Malignant melanoma typically metastasizes to lymph nodes (LNs) as a primary or in-transit lesion before secondary metastasis occurs, and LN biopsy is a common procedure to diagnose melanoma progression. Since cancer metastasis is a complex process where various interactions between tumor cells and the stroma play key roles in establishing metastatic lesions, the exact mechanisms underlying melanoma metastasis to LNs remains unknown. It has been known that focal adhesion kinase (FAK) activity promotes the expression of proinflammatory vascular cell adhesion molecule-1 (VCAM-1). As VCAM-1 is a major receptor for α4 integrin and plays a key role in leukocyte recruitment, we reasoned that inhibition of FAK activity may reduce VCAM-1 expression within LNs and thus reduce metastasis of α4 integrin-expressing melanoma to LNs. First, we found that a pharmacological FAK inhibitor, PF-271, blocked tumor necrosis factor-α (TNF-α)-mediated VCAM-1 expression on human dermal lymphatic endothelial cells (HDLECs). In vitro, PF-271 significantly decreased B16F10 melanoma adhesion to and transmigration through HDLECs compared to TNF-α treated cells. Furthermore, in vivo FAK inhibition by oral PF-271 administration reduced VCAM-1 expression in inguinal, cervical, and popliteal LNs compared to vehicle treated mice. Finally, in a footpad metastasis model, B16F10 melanoma cells were injected into the right footpad of C57BL/6 mice, and PF-271 (50 mg/kg, twice daily for 6 days) was orally administrated after 1 week of tumor transplantation. While untreated mice exhibited significant metastatic melanoma lesions in popliteal LNs, PF-271 treated mice showed only marginal melanoma metastasis. These results support the possibility that FAK inhibitors may be a novel preventative option in melanoma metastasis by blocking VCAM-1 expression in LNs.

Renal clear cell carcinoma (ccRCC), is an inflammation-related malignancy with poor therapeutic outcome. Interferon-induced transmembrane protein 2 (IFITM2), an inflammation related gene, is reported to promote tumor progression via inducing cytokine release and lymphatic metastasis. However, IFITM2's role in ccRCC remains unclear. In this study, we aimed to explore the role of IFITM2 in ccRCC. In vitro studies displayed overexpressed IFITM2 level in tumor tissues, while analysis of 538 cases from TCGA unveiled the correlation of upregulated-IFITM2 with shorter survival. Migration and invasion of ccRCC were inhibited following the downregulation of IFITM2. Cocultured with IFITM2-silenced ccRCC cells, human lymphatic endothelial cells were inhibited in proliferation, migration and tube formation, indicating that lymphangiognesis was contributed by IFITM2 expression. Taken together, IFITM2 promotes ccRCC progression by inducing malignant characteristics and lymphatic metastasis. Therefore, IFITM2 represents a promising novel target for therapy and effective prediction of malignancy of ccRCC.

Lymphatic endothelial cells in tumors (T-LECs) are considered to have different characteristics from LECs in non-tumor tissues (N-LECs). However, differences between the two types have not been well analyzed at molecular level. In this report, we performed differential proteome analysis of T-LEC and N-LEC models prepared by cultivation of LECs in tumor conditioned medium. By expression profiling of identified proteins using tissue microarrays, reticulocalbin-1 was found to be expressed in clinical specimen-derived T-LECs and lung cancer cells but not N-LECs. It is suggested that reticulocalbin-1 may be an important molecule in understanding T-LEC function and control of lymphatic metastasis.

Heparanase-1/syndecan-1 axis plays critical roles in tumorigenesis and development. The main mechanism includes heparanase-1 (HPA-1) degrades the heparan sulfate chain of syndecan-1 (SDC-1), and the following shedding of heparan sulfate from tumor cell releases and activates SDC-1 sequestered growth factors. However, the significance of Heparanase-1/syndecan-1 axis and its effects on the microenvironment of lymphatic metastasis in hepatocellular carcinogenesis (HCC) procession have not been reported. Herein, we found that HPA-1 could degrade the heparan sulfate on hepatocarcinoma cell surface. Importantly, HPA-1-induced shedding of heparan sulfate chain from SDC-1 facilitated the release of vascular endothelial growth factor C (VEGF-C) from SDC-1/VEGF-C complex into the medium of hepatocarcinoma cell. Further studies indicated that VEGF-C secretion from hepatocarcinoma cell promoted lymphatic endothelial cell growth through activating extracellular signal-regulated kinase (ERK) signaling. Taken together, this study reveals a novel existence of Heparanase-1/syndecan-1 axis in hepatocarcinoma cell and its roles in the cross-talking with the microenvironment of lymphatic metastasis.

