CL100 expression is down-regulated in advanced epithelial ovarian cancer and its re-expression decreases its malignant potential

Atypical phosphatase DUSP11 inhibition promotes nc886 expression and potentiates gemcitabine-mediated cell death through NF-kB modulation

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers among all solid tumors. First-line treatment relies on gemcitabine (Gem) and despite treatment improvements, refractoriness remains a universal challenge. Attempts to decipher how feedback-loops control signaling pathways towards drug resistance have gained attention in recent years, particularly focused on the role of phosphatases. In this study, a CRISPR/Cas9-based phenotypic screen was performed to identify members from the dual-specificity phosphatases (DUSP) family potentially acting on Gem response in PDAC cells. The approach revealed the atypical RNA phosphatase DUSP11 as a potential target, whose inhibition creates vulnerability of PDAC cells to Gem. DUSP11 genetic inhibition impaired cell survival and promoted apoptosis, synergistically enhancing Gem cytotoxicity. In silico transcriptome analysis of RNA-seq data from PDAC human samples identified NF-ĸB signaling pathway highly correlated with DUSP11 upregulation. Consistently, Gem-induced NF-ĸB phosphorylation was blocked upon DUSP11 inhibition in vitro. Mechanistically, we found that DUSP11 directly impacts nc886 expression and modulates PKR-NF-ĸB signaling cascade after Gem exposure in PDAC cells resulting in resistance to Gem-induced cell death. In conclusion, this study provides new insights on DUSP11 role in RNA biology and Gem response in PDAC cells.

MKP-1 overexpression is associated with chemoresistance in bladder cancer via the MAPK pathway

Mitogen activated protein kinase phosphatase-1 (MKP-1) has been revealed to be overexpressed in bladder cancer, particularly in non-muscle invasive bladder cancer. MKP-1 may also be associated with chemotherapy resistance. However, the underlying mechanism is yet to be elucidated. The current study investigated the expression of MKP-1 by performing immunohistochemistry in surgically resected specimens obtained from primary and recurrent patients with bladder cancer. The results revealed that MKP-1 expression increased in recurrent patients. Additionally, a 3D model of the human bladder cancer cell line, RT112, was established to determine the role of MKP-1 in drug resistance. The results demonstrated that MKP-1 overexpression protected bladder cancer cells against cell death. Contrarily, MKP-1 knockdown was revealed to sensitize cells to death. In addition, the application of MAPK inhibitors effectively increased RT112 cell sensitivity to pirarubicin. In conclusion, the results of the current study indicated that MKP-1 treatment resulted in bladder cancer cell chemoresistance via JNK, ERK and p38 pathways. MKP-1 may also serve as a potential therapeutic target for chemoresistance in patients with bladder cancer.

ERK Dephosphorylation through MKP1 Deacetylation by SIRT1 Attenuates RAS-Driven Tumorigenesis

The role of Situin 1 (SIRT1) in tumorigenesis is still controversial due to its wide range of substrates, including both oncoproteins and tumor suppressors. A recent study has demonstrated that SIRT1 interferes in the Kirsten rat sarcoma viral oncogene homolog (KRAS)-driven activation of the Raf-mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK pathway, thereby inhibiting tumorigenesis. However, the molecular mechanism of SIRT1 as a tumor suppressor in RAS-driven tumorigenesis has been less clearly determined. This study presents evidence that the ectopic expression of SIRT1 attenuates RAS- or MEK-driven ERK activation and reduces cellular proliferation and transformation in vitro. The attenuation of ERK activation by SIRT1 results from prompt dephosphorylation of ERK, while MEK activity remains unchanged. We identified that MKP1, a dual specific phosphatase for MAPK, was deacetylated by SIRT1. Deacetylation of MKP1 by direct interaction with SIRT1 increased the binding affinity to ERK which in turn facilitated inactivation of ERK. Taken together, these results suggest that SIRT1 would act as a tumor suppressor by modulating RAS-driven ERK activity through MKP1 deacetylation.

The impact of phosphatases on proliferative and survival signaling in cancer

The dynamic and stringent coordination of kinase and phosphatase activity controls a myriad of physiologic processes. Aberrations that disrupt the balance of this interplay represent the basis of numerous diseases. For a variety of reasons, early work in this area portrayed kinases as the dominant actors in these signaling events with phosphatases playing a secondary role. In oncology, these efforts led to breakthroughs that have dramatically altered the course of certain diseases and directed vast resources toward the development of additional kinase-targeted therapies. Yet, more recent scientific efforts have demonstrated a prominent and sometimes driving role for phosphatases across numerous malignancies. This maturation of the phosphatase field has brought with it the promise of further therapeutic advances in the field of oncology. In this review, we discuss the role of phosphatases in the regulation of cellular proliferation and survival signaling using the examples of the MAPK and PI3K/AKT pathways, c-Myc and the apoptosis machinery. Emphasis is placed on instances where these signaling networks are perturbed by dysregulation of specific phosphatases to favor growth and persistence of human cancer.

DUSP1 induces apatinib resistance by activating the MAPK pathway in gastric cancer

Dual-specificity phosphatase-1 (DUSP1) is an oncogene that is associated with cancer progression following drug resistance. In order to investigate the potential relationship between DUSP1 and apatinib resistance in gastric cancer cells, we preformed many assays to study this problem. DUSP1 gene was detected by RT-qPCR assay, proteins in MAPK pathway were quantified by western blot assay, and CCK-8 assay, flow cytometry and Hoechest 33342 stain were performed to detect the resistance of cells, cell cycles and apoptosis, respectively. Immunohistochemical staining was used to discover the expression of DUSP1 protein in patients' tumor or paratumor tissues. It was found that apatinib (Apa)-resistant gastric cancer (GC) cells showed increased expression of DUSP1, whereas the knockdown of DUSP1 in resistant cells resensitized these cells to Apa. The restored sensitivity to Apa was the result of inactivation of mitogen-activated protein kinase (MAPK) signaling and the induction of apoptosis. The in vitro use of Apa in combination with a DUSP1 inhibitor, triptolide, exerted significant effects on inhibiting the expression of DUSP1, growth inhibition, and apoptosis via the inactivation of MAPK signaling. In patients who did not undergo chemotherapy or targeted therapy, the expression of DUSP1 in adjacent tissues was higher when compared with that observed in tumor tissues. In addition, the expression of DUSP1 was higher in the early stages of GC than in the advanced stages. The expression of DUSP1 in tumor tissues was not associated with the survival rate of the patients. Therefore, increased expression of DUSP1 may be responsible for Apa resistance, and DUSP1 may serve as a biomarker for Apa efficacy. In conclusion, inducing the downregulation of DUSP1 may be a promising strategy to overcome Apa resistance.

