Eps8 facilitates cellular growth and motility of colon cancer cells by increasing the expression and activity of focal adhesion kinase

Single-cell transcriptomics uncover hub genes and cell-cell crosstalk in patients with hypertensive nephropathy

Hypertensive nephropathy (HTN) is one of the leading causes of end-stage renal disease, yet the molecular mechanisms are still unknown. To explore novel mechanisms and gene targets for HTN, the gene expression profiles of renal biopsy samples obtained from 2 healthy living donor controls and 5 HTN patients were determined by single-cell RNA sequencing. Key hub genes expression were validated by the Nephroseq v5 platform. The HTN endothelium upregulated cellular adhesion genes (ICAM2 and CEACAM1), inflammatory genes (ETS2 and IFI6) and apoptosis related genes (CNN3). Proximal tubules in HTN highly expressed hub genes including BBOX1, TPM1, TMSB10, SDC4, and NUP58, which might be potential novel targets for proximal tubular injury. The upregulated genes in tubules of HTN were mainly participating in inflammatory signatures including IFN-γ signature, NF-κB signaling, IL-12 signaling and Wnt signaling pathway. Receptor-ligand interaction analysis indicated potential cell-cell crosstalk between endothelial cells or mesangial cells with other renal resident cells in HTN. Together, our data identify a distinct cell-specific gene expression profile, pathogenic inflammatory signaling and potential cell-cell communications between endothelial cells or mesangial cells with other renal resident cells in HTN. These findings may provide a promising novel landscape for mechanisms and treatment of human HTN.

Loss of EPS8 sensitizes non-small-cell lung carcinoma to chemotherapy-induced DNA damage

Epidermal growth factor receptor pathway substrate number 8 (EPS8) has been reported to be critical in mediating tumor progression. However, the molecular and biological consequences of EPS8 overexpression remain unclear. Here we evaluated whether EPS8 increased DNA damage repair in non-small-cell lung carcinoma (NSCLC) cells and the mechanism of EPS8-mediated DNA damage repair which influenced chemosensitivity. Serial studies of functional experiments revealed that EPS8 knockdown inhibited cell growth, induced cell-cycle arrest and increased cisplatin therapeutic effects on NSCLC. EPS8 was found to induce DNA damage repair via upregulation of phosphorylated-ATM and downregulation of the tumor suppressor p53 and G1 cell kinase inhibitor p21. Moreover, in conjunction with cisplatin, decreasing EPS8 protein levels further increased p53 protein level and inhibited ATM signaling. Transplanted tumor studies were also performed to demonstrate that EPS8 knockdown inhibited tumor growth and sensitized tumors to cisplatin treatment. In conclusion, we have described a novel molecular mechanism through which EPS8 is likely to be involved in cancer progression and chemoresistance via DNA damage repair, indicating that EPS8 expression may influence the response to chemotherapy. Therefore, targeting EPS8 may be a potential therapeutic approach for patients with NSCLC.

Construction of Molecular Subtype and Prognosis Prediction Model of Osteosarcoma Based on Aging-Related Genes

Background

Osteosarcoma (OS) is a rare form of malignant bone cancer that is usually detected in young adults and adolescents. This disease shows a poor prognosis owing to its metastatic status and resistance to chemotherapy. Hence, it is necessary to design a risk model that can successfully forecast the OS prognosis in patients.

Methods

The researchers retrieved the RNA sequencing data and follow-up clinical data related to OS patients from the TARGET and GEO databases, respectively. The coxph function in R software was used for carrying out the Univariate Cox regression analysis for deriving the aging-based genes related sto the OS prognosis. The researchers conducted consistency clustering using the ConcensusClusterPlus R package. The R software package ESTIMATE, MCPcounter, and GSVA packages were used for assessing the immune scores of various subtypes using the ssGSEA technique, respectively. The Univariate Cox and Lasso regression analyses were used for screening and developing a risk model. The ROC curves were constructed, using the pROC package. The performance of their developed risk model and designed survival curve was conducted, with the help of the Survminer package.

Results

The OS patients were classified into 2 categories, as per the aging-related genes. The results revealed that the Cluster 1 patients showed a better prognosis than the Cluster 2 patients. Both clusters showed different immune microenvironments. Additional screening of the prognosis-associated genes revealed the presence of 5 genes, i.e., ERCC4, GPX4, EPS8, TERT, and STAT5A, and these data were used for developing the risk model. This risk model categorized the training set samples into the high- and low-risk groups. The patients classified into the high-risk group showed a poor OS prognosis compared to the low-risk patients. The researchers verified the reliability and robustness of the designed 5-gene signature using the internal and external datasets. This risk model was able to effectively predict the prognosis even in the samples having differing clinical features. Compared with other models, the 5- gene model performs better in predicting the risk of osteosarcoma.

