The emerging molecular machinery and therapeutic targets of metastasis

Quantification of Invadopodia Formation and Matrix Degradation Activity

Cancer cells possess a remarkable capacity to dissociate from a primary tumor, invade the surrounding tissues and vasculature, and eventually form metastases in distant organs. This complex and multistep process remains one of the major causes of mortality in cancer patients worldwide. Multiple studies have highlighted the role of actin-rich structures called invadopodia ("invasive feet"), which adhere to the matrix, contain and secrete matrix-degrading proteinases, and apply protrusive forces generated by the actin cytoskeleton, which drive the invasive process. Here, we describe a fluorescent microscopy-based protocol for imaging and quantifying both invadopodia formation and matrix degradation.

Targeting tumor-intrinsic PD-L1 suppresses the progression and aggressiveness of head and neck cancer by inhibiting GSK3β-dependent Snail degradation

PURPOSE

PD-L1 is an immune checkpoint protein that allows cells to evade T-cell-mediated immune responses. Herein, we uncover a tumor-intrinsic mechanism of PD-L1 that is responsible for the progression and aggressiveness of HNC and reveal that the extracts of a brown alga can target the tumor-intrinsic signaling pathway of PD-L1.

METHODS

The biological functions of PD-L1 in the proliferation and aggressiveness of HNC cells in vitro were examined by metabolic activity, clonogenic, tumorigenicity, wound healing, migration, and invasion assays. The clinical importance of PD-L1 in the prognosis of patients with HNC was analyzed by immunohistochemistry. The relationship between PD-L1 and EMT was confirmed via western blotting, qPCR, and immunocytochemistry.

RESULTS

Through our in silico approach, we found that PD-L1 was upregulated in HNC and was correlated with an unfavorable clinical outcome in patients with HNC. PD-L1 was crucial for promoting tumor growth, both in vitro and in vivo. High expression of PD-L1 was closely correlated with LN metastasis in OSCC. PD-L1 facilitated the cytoskeletal reorganization and aggressiveness of HNC cells. Moreover, PD-L1 enhanced the EMT of HNC cells by regulating the Snail/vimentin axis. Consistently, MEIO suppressed the PD-L1/Snail/vimentin axis, thereby inhibiting the aggressiveness of HNC cells. Inhibition of PD-L1 induced by PD-L1 silencing or MEIO treatment caused Snail degradation through a GSK3β-dependent mechanism. The tumor-intrinsic function of PD-L1 could be attributed to the regulation of the GSK3β/Snail/vimentin axis.

CONCLUSION

The discovery of MEIO targeting the tumor-intrinsic function of PD-L1 may prove particularly valuable for the development of novel and effective anticancer drug candidates for HNCs overexpressing PD-L1.

The Significance of MicroRNAs in the Molecular Pathology of Brain Metastases

Brain metastases are the most frequent intracranial tumors in adults and the cause of death in almost one-fourth of cases. The incidence of brain metastases is steadily increasing. The main reason for this increase could be the introduction of new and more efficient therapeutic strategies that lead to longer survival but, at the same time, cause a higher risk of brain parenchyma infiltration. In addition, the advances in imaging methodology, which provide earlier identification of brain metastases, may also be a reason for the higher recorded number of patients with these tumors. Metastasis is a complex biological process that is still largely unexplored, influenced by many factors and involving many molecules. A deeper understanding of the process will allow the discovery of more effective diagnostic and therapeutic approaches that could improve the quality and length of patient survival. Recent studies have shown that microRNAs (miRNAs) are essential molecules that are involved in specific steps of the metastatic cascade. MiRNAs are endogenously expressed small non-coding RNAs that act as post-transcriptional regulators of gene expression and thus regulate most cellular processes. The dysregulation of these molecules has been implicated in many cancers, including brain metastases. Therefore, miRNAs represent promising diagnostic molecules and therapeutic targets in brain metastases. This review summarizes the current knowledge on the importance of miRNAs in brain metastasis, focusing on their involvement in the metastatic cascade and their potential clinical implications.

