Knockdown of EGFR inhibits growth and invasion of gastric cancer cells

Effects of catechin on the malignant biological behavior of gastric cancer cells through the PI3K/Akt signaling pathway

Catechin is a kind of flavonoids, mainly derived from the plant Camellia sinensis. It has a strong antioxidant effect, and it also has significant therapeutic effects on anti-cancer, anti-diabetes, and anti-infection. This study was intended to look at how catechin affected the malignant biological activity of gastric cancer cells. We used databases to predict the targets of catechin and the pathogenic targets of gastric cancer. Venn diagram was used to find the intersection genes, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses were performed on intersection genes. Using the STRING database, the Protein-Protein Interaction (PPI) network was built. The top 8 genes were screened by Cytoscape 3.9.1, then their binding was verified by molecular docking. The proliferation ability, cell cycle, apoptosis and migration of gastric cancer cells were detected, as well as the protein expression levels of PI3K, p-AKT, and AKT and the mRNA expression levels of AKT1, VEGFA, EGFR, HRAS, and HSP90AA1 in gastric cancer cells. Our research revealed that different concentrations of catechin could effectively inhibit the proliferation and migration of gastric cancer cells, regulate the cell cycle, and promote the death of these cells, and it's possible that the PI3K/Akt pathway was crucial in mediating this impact. Moreover, adding the PI3K/Akt pathway agonist significantly reduced the promoting effect of catechin on the apoptosis of gastric cancer cells. This study suggested that catechin was a potential drug for the treatment of gastric cancer.

EGFR and PI3K Signalling Pathways as Promising Targets on Circulating Tumour Cells from Patients with Metastatic Gastric Adenocarcinoma

The prognosis for metastatic gastric adenocarcinoma (mGAC) remains poor. Gene alterations in receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and their downstream effectors including catalytic subunit alpha of the phosphatidylinositol 3-kinase (PIK3CA) are common in mGAC. Targeted RTK and phosphatidylinositol-3-kinase (PI3K) treatments have demonstrated clinical benefits in other solid tumours and are key potential targets for clinical development against mGAC given the presence of recurrent alterations in these pathways. Furthermore, combination RTK/PI3K treatments may overcome compensatory mechanisms that arise using monotherapies, leading to improved patient outcomes. Herein, we investigated RTK/PI3K single and combination drug responses against our unique human mGAC-derived PIK3CA gain-of-function mutant, human epidermal growth factor receptor 2 (HER2)-negative, EGFR-expressing circulating tumour cell line, UWG02CTC, under two- and three-dimensional culture conditions to model different stages of metastasis. UWG02CTCs were highly responsive to the PI3K p110α-subunit targeted drugs PIK-75 (IC50 = 37.0 ± 11.1 nM) or alpelisib (7.05 ± 3.7 µM). Drug sensitivities were significantly increased in 3D conditions. Compensatory MAPK/ERK pathway upregulation by PI3K/Akt suppression was overcome by combination treatment with the EGFR inhibitor gefitinib, which was strongly synergistic. PIK-75 plus gefitinib significantly impaired UWG02CTC invasion in an organotypic assay. In conclusion, UWG02CTCs are a powerful ex vivo mGAC drug responsiveness model revealing EGFR/PI3K-targeted drugs as a promising combination treatment option for HER2-negative, RAS wild-type mGAC patients.

Endosomal Arl4A attenuates EGFR degradation by binding to the ESCRT-II component VPS36

Ligand-induced epidermal growth factor receptor (EGFR) endocytosis followed by endosomal EGFR signaling and lysosomal degradation plays important roles in controlling multiple biological processes. ADP-ribosylation factor (Arf)-like protein 4 A (Arl4A) functions at the plasma membrane to mediate cytoskeletal remodeling and cell migration, whereas its localization at endosomal compartments remains functionally unknown. Here, we report that Arl4A attenuates EGFR degradation by binding to the endosomal sorting complex required for transport (ESCRT)-II component VPS36. Arl4A plays a role in prolonging the duration of EGFR ubiquitinylation and deterring endocytosed EGFR transport from endosomes to lysosomes under EGF stimulation. Mechanistically, the Arl4A-VPS36 direct interaction stabilizes VPS36 and ESCRT-III association, affecting subsequent recruitment of deubiquitinating-enzyme USP8 by CHMP2A. Impaired Arl4A-VPS36 interaction enhances EGFR degradation and clearance of EGFR ubiquitinylation. Together, we discover that Arl4A negatively regulates EGFR degradation by binding to VPS36 and attenuating ESCRT-mediated late endosomal EGFR sorting.

