 crudely enriched normal ovarian tissue samples by RNA hybridization on oligonucleotide microarrays. Multiple genes with near-uniformly expression were elevated in carcinomas of varying grade and malignant potential, including several previously described genes (e.g., MUC-1, CD9, CD24, claudin 3, and mesothelin). We performed immunohistochemical staining with antibodies against several of the proteins encoded by differentially expressed genes in an independent cohort of 71 cases of paraffin-embedded ovarian cancer samples.

RESULTS

We found striking differences in EpCAM (p < 0.005), CD9 (p < 0.001), MUC-1 (p < 0.001), and claudin 3 proteins (p < 0.001) but not for mesothelin (p > 0.05) using the Mann-Whitney U test.

CONCLUSIONS

Protein expression of a majority of the differentially expressed genes tested was found to be elevated in ovarian carcinomas and, as such, define potential new biomarkers or targets.

Differential expression of Fas family members and Bcl-2 family members in benign versus malignant epithelial ovarian cancer (EOC) in North Indian population

Epithelial ovarian cancer (EOC) represents the most challenging of gynecological malignancies. Defective apoptosis is a major causative factor in the development and progression of cancer. The two important pathways of apoptosis are extrinsic death receptor pathway (Fas family) and intrinsic mitochondrial pathway (Bcl-2 family). In this study, differential protein expression of the major Fas family members (Fas, FasL, and FAP-1) and Bcl-2 family members (Bax, Bcl-2, and Bcl-X(L)) in benign versus malignant surface epithelial ovarian tumors was evaluated at the protein level by immunohistochemistry. The expression of these molecules was compared in 30 benign versus 35 malignant surface epithelial ovarian tumors. The findings of the present study showed that there was no significant difference in the expression of the Fas family members in benign and malignant ovarian tumors. However, benign tumors showed higher levels of anti-apoptotic Bcl-2 protein levels (p < 0.009), whereas malignant tumors showed higher levels of pro-apoptotic Bax (p < 0.001). In general, there was no significant difference in Bcl-X(L) protein levels. The observations made in the present study suggest that alterations in expression of the Fas family and the Bcl-2 family members occur and play a key role in the deregulated growth of epithelial ovarian cancer.

Coexpression of MUC16 and mesothelin is related to the invasion process in pancreatic ductal adenocarcinoma

The invasion process is a crucial step for pancreatic ductal adenocarcinoma (PDAC); however, the genes related to invasion remain unclear. To identify specific genes for the invasion process, we compared microarray data for infiltrating cancer and PanIN-3, which were harvested from an individual PDAC patient by microdissection. Furthermore, immunohistochemical, coimmunoprecipitation and invasion analyses were performed to confirm the biologic significance of molecules identified by expression profile. In the present study, we focused on MUC16 and mesothelin among 87 genes that were significantly upregulated in infiltrating components compared to PanIN-3 in all PDAC patients, because MUC16 was the most differently expressed between two regions, and mesothelin was reported as the receptor for MUC16. Immunohistochemical analysis revealed that MUC16 and mesothelin were expressed simultaneously only in infiltrating components and increased at the invasion front, and binding of MUC16 and mesothelin was found in PDAC by immunoprecipitation assay. The downregulation of MUC16 by shRNA and the blockage of MUC16 binding to mesothelin by antibody inhibited both invasion and migration of pancreatic cancer cell line. MUC16 high/mesothelin high expression was an independent prognostic factor for poor survival in PDAC patients. In conclusion, we identified two specific genes, MUC16 and mesothelin, associated with the invasion process in patients with PDAC.

The nonreceptor-type tyrosine phosphatase PTPN13 is a tumor suppressor gene in non-small cell lung cancer

The aim of the present work was to identify protein tyrosine phosphatases (PTPs) as novel, candidate tumor suppressor genes in lung cancer. Among the 38 PTPs in the human genome that show specificity for phosphotyrosine, we identified six PTPs by quantitative RT-PCR whose mRNA expression levels were significantly down-regulated in lung cancer-derived cell lines (ie, PTPRE, PTPRF, PTPRU, PTPRK, PTPRD, and PTPN13). After validation in primary samples of non-small cell lung cancer (NSCLC), we selected PTPN13 for further studies. The results presented here demonstrate that PTPN13 is a candidate tumor suppressor gene that is frequently inactivated in NSCLC through the loss of either mRNA and protein expression (64/87, 73%) or somatic mutation (approximately 8%). Loss of PTPN13 expression was apparently due to the loss of one or both copies of the PTPN13 locus at 4q (approximately 26% double deletion and approximately 37% single deletion) but not to promoter methylation. Finally, the manipulation of PTPN13 expression in lung cancer cells (ie, NCI-H292, A549) demonstrated that PTPN13 negatively regulates anchorage-dependent and anchorage-independent growth in vitro and restrains tumorigenicity in vivo, possibly through the control of the tyrosine phosphorylation of both EGFR and HER2. In conclusion, the expression screening of PTPs in lung cancer reported here has identified PTPN13 as a novel candidate tumor suppressor in NSCLC whose loss increases signaling from epidermal growth factor receptor and HER2 tyrosine kinase receptors.