Linoleic Acid-Substituted Polyethyleneimine to Silence Heat Shock Protein 90B1 (HSP90B1) to Inhibit Migration of Breast Cancer Cells

INTRODUCTION

Breast cancer continues to be one of the leading causes of death in women and the lack of treatment options for distant metastasis warrants the need to identify and develop more effective approaches. The aim of this study was to identify and validate targets that are associated with the survival and migration of the breast cancer cells in vitro through RNA interference (RNAi) approach.

METHODS

Linoleic acid modified polyethylenimine (PEI) polymer was used to screen a siRNA library against numerous cell adhesion and cytoskeleton genes in MDA-MB-231 triple negative breast cell line and the functional outcome of silencing was determined by growth and migration inhibition with further target validation studies.

RESULTS

Heat shock protein 90B1 (HSP90B1) was identified as a crucial gene which is known to be involved in various breast cancer machineries, including uncontrolled proliferation and brain metastasis. The success of this approach was also due to the use of hyaluronic acid (HA) additive in lipopolymer complexes that showed a profound impact in reducing the cell viability (~50%), migration (~40%), and mRNA transcript levels (~80%) with a physiologically relevant siRNA concentration of 60 nM. The use of dicer-substrate siRNA proved to be beneficial in target silencing and a combinational treatment of integrin-β1 (ITGB1) and HSP90B1 was effective in reducing the migration of the MDA-MB-231 and MDA-MB-436 breast cancer cells.

CONCLUSION

This study demonstrated the potential to identify and silence targets using lipid modified PEI/siRNA system and highlight the importance of HSP90B1 in the growth and migration of breast cancer cells.

Cancer Stem Cell Traits in Tumor Spheres Derived from Primary Laryngeal Carcinoma Cell Lines

Objective

Cancer stem cells (CSCs) belong to a subpopulation of undifferentiated cells present within tumors that have the potential to regenerate, differentiate, maintenance of pluripotency, drug resistance, and tumorigenicity when transplanted into an innate host. These can influence the growth and behavior of these tumors and are used to investigate the initiation, progression, and treatment strategies of laryngeal cancer. Research on CSC science and targeted therapies were hinge on their isolation and/or enrichment procedures. The object of the study is to isolate cancer stem cells from primary laryngeal carcinoma (CSCPLC) by tumor spheres enrichment. We checked the properties of self-renewal, stemness, clonogenicity, and chemotherapeutic resistance.

Materials and Methods

We performed tumor sphere formation assay (primary, secondary, and tertiary) chemotherapy resistance by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay were performed to evaluate the CSC cells. Immunofluorescence for stem cell markers (CD133+, CD44+) and gene expression of stem cell markers for CD133+, CD44+, OCT4, SOX2, and NANOG was done using the real-time polymerase chain reaction technique.

Results

We were able to isolated CSC subpopulations from PLC cell lines by the tumor sphere method. These cells exhibited good primary, secondary, and tertiary tumor sphere formation efficiency and also disclosed a resistant index of more than 2. Immunofluorescence for stem cell markers (CD133+ and CD44+) confirms the presence of CSC. There was significantly higher mRNA expression of stem cell markers in CSC enriched subpopulations compared to the parental cell lines.

Conclusion

We conclude that tumor spheres enrichment is an efficient, economical, and reliable approach for the isolation and characterization of CSC from PLC cell lines. These cells demonstrated the properties of self-renewal, stemness, clonogenicity, and chemotherapeutic resistance.

L-Plastin Promotes Gastric Cancer Growth and Metastasis in a Helicobacter pylori cagA-ERK-SP1-Dependent Manner

Actin cytoskeleton dynamic rearrangement is required for tumor cell metastasis and is a key characteristic of Helicobacter pylori (H. pylori)-infected host cells. Actin cytoskeleton modulation is coordinated by multiple actin-binding proteins (ABP). Through Kyoto encyclopedia of gene and genomes database, GEPIA website, and real-time PCR data, we found that H. pylori infection significantly induced L-plastin, a key ABP, in gastric cancer cells. We further explored the regulation and function