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

Predictive data-driven modeling of C-terminal tyrosine function in the EGFR signaling network

The epidermal growth factor receptor (EGFR) has been studied extensively because of its critical role in cellular signaling and association with disease. Previous models have elucidated interactions between EGFR and downstream adaptor proteins or showed phenotypes affected by EGFR. However, the link between specific EGFR phosphorylation sites and phenotypic outcomes is still poorly understood. Here, we employed a suite of isogenic cell lines expressing site-specific mutations at each of the EGFR C-terminal phosphorylation sites to interrogate their role in the signaling network and cell biological response to stimulation. Our results demonstrate the resilience of the EGFR network, which was largely similar even in the context of multiple Y-to-F mutations in the EGFR C-terminal tail, while also revealing nodes in the network that have not previously been linked to EGFR signaling. Our data-driven model highlights the signaling network nodes associated with distinct EGF-driven cell responses, including migration, proliferation, and receptor trafficking. Application of this same approach to less-studied RTKs should provide a plethora of novel associations that should lead to an improved understanding of these signaling networks.

MLK3 Is Associated With Poor Prognosis in Patients With Glioblastomas and Actin Cytoskeleton Remodeling in Glioblastoma Cells

Mixed lineage kinase 3 (MLK3) has been implicated in human melanoma and breast cancers. However, the clinical significance of MLK3 in human gliomas and the underlying cellular and molecular mechanisms remain unclear. We found that MLK3 proteins were highly expressed in high-grade human glioma specimens and especially prevalent in primary and recurrent glioblastoma multiforme (GBM). High levels of MLK3 mRNA were correlated with poor prognosis in patients with isocitrate dehydrogenase (IDH)-wild-type (wt) gliomas. Furthermore, genetic ablation of MLK3 significantly suppressed the migration and invasion abilities of GBM cells and disrupted actin cytoskeleton organization. Importantly, MLK3 directly bound to epidermal growth factor receptor kinase substrate 8 (EPS8) and regulated the cellular location of EPS8, which is essential for actin cytoskeleton rearrangement. Overall, these findings provide evidence that MLK3 upregulation predicts progression and poor prognosis in human IDH-wt gliomas and suggest that MLK3 promotes the migration and invasion of GBM cells by remodeling the actin cytoskeleton via MLK3-EPS8 signaling.

Multicellular 3D Models to Study Tumour-Stroma Interactions

Two-dimensional (2D) cell cultures have been the standard for many different applications, ranging from basic research to stem cell and cancer research to regenerative medicine, for most of the past century. Hence, almost all of our knowledge about fundamental biological processes has been provided by primary and established cell lines cultured in 2D monolayer. However, cells in tissues and organs do not exist as single entities, and life in multicellular organisms relies on the coordination of several cellular activities, which depend on cell–cell communication across different cell types and tissues. In addition, cells are embedded within a complex non-cellular structure known as the extracellular matrix (ECM), which anchors them in a three-dimensional (3D) formation. Likewise, tumour cells interact with their surrounding matrix and tissue, and the physical and biochemical properties of this microenvironment regulate cancer differentiation, proliferation, invasion, and metastasis. 2D models are unable to mimic the complex and dynamic interactions of the tumour microenvironment (TME) and ignore spatial cell–ECM and cell–cell interactions. Thus, multicellular 3D models are excellent tools to recapitulate in vitro the spatial dimension, cellular heterogeneity, and molecular networks of the TME. This review summarizes the biological significance of the cell–ECM and cell–cell interactions in the onset and progression of tumours and focuses on the requirement for these interactions to build up representative in vitro models for the study of the pathophysiology of cancer and for the design of more clinically relevant treatments.

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 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.

A low-molecular-weight compound exerts anticancer activity against breast and lung cancers by disrupting EGFR/Eps8 complex formation

BACKGROUND

Epidermal growth factor receptor (EGFR) and epidermal growth factor receptor pathway substrate 8 (Eps8) have been widely reported to be expressed in various tumors. Eps8 is an important active kinase substrate of EGFR that directly binds to the juxtamembrane (JXM) domain of EGFR to form an EGFR/Eps8 complex. The EGFR/Eps8 complex is involved in regulating cancer progression and might be an ideal target for antitumor therapy. This study focused on the screening of small-molecule inhibitors that target the EGFR/Eps8 complex in breast cancer and non-small cell lung cancer (NSCLC).

