Constitutive phosphorylation of eps8 in tumor cell lines: relevance to malignant transformation

Reframing a debate in chiropractic

The chiropractic profession is 125 years old and has evolved a culture beset with internal conflict. The internal ructions have been particularly noticeable during the last 20 years. The recent resignation of the entire World Federation of Chiropractic Research Committee has again focussed the conflicting views and goals of the “wellness” and “evidence” factions within the profession. These polarising viewpoints are worsening to the degree that there are calls for the profession to break into two separate entities. Key to the recognition of the differences within the profession is the recognition of title for particular sub populations of patients presenting to chiropractors. For many of the sub populations such as sport or paediatrics there has grown appropriate post professional specialist educational training sometimes leading to a protected title. However, this is not occurring in that group of practitioners that choose to focus on wellness care. A recommendation is made that wellness chiropractic be viewed as a post professional specialty program within chiropractic, as it is in medicine and elsewhere, and that recognition follow after appropriate post professional educational programs have been completed, as is customary in the other special interest groups. In order to do so, consensus will be required from all stakeholders within the profession on the level, scope and depth of such programs. Furthermore, it is possible that different jurisdictions around the world may require different post graduate educational levels based on local competitive, legal and professional circumstances. In such cases, transitioning to the higher level over a period of time may be undertaken. Recognition of the wellness specialty by the profession would allow for vertical integration with other healthcare providers as well as help bridge a gap between the entrepreneur and academic groups that would be responsible for creating these programs at tertiary education institutions. Finally, should these programs acquire evidence to underpin them, a process that would be taught within the programs, it is likely that recognition of an extended scope of practice would occur increasing the appeal of chiropractic to the public.

Effects and mechanisms of Eps8 on the biological behaviour of malignant tumours (Review)

Epidermal growth factor receptor pathway substrate 8 (Eps8) was initially identified as the substrate for the kinase activity of EGFR, improving the responsiveness of EGF, which is involved in cell mitosis, differentiation and other physiological functions. Numerous studies over the last decade have demonstrated that Eps8 is overexpressed in most ubiquitous malignant tumours and subsequently binds with its receptor to activate multiple signalling pathways. Eps8 not only participates in the regulation of malignant phenotypes, such as tumour proliferation, invasion, metastasis and drug resistance, but is also related to the clinicopathological characteristics and prognosis of patients. Therefore, Eps8 is a potential tumour diagnosis and prognostic biomarker and even a therapeutic target. This review aimed to describe the structural characteristics, role and related molecular mechanism of Eps8 in malignant tumours. In addition, the prospect of Eps8 as a target for cancer therapy is examined.

EPS8 phosphorylation by Src modulates its oncogenic functions

Background

EPS8 is a scaffolding protein that regulates proliferation, actin dynamics and receptor trafficking. Its expression is increased in cancer, enhancing mitogenesis, migration and tumorigenesis. Src phosphorylates EPS8 at four tyrosine residues, although the function is unknown. Here we investigated the pro-oncogenic role of EPS8 tyrosine phosphorylation at Src target sites in HNSCC.

Methods

Plasmids expressing EPS8 Src-mediated phosphorylation site mutants (Y485F, Y525F, Y602F, Y774F and all four combined [FFFF]) were expressed in cells containing a normal endogenous level of EPS8. In addition, cells were treated with dasatinib to inhibit Src activity. EPS8 downstream targets were evaluated by western blotting. Wound closure, proliferation, immunofluorescence and tumorgenicity assays were used to investigate the impact of phenylalanine mutations on EPS8 biological functions.

Results

FOXM1, AURKA, and AURKB were decreased in cells expressing FFFF- and Y602F-EPS8 mutants, while cells harbouring the Y485F-, Y525F- and Y774F-EPS8 mutants showed no differences compared to controls. Consistent with this, dasatinib decreased the expression of EPS8 targets. Moreover, Y602F- and FFFF-EPS8 mutants reduced mitogenesis and motility. Strikingly though, FFFF- or Y602F-EPS8 mutants actually promoted tumorigenicity compared with control cells.

Conclusions

Phosphorylation of EPS8 at Y602 is crucial for signalling to the cell cycle and may provide insight to explain reduced efficacy of dasatinib treatment.

EPS8 is a Potential Oncogene in Glioblastoma

Purpose

In this study, we investigated the expression and function of Epidermal growth factor receptor kinase substrate 8 (EPS8) in glioblastoma (GBM), and further explored the underlying mechanisms that regulate it.

Patients and methods

The expression and potential mechanisms of EPS8 in GBM were evaluated through multiple online public databases. The expression level EPS8 in GBM tissues and cell lines were detected by immunohistochemical staining and Western blot. Then, the prognosis of EPS8 and GBM patients were analyzed. Loss-of-function experiments were conducted to determine the role of EPS8 for the biological behavior of GBM cells. In addition, the tumorigenic ability of nude mice was tested in vivo.

Results

EPS8 is highly expressed in GBM tissues and indicates poor patient prognosis. In cell experiments, EPS8 can promote the proliferation, migration and invasion of GBM cells. In vivo, EPS8 promotes tumor formation in nude mice. EPS8 can activate the PI3K/Akt signaling pathway to function.

Conclusion

EP8S plays a role in the development of GBM and may be a potential therapeutic target for GBM.

Novel Nuclear Partnering Role of EPS8 With FOXM1 in Regulating Cell Proliferation

One hallmark of cancer cells is sustaining proliferative signaling that leads to uncontrolled cell proliferation. Both the Forkhead box (FOX) M1 transcription factor and the Epidermal Growth Factor (EGF) receptor Pathway Substrate 8 (EPS8) are known to be activated by mitogenic signaling and their levels upregulated in cancer. Well-known to regulate Rac-mediated actin remodeling at the cell cortex, EPS8 carries a nuclear localization signal but its possible nuclear role remains unclear. Here, we demonstrated interaction of FOXM1 with EPS8 in yeast two-hybrid and immunoprecipitation assays. Immunostaining revealed co-localization of the two proteins during G2/M phase of the cell cycle. EPS8 became nuclear localized when CRM1/Exportin 1-dependent nuclear export was inhibited by Leptomycin B, and a functional nuclear export signal could be identified within EPS8 using EGFP-tagging and site-directed mutagenesis. Downregulation of EPS8 using shRNAs suppressed expression of FOXM1 and the FOXM1-target CCNB1, and slowed down G2/M transition in cervical cancer cells. Chromatin immunoprecipitation analysis indicated recruitment of EPS8 to the CCNB1 and CDC25B promoters. Taken together, our findings support a novel partnering role of EPS8 with FOXM1 in the regulation of cancer cell proliferation and provides interesting insight into future design of therapeutic strategy to inhibit cancer cell proliferation.

Eps8 expression is significantly lower in p16+ head and neck squamous cell carcinomas (HNSCCs) compared with p16- HNSCCs

In vitro head and neck cancer studies have demonstrated that epidermal growth factor receptor kinase substrate 8 (Eps8) overexpression contributes to squamous carcinogenesis. Oral squamous cell carcinoma studies have correlated Eps8 expression with metastatic disease and poor prognosis. Head and neck squamous cell carcinoma (HNSCC) studies comparing its expression by anatomic site or in in vivo regional metastases have not been performed. In this study, we compared Eps8 expression in HNSCCs arising in the oral cavity (OCSCC) and oropharynx (OPSCC) along with their corresponding regional lymph node (LN) metastases. We then correlated our findings with clinicopathologic data including tumor-node-metastasis stage, p16 status, age, sex, and smoking and alcohol history. Eps8 immunohistochemistry was performed on 69 archived OCSCCs and OPSCCs, and 24 paired and 4 unpaired LNs. Expression was scored from 0 to 3. Eps8 expression was detected in 49% of combined OCSCC and OPSCC cases. We found that expression correlated with advanced tumor stage (P = .022) and p16 status (P = .032) but not with anatomic site. Notably, p16⁺ HNSCCs had significantly lower Eps8 expression than p16^- HNSCCs. No significant difference was observed between primary HNSCCs and their corresponding metastatic LNs. Neither p16 status nor anatomic site influenced Eps8 expression in regional LN metastases. In conclusion, our data offer in vivo support that, in HNSCCs, Eps8 is involved in tumor invasion but not necessarily the development of regional LN metastasis. The association between low Eps8 expression and p16⁺ HNSCCs suggests that alternative signaling pathways may be used for their tumorigenesis.

