The somite-secreted factor Maeg promotes zebrafish embryonic angiogenesis

EGFL6 promotes bone metastasis of lung adenocarcinoma by increasing cancer cell malignancy and bone resorption

Lung adenocarcinoma is the most common and aggressive type of lung cancer with the highest incidence of bone metastasis. Epidermal growth factor-like domain multiple 6 (EGFL6) is an exocrine protein, and the expression of EGFL6 is correlated with survival of patient with lung adenocarcinoma. However, the association between EGFL6 expression in lung adenocarcinoma and bone metastasis has not been investigated. In this study, we found that EGFL6 levels in lung adenocarcinoma tissues correlate with bone metastasis and TNM stages in surgical patients. In vitro, overexpression of EGFL6 in lung adenocarcinoma cells promoted their proliferation, migration, and invasion ability compared with control by enhancing EMT process and activating Wnt/β-catenin and PI3K/AKT/mTOR pathways. In the nude mouse model, overexpression of EGFL6 enhanced tumor growth and caused greater bone destruction. Moreover, the exocrine EGFL6 of human lung adenocarcinoma cells increased osteoclast differentiation of bone marrow mononuclear macrophages (BMMs) of mice via the NF-κB and c-Fos/NFATc1 signaling pathways. However, exocrine EGFL6 had no effect on osteoblast differentiation of bone marrow mesenchymal stem cells (BMSCs). In conclusion, high expression of EGFL6 in lung adenocarcinomas is associated with bone metastasis in surgical patients. The underlying mechanism may be the increased metastatic properties of lung adenocarcinoma cells with high EGFL6 level and the enhanced osteoclast differentiation and bone resorption by exocrine EGFL6 from tumors. Therefore, EGFL6 is a potential therapeutic target to reduce the ability of lung adenocarcinomas to grow and metastasize and to preserve bone mass in patients with bone metastases from lung adenocarcinomas.

Progress of EGFL6 in angiogenesis and tumor development

The epidermal growth factor (EGF) superfamily includes the protein 6 with an epidermal growth factor-like protein (EGFL6). EGFL6 has a signal peptide domain with an amino terminus and a MAM domain with a carboxy terminus. There are four whole EGF-like repeat regions and one partial EGF-like repeat region. Three of these regions include calcium-binding structures and an arg-gly-asp (RGD) integrin interaction motif. The epidermal growth factor-like (EGFL) and EGF domains have identical amino acid residues. Cell division, differentiation, mortality, cell adhesion, and migration are all affected by EGFL6. EGFL proteins are involved in a broad range of biological activities, making it important in tumor development and angiogenesis. We highlighted the latest development of EGFL6 research on tumor proliferation, invasion, and migration in this review.

Osteoblast-derived EGFL6 couples angiogenesis to osteogenesis during bone repair

Rationale: Angiogenesis and osteogenesis are highly coupled processes which are indispensable to bone repair. However, the underlying mechanism(s) remain elusive. To bridge the gap in understanding the coupling process is crucial to develop corresponding solutions to abnormal bone healing. Epidermal growth factor-like protein 6 (EGFL6) is an angiogenic factor specifically and distinctively up-regulated during osteoblast differentiation. In contrast with most currently known osteoblast-derived coupling factors, EGFL6 is highlighted with little or low expression in other cells and tissues.

Methods: In this study, primary bone marrow mesenchymal stem cells (MSCs) and osteoblastic cell line (MC3T3-E1) were transduced with lentiviral silencing or overexpression constructs targeting EGFL6. Cells were induced by osteogenic medium, followed by the evaluation of mineralization as well as related gene and protein expression. Global and conditional knockout mice were established to examine the bone phenotype under physiological condition. Furthermore, bone defect models were created to investigate the outcome of bone repair in mice lacking EGFL6 expression.

Results: We show that overexpression of EGFL6 markedly enhances osteogenic capacity in vitro by augmenting bone morphogenic protein (BMP)-Smad and MAPK signaling, whereas downregulation of EGFL6 diminishes osteoblastic mineralization. Interestingly, osteoblast differentiation was not affected by the exogenous addition of EGFL6 protein, thereby indicating that EGFL6 may regulate osteoblastic function in an intracrine manner. Mice with osteoblast-specific and global knockout of EGFL6 surprisingly exhibit a normal bone phenotype under physiological conditions. However, EGFL6-deficiency leads to compromised bone repair in a bone defect model which is characterized by decreased formation of type H vessels as well as osteoblast lineage cells.