METHODS

In silico virtual screening was used to identify small-molecule EGFR/Eps8 complex inhibitors. These compounds were screened for the inhibition of A549 and BT549 cell viability. The direct interaction between EGFR and Eps8 was measured using coimmunoprecipitation (CoIP) and JXM domain replacement assays. The antitumor effects of the inhibitors were analyzed in cancer cells and xenograft models. An acute toxicity study of EE02 was performed in a mouse model. In addition, the effect of the EE02 inhibitor on the protein expression of elements downstream of the EGFR/Eps8 complex was determined by western blotting and protein chip assays.

RESULTS

In this study of nearly 390,000 compounds screened by virtual database screening, the top 29 compounds were identified as candidate small-molecule EGFR/Eps8 complex inhibitors and evaluated by using cell-based assays. The compound EE02 was identified as the best match to our selection criteria. Further investigation demonstrated that EE02 directly bound to the JXM domain of EGFR and disrupted EGFR/Eps8 complex formation. EE02 selectively suppressed growth and induced apoptosis in EGFR-positive and Eps8-positive breast cancer and NSCLC cells. More importantly, the PI3K/Akt/mTOR and MAPK/Erk pathways downstream of the EGFR/Eps8 complex were suppressed by EE02. In addition, the suppressive effect of EE02 on tumor growth in vivo was comparable to that of erlotinib at the same dose.

CONCLUSIONS

We identified EE02 as an EGFR/Eps8 complex inhibitor that demonstrated promising antitumor effects in breast cancer and NSCLC. Our data suggest that the EGFR/Eps8 complex offers a novel cancer drug target.

CD19 chimeric antigen receptor-redirected T cells combined with epidermal growth factor receptor pathway substrate 8 peptide-derived dendritic cell vaccine in leukemia

BACKGROUND

Chimeric antigen receptor (CAR)-T cell therapy opens a new era for cancer treatment. However, in prolonged follow-up, relapse has emerged as one of the major obstacles. Dendritic cell (DC) vaccination is a promising treatment to eradicate tumor cells and prevent relapse. The epidermal growth factor receptor (EGFR) pathway substrate 8 (Eps8) gene is involved in regulating cancer progression and is considered an attractive target for specific cancer immunotherapy. The purpose of this study was to explore a combinatorial therapy using CAR-T cells and a DC vaccine such as Eps8-DCs to increase leukemia treatment efficacy.

METHODS

We pulsed DCs with Eps8-derived peptides to generate Eps8-DCs, engineered T cells to express a second-generation CAR specific for CD19, and analyzed the effects of the Eps8-DCs on the in vitro expansion, phenotype and effector functions of the CD19 CAR-T cells.

RESULTS

The Eps8-DCs significantly reduced the activation-induced cell death and enhanced the proliferative potential of CAR-T cells during in vitro expansion. In addition, the expanded T cells co-cultured with the Eps8-DCs exhibited an increased percentage of central memory T cells (Tcms) and a decreased percentage of effector memory T cells (Tems). The Eps8-DCs enhanced CD19 CAR-T cell immune functions, including cytokine production, CD107a degranulation activity and cytotoxicity.

DISCUSSION

This study demonstrates that Eps8-DCs exert synergistic effect on CD19 targeting CAR-T cells and paves the way for clinical trials using the combination of DC vaccination and engineered T cells in relapsed leukemia.