Conclusion

The 5-gene signature developed by the researchers in this study could be effectively used for forecasting the OS prognosis in patients.

EPS8 supports pancreatic cancer growth by inhibiting BMI1 mediated proteasomal degradation of ALDH7A1

Aldehyde dehydrogenase 7 family member A1 (ALDH7A1) is an enzyme catalyzing lipid peroxidation of fatty aldehydes. It plays a critical role in sustaining high oxygen consumption rate (OCR) and ATP production in pancreatic ductal adenocarcinoma (PADC). However, why PADC cells maintain a relatively high level of ALDH7A1 concentration is still not well understood. In the current study, we explored the interplay between epidermal growth factor receptor kinase substrate 8 (EPS8) and ALDH7A1 in PADC cells. PADC cell lines MIA PaCa-2 and AsPANC-1 were used for in vitro and in vivo studies. The co-IP assay showed mutual interactions between Flag-EPS8 and Myc-ALDH7A1 in both MIA PaCa-2 and AsPANC-1 cells. EPS8 knockdown resulted in decreased ALDH7A1 protein levels and increased poly-ubiquitination. An interaction was observed between ALDH7A1 and BMI1 but not between BMI1 and EPS8. BMI1 knockdown reduced ALDH7A1 poly-ubiquitination and degradation caused by EPS8 knockdown. Dual EPS8 and ALDH7A1 knockdown had a synergistic effect on suppressing PADC cell proliferation in vitro and in vivo. In conclusion, this study revealed that EPS8 supports PADC growth by interacting with ALDH7A1 and inhibiting BMI1 mediated proteasomal degradation of ALDH7A1.

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 regulates an NLRP3 inflammasome-independent caspase-1 activation pathway in monosodium urate crystal-treated RAW264.7 macrophages

Gout is an inflammatory arthritis caused by the phagocytosis of monosodium urate (MSU) crystal deposition in joints. NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome-dependent caspase-1 activation is implicated in the processing of interleukin-1β (IL-1β), which is the major effector cytokine in the acute inflammatory response of gout. Mechanisms underlying caspase-1 activation remain unclear. Epidermal growth factor receptor pathway substrate no. 8 (Eps8) is a signal transducer and actin filament organizer that plays a key role in lipopolysaccharide-stimulated phagocytosis in macrophages. Here, RAW264.7 macrophages that have no intact NLRP3 inflammasomes were used to investigate the role of Eps8 in MSU crystal-mediated caspase-1 activation. A kinetic study revealed that the induction of Eps8 expression by MSU crystals occurred before NLRP3, p46/p33 caspase-1, and mature IL-1β in RAW 264.7 cells. In addition, actin cytoskeleton dynamics was required for Eps8 induction and caspase-1 activation in MSU crystal stimulation. Silencing Eps8 had no effect on the basal expression of p46/p33 caspase-1 and NLRP3, but nearly abolished MSU crystal-induced NLRP3 expression and caspase-1 activation. Furthermore, MSU crystals induced Eps8-pro-caspase-1 complex formation and Eps8 formed a stable complex with p33 caspase-1, but not with NLRP3. In summary, our results demonstrated for the first time the importance of Eps8 in MSU crystal-mediated caspase-1 activation without the involvement of NLRP3 inflammasomes.

Regulation of Src Family Kinases during Colorectal Cancer Development and Its Clinical Implications

Src family kinases (SFKs) are non-receptor kinases that play a critical role in the pathogenesis of colorectal cancer (CRC). The expression and activity of SFKs are upregulated in patients with CRC. Activation of SFKs promotes CRC cell proliferation, metastases to other organs and chemoresistance, as well as the formation of cancer stem cells (CSCs). The enhanced expression level of Src is associated with decreased survival in patients with CRC. Src-mediated regulation of CRC progression involves various membrane receptors, modulators, and suppressors, which regulate Src activation and its downstream targets through various mechanisms. This review provides an overview of the current understanding of the correlations between Src and CRC progression, with a special focus on cancer cell proliferation, invasion, metastasis and chemoresistance, and formation of CSCs. Additionally, this review discusses preclinical and clinical strategies to improve the therapeutic efficacy of drugs targeting Src for treating patients with CRC.

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.

FoxO3a inhibiting expression of EPS8 to prevent progression of NSCLC: A new negative loop of EGFR signaling

Background

The resistance to EGF receptor (EGFR) tyrosine kinase inhibitors (TKI) is a major challenge in the treatment of non-small cell lung cancer (NSCLC). Understanding the molecular mechanisms behind resistance is therefore an important issue. Here we assessed the role of EGFR pathway substrate 8 (EPS8) and Forkhead box O 3a (FoxO3a) as potentially valuable targets in the resistance of NSCLC .