Prognostic biomarkers and molecular pathways mediating Helicobacter pylori–induced gastric cancer: a network-biology approach

Cancer of the stomach is the second most frequent cancer-related death worldwide. The survival rate of patients with gastric cancer (GC) remains fragile. There is a requirement to discover biomarkers for prognosis approaches. Helicobacter pylori in the stomach is closely associated with the progression of GC. We identified the genes associated with poor/favorable prognosis in H. pylori–induced GC. Multivariate statistical analysis was applied on the Gene Expression Omnibus (GEO) dataset GSE54397 to identify differentially expressed miRNAs (DEMs) in gastric tissues with H. pylori–induced cancer compared with the H. pylori–positive with non-cancerous tissue. A protein interaction map (PIM) was built and subjected to DEMs targets. The enriched pathways and biological processes within the PIM were identified based on substantial clusters. Thereafter, the most critical genes in the PIM were illustrated, and their prognostic impact in GC was investigated. Considering p-value less than 0.01 and |Log2 fold change| as >1, five microRNAs demonstrated significant changes among the two groups. Gene functional analysis revealed that the ubiquitination system, neddylation pathway, and ciliary process are primarily involved in H. pylori–induced GC. Survival analysis illustrated that the overexpression of DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, and TXNIP was associated with poor prognosis, while increased MRPS5 expression was related to a favorable prognosis in GC patients. DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, TXNIP, and MRPS5 may be considered prognostic biomarkers for H. pylori–induced GC. However, experimental validation is necessary in the future.

Substrate stiffness regulates the recurrent glioblastoma cell morphology and aggressiveness

Recurrent glioblastoma is highly aggressive with currently no specific treatment regime. Therefore, to identify novel therapeutic targets for recurrent GBM, we used a cellular model developed in our lab from commercially available cell line U87MG and patient-derived cultures that allows the comparison between radiation naïve (Parent) and recurrent GBM cells generated after parent cells are exposed to lethal dose of radiation. Total RNA-seq of parent and recurrent population revealed significant upregulation of cell-ECM interactions pathway in the recurrent population. These results led us to hypothesize that the physical microenvironment contributes to the aggressiveness of recurrent GBM. To verify this, we cultured parent and recurrent GBM cells on collagen-coated polyacrylamide gels mimicking the stiffness of normal brain (Young's modulus E = 0.5kPa) or tumorigenic brain (E = 10kPa) and tissue culture plastic dishes (E ∼ 1 GPa). We found that compared to parent cells, recurrent cells showed higher proliferation, invasion, migration, and resistance to EGFR inhibitor. Using orthotopic GBM mouse model and resection model, we demonstrate that recurrent cells cultured on 0.5kPa had higher in vivo tumorigenicity and recurrent disease progression than parent cells, whereas these differences were insignificant when parent and recurrent cells were cultured on plastic substrates. Furthermore, recurrent cells on 0.5kPa showed high expression of ECM proteins like Collagen, MMP2 and MMP9. These proteins were also significantly upregulated in recurrent patient biopsies. Additionally, the brain of mice injected with recurrent cells grown on 0.5kPa showed higher Young's moduli suggesting the ability of these cells to make the surrounding ECM stiffer. Total RNA-seq of parent and recurrent cells grown on plastic and 0.5kpa identified PLEKHA7 significantly upregulated specifically in recurrent cells grown on 0.5 kPa substrate. PLEKHA7 was also found to be high in recurrent GBM patient biopsies. Accordingly, PLEKHA7 knockdown reduced invasion and survival of recurrent GBM cells. Together, these data provide an in vitro model system that captures the observed in vivo and clinical behavior of recurrent GBM by mimicking mechanical microenvironment and identifies PLEKHA7 as a novel potential target for recurrent GBM.