Inhibition of Chloride Intracellular Channel 1 (CLIC1) as Biguanide Class-Effect to Impair Human Glioblastoma Stem Cell Viability

The antidiabetic biguanide metformin exerts antiproliferative effects in different solid tumors. However, during preclinical studies, metformin concentrations required to induce cell growth arrest were invariably within the mM range, thus difficult to translate in a clinical setting. Consequently, the search for more potent metformin derivatives is a current goal for new drug development. Although several cell-specific intracellular mechanisms contribute to the anti-tumor activity of metformin, the inhibition of the chloride intracellular channel 1 activity (CLIC1) at G1/S transition is a key events in metformin antiproliferative effect in glioblastoma stem cells (GSCs). Here we tested several known biguanide-related drugs for the ability to affect glioblastoma (but not normal) stem cell viability, and in particular: phenformin, a withdrawn antidiabetic drug; moroxydine, a former antiviral agent; and proguanil, an antimalarial compound, all of them possessing a linear biguanide structure as metformin; moreover, we evaluated cycloguanil, the active form of proguanil, characterized by a cyclized biguanide moiety. All these drugs caused a significant impairment of GSC proliferation, invasiveness, and self-renewal reaching IC₅₀ values significantly lower than metformin, (range 0.054–0.53 mM vs. 9.4 mM of metformin). All biguanides inhibited CLIC1-mediated ion current, showing the same potency observed in the antiproliferative effects, with the exception of proguanil which was ineffective. These effects were specific for GSCs, since no (or little) cytotoxicity was observed in normal umbilical cord mesenchymal stem cells, whose viability was not affected by metformin and moroxydine, while cycloguanil and phenformin induced toxicity only at much higher concentrations than required to reduce GSC proliferation or invasiveness. Conversely, proguanil was highly cytotoxic also for normal mesenchymal stem cells. In conclusion, the inhibition of CLIC1 activity represents a biguanide class-effect to impair GSC viability, invasiveness, and self-renewal, although dissimilarities among different drugs were observed as far as potency, efficacy and selectivity as CLIC1 inhibitors. Being CLIC1 constitutively active in GSCs, this feature is relevant to grant the molecules with high specificity toward GSCs while sparing normal cells. These results could represent the basis for the development of novel biguanide-structured molecules, characterized by high antitumor efficacy and safe toxicological profile.

A dual-function epidermal growth factor receptor pathway substrate 8 (Eps8)-derived peptide exhibits a potent cytotoxic T lymphocyte-activating effect and a specific inhibitory activity

The identification and characterization of tumor-associated antigens (TAAs) that generate specific cytotoxic T lymphocytes (CTLs) are vital to the development of cancer immunotherapy. The epidermal growth factor receptor (EGFR) pathway substrate 8 gene (Eps8) is involved in regulating cancer progression and might be an ideal antigen. In this study, we searched for novel human leukocyte antigen (HLA)-A*2402-restricted epitopes derived from the Eps8 protein via the HLA-binding prediction algorithm. Among four candidates, peptides 327 (EFLDCFQKF), 534 (KYAKSKYDF) and 755 (LFSLNKDEL) induced peptide-specific CTLs to secrete higher levels of interferon-gamma (IFN-γ) and showed enhanced cytotoxic activity against malignant cancer cells. Our results demonstrated that peptide-specific CTLs showed effective antitumor responses, including upregulation of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-α), granzyme B and perforin. Treatment with peptide-sensitized peripheral blood mononuclear cells (PBMCs) significantly reduced the tumor growth in vivo compared with the non-peptide-sensitized PBMC treatment. Importantly, our results indicated that peptide 327 may interfere with EGFR signaling by mechanistically disrupting Eps8/EGFR complex formation. We extended this observation that peptide 327 also suppressed the viability of cancer cells, blocked EGFR signal pathway and reduced the expression of downstream targets. Notably, conjugation of peptide 327 to the TAT sequence (TAT-327) resulted in potent antitumor activity and selective insertion into cancer cell membranes, where it adopted a punctate distribution. Furthermore, peptide 327 and TAT-327 displayed anticancer properties in xenograft models. Our results indicated that 327, 534 and 755 were novel HLA-A*2402-restricted epitopes from Eps8. By inhibiting the Eps8/EGFR interaction, peptide 327 and TAT-327 may serve as novel peptide inhibitors, which could provide an innovative approach for treating various cancers.

