Inhibition of epithelial-mesenchymal transition by cetuximab via the EGFR-GEP100-Arf6-AMAP1 pathway in head and neck cancer

Monoclonal antibody cetuximab impairs matrix metalloproteinases 2 and 9, epithelial-mesenchymal transition and cell migration in feline oral squamous cell carcinoma in vitro

Feline oral squamous cell carcinoma (FOSCC) is characterised by invasive and metastatic behaviour and is poorly responsive to current treatments, hence the need for new therapeutic strategies. FOSCC shares molecular targets with human head and neck squamous cell carcinoma (HNSCC), among these the epidermal growth factor receptor. Cetuximab is an anti-epidermal growth factor receptor monoclonal antibody employed in the therapy of HNSCC and, interestingly, previous work in vitro suggested that it displays cytostatic and cytotoxic properties also against FOSCC. With the present study, we aimed at further investigating the effects of cetuximab on invasion and metastasis pathways proven to be relevant in human patients. To this purpose, FOSCC cell lines SCCF1, SCCF2 and SCCF3 were treated with cetuximab for 48/72 h and subjected to Western blot for matrix metalloproteinases-2/9 (MMP-2/9) and epithelial-mesenchymal transition markers vimentin, E-, P- and N-cadherin. Treatment with cetuximab resulted in downregulation of MMP-2/-9 in all of the three cell lines in a dose-dependent manner. Moreover, cetuximab downregulated vimentin and P-cadherin in SCCF1, upregulated E-cadherin whilst downregulating P-/N-cadherins in SCCF2, and impaired P-/N-cadherins in SCCF3. An in vitro scratch test also demonstrated that cetuximab delayed cell migration in SCCF3. These data suggest that cetuximab mitigates invasion and metastasis processes by impairing MMPs and epithelial-mesenchymal transition pathways in FOSCC, indicating that this monoclonal antibody may help to counteract malignant progression and improve the management of locally invasive disease.

Arf6 as a therapeutic target: Structure, mechanism, and inhibitors

ADP-ribosylation factor 6 (Arf6), a small G-protein of the Ras superfamily, plays pivotal roles in multiple cellular events, including exocytosis, endocytosis, actin remodeling, plasma membrane reorganization and vesicular transport. Arf6 regulates the progression of cancer through the activation of cell motility and invasion. Aberrant Arf6 activation is a potential therapeutic target. This review aims to understand the comprehensive function of Arf6 for future cancer therapy. The Arf6 GEFs, protein structure, and roles in cancer have been summarized. Comprehending the mechanism underlying Arf6-mediated cancer cell growth and survival is essential. The structural features of Arf6 and its efforts are discussed and may be contributed to the discovery of future novel protein-protein interaction inhibitors. In addition, Arf6 inhibitors and mechanism of action are listed in the table. This review further emphasizes the crucial roles in drug resistance and attempts to offer an outlook of Arf6 in cancer therapy.

ADP Ribosylation Factor 6 Relieves Airway Inflammation and Remodeling by Inhibiting Ovalbumin Induced-Epithelial Mesenchymal Transition in Experimental Asthma, Possibly by Regulating of E2F Transcription Factor 8

BACKGROUND

Childhood asthma is a major global health concern. ADP-ribosylation factor 6 (ARF6) is a low-molecular-weight GTPase; however, its role in childhood asthma remains unclear.

METHODS

Ovalbumin (OVA)-challenged neonatal mice and transforming growth factor-β1 (TGF-β1)-induced BEAS-2B cells were used as in vivo and in vitro models of childhood asthma, respectively.

RESULTS

Upon OVA stimulation, ARF6 expression was upregulated in the lung tissue. Neonatal mice administered SehinH3 (an ARF6 inhibitor) exhibited improved pulmonary pathological injury, along with reduced inflammatory cell infiltration in the lungs and cytokine release in bronchial alveolar lavage fluid and serum (interleukin [IL]-3, IL-5, IL-13, IgE, and OVA-specific IgE). SehinH3 treatment restrained epithelial - mesenchymal transition (EMT) in the lungs of asthmatic mice, as evidenced by increased E-cadherin and decreased N-cadherin and α-smooth muscle actin expression. Different TGF-β1 exposures to BEAS-2B cells induced a time- and dose-dependent increase in ARF6 expression in vitro. Upon TGF-β1 stimulation, ARF6 knockdown repressed EMT and SehinH3 treatment caused similar results in BEAS-2B cells. The transcription factor E2F8 is involved in diverse biological functions and its increased expression was confirmed in vivo and in vitro. Dual-luciferase assays confirmed that E2F8 binds to the ARF6 promoter and promotes its transcriptional activity. In vitro results revealed that E2F8 silencing suppressed EMT, whereas rescue experiments showed that ARF6 overexpression partly reversed these phenomena.