Characterisation of FAP-1 expression and CD95 mediated apoptosis in the A818-6 pancreatic adenocarcinoma differentiation system

The present study investigated the expression and localisation of FAP-1 (Fas associated phosphatase-1) and CD95 in a 3D differentiation model in comparison to 2D monolayers of the pancreatic adenocarcinoma cell line A818-6. Under non-adherent growth conditions, A818-6 cells differentiate into 3D highly organised polarised epithelial hollow spheres, resembling duct-like structures. A818-6 cells showed a differentiation-dependent FAP-1 localisation. Cells grown as 2D monolayers revealed FAP-1 staining in a juxtanuclear cisternal position, as well as localisation in the nucleus. After differentiation into hollow spheres, FAP-1 was relocated towards the actin cytoskeleton beneath the outer plasma membrane of polarised cells and no further nuclear localisation was observed. CD95 surface staining was found only in a subset of A818-6 monolayer cells, while differentiated hollow spheres appeared to express CD95 in all cells of a given sphere. We rarely observed co-localisation of CD95 and FAP-1 in A818-6 monolayer cells, but strong co-localisation beneath the outer plasma membrane in polarised cells. Analysis of surface expression by flow cytometry revealed that only a subset (36%) of monolayer cells showed CD95 surface expression, and after induction of hollow spheres, CD95 presentation at the outer plasma membrane was reduced to 13% of hollow spheres. Induction of apoptosis by stimulation with agonistic anti-CD95 antibodies, resulted in increased caspase activity in both, monolayer cells and hollow spheres. Knock down of FAP-1 mRNA in A818-6 monolayer cells did not alter resposiveness to CD95 agonistic antibodies. These data suggested that CD95 signal transduction was not affected by FAP-1 expression in A818-6 monolayer cells. In differentiated 3D hollow spheres, we found a polarisation-induced co-localisation of CD95 and FAP-1. A tight control of receptor surface representation and signalling induced apoptosis ensures controlled removal of individual cells instead of a "snowball effect" of apoptotic events.

FAP-1 and NF-κB expressions in oral squamous cell carcinoma as potential markers for chemo-radio sensitivity and prognosis

This study was designed to investigate the feasibility of using Fas-associated phosphatase-1 (FAP-1), nuclear factor kappa B (NF-κB) and p53 as markers for chemo-radio sensitivity in oral squamous cell carcinoma (OSCC). FAP-1 plays a role as an anti-apoptotic factor through Fas-dependent apoptosis after chemo-radiotherapy. NF-κB and p53 might be involved in modulation of FAP-1 expression. FAP-1, NF-κB and p53 expression were immunohistochemically examined using biopsy specimens in 50 OSCC patients treated with chemotherapy and/or radiotherapy. FAP-1 was expressed in 52%, NF-κB in 52% and p53 in 46% of patients. There was no significant difference in FAP-1, p53 or NF-κB expression according to the clinicopathological features. No correlation was found among FAP-1, p53 or NF-κB expression. FAP-1-positive cases showed a poorer survival rate than FAP-1-negative cases (P = 0.0409) and NF-κB-positive cases showed a poorer survival rate than NF-κB-negative cases (P = 0.0018). Multivariate analysis showed that FAP-1 expression, NF-κB expression, clinical stage and age were significant independent variables for survival (clinical stage: P = 0.0016; age: P = 0.0016; NF-κB: P = 0.0314; FAP-1: P = 0.0366). These results suggest that FAP-1 and NF-κB might play a role as chemo-radioresistant factor during chemo-radiotherapy, and FAP-1 and NF-κB expression in OSCC would be feasible markers for chemo-radio sensitivity and prognosis.

miR-200c regulates induction of apoptosis through CD95 by targeting FAP-1

Tumor progression shares many characteristics with the process of epithelial-to-mesenchymal transition (EMT). Cells that have undergone an EMT are known to have an increased resistance to apoptosis. CD95/Fas is an apoptosis-inducing receptor expressed on many tissues and tumor cells. During tumor progression CD95 is frequently downregulated, and tumor cells lose apoptosis sensitivity. miR-200 microRNAs repress both the EMT-inducing ZEB1 and ZEB2 transcription factors. We now demonstrate that miR-200c sensitizes cells to apoptosis mediated by CD95. We have identified the apoptosis inhibitor FAP-1 as a target for miR-200c. FAP-1 was demonstrated to be responsible for the reduced sensitivity to CD95-mediated apoptosis in cells with inhibited miR-200. The identification of FAP-1 as an miR-200c target provides a molecular mechanism to explain both the downregulation of CD95 expression and the reduction in sensitivity of cells to CD95-mediated apoptosis that is observed in the context of reduced miR-200 expression during tumor progression.