High expression of MKP1/DUSP1 counteracts glioma stem cell activity and mediates HDAC inhibitor response

The elucidation of mechanisms involved in resistance to therapies is essential to improve the survival of patients with malignant gliomas. A major feature possessed by glioma cells that may aid their ability to survive therapy and reconstitute tumors is the capacity for self-renewal. We show here that glioma stem cells (GSCs) express low levels of MKP1, a dual-specificity phosphatase, which acts as a negative inhibitor of JNK, ERK1/2, and p38 MAPK, while induction of high levels of MKP1 expression are associated with differentiation of GSC. Notably, we find that high levels of MKP1 correlate with a subset of glioblastoma patients with better prognosis and overall increased survival. Gain of expression studies demonstrated that elevated MKP1 impairs self-renewal and induces differentiation of GSCs while reducing tumorigenesis in vivo. Moreover, we identified that MKP1 is epigenetically regulated and that it mediates the anti-tumor activity of histone deacetylase inhibitors (HDACIs) alone or in combination with temozolomide. In summary, this study identifies MKP1 as a key modulator of the interplay between GSC self-renewal and differentiation and provides evidence that the activation of MKP1, through epigenetic regulation, might be a novel therapeutic strategy to overcome therapy resistance in glioblastoma.

Formyl peptide receptor 2 expression predicts poor prognosis and promotes invasion and metastasis in epithelial ovarian cancer

Formyl peptide receptor 2 (FPR2) has been identified as a member of the G protein-coupled chemoattractant receptor (GPCR) family and has been implicated as playing a role in both inflammation and cancer development. Epithelial ovarian cancer (EOC) has been suggested to be correlated with both infectious and non-infectious inflammation. To date, the role of FPR2 in EOC remains poorly understood and controversial. In the present study, we aimed to investigate the potential of FPR2 in regulating EOC. We performed immunohistochemistry and RT-qPCR to analyzed expression of FPR2 in EOC tissues and the correlation between FPR2 and EOC clinicopathological characteristics as well as prognosis were also analyzed. To test the role of FPR2 in EOC cell migration, we established FPR2-knockdown SKOV3 cells and performed wound-healing, Transwell and angiogenesis assays to detect the metastatic potential of these EOC cells. Our studies found that FPR2 was overexpressed in EOC tissues and was positively correlated with EOC clinicopathological characteristics including the International Federation of Gynecology and Obstetrics (FIGO) stage, histological grade and ovarian cancer type. Survival analyses suggested that FPR2 overexpression indicated the poorer prognosis of EOC patients and FPR2 may act as an independent risk factor for EOC prognosis. FPR2 knockdown decreased the migration potential of the ovarian cancer cells. Moreover, serum amyloid A (SAA) may stimulate the migration of SKOV3 cells through FPR2. The present study suggested that FPR2 promoted the invasion and metastasis of EOC and it could be a prognostic marker for EOC.

Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification

Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.

Phosphatases and solid tumors: focus on glioblastoma initiation, progression and recurrences

Phosphatases and cancer have been related for many years now, as these enzymes regulate key cellular functions, including cell survival, migration, differentiation and proliferation. Dysfunctions or mutations affecting these enzymes have been demonstrated to be key factors for oncogenesis. The aim of this review is to shed light on the role of four different phosphatases (PTEN, PP2A, CDC25 and DUSP1) in five different solid tumors (breast cancer, lung cancer, pancreatic cancer, prostate cancer and ovarian cancer), in order to better understand the most frequent and aggressive primary cancer of the central nervous system, glioblastoma.

Role of DUSP1/MKP1 in tumorigenesis, tumor progression and therapy

Dual‐specificity phosphatase‐1 (DUSP1/MKP1), as a member of the threonine‐tyrosine dual‐specificity phosphatase family, was first found in cultured murine cells. The molecular mechanisms of DUSP1‐mediated extracellular signal‐regulated protein kinases (ERKs) dephosphorylation have been subsequently identified by studies using gene knockout mice and gene silencing technology. As a protein phosphatase, DUSP1 also downregulates p38 MAPKs and JNKs signaling through directly dephosphorylating threonine and tyrosine. It has been detected that DUSP1 is involved in various functions, including proliferation, differentiation, and apoptosis in normal cells. In various human cancers, abnormal expression of DUSP1 was observed which was associated with prognosis of tumor patients. Further studies have revealed its role in tumorigenesis and tumor progression. Besides, DUSP1 has been found to play a role in tumor chemotherapy, immunotherapy, and biotherapy. In this review, we will focus on the function and mechanism of DUSP1 in tumor cells and tumor treatment.

Microarray phosphatome profiling of breast cancer patients unveils a complex phosphatase regulatory role of the MAPK and PI3K pathways in estrogen receptor-negative breast cancers

Phosphatases are proteins with the ability to dephosphorylate different substrates and are involved in critical cellular processes such as proliferation, tumor suppression, motility and survival. Little is known about their role in the different breast cancer (BC) phenotypes. We carried out micro-array phosphatome profiling in 41 estrogen receptor-negative (ER⁻) BC patients, as determined by immunohistochemistry (IHC), containing both ERBB2⁺ and ERBB2⁻ in order to characterize the differences between these two groups. We characterized and confirmed the distinct phosphatome of the two main ER⁻ BC subgroups (in two independent microarrays series) and that of ER⁺ BC (in three large independent series). Our findings point to the importance of the MAPK and PI3K pathways in ER⁻ BCs as some of the most differentially expressed phosphatases (like DUSP4 and DUSP6) sharing ERK as substrate, or regulating the PI3K pathway (INPP4B, PTEN). It was possible to identify a selective group of phosphatases upregulated only in the ER⁻ ERBB2⁺ subgroup and not in ER⁺ (like DUSP6, DUSP10 and PPAPDC1A among others), suggesting a role of these phosphatases in specific BC subtypes, unlike other differentially expressed phosphatases (DUSP4 and ENPP1) that seemed to have a role in multiple BC subtypes. Significant correlation was found at the protein level by IHC between the expression of DUSP6 and phospho-ERK (p=0.04) but not of phospho-ERK with DUSP4. To show the potential prognostic relevance of phosphatases as a functional group of genes, we derived and validated in two large independent BC microarray series a multiphosphatase signature enriched in differentially expressed phosphatases, to predict distant metastasis-free survival (DMFS). ER⁻ ERBB2⁺, ER⁻ ERBB2⁻ and ER⁺ BC patients have a distinct pattern of phosphatase RNA expression with a potential prognostic relevance. Further studies of the most relevant phosphatases found in this study are warranted.

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.