CONCLUSION

Our study showed that ARF6 is associated with childhood asthma progression and may be positively regulated by E2F8. These results provide insight into the pathogenesis and treatment of childhood asthma.

Extracellular Vesicles and Epidermal Growth Factor Receptor Activation: Interplay of Drivers in Cancer Progression

Extracellular vesicles (EVs) are of great interest to study the cellular mechanisms of cancer development and to diagnose and monitor cancer progression. EVs are a highly heterogeneous population of cell derived particles, which include microvesicles (MVs) and exosomes (EXOs). EVs deliver intercellular messages transferring proteins, lipids, nucleic acids, and metabolites with implications for tumour progression, invasiveness, and metastasis. Epidermal Growth Factor Receptor (EGFR) is a major driver of cancer. Tumour cells with activated EGFR could produce EVs disseminating EGFR itself or its ligands. This review provides an overview of EVs (mainly EXOs and MVs) and their cargo, with a subsequent focus on their production and effects related to EGFR activation. In particular, in vitro studies performed in EGFR-dependent solid tumours and/or cell cultures will be explored, thus shedding light on the interplay between EGFR and EVs production in promoting cancer progression, metastases, and resistance to therapies. Finally, an overview of liquid biopsy approaches involving EGFR and EVs in the blood/plasma of EGFR-dependent tumour patients will also be discussed to evaluate their possible application as candidate biomarkers.

Potential use of EGFR-targeted molecular therapies for tumor suppressor CYLD-negative and poor prognosis oral squamous cell carcinoma with chemoresistance

Background

Tumor suppressor CYLD dysfunction by loss of its expression, triggers malignant transformation, especially drug resistance and tumor invasion/metastasis. Although loss of CYLD expression is significantly associated with poor prognosis in a large variety of tumors, no clinically-effective treatment for CYLD-negative cancer patients is available.

Methods

We focused on oral squamous cell carcinoma (OSCC), and sought to develop novel therapeutic agents for CYLD-negative cancer patients with poor prognosis. CYLD-knockdown OSCC cells by using CYLD-specific siRNA, were used to elucidate and determine the efficacy of novel drug candidates by evaluating cell viability and epithelial-mesenchymal transition (EMT)-like change. Therapeutic effects of candidate drug on cell line-derived xenograft (CDX) model and usefulness of CYLD as a novel biomarker using patient-derived xenograft (PDX) model were further investigated.

Results

CYLD-knockdown OSCC cells were resistant for all currently-available cytotoxic chemotherapeutic agents for OSCC, such as, cisplatin, 5-FU, carboplatin, docetaxel, and paclitaxel. By using comprehensive proteome analysis approach, we identified epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, played key roles in CYLD-knockdown OSCC cells. Indeed, cell survival rate in the cisplatin-resistant CYLD-knockdown OSCC cells was markedly inhibited by treatment with clinically available EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib. In addition, gefitinib was significantly effective for not only cell survival, but also EMT-like changes through inhibiting transforming growth factor-β (TGF-β) signaling in CYLD-knockdown OSCC cells. Thereby, overall survival of CYLD-knockdown CDX models was significantly prolonged by gefitinib treatment. Moreover, we found that CYLD expression was significantly associated with gefitinib response by using PDX models.

Conclusions

Our results first revealed that EGFR-targeted molecular therapies, such as EGFR-TKIs, could have potential to be novel therapeutic agents for the CYLD-negative OSCC patients with poor prognosis.

Long Non-Coding RNA MDFIC-7 Promotes Chordoma Progression Through Modulating the miR-525-5p/ARF6 Axis

Background

Chordoma, an extremely rare malignant tumor, remains difficult to be cured because of its strong local invasiveness and high recurrence rate. Long non-coding RNAs (lncRNAs) have been demonstrated to play multiple roles in various cancers. The purpose of this study was to investigate the modulatory function of lncRNA MDFIC-7 in chordoma and to elucidate its underlying mechanisms.

Methods

Quantitative real-time polymerase chain reaction was performed to detect the expression of lncRNA MDFIC-7 in tumor tissues and adjacent nontumorous tissues collected from 15 chordoma patients, as well as in chordoma cell lines. Gene silencing and overexpression experiments were carried out by RNA interference and lentiviral transduction. The effect of lncRNA MDFIC-7 on the proliferation of chordoma cells was evaluated by cell counting kit-8 assay, colony formation assay and xenograft tumor experiments. RNA immunoprecipitation and dual luciferase reporter assays were conducted to evaluate the binding between lncRNA MDFIC-7 and miRNA-525-5p and the interaction between miR-525-5p and the 3′ untranslated region of ADP-ribosylation factor 6 (ARF6) mRNA. The glycolytic capacity and mitochondrial function of chordoma cells were measured by the Seahorse Bioscience XF96 Extracellular Flux Analyzer.