Conclusions: Together, these data demonstrate that EGFL6 serves as an essential regulator to couple osteogenesis to angiogenesis during bone repair.

egfl6 expression in the pharyngeal pouch is dispensable for craniofacial development

Epidermal growth factor-like domain multiple 6 (Egfl6) is a basement membrane protein and plays an important role in hair follicle morphogenesis, angiogenesis, notochord development in vertebrates. Although egfl6 expression in the developing head was observed in zebrafish, its role for craniofacial development and the determination of the pharyngeal region expressing egfl6, have not been reported yet. Here, we report the expression patterns and function of egfl6 in craniofacial development in zebrafish. egfl6 was expressed sequentially in the developing pharyngeal pouches that are key epithelial structures governing the development of the vertebrate head. However, loss-of-function mutations in egfl6 did not cause any craniofacial defects, including the pouches as well as the thymus and facial cartilages whose development is contingent upon appropriate pouch formation. egfl6 was unlikely redundant with egfl7 expressed in a distinct pharyngeal region from that of egfl6 in craniofacial development because reduction of egfl7 with a MO in egfl6 mutants did not affect craniofacial development. In addition, we found that egfl6 carried an endogenous start loss mutation in the wild-type Tübingen strain, implying egfl6 would be a non-functional gene. Taken all together, we suggest that egfl6 expression in the pharyngeal pouches is not required for craniofacial development in zebrafish.

EGFL6 promotes colorectal cancer cell growth and mobility and the anti-cancer property of anti-EGFL6 antibody

BACKGROUND

The availability of a reliable tumor target for advanced colorectal cancer (CRC) therapeutic approaches is critical since current treatments are limited. Epidermal growth factor-like domain 6 (EGFL6) has been reported to be associated with cancer development. Here, we focused on the role of EGFL6 in CRC progression and its clinical relevance. In addition, an anti-EGFL6 antibody was generated by phage display technology to investigate its potential therapeutic efficacy in CRC.

RESULTS

EGFL6 expression significantly increased in the colon tissues from CRC patients and mice showing spontaneous tumorigenesis, but not in normal tissue. Under hypoxic condition, EGFL6 expression was enhanced at both protein and transcript levels. Moreover, EGFL6 could promote cancer cell migration invasion, and proliferation of CRC cells via up-regulation of the ERK/ AKT pathway. EGFL6 also regulated cell migration, invasion, proliferation, and self-renewal through EGFR/αvβ3 integrin receptors. Treatment with the anti-EGFL6 antibody EGFL6-E5-IgG showed tumor-inhibition and anti-metastasis abilities in the xenograft and syngeneic mouse models, respectively. Moreover, EGFL6-E5-IgG treatment had no adverse effect on angiogenesis and wound healing CONCLUSIONS: We demonstrated that EGFL6 plays a role in CRC tumorigenesis and tumor progression, indicating that EGFL6 is a potential therapeutic target worth further investigation.

The emerging role of EGFL6 in angiogenesis and tumor progression

Epidermal growth factor-like domain-containing protein 6 (EGFL6) belongs to the epidermal growth factor (EGF) superfamily. EGFL6 is expressed at higher levels in embryos and various malignant tumors than in normal tissues. Recent studies suggest that EGFL6 participates in the development of a variety of tumors. In this review, we summarize findings that support the role for EGFL6 in tumor proliferation, invasion and migration. Furthermore, our review results indicate the mechanism of EGFL6 activity angiogenesis. We also describe work toward the preparation of monoclonal antibodies against EGFL6. Altogether, the work of this review promotes understanding of the role of EGFL6 in tumor development, the mechanism of that action, and the potential of EGFL6 as a therapeutic target for tumor prevention and treatment.

EGFL6 promotes cell proliferation in colorectal cancer via regulation of the WNT/β-catenin pathway

Epidermal growth factor-like protein 6 (EGFL6) serves as an exocrine protein promoting proliferation and migration during carcinogenesis in ovarian cancer. However, its function and mechanisms in colorectal cancer (CRC) have not been completely explored. To investigate the role of EGFL6 in CRC cell growth, in vitro CCK8, colony formation assays, flow cytometric analysis of the cell cycle and apoptosis, and an in vivo tumor xenograft model were utilized. Additionally, Western blotting and luciferase reporter assays were used to investigate the underlying mechanisms of EGFL6 function on the WNT/β-catenin signaling pathway. Immunohistochemical staining showed that EGFL6 is overexpressed in CRCs and this overexpression was highly correlated with advanced T classification, N classification, distant metastasis, and poor survival. Knocking down EGFL6 in CRC cell lines induced the inhibition of cell growth, cell cycle arrest at the G0/G1 phase, and apoptosis. Further, knockdown of EGFL6 blocked WNT/β-catenin signaling as measured by Western blotting and luciferase reporter assay. Results also showed that recombinant EGFL6 (rEGFL6) induced β-catenin in a concentration- and time-dependent manner. Further experiments showed that administration of rEGFL6 to cell cultures with EGFL6 knocked down or treated with the WNT/β-catenin inhibitor ICG-001 increased β-catenin and its downstream protein CyclinD1. The CCK8 assay showed that EGFL6 promoted CRC cell growth partly by the promotion of TCF7L2 expression. These findings suggest that EGFL6 plays a crucial role in the progression of CRC by regulation of the WNT/β-catenin signaling pathway.