Genetic polymorphisms in the PTPN13 gene and risk of squamous cell carcinoma of head and neck

Fas-associated phosphatase-1 is encoded by the protein tyrosine phosphatase, non-receptor type 13 (PTPN13) gene and attributes to the resistance to Fas-mediated apoptosis in several tumors, including squamous cell carcinoma of the head and neck (SCCHN). However, no epidemiological studies have investigated the roles of PTPN13 polymorphisms in SCCHN risk. In this hospital-based case-control study of 1069 SCCHN patients and 1102 non-Hispanic white cancer-free controls, we evaluated the associations between three single-nucleotide polymorphisms c.4068 T>G F1356L (rs10033029), c.4566 A>G I1522M (rs2230600) and c.6241 T>G Y2081D (rs989902) located in the coding region of PTPN13 and SCCHN risk. We found that a significantly increased SCCHN risk was associated with the c.4566 I1522M GG genotype [odds ratio (OR), 1.89; 95% confidence interval (CI), 1.27-2.79] and c.6241 Y2081D GT genotype (OR, 1.26; 95% CI, 1.03-1.53) compared with the c.4566 I1522M AA and c.6241 Y2081D TT genotypes, respectively. Further stratified analyses showed that risk associated with the c.4566 I1522M GG genotype was more profound in the subgroups of young (< or = 57 years), males, never smokers, current drinkers and patients with pharyngeal cancer; that risk associated with c.6241 Y2081D GT genotype persisted in subgroups of old (>57 years), males, current drinkers and patients with pharyngeal and laryngeal cancers and that risk associated with c.6241 Y2081D GG genotype was borderline in patients with laryngeal cancer. In conclusion, polymorphisms in the PTPN13 coding region may be biomarkers for susceptibility to SCCHN in USA populations.

The impact of T-cell immunity on ovarian cancer outcomes

Ovarian cancer remains a challenging disease for which improved treatments are urgently needed. Most patients present with advanced disease that is highly responsive to surgery combined with platinum- and taxane-based chemotherapy, with a state of minimal residual disease being achieved in many cases. However, chemotherapy-resistant recurrent tumors typically appear within 1-5 years and are ultimately fatal. Recently, several groups have shown that ovarian tumors are often infiltrated by activated T cells at the time of diagnosis, and patients with dense infiltrates of CD3+CD8+ T cells experience unexpectedly favorable progression-free and overall survival. Other cell types in the immune infiltrate oppose anti-tumor immunity, including CD4+CD25+FoxP3+ regulatory T cells, CD8+ regulatory T cells, macrophages, and dendritic cells. The composition of immune infiltrates is shaped by the expression of cytokines, chemokines, antigens, major histocompatibility complex molecules, and costimulatory molecules. The relationship between these various immunological factors is reviewed here with a strong emphasis on outcomes data so as to create a knowledge base that is well grounded in clinical reality. With improved understanding of the functional properties of natural CD8+ T-cell responses to ovarian cancer, there is great potential to improve clinical outcomes by amplifying host immunity.

Bcl-B expression in human epithelial and nonepithelial malignancies

PURPOSE

Apoptosis plays an important role in neoplastic processes. Bcl-B is an antiapoptotic Bcl-2 family member, which is known to change its phenotype upon binding to Nur77/TR3. The expression pattern of this protein in human malignancies has not been reported.

EXPERIMENTAL DESIGN

We investigated Bcl-B expression in normal human tissues and several types of human epithelial and nonepithelial malignancy by immunohistochemistry, correlating results with tumor stage, histologic grade, and patient survival.

RESULTS

Bcl-B protein was strongly expressed in all normal plasma cells but found in only 18% of multiple myelomas (n = 133). Bcl-B immunostaining was also present in normal germinal center centroblasts and centrocytes and in approximately half of diffuse large B-cell lymphoma (n = 48) specimens, whereas follicular lymphomas (n = 57) did not contain Bcl-B. In breast (n = 119), prostate (n = 66), gastric (n = 180), and colorectal (n = 106) adenocarcinomas, as well as in non-small cell lung cancers (n = 82), tumor-specific overexpression of Bcl-B was observed. Bcl-B expression was associated with variables of poor prognosis, such as high tumor grade in breast cancer (P = 0.009), microsatellite stability (P = 0.0002), and left-sided anatomic location (P = 0.02) of colorectal cancers, as well as with greater incidence of death from prostate cancer (P = 0.005) and shorter survival of patients with small cell lung cancer (P = 0.009). Conversely, although overexpressed in many gastric cancers, Bcl-B tended to correlate with better outcome (P = 0.01) and more differentiated tumor histology (P < 0.0001).

CONCLUSIONS

Tumor-specific alterations in Bcl-B expression may define subsets of nonepithelial and epithelial neoplasms with distinct clinical behaviors.

PTPL1: a large phosphatase with a split personality

Protein tyrosine phosphatase, PTPL1, (also known as PTPN13, FAP-1, PTP-BAS, PTP1E) is a non-receptor type PTP and, at 270 kDa, is the largest phosphatase within this group. In addition to the well-conserved PTP domain, PTPL1 contains at least 7 putative macromolecular interaction domains. This structural complexity indicates that PTPL1 may modulate diverse cellular functions, perhaps exerting both positive and negative effects. In accordance with this idea, while certain studies suggest that PTPL1 can act as a tumor-promoting gene other experimental studies have suggested that PTPL1 may function as a tumor suppressor. The role of PTPL1 in the cancer cell is therefore likely to be both complex and context dependent with possible roles including the modulation of growth, stress-response, and cytoskeletal remodeling pathways. Understanding the nature of molecular complexes containing PTPL1, its interaction partners, substrates, regulation and subcellular localization are key to unraveling the complex personality of this protein phosphatase.