Results

The expression of lncRNA MDFIC-7 was higher in chordoma tumor tissues than in adjacent non-tumor tissues. Downregulation of lncRNA MDFIC-7 reduced colony formation and cell proliferation in chordoma cells and decreased xenograft tumor growth in a nude mouse model. Moreover, lncRNA MDFIC-7 knockdown attenuated the Warburg effect in chordoma cells and xenograft tumors. LncRNA MDFIC-7 knockdown elevated miR-525-5p levels and decreased ARF6 expressions. Overexpression of ARF6 reversed the inhibitory effect of lncRNA MDFIC-7 knockdown on cell proliferation and the Warburg effect in chordoma cells and xenograft tumors. Mechanistically, lncRNA MDFIC-7, as a molecular sponge of miR-525-5p, negatively regulated miR-525-5p expression and promoted the gene expression of ARF6, a miR-525-5p target.

Conclusion

Our findings demonstrate that lncRNA MDFIC-7 acts as a molecular sponge to competitively bind to miR-525-5p and promote expression of ARF6. The lncRNA MDFIC-7/miR-525-5p/ARF6 axis regulates chordoma progression and the Warburg effect in chordoma, suggesting that lncRNA MDFIC-7 and miR-525-5p could be promising therapeutic targets for the treatment of chordoma.

Cooperation and Interplay between EGFR Signalling and Extracellular Vesicle Biogenesis in Cancer

Epidermal growth factor receptor (EGFR) takes centre stage in carcinogenesis throughout its entire cellular trafficking odyssey. When loaded in extracellular vesicles (EVs), EGFR is one of the key proteins involved in the transfer of information between parental cancer and bystander cells in the tumour microenvironment. To hijack EVs, EGFR needs to play multiple signalling roles in the life cycle of EVs. The receptor is involved in the biogenesis of specific EV subpopulations, it signals as an active cargo, and it can influence the uptake of EVs by recipient cells. EGFR regulates its own inclusion in EVs through feedback loops during disease progression and in response to challenges such as hypoxia, epithelial-to-mesenchymal transition and drugs. Here, we highlight how the spatiotemporal rules that regulate EGFR intracellular function intersect with and influence different EV biogenesis pathways and discuss key regulatory features and interactions of this interplay. We also elaborate on outstanding questions relating to EGFR-driven EV biogenesis and available methods to explore them. This mechanistic understanding will be key to unravelling the functional consequences of direct anti-EGFR targeted and indirect EGFR-impacting cancer therapies on the secretion of pro-tumoural EVs and on their effects on drug resistance and microenvironment subversion.

Arf6 regulates RhoB subcellular localization to control cancer cell invasion

The ADP-ribosylation factor 6 (Arf6) is a small GTPase that regulates endocytic recycling processes in concert with various effectors. Arf6 controls cytoskeletal organization and membrane trafficking; however, the detailed mechanisms of regulation remain poorly understood. Here, we report that Arf6 forms a complex with RhoB. The interaction between RhoB and Arf6 is mediated by the GCI (glycine, cysteine, and isoleucine) residues (188-190) of RhoB. Specific targeting of Arf6 to plasma membrane or mitochondrial membranes promotes recruitment and colocalization of RhoB to these membrane microdomains. Arf6 depletion promotes the loss of RhoB from endosomal membranes and leads to RhoB degradation through an endolysosomal pathway. This results in defective actin and focal adhesion dynamics and increased 3D cell migration upon activation of the Met receptor tyrosine kinase. Our findings identify a novel regulatory mechanism for RhoB localization and stability by Arf6 and establish the strict requirement of Arf6 for RhoB-specific subcellular targeting to endosomes and biological functions.

Design, synthesis, and biological study of 4-[(2-nitroimidazole-1H-alkyloxyl)aniline]-quinazolines as EGFR inhibitors exerting cytotoxicities both under normoxia and hypoxia

Purpose

In order to get novel EGFR inhibitors exerting more potency in tumor hypoxia than in normoxia.

Methods

A series of 4-[(2-nitroimidazole-1H-alkyloxyl)aniline]-quinazolines were designed and synthesized, and their in vitro cytotoxicity and EGFR inhibitory activity were evaluated. Molecule docking study was performed for the representative compound.

Results

The structure-activity relationship (SAR) studies revealed that compounds bearing both meta-chloride and para-(2-nitroimidazole-1H-alkyloxy) groups on the aniline displayed potent inhibitory activities both in enzymatic and cellular levels. The most promising compound 16i potently inhibited EGFR with an IC₅₀ value of 0.12 μM. Meanwhile, it manifested more potent cytotoxicity than the positive control lapatinib under tumor normoxia and hypoxia conditions (IC₅₀ values of 1.59 and 1.09 μM against A549 cells, 2.46 and 1.35 μM against HT-29 cells, respectively). The proposed binding model of 16i in complex with EGFR was displayed by the docking results.