PTK6 Localized at the Plasma Membrane Promotes Cell Proliferation and MigratiOn Through Phosphorylation of Eps8

Protein tyrosine kinase 6 (PTK6; also known as Brk) is closely related to the Src family kinases, but lacks a membrane-targeting myristoylation signal. Sublocalization of PTK6 at the plasma membrane enhances its oncogenic potential. To understand the mechanism(s) underlying the oncogenic property of plasma---membrane-associated PTK6, proteins phosphorylated by membrane-targeted myristoylated PTK6 (Myr-PTK6) were enriched and analyzed using a proteomics approach. Eps8 which was identified by this method is phosphorylated by Myr-PTK6 in HEK293 cells. Mouse Eps8 expressed in HEK293 cells is phosphorylated by Myr-PTK6 at residues Tyr497, Tyr524, and Tyr534. Compared to wild-type Eps8 (Eps8 WT), the phosphorylation-defective 3YF mutant (Eps8 3YF) reverts the increased proliferation, migration, and phosphorylation of ERK and FAK mediated by Eps8 WT in HEK293 cells overexpressing PTK6. PTK6 knockdown in T-47D breast cancer cells decreased EGF-induced phosphorylation of Eps8. Endogenous PTK6 phosphorylates ectopically expressed Eps8 WT, but not Eps8 3YF mutant, in EGF-stimulated T-47D cells. The EGF-induced Eps8 phosphorylation enhances activation of ERK and FAK, cell adhesion, and anchorage-independent colony formation in T-47D cells, but not in the PTK6-knokdown T-47D cells. These results indicate that plasma-membrane-associated PTK6 phosphorylates Eps8, which promotes cell proliferation, adhesion, and migration and, thus, tumorigenesis. J. Cell. Biochem. 118: 2887-2895, 2017. © 2017 Wiley Periodicals, Inc.

Identification of HLA‑A*1101‑restricted cytotoxic T lymphocyte epitopes derived from epidermal growth factor pathway substrate number 8

Epidermal growth factor receptor pathway substrate 8 (EPS8) is critical in the proliferation, progression and metastasis of solid and hematological types of cancer, and thus constitutes an ideal target for cancer immunotherapy. The present study aimed to identify human leukocyte antigen (HLA)‑A*1101‑restricted cytotoxic T lymphocyte (CTL) epitopes from EPS8 and characterize their immunotherapeutic efficacy in vitro. Two computer‑based algorithms were used to predict native EPS8 epitopes with potential high binding affinity to the HLA‑A*1101 molecule, which is the HLA‑A allele with the highest frequency in the Chinese population. The peptide‑induced cytokine production from the CTLs was examined using enzyme‑linked immunosorbent spot analysis. The cytotoxic effects on cancer cells by CTLs primed with the identified peptides were examined using flow cytometry. A total of five peptides, designated as P380, P70, P82, P30 and P529, presented with high affinity towards the HLA‑A*1101 molecule. In response to stimulation by these five peptides, enhanced secretion of interferon‑γ from the CTLs and increased cytolytic capabilities of the CTLs toward cancer cells were noted, with the most potent effects observed from the P380 peptide. Taken together, the present study identified five potential CTL epitopes from EPS8. Among these, P380 presented with the highest therapeutic efficacy in vitro. These peptides may benefit the development of EPS8‑based immunotherapy for the treatment of HLA‑A*1101‑positive hematological malignancies.

Epidermal growth factor receptor kinase substrate 8 promotes the metastasis of cervical cancer via the epithelial-mesenchymal transition

Epidermal growth factor receptor pathway substrate 8 (Eps8) has been identified as a novel substrate for epidermal growth factor receptor (EGFR) kinase and is involved in EGFR-mediated signaling pathways correlated with tumorigenesis, proliferation and metastasis in various cancer types. However, the precise role of Eps8 in cervical cancer metastasis remains to be elucidated. Immunohistochemistry revealed that Eps8 was significantly increased in cervical cancer specimens compared with squamous intraepithelial lesion and normal cervical tissues. Additionally, it was revealed that Eps8 expression not only correlated with cervical cancer progression, but also exhibited a close correlation with the epithelial-mesenchymal transition (EMT) markers, E-cadherin and vimentin. Furthermore, the present study focused predominantly on the EMT-associated role of Eps8 in the EMT, migration and invasion of cervical cancer cells. Eps8-short hairpin (sh) RNA was transfected into HeLa and SiHa cells to deplete its expression, and reverse transcription-quantitative polymerase chain reaction and western blot analyses were performed to confirm Eps8-knockdown and to investigate the influence of Eps8 on EMT markers. The present findings have revealed that Eps8 silencing led to the upregulation of the epithelial marker E-cadherin, while expression of the mesenchymal marker vimentin and the transcription factor snail was decreased at both mRNA and protein expression levels. Transwell cell migration and Matrigel invasion assays showed that downregulation of Eps8 significantly inhibited cell migration and invasion of HeLa and SiHa cells. Taken together, these results suggested that Eps8 promotes cervical cancer metastasis by orchestrating the EMT.

Identification of human leukemia antigen A*0201-restricted epitopes derived from epidermal growth factor pathway substrate number 8

T-cell-mediated immunotherapy of hematological malignancies requires selection of targeted tumor-associated antigens and T-cell epitopes contained in these tumor proteins. Epidermal growth factor receptor pathway substrate 8 (EPS8), whose function is pivotal for tumor proliferation, progression and metastasis, has been found to be overexpressed in most human tumor types, while its expression in normal tissue is low. The aim of the present study was to identify human leukemia antigen (HLA)-A*0201-restricted epitopes of EPS8 by using a reverse immunology approach. To achieve this, computer algorithms were used to predict HLA-A*0201 molecular binding, proteasome cleavage patterns as well as translocation of transporters associated with antigen processing. Candidate peptides were experimentally validated by T2 binding affinity assay and brefeldin-A decay assay. The functional avidity of peptide-specific cytotoxic T lymphocytes (CTLs) induced from peripheral blood mononuclear cells of healthy volunteers were evaluated by using an enzyme-linked immunosorbent spot assay and a cytotoxicity assay. Four peptides, designated as P455, P92, P276 and P360, had high affinity and stability of binding towards the HLA-A*0201 molecule, and specific CTLs induced by them significantly responded to the corresponding peptides and secreted IFN-γ. At the same time, the CTLs were able to specifically lyse EPS8-expressing cell lines in an HLA-A*0201-restricted manner. The present study demon-strated that P455, P92, P276 and P360 were CTL epitopes of EPS8, and were able to be used for epitope-defined adoptive T-cell transfer and multi-epitope-based vaccine design.

Dynamic filopodia are required for chemokine-dependent intracellular polarization during guided cell migration in vivo

Cell migration and polarization is controlled by signals in the environment. Migrating cells typically form filopodia that extend from the cell surface, but the precise function of these structures in cell polarization and guided migration is poorly understood. Using the in vivo model of zebrafish primordial germ cells for studying chemokine-directed single cell migration, we show that filopodia distribution and their dynamics are dictated by the gradient of the chemokine Cxcl12a. By specifically interfering with filopodia formation, we demonstrate for the first time that these protrusions play an important role in cell polarization by Cxcl12a, as manifested by elevation of intracellular pH and Rac1 activity at the cell front. The establishment of this polarity is at the basis of effective cell migration towards the target. Together, we show that filopodia allow the interpretation of the chemotactic gradient in vivo by directing single-cell polarization in response to the guidance cue.

DOI:http://dx.doi.org/10.7554/eLife.05279.001

Some of the cells in an animal embryo have to migrate long distances to reach their final positions; that is to say, to reach the locations where they will participate in the formation of tissues and organs. The migration of cells is also important throughout the entire lifespan of an animal. White blood cells, for example, must be able to move within tissues to search for and fight infections as well as to detect and remove abnormal cells.

The front end of a migrating cell typically protrudes. The back of the cell is then pulled and detaches, which allows the whole cell to move forward. Migrating cells generate thin finger-like projections known as filopodia that have been suggested to help the cell sense their external environments and follow chemical cues. It is not clear what happens to a migrating cell in a living organism if the formation of its filopodia is impaired, or even how filipodia help the normal migration of cells in animals.

To define how filopodia help to guide migrating cells in an animal, Meyen et al. analyzed the migration of cells called ‘primordial germ cells’ (or PGCs) in zebrafish. These cells form very early on in development of a zebrafish embryo at a position that is far away from their final location (in the testes or ovaries where they will go on to form sperm or egg cells respectively). Meyen et al. revealed that cells that are exposed to the guidance cue (a protein called a chemokine) form more filopodia at their front compared to their rear. The filopodia formed at the cell front also extend and retract more frequently.

Meyen et al. further observed that the specific chemokine that guides the cells can bind to the filopodia and enter the cell. This leads to a signal inside the cell that tells the cell to move in the direction where more of the chemokine is found. Indeed, altering the distribution and number of filopodia around the cell's edge decreases the ability of the primordial germ cells to reach their targets. Together, this work shows that the filopodia at the front end of cells are required for sensing the chemokines that guide cell movement.