The Molecular Roles and Clinical Implications of Non-Coding RNAs in Gastric Cancer

Gastric cancer (GC) is one of the most common malignancies in the world. It is also the fifth most common cancer in China. In recent years, a large number of studies have proved that non-coding RNAs (ncRNAs) can regulate cell proliferation, invasion, metastasis, apoptosis, and angiogenesis. NcRNAs also influence the therapeutic resistance of gastric cancer. NcRNAs mainly consist of miRNAs, lncRNAs and circRNAs. In this paper, we summarized ncRNAs as biomarkers and therapeutic targets for gastric cancer, and also reviewed their role in clinical trials and diagnosis. We sum up different ncRNAs and related moleculars and signaling pathway in gastric cancer, like Bcl-2, PTEN, Wnt signaling. In addition, the potential clinical application of ncRNAs in overcoming chemotherapy and radiotherapy resistance in GC in the future were also focused on.

Zinc finger protein 852 is essential for the proliferation, drug sensitivity, and self-renewal of gastric cancer cells

Exploring cellular and molecular mechanisms responsible for gastric cancer growth, survival, self-renewal, and metastasis helps develop efficacious therapeutic strategies. In this study, the expression and function of Zinc finger protein 852 (ZNF852) in human gastric cancer cell lines were characterized. ZNF852 was up-regulated in gastric cancer cell lines relative to normal gastric epithelial cell line GES-1. When the ZNF852 gene was ablated in gastric cancer cell line MGC-803 using the CRISPR/Cas9-encoding lentivirus, the proliferation of MGC-803 was suppressed. ZNF852 deficiency also resulted in the inhibition of MGC-803 sphere formation, along with decreases in SRY-box 2 (SOX2), Octamer-binding transcription factor 4 (OCT4), and Nanog homeobox (NANOG), suggesting that ZNF852 sustains self-renewal of MGC-803 cells. Furthermore, ZNF852 deficiency increased oxaliplatin-induced MGC-803 cell death, implying the role of ZNF852 in drug sensitivity. Subcutaneous infusion of MGC-803 cells into nude mice illustrated the same effects of ZNF852 on the proliferation and self-renewal of gastric cancer cells. Similar effects of ANF852 were also seen in gastric cancer cell line SNU-1. Interestingly, ZNF852 deficiency caused down-regulation of epidermal growth factor receptor (EGFR) on gastric cancer cells. In summary, this study uncovers the positive regulatory role of ZNF852 in gastric cancer growth and maintenance. ZNF852 could be a potential therapeutic target for inhibiting gastric cancer initiation or progression. This article is protected by copyright. All rights reserved.

FGD5 facilitates tumor growth by regulating EGFR ubiquitination in gastric cancer

FGD5 (faciogenital dysplasia-5), a Rho-family guanine nucleotide exchange factor, has been identified as a key regulator of endothelial cells angiogenesis and apoptosis. However, the expression and role of FGD5 in the pathogenesis of gastric cancer remain unknown. In the present study, we first detected FGD5 expression in tumor tissues of different stages by immunofluorescence and confirmed that FGD5 expression was associated with stages in human gastric cancer. Knockdown FGD5 by shRNA in 7901 and BGC823 human gastric cells lines inhibited tumorigenesis and migration in vivo and in vitro. Mechanistically, co-immunoprecipitation (Co-IP) assay showed that FGD5 interacted with EGFR and decreased EGFR ubiquitination. Additionally, FGD5 sustained the activation of EGFR downstream signaling molecules, including STAT3 and pSTAT3. Furthermore, we showed that FGD5 could induce resistance to chemotherapy 5Fu/CIS, however, a well-known STAT3 inhibitor FLL32 could reverse FGD5-induced chemotherapy resistance in vivo. In conclusion, we are the first to demonstrate that FGD5 expression was associated with tumor stage and proliferation in gastric cancer and targeting FGD5 might be a potential therapeutic target for EGFR-STAT3 resistance gastric cancer.