Ovarian cancer molecular pathology

Ovarian cancer (OVC) is the fourth leading cause of cancer mortality among women in Europe and the United States. Its early detection is difficult due to the lack of specificity of clinical symptoms. Unfortunately, late diagnosis is a major contributor to the poor survival rates for OVC, which can be attributed to the lack of specific sets of markers. Aside from patients sharing a strong family history of ovarian and breast cancer, including the BRCA1 and BRCA2 tumor suppressor genes mutations, the most used biomarker is the Cancer-antigen 125 (CA-125). CA-125 has a sensitivity of 80 % and a specificity of 97 % in epithelial cancer (stage III or IV). However, its sensitivity is 30 % in stage I cancer, as its increase is linked to several physiological phenomena and benign situations. CA-125 is particularly useful for at-risk population diagnosis and to assess response to treatment. It is clear that alone, CA-125 is inadequate as a biomarker for OVC diagnosis. There is an unmet need to identify additional biomarkers. Novel and more sensitive proteomic strategies such as MALDI mass spectrometry imaging studies are well suited to identify better markers for both diagnosis and prognosis. In the present review, we will focus on such proteomic strategies in regards to OVC signaling pathways, OVC development and escape from the immune response.

Protein tyrosine phosphatases in cancer: friends and foes!

Tyrosine phosphorylation of proteins serves as an exquisite switch in controlling several key oncogenic signaling pathways involved in cell proliferation, apoptosis, migration, and invasion. Since protein tyrosine phosphatases (PTPs) counteract protein kinases by removing phosphate moieties on target proteins, one may intuitively think that PTPs would act as tumor suppressors. Indeed, one of the most described PTPs, namely, the phosphatase and tensin homolog (PTEN), is a tumor suppressor. However, a growing body of evidence suggests that PTPs can also function as potent oncoproteins. In this chapter, we provide a broad historical overview of the PTPs, their mechanism of action, and posttranslational modifications. Then, we focus on the dual properties of classical PTPs (receptor and nonreceptor) and dual-specificity phosphatases in cancer and summarize the current knowledge of the signaling pathways regulated by key PTPs in human cancer. In conclusion, we present our perspective on the potential of these PTPs to serve as therapeutic targets in cancer.

Diversity and specificity of the mitogen-activated protein kinase phosphatase-1 functions

The balance of protein phosphorylation is achieved through the actions of a family of protein serine/threonine kinases called the mitogen-activated protein kinases (MAPKs). The propagation of MAPK signals is attenuated through the actions of the MAPK phosphatases (MKPs). The MKPs specifically inactivate the MAPKs by direct dephosphorylation. The archetypal MKP family member, MKP-1 has garnered much of the attention amongst its ten other MKP family members. Initially viewed to play a redundant role in the control of MAPK signaling, it is now clear that MKP-1 exerts profound regulatory functions on the immune, metabolic, musculoskeletal and nervous systems. This review focuses on the physiological functions of MKP-1 that have been revealed using mouse genetic approaches. The implications from studies using MKP-1-deficient mice to uncover the role of MKP-1 in disease will be discussed.

CacyBP/SIP phosphatase activity in neuroblastoma NB2a and colon cancer HCT116 cells

Recently, we have reported that CacyBP/SIP could be a novel phosphatase for ERK1/2 kinase. In this work, we analyzed the CacyBP/SIP phosphatase activity toward ERK1/2 in 2 cell lines of different origin. We showed that overexpression of CacyBP/SIP in NB2a cells resulted in a lower level of phosphorylated ERK1/2 (P-ERK1/2) in the nuclear fraction while such overexpression in HCT116 cells had no effect on the level of P-ERK1/2. Moreover, we found that overexpression of CacyBP/SIP resulted in higher phosphatase activity in the nuclear fraction obtained from NB2a cells when compared with HCT116 cells. Using 2-D electrophoresis we showed that the pattern of spots representing CacyBP/SIP differed in these 2 cell lines and was probably due to a different phosphorylation state of this protein. We also established that after overexpression of CacyBP/SIP in NB2a cells, the amount of nuclear β-catenin was low, while it remained high in HCT116 cells. Since NB2a cells have differentiation potential and HCT116 cells do not, our data suggest that different activity of CacyBP/SIP in these 2 cell lines might affect the ERK1/2 pathway in the differentiation or proliferation processes.

Mitogen-activated protein kinase phosphatase (MKP)-1 in immunology, physiology, and disease

Mitogen-activated protein kinases (MAPKs) are key regulators of cellular physiology and immune responses, and abnormalities in MAPKs are implicated in many diseases. MAPKs are activated by MAPK kinases through phosphorylation of the threonine and tyrosine residues in the conserved Thr-Xaa-Tyr domain, where Xaa represents amino acid residues characteristic of distinct MAPK subfamilies. Since MAPKs play a crucial role in a variety of cellular processes, a delicate regulatory network has evolved to control their activities. Over the past two decades, a group of dual specificity MAPK phosphatases (MKPs) has been identified that deactivates MAPKs. Since MAPKs can enhance MKP activities, MKPs are considered as an important feedback control mechanism that limits the MAPK cascades. This review outlines the role of MKP-1, a prototypical MKP family member, in physiology and disease. We will first discuss the basic biochemistry and regulation of MKP-1. Next, we will present the current consensus on the immunological and physiological functions of MKP-1 in infectious, inflammatory, metabolic, and nervous system diseases as revealed by studies using animal models. We will also discuss the emerging evidence implicating MKP-1 in human disorders. Finally, we will conclude with a discussion of the potential for pharmacomodulation of MKP-1 expression.

Inside the human cancer tyrosine phosphatome

Members of the protein tyrosine phosphatase (Ptp) family dephosphorylate target proteins and counter the activities of protein tyrosine kinases that are involved in cellular phosphorylation and signalling. As such, certain PTPs might be tumour suppressors. Indeed, PTPs play an important part in the inhibition or control of growth, but accumulating evidence indicates that some PTPs may exert oncogenic functions. Recent large-scale genetic analyses of various human tumours have highlighted the relevance of PTPs either as putative tumour suppressors or as candidate oncoproteins. Progress in understanding the regulation and function of PTPs has provided insights into which PTPs might be potential therapeutic targets in human cancer.

The investigation of mitogen-activated protein kinase phosphatase-1 as a potential pharmacological target in non-small cell lung carcinomas, assisted by non-invasive molecular imaging

Background

Invasiveness and metastasis are the most common characteristics of non small cell lung cancer (NSCLC) and causes of tumour-related morbidity and mortality. Mitogen-activated protein kinases (MAPKs) signalling pathways have been shown to play critical roles in tumorigenesis. However, the precise pathological role(s) of mitogen-activated protein kinase phosphatase-1 (MKP-1) in different cancers has been controversial such that the up-regulation of MKP-1 in different cancers does not always correlate to a better prognosis. In this study, we showed that the induction of MKP-1 lead to a significant retardation of proliferation and metastasis in NSCLC cells. We also established that rosiglitazone (a PPARγ agonist) elevated MKP-1 expression level in NSCLC cells and inhibited tumour metastasis.