Regulation of CD95/APO-1/Fas-induced apoptosis by protein phosphatases

Triggering the CD95/APO-1/Fas receptor by CD95-L induces the assembly of the death-inducing signaling complex (DISC), which permits initiator caspases activation and progression of a signaling cascade that culminates in cellular apoptosis. Despite the CD95 receptor does not exhibit any kinase activity by itself, phosphorylation/dephosphorylation events seem important to regulate many aspects of CD95-mediated apoptosis. Here, we try to highlight particularly the importance of protein phosphatases in the modulation of the CD95 system.

FAP-1-mediated activation of NF-kappaB induces resistance of head and neck cancer to Fas-induced apoptosis

Molecular mechanisms responsible for tumor resistance to apoptosis often involve the Fas/FasL pathway. While squamous cell carcinomas of the head and neck (SCCHN) express both Fas and FasL, their resistance to self-induced apoptosis or apoptosis mediated by Fas agonistic antibody (CH-11Ab) was independent of the level of Fas surface expression or the presence of soluble Fas in supernatants of primary or metastatic SCCHN cell lines. By in vitro immunoselection, using PCI-15A cell line treated with successive cycles of CH-11 Ab, Fas-resistant sublines with the parental genotype were selected. Such sublines failed to cleave caspase-8 upon Fas engagement and were resistant to CH-11 Ab, although they remained sensitive to VP-16 or staurosporin. In the presence of cycloheximide, the selected SCCHN sublines become susceptible to CH-11 Ab, and showed cleavage of caspase-8, suggesting that apoptosis resistance was mediated by an inhibitory protein(s) acting upstream of caspase-8. Overexpression of Fas-associated phosphatase 1 (FAP-1), but not cellular FLICE-inhibitory protein (cFLIP) in SCCHN sublines was documented by Western blots and RT-PCR analyses. The FAP-1+ selected sublines also downregulated cell surface Fas. A high phosphorylation level of IkappaB kappa, NFkappaB activation and upregulation of Bcl-2 expression were observed in the FAP-1+ sublines. Treatment with the phosphatase inhibitor, orthovanadate, or silencing of FAP-1 with siRNA abolished their resistance to apoptosis, suggesting that FAP-1 phosphatase activity could be responsible for NF-kappaB activation and resistance of SCCHN cells to Fas-mediated apoptosis.

Regulation of TRP channel TRPM2 by the tyrosine phosphatase PTPL1

TRPM2, a member of the transient receptor potential (TRP) superfamily, is a Ca(2+)-permeable channel, which mediates susceptibility to cell death following activation by oxidative stress, TNFalpha, or beta-amyloid peptide. We determined that TRPM2 is rapidly tyrosine phosphorylated after stimulation with H(2)O(2) or TNFalpha. Inhibition of tyrosine phosphorylation with the tyrosine kinase inhibitors genistein or PP2 significantly reduced the increase in [Ca(2+)](i) observed after H(2)O(2) or TNFalpha treatment in TRPM2-expressing cells, suggesting that phosphorylation is important in TRPM2 activation. Utilizing a TransSignal PDZ domain array blot to identify proteins which interact with TRPM2, we identified PTPL1 as a potential binding protein. PTPL1 is a widely expressed tyrosine phosphatase, which has a role in cell survival and tumorigenesis. Immunoprecipitation and glutathione-S-transferase pull-down assays confirmed that TRPM2 and PTPL1 interact. To examine the ability of PTPL1 to modulate phosphorylation or activation of TRPM2, PTPL1 was coexpressed with TRPM2 in human embryonic kidney-293T cells. This resulted in significantly reduced TRPM2 tyrosine phosphorylation, and inhibited the rise in [Ca(2+)](i) and the loss of cell viability, which follow H(2)O(2) or TNFalpha treatment. Consistent with these findings, reduction in endogenous PTPL1 expression with small interfering RNA resulted in increased TRPM2 tyrosine phosphorylation, a significantly greater rise in [Ca(2+)](i) following H(2)O(2) treatment, and enhanced susceptibility to H(2)O(2)-induced cell death. Endogenous TRPM2 and PTPL1 was associated in U937-ecoR cells, confirming the physiological relevance of this interaction. These data demonstrate that tyrosine phosphorylation of TRPM2 is important in its activation and function and that inhibition of TRPM2 tyrosine phosphorylation reduces Ca(2+) influx and protects cell viability. They also suggest that modulation of TRPM2 tyrosine phosphorylation is a mechanism through which PTPL1 may mediate resistance to cell death.