Further work is required to understand the mechanism that determines the distribution of filopodia on the surface of migrating cells, and the role of chemokines in the process. Moreover, this work may also be relevant for understanding the migration of cancer cells, because several types of cancer can invade new tissues by following directional cues including chemokines.

DOI:http://dx.doi.org/10.7554/eLife.05279.002

Human intersectin 2 (ITSN2) binds to Eps8 protein and enhances its degradation

Participates in actin remodeling through Rac and receptor endocytosis via Rab5. Here, we used yeast two-hybrid system with Eps8 as bait to screen a human brain cDNA library. ITSN2 was identified as the novel binding factor of Eps8. The interaction between ITSN2 and Eps8 was demonstrated by the in vivo co-immunoprecipitation and colocalization assays and the in vitro GST pull-down assays. Furthermore, we mapped the interaction domains to the region between amino acids 260-306 of Eps8 and the coiled-coil domain of ITSN2. In addition, protein stability assays and immunofluorescence analysis showed ITSN2 overexpression induced the degradation of Eps8 proteins, which was markedly alleviated with the lysosome inhibitor NH4Cl treatment. Taken together, our results suggested ITSN2 interacts with Eps8 and stimulates the degradation of Eps8 proteins.

Eps8 regulates cellular proliferation and migration of breast cancer

The role of Eps8 in human breast cancer was studied, and we found that Eps8 was overexpressed in >60% of human breast cancer samples compared with adjacent normal breast tissues by immunohistochemical analysis. Eps8 was highly expressed in the highly invasive breast cancer cell line MDA-MB‑231 compared with the weakly invasive breast cancer cell lines MCF7 and MDA-MB‑468. MCF7 cell line stably expressing Eps8 was established by G418 screening, and the ectopic expression of Eps8 enhanced MCF7 breast cancer cell growth and survival as assessed by MTT analysis, cell viability and liquid colony formation, whereas the lentiviral expression of Eps8 shRNA in MDA-MB‑231 cells resulted in a significant reduction in cellular growth and proliferation in vitro and in vivo. Furthermore, Eps8 knockdown inhibited breast cancer cell migration in wound healing assays, decreased the number and size of EGF-induced filopodia and increased the sensitivity of breast cancer cells to cisplatin analyzed by MTT assays. Eps8 knockdown decreased the levels of phosphorylated extracellular signal-regulated protein kinase (ERK) and MMP9 but increased p53. Moreover, Eps8 knockdown suppressed a partial EMT-like transition and showed a significant increase in E-cadherin and decrease in N-cadherin and vimentin. These results suggest that Eps8 is overexpressed in human breast cancers, possibly by regulating ERK signaling, MMP9, p53 and EMT-like transition to affect breast cancer cell growth, migration and invasion. Therefore, Eps8 might represent a novel potential target in human breast cancer therapy.

Novel oncoprotein EPS8: a new target for anticancer therapy

EPS8 was first identified as a tyrosine kinase substrate, that plays a role in EGFR-mediated mitogenic signaling. Recent research has shown that EPS8 is overexpressed in most types of cancer, for example breast cancer, colon cancer, cervical cancer and even hematologic malignancies. EPS8 is involved in many signaling pathways related to tumorigenesis, proliferation, migration and metastasis, and is a biomarker for poor prognosis of cancer patients. This review aims to provide a comprehensive picture of the role of EPS8 in cellular processes and its significance to tumorigenesis. Furthermore, this review focuses on the potential role of EPS8 as a therapeutic cancer target.

EPS8 inhibition increases cisplatin sensitivity in lung cancer cells

Cisplatin, a commonly used chemotherapeutic, is associated with ototoxicity, renal toxicity and neurotoxicity, thus identifying means to increase the therapeutic index of cisplatin may allow for improved outcomes. A SNP (rs4343077) within EPS8, discovered through a genome wide association study of cisplatin-induced cytotoxicity and apoptosis in lymphoblastoid cell lines (LCLs), provided impetus to further study this gene. The purpose of this work was to evaluate the role of EPS8 in cellular susceptibility to cisplatin in cancerous and non-cancerous cells. We used EPS8 RNA interference to determine the effect of decreased EPS8 expression on LCL and A549 lung cancer cell sensitivity to cisplatin. EPS8 knockdown in LCLs resulted in a 7.9% increase in cisplatin-induced survival (P = 1.98 × 10(-7)) and an 8.7% decrease in apoptosis (P = 0.004) compared to control. In contrast, reduced EPS8 expression in lung cancer cells resulted in a 20.6% decrease in cisplatin-induced survival (P = 5.08 × 10(-5)). We then investigated an EPS8 inhibitor, mithramycin A, as a potential agent to increase the therapeutic index of cisplatin. Mithramycin A decreased EPS8 expression in LCLs resulting in decreased cellular sensitivity to cisplatin as evidenced by lower caspase 3/7 activation following cisplatin treatment (42.7% ± 6.8% relative to control P = 0.0002). In 5 non-small-cell lung carcinoma (NSCLC) cell lines, mithramycin A also resulted in decreased EPS8 expression. Adding mithramycin to 4 NSCLC cell lines and a bladder cancer cell line, resulted in increased sensitivity to cisplatin that was significantly more pronounced in tumor cell lines than in LCL lines (p<0.0001). An EGFR mutant NSCLC cell line (H1975) showed no significant change in sensitivity to cisplatin with the addition of mithramycin treatment. Therefore, an inhibitor of EPS8, such as mithramycin A, could improve cisplatin treatment by increasing sensitivity of tumor relative to normal cells.

A graph kernel approach for alignment-free domain-peptide interaction prediction with an application to human SH3 domains

MOTIVATION

State-of-the-art experimental data for determining binding specificities of peptide recognition modules (PRMs) is obtained by high-throughput approaches like peptide arrays. Most prediction tools applicable to this kind of data are based on an initial multiple alignment of the peptide ligands. Building an initial alignment can be error-prone, especially in the case of the proline-rich peptides bound by the SH3 domains.

RESULTS

Here, we present a machine-learning approach based on an efficient graph-kernel technique to predict the specificity of a large set of 70 human SH3 domains, which are an important class of PRMs. The graph-kernel strategy allows us to (i) integrate several types of physico-chemical information for each amino acid, (ii) consider high-order correlations between these features and (iii) eliminate the need for an initial peptide alignment. We build specialized models for each human SH3 domain and achieve competitive predictive performance of 0.73 area under precision-recall curve, compared with 0.27 area under precision-recall curve for state-of-the-art methods based on position weight matrices. We show that better models can be obtained when we use information on the noninteracting peptides (negative examples), which is currently not used by the state-of-the art approaches based on position weight matrices. To this end, we analyze two strategies to identify subsets of high confidence negative data. The techniques introduced here are more general and hence can also be used for any other protein domains, which interact with short peptides (i.e. other PRMs).

AVAILABILITY

The program with the predictive models can be found at http://www.bioinf.uni-freiburg.de/Software/SH3PepInt/SH3PepInt.tar.gz. We also provide a genome-wide prediction for all 70 human SH3 domains, which can be found under http://www.bioinf.uni-freiburg.de/Software/SH3PepInt/Genome-Wide-Predictions.tar.gz.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Eps8 vaccine exerts prophylactic antitumor effects in a murine model: a novel vaccine for breast carcinoma

Cancer vaccines are an effective way to prevent the occurrence of cancer. Epidermal growth factor receptor pathway substrate 8 (Eps8) is a novel tumor-associated antigen, which is overexpressed in the majority of tumor types. In the present study, the Eps8 protein was cloned and characterized, and its feasibility as an antitumor agent in murine breast carcinoma was investigated. The results revealed that the Eps8 protein increased the secretion of interleukin (IL)-12 in the culture supernatant of dendritic cells (DCs). The Eps8 protein‑pulsed DCs induced significant cytotoxic T lymphocyte (CTL) responses, T-cell proliferation and a higher level of interferon (IFN)-γ in the culture supernatant of the splenocytes ex vivo. Additionally, when the mice were immunized with the Eps8 vaccine, this resulted in a regression of 4T1 breast tumors and significantly prolonged survival time in the tumor‑bearing mice compared with that in the phosphate-buffered saline (PBS) control group. The Eps8 vaccine induced higher CTL responses in the splenocytes of mice vaccinated against the 4T1 cells; the ratio of CD4+/CD8+ T cells was increased in the Eps8 group; and the percentage of CD4+CD25+ FoxP3+ regulatory T (Treg) cells in the Eps8 group was significantly lower compared with that of the PBS group. The results suggested that the Eps8 vaccine was able to stimulate antitumor effects against 4T1 breast cancer cells in vitro and in vivo, and it may provide a potential immunotherapeutic agent for the treatment of breast cancer.