Methods

Both wildtype and dominant negative forms of MKP-1 were constitutively expressed in NSCLC cell line H441GL. The migration and invasion abilities of these cells were examined in vitro. MKP-1 modulating agents such as rosiglitazone and triptolide were used to demonstrate MKP-1's role in tumorigenesis. Bioluminescent imaging was utilized to study tumorigenesis of MKP-1 over-expressing H441GL cells and anti-metastatic effect of rosiglitazone.

Results

Over-expression of MKP-1 reduced NSCLC cell proliferation rate as well as cell invasive and migratory abilities, evident by the reduced expression levels of MMP-2 and CXCR4. Mice inoculated with MKP-1 over-expressing H441 cells did not develop NSCLC while their control wildtype H441 inoculated littermates developed NSCLC and bone metastasis. Pharmacologically, rosiglitazone, a peroxisome proliferator activated receptor-γ (PPARγ) agonist appeared to induce MKP-1 expression while reduce MMP-2 and CXCR4 expression. H441GL-inoculated mice receiving daily oral rosiglitazone treatment demonstrated a significant inhibition of bone metastasis when compared to mice receiving sham treatment. We found that rosiglitazone treatment impeded the ability of cell migration and invasion in vitro. Cells pre-treated with triptolide (a MKP-1 inhibitor), reversed rosiglitazone-mediated cell invasion and migration.

Conclusion

The induction of MKP-1 could significantly suppress the proliferative and metastatic abilities of NSCLC both in vitro and in vivo. Therefore, MKP-1 could be considered as a potential therapeutic target in NSCLC therapy and PPARγ agonists could be explored for combined chemotherapy.

Mitogen-activated protein (MAP) kinase/MAP kinase phosphatase regulation: roles in cell growth, death, and cancer

Mitogen-activated protein kinase dual-specificity phosphatase-1 (also called MKP-1, DUSP1, ERP, CL100, HVH1, PTPN10, and 3CH134) is a member of the threonine-tyrosine dual-specificity phosphatases, one of more than 100 protein tyrosine phosphatases. It was first identified approximately 20 years ago, and since that time extensive investigations into both mkp-1 mRNA and protein regulation and function in different cells, tissues, and organs have been conducted. However, no general review on the topic of MKP-1 exists. As the subject matter pertaining to MKP-1 encompasses many branches of the biomedical field, we focus on the role of this protein in cancer development and progression, highlighting the potential role of the mitogen-activated protein kinase (MAPK) family. Section II of this article elucidates the MAPK family cross-talk. Section III reviews the structure of the mkp-1 encoding gene, and the known mechanisms regulating the expression and activity of the protein. Section IV is an overview of the MAPK-specific dual-specificity phosphatases and their role in cancer. In sections V and VI, mkp-1 mRNA and protein are examined in relation to cancer biology, therapeutics, and clinical studies, including a discussion of the potential role of the MAPK family. We conclude by proposing an integrated scheme for MKP-1 and MAPK in cancer.

Asparagine synthetase is a predictive biomarker of L-asparaginase activity in ovarian cancer cell lines

We recently used RNA interference to show that a negative correlation of L-asparaginase (L-ASP) chemotherapeutic activity with asparagine synthetase (ASNS) expression in the ovarian subset of the NCI-60 cell line panel is causal. To determine whether that relationship would be sustained in a larger, more diverse set of ovarian cell lines, we have now measured ASNS mRNA expression using microarrays and a branched-DNA RNA assay, ASNS protein expression using an electrochemiluminescent immunoassay, and L-ASP activity using an MTS assay on 19 human ovarian cancer cell lines. Contrary to our previous findings, L-ASP activity was only weakly correlated with ASNS mRNA expression; Pearson's correlation coefficients were r = -0.21 for microarray data and r = -0.39 for the branched-DNA RNA assay, with just the latter being marginally statistically significant (P = 0.047, one-tailed). ASNS protein expression measured by liquid-phase immunoassay exhibited a much stronger correlation (r = -0.65; P = 0.0014, one-tailed). We conclude that ASNS protein expression measured by immunoassay is a strong univariate predictor of L-ASP activity in ovarian cancer cell lines. These findings provide rationale for evaluation of ASNS protein expression as a predictive biomarker of clinical L-ASP activity in ovarian cancer.

Docosahexaenoic acid induces apoptosis in lung cancer cells by increasing MKP-1 and down-regulating p-ERK1/2 and p-p38 expression

Different agents able to modulate apoptosis have been shown to modify the expression of the MAP-kinase-phosphatase-1 (MKP-1). The expression of this phosphatase has been considered a potential positive prognostic factor in lung cancer, and smoke was shown to reduce the levels of MKP-1 in ferret lung. Our aim was to assess whether the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA), known to inhibit the growth of several cancer cells mainly inducing apoptosis, may exert pro-apoptotic effect in lung cancer cells by modifying MKP-1 expression. We observed that DHA increased MKP-1 protein and mRNA expression and induced apoptosis in different lung cancer cell lines (mink Mv1Lu adenocarcinoma cells, human A549 adenocarcinoma and human BEN squamous carcinoma cells). We inhibited the pro-apoptotic effect of DHA by treating the cells with the phosphatase inhibitor Na(3)VO(4) or by silencing the MKP-1 gene with the specific siRNA. This finding demonstrated that the induction of apoptosis by DHA involved a phosphatase activity, specifically that of MKP-1. DHA reduced also the levels of the phosphorylated MAP-kinases, especially ERK1/2 and p38. Such an effect was not observed when the MKP-1 gene was silenced. Altogether, the data provide evidence that the DHA-induced overexpression of MKP-1 and the resulting decrease of MAP-kinase phosphorylation by DHA may underlie the pro-apoptotic effect of this fatty acid in lung cancer cells. Moreover, they support the hypothesis that DHA may exert chemopreventive action in lung cancer.

The aryl hydrocarbon receptor repressor is a putative tumor suppressor gene in multiple human cancers

The aryl hydrocarbon receptor repressor (AHRR) is a bHLH/Per-ARNT-Sim transcription factor located in a region of chromosome 5 (5p15.3) that has been proposed to contain one or more tumor suppressor genes. We report here consistent downregulation of AHRR mRNA in human malignant tissue from different anatomical origins, including colon, breast, lung, stomach, cervix, and ovary, and demonstrate DNA hypermethylation as the regulatory mechanism of AHRR gene silencing. Knockdown of AHRR gene expression in a human lung cancer cell line using siRNA significantly enhanced in vitro anchorage-dependent and -independent cell growth as well as cell growth after transplantation into immunocompromised mice. In addition, knockdown of AHRR in non-clonable normal human mammary epithelial cells enabled them to grow in an anchorage-independent manner. Further, downregulation of AHRR expression in the human lung cancer cell line conferred resistance to apoptotic signals and enhanced motility and invasion in vitro and angiogenic potential in vivo. Ectopic expression of AHRR in tumor cells resulted in diminished anchorage-dependent and -independent cell growth and reduced angiogenic potential. These results therefore demonstrate that AHRR is a putative new tumor suppressor gene in multiple types of human cancers.

