Overexpression of engulfment and cell motility 1 promotes cell invasion and migration of hepatocellular carcinoma

Overexpression of Dock180 and Elmo1 in Melanoma is Associated with Cell Survival and Migration

BACKGROUND

Melanoma is one of the most aggressive and metastatic skin cancers. Although overexpression of Dock180 and Elmo1 has been identified in various cancers, including glioma, ovarian cancer, and breast cancer, their expression and functions in melanoma remain unknown.

OBJECTIVE

This study aims to confirm the expression of Dock180 and Elmo1, their underlying mechanisms, and roles in melanoma.

METHODS

Both immunohistochemical staining and Western blotting were used to confirm expression of Dock180 and Elmo1 in human melanoma. To identify roles of Dock180 and Elmo1 in cell survival, apoptosis and migration, downregulation of Dock180 or Elmo1 in melanoma cells with small interfering RNA (siRNA) was performed.

RESULTS

We identified overexpression of Dock180 and Elmo1 in human melanoma compared to normal skin ex vivo. Inhibition of Dock180 or Elmo1 following siRNA in melanoma cells reduced cell viability and increased apoptosis as supported by increased proportion of cells with Annexin V-PE (+) staining and sub-G0/G1 peak in cell cycle analysis. Moreover, inhibition of Dock180 or Elmo1 regulated apoptosis-related proteins, showing downregulation of Bcl-2, caspase-3, and PARP and upregulation of Bax, PUMA, cleaved caspase-3, and cleaved PARP. Furthermore, knockdown of Dock180 and Elmo1 in melanoma cells reduced cell migration and changed cellular signaling pathways including ERK and AKT. Vemurafenib decreased cell viability in concentration-dependent manner, while transfection with Dock180- or Elmo1-specific siRNA in melanoma cells significantly reduced cell viability.

CONCLUSION

Our results suggest that both Dock180 and Elmo1 may be associated with cancer progression, and can be potential targets for treatment of melanoma.

Nucleophosmin 1 associating with engulfment and cell motility protein 1 regulates hepatocellular carcinoma cell chemotaxis and metastasis

The chemokine, C-X-C motif chemokine ligand 12 (CXCL12) and its G-protein-coupled receptor (GPCR) and C-X-C chemokine receptor type 4 (CXCR4), are closely associated with promoting hepatocellular carcinoma (HCC) chemotaxis and metastasis. The binding of CXCL12 and CXCR4 depends on the heterotrimeric Gi proteins to regulate actin polymerisation and mobility in HCC. Although the role of GPCR/Gi signalling in carcinogenesis migration has been intensively studied, the detailed mechanism remains largely unknown. In this study, a small interfering RNA technique was used to knock down the Nucleophosmin 1 (NPM1) gene expression. Through the chemotaxis and invasion assays, wound healing, proliferation, filamentous-actin, immunofluorescence, immunohistochemical assays, and co-immunoprecipitation assays, we investigated the specific biological role and underlying mechanisms of the NPM1 in HCC. Additionally, dimethyl fumarate (DMF), a fumaric acid ester, was used to inhibit the HCC cell chemokines and metastasis by regulating ELMO1 and NPM1. Therefore, this study reported that NPM1 gene expression was upregulated in the HCC tissues and cell lines. The NPM1 knockdown significantly inhibited the proliferation, migration, and chemotaxis of the HepG2 cells in vitro. Further mechanistic studies suggested that the NPM1 interacts with ELMO1 and the CXCL12/CXCR4 pathway activates NPM1-dependent regulation of the ELMO1 localisation. Furthermore, the DMF significantly inhibited tumour metastasis induced by the NPM1/ELMO1 signalling pathway, as observed in in vitro cell functional experiments. These data suggested that as a potentially novel therapeutic approach, the simultaneous targeting of NPM1 and ELMO1 could effectively be used to treat HCC.