Methods

The expression levels of EPS8 and FoxO3a in patients with NSCLC (n = 75) were examined by immunohistochemistry staining, while in cells were detected by qPCR and western blot. The effects of EPS8 and FoxO3a on resistance, migration and invasion, cell cycle arrest were detected by MTT, transwell and flow cytometry, respectively. Chromatin immunoprecipitation and luciferase reporter assays were performed to determine the mechanisms of EPS8 expression and FoxO3a regulation.

Findings

We observed that the expression of EPS8 inversely correlated with FoxO3a in NSCLC cell lines and NSCLC patients. FoxO3a levels were significantly decreased in tumor tissues compared with para-carcinoma tissues, while EPS8 is opposite. Besides, they play reverse roles in the resistance to gefitinib, the migration and invasion abilities, the cell cycle arrest in vitro and the tumor growth in vivo. Mechanistically, FoxO3a inhibits EPS8 levels by directly binding its gene promoter and they form a negative loop in EGFR pathway.

Interpretation

Targeting FoxO3a and EPS8 in EGFR signaling pathway prevents the progression of NSCLC, which implied that the negative loop they formed could served as a therapeutic target for overcoming resistance in NSCLC.

Funds

National Natural Science Foundation of China, Science and Technology Project of Henan, Outstanding Young Talent Research Fund of Zhengzhou University and the National Scholarship Fund.

Effect of trichostatin A on Burkitt's lymphoma cells: Inhibition of EPS8 activity through Phospho-Erk1/2 pathway

Histone deacetylase inhibitors (HDACi) manifest great potential for treatment of Burkitt's lymphoma (BL), an aggressive B-cell lymphoma. Epidermal growth factor receptor pathway substrate 8 (EPS8) is confirmed overexpressed and associated with poor prognosis in solid tumors and leukemia. However, EPS8 expression and the relationship between EPS8 and HDACi on BL remains obscure. Here, we hypothesized that trichostatin A (TSA), a pan-HDACi, could inhibit BL cells by downregulating EPS8. We demonstrated that TSA reduced cell viability, induced apoptosis and cell arrest at G0/G1. Mechanismly, TSA attenuated EPS8 and downstream Phospho-Erk1/2 pathway. Knockdown of EPS8 resulted in a significant reduction in cellular proliferation and suppressed Phospho-Erk1/2 pathway activity, particularly when combined with TSA. Conversely, overexpression of EPS8 rescued this phenomenon. Then we showed that the combination of TSA and Epirubicin had a more significant effect when compared with TSA or Epirubicin alone. Finally, knockdown of EPS8 and TSA had a synergistic suppression effect on BALB/c nude mice. In conclusion, this study reveals that TSA affects BL cells by suppressing Phospho-Erk1/2 pathway through downregulating EPS8.

A synthetic cell-penetrating peptide derived from nuclear localization signal of EPS8 exerts anticancer activity against acute myeloid leukemia

Background

Oncogenic roles of epidermal growth factor receptor pathway substrate no.8 (EPS8) have been widely reported in various tumors, making targeting of EPS8 an appealing prospect. Here, we describe the role of EPS8 in acute myeloid leukemia (AML) and consider the potential of EPS8 as an anti-AML target. Nuclear localization signal (NLS) residues of tumor-associated proteins are crucial for cell cycle progression, and specific inhibitors derived from the NLS have inhibitory effect on cancer cells. The NLS in EPS8 has potential as a specific anti-AML target.

Methods

Gene Expression Omnibus expression profiles of AML patients were used to test associations between EPS8 expression and AML patient outcome. The biological characteristics of AML cells after EPS8 knockdown were analyzed in vitro and in vivo. A specific peptide (CP-EPS8-NLS) derived from the NLS of EPS8 (amino acids 298–310) was synthesized, and the anti-AML effects of CP-EPS8-NLS were analyzed in cancer cells and in xenograft models. Mutated CP-EPS8-NLS and penetratin served as controls.

Results

We observed that elevated EPS8 expression in AML patients is associated with poor outcome. Knockdown of EPS8 significantly suppressed the survival of AML cells in vitro and in vivo. CP-EPS8-NLS interfered with EPS8-associated signaling and consequently exerted anti-AML activity. Importantly, CP-EPS8-NLS displayed anti-AML activity in various AML cell types, with diminished activity in PBMCs. CP-ESP8-NLS suppressed U937 cell proliferation, and injection of CP-EPS8-NLS exerted potent antitumor activity in the xenograft tumor models. A synergistic effect of CP-EPS8-NLS and chemotherapeutic agents was also observed in vitro and in vivo. Mechanistically, treatment of various AML cells with CP-EPS8-NLS downregulated the expression of EPS8 and its downstream pathways.