Role of mitogen-activated protein kinase phosphatases (MKPs) in cancer

The mitogen-activated protein kinase (MAPK) phosphatases (MKPs) are a family of dual-specificity protein phosphatases that dephosphorylate both phospho-threonine and phospho-tyrosine residues in MAP kinases, including the c-Jun N-terminal protein kinase (JNK)/stress-activated protein kinase (SAPK), the p38 MAPK, and the extracellular signal-related kinase (ERK). Since phosphorylation is required for the activation of MAP kinases, dephosphorylation by MKPs inhibits MAPK activity, thereby negatively regulating MAPK signaling. It is known that deregulation of MAPK signaling is the most common alteration in human cancers. Recent studies have suggested that MKPs play an important role not only in the development of cancers, but also in the response of cancer cells to chemotherapy. Thus, understanding the roles of MKPs in the development of cancer and their impact on chemotherapy can be exploited for therapeutic benefits for the treatment of human cancer.

Dual specificity phosphatase 1/CL100 is a direct transcriptional target of E2F-1 in the apoptotic response to oxidative stress

E2F-1 mediates apoptosis through transcriptional regulation of its targets. We report here that E2F-1 acts as a direct transcriptional regulator of dual specificity phosphatase 1 (DUSP1; CL100), a threonine and tyrosine phosphatase that inhibits mitogen-activated protein (MAP) kinases. We found that DUSP1 is transcriptionally induced by ectopic E2F-1 expression and that extracellular signal-regulated kinase 1/2 are dephosphorylated in the presence of E2F-1 and DUSP1. E2F-1 mediates apoptosis in the cellular response to oxidative stress. DUSP1 levels are significantly increased in an E2F-1-dependent manner following oxidative stress but not other stresses examined. DUSP1 mediates the cellular response to oxidative stress. We found that E2F-1 binds to chromatin encompassing the DUSP1 promoter and greatly stimulates the promoter activity of the DUSP1 gene. In particular, E2F-1 physically binds to an E2F-1 consensus sequence and a palindromic motif in the DUSP1 promoter. Interestingly, E2F-1 is acetylated following oxidative stress. Our findings show that E2F-1 is a transcriptional activator of DUSP1 and that DUSP1 is a link between E2F-1 and MAP kinases.

Role of MAPK Phosphatase-1 in the Induction of Monocyte Chemoattractant Protein-1 during the Course of Adipocyte Hypertrophy

Monocyte chemoattractant protein-1 (MCP-1), an important chemokine whose expression is increased during the course of obesity, plays a role in macrophage infiltration into obese adipose tissue. This study was designed to elucidate the role of mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in the induction of MCP-1 during the course of adipocyte hypertrophy. We examined the time course of MKP-1 and MCP-1 mRNA expression and extracellular signal-regulated kinase (ERK) phosphorylation in the adipose tissue from mice rendered mildly obese by a short term high fat diet. We also studied the role of MKP-1 in the induction of MCP-1 in 3T3-L1 adipocytes during the course of adipocyte hypertrophy. MCP-1 mRNA expression was increased, followed by ERK activation and down-regulation of MKP-1, an inducible dual specificity phosphatase to inactivate ERK, in the adipose tissue at the early stage of obesity induced by a short term high fat diet, when macrophages are not infiltrated. Down-regulation of MKP-1 preceded ERK activation and increased production of MCP-1 in 3T3-L1 adipocytes in vitro during the course of adipocyte hypertrophy. Adenovirus-mediated restoration of MKP-1 in hypertrophied 3T3-L1 adipocytes reduced the otherwise increased ERK phosphorylation, thereby leading to the significant reduction of MCP-1 mRNA expression. This study provides evidence that the down-regulation of MKP-1 is critical for increased production of MCP-1 during the course of adipocyte hypertrophy.

Targeting dual-specificity phosphatases: manipulating MAP kinase signalling and immune responses

Dual-specificity phosphatases (DUSPs) are a subset of protein tyrosine phosphatases, many of which dephosphorylate threonine and tyrosine residues on mitogen-activated protein kinases (MAPKs), and hence are also referred to as MAPK phosphatases (MKPs). The regulated expression and activity of DUSP family members in different cells and tissues controls MAPK intensity and duration to determine the type of physiological response. For immune cells, DUSPs regulate responses in both positive and negative ways, and DUSP-deficient mice have been used to identify individual DUSPs as key regulators of immune responses. From a drug discovery perspective, DUSP family members are promising drug targets for manipulating MAPK-dependent immune responses in a cell-type and disease-context-dependent manner, to either boost or subdue immune responses in cancers, infectious diseases or inflammatory disorders.

Anti-TNF Effects on Destructive Fibroblasts Depend on Mechanical Stress

Joint destruction in rheumatoid arthritis (RA) starts typically at sites of mechanically stressed inserts of the synovial membrane near the cartilage/bone border. In the therapy of RA, tumour necrosis factor (TNF) antagonists have rapidly emerged as a valuable class of anti-rheumatic agents that reduce joint destruction. The aim of this study was to investigate and profile genes involved in the interaction between articular movement and anti-TNF therapy in an in vitro model. Murine LS48 cells, an established substitute for invasive RA synovial fibroblasts, were cultured, stretched and/or treated with anti-TNF-alpha antibody for 24 h. RNA was isolated and gene transcript levels were determined using U74Av2 Affymetrix GeneChips to identify transcriptional events. Positive findings were verified by polymerase chain reaction (PCR). We identified 170 differentially regulated genes, including 44 of particular interest. Gene expression fell into different functional groups that can be explained by RA pathogenesis and experimental conditions. For 21 genes of the 44 of particular interest, regulation could be confirmed by real-time PCR. Remarkably, we found structural as well as functional genes differently regulated between stretched cells, anti-TNF-treated cells, and stretched cells treated with anti-TNF antibody. Additionally, we also found a large number of genes that are apparently not related to the experimental conditions. Mechanical exertion modulates gene expression and subsequently cellular response to anti-TNF therapy. Results in exerted cells correspond to current knowledge regarding RA pathogenesis and underline the relevance of our experimental approach. Finally, the central function of the interleukin-18 system in joint destruction could be confirmed by our findings.