Epidermal growth factor receptor promotes tumor progression and contributes to gemcitabine resistance in osteosarcoma

Osteosarcoma (OS) is the most common type of primary malignant tumors that originate in the bone. Resistance to chemotherapy confers a poor prognosis on OS patients. Dysregulation of the epidermal growth factor receptor (EGFR) signaling has been reported in sarcomas. However, the functional contribution of EGFR hyperactivation to the tumor biology and chemoresistance remains largely unexplored in OS. In this study, we aimed to investigate the role of EGFR in OS progression and in the response of OS to gemcitabine treatment. The EGFR expression was found to be upregulated in fibroblastic OS cell lines. EGFR knockdown suppressed OS cell proliferation, migration, and invasion in vitro and tumor formation in vivo. Conversely, EGFR overexpression promoted the growth and motility of OS cells. In terms of mechanism, the levels of phospho-Akt and phospho-ERK were decreased upon EGFR knockdown but increased as a result of EGFR overexpression, implying a possible involvement of PI3K/Akt and ERK pathways in mediating the effects of EGFR on OS cells. Moreover, the level of phospho-EGFR was increased in OS cells when exposed to gemcitabine treatment. A more profound proliferative inhibition and a higher rate of apoptosis were obtained in OS cells via inducing cell cycle arrest at G1 phase upon gemcitabine treatment combined with EGFR knockdown, as compared to gemcitabine alone. On the contrary, EGFR overexpression counteracted the growth-inhibiting and pro-apoptotic effects of gemcitabine in OS cells. The present study suggests that EGFR promotes tumor progression and contributes to gemcitabine resistance in OS.

The utility of high-mobility group A2 overexpression for predicting the prognosis of gastric cancer patients and its contribution to poor prognosis via chemoresistance and the propensity for the occurrence of carcinomatosis peritonei

BACKGROUND

The aim of this study was to elucidate the correlation of high-mobility group protein A2 overexpression with gastric cancer prognosis and compare its prognostic power with that of pre-existing markers.

METHODS

Malignant tissues from 396 patients with gastric cancer who underwent gastrectomy from 2008 to 2012 were examined. High-mobility group protein A2 expression was assessed by immunohistochemistry and the sensitivity and specificity for predicting disease progression and overall survival of high-mobility group protein A2 and the prognostic biomarkers p53, Ki-67, human epidermal growth factor receptor 2, cyclooxygenase-2, and epidermal growth factor receptor were compared.

RESULTS

A total of 95 samples (24.1%) showed high-mobility group protein A2 overexpression, which was related to advanced stage, undifferentiated histology, and lymphatic and perineural invasion. Additionally, high-mobility group protein A2 overexpression was an independent prognostic factor in multivariate analysis for disease progression and overall survival. Based on Kaplan-Meier survival analysis disease progression and overall survival, the high-mobility group protein A2-overexpressing patients showed worse survival. The recurrence pattern of peritoneal dissemination was more frequently observed in high-mobility group protein A2-positive group. Moreover, chemoresistance was more frequently observed in the high-mobility group protein A2-positive group. High-mobility group protein A2 exhibited a better ability for predicting disease progression and overall survival than other markers, and the prognostic power was enhanced when high-mobility group protein A2 was used with these markers.

CONCLUSION

High-mobility group protein A2 overexpression is associated with chemoresistance and a propensity for carcinomatosis peritonei after surgery in patients with gastric cancer. The power to predict the prognosis of patients with gastric cancer can be enhanced with the use of preexisting biomarkers and high-mobility group protein A2.

Genes Involved in the PD-L1 Pathway Might Associate with Radiosensitivity of Patients with Gastric Cancer

The PD-1/PD-L1 pathway plays an important role in the treatment of cancers as immune checkpoint. However, the association of genes involved in the PD-L1 pathway and radiosensitivity of gastric cancer has not been fully characterized. This study aims to explore the relationship between the expression levels of genes involved in the PD-L1 pathway and radiosensitivity for gastric cancer patients. A total of 367 patients with clinical survival information and radiotherapy information were obtained in The Cancer Genome Atlas (TCGA). Genes involved in the PD-L1 pathway were categorized into high and low expression level groups according to the median value. The Cox proportional hazards model was used to find the association between gene expression level and radiosensitivity. The results show that high expression levels of CD274, EGFR, RAF1, RPS6KB1, PIK3CA, MTOR, CHUK, NFKB1, TRAF6, FOS, NFATC1, and HIF1A were associated with radiosensitivity of gastric cancer. While low expression level of HRAS was also associated with radiosensitivity in gastric cancer. The rates of a new tumor event and disease progression were lower for radiosensitivity patients than other patients. The relationship between the expression level of CD274 and other genes involved in the PD-L1 pathway is significant. GO (Gene Ontology) analysis shows that the biological process of 13 genes was mainly related to innate immune response activating the cell surface receptor signaling pathway. KEGG analysis demonstrated that 13 genes in gastric cancer are mainly related to the PD-L1 expression and PD-1 checkpoint pathway in cancer. The correlation between the expression level of CD274 and other genes involved in the PD-L1 pathway is significant. The present study offered more evidence for using PD-L1 and genes involved in the PD-L1 pathway as potential biomarkers to predict radiosensitive patients with gastric cancer.