Cross-talk between sphingosine-1-phosphate and EGFR signaling pathways enhances human glioblastoma cell invasiveness

We show that glioblastoma multiform (GBM) cells overexpressing the constitutively active form of the epidermal growth factor receptor [epidermal growth factor receptor variant III (EGFRvIII) and U87MG human GBM cell line overexpressing EGFRvIII (EGFR+) cells] possess greater invasive properties and have higher levels of extracellular sphingosine-1-phosphate (S1P) and increased sphingosine kinase-1 (SK1) activity than the empty vector-expressing cells. Notably, the inhibition of SK1 or S1P receptors decreases the invasiveness of EGFR+ cells. Moreover, EGFR and MEK1 inhibitors reduce both SK1 activation and cell invasion, suggesting that the enhanced invasiveness observed in the EGFR+ cells depends on the increased S1P secretion, downstream of the EGFRvIII-ERK-SK1-S1P pathway. Altogether, the results of the present study indicate that, in GBM cells, EGFRvIII is connected with the S1P signaling pathway to enhance cell invasiveness and tumor progression.

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.

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.

The effects of focal adhesion kinase on the motility, proliferation and apoptosis of Caco2 and SMMC-7721 cells

Focal adhesion kinase (FAK) plays important roles in cancer development. However, the significance of FAK expression in colorectal carcinoma and hepatocellular carcinoma has not been clarified. This study aims to explore the roles FAK played in the progression of colorectal carcinoma and hepatocellular carcinoma. RNAi method was used to inhibit the expression of FAK in Caco2 and SMMC-7721 cells. Reverse transcriptase polymerase chain reaction analysis and Western blot analysis were used to examine mRNA and protein expression of FAK. Then, the proliferation, motility and apoptosis of both types of cells were detected using MTT assay, wound healing/transwell assay and nuclear staining assay. The microstructure changes (F-actin, β-tubulin and lamin B1) of SMMC-7721 cells were visualized by immunofluorescence. FAK was overexpressed in both cell lines and down-regulation of FAK resulted in suppression of cell proliferation, inhibition of cell migration and invasion. The apoptosis of cells was increased significantly following the FAK expression inhibition. Moreover, actin polymerization, β-tubulin and lamin B1 expression of cells were significantly decreased. The results highlight the role of FAK in the progression of cancers. These findings suggest FAK serve as a potential therapeutic target for cancer therapy.

Indatraline inhibits Rho- and calcium-mediated glioblastoma cell motility and angiogenesis

Glioblastoma multiforme (GBM) is the most common and lethal primary brain tumor of the central nervous system (CNS). As an attempt to identify drugs for GBM therapeutics, phenotypic assays were used to screen 1000 chemicals from a clinical compound library. GBM subtypes exhibited different capabilities to induce angiogenesis when cultured on Matrigel; proneural cells migrated and formed a tube-like structure without endothelial cells. Among the compounds screened, indatraline, a nonselective monoamine transporter inhibitor, suppressed these morphological changes; it dose dependently inhibited cell spreading, migration, and in vitro/in vivo tube formation. In addition to intracellular calcium concentration, indatraline increased the level of Rho GTPase and its activity. Moreover, indatraline downregulated angiogenesis-related genes such as IGFBP2, PTN, VEGFA, PDGFRA, and VEGFR as well as nestin, a stem cell marker. These findings collectively suggest that the activation of Rho GTPase and the suppression of angiogenesis-related factors mediate the antiangiogenic activity of indatraline in proneural GBM culture.

Systematic review of protein biomarkers of invasive behavior in glioblastoma

Glioblastoma (GBM) is an aggressive and incurable brain tumor with a grave prognosis. Recurrence is inevitable even with maximal surgical resection, in large part because GBM is a highly invasive tumor. Invasiveness also contributes to the failure of multiple cornerstones of GBM therapy, including radiotherapy, temozolomide chemotherapy, and vascular endothelial growth factor blockade. In recent years there has been significant progress in the identification of protein biomarkers of invasive phenotype in GBM. In this article, we comprehensively review the literature and survey a broad spectrum of biomarkers, including proteolytic enzymes, extracellular matrix proteins, cell adhesion molecules, neurodevelopmental factors, cell signaling and transcription factors, angiogenic effectors, metabolic proteins, membrane channels, and cytokines and chemokines. In light of the marked variation seen in outcomes in GBM patients, the systematic use of these biomarkers could be used to form a framework for better prediction, prognostication, and treatment selection, as well as the identification of molecular targets for further laboratory investigation and development of nascent, directed therapies.