Novel binding partners and differentially regulated phosphorylation sites clarify Eps8 as a multi-functional adaptor

Eps8 is involved in both cell signalling and receptor trafficking. It is a known phosphorylation substrate for two proteins involved in the fibroblast growth factor receptor (FGFR) signalling pathway: the receptor itself and Src. Here we report a differential proteomic analysis of Eps8 aimed to identify specific FGFR and Src family kinase dependent phosphosites and co-associated phosphodependent binding partners. This study reveals a total of 22 Eps8 pTyr and pSer/Thr phosphorylation sites, including those that are dependent on Src family and FGFR kinase activity. Peptide affinity purification of proteins that bind to a selection of the pTyr phosphosites has identified a range of novel Eps8 binding partners including members of the intracellular vesicle trafficking machinery (clathrin and AP-2), proteins which have been shown to regulate activated receptor trafficking (NBR1 and Vav2), and proteins involved in receptor signalling (IRS4 and Shp2). Collectively this study significantly extends the understanding of Eps8 post-translational modification by regulated phosphorylation, identifies novel Eps8 binding partners implicated in receptor trafficking and signalling, and confirms the functions of Eps8 at the nexus of receptor signalling and vesicular trafficking.

Eps8 promotes cellular growth of human malignant gliomas

Eps8 was initially identified as a substrate of the epidermal growth factor receptor. Overexpression of Eps8 leads to increased mitogenic signaling and malignant transformation. However, little is known concerning the importance of Eps8 in human gliomas. In this study, we found that Eps8 was overexpressed in 56.6% of human gliomas (WHO grades III and IV) compared with adjacent normal brain tissues by immunohistochemical analysis. The U251 human glioma cell line stably expressing Eps8 was established by G418 screening, and the ectopic expression of Eps8 enhanced U251 glioma cell growth and survival by cell survival, MTT and liquid colony formation assays. By contrast, the lentiviral expression of Eps8 siRNA in SHG-44 cells resulted in a significant reduction in cellular growth and proliferation. Furthermore, Eps8 modulated the levels of phosphorylated extracellular signal-regulated protein kinase (ERK), phosphorylated serine-threonine protein kinase Akt and β-catenin expression in glioma cell lines and tissues. These results suggest that Eps8 is overexpressed in human gliomas, and affects glioma cell growth possibly by regulating ERK and Akt/β-catenin signaling. Therefore, Eps8 may represent a novel potential target in human glioma therapy.

Differential roles of EPS8 in carcinogenesis: Loss of protein expression in a subset of colorectal carcinoma and adenoma

AIM: To analyze the epidermal growth factor receptor pathway substrate 8 (EPS8) expression status and role in colorectal carcinogenesis given that EPS8 has a conserved actin barbed-end capping function that is required for proper maturation in intestinal cells.

METHODS: We studied 8 colon cancer cell lines and 58 colorectal tumors (19 adenomas and 39 carcinomas). We performed expression microarray analysis of colon cancer cell lines followed by loss of heterozygosity (LOH) analysis and immunohistochemistry for EPS8 expression in colon tumors. Subsequently, we performed mutation analysis by direct sequencing and methylation analysis by bisulfite sequencing and methylation-specific polymerase chain reaction assays.

RESULTS: Expression microarray analysis of colon cancer cell lines showed overexpression of EPS8 transcript in all lines but RKO. Genome wide loss of heterozygosity (LOH) analysis of colon tumors, showed considerable LOH at the EPS8 gene locus. Immunohistochemically, EPS8 was constitutively expressed in normal colonic mucosa with a dot-like supranuclear localization with accentuation at the luminal surface supporting its proposed role in epithelial maturation. Nineteen colon tumors (4 adenoma, 15 carcinoma) out of 51 (37%) showed strikingly tumor specific EPS8 protein loss. Of the remaining tumors, 5/51 (2 adenoma, and 3 carcinoma, 10%) showed marked overexpression, while 27/51 tumors (53%) showed retained expression. Mutation analysis revealed a missense mutation (c.794C>T, p.R265C) in exon 8 in RKO. The EPS8 promoter was also methylated in RKO, but there was no significant methylation in other cell lines or carcinoma specimens.

CONCLUSION: The loss of EPS8 expression in colorectal adenomas and carcinomas suggests that down regulation of this gene contributes to the development of a subset of colorectal cancers, a finding which could have applications in diagnosis and treatment.

Endocytosis and signaling: cell logistics shape the eukaryotic cell plan

Our understanding of endocytosis has evolved remarkably in little more than a decade. This is the result not only of advances in our knowledge of its molecular and biological workings, but also of a true paradigm shift in our understanding of what really constitutes endocytosis and of its role in homeostasis. Although endocytosis was initially discovered and studied as a relatively simple process to transport molecules across the plasma membrane, it was subsequently found to be inextricably linked with almost all aspects of cellular signaling. This led to the notion that endocytosis is actually the master organizer of cellular signaling, providing the cell with understandable messages that have been resolved in space and time. In essence, endocytosis provides the communications and supply routes (the logistics) of the cell. Although this may seem revolutionary, it is still likely to be only a small part of the entire story. A wealth of new evidence is uncovering the surprisingly pervasive nature of endocytosis in essentially all aspects of cellular regulation. In addition, many newly discovered functions of endocytic proteins are not immediately interpretable within the classical view of endocytosis. A possible framework, to rationalize all this new knowledge, requires us to "upgrade" our vision of endocytosis. By combining the analysis of biochemical, biological, and evolutionary evidence, we propose herein that endocytosis constitutes one of the major enabling conditions that in the history of life permitted the development of a higher level of organization, leading to the actuation of the eukaryotic cell plan.

Chemotherapeutic-induced apoptosis: a phenotype for pharmacogenomics studies

AIM

To determine whether cellular apoptosis is a suitable phenotypic trait for pharmacogenomics studies by evaluating caspase 3/7-mediated activity in lymphoblastoid cell lines after treatment with six chemotherapeutic agents: 5'-deoxyfluorouridine, pemetrexed, cytarabine, paclitaxel, carboplatin, and cisplatin.

MATERIALS AND METHODS

Using monozygotic twin pair and sibling pair lymphoblastoid cell lines, we identified conditions for measurement of caspase 3/7 activity in lymphoblastoid cell lines. Genome-wide association studies were performed with over 2 million single nucleotide polymorphisms (SNPs) and cisplatin-induced apoptosis in HapMap CEU cell lines (n=77).

RESULTS

Although treatment with 5'-deoxyfluorouridine and pemetrexed for up to 24 h resulted in low levels of apoptosis or interindividual variation in caspase-dependent cell death; paclitaxel, cisplatin, carboplatin, and cytarabine treatment for 24 h resulted in 9.4-fold, 9.1-fold, 7.0-fold, and 6.0-fold increases in apoptosis relative to control, respectively. There was a weak correlation between caspase activity and cytotoxicity (r(2)=0.03-0.29) demonstrating that cytotoxicity and apoptosis are two distinct phenotypes that may produce independent genetic associations. Estimated heritability (h(2)) for apoptosis was 0.57 and 0.29 for cytarabine (5 and 40 μmol/l, respectively), 0.22 for paclitaxel (12.5 nmol/l), and 0.34 for cisplatin (5 μmol/l). In the genome-wide association study using the HapMap CEU panel, we identified a significant enrichment of cisplatin-induced cytotoxicity SNPs within the significant cisplatin-induced apoptosis SNPs and an enrichment of expression quantitative trait loci (eQTL). Among these eQTLs, we identified several eQTLs with known function related to apoptosis and/or cytotoxicity.

CONCLUSION

Our study identifies apoptosis as a phenotype for pharmacogenomic studies in lymphoblastoid cell lines after treatment with paclitaxel, cisplatin, carboplatin, and cytarabine that may have utility for discovering biomarkers to predict response to certain chemotherapeutics.

c-Jun N-terminal kinase 2 (JNK2) enhances cell migration through epidermal growth factor substrate 8 (EPS8)

Membrane-bound receptors induce biochemical signals to remodel the actin cytoskeleton and mediate cell motility. In association with receptor tyrosine kinases, several downstream mitogen-induced kinases facilitate cell migration. Here, we show a role for c-Jun N-terminal kinase 2 (JNK2) in promoting mammary cancer cell migration through inhibition of epidermal growth factor substrate 8 (EPS8) expression, a key regulator of EGF receptor (R) signaling and trafficking. Using jnk2(-/-) mice, we found that EPS8 expression is higher in polyoma middle T antigen (PyVMT)jnk2(-/-) mammary tumors and jnk2(-/-) mammary glands compared with the respective jnk2(+/+) controls. The inverse relationship between the jnk2 and eps8 expression was also associated with cancer progression in that patients with basal-type breast tumors expressing high jnk2 and low eps8 experienced poor disease-free survival. In mammary tumor cell lines, the absence of jnk2 greatly reduces cell migration that is rescued by EPS8 knockdown. Subsequent studies show that JNK2 enhances formation of the EPS8-Abi-1-Sos-1 complex to augment EGFR activation of Akt and ERK, whereas the absence of JNK2 promotes ESP8/RN-Tre association to inhibit endocytotic trafficking of the EGFR. Together, these studies unveil a critical role for JNK2 and EPS8 in receptor tyrosine kinase signaling and trafficking to convey distinctly different effects on cell migration.