Conclusions

The function of CP-EPS8-NLS is explained by the presence of a NLS in EPS8, which has been shown to induce nuclear translocation, consequently resulting in EPS8 overexpression. These results indicate that EPS8 is a potential target for AML treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0682-x) contains supplementary material, which is available to authorized users.

EPS8 regulates proliferation, apoptosis and chemosensitivity in BCR-ABL positive cells via the BCR-ABL/PI3K/AKT/mTOR pathway

Although the introduction of tyrosine kinase inhibitors greatly improved the survival of patients with chronic myeloid leukemia (CML), drug resistance remains a problem. Thus, mechanism-based novel therapeutic targets warrant exploration. Recently, epidermal growth factor receptor kinase substrate 8 (EPS8), which has been identified as an oncogene and plays an important role in a broad spectrum of solid tumours, was reported to be related to poor prognosis or chemoresistance in acute leukemia patients. However, its role in CML remains unclear. In the present study, using q-RT-PCR, we demonstrated that CML patients expressed a higher level of EPS8 mRNA in bone marrow mononuclear cells than healthy controls. Then, to determine the effect of EPS8 on the biological functions of CML cells, EPS8 expression was knocked down in the human CML cell line K562. Reduced proliferation, increased apoptosis, impaired adhesion and migration were observed in K562 cells after EPS8 silencing. Notably, attenuation of EPS8 increased chemosensitivity both in imatinib-sensitive K562 cells and in the imatinib-resistant murine BCR-ABL⁺ 32D-p210^{BCR/ABL-T315I} cells. Mechanistically, knockdown of EPS8 downregulated p-BCR/ABL and its downstream AKT/mTOR signalling pathway. Finally, knockdown of EPS8 attenuated K562 cell proliferation in BALB/c nude mice. These data indicated that EPS8 regulated the proliferation, apoptosis and chemosensitivity in BCR-ABL positive cells via the BCR-ABL/PI3K/AKT/mTOR pathway. Targeting EPS8 alone or combined with a tyrosine kinase inhibitor may be a promising alternative therapeutic strategy.

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.

Pro-migratory and TGF-β-activating functions of αvβ6 integrin in pancreatic cancer are differentially regulated via an Eps8-dependent GTPase switch

The integrin αvβ6 is up-regulated in numerous carcinomas, where expression commonly correlates with poor prognosis. αvβ6 promotes tumour invasion, partly through regulation of proteases and cell migration, and is also the principal mechanism by which epithelial cells activate TGF-β1; this latter function complicates therapeutic targeting of αvβ6, since TGF-β1 has both tumour-promoting and -suppressive effects. It is unclear how these different αvβ6 functions are linked; both require actin cytoskeletal reorganization, and it is suggested that tractive forces generated during cell migration activate TGF-β1 by exerting mechanical tension on the ECM-bound latent complex. We examined the functional relationship between cell invasion and TGF-β1 activation in pancreatic ductal adenocarcinoma (PDAC) cells, and confirmed that both processes are αvβ6-dependent. Surprisingly, we found that cellular functions could be biased towards either motility or TGF-β1 activation depending on the presence or absence of epidermal growth factor receptor pathway substrate 8 (Eps8), a regulator of actin remodelling, endocytosis, and GTPase activation. Similar to αvβ6, we found that Eps8 was up-regulated in >70% of PDACs. In complex with Abi1/Sos1, Eps8 regulated αvβ6-dependent cell migration through activation of Rac1. Down-regulation of Eps8, Sos1 or Rac1 suppressed cell movement, while simultaneously increasing αvβ6-dependent TGF-β1 activation. This latter effect was modulated through increased cell tension, regulated by Rho activation. Thus, the Eps8/Abi1/Sos1 tricomplex acts as a key molecular switch altering the balance between Rac1 and Rho activation; its presence or absence in PDAC cells modulates αvβ6-dependent functions, resulting in a pro-migratory (Rac1-dependent) or a pro-TGF-β1 activation (Rho-dependent) functional phenotype, respectively. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

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.