Expression level of EGFR and MET receptors regulates invasiveness of melanoma cells

Epidermal and hepatocyte growth factors can stimulate invasive abilities of melanoma cells, while treatment with combination of their receptors' (EGFR and MET, respectively) inhibitors reduces viability of these cells, as we have previously shown. Proposed therapy has potential; however, used drugs block more than one goal effectively, what raises the question about the real target of analysed inhibitors. For this reason, we analysed direct involvement of these receptors in the invasion of melanoma cells inducing EGFR and MET up‐ and down‐regulations in examined cells. Results were acquired with assays evaluating cell migration and invasion (scratch wound assay, Transwell filter‐based method and single‐cell tracking). We revealed that cells' motile abilities are increased after EGFR overexpression and decreased following EGFR and MET silencing. This outcome correlates with elevated (EGFR up‐regulation) or reduced (EGFR/MET down‐regulation) number of formed invadopodia, visualized with immunofluorescence, and their rate of proteolytic abilities, evaluated by fluorescent gelatin degradation assay, and gelatin zymography, compared to control cells. Above‐mentioned data indicate that both—EGFR and MET signalling is directly connected with melanoma cells invasion, what establishes these receptors as promising targets for anti‐cancer treatment.

A phase I study evaluating combined nimotuzumab and neoadjuvant chemoradiotherapy followed by surgery in locally advanced esophageal cancer

OBJECTIVE

The aim of this study was to evaluate the safety and efficacy of combined nimotuzumab and neoadjuvant chemoradiotherapy followed by surgery in locally advanced esophageal cancer.

METHODS

Patients with clinically resectable, locally advanced esophageal cancer treated with neoadjuvant chemoradiotherapy plus nimotuzumab were eligible for study participation. Radiotherapy was administered in 1.8 Gy once daily for 5 days per week up to a total dose of 41.4 Gy. Weekly nimotuzumab (200 mg/week) was administered following paclitaxel and carboplatin on the same day for 5 weeks. The primary end-point was the pathological complete response (pCR) rate and the secondary end-point was the safety, progression-free survival (PFS) and overall survival (OS).

RESULTS

A total of 64 patients with a median age of 58 years were enrolled in this study. pCR was observed in 51.6% patients. Grade 3 acute toxicities were observed in 6 patients (9.4%), shown as bone marrow suppression. 7 patients experienced grade 1 transient skin rash during nimotuzumab treatment. The median PFS time and OS time were 64.6 and 68.2 months.

CONCLUSIONS

Combined nimotuzumab and neoadjuvant chemoradiotherapy for clinically resectable, locally advanced esophageal cancer showed a significant anticancer effect with tolerable toxicities.

E5 can be expressed in anal cancer and leads to epidermal growth factor receptor-induced invasion in a human papillomavirus 16-transformed anal epithelial cell line

We created the first human papillomavirus (HPV)-16-immortalized anal epithelial cell line, known as AKC2 cells to establish an in vitro model of HPV-16-induced anal carcinogenesis. Consistent with detection of E6, E7 and E5 expression in anal cancer biopsies, AKC2 cells expressed high levels of all three HPV oncogenes. Also, similar to findings in anal cancer biopsies, epidermal growth factor receptor (EGFR) was overexpressed in AKC2 cells. AKC2 cells exhibited a poorly differentiated and invasive phenotype in three-dimensional raft culture and inhibition of EGFR function abrogated AKC2 invasion. Reducing E5 expression using E5-targeted siRNAs in AKC2 cells led to knockdown of E5 expression, but also HPV-16 E2, E6 and E7 expression. AKC2 cells treated with E5-targeted siRNA had reduced levels of total and phosphorylated EGFR, and reduced invasion. Rescue of E6/E7 expression with simultaneous E5 knockdown confirmed that E5 plays a key role in EGFR overexpression and EGFR-induced invasion.