Efficacy and antivascular effects of EphA2 reduction with an agonistic antibody in ovarian cancer

BACKGROUND

EphA2 is an oncoprotein and tyrosine kinase receptor that is overexpressed in ovarian and many other cancers. We investigated the effects of reduced EphA2 levels on tumor growth and the tumor microenvironment in an orthotopic ovarian cancer model.

METHODS

The effect of the EphA2-agonistic monoclonal antibody EA5, alone or in combination with paclitaxel, on the growth of ovarian cancer cells (SKOV3ip1, HeyA8, and HeyA8MDR [taxane-platinum resistant]) was determined in vitro and in vivo by immunoblotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, and immunohistochemical analysis. Expression of EphA2 and markers of angiogenesis (CD31, vascular endothelial growth factor [VEGF], and basic fibroblast growth factor), proliferation (proliferating cell nuclear antigen), and endothelial cell apoptosis (CD31-terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick-end labeling colocalization) and phosphorylation of Src were analyzed by immunoblotting, immunohistochemistry, immunofluorescence, and in situ hybridization in tumors from treated mice. Statistical tests were two-sided.

RESULTS

EA5 antibody treatment led to a more than 90% reduction in EphA2 expression in HeyA8 tumors in vivo. In mice bearing orthotopic SKOV3ip1 or HeyA8 tumors, 4 weeks of EA5 treatment resulted in tumors that weighed 31% and 45% less, respectively, than those in control (IgG-treated) mice (95% confidence interval [CI] = -0.09% to 71% and 20% to 70%, P = .27 and .01, respectively). Combination therapy with EA5 and paclitaxel reduced tumor weight by 77% and 80% (95% CI = 63% to 91% and 68% to 91%), respectively, compared with paclitaxel alone and by 92% and 88% (95% CI = 87% to 97% and 80% to 94%), respectively, compared with IgG alone. Combination therapy also reduced the weight of HeyA8MDR tumors by 47% (95% CI = 24% to 72%) compared with paclitaxel. Mice bearing SKOV3ip1 or HeyA8 tumors that were treated with combination therapy survived longer than those treated with paclitaxel alone (median survival = 144 versus 69 days and 46 versus 37 days, respectively). EA5-treated tumors had reduced microvascular density, proliferation, and VEGF protein and mRNA levels, with increased endothelial cell apoptosis. EphA2 was associated with Src, which was rapidly dephosphorylated after EA5 treatment.

CONCLUSIONS

EA5 in combination with paclitaxel decreased tumor growth in an orthotopic ovarian cancer mouse model through antiangiogenic mechanisms associated with reduced levels of VEGF and phosphorylated Src. Humanized antibody constructs against EphA2 are worthy of future study.

Ionizing radiation suppresses FAP-1 mRNA level in A549 cells via p53 activation

Ionizing radiation (IR) is known to upregulate cell surface Fas through p53 activation in various cells. However, the signaling pathway intermediating between p53 activation and cell surface Fas upregulation remains to be elucidated. Recently, Fas-associated phosphatase-1 (FAP-1) has been reported to associate with Fas and inhibit cell surface Fas expression. We evaluated the expression of FAP-1 mRNA following IR in A549 cells. Ionizing radiation inhibited the expression of FAP-1 mRNA. Pretreatment with p53 inhibitor pifithrin alpha cancelled the IR-induced downregulation of FAP-1 mRNA. These results suggest that IR-induced p53 activation may upregulate cell surface Fas via the down-modulation of FAP-1.

RETRACTED ARTICLE: Oleandrin-Mediated Expression of Fas Potentiates Apoptosis in Tumor Cells

Chemotherapeutic agent is characterized by its concentration in tumor cells with minimum side effects. Oleandrin, a polyphenolic cardiac glycoside is known to induce apoptosis in tumor cells. However, no report is available on its efficacy in primary cells. In this report we are providing the evidence that oleandrin induces apoptosis, not necrosis in tumor cells but not in primary cells like peripheral blood mononuclear cells (PBMC) and neutrophils. Oleandrin inhibited NF-kappaB activation in tumor cells but not in primary cells. It induced cell death in NF-kappaB-overexpressed tumor cells. Oleandrin induced Fas expression thereby inducing apoptosis in tumor cells but not in primary cells. Dominant negative FADD inhibited oleandrin-induced cell death in tumor cells. Overall, these results suggest that oleandrin mediates apoptosis in tumor cells by inducing Fas but not in primary cells indicating its potential anti-cancer property with no or slight side effect.

Tumor-associated alterations in caspase-14 expression in epithelial malignancies

PURPOSE

Caspase-14 is unique among caspase family proteases in that its proteolytic processing has been principally associated with epithelial cell differentiation rather than apoptosis or inflammation. We investigated caspase-14 expression in several types of human epithelial malignancy by immunohistochemistry, correlating results with stage, histologic grade, and patient survival.

EXPERIMENTAL DESIGN

Tumor-associated alterations in caspase-14 expression were observed for cervical, ovarian, breast, gastric, and colon cancers.