Chaperone-mediated autophagy substrate proteins in cancer

All intracellular proteins undergo continuous synthesis and degradation. Chaperone-mediated autophagy (CMA) is necessary to maintain cellular homeostasis through turnover of cytosolic proteins (substrate proteins). This degradation involves a series of substrate proteins including both cancer promoters and suppressors. Since activating or inhibiting CMA pathway to treat cancer is still debated, targeting to the CMA substrate proteins provides a novel direction. We summarize the cancer-associated substrate proteins which are degraded by CMA. Consequently, CMA substrate proteins catalyze the glycolysis which contributes to the Warburg effect in cancer cells. The fact that the degradation of substrate proteins based on the CMA can be altered by posttranslational modifications such as phosphorylation or acetylation. In conclusion, targeting to CMA substrate proteins develops into a new anticancer therapeutic approach.

Identification and first characterization of SmEps8, a potential interaction partner of SmTK3 and SER transcribed in the gonads of Schistosoma mansoni

In eukaryotes the roles of protein kinases (PKs) regulating important biological processes such as growth and differentiation are well known. Molecular, biochemical, and physiological analyses trying to unravel principles of schistosome development have substantiated the importance for PKs also in this parasite. Amongst others the role of SmTK3 was studied, one of the first cellular PKs characterized from Schistosoma mansoni. Its function was demonstrated in mitogenic and differentiation processes in the gonads. Furthermore, first insights were obtained for the downstream part of a signal transduction cascade SmTK3 is involved in, which includes the diaphanous homolog SmDia. Here we attempted to further unravel the SmTK3 signaling cascade by searching for upstream interaction partners. Using yeast three-hybrid (Y3H) analyses we detected the epidermal growth factor receptor (EGFR) pathway substrate 8 of S. mansoni (SmEps8) as the most interesting candidate. By detailed interaction analyses we showed a contribution of the Src homology (SH) domains SH2 and SH3 of SmTK3 to binding, with a clear bias towards SH2. Compared to full-length SmEps8, binding was enhanced when only its 5' part including the phosphotyrosine binding domain (PTB) was used for interaction analyses including the SH2 domain of SmTK3, although phosphorylation seemed not to play a decisive role for binding. RT-PCR analyses and in situ hybridization experiments demonstrated similar transcription patterns of SmTK3 and SmEPS8, which co-localize in the reproductive organs. Furthermore, first evidence was obtained for SmEps8 interaction and colocalization with SER, one of the epidermal growth factor receptor (EGFR) homologs detected in S. mansoni. The results of this study provide first evidence for a SER-SmEps8-SmTK3-SmDia signal transduction pathway controlling differentiation processes in the gonads of S. mansoni.

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.

Ovatodiolide of Anisomeles indica Exerts the Anticancer Potential on Pancreatic Cancer Cell Lines through STAT3 and NF-κB Regulation

Pancreatic cancer is the eighth leading cause of cancer death worldwide. Patients with pancreatic cancer are normally diagnosed at an advanced stage and present poor survival rate. Ovatodiolide (OV), a bioactive macrocyclic diterpenoid isolated from Anisomeles indica, showed cytotoxicity effects in pancreatic cancer cells by inhibiting cell proliferation and inducing apoptosis. Moreover, not only were cell adhesion and invasion markedly suppressed in a dose-dependent manner, but the mRNA expression of matrix metalloproteinase-9 (MMP-9) and focal adhesion kinase (FAK) was also significantly decreased. Western blot analysis indicated that OV potently suppressed the phosphorylation of STAT-3 and its upstream kinase including ERK1/2, P38, and AKT Ser473. Meanwhile, OV inactivated the nuclear factor kappa B (NF-κB) by inhibiting IκB kinase (IKK α/β) activation and the subsequent suppression of inhibitor of kappa B (IκB) phosphorylation. These results demonstrated that OV could potentially inhibit Mia-PaCa2 cancer cells proliferation and induce apoptosis through modulation of NF-κB and STAT3 pathway. Moreover, OV suppressed cell invasiveness and interfered with cell-matrix adhesion in Mia-PaCa2 cancer cells by reducing MMP-9 and FAK transcription through suppressing NF-κB and STAT3 pathway. Taken together, our findings reveal a new therapeutic and antimetastatic potential of ovatodiolide for pancreatic cancer remedy.

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.

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 controls Src- and FAK-dependent phenotypes in squamous carcinoma cells

Eps8 is an actin regulatory scaffold protein whose expression is increased in squamous cell carcinoma (SCC) cells. It forms a complex with both focal adhesion kinase (FAK, also known as PTK2) and Src in SCC cells derived from skin carcinomas induced by administration of the chemical DMBA followed by TPA (the DMBA/TPA model). Here, we describe two new roles for Eps8. Firstly, it controls the spatial distribution of active Src in a FAK-dependent manner. Specifically, Eps8 participates in, and regulates, a biochemical complex with Src and drives trafficking of Src to autophagic structures that SCC cells use to cope with high levels of active Src when FAK is absent. Secondly, when FAK is expressed in SCC cells, thereby meaning active Src becomes tethered at focal adhesion complexes, Eps8 is also recruited to focal adhesions and is required for FAK-dependent polarization and invasion. Therefore, Eps8 is a crucial mediator of Src- and FAK-regulated processes; it participates in specific biochemical complexes and promotes actin re-arrangements that determine the spatial localization of Src, and modulates the functions of Src and FAK during invasive migration.