MicroRNA‑509 acts as a tumor suppressor in tongue squamous cell carcinoma by targeting epidermal growth factor receptor

Tongue squamous cell carcinoma (TSCC) is the most frequent type of oral carcinoma, and is characterized by high metastatic and growth capabilities. Previous studies have demonstrated that aberrantly expressed cancer‑associated microRNAs (miRs) may be associated with tumorigenesis and tumor development in various types of cancer, including TSCC. miR‑509 has been identified as a critical regulator in tumorigenesis and tumor development, via its tumor‑suppressing actions in several types of human cancer. In the present study, miR‑509 expression in TSCC tissues and cell lines was determined by reverse transcription‑quantitative polymerase chain reaction. The effects of miR‑509 on TSCC cell proliferation and invasion were evaluated via MTT and invasion assays, respectively. In addition, the direct target of miR‑509 in TSCC was investigated. The present study demonstrated that miR‑509 expression was downregulated in TSCC tissue samples and cell lines, whereas its ectopic expression suppressed TSCC cell proliferation and invasion in vitro. In addition, epidermal growth factor receptor (EGFR) was identified as a direct target gene of miR‑509 in TSCC cells. EGFR downregulation was demonstrated to suppress the proliferation and invasion of TSCC cells, similar to miR‑509 overexpression. Furthermore, EGFR was significantly upregulated in TSCC tissues, and the levels of miR‑509 were revealed to be negatively correlated with EGFR expression in TSCC tissues. Following transfection with miR‑509 mimics, signaling pathways downstream of EGFR appeared to be suppressed, as phosphorylated (p)‑extracellular signal‑regulated kinase and p‑Akt were downregulated in TSCC cells. In conclusion, the results of the present study suggested that miR‑509 may inhibit the proliferation and invasion of TSCC cells via directly targeting EGFR, thus suggesting that the miR‑509/EGFR axis may have potential as a novel therapeutic target for the development of a treatment for patients with TSCC.

Allele-specific silencing of mutant p53 attenuates dominant-negative and gain-of-function activities

Many p53 hotspot mutants not only lose the transcriptional activity, but also show dominant-negative (DN) and oncogenic gain-of-function (GOF) activities. Increasing evidence indicates that knockdown of mutant p53 (mutp53) in cancer cells reduces their aggressive properties, suggesting that survival and proliferation of cancer cells are, at least partially, dependent on the presence of mutp53. However, these p53 siRNAs can downregulate both wild-type p53 (wtp53) and mutp53, which limits their therapeutic applications. In order to specifically deplete mutp53, we have developed allele-specific siRNAs against p53 hotspot mutants and validated their biological effects in the absence or presence of wtp53. First, the mutp53-specific siRNAs selectively reduced protein levels of matched p53 mutants with minimal reduction in wtp53 levels. Second, downregulation of mutp53 in cancer cells expressing a mutp53 alone (p53mut) resulted in significantly decreased cell proliferation and migration. Third, transfection of mutp53-specific siRNAs in cancer cells expressing both wtp53 and mutp53 also reduced cell proliferation and migration with increased transcripts of p53 downstream target genes, which became further profound when cells were treated with an MDM2 inhibitor Nutlin-3a or a chemotherapeutic agent doxorubicin. These results indicate that depletion of mutp53 by its specific siRNA restored endogenous wtp53 activity in cells expressing both wtp53 and mutp53. This is the first study demonstrating biological effects and therapeutic potential of allele-specific silencing of mutp53 by mutp53-specific siRNAs in cancer cells expressing both wtp53 and mutp53, thus providing a novel strategy towards targeted cancer therapies.