Engulfment and cell motility protein 1 fosters reprogramming of tumor-associated macrophages in colorectal cancer

Functional reprogramming of tumor-associated macrophages (TAMs) is crucial to their potent tumor-supportive capacity. However, the molecular mechanism behind the reprogramming process remains poorly understood. Here, we identify engulfment and cell motility protein 1 (ELMO1) as a crucial player for TAM reprogramming in colorectal cancer (CRC). The expression of ELMO1 in stromal but not epithelial tumor cells was positively associated with advanced clinical stage and poor disease-free survival in CRC. An increase in ELMO1 expression was specifically found in TAMs, but not in other multiple nonmalignant stromal cells. Gain- and loss-of-function assays indicated ELMO1 reprogrammed macrophages to a TAM-like phenotype through Rac1 activation. In turn, ELMO1-reprogrammed macrophages were shown to not only facilitate the malignant behaviors of CRC cells but exhibited potent phagocytosis of tumor cells. Taken together, our work underscores the importance of ELMO1 in determining functional reprogramming of TAMs and could provide new insights on potential therapeutic strategies against CRC.

Role of ELMO1 in inflammation and cancer-clinical implications

BACKGROUND

Engulfment and cell motility protein 1 (ELMO1) is a key protein for innate immunity since it is required for the clearance of apoptotic cells and pathogenic bacteria as well as for the control of inflammatory responses. ELMO1, through binding with Dock180 and activation of the Rac1 signaling pathway, plays a significant role in cellular shaping and motility. Rac-mediated actin cytoskeletal rearrangement is essential for bacterial phagocytosis, but also plays a crucial role in processes such as cancer cell invasion and metastasis. While the role of ELMO1 in bacterial infection and inflammatory responses is well established, its implication in cancer is not widely explored yet. Molecular changes or epigenetic alterations such as DNA methylation, which ultimately leads to alterations in gene expression and deregulation of cellular signaling, has been reported for ELMO1 in different cancer types.

CONCLUSIONS

In this review, we provide an updated and comprehensive summary of the roles of ELMO1 in infection, inflammatory diseases and cancer. We highlight the possible mechanisms regulated by ELMO1 that are relevant for cancer development and progression and provide insight into the possible use of ELMO1 as a diagnostic biomarker and therapeutic target.

Functional Verification of Novel ELMO1 Variants by Live Imaging in Zebrafish

ELMO1 (Engulfment and Cell Motility1) is a gene involved in regulating cell motility through the ELMO1-DOCK2-RAC complex. Contrary to DOCK2 (Dedicator of Cytokinesis 2) deficiency, which has been reported to be associated with immunodeficiency diseases, variants of ELMO1 have been associated with autoimmune diseases, such as diabetes and rheumatoid arthritis (RA). To explore the function of ELMO1 in immune cells and to verify the functions of novel ELMO1 variants in vivo, we established a zebrafish elmo1 mutant model. Live imaging revealed that, similar to mammals, the motility of neutrophils and T-cells was largely attenuated in zebrafish mutants. Consequently, the response of neutrophils to injury or bacterial infection was significantly reduced in the mutants. Furthermore, the reduced mobility of neutrophils could be rescued by the expression of constitutively activated Rac proteins, suggesting that zebrafish elmo1 mutant functions via a conserved mechanism. With this mutant, three novel human ELMO1 variants were transiently and specifically expressed in zebrafish neutrophils. Two variants, p.E90K (c.268G>A) and p.D194G (c.581A>G), could efficiently recover the motility defect of neutrophils in the elmo1 mutant; however, the p.R354X (c.1060C>T) variant failed to rescue the mutant. Based on those results, we identified that zebrafish elmo1 plays conserved roles in cell motility, similar to higher vertebrates. Using the transient-expression assay, zebrafish elmo1 mutants could serve as an effective model for human variant verification in vivo.

Engulfment and cell motility 1 promotes tumor progression via the modulation of tumor cell survival in gastric cancer

BACKGROUND/AIM

Engulfment and cell motility 1 (ELMO1) protein has been implicated in phagocytosis of apoptotic cells, cell migration, neurite outgrowth, cancer cell invasion and metastasis, and poor prognosis in various cancers. We investigated the role of ELMO1 in mediating the oncogenic behavior of gastric cancer (GC) cells. We also investigated the correlation between expression of ELMO1 in GC tissues and various clinicopathological parameters.