RESULTS

In cervical (n = 445), ovarian (n = 91), and colon (n = 106) specimens, expression of caspase-14 was significantly reduced in cancers compared with normal epithelium. Decreases in caspase-14 immunopositivity correlated with the histologic progression of cervical cancer (P < 0.0001, ANOVA). In localized gastric cancers, caspase-14 immunostaining was significantly lower in poorly differentiated tumors compared with well-differentiated tumors (P = 0.02, Pearson's chi(2) analysis). Lower caspase-14 expression was associated with advanced clinical stage in ovarian cancer (P = 0.04, ANOVA) and with shorter overall survival among ovarian cancer patients with serous tumors (n = 62) in both univariate (P = 0.005) and multivariate (P = 0.03) analysis. Lower caspase-14 expression correlated with shorter overall survival among patients with T(3)N(0)M(0) stage gastric cancers (n = 94; P = 0.006, log-rank test). In contrast to cervical, ovarian, and colon cancers, caspase-14 expression was increased in ductal carcinoma in situ and invasive cancers compared with normal mammary epithelium (P = 0.001, t test).

CONCLUSIONS

The findings reveal tumor-specific alterations in caspase-14 expression and suggest that differences in its expression may define subsets of epithelial cancers with distinct clinical behaviors.

FAS associated phosphatase (FAP-1) blocks apoptosis of astrocytomas through dephosphorylation of FAS

Astrocytomas are the most common primary tumor of the adult human central nervous system. Despite efforts to develop more effective clinical treatment strategies, median survival time for patients with the most severe form of astrocytoma, glioblastoma multiforme (GBM), remains about one year. Astrocytomas are resistant to cytotoxic therapy in general and radiation therapy in particular, greatly limiting treatment options. One reason for this seems to be defects in the pathways controlling apoptosis. We have characterized the role of the tyrosine phosphatase FAP-1 (FAS-associated phosphatase 1) in astrocytomas. Our studies demonstrate that FAP-1 is overexpressed in astrocytomas and this contributes to the resistance of the tumor cells to FAS-mediated apoptosis. We demonstrate that knockdown of FAP-1 by RNA interference leads to increased apoptosis and increased sensitivity of astrocytoma cells to FAS-induced cell death. FAP-1 binds to FAS in a ligand-dependent manner and forms a signaling complex that modulates the ability of astrocytoma cells to undergo FAS ligand (FASL)-mediated cell death. In astrocytoma cells, FASL treatment induces tyrosine phosphorylation of FAS. FAP-1 dephosphorylates phospho-tyrosine 275 in the carboxyl terminus of FAS. This is the first direct evidence that FAS activity can be regulated by reversible phosphorylation and suggests a mechanism for astrocytoma resistance to apoptosis.

Opposite roles of FAP-1 and dynamin in the regulation of Fas (CD95) translocation to the cell surface and susceptibility to Fas ligand-mediated apoptosis

Human melanoma is the most aggressive form of skin cancer and is extremely resistant to radiation and chemotherapy. One of the critical parameters of this resistance is down-regulation of Fas (CD95) cell-surface expression. Using TIG3 normal human fibroblasts and human melanoma cell lines, we investigated transcriptional regulation of FAP-1, a regulator of Fas translocation in the cell. Protein-tyrosine phosphatase FAP-1 (PTPN13, PTP-BAS) interacts with human Fas protein and prevents its export from the cytoplasm to the cell surface. In contrast, dynamin-2 facilitates Fas protein translocation from the Golgi apparatus via the trans-Golgi network to the cell surface. Suppression of dynamin functions by dominant negative dynamin K44A blocks Fas export, whereas the down-regulation of FAP-1 expression by specific RNA interference restores Fas export (a phenomenon that could still be down-regulated in the presence of dominant-negative dynamin). Based on the FAP-1- and dynamin-dependent regulation of Fas translocation, we have created human melanoma lines with different levels of surface expression of Fas. Treatment of these melanoma lines with soluble Fas ligand resulted in programmed cell death that was proportional to the pre-existing levels of surface Fas. Taking into consideration the well known observations that FAP-1 expression is often up-regulated in metastatic tumors, we have established a causal connection between high basal NF-kappaB transcription factor activity (which is a hallmark of many types of metastatic tumors) and NF-kappaB-dependent transcriptional regulation of FAP-1 gene expression that finally restricts Fas protein trafficking, thereby, facilitating the survival of cancer cells.

Molecular and prognostic distinction between serous ovarian carcinomas of varying grade and malignant potential