Expression and functional validation of new p38α transcriptional targets in tumorigenesis

p38α MAPK (mitogen-activated protein kinase) plays an important tumour suppressor role, which is mediated by both its negative effect on cell proliferation and its pro-apoptotic activity. Surprisingly, most tumour suppressor mechanisms co-ordinated by p38α have been reported to occur at the post-translational level. This contrasts with the important role of p38α in the regulation of transcription and the profound changes in gene expression that normally occur during tumorigenesis. We have analysed whole-genome expression profiles of Ras-transformed wild-type and p38α-deficient cells and have identified 202 genes that are potentially regulated by p38α in transformed cells. Expression analysis has confirmed the regulation of these genes by p38α in tumours, and functional validation has identified several of them as probable mediators of the tumour suppressor effect of p38α on Ras-induced transformation. Interestingly, approx. 10% of the genes that are negatively regulated by p38α in transformed cells contribute to EGF (epidermal growth factor) receptor signalling. Our results suggest that inhibition of EGF receptor signalling by transcriptional targets of p38α is an important function of this signalling pathway in the context of tumour suppression.

P66shc and its downstream Eps8 and Rac1 proteins are upregulated in esophageal cancers

Members of Shc (src homology and collagen homology) family, p46shc, p52shc, p66shc have known to be related to cell proliferation and carcinogenesis. Whereas p46shc and p52shc drive the reaction forward, the role of p66shc in cancers remains to be understood clearly. Hence, their expression in cancers needs to be evaluated carefully so that Shc analysis may provide prognostic information in the development of carcinogenesis. In the present study, the expression of p66shc and its associate targets namely Eps8 (epidermal pathway substrate 8), Rac1 (ras-related C3 botulinum toxin substrate1) and Grb2 (growth factor receptor bound protein 2) were examined in fresh tissue specimens from patients with esophageal squamous cell carcinoma and esophageal adenocarcinoma using western blot analysis. A thorough analysis of both esophageal squamous cell carcinoma and adenocarcinoma showed p66shc expression to be significantly higher in both types of carcinomas as compared to the controls. The controls of adenocarcinoma show a higher basal expression level of p66shc as compared to the controls of squamous cell carcinoma. The expression level of downstream targets of p66shc i.e., eps8 and rac1 was also found to be consistently higher in human esophageal carcinomas, and hence correlated positively with p66shc expression. However the expression of grb2 was found to be equal in both esophageal squamous cell carcinoma and adenocarcinoma. The above results suggest that the pathway operated by p66shc in cancers does not involve the participation of Ras and Grb2 as downstream targets instead it operates the pathway involving Eps8 and Rac1 proteins. From the results it is also suggestive that p66shc may have a role in the regulation of esophageal carcinomas and represents a possible mechanism of signaling for the development of squamous cell carcinoma and adenocarcinoma of esophagus.

EPS8 upregulates FOXM1 expression, enhancing cell growth and motility

Previous studies from our laboratory have indicated that overexpression of the epidermal growth factor receptor pathway substrate 8 (EPS8) enhances cell proliferation, migration and tumorigenicity in vivo, although the mechanisms involved remain unexplored. A microarray screen to search for potential mediators of EPS8 identified upregulation of multiple cell cycle-related targets such as the transcription factor FOXM1 and several of its reported downstream mediators, including cdc20, cyclin B1, cyclin A, aurora-B kinase and cdc25C in cells with elevated EPS8, as well as matrix metalloproteinase-9, which we reported previously to be upregulated by EPS8-dependent mechanisms. Cells engineered to overexpress FOXM1 showed increased proliferation, similar to EPS8-overexpressing cells. Conversely, targeted knockdown of FOXM1 in EPS8-overexpressing cells reduced proliferation. Cotransfection of EPS8 with a FOXM1-luciferase reporter plasmid into 293-T- or SVpgC2a-immortalized buccal keratinocytes demonstrated that EPS8 enhances FOXM1 promoter activity, whereas chromatin immunoprecipitation assays revealed elevated levels of acetylated histone H3 associated with the FOXM1 promoter in cells expressing high levels of EPS8. Treatment of EPS8-overexpressing cells with inhibitors of phosphoinositide 3-OH kinase or AKT reduced expression of FOXM1 and aurora-B kinase, a transcriptional target of FOXM1. Overexpression of EPS8 induced expression of the chemokine ligands CXCL5 and CXCL12 in a FOXM1-dependent manner, which was blocked by LY294002 or a dominant-negative form of AKT. Additionally, overexpression of FOXM1 enhanced cell migration, whereas targeted knockdown of CXCL5 or inhibition of AKT reduced migration of EPS8-expressing cells. These data suggest that EPS8 enhances cell proliferation and migration in part by deregulating FOXM1 activity and inducing CXC-chemokine expression, mediated by PI3K- and AKT-dependent mechanisms.

Eps8 is recruited to lysosomes and subjected to chaperone-mediated autophagy in cancer cells

Eps8 controls actin dynamics directly through its barbed end capping and actin-bundling activity, and indirectly by regulating Rac-activation when engaged into a trimeric complex with Eps8-Abi1-Sos1. Recently, Eps8 has been associated with promotion of various solid malignancies, but neither its mechanisms of action nor its regulation in cancer cells have been elucidated. Here, we report a novel association of Eps8 with the late endosomal/lysosomal compartment, which is independent from actin polymerization and specifically occurs in cancer cells. Endogenous Eps8 localized to large vesicular lysosomal structures in metastatic pancreatic cancer cell lines, such as AsPC-1 and Capan-1 that display high Eps8 levels. Additionally, ectopic expression of Eps8 increased the size of lysosomes. Structure-function analysis revealed that the region encompassing the amino acids 184-535 of Eps8 was sufficient to mediate lysosomal recruitment. Notably, this fragment harbors two KFERQ-like motifs required for chaperone-mediated autophagy (CMA). Furthermore, Eps8 co-immunoprecipitated with Hsc70 and LAMP-2, which are key elements for the CMA degradative pathway. Consistently, in vitro, a significant fraction of Eps8 bound to (11.9+/-5.1%) and was incorporated into (5.3+/-6.5%) lysosomes. Additionally, Eps8 binding to lysosomes was competed by other known CMA-substrates. Fluorescence recovery after photobleaching revealed that Eps8 recruitment to the lysosomal membrane was highly dynamic. Collectively, these results indicate that Eps8 in certain human cancer cells specifically localizes to lysosomes, and is directed to CMA. These results open a new field for the investigation of how Eps8 is regulated and contributes to tumor promotion in human cancers.

Schistosoma mansoni: signal transduction processes during the development of the reproductive organs

Among the topics of considerable interest concerning our understanding of the unusual biology of schistosomes is the sexual maturation of the female. The identification of genes coding for signal transduction proteins controlling essential steps of the pairing-dependent differentiation of the reproductive organs, vitellarium and ovary will help to substantiate our knowledge about this unique parasite. Furthermore, such signalling proteins could be potential targets to interfere with the development of this parasite to combat schistosomiasis since its pathology is caused by the eggs. This review summarises first post-genomic steps to elucidate the function of gonad-specific signalling molecules which were identified by homology-based cloning strategies, by in silico identification or by yeast two-hybrid interaction analyses, using a combination of novel techniques. These include the in vitro culture of adult schistosomes, their treatment with chemical inhibitors to block enzyme activity, the use of RNAi to silence gene function post-transcriptionally, and confocal laser scanning microscopy to study the morphological consequences of these experimental approaches. Finally, we propose a first model of protein networks that are active in the ovary regulating mitogenic activity and differentiation. Some of these molecules are also active in the testes of males, probably fulfilling similar roles as in the ovary.