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.

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.

Silencing of Eps8 blocks migration and invasion in human glioblastoma cell lines

Glioblastoma multiforme (GBM) is the most malignant human primary brain tumor, and its infiltrative nature represents the leading cause for the failure of therapies and tumor recurrences. It is therefore crucial the knowledge of the molecular mechanisms underlying GBM invasion to identify novel therapeutic targets to limit motility. In this study, we evaluated the role of Epidermal growth factor receptor Pathway Substrate 8 (Eps8), a crucial regulator of the actin cytoskeleton dynamics accompanying cell motility and invasion, in GBM migration and invasiveness. We found that silencing of the protein by small interfering RNAs (siRNAs) abrogated the migratory and invasive capacity of three different human GBM cell lines both in 2-dimensional (2-D) and 3-dimensional (3-D) in vitro assays. The inhibitory effect on invasion was maintained independently by the migration mode utilized by the cells in our 3-D model, and was accompanied by an impaired formation of actin-based cytoskeletal protrusive structures. Our data propose Eps8 as a key molecule involved in the control of the intrinsic invasive behavior of GBM cells, and suggest that this protein might represent a useful target for the design of new drugs for the treatment of these tumors.

Eps8 protein facilitates phagocytosis by increasing TLR4-MyD88 protein interaction in lipopolysaccharide-stimulated macrophages

Toll-like receptors (TLRs) are crucial in macrophage phagocytosis, which is pivotal in host innate immune response. However, the detailed mechanism is not fully defined. Here, we demonstrated that the induction of Src and Eps8 in LPS-treated macrophages was TLR4- and MyD88-dependent, and their attenuation reduced LPS-promoted phagocytosis. Confocal microscopy indicated the colocalization of Eps8 and TLR4 in the cytosol and at the phagosome. Consistently, both Eps8 and TLR4 were present in the same immunocomplex regardless of LPS stimulation. Inhibition of this complex formation by eps8 siRNA or overexpression of pleckstrin homology domain-truncated Eps8 (i.e. 261-p97(Eps8)) decreased LPS-induced TLR4-MyD88 interaction and the following activation of Src, focal adhesion kinase, and p38 MAPK. Importantly, attenuation of Eps8 impaired the bacterium-killing ability of macrophages. Thus, Eps8 is a key regulator of the LPS-stimulated TLR4-MyD88 interaction and contributes to macrophage phagocytosis.

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.

Expression of Eps8 correlates with poor survival in oral squamous cell carcinoma

AIMS

Epidermal growth factor receptor pathway substrate 8 (Eps8) is a signaling protein implicated in the development of many human cancers including oral squamous cell carcinoma (OSCC). This study examined the expression of Eps8 and assessed its significance in patients with OSCC.

METHODS

Immunohistochemical staining for Eps8 was conducted in 205 cases of OSCC collected over 7 years. The results were analyzed and correlated with patients' clinical outcomes.

RESULTS

We identified Eps8 expression in 186 of the 205 cases of OSCC (91%) and the aberrance occurred primarily in the cytoplasm of OSCC cells. Univariate analysis revealed that patients with Eps8 expression had significantly poorer 5-year overall survival (OS) than those without it (43% vs 74%, P = 0.014). Eps8 expression was also identified as an independent predictive factor for poorer OS by a multivariate analysis in regression modeling (P = 0.021, HR = 2.7). A Kaplan-Meier analysis showed that patients with positive Eps8 expression had a significantly poorer OS than patients with negative/low Eps8 expression (P = 0.038). The difference in disease-free survival between positive Eps8 expression and negative/low Eps8 expression nearly reached statistical significance (P = 0.051).

CONCLUSION

Eps8 is frequently expressed in OSCC. The aberrant expression of Eps8 closely correlated with poor survival in patients with OSCC.