Conclusion

This study provides insights for developing hypoxia-activated kinase inhibitors.

GEP100/ARF6 regulates VEGFR2 signaling to facilitate high-glucose-induced epithelial-mesenchymal transition and cell permeability in retinal pigment epithelial cells

Cell permeability and epithelial-mesenchymal transition (EMT) were found to be enhanced in diabetic retinopathy, and the aim of this study was to investigate the underlying mechanism. ARPE-19 cell line or primary retinal pigment epithelial (RPE) cells were cultured under high or normal glucose conditions. Specific shRNAs were employed to knock down ADP-ribosylation factor 6 (ARF6), GEP100, or VEGF receptor 2 (VEGFR2) in ARPE-19 or primary RPE cells. Cell migration ability was measured using Transwell assay. Western blotting was used to measure indicated protein levels. RPE cells treated with high glucose showed increased cell migration, paracellular permeability, EMT, and expression of VEGF. Knockdown of VEGFR2 inhibited the high-glucose-induced effects on RPE cells via inactivation of ARF6 and MAPK pathways. Knockdown ARF6 or GEP100 led to inhibition of high-glucose-induced effects via inactivation of VEGFR2 pathway. Knockdown of ARF6, but not GEP100, decreased high-glucose-induced internalization of VEGFR2. High-glucose enhances EMT and cell permeability of RPE cells through activation of VEGFR2 and ARF6/GEP100 pathways, which form a positive feedback loop to maximize the activation of VEGF/VEGFR2 signaling.

Knockdown of Arf6 increases drug sensitivity and inhibits proliferation, migration and invasion in gastric cancer SGC-7901 cells

ADP-ribosylation factor 6 (Arf6), a member of the ADP-ribosylation factor family, is overexpressed in different types of cancer cell and promotes invasion, metastasis and drug resistance. However, the potential functions of Arf6 in gastric cancer (GC), and the molecular mechanism underlying these functions, remain to be fully elucidated. In the present study, the results demonstrated that in vitro knockdown of Arf6 decreased proliferation, colony formation, migration and invasion in SGC-7901 cells. Arf6 knockdown also markedly decreased the activity of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. Furthermore, knockdown of Arf6 was associated with elevated chemosensitivity of SGC-7901 cells to 5-fluorouracil through inactivation of the ERK1/2 signaling pathway. Taken together, these results suggest that Arf6 is involved in regulating proliferation, migration, invasion and drug resistance in GC, and may be a potential therapeutic target for the treatment of GC.

Parametric Linkage Analysis Identifies Five Novel Genome-Wide Significant Loci for Familial Lung Cancer

OBJECTIVE

One of four American cancer patients dies of lung cancer. Environmental factors such as tobacco smoking are known to affect lung cancer risk. However, there is a genetic factor to lung cancer risk as well. Here, we perform parametric linkage analysis on family-based genotype data in an effort to find genetic loci linked to the disease.

METHODS

197 individuals from families with a high-risk history of lung cancer were recruited and genotyped using an Illumina array. Parametric linkage analyses were performed using an affected-only phenotype model with an autosomal dominant inheritance using a disease allele frequency of 0.01. Three types of analyses were performed: single variant two-point, collapsed haplotype pattern variant two-point, and multipoint analysis.

RESULTS

Five novel genome-wide significant loci were identified at 18p11.23, 2p22.2, 14q13.1, 16p13, and 20q13.11. The families most informative for linkage were also determined.

CONCLUSIONS

The 5 novel signals are good candidate regions, containing genes that have been implicated as having somatic changes in lung cancer or other cancers (though not in germ line cells). Targeted sequencing on the significant loci is planned to determine the causal variants at these loci.

Roles of Arf6 in cancer cell invasion, metastasis and proliferation

ADP-ribosylation factor 6 (Arf6), a member of small GTPases ADP-ribosylation factor (Arf) family, expresses widely in mammalian cells and mainly regulates the functions of membrane traffic and actin remodeling. Current studies indicated that the activation and high expression of Arf6 protein may be significantly correlated with the invasion and metastasis of several tumors, such as breast cancer, pancreatic cancer, lung cancer, etc. Meanwhile, the ability of tumor invasion and metastasis can be suppressed when Arf6 activity is blocked by the inhibitors or small-interfering RNAs of Arf6. To explore the precisely potential mechanisms between Arf6 and the process of tumor invasion, metastasis and proliferation, we concludes the functions and potential signaling pathways of Arf6 in tumor cells and provides an overview about clinical prospects of Arf6 in the screening, diagnosis, treatment and evaluation of prognosis of neoplasms.