Dual-specificity phosphatase 1 and serum/glucocorticoid-regulated kinase are downregulated in prostate cancer

Inactivation of tumor suppressor genes through deletion, mutation and epigenetic silencing has been shown to occur in cancer. In our study, we combined DNA demethylation and histone deacetylation inhibition treatments with suppression subtraction hybridization (SSH) and cDNA microarrays to identify potentially epigenetically downregulated genes in PC-3 prostate cancer cell line. We found 11 genes whose expression was upregulated after relieving epigenetic regulation. Expression of 3 genes [dual-specificity phosphatase 1 (DUSP1), serum/glucocorticoid regulated kinase (SGK) and spermidine/spermine N1-acetyltransferase (SAT)] was subsequently studied in clinical sample material using real-time quantitative RT-PCR and immunohistochemistry. The DUSP1 and SGK mRNA expression was lower in hormone-refractory prostate carcinomas compared to benign prostate hyperplasia (BPH) or untreated prostate carcinomas. BPH, normal prostate and high-grade prostate intraepithelial neoplasia (PIN) expressed high levels of DUSP1 and SGK proteins. Ninety-two percent and 48% of the prostate carcinomas showed almost complete lack of DUSP1 and SGK proteins, respectively, indicating common downregulation of these genes. The genomic bisulphite sequencing did not reveal dense hypermethylation in the promoter regions of either DUSP1 or SGK. In conclusion, the data suggest that downregulation of DUSP1 and SGK is an early event and could be important in the tumorigenesis of prostate cancer.

Targeting the ERK signaling pathway in cancer therapy

The extracellular signal-regulated kinase (ERK) signaling pathway is a major determinant in the control of diverse cellular processes such as proliferation, survival, differentiation and motility. This pathway is often up-regulated in human tumors and as such represents an attractive target for the development of anticancer drugs. Because of its multiple roles in the acquisition of a complex malignant phenotype, specific blockade of the ERK pathway is expected to result in not only an anti-proliferative effect but also in anti-metastatic and anti-angiogenic effects in tumor cells. Recently potent small-molecule inhibitors targeting the components of the ERK pathway have been developed. Among them, BAY 43-9006 (Raf inhibitor), and PD184352, PD0325901 and ARRY-142886 (MEK1/2 inhibitors) have reached the clinical trial stage. We briefly discuss the possibility that combination of ERK pathway inhibitors (cytostatic agents) and conventional anticancer drugs (cytotoxic agents) provides an excellent basis for the development of new chemotherapeutic strategies against cancer.

Suppressed MKP-1 is an independent predictor of outcome in patients with hepatocellular carcinoma

OBJECTIVE

An increase in the activity of mitogen-activated protein kinases (MAPKs) has been correlated with a more malignant phenotype in several tumor models in vivo. This study was designed to clarify the expression of MKP-1 in surgically resected hepatocellular carcinoma (HCC).

METHODS

We reviewed the cases of 77 patients who had undergone initial liver resection for HCC without preoperative treatment. Immunohistochemical analysis of MKP-1 was performed on paraffin-embedded tissues. The correlation between MKP-1 expression and clinical outcome was investigated.

RESULTS

Tumor cells were immunohistochemically stained for MKP-1 expression, and the same levels as in normal hepatocytes were detected in 66 (85%) of 77 HCC patients, being decreased in 11 (15%) HCCs. Decreased MKP-1 expression significantly correlated with serum alpha-fetoprotein levels and tumor size (p<0.05). The disease-free survival rates in MKP-1-negative and -positive patients were 0 and 31.0% at 5 years, respectively (p<0.01). The survival rates after a surgical resection in MKP-1-negative and -positive patients were 18.2 and 65.5% at 5 years, respectively (p<0.01).

CONCLUSIONS

The MKP-1 expression in HCC was an independent prognostic factor for outcome in HCC patients. In the future, it will be useful to explore whether the phosphatase expression might account for the response to HCC treatments targeting at MAPK activation.

Cooperation of ERK and SCFSkp2 for MKP-1 destruction provides a positive feedback regulation of proliferating signaling

The dual-specificity MAPK phosphatase MKP-1/CL100/DUSP1 is an inducible nuclear protein controlled by p44/42 MAPK (ERK1/2) in a negative feedback mechanism to inhibit kinase activity. Here, we report on the molecular basis for a novel positive feedback mechanism to sustain ERK activation by triggering MKP-1 proteolysis. Active ERK2 docking to the DEF motif (FXFP, residues 339-342) of N-terminally truncated MKP-1 in vitro initiated phosphorylation at the Ser(296)/Ser(323) domain, which was not affected by substituting Ala for Ser at Ser(359)/Ser(364). The DEF and Ser(296)/Ser(323) sites were essential for ubiquitin-mediated MKP-1 proteolysis stimulated by MKK1-ERK signaling in H293 cells, whereas the N-terminal domain and Ser(359)/Ser(364) sites were dispensable. ERK activation by serum increased the endogenous level of ubiquitinated phospho-Ser(296) MKP-1 and the degradation of MKP-1. Intriguingly, active ERK-promoted phospho-Ser(296) MKP-1 bound to SCF(Skp2) ubiquitin ligase in vivo and in vitro. Forced expression of Skp2 enhanced MKP-1 polyubiquitination and proteolysis upon ERK activation, whereas depletion of endogenous Skp2 suppressed such events. The kinetics of ERK signaling stimulated by serum correlated with the endogenous MKP-1 degradation rate in a Skp2-dependent manner. Thus, MKP-1 proteolysis can be achieved via ERK and SCF(Skp2) cooperation, thereby sustaining ERK activation.

Gene expression profiles associated with response to chemotherapy in epithelial ovarian cancers

PURPOSE

The goal of this study was to determine whether distinct gene expression profiles are associated with intrinsic and/or acquired chemoresistance in epithelial ovarian carcinoma.

EXPERIMENTAL DESIGN

Gene expression profiles were generated from 21 primary chemosensitive tumors and 24 primary chemo-resistant tumors using cDNA-based microarrays. Gene expression profiles of both groups of primary tumors were then compared with those of 15 ovarian carcinomas obtained following platinum-based chemotherapy ("post-chemotherapy" tumors). A theme discovery tool was used to identify functional categories of genes involved in drug resistance.

RESULTS

Comparison of primary chemosensitive and chemo-resistant tumors revealed differential expression of 85 genes (P < 0.001). Comparison of gene expression profiles of primary chemosensitive tumors and post-chemotherapy tumors revealed more robust differences with 760 genes differentiating the two groups (P < 0.001). In contrast, only 230 genes were differentially expressed between primary chemo-resistant and post-chemotherapy groups (P < 0.001). Common to both gene lists were 178 genes representing transcripts differentially expressed between post-chemotherapy tumors and all primary tumors irrespective of intrinsic chemosensitivity. The gene expression profile of post-chemotherapy tumors compared with that of primary tumors revealed statistically significant overrepresentation of genes encoding extracellular matrix-related proteins.

CONCLUSIONS

These data show that gene expression profiling can discriminate primary chemo-resistant from primary chemosensitive ovarian cancers. Gene expression profiles were also identified that correlate with states of intrinsic and acquired chemoresistance and that represent targets for future investigation and potential therapeutic interventions.