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.

p190RhoGEF (Rgnef) promotes colon carcinoma tumor progression via interaction with focal adhesion kinase

Focal adhesion kinase (FAK) functions downstream of integrins and growth factor receptors to promote tumor cell motility and invasion. In colorectal cancer, FAK is activated by amidated gastrin, a protumorigenic hormone. However, it is unclear how FAK receives signals from the gastrin receptor or other G-protein-coupled receptors that can promote cell motility and invasion. The Rho guanine-nucleotide exchange factor p190RhoGEF (Rgnef) binds FAK and facilitates fibroblast focal adhesion formation on fibronectin. Here we report that Rgnef mRNA and protein expression are significantly increased during colorectal tumor progression. In human colon carcinoma cells, Rgnef forms a complex with FAK and upon gastrin stimulation, FAK translocates to newly-forming focal adhesions where it facilitates tyrosine phosphorylation of paxillin. short hairpin (shRNA)-mediated knockdown of Rgnef or FAK, or pharmacological inhibition of FAK activity, is sufficient to block gastrin-stimulated paxillin phosphorylation, cell motility, and invadopodia formation in a manner dependent upon upstream cholecystokinin-2 receptor expression. Overexpression of the C-terminal region of Rgnef (Rgnef-C, amino acid 1,279-1,582) but not Rgnef-CΔFAK (amino acid 1,302-1,582 lacking the FAK binding site) disrupted endogenous Rgnef-FAK interaction and prevented paxillin phosphorylation and cell motility stimulated by gastrin. Rgnef-C-expressing cells formed smaller, less invasive tumors with reduced tyrosine phosphorylation of paxillin upon orthotopic implantation, compared with Rgnef-CΔFAK-expressing cells. Our studies identify Rgnef as a novel regulator of colon carcinoma motility and invasion, and they show that a Rgnef-FAK linkage promotes colon carcinoma progression in vivo.

Quantification of beta-catenin signaling components in colon cancer cell lines, tissue sections, and microdissected tumor cells using reaction monitoring mass spectrometry

Reaction monitoring mass spectrometry has emerged as a powerful tool for targeted detection and quantification of proteins in clinical samples. Here, we report the use of gel electrophoresis for protein fractionation and liquid chromatography coupled to multiple reaction monitoring mass spectrometry (LC-MRM) screening for quantitative analysis of components from the Wnt/beta-catenin signaling pathway, which contributes to colon tumor formation and progression. In silico tools are used to design LC-MRM screens for each target protein. Following successful peptide detection, stable isotope labeled peptides are synthesized and developed as internal standards. Then, the assays are implemented in colon cancer cell lines to achieve detection in minimal amounts of cells, compatible with direct translation to clinical specimens. Selected assays are compared with qualitative results from immunoblotting (Westerns) and translated to individual frozen colon tissue sections and laser capture microdissected tumor cells. This LC-MRM platform has been translated from in vitro models to clinical specimens, forming the basis for future experiments in patient assessment.

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.

The effect of focal adhesion kinase gene silencing on 5-fluorouracil chemosensitivity involves an Akt/NF-kappaB signaling pathway in colorectal carcinomas

Multicellular resistance (MCR) is produced because multicellular spheroids (MCSs) are formed with a broad cell-cell connection when cultured in three-dimensions, which limits the clinical treatment efficacy in solid tumors. Focal adhesion kinase (FAK) plays an important role in apoptosis, survival and cell adhesion between cells and their extracellular matrix. In this study, we investigated the expressions of FAK, Akt and NF-kappaB in human colorectal cancer (CRC), and the effects of FAK gene silencing on MCSs formation and 5-fluorouracil (5-FU) chemosensitivity in colon carcinoma MCSs culture cells. In CRC samples, FAK, Akt and NF-kappaB were overexpressed. The positive expression of FAK correlated notably with lymph node metastasis and cellular differentiation. Positive expressions of Akt and NF-kappaB were significantly related to cellular differentiation and lymph node metastasis, respectively. Furthermore, positive expression of FAK correlated with that of Akt and NF-kappaB. The expression of FAK was inhibited significantly by a small hairpin RNA targeting FAK. Knockdown of FAK reversed the formation and aggregation of MCSs, significantly decreased the 50% inhibitory concentration of 5-FU, and markedly increased MCS culture cells apoptosis. These effects were associated with reduced levels of Akt and NF-kappaB. These results indicate that suppressing FAK expression potentiated 5-FU-induced cytotoxicity and contributed to its chemosensitizing effect by suppressing Akt/NF-kappaB signaling in colon carcinoma MCS culture cells. These data also imply that FAK mediates MCR of CRC through the survival signaling pathway FAK/Akt/NF-kappaB.