Profiles of gene transcription have begun to delineate the molecular basis of ovarian cancer, including distinctions between carcinomas of differing histology, tumor progression and patient outcome. However, the similarities and differences among the most commonly diagnosed noninvasive borderline (low malignant potential, LMP) lesions and invasive serous carcinomas of varying grade (G1, G2 and G3) have not yet been explored. Here, we used oligonucleotide arrays to profile the expression of 12,500 genes in a series of 57 predominantly stage III serous ovarian adenocarcinomas from 52 patients, eight with borderline tumors and 44 with adenocarcinomas of varying grade. Unsupervised and supervised analyses showed that LMP lesions were distinct from high-grade serous adenocarcinomas, as might be expected; however, well-differentiated (G1) invasive adenocarcinomas showed a strikingly similar profile to LMP tumors as compared to cancers with moderate (G2) or poor (G3) cellular differentiation, which were also highly similar. Comparative genomic hybridization of an independent cohort of five LMP and 63 invasive carcinomas of varying grade demonstrated LMP and G1 were again similar, exhibiting significantly less chromosomal aberration than G2/G3 carcinomas. A majority of LMP and G1 tumors were characterized by high levels of p21/WAF1, with concomitant expression of cell growth suppressors, gadd34 and BTG-2. In contrast, G2/G3 cancers were characterized by the expression of genes associated with the cell cycle and by STAT-1-, STAT-3/JAK-1/2-induced gene expression. The distinction between the LMP-G1 and G2-G3 groups of tumors was highly correlated to patient outcome (chi(2) for equivalence of death rates=7.681189; P=0.0056, log-rank test). Our results are consistent with the recent demonstration of a poor differentiation molecular 'meta-signature' in human cancer, and underscore a number of cell-cycle- and STAT-associated targets that may prove useful as points of therapeutic intervention for those patients with aggressive disease.

Potential role of protein tyrosine phosphatase nonreceptor type 13 in the control of oocyte meiotic maturation

Protein tyrosine phosphatase nonreceptor type 13 (PTPN13) is a tyrosine phosphatase with multiple interacting domains that has been implicated previously in the regulation of apoptosis. We provide evidence that PTPN13 plays an important role in the control of the meiotic cell cycle. A cDNA coding for PTPN13 was isolated during the screening for the substrate of protein kinase A expressed in mammalian oocytes. PTPN13 is expressed in both mouse and Xenopus oocytes and is a substrate for protein kinase A in vitro and in vivo. Expression of a truncated constitutively-active PTPN13 in Xenopus oocytes synergizes with progesterone in the induction of germinal vesicle breakdown, the translation of Mos, the phosphorylation of Erk and the dephosphorylation of Cdc2. The phosphatase activity of PTPN13 is required for this synergism. Oocyte injection with specific small interference RNA downregulates the expression of mRNA for PTPN13 and blocks oocyte maturation induced by progesterone, a blockade that can be overcome by Cdc25 overexpression. These findings indicate that PTPN13 is involved in the regulation of the meiotic cell cycle.

Update on NCI in vitro drug screen utilities

Development of new anti-cancer drugs is a costly and risky proposition. The Developmental Therapeutics Program (DTP) of the National Cancer Institutes of the United States (U.S.) facilitates the drug development process by providing access to preclinical screening services. Since the early 1990's, DTP has screened tens of thousands of compounds against a panel of 60 human tumour cell lines representing nine tissue sites. At the same time, DTP began to accumulate information on the expression of molecular entities in the same 60 cell line panel. Many of these data are freely available to the public at. More recently, additional, more focused screens have entered the picture, with data also available through the web site. These include screening of roughly 100000 compounds against a panel of yeast mutants, and screening of the NCI Diversity Set in assays designed to detect effects on Molecular Targets of interest.

The protein tyrosine phosphatase PTP-Basophil/Basophil-like

The protein tyrosine phosphatase PTP-Basophil (PTP-Bas) and its mouse homologue, PTP-Basophil-like (PTP-BL), are high molecular mass protein phosphatases consisting of a number of diverse protein-protein interaction modules. Several splicing variants of these phosphatases are known to exist thus demonstrating the complexity of these molecules. PTP-Bas/BL serves as a central scaffolding protein facilitating the assembly of a multiplicity of different proteins mainly via five different PDZ domains. Many of these interacting proteins are implicated in the regulation of the actin cytoskeleton. However, some proteins demonstrate a nuclear function of this protein tyrosine phosphatase. PTP-Bas is involved in the regulation of cell surface expression of the cell death receptor, Fas. Moreover, it is a negative regulator of ephrinB phosphorylation, a receptor playing an important role during development. The phosphorylation status of other proteins such as RIL, IkappaBalpha and beta-catenin can also be regulated by this phosphatase. Finally, PTP-BL has been shown to be involved in the regulation of cytokinesis, the last step in cell division. Although the precise molecular function of PTP-Bas/BL is still elusive, current data suggest clearly that PTP-Bas/BL belongs to the family of PDZ domain containing proteins involved in the regulation of the cytoskeleton and of intracellular vesicular transport processes.