Mithramycin inhibits human epithelial carcinoma cell proliferation and migration involving downregulation of Eps8 expression

Mithramycin is an inhibitor of the binding of the Sp-family transcription factor to the GC box. Many studies show that mithramycin may reduce the expression of many oncogenes by inhibiting the mRNA and protein synthesis and it has been used as an antibiotic chemotherapy drug for a long time. Recently, Eps8 (EGFR pathway substrate 8) has been revealed to be a novel proto-oncogene related to cellular transformation, Rac activation and actin barbed-end-capping activity. Therefore, the aim of this study was to verify whether Eps8 might be regulated by mithramycin. Results showed that mithramycin could reduce the mRNA and protein levels of Eps8 in dose- and time-dependent manners in several cancer cell lines. Furthermore, cell growth and migration ability were also reduced significantly by mithramycin treatment. Since Src is a well-known Eps8 activity enhancer, a v-Src transfected IV5 cell line was subjected to mithramycin treatment and then analyzed to show that Src expression was unable to restore the mithramycin-induced decrease in Eps8 expression, cell growth, and migration ability. To further confirm the above mentioned results, the expression of Eps8 was eliminated by a transient transfection with siRNA and subsequent analysis showed that silencing of Eps8 might also lead to a reduced growth and migration ability of cancer cells. These findings suggested that Eps8 was involved in the regulation of growth and motility of cancer cells and mithramycin might exert its anticancer ability via a pathway involving the downregulation of Eps8.

EMT, the cytoskeleton, and cancer cell invasion

The metastatic process, i.e. the dissemination of cancer cells throughout the body to seed secondary tumors at distant sites, requires cancer cells to leave the primary tumor and to acquire migratory and invasive capabilities. In a process of epithelial-mesenchymal transition (EMT), besides changing their adhesive repertoire, cancer cells employ developmental processes to gain migratory and invasive properties that involve a dramatic reorganization of the actin cytoskeleton and the concomitant formation of membrane protrusions required for invasive growth. The molecular processes underlying such cellular changes are still only poorly understood, and the various migratory organelles, including lamellipodia, filopodia, invadopodia and podosomes, still require a better functional and molecular characterization. Notably, direct experimental evidence linking the formation of migratory membrane protrusions and the process of EMT and tumor metastasis is still lacking. In this review, we have summarized recent novel insights into the molecular processes and players underlying EMT on one side and the formation of invasive membrane protrusions on the other side.

Upregulation of Eps8 in oral squamous cell carcinoma promotes cell migration and invasion through integrin-dependent Rac1 activation

Oral squamous cell carcinoma (OSCC) is a lethal disease and early death usually occurs as a result of local invasion and regional lymph node metastases. Current treatment regimens are, to a certain degree, inadequate, with a 5-year mortality rate of around 50% and novel therapeutic targets are urgently required. Using expression microarrays, we identified the eps8 gene as being overexpressed in OSCC cell lines relative to normal oral keratinocytes, and confirmed these findings using RT-PCR and western blotting. In human tissues, we found that Eps8 was upregulated in OSCC (32% of primary tumors) compared with normal oral mucosa, and that expression correlated significantly with lymph node metastasis (P=0.032), suggesting a disease-promoting effect. Using OSCC cell lines, we assessed the functional role of Eps8 in tumor cells. Although suppression of Eps8 produced no effect on cell proliferation, both cell spreading and migration were markedly inhibited. The latter cell functions may be modulated through the small GTP-ase, Rac1 and we used pull-down assays to investigate the role of Eps8 in Rac1 signaling. We found that alphavbeta6- and alpha5beta1-integrin-dependent activation of Rac1 was mediated through Eps8. Knockdown of either Eps8 or Rac1, inhibited integrin-dependent cell migration similarly and transient expression of constitutively active Rac1 restored migration of cells in which Eps8 expression had been suppressed. We also showed that knockdown of Eps8 inhibited tumor cell invasion in an organotypic model of OSCC. These data suggest that Eps8 and Rac1 are part of an integrated signaling pathway modulating integrin-dependent tumour cell motility and identify Eps8 as a possible therapeutic target.

Epidermal growth factor receptor pathway substrate 8 is overexpressed in human pituitary tumors: role in proliferation and survival

Based on prior work showing that human pituitary tumors overexpress epidermal and fibroblast growth factor receptors, we hypothesized that downstream components of growth factor signaling pathways may also be dysregulated. Epidermal growth factor pathway substrate number 8 (Eps8) was identified as a transcript overexpressed (5.9-fold) in human pituitary tumors compared with normal pituitary by DNA microarrays. Eps8 mRNA up-regulation was confirmed by semiquantitative RT-PCR. Immunoblot analysis showed that Eps8 protein levels and its downstream target phosphorylated ERK were also up-regulated in human pituitary tumors. Stable overexpression of Eps8 in LbetaT2 gonadotrope pituitary cells augmented colony formation in soft agar at d 21. Eps8 cells proliferated more robustly compared with controls in growth factor replete as well as growth-restricted conditions. In addition, the Eps8 overexpressing cells were protected from serum withdrawal-induced apoptosis compared with controls as assessed by caspase-3 cleavage. Epidermal growth factor activated a robust amplification of ERK and modest up-regulation of Akt in Eps8-overexpressing pituitary cells compared with vector controls. MAPK kinase inhibition or silencing of Eps8 blunted the proliferation of the cells in response to growth factor stimulation. Blockade of the phosphatidylinositol 3-kinase pathway or silencing of Eps8 resulted in a loss of the Eps8 protection from growth factor withdrawal-induced apoptosis. Together these data support a role of Eps8 in amplifying growth factor receptor signaling in human pituitary tumors to promote proliferation and cell survival.

Role for EPS8 in squamous carcinogenesis

We have investigated the role of the signaling intermediate, EPS8, in tumor progression using a model system and in vivo. HN4 primary tumor cells express low levels of EPS8, similar to normal keratinocytes, and show minimal invasion in vitro in response to epidermal growth factor, whereas HN12 cells express high levels of EPS8 and are highly motile in vitro and tumorigenic in vivo. Additional independent tumor cell lines also showed elevated EPS8 expression compared with normal keratinocytes. Using retroviral transduction, we generated HN4 cell lines expressing EPS8 (HN4/EPS8) at levels equivalent to those present in HN12 cells. HN4/EPS8 cells showed increased proliferation and migration compared with controls, together with elevated expression and activity of matrix metalloprotease (MMP)-9, which was dependent on protein kinase B (AKT) activity. Introduction of plasmids that direct synthesis of EPS8 short hairpin RNA (shRNA) into HN12 cells resulted in decreased EPS8 expression in these cells, which correlated with a decrease in their capacity to migrate and invade in vitro. In addition, shRNA-mediated knockdown of EPS8 reduced expression and activity of MMP-9 produced by these cells and reduced MMP-9 promoter activity. EPS8 knockdown cells showed decreased tumorigenicity in vivo compared with controls and lower MMP-9 expression. Conversely, overexpression of EPS8 in HN4 cells was sufficient to induce growth of these non-tumorigenic cells in orthotopic transplantation assays. Furthermore, EPS8 expression in clinical samples of squamous cell carcinoma showed variable expression levels and broadly paralleled expression of MMP-9. The data support a role for EPS8 in squamous carcinogenesis.

The role of palladin in actin organization and cell motility

Palladin is a widely expressed protein found in stress fibers, focal adhesions, growth cones, Z-discs, and other actin-based subcellular structures. It belongs to a small gene family that includes the Z-disc proteins myopalladin and myotilin, all of which share similar Ig-like domains. Recent advances have shown that palladin shares with myotilin the ability to bind directly to F-actin, and to crosslink actin filaments into bundles, in vitro. Studies in a variety of cultured cells suggest that the actin-organizing activity of palladin plays a central role in promoting cell motility. Correlative evidence also supports this hypothesis, as palladin levels are typically up-regulated in cells that are actively migrating: in developing vertebrate embryos, in cells along a wound edge, and in metastatic cancer cells. Recently, a mutation in the human palladin gene was implicated in an unusually penetrant form of inherited pancreatic cancer, which has stimulated new ideas about the role of palladin in invasive cancer.

Eps8 is increased in pancreatic cancer and required for dynamic actin-based cell protrusions and intercellular cytoskeletal organization

We investigated the role of Eps8 in pancreatic cancer. Eps8 was significantly increased in pancreatic cancer and colocalized with F-actin, predominantly in pancreatic ductal cells. Eps8 levels were higher in cell lines derived from ascites and metastases than in those from primary tumors. Expression correlated positively with the migratory potential of tumor cells. Eps8 localized to the tips of F-actin filaments, filopodia, and the leading edge of cells. Eps8 knockdown altered cell shape and actin-based cytoskeletal structures, impairing protrusion formation and cell-cell junctions. We concluded that Eps8 is increased in pancreatic cancer and correlates with migratory potential and tumor progression in vitro. Eps8 is essential for actin dynamics and cell interactions, independent of Eps8-like gene products.