The interplay between Eps8 and IRSp53 contributes to Src-mediated transformation

As an oncoprotein, Eps8 participates in v-Src-induced cellular transformation. To delineate the underlying mechanism, we conducted a yeast two-hybrid screening and identified IRSp53S, a protein critical in cell mobilization, as one of the Eps8-binding partners from a human brain cDNA library. The association was mediated by the multiple proline-rich regions of Eps8 and the C-terminal SH3-WWB containing domains of IRSp53S. In this study, we observed that Eps8 modulated the expression of IRSp53 in v-Src-transformed cells (IV5), raising the question of whether Eps8/IRSp53 interaction was crucial in carcinogenesis. To address this issue, we generated IV5-expressing irsp53 siRNA cells. Attenuation of IRSp53 reduced cell proliferation of IV5 in culture dish and tumor formation in mice, which could be partly rescued by ectopically expressed human IRSp53S. In addition, IRSp53 knockdown impaired activity of phosphatidylinositol 3-kinase (as reflected by Pi-Ser473 AKT) and Stat3 (as reflected by Pi-Tyr705 Stat3), and reduced cyclin D1 expression that culminated to impede G(1)-phase cell-cycle progression. Ectopically expressed human IRSp53S, but not its Eps8-binding defective mutants (that is, Delta363 and PPPDA), rescued these defects and partly restored cell proliferation. Remarkably, through activation of Src, EGF increased the formation of Eps8/IRSp53 complex and Stat3 activation in HeLa cells. With these results, we show for the first time that IRSp53, through its interaction with Eps8, not only affects cell migration but also dictates cellular growth in cancer cells.

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.

Progress in researches about focal adhesion kinase in gastrointestinal tract

Focal adhesion kinase (FAK) is a 125-kDa non-receptor protein tyrosine. Growth factors or the clustering of integrins facilitate the rapid phosphorylation of FAK at Tyr-397 and this in turn recruits Src-family protein tyrosine kinases, resulting in the phosphorylation of Tyr-576 and Tyr-577 in the FAK activation loop and full catalytic FAK activation. FAK plays a critical role in the biological processes of normal and cancer cells including the gastrointestinal tract. FAK also plays an important role in the restitution, cell survival and apoptosis and carcinogenesis of the gastrointestinal tract. FAK is over-expressed in cancer cells and its over-expression and elevated activities are associated with motility and invasion of cancer cells. FAK has been proposed as a potential target in cancer therapy. Small molecule inhibitors effectively inhibit the kinase activity of FAK and show a potent inhibitory effect for the proliferation and migration of tumor cells, indicating a high potential for application in cancer therapy.

Cytoplasmic Ig-domain proteins: cytoskeletal regulators with a role in human disease

Immunoglobulin domains are found in a wide variety of functionally diverse transmembrane proteins, and also in a smaller number of cytoplasmic proteins. Members of this latter group are usually associated with the actin cytoskeleton, and most of them bind directly to either actin or myosin, or both. Recently, studies of inherited human disorders have identified disease-causing mutations in five cytoplasmic Ig-domain proteins: myosin-binding protein C, titin, myotilin, palladin, and myopalladin. Together with results obtained from cultured cells and mouse models, these clinical studies have yielded novel insights into the unexpected roles of Ig domain proteins in mechanotransduction and signaling to the nucleus. An emerging theme in this field is that cytoskeleton-associated Ig domain proteins are more than structural elements of the cell, and may have evolved to fill different needs in different cellular compartments. Cell Motil. Cytoskeleton 2009. (c) 2009 Wiley-Liss, Inc.

Knockdown of focal adhesion kinase reverses colon carcinoma multicellular resistance

Chemotherapy resistance in solid tumors is broad and encompasses diverse unrelated drugs. Three-dimensional multicellular spheroids (MCSs) are a good model for studying in vitro drug resistance. In the current study, we investigated the role of focal adhesion kinase (FAK) in 5-fluorouracil (5-FU) chemoresistance in colon carcinoma MCS culture cells. The expression of FAK was inhibited significantly by specific small hairpin RNA targeting FAK. The suppression of FAK expression did not affect the growth of spheroid cells. However, silencing of FAK combined with 5-FU treatment significantly decreased the 50% inhibitory concentration (IC(50)) of 5-FU and markedly increased the population of apoptosis cells, which was associated with the reduction of the levels of Akt and nuclear factor-kappa B (NF-kappaB). Moreover, knockdown of FAK could inhibit tumor growth and increase the sensitivity of the tumor to 5-FU in the nude mouse xenograft. These results indicate that while not affecting cellular proliferation in the absence of 5-FU, RNA interference targeting FAK potentiated 5-FU-induced cytotoxicity in vitro and in vivo, and partially reversed multicellular resistance, which may contribute to its chemosensitizing effect through efficiently suppressing Akt/NF-kappaB activity.