Identification of biomarkers for ovarian cancer using strong anion-exchange ProteinChips: potential use in diagnosis and prognosis

One hundred eighty-four serum samples from patients with ovarian cancer (n = 109), patients with benign tumors (n = 19), and healthy donors (n = 56) were analyzed on strong anion-exchange surfaces using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry technology. Univariate and multivariate statistical analyses applied to protein-profiling data obtained from 140 training serum samples identified three biomarker protein panels. The first panel of five candidate protein biomarkers, termed the screening biomarker panel, effectively diagnosed benign and malignant ovarian neoplasia [95.7% sensitivity, 82.6% specificity, 89.2% accuracy, and receiver operating characteristic (ROC) area under the curve of 0.94]. The other two panels, consisting of five and four candidate protein biomarkers each, effectively distinguished between benign and malignant ovarian neoplasia and were therefore referred to as validation biomarker panel I (81.5% sensitivity, 94.9% specificity, 88.2% accuracy, and ROC = 0.94) and validation biomarker panel II (72.8% sensitivity, 94.9% specificity, 83.9% accuracy, and ROC = 0.90). The three ovarian cancer biomarker protein panels correctly diagnosed 41 of the 44 blinded test samples: 21 of 22 malignant ovarian neoplasias [10 of 11 early-stage ovarian cancer (I/II) and 11 of 11 advanced-stage ovarian cancer (III/IV)], 6 of 6 low malignant potential, 5 of the 6 benign tumors, and 9 of 10 normal patient samples. In conclusion, we have discovered three ovarian cancer biomarker protein panels that, when used together, effectively distinguished serum samples from healthy controls and patients with either benign or malignant ovarian neoplasia.

Tyrosine phosphatase-epsilon activates Src and supports the transformed phenotype of Neu-induced mammary tumor cells

Few tyrosine phosphatases support, rather than inhibit, survival of tumor cells. We present genetic evidence that receptor-type protein-tyrosine phosphatase (RPTP)-epsilon performs such a function, as cells from mammary epithelial tumors induced by activated Neu in mice genetically lacking RPTPepsilon appeared morphologically less transformed and exhibited reduced proliferation. We show that at the molecular level, RPTPepsilon activates Src, a known collaborator of Neu in mammary tumorigenesis. Lack of RPTPepsilon reduced Src activity and altered Src phosphorylation in tumor cells; RPTPepsilon dephosphorylated and activated Src; and Src bound a substrate-trapping mutant of RPTPepsilon. The altered morphology of tumor cells lacking RPTPepsilon was corrected by exogenous Src and exogenous RPTPepsilon or RPTPalpha; exogenous activated Src corrected also the growth rate phenotype. Together, these results suggest that the altered morphology of RPTPepsilon-deficient tumor cells is caused by reduced Src activity, caused, in turn, by lack of RPTPepsilon. Unexpectedly, the phenotype of RPTPepsilon-deficient tumor cells occurs despite expression of the related RPTPalpha, indicating that endogenous RPTPalpha does not compensate for the absence of RPTPepsilon in this case. We conclude that RPTPepsilon is a physiological activator of Src in Neu-induced mammary tumors and suggest that pharmacological inhibition of phosphatases that activate Src may be useful to augment direct pharmacological inhibition of Src.

FAP-1 association with Fas (Apo-1) inhibits Fas expression on the cell surface

As revealed by intracellular pools of nonactive Fas (Apo-1), export of Fas to the cell surface is often impaired in human tumors, thereby inactivating Fas ligand-mediated apoptosis. Here, we demonstrate that association with Fas-associated phosphatase 1 (FAP-1) attenuates Fas export to the cell surface. Forced expression of FAP-1 reduces cell surface Fas levels and increases the intracellular pool of Fas within the cytoskeleton network. Conversely, expression of dominant-negative forms of FAP-1, or inhibition of FAP-1 expression by short interfering RNA, efficiently up-regulates surface expression of Fas. Inhibition of Fas surface expression by FAP-1 depends on its association with the C terminus of Fas. Mutation within amino acid 275 results in decreased association with FAP-1 and greater export of Fas to the cell surface in melanomas, normal fibroblasts, or Fas null cells. Identifying the role of FAP-1 in binding to, and consequently inhibition of, Fas export to the cell surface provides novel insight into the mechanism underlying the regulation of Fas trafficking, which is commonly impaired in advanced tumors with FAP-1 overexpression.

DNA microarrays for assessing ovarian cancer gene expression

Although DNA microarray analysis is presented as a revolution in gene expression studies, it is in fact based on the classic technique of Southern DNA hybridisation where a labelled DNA probe is hybridised to single stranded DNA that is bound to a solid support matrix. The truly revolutionary aspect of microarray analysis lies in the fact that, within a given cell population, the expression of tens of thousands of genes, and ultimately the entire genome, can be assayed simultaneously. This capability, when coupled with powerful data analysis software, allows researchers to rapidly compare gene expression between two cell populations. In the cancer field, this enables researchers to compare gene expression between normal and malignant cells and to identify genes that are differentially regulated during cancer development. Microarray data can also be used to categorize tumours on the basis of their molecular profile, which may provide important biological, diagnostic and prognostic information. As little as 5 years ago identifying even a few differentially expressed genes may have taken several years and cost tens of thousands of dollars. Today microarrays can identify ten times the number of candidate genes in just a few months and at a tenth of the cost. Even so, microarray analysis is still in its infancy and the technology is advancing rapidly. There is little doubt that microarrays will revolutionize our ability to quantify the complex changes that occur in gene expression during cancer development. The greatest challenge that lies ahead is how to translate this knowledge into clinically useful diagnostic and therapeutic tools. In this review, we describe the technical aspects of DNA microarray analysis and some of the current and future applications of this technology for analysing gene expression in ovarian cancer.