METHODS

We studied the impact of ELMO1 on tumor cell behavior using the pcDNA-myc vector and small interfering RNA in AGS and SNU1750 GC cell lines. We performed western blotting and immunohistochemistry to investigate the expression of ELMO1 in GC cells and tissues.

RESULTS

ELMO1 overexpression inhibited apoptosis via the modulation of PARP, caspase-3 and caspase-7 in GC cells. ELMO1 overexpression led to significant increase in the number of migrating and invading GC cells. The expression of E-cadherin decreased and that of Snail increased in GC cells upon ELMO1 overexpression. Phosphorylation of PI3K/Akt and GSK-3β was increased and that of β-catenin was decreased upon ELMO1 overexpression in GC cells. These results were reversed after ELMO1 knockdown. ELMO1 expression was significantly associated with tumor size, cancer stage, lymph node metastasis and survival. ELMO1-positive tumors had significantly higher mean of Ki-67 labeling index than ELMO1-negative tumors. There was no significant relationship between ELMO1 expression and the mean value of the apoptotic index.

CONCLUSIONS

Our results indicate that ELMO1 promotes tumor progression by modulating tumor cell survival in human GC.

ELMO2 association with Gαi2 regulates pancreatic cancer cell chemotaxis and metastasis

Background

Pancreatic cancer is a highly lethal disease. Nearly half of the patients have distant metastasis and remain asymptomatic. Emerging evidence suggests that the chemokine, CXCL12, has a role in cancer metastasis. The interaction between CXCL12 and CXCR4 activates heterotrimeric G proteins, which regulates actin polymerization and cancer cell migration. However, the molecular mechanisms underlying pancreatic cancer cell migration are still largely obscure. Here, we addressed the role of ELMO2 in chemotaxis and metastasis of pancreatic cancer cells.

Methods

Pancreatic cancer cell lines PANC-1 and AsPC-1 and siRNA-mediated knockdown of ELMO2 were used to determine the effects of ELMO2 on cancer cell chemotaxis, invasion, migration. Co-immunoprecipitation assays were carried out to identify interacting partners of ELMO2.

Results

ELMO2 knockdown inhibited pancreatic cancer cell chemotaxis, migration, invasion, and F-actin polymerization. Co-immunoprecipitation assays revealed that ELMO2 interacted with Gαi2 and that CXCL12 triggered Gα i2-dependent membrane translocation of ELMO2. Thus, ELMO2 is a potential therapeutic target for pancreatic cancer.

Intergrated analysis of ELMO1, serves as a link between tumour mutation burden and epithelial-mesenchymal transition in hepatocellular carcinoma

BACKGROUND

Epithelial-mesenchymal transition (EMT) is critical for cancer cell metastasis. Recently, EMT was reported to be associated with the inflammatory tumour microenvironment and, therefore, might be a predictive biomarker for immune checkpoint blockade agents. However, the underlying mechanism is still unclear.

METHODS

Patient survival data for our HCC cohort, TCGA and GEO datasets were determined by Kaplan-Meier analysis. The functional roles of ELMO1 in HCC were demonstrated by a series of in vitro and in vivo experiments. Gene microarray analysis was used to demonstrate potential mechanisms of ELMO1. Data retrieved from the TCGA datasets were used to determine the relationships of ELMO1, EMT and TMB.

FINDINGS

Here, we report an indispensable role for ELMO1 in linking EMT with tumour mutation burden (TMB), which is a promising biomarker for the immune checkpoint blockade agent response. Upregulated ELMO1 expression is associated with a poor prognosis in hepatocellular carcinoma (HCC), as well as increased cell growth, invasion, migration, angiogenesis and EMT in vitro and in vivo. Mechanistically, we provide evidence that ELMO1 regulates SOX10 expression and induces EMT through PI3K/Akt signalling. Moreover, ELMO1 is negatively associated with TMB, indicating a negative relationship between EMT and TMB.