Gene expression profiling of differentiated thyroid neoplasms: diagnostic and clinical implications

PURPOSE

The purpose of this research was to identify novel genes that can be targeted as diagnostic and clinical markers of differentiated thyroid tumors.

EXPERIMENTAL DESIGN

Gene expression analysis using microarray platform was performed on 6 pathologically normal thyroid samples and 12 primary follicular and papillary thyroid neoplasms. Microarrays containing probes for 5,760 human full-length cDNAs were used for hybridization with total RNA from normal and tumor thyroid samples labeled with Cy3-dUTP and Cy5-dUTP, respectively. Scanned array images were recorded, and data analysis was performed. Selected sets of differentially expressed genes were analyzed using quantitative real-time reverse transcription-PCR for verification.

RESULTS

We identified 155 genes that differentiate histologically normal thyroid tissues from benign and malignant thyroid neoplasms. Of these 75 genes were differentiated between follicular neoplasms (adenoma and carcinoma) and the follicular variant of papillary carcinoma. Purely follicular neoplasms (adenomas and carcinomas) shared many genetic profiles, and only 43 genes were distinctly different between these tumors. Hierarchical cluster analysis also differentiated conventional papillary carcinoma from its follicular variant and follicular tumors. The differentially expressed genes were composed of members of cell differentiation, adhesion, immune response, and proliferation associated pathways. Quantitative real-time reverse transcription-PCR analysis of selected genes corroborated the microarray expression results.

CONCLUSIONS

Our study show the following: (1) differences in gene expression between tumor and nontumor bearing normal thyroid tissue can be identified, (2) a set of genes differentiate follicular neoplasm from follicular variant of papillary carcinoma, (3) follicular adenoma and carcinoma share many of the differentiated genes, and (4) gene expression differences identify conventional papillary carcinoma from the follicular variant.

Mitogen-activated protein kinase phosphatase-1 is overexpressed in non-small cell lung cancer and is an independent predictor of outcome in patients

PURPOSE

An increase in the activity of the mitogen-activated protein kinases (MAPKs) has been correlated with a more malignant phenotype in several tumor models in vitro and in vivo. A key regulatory mechanism of the MAPKs [extracellular signal-regulated kinase (ERK); c-jun NH(2)-terminal kinase (JNK); and p38] is the dual specificity phosphatase CL100, also called MAPK phosphatase-1 (MKP-1). This study was designed to examine the involvement of CL100/MKP-1 and stress-related MAPKs in lung cancer.

EXPERIMENTAL DESIGN

We assessed the expression of CL100/MKP-1 and the activation of the MAPKs in a panel of 18 human cell lines [1 primary normal bronchial epithelium, 8 non-small cell lung cancer (NSCLC), 7 small cell lung cancer (SCLC), and 2 carcinoids] and in 108 NSCLC surgical specimens.

RESULTS

In the cell lines, CL100/MKP-1 expression was substantially higher in NSCLC than in SCLC. P-ERK, P-JNK, and P-p38 were activated in SCLC and NSCLC, but the degree of their activation was variable. Immunohistochemistry in NSCLC resection specimens showed high levels of CL100/MKP-1 and activation of the three MAPK compared with normal lung. In univariate analysis, no relationship was found among CL100/MKP-1 expression and P-ERK, P-JNK, or P-p38. Interestingly, high CL100/MKP-1 expression levels independently predicted improved survival in multivariate analysis. JNK activation associated with T(1-2) and early stage, whereas ERK activation correlated with late stages and higher T and N. Neither JNK nor ERK activation were independent prognostic factors when studied for patient survival.

CONCLUSIONS

Our data indicate the relevance of MAPKs and CL100/MKP-1 in lung cancer and point at CL100/MKP-1 as a potential positive prognostic factor in NSCLC. Finally, our study supports the search of new molecular targets for lung cancer therapy within the MAPK signaling pathway.

Targeting the mitogen-activated protein kinase cascade to treat cancer

The RAS-mitogen activated protein kinase (MAPK) signalling pathway has long been viewed as an attractive pathway for anticancer therapies, based on its central role in regulating the growth and survival of cells from a broad spectrum of human tumours. Small-molecule inhibitors designed to target various steps of this pathway have entered clinical trials. What have we recently learned about their safety and effectiveness? Will the MAPK pathway prove amenable to therapeutic intervention?

Molecular characterization of uterine fibroids and its implication for underlying mechanisms of pathogenesis

OBJECTIVE

To identify genes involved in fibroid development by performing global expression profiling on tissues of normal myometrium and uterine leiomyoma origin using Affymetrix HG-U133A GeneChip microarrays.

DESIGN

Whole-genome analysis of mRNA levels in leiomyoma and normal myometrium tissue samples.

SETTING

University research laboratory.

PATIENT(S)

Eight patients of varying age and race undergoing surgery for symptomatic fibroids.

INTERVENTION(S)

After tissue collection of five tumors and five normals from human pathological specimens, labeled cRNA was generated and hybridized to the oligonucleotide-composed arrays.

MAIN OUTCOME MEASURE(S)

Quantification of transcript expression levels in uterine fibroids relative to normal myometrium.

RESULT(S)

Model-based expression analysis revealed that of the 22,500 transcripts represented on the arrays, 226 genes were found to be dysregulated by a > or =1.5-fold change between leiomyoma and normal myometrium. Moreover, our research identified many dysregulated apoptosis-related genes, of particular interest was TRAIL and Ask1, and also found numerous differentially expressed proliferation genes, including TGFB1, PDGFC, and two dual specificity phosphatases.

CONCLUSION(S)

These results indicate that these genes may play a significant role in the development of leiomyomas from normal uterine tissue. We hypothesize that the deregulation of apoptotic and proliferative processes is pivotal to fibroid development.

Expression profiling of non–small cell lung carcinoma identifies metastatic genotypes based on lymph node tumor burden

OBJECTIVE

This study hypothesized that non-small cell lung carcinoma cells from primary tumors isolated by laser capture microdissection would exhibit gene expression profiles associated with graded lymph node metastatic cell burden.

METHODS

Non-small cell lung carcinoma tumors (n = 15) were classified on the basis of nodal metastatic cell burden by 2 methods, obtaining 3 groups: no metastasis, micrometastasis, and overt metastasis. We then performed microarray analysis on microdissected primary tumor cells and identified gene expression profiles associated with graded nodal tumor burden using a correlation-based selection algorithm coupled with cross-validation analysis. Hierarchical clustering showed the regrouping of tumor specimens; the classification inference was assessed with Fisher's exact test. We verified data for certain genes by using another independent assay.