13-Methyl-palmatrubine induces apoptosis and cell cycle arrest in A549 cells in vitro and in vivo

Corydalis yanhusuo, a well-known herbaceous plant, is commonly used in the treatment of inflammation, injury and pain. One natural agent isolated from Corydalis yanhusuo, 13-methyl-palmatrubine, was found to have a cytotoxic effect on cancer cells as reported in published studies. In the present study, we synthesized a potential anti-lung tumor agent, 13-methyl-palmatrubine and analyzed its activity. 13-Methyl-palmatrubine exhibited a cytotoxic effect on a panel of cancer cell lines in a time- and concentration-dependent manner. Among all the tested cancer cell lines, lung cancer A549 cells were most sensitive to 13-methyl-palmatrubine treatment. Meanwhile 13-methyl-palmatrubine showed less cytotoxicity in human normal cells. Our investigation revealed that 13-methyl-palmatrubine induced apoptosis and cell cycle arrest in A549 cells in a dose-dependent manner. Furthermore, 13-methyl-palmatrubine treatment caused activation of P38 and JNK pathways and blocked the EGFR pathway. In conclusion, our findings demonstrated that 13-methyl-palmatrubine inhibited the growth of A549 cells mediated by blocking of the EGFR signaling pathway and activation of the MAPK signaling pathway and provides a better understanding of the molecular mechanisms of 13-methyl-palmatrubine.

Rab11-FIP2 promotes the metastasis of gastric cancer cells

Rab11-FIP2 can interact with MYO5B and plays an important role in regulating plasma membrane recycling. Our previous study has shown that MYO5B is epigenetically silenced and associated with c-Met signaling in human gastric cancer. However, little is known of the function of Rab11-FIP2 in gastric cancer. In this study, we investigated Rab11-FIP2 expression by immunohistochemistry in 86 patients with gastric cancer. We found that the expression level of Rab11-FIP2 was significantly increased in gastric cancer tissues and high expression of Rab11-FIP2 was closely correlated with nodal metastasis in gastric cancer patients. Rab11-FIP2 overexpression promoted epithelial-mesenchymal transition (EMT) in a manner associated with gastric cancer metastasis in vitro and in vivo. We also found that hypoxia could enhance the expression of Rab11-FIP2 through HIF-1α. Inactivation of Rab11-FIP2 dramatically decreased hypoxia-induced migration of gastric cancer cells. Suppression of the internalization of EGFR, at least in part, plays an important role in EMT induced by overexpression of Rab11-FIP2 in gastric cancer cells. Finally, we demonstrated that Rab11-FIP2 could regulate actin cytoskeleton dynamics. In conclusion, our findings reveal a novel mechanism underlying the role of Rab11-FIP2 in gastric cancer dissemination, suggesting that Rab11-FIP2 may be a promising candidate target for gastric cancer treatment.

CD24 associates with EGFR and supports EGF/EGFR signaling via RhoA in gastric cancer cells

Background

CD24, a mucin-like membrane glycoprotein, plays a critical role in carcinogenesis, but its role in human gastric cancer and the underlying mechanism remains undefined.

Methods

The contents of CD24 and epidermal growth factor receptor (EGFR) in gastric cancer cells (SGC-7901 and BGC-823) and non-malignant gastric epithelial cells (GES-1) were evaluated by Western blotting assay. Cellular EGFR staining was examined by immunofluorescence assay. Cell migration rate was measured by wound healing assay. The effects of depletion/overexperssion of CD24 on EGFR expression and activation of EGF/EGFR singaling pathways were evaluated by immunofluorescence, qPCR, Western blotting and flow cytometry techniques. RhoA activity was assessed by pulldown assay. CD24 and EGFR expression patterns in human gastric tumor samples were also investigated by immunohistochemistry staining.

Results

CD24 was overexpressed in human gastric cancer cells. Ectopic expression of CD24 in gastric epithelial cells augmented the expression of EGFR, while knockdown of CD24 in gastric cancer cells decreased the level of EGFR and cell migration velocity. To further explore the mechanisms, we investigated the effect of CD24 expression on EGF/EGFR signaling. We noticed that this effect of CD24 on EGFR expression was dependent on promoting EGFR internalization and degradation. Lower ERK and Akt phosphorylations in response to EGF stimulation were observed in CD24-depleted cells. In addition, we noticed that the effect of CD24 on EGFR stability was mediated by RhoA activity in SGC-7901 gastric cancer cells. Analysis of gastric cancer specimens revealed a positive correlation between CD24 and EGFR levels and an association between CD24 expression and worse prognosis.

Conclusion

Thus, these findings suggest for the first time that CD24 regulates EGFR signaling by inhibiting EGFR internalization and degradation in a RhoA-dependent manner in gastric cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0787-y) contains supplementary material, which is available to authorized users.