INTERPRETATION

ELMO1 serves as a link between EMT and TMB, providing a mechanistic basis for the further development of ELMO1 as a therapeutic target against HCC and potentially a promising biomarker of the immune checkpoint blockade agent response. FUND: National Natural Science Foundation of China; Natural Science Foundation of Guangdong Province; Young Teacher Training Program of Sun Yat-sen University; Science and Technology Plan of Guangdong Province; Special Support Program of Guangdong Province, Science and Technology Innovation Youth Talent Support Program; the Pearl River Science and Technology New Talent of Guangzhou City; Medical Scientific Research Foundation of Guangdong Province.

MiR-HCC2 Up-regulates BAMBI and ELMO1 Expression to Facilitate the Proliferation and EMT of Hepatocellular Carcinoma Cells

MicroRNAs (miRNAs) are a class of gene expression regulators that participate in the occurrence and development of hepatocellular carcinoma (HCC), although the underlying mechanism by which they function in HCC has not been fully elucidated. Here, small RNA deep sequencing was used to identify aberrantly expressed miRNAs in HCC tissues, and a novel miRNA named miR-HCC2 was identified. RT-qPCR analysis demonstrated that miR-HCC2 displayed higher expression in HCC tissues than in adjacent non-tumor tissues. We documented that miR-HCC2 facilitated the growth, migration and invasion of HCC cells by accelerating cell cycle progression, incressing the expression of epithelial-to-mesenchymal transition (EMT)-associated marker vimentin but decreasing the expression of E-cadherin. MiR-HCC2 directly targeted the 3′ UTR of BAMBI and ELMO1 and up-regulated their expression. Both BAMBI and ELMO1 had the same patterns of expression with miR-HCC2 in HCC tissues. Additionally, blocking BAMBI or ELMO1 counteracted the phenotypic alterations elicited by miR-HCC2. Collectively, our investigation identified miR-HCC2 as a new positive modulator of HCC aggressiveness that may serve as a potential biomarker for the development of diagnostic and therapeutic approaches for HCC.

Down Regulation of the Expression of ELMO3 by COX2 Inhibitor Suppresses Tumor Growth and Metastasis in Non-Small-Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is one of the most common malignancies. Studies have shown that engulfment and cell motility 3 (ELMO3) is highly expressed in NSCLC and can be used as a novel biomarker, but its underlying mechanism remains to be explored. The aim of this study was to investigate the mechanism by which ELMO3 may be down-regulated by COX-2 inhibitors to inhibit NSCLC. NSCLC tissue and adjacent normal lung tissue from 24 patients were used to detect the mRNA and protein expression of ELMO3, COX-2, and other related proteins by Western blot, RT-PCR, and Immunohistochemical analysis. Lewis Lung carcinoma (LLC) cells were used to investigate the effects and the mechanism of siELMO3 and COX-2 inhibitor. C57BL/6 mice inoculated with LLC cells by subcutaneous (s.c.) injection were used to detect the in vivo effects of cox-2 inhibitor. The expression of ELMO3 and cyclooxygenase-2 (COX-2) in human NSCLC tissues was significantly increased compared with that in the adjacent normal tissues. ELMO3 exhibited a positive correlation with COX-2 expression. Moreover, knockdown of ELMO3 suppressed the epithelial-mesenchymal transition (EMT), adhesion, and metastasis of Lewis lung carcinoma (LLC) cells. Importantly, Parecoxib, a selective inhibitor of COX-2, significantly reduced the expression of ELMO3 and EMT in LLC cells and LLC-bearing mice. Furthermore, it could inhibit the growth, adhesion and metastasis of LLC cells in vitro. Our results demonstrate that down regulation of ELMO3 suppressed growth and metastasis of lung cancer by inhibiting EMT. Parecoxib could reduce ELMO3 expression and suppress growth and metastasis of lung cancer, which might be a useful chemotherapeutic agent for inhibiting metastasis and recurrence of NSCLC.