Human peritoneum is composed of mesothelial monolayer and stromal tissue containing microvasculature. Dissemination and infiltration of cancer cells to the peritoneum result in cancer peritoneal metastasis which is an important prognostic factor of intraperitoneal or intrapelvic carcinoma. To elucidate an initial metastatic mechanism of cancer cells, in vitro human peritoneal models are demanded. In this study, we created a three-dimensional artificial human peritoneal tissue (AHPT) harboring the blood or lymphatic vascular network by cell-accumulation technique. Morphological analysis demonstrated that AHPT had mesothelial monolayer with polygonal flat cells with apical microvilli, and stroma-like structure containing fibroblasts surrounded by extracellular matrix and blood or lymphatic vascular network. To assess AHPT as a tool for cancer peritoneal metastasis model, colon and ovarian cancer cells (HT-29 and SKOV3) were seeded onto AHPT. HT-29 cells showed poor metastatic characteristics forming thick clusters in mesothelial layer without invasion into stroma-like structure. On the other hand, SKOV3 cells rapidly invaded intercellular spaces between mesothelial cells and then spread over the stroma-like structure accompanying lymphatic invasion, showing aggressive metastatic characteristics. These results demonstrated that the metastatic dynamics of cancer cells with different characteristics are able to visualized by AHPT, suggesting that this tissue can be a powerful tool for the basic research of cancer peritoneal dissemination and metastasis.

Colorectal cancer mainly metastasizes through the lymphatic pathways and is associated with a high mortality rate. It is one of the leading causes of cancer-related deaths. In this study, the effects of long non-coding RNA (lncRNA) ENSG00000231881 on the metastasis of colorectal cancer cells were evaluated.

Tumor-induced lymphangiogenesis, a major conduit for cancer cell dissemination from the primary tumor site to lymph nodes and beyond, eventually leads to metastasis in cancer patients. Given the recent evidence revealing that the suppression of ELK3 inhibits the metastasis of triple-negative breast cancer cells, we aimed to study the underlying mechanism of impaired metastasis in ELK3-suppressed MDA-MB-231 cells (ELK3 KD) with regard to lymphangiogenesis. We found that the secretome of ELK3 KD cells inhibited tube formation, whereas it promoted the migration and invasion of lymphatic endothelial cells (LECs) in vitro. In vivo analysis revealed that peritumoral lymphatic vessels were not developed around the xenografted tumors of ELK3 KD. We further revealed that the suppression of NF-κB signaling in ELK3 KD was the primary cause of the reduced VEGFC expression. Taken together, we suggest that ELK3 is an upstream regulator of the NF-κB signaling pathway, the inhibition of which leads to the suppression of peritumoral lymphatic vessel development, possibly due to a low VEGFC expression.

Esophageal cancer (EC) is one of the most common malignancies with poor prognosis. Metabolomics has been shown to be a powerful approach to discover the potential biomarkers for cancer diagnosis and prognosis. The goal of this study is to screen potential biomarkers for early diagnosis and prognosis. In this study, 40 tissue samples and the corresponding control samples from the same esophageal squamous cell carcinoma (ESCC) patients were analyzed by liquid chromatography-mass spectrometry (LC-MS)-based metabolomics. 20 potential diagnostic biomarkers were selected. Moreover, 9 metabolites were found to be closely correlated with the pathological feature such as local invasion, lymphatic metastasis and postoperative survival time. Glutamate was correlated with local invasion of tumor, and oleic acid, LysoPC(15:0), uracil, inosine and choline were closely related with the lymphatic metastasis, while glutamine, kynurenine, serine and uracil were related with postoperative survival time. The results indicated that the potential biomarkers discovered by metabolomics could reflect the metabolic characterization of ESCC, and offers a novel approach for early diagnosis, assessment and prognosis of the disease.

We had previously reported that in addition to p53 inactivation, overexpression of the DNA sensor protein-absent in melanoma 2 (AIM2)-contributes to tumorigenesis of oral squamous cell carcinoma (OSCC). Given that AIM2 is highly expressed in the OSCC tumors from patients with metastasis, we investigated whether AIM2 expression contributes to the progression of OSCC metastasis. In in vitro assays using OSCC cell lines, the high migration and invasion capacity of OSCC cells were dependent on the increased expression of AIM2, resulting in enhanced epithelial-mesenchymal transition (EMT), with EMT-related gene expression. Moreover, the in vivo short-term metastasis assay using orthotopic implantation into immunodeficient mice demonstrated that OSCC cells with high levels of AIM2 expression exhibited enhanced tumor growth in the tongue, resulting in decreased survival of the mice. Further, the cells overexpressing AIM2 dominantly invaded into the tumor lymphatic vessels, unlike OSCC cells with low AIM2 expression. Thus, the high expression of AIM2 in OSCC enhances progression of tumor growth.