Combined cDNA array comparative genomic hybridization and serial analysis of gene expression analysis of breast tumor progression

To identify genetic changes involved in the progression of breast carcinoma, we did cDNA array comparative genomic hybridization (CGH) on a panel of breast tumors, including 10 ductal carcinoma in situ (DCIS), 18 invasive breast carcinomas, and two lymph node metastases. We identified 49 minimal commonly amplified regions (MCRs) that included known (1q, 8q24, 11q13, 17q21-q23, and 20q13) and several uncharacterized (12p13 and 16p13) regional copy number gains. With the exception of the 17q21 (ERBB2) amplicon, the overall frequency of copy number alterations was higher in invasive tumors than that in DCIS, with several of them present only in invasive cancer. Amplification of candidate loci was confirmed by quantitative PCR in breast carcinomas and cell lines. To identify putative targets of amplicons, we developed a method combining array CGH and serial analysis of gene expression (SAGE) data to correlate copy number and expression levels for each gene within MCRs. Using this approach, we were able to distinguish a few candidate targets from a set of coamplified genes. Analysis of the 12p13-p12 amplicon identified four putative targets: TEL/ETV6, H2AFJ, EPS8, and KRAS2. The amplification of all four candidates was confirmed by quantitative PCR and fluorescence in situ hybridization, but only H2AFJ and EPS8 were overexpressed in breast tumors with 12p13 amplification compared with a panel of normal mammary epithelial cells. These results show the power of combined array CGH and SAGE analysis for the identification of candidate amplicon targets and identify H2AFJ and EPS8 as novel putative oncogenes in breast cancer.

Cell fate-specific regulation of EGF receptor trafficking during Caenorhabditis elegans vulval development

By controlling the subcellular localization of growth factor receptors, cells can modulate the activity of intracellular signal transduction pathways. During Caenorhabditis elegans vulval development, a ternary complex consisting of the LIN-7, LIN-2 and LIN-10 PDZ domain proteins localizes the epidermal growth factor receptor (EGFR) to the basolateral compartment of the vulval precursor cells (VPCs) to allow efficient receptor activation by the inductive EGF signal from the anchor cell. We have identified EGFR substrate protein-8 (EPS-8) as a novel component of the EGFR localization complex that links receptor trafficking to cell fate specification. EPS-8 expression is upregulated in the primary VPCs, where it creates a positive feedback loop in the EGFR/RAS/MAPK pathway. The membrane-associated guanylate kinase LIN-2 recruits EPS-8 into the receptor localization complex to retain the EGFR on the basolateral plasma membrane, and thus allow maximal receptor activation in the primary cell lineage. Low levels of EPS-8 in the neighboring secondary VPCs result in the rapid degradation of the EGFR, allowing these cells to adopt the secondary cell fate. Extracellular signals thus regulate EGFR trafficking in a cell type-specific manner to control pattern formation during organogenesis.

No complementation between TP53 or RB-1 and v-src in astrocytomas of GFAP-v-src transgenic mice

Human low-grade astrocytomas frequently recur and progress to states of higher malignancy. During tumor progression TP53 alterations are among the first genetic changes, while derangement of the p16/p14ARF/RB-1 system occurs later. To probe the pathogenetic significance of TP53 and RB-1 alterations, we introduced a v-src transgene driven by glial fibrillary acidic protein (GFAP) regulatory elements (which causes preneoplastic astrocytic lesions and stochastically astrocytomas of varying degrees of malignancy) into TP53+/- or RB-1+/- mice. Hemizygosity for TP53 or RB-1 did not increase the incidence or shorten the latency of astrocytic tumors in GFAP-v-src mice over a period of up to 76 weeks. Single strand conformation analysis of exons 5 to 8 of non-ablated TP53 alleles revealed altered migration patterns in only 3/16 tumors analyzed. Wild-type RB-1 alleles were retained in all RB-1+/-GFAP-v-src mice-derived astrocytic tumors analyzed, and pRb immunostaining revealed protein expression in all tumors. Conversely, the GFAP-v-src transgene did not influence the development of extraneural tumors related to TP53 or RB-1 hemizygosity. Therefore, the present study indicates that neither loss of RB-1 nor of TP53 confer a growth advantage in vivo to preneoplastic astrocytes expressing v-src, and suggests that RB-1 and TP53 belong to one single complementation group along with v-src in this transgenic model of astrocytoma development. The stochastic development of astrocytic tumors in GFAP-v-src, TP53+/- GFAP-v-src, and RB-1+/- GFAP-v-src transgenic mice indicates that additional hitherto unknown genetic lesions of astrocytes contribute to tumorigenesis, whose elucidation may prove important for our understanding of astrocytoma initiation and progression.

Uncoupling of epidermal growth factor-dependent proliferation and invasion in a model of squamous carcinoma progression

Cell lines pairs were established from a primary squamous carcinoma of tongue and a lymph node metastasis and their biological behavior characterized. HN12 cells, derived from metastatic SCC, formed tumors upon subcutaneous transplantation to athymic mice, whereas HN4, derived from a primary lesion in the same individual, were non-tumorigenic in this assay. EGF stimulated proliferation of HN4 cells; in comparison, not only were metastatic HN12 cells refractory to the stimulatory effects of this growth factor but showed inhibition at higher growth factor concentrations. However, in contrast to the effects on proliferation, EGF (10 ng/ml) readily induced HN12 cells to invade in Boyden chamber assays whereas HN4 were non-invasive under these conditions. The invasive properties of HN12 cells were apparently independent of MMP-2 activity, as levels of active MMP-2 were higher in the non-invasive cells. However, EGF stimulated MMP-9 activity in invasive cells. Additionally, HN12 cells expressed constitutively high levels of active MMP-7 and MMP-3/10. The pharmacological agents LY294002, PD098059, SP600125, or SB202190 inhibited invasion of HN12 cells, suggesting requirement for phosphoinositide 3-OH kinase- and mitogen activated protein kinase-dependent pathways in the process. The data indicate that distinct biochemical differences distinguish metastatic squamous carcinoma cells from those derived from corresponding primary tumors, resulting in their contrasting biological properties.

Global Protein Shotgun Expression Profiling of Proliferating MCF-7 Breast Cancer Cells

Protein expression becomes altered in breast epithelium during malignant transformation. Knowledge of these perturbations should provide insight into the molecular basis of breast cancer, as well as reveal possible new therapeutic targets. To this end, we have performed an extensive comparative proteomic survey of global protein expression patterns in proliferating MCF-7 breast cancer cells and normal human mammary epithelial cells using gel-free shotgun tandem mass spectrometry. Pathophysiological alterations associated with the malignant breast cancer phenotype were detected, including differences in the apparent levels of key regulators of the cell cycle, signal transduction, apoptosis, transcriptional regulation, and cell metabolism.

IRSp53/Eps8 Complex Is Important for Positive Regulation of Rac and Cancer Cell Motility/Invasiveness

IRSp53 has been characterized as an adaptor protein that links Rho-family small GTPases, such as Rac, to reorganization of the actin cytoskeleton. Here, we search for other binding partners for the IRSp53 SH3 domain and identify Eps8 as the major binding protein in fibroblasts and various cancer cell lines. Eps8 has been shown to form a Rac-specific guanine nucleotide exchange factor complex with Abi-1 and Sos-1, which seems essential for ruffling formation induced by oncogenic Ras. We confirm the IRSp53/Eps8 complex formation in vivo and the direct association between Eps8 NH(2)-terminal proline-rich sequence and IRSp53 SH3 domain. This complex synergistically activates Rac by reinforcing the formation of the Eps8/Abi-1/Sos-1 Rac-guanine nucleotide exchange factor complex, which mediates positive regulation of Rac activity. In addition, IRSp53/Eps8 complex formation as determined by fluorescent resonance energy transfer analysis, occurs at the leading edge of motile cells, and the motility and invasiveness of HT1080 fibrosarcoma cells are suppressed by inhibiting complex formation. These findings implicate the importance of the IRSp53/Eps8 complex in Rac activation and metastatic behavior of the malignant tumor cells.

Participation of p97Eps8 in Src-mediated Transformation

Histone acetylase and histone deacetylase are two crucial enzymes that determine the structure of chromatin, regulating gene expression. In this study, we observed that trichostatin A (TSA), a specific histone deacetylase inhibitor, could effectively inhibit the growth of v-Src-transformed (IV5) cells and abrogate their ability to form colonies in soft agar. Further analysis demonstrated that, although TSA reduced the expression of Eps8 in a dose- and time-dependent manner, both the protein expression and kinase activity of v-Src remained constant, and the abundance and phosphotyrosine levels of Src substrates, including cortactin, focal adhesion kinase, p130(Cas), paxillin, and Shc, were not altered. Notably, removal of TSA from the medium restored not only the expression of Eps8, but also cellular growth. Northern and reverse transcription-PCR analyses revealed the significant reduction of eps8 transcripts in TSA-treated IV5 cells relative to control cells. When active Src-expressing chicken embryonic cells were forced to overexpress p97(Eps8), they became resistant to TSA-mediated anti-proliferation. Furthermore, using small interference RNA of eps8, we demonstrated the requirement for Eps8 in IV5 cell proliferation. Thus, our results highlight a critical role for p97(Eps8) in TSA-exerted growth inhibition of v-Src-transformed cells.