Recent insights into vascular development from studies in zebrafish

PURPOSE OF REVIEW

Zebrafish has provided a powerful platform to study vascular biology over the past 25 years, owing to their distinct advantages for imaging and genetic manipulation. In this review, we summarize recent progress in vascular biology with particular emphasis on vascular development in zebrafish.

RECENT FINDINGS

The advent of transcription activator-like effector nuclease and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 genome-editing technologies has dramatically facilitated reverse genetic approaches in zebrafish, as in other models. Here, we highlight recent studies on vascular development in zebrafish which mainly employed forward or reverse genetics combined with high-resolution imaging. These studies have advanced our understanding of diverse areas in vascular biology, including transcriptional regulation of endothelial cell differentiation, endothelial cell signaling during angiogenesis and lymphangiogenesis, vascular bed-specific developmental mechanisms, and perivascular cell recruitment.

SUMMARY

The unique attributes of the zebrafish model have allowed critical cellular and molecular insights into fundamental mechanisms of vascular development. Knowledge acquired through recent zebrafish work further advances our understanding of basic mechanisms underlying vascular morphogenesis, maintenance, and homeostasis. Ultimately, insights provided by the zebrafish model will help to understand the genetic, cellular, and molecular underpinnings of human vascular malformations and diseases.

Elevated EGFL6 modulates cell metastasis and growth via AKT pathway in nasopharyngeal carcinoma

Epidermal growth factor-like domain multiple 6 (EGFL6) is a secreted protein, regulates maintenance and metastasis of cancer cells. Nevertheless, how EGFL6 participates in the progression and tumorigenesis of nasopharyngeal carcinoma (NPC) remains unclear. In our study, EGFL6 was detected highly expressed in 20 NPC tissues compared with normal tissues by IHC assay. Then, the level of EGFL6 in NPC serum and NPC cells was explored through enzyme-linked immunosorbent assay and western blot, the results consistent with IHC. More interestingly, EGFL6 accelerated the migration and growth of NPC in vitro assays. Considering the mechanism of migration, NPC cells were cultured with AKT activator, revealing EGFL6 facilitated the progression of NPC via AKT. Moreover, the same effect of EGFL6 in promoting NPC growth was proved in nude mice. Furthermore, heat-shock zebrafish model was established with EGFL6 overexpression. Then, CNE2 cells were injected into the model and cells mass was observed, showing that EGFL6 enhanced the migration and metastasis of NPC. Currently, as the prognosis of NPC is severely affected by distant metastasis, it might be a new therapeutic target toward EGFL6. Taken together, our results suggested that EGFL6 acts as a potential positive regulator in the migration and proliferation of NPC.

Validation of EGFL6 expression as a prognostic marker in patients with lung adenocarcinoma in Taiwan: a retrospective study

OBJECTIVE

Lung adenocarcinoma is a non-small cell lung cancer, a common cancer in both genders, and has poor clinical outcome. Our aim was to evaluate the role of epidermal growth factor (EGF)-like domain multiple 6 (EGFL6) and its prognostic significance in lung adenocarcinoma.

METHODS

EGFL6 expression was studied by immunohistochemical staining of specimens from 150 patients with lung adenocarcinoma. The correlation between clinicopathological features and EGFL6 expression was quantitatively analysed. We used Kaplan-Meier analysis and Cox proportional hazard models to examine the prognostic value of EGFL6 in terms of overall survival.

RESULTS

No significant correlation was found between EGFL6 expression and clinical parameters. However, patients with high levels of EGFL6 expression showed a tendency towards poor prognosis, with borderline statistical significance. Grouping the patients according to a medium age value revealed a significant association between high EGFL6 expression and poor clinical outcome in young patients. This finding was further confirmed by grouping the patients into three groups according to age. HR in patients with high EGFL6 expression was higher in younger patients than in older patients.

CONCLUSION

High EGFL6 expression may serve as a marker for poor prognosis of lung adenocarcinoma, especially in younger patients.