EGF-reduced Wnt5a transcription induces epithelial-mesenchymal transition via Arf6-ERK signaling in gastric cancer cells

Wnt5a, a ligand for activating the non-canonical Wnt signaling pathway, is commonly associated with Epithelial-to-mesenchymal transition (EMT) in cancer cell metastasis. Here, we show that downregulation of Wnt5a mRNA and protein by EGF is necessary for EGF-induced EMT in gastric cancer SGC-7901 cells. To further explore the mechanisms, we investigated the effect of EGF signaling on Wnt5a expression. EGF increased Arf6 and ERK activity, while blockade of Arf6 activation repressed ERK activity, up-regulated Wnt5a expression and repressed EMT in response to EGF. We also demonstrate that EGF inactivated Wnt5a transcription by direct recruitment of ERK to the Wnt5a promoter. On the other hand, inhibition of ERK phosphorylation resulted in decreased movement of ERK from the cytoplasm to the nucleus, following rescued Wnt5a mRNA and protein expression and favored an epithelial phenotype of SGC-7901 cells. In addition, we notice that kinase-dead, nuclear-localised ERK has inhibitory effect on Wnt5a transcription. Analysis of gastric cancer specimens revealed an inverse correlation between P-ERK and Wnt5a protein levels and an association between Wnt5a expression and better prognosis. These findings indicate that Wnt5a is a potential suppressor of EMT and identify a novel Arf6/ERK signaling pathway for EGF-regulated Wnt5a expression at transcriptional level of gastric cancer cells.

The combinational therapy of trastuzumab and cetuximab inhibits tumor growth in a patient-derived tumor xenograft model of gastric cancer

PURPOSE

Gastric cancer (GC) is one of the leading causes of cancer mortality worldwide. Although therapeutic strategies for GC have improved, the prognosis for advanced GC remains poor. Herein, the present study sought to design a personalized cancer therapy specific to a stage III GC patient.

METHODS

The tumor was surgically removed and was used to establish a patient-derived tumor xenograft (PDTX) model utilizing nude mice. Various molecular-targeted anticancer treatments were tested in the study, including control (no treatment), bevacizumab, cetuximab, bevacizumab + cetuximab, trastuzumab, and trastuzumab + cetuximab.

RESULTS

Trastuzumab + cetuximab treatment exhibited the best antitumor growth effect, followed by trastuzumab, bevacizumab + cetuximab, cetuximab, and bevacizumab. Similarly, trastuzumab + cetuximab was also the most effective treatment at inducing apoptosis and cell cycle arrest in primary cultures of the patient's gastric cancer cells. Among all treatments tested in the study, trastuzumab + cetuximab showed the most profound effect in reducing the protein expression of proliferation and metastatic markers (VEGF, MMP-7, EGFT, Ki-67 and, PCNA) in tumors obtained from PDTX models, which may be the mechanism underlying the profound antitumor growth effect exerted by trastuzumab + cetuximab.

CONCLUSIONS

The data indicate that trastuzumab + cetuximab combinational therapy should be the most effective antitumor growth therapy for the GC patient whom we took the cancer cells from.

Emerging kinase inhibitors of the treatment of gastric cancer

INTRODUCTION

Gastric cancer (GC) is the fifth most common malignancy in the world. In the last years, for the first time in literature, the addition of a targeted therapy to standard chemotherapy has proved to prolong median overall survival. In this scenario, kinase inhibitors (KIs), smaller intracellular agents, could be an interesting and novel type of targeted treatment of metastatic GC both in first and further lines of therapy.

AREAS COVERED

Several KI have been evaluated in the preclinical setting. This review will underline the most relevant targeted pathways involved in GC tumorigenesis and disease progression including EGFR, VEGFR, c-MET, mTOR, fibroblast growth factor receptor, Src and Aurora kinases.

EXPERT OPINION

Despite the good results of TOGA, RAINBOW and REGARD trials about the addition of monoclonal antibodies to standard of care in GC, the addition of KI seems not to achieve comparable interesting results in management of GC. However, an improved patient selection before and during treatment according to molecular characteristics, as well as combination studies evaluating the synergistic effect of combination schedules of different KIs and standard chemotherapy, or KI plus KI or KI plus antibodies-based therapy may reveal interesting results and lead to understand mechanisms of multi-drug resistance.