RESULTS

The 15 specimens clustered into 3 groups: cluster A predominated in specimens with overt nodal metastasis; cluster B had more specimens with nodal micrometastases; and cluster C included only specimens without nodal metastases. Cluster assignment was based on a validated 75-gene discriminatory subset. Notably, genes not previously associated with positive non-small cell lung carcinoma lymph node status were encountered in the profiling analysis.

CONCLUSIONS

Microdissection, combined with microarray analysis, is a potentially powerful method to characterize the molecular profile of tumor cells. The 75-gene expression profiles representative of clusters A and B may define genotypes prone to metastasize. Overall, the 3 groups of tumor specimens clustered separately, suggesting that this approach may identify graded metastatic propensity. Further, genes singled out in clustering may yield insights into underlying metastatic mechanisms and may represent new therapeutic targets.

The transcriptosomal response of human A549 lung cells to a hydrogen peroxide-generating system: relationship to DNA damage, cell cycle arrest, and caspase activation

Intracellular oxidative stress is a dynamic situation characterized by the accumulation of reactive oxygen metabolites, such as hydrogen peroxide. This is traditionally associated with both macromolecular damage and adaptive changes in gene expression, aimed at preventing cellular demise. However, the overall extent of such genetic changes is not well characterized. Here we present a comprehensive analysis of altered mRNA profiles in human A549 type II lung epithelial cells in response to hydrogen peroxide, at concentrations failing to induce necrotic toxicity. The results of an Affymetrix-based screen of the steady-state levels of mRNAs for several thousand genes revealed a complex pattern of transcriptional and/or posttranscriptional response to oxidative stress, which can be functionally related to both the oxidation and repair of damaged DNA, the induction and permanency of cell cycle arrest, and caspase-3 activation. Many of the genetic events can be related to activation of the p53/p21 pathway, but many other novel inductions and suppressions were detected, revealing the intricacy of the response. The data also disclosed a potential interaction between hydrogen peroxide treatment and increased sensitivity to cell killing by TRAIL, which could be functionally confirmed at the level of induction of caspase-3 activity.

Biologic directed therapies in gynecologic oncology

Evaluation of the genome has provided information concerning the origins of many human diseases, including cancer. Identification of the genes and their protein products has greatly increased our understanding of this complex disease. A variety of cellular processes and pathways stimulate cellular proliferation or inhibit cell death. Many of these pathways are targets for novel therapeutic agents. These agents will usher in a new era of biologically targeted therapeutics. In gynecologic oncology, we are just beginning to investigate these new biologic agents. An appreciation and understanding of these pathways of growth deregulation in gynecologic cancers provide an opportunity for many clinically relevant therapies. This review summarizes the emerging biologic therapies with an emphasis on their relevance to gynecologic malignancies.

Expression profiling of CC531 colon carcinoma cells reveals similar regulation of beta-catenin target genes by both butyrate and aspirin

The CC531 cell line has been widely used to study different aspects of tumor growth and metastasis and provides an excellent experimental platform to develop novel antitumor strategies. To characterize the CC531 model at the molecular level, we screened for mutations in genes covering important signal-transduction pathways that are known to play major roles during colon carcinogenesis, the wnt and the ki-ras signaling pathways. We found both a prototypic beta-catenin (Ctnnb1) mutation (Thr(41)Ile) and a ki-ras (G12D) mutation, providing unambiguous evidence for the constitutive activation of these pathways in CC531 cells. We further established comprehensive gene expression profiles of CC531 cells and investigated the molecular response to 2 antitumor drugs, butyrate and aspirin. Using oligonucleotide microarrays, we screened the expression levels of 7,700 genes and identified a total of 398 genes whose expression was significantly changed upon treatment with butyrate. When using aspirin, 121 genes were significantly altered. Interestingly, 36 genes were regulated by both butyrate and aspirin and 35 of them were regulated in the same direction. We found 7 differentially expressed genes, cyclin D1, cyclin E, c-myc, Fosl1, c-fos, Cd44 and follistatin, which are known targets of the beta-catenin and/or the ras pathway. In all cases, butyrate and aspirin reversed the changes in expression normally found in response to active signaling of these oncogenic pathways. The microarray data are available (http://ncbi.nlm.nih.gov/geo/).

ERK1/2 achieves sustained activation by stimulating MAPK phosphatase-1 degradation via the ubiquitin-proteasome pathway

Sustained extracellular signal-regulated kinase 1/2 (ERK1/2) activation does not always correlate with its upstream Ras-Raf-mitogen-activated protein kinase kinase 1/2 (MKK1/2) signal cascade in cancer cells, and the mechanism remains elusive. Here we report a novel mechanism by which sustained ERK1/2 activation is established. We demonstrate that Pb(II), a carcinogenic metal, persistently induces ERK1/2 activity in CL3 human lung cancer cells and that Ras-Raf-MKK1/2 signaling cannot fully account for such activation. It is intriguing that Pb(II) treatment reduces mitogen-activated protein kinase phosphatase 1 (MKP-1) protein levels in time- and dose-dependent manners, which correlates with sustained ERK1/2 activation, and that Pb(II) also induces mRNA and de novo protein synthesis of MKP-1. In Pb(II)-treated cells, MKP-1 is polyubiquitinated, and proteasome inhibitors markedly alleviate the ubiquitination and degradation of MKP-1. Inhibiting the Pb(II)-induced ERK1/2 activation by PD98059 greatly suppresses MKP-1 ubiquitination and degradation. It is remarkable that constitutive activation of MKK1/2 triggers endogenous MKP-1 ubiquitination and degradation in various mammalian cell lines. Furthermore, expression of functional MKP-1 decreases ERK1/2 activation and the c-Fos protein level and enhances cytotoxicity under Pb(II) exposure. Taken together, these results demonstrate that activated ERK1/2 can trigger MKP-1 degradation via the ubiquitin-proteasome pathway, thus facilitating long-term activation of ERK1/2 against cytotoxicity.

Early events in ovarian epithelial carcinogenesis: progress and problems in experimental approaches

The etiology and early events in the progression of epithelial ovarian carcinomas are among the least understood of all major human malignancies. There are no adequate means for early detection of these neoplasms and, as a result, they are usually diagnosed in late stages. The purpose of this review is to point out some of the peculiar problems and limitations that have hampered progress in ovarian carcinogenesis research and to summarize new approaches and recent advances in our understanding of this process. The review first presents an overview of the properties of the ovarian surface epithelium (OSE) which is thought to be the source of epithelial ovarian carcinomas, followed by a discussion of recent research based on human OSE. This includes sections on methodology for the attainment and study of OSE, investigations of OSE from women with predisposing mutations, and attempts to convert normal OSE to malignancy. This overview is followed by a discussion of the contributions, potential, and limitations of animal models. The knowledge gained by these approaches will likely lead to improvements in our ability to prevent, diagnose, and treat ovarian cancer.