Circulating lncRNAs have been defined as a novel biomarker for non-small cell lung cancer (NSCLC), MALAT-1 was first identified lncRNA that was related to lung cancer metastasis. However, the relationship between exosomal lncRNAs and the diagnosis and prognosis of NSCLC was poorly understood. The aim of this study is to evaluate the clinical significance of serum exosomal MALAT-1 as a biomarker in the metastasis of NSCLC. In this study, we firstly isolated the exosomes from healthy subjects and NSCLC patients. Then we measured the expression levels of MALAT-1 contained in exosomes, and found that exosomal MALAT-1 was highly expressed in NSCLC patients, more importantly, the levels of exosomal MALAT-1 were positively associated with tumor stage and lymphatic metastasis. In addition, we decreased MALAT-1 expression by short hairpin RNA and conducted a series of assays including MTT, cell cycle, colony formation, wound-healing scratch and Annexin/V PI by flow cytometry in human lung cancer cell lines. These in vitro studies demonstrated that serum exosome-derived long noncoding RNA MALAT-1 promoted the tumor growth and migration, and prevented tumor cells from apoptosis in lung cancer cell lines. Taken together, this study shed a light on utilizing MALAT-1 in exosomes as a non-invasive serum-based tumor biomarker for diagnosis and prognosis of NSCLC.

Abundant evidence has showed that circular RNA (circRNA) plays an important role in cancer. Nonetheless, little is known about the roles and mechanisms of specific circRNAs in different cancer types. Hsa_circ_0008285 (circ_0008285), derived from the coding gene chromodomain y-like protein (CDYL), is upregulated in hepatocellular carcinoma and mantle cell lymphoma. However, we previously found, by analyzing two independent high-throughput sequencing datasets, that it was reduced in colon cancer. In this study, we explored the function and mechanism of circ_0008285 in the progression of colorectal cancer (CRC). First, the downregulated expression of circ_0008285 in CRC tissues and cell lines was confirmed using RT-qPCR analysis. In addition, the expression level of circ_0008285 was inversely correlated with tumor size, lymphatic metastasis, and tumor-node-metastasis (TNM) stage through clinicopathological parameter analysis. Functionally, knockdown of circ_0008285 promoted CRC cell proliferation and migration in vitro. Mechanistically, by using RNA-sequencing, bioinformatics analysis, dual-luciferase reporter assay, and western blotting, we determined that circ_0008285 suppressed the PI3K/AKT pathway via the miR-382-5p/PTEN axis. In conclusion, our data demonstrate a tumor suppressor role for circ_0008285 in CRC and suggest circ_0008285 as a potential target for CRC treatment.

The VEGF family comprises seven members that are designated VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGF-E, placental growth factor (PlGF), and VEGF-F. Of these factors, VEGF-D plays important roles for angiogenesis and lymphangiogenesis, and could promote tumor growth and lymphatic metastasis. In this study, we identified a zebrafish VEGF-D homolog that encodes a 272 amino acid protein including a PDGF (platelet-derived growth factor) domain characteristic to VEGF family. Expression profile demonstrated that the VEGF-D began expressed from 13 somite stage. Microinjecting zVEGF-D mRNA into zebrafish 1-cell stage embryos resulted in severe misguidance of intersegmental vessels (ISV) and abnormal connection between dorsal aorta and caudal vein. Microangiography indicated that these abnormal ISVs were not functional. Our studies therefore identified the first non-mammalian VEGF-D and established its in vivo role for vascular system development during vertebrate embryogenesis and provided an alternative animal model to further reveal functions of VEGF-D.

Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment and have been shown to promote cancer aggressiveness. In our previous study, analysis of expression profiles obtained from paired CAFs and normal fibroblasts from colorectal cancer (CRC) tissue revealed that gene sets related to the Wnt signaling pathway were highly enriched in colorectal CAFs. Furthermore, among the components of the β-catenin-independent Wnt pathway, Wnt5a was highly expressed in CAFs. Since Wnt5a is considered to be a regulator of CRC progression in CAFs, we performed immunohistochemical analysis on Wnt5a in 171 patients who underwent surgery for CRC. Positive staining for Wnt5a was often found in cancer stroma, particularly in fibromatous areas, although the immunoreactivity for Wnt5a was weak in cancer cells. Wnt5a status in CAFs was significantly associated with tumor size, depth of invasion, lymphatic and vascular invasion, lymph node metastasis, TNM stage, and recurrence. Subsequent in vitro analyses using human recombinant Wnt5a protein revealed that cancer cell proliferation and migration were significantly increased by stimulation with Wnt5a. Our findings suggest that Wnt5a-derived CAFs play a crucial role in CRC progression and have potential as a target of anti-cancer therapies.