In silico analysis of the EPS8 gene family: genomic organization, expression profile, and protein structure

EPS8 codes for a protein essential in Ras to Rac signaling leading to actin remodeling. Three genes highly homologous to EPS8 were discovered, thereby defining a novel gene family. Here, we report the genomic structure of EPS8 and the EPS8-related genes in human and mouse. We performed BLASTN searches against the Celera Human Genome and Mouse Fragments Database. The mouse fragments were manually assembled, and the organization of both human and mouse genes was reconstructed. The gene structures in Celera annotations of the human and mouse genomes were compared to outline correspondences and divergences. We also compared the EPS8 family gene structures predicted by Celera with those predicted by NCBI. Moreover, we performed a virtual analysis of the expression of the EPS8 gene family members by using the SAGEmap Database in NCBI. Finally, we analyzed the domain organization of the gene products and their evolutionary conservation to define novel putative domains, thereby helping to predict novel modality of action for the members of this gene family. The data obtained will be instrumental in directing further experimental functional characterization of these genes.

Eps8 in the midst of GTPases

Eps8, originally identified as a substrate for the kinase activity of the epidermal growth factor receptor (EGFR), displays a domain organization typical of a signaling molecule that includes a putative N-terminal PTB domain, a central SH3 domain, and a C-terminal "effector region". This latter region directs Eps8 localization within the cell and is sufficient to activate the GTPase, Rac, leading to actin cytoskeletal remodeling. Eps8 binds, through its SH3 domain, to either Abi1 (also called E3b1) or RN-tre. Abi1 scaffolds together Eps8 and Sos1, a dual specificity guanine nucleotide exchange factor for Ras and Rac proteins, thus facilitating the formation of a trimeric complex, in turn required for activation of Rac. On the other hand, RN-tre, a Rab5 GTPase activating protein, by entering in a complex with Eps8, inhibits EGFR internalization. Furthermore, RN-tre competes with Abi1 for binding to Eps8, diverting the latter from its Rac-activating function. Thus, depending on its engagement in different complexes, Eps8 participates to EGFR signaling through Rac and endocytosis through Rab5.

Shc mediates ligand-induced internalization of epidermal growth factor receptors

In order to clarify the physiological relevance of the interaction between Shc and adaptins, components of plasma membrane-coated pit adaptor complex AP2, we investigated the role of Shc in ligand-induced endocytosis of epidermal growth factor (EGF) receptors. In vitro peptide binding assay showed that alpha-adaptin bound to the wild-type peptide corresponding to amino acids 346-355 of Shc, RDLFDMKPFE, but not to the mutant peptide in which both phenylalanines at 349 and 354 were substituted for alanines (FA). Using adenovirus vectors carrying a herpes simplex virus epitope-tagged 52-kDa wild-type Shc and Shc FA, we examined the interaction between Shc, AP2, and EGF receptors in intact cells. Alpha-adaptin bound to wild-type Shc in an EGF-dependent manner, whereas EGF-dependent association of alpha-adaptin with Shc FA was markedly reduced. In addition, EGF increased the amount of alpha-adaptin coprecipitated with EGF receptors in cells expressing wild-type Shc but not Shc FA. These results suggest that EGF stimulates Shc-AP2 complex formation and association of Shc-AP2 complexes with EGF receptors. Internalization assay showed that (125)I-EGF internalization was reduced in cells overexpressing Shc FA. Immunofluorescence study showed that punctate staining along the plasma membrane border as well as punctate pattern characteristic of cytoplasmic vesicles near the plasma membrane was enhanced in cells expressing wild-type Shc. These results suggest, therefore, the implication of Shc in ligand-induced endocytosis of EGF receptors in intact cells.

The insulin receptor substrate (IRS)-1 recruits phosphatidylinositol 3-kinase to Ret: evidence for a competition between Shc and IRS-1 for the binding to Ret

Tyrosine 1062 of Ret, which represents an intracytoplasmic docking site for multiple signaling molecules, is essential for Ret-mediated activation of phosphatidylinositol 3-Kinase (PI3-K). PI3-K, in turn, has been implicated in inducing cell survival and neoplastic transformation mediated by Ret. We have examined the mechanisms by which Ret stimulates PI3-K. Here we show that the Insulin Receptor Substrate-1 (IRS-1) is tyrosine phosphorylated and associated with the p85 regulatory subunit of PI3-K in response to Ret activation. IRS-1 coimmunoprecipitates with Ret and co-expression of IRS-1 results in the potentiation of Ret-mediated activation of Akt(PKB), a bona fide effector of PI3-K. The association with the PTB domain of IRS-1 depends on the phosphorylation of tyrosine 1062 of Ret. The deletion of asparagine 1059 (delN1059) and the substitution of leucine 1061 (L1061P), two Ret mutations identified in families affected by congenital megacolon (Hirschsprung's disease), impair the binding of IRS-1 to Ret as well as Ret-mediated Akt(PKB) stimulation. Finally, we show that Shc, which was previously identified as another ligand of Y1062 of Ret, competes with IRS-1 for the binding to Ret pY1062. All together, these findings suggest that IRS-1 is a component of the signaling pathway which leads to Ret-mediated PI3-K activation, a pathway which can be targeted by Hirschsprung-associated Ret mutations. The alternative binding of Shc and IRS-1 to Ret pY1062 can be a system to modulate the activation of different intracellular signaling pathways and to elicit different biological responses following Ret activation.

Overexpression of p97Eps8 leads to cellular transformation: implication of pleckstrin homology domain in p97Eps8-mediated ERK activation

Two isoforms of Eps8, p97Eps8 and p68Eps8, have been identified as the substrates for receptor tyrosine kinases. Our previous studies indicated that both tyrosyl phosphorylation and protein expression of Eps8 were elevated in v-Src transformed cells. In an attempt to examine the role played by p97Eps8 in tumorigenesis, we have first obtained cells overexpressing p97Eps8 and its pleckstrin homology (PH)-truncated variant. We then demonstrated that cells overexpressing p97Eps8 not only exhibited the ability of focus formation in cell culture but also promoted the tumor formation in mice as compared to controls. Furthermore, elevated serum-induced extracellular responsive kinase (ERK) activation was observed in p97Eps8 overexpressors. This enhanced ERK activation was sensitive to a MEK1 specific inhibitor PD98059 and was important for p97Eps8-mediated transformation, since transfection of vectors expressing dominant negative MEK1 and p97Eps8 abrogated focus formation by p97Eps8. In contrast, PH-truncated p97Eps8 failed to localize at the plasma membrane and that the truncated variant also did not elevate ERK activation and cellular transformation in response to serum stimulation. Our results thus indicated that: (i) the gene encoding p97Eps8 was an oncogene; (ii) p97Eps8-induced oncogenesis was partly mediated by ERK activation; and (iii) the PH domain of p97Eps8 was critical for its cellular localization, ERK activation and its ability to transform cells. Oncogene (2001) 20, 106 - 112.

Evolution of Shc functions from nematode to human

The Shc protein family is characterized by the (CH2)-PTB-CH1-SH2 modularity. Its complexity increased during evolution from one locus in Drosophila (dShc), to at least three loci in mammals (shc, rai and sli). The three mammalian loci encode, because of alternative initiation codon usage and splicing pattern, at least six Shc-like proteins. Genetic and biological evidence indicates that the mammalian Shc isoforms regulate functions as diverse as growth (p52/p46Shc), apoptosis (p66Shc) and life-span (p66Shc). Available structure-function data and analysis of sequence similarities of Shc-like genes and proteins suggest complex diversification of Shc functions during evolution. Notably, Ras activation, the best-characterized Shc activity, appears to be a recent evolutionary acquisition.

The ShcA phosphotyrosine docking protein sensitizes cardiovascular signaling in the mouse embryo

The ShcA gene products have served as a model for the analysis of phosphotyrosine-recognition domains, and for the functions of docking proteins during tyrosine kinase signaling. Here we show that ShcA is primarily expressed in the cardiovascular system during early mouse embryogenesis and regulates both heart development and establishment of mature blood vessels. Targeted mutation suggests that the ShcA adaptor is a pivotal target of tyrosine kinases that selectively potentiates activation of the MAP kinase pathway in the remodeling vasculature. Biochemical analysis of mutant cells shows that ShcA sensitizes cells to growth factor-induced MAP kinase activation, and also organizes cytoskeletal rearrangement in response to the extracellular matrix. ShcA may therefore orchestrate complex interactions within the vascular compartment by rendering cells permissive to respond to soluble and adhesive external cues.