Exome Sequencing of Fresh-frozen or Formalin-fixed Paraffin-embedded B6C3F1/N Mouse Hepatocellular Carcinomas Arising Either Spontaneously or due to Chronic Chemical Exposure

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide; however, the mutational properties of HCC-associated carcinogens remain largely uncharacterized. We hypothesized that mechanisms underlying chemical-induced HCC can be characterized by evaluating the mutational spectra of these tumors. To test this hypothesis, we performed exome sequencing of B6C3F1/N HCCs that arose either spontaneously in vehicle controls ( n = 3) or due to chronic exposure to gingko biloba extract (GBE; n = 4) or methyleugenol (MEG; n = 3). Most archived tumor samples are available as formalin-fixed paraffin-embedded (FFPE) blocks, rather than fresh-frozen (FF) samples; hence, exome sequencing from paired FF and FFPE samples was compared. FF and FFPE samples showed 63% to 70% mutation concordance. Multiple known (e.g., Ctnnb1T41A, BrafV637E) and novel (e.g., Erbb4C559S, Card10A700V, and Klf11P358L) mutations in cancer-related genes were identified. The overall mutational burden was greater for MEG than for GBE or spontaneous HCC samples. To characterize the mutagenic mechanisms, we analyzed the mutational spectra in the HCCs according to their trinucleotide motifs. The MEG tumors clustered closest to Catalogue of Somatic Mutations in Cancer signatures 4 and 24, which are, respectively, associated with benzo(a)pyrene- and aflatoxin-induced HCCs in humans. These results establish a novel approach for classifying liver carcinogens and understanding the mechanisms of hepatocellular carcinogenesis.

De-repression of the RAC activator ELMO1 in cancer stem cells drives progression of TGFβ-deficient squamous cell carcinoma from transition zones

Squamous cell carcinomas occurring at transition zones are highly malignant tumors with poor prognosis. The identity of the cell population and the signaling pathways involved in the progression of transition zone squamous cell carcinoma are poorly understood, hence representing limited options for targeted therapies. Here, we identify a highly tumorigenic cancer stem cell population in a mouse model of transitional epithelial carcinoma and uncover a novel mechanism by which loss of TGFβ receptor II (Tgfbr2) mediates invasion and metastasis through de-repression of ELMO1, a RAC-activating guanine exchange factor, specifically in cancer stem cells of transition zone tumors. We identify ELMO1 as a novel target of TGFβ signaling and show that restoration of Tgfbr2 results in a complete block of ELMO1 in vivo. Knocking down Elmo1 impairs metastasis of carcinoma cells to the lung, thereby providing insights into the mechanisms of progression of Tgfbr2-deficient invasive transition zone squamous cell carcinoma.

Knockdown of ELMO3 Suppresses Growth, Invasion and Metastasis of Colorectal Cancer

The engulfment and cell motility (ELMOs) family of proteins plays a crucial role in tumor cell migration and invasion. However, the function of ELMO3 is poorly defined. To elucidate its role in the development and progression of colorectal cancer (CRC), we examined the expression of ELMO3 in 45 cases of paired CRC tumor tissues and adjacent normal tissues. Furthermore, we assessed the effect of the knockdown of ELMO3 on cell proliferation, cell cycle, migration, invasion and F-actin polymerization in HCT116 cells. The result shows that the expression of ELMO3 in CRC tissues was significantly increased in comparison to the adjacent normal colorectal tissues. Moreover, this overexpression was associated with tumor size (p = 0.007), tumor differentiation (p = 0.001), depth of invasion (p = 0.009), lymph node metastasis (p = 0.003), distant metastasis (p = 0.013) and tumor, node, metastasis (TNM)-based classification (p = 0.000). In in vitro experiments, the silencing of ELMO3 inhibited cell proliferation, invasion, metastasis, and F-actin polymerization, and induced Gap 1 (G1) phase cell cycle arrest. Our study demonstrates that ELMO3 is involved in the processes of growth, invasion and metastasis of CRC, and could be used a potential molecular diagnostic tool or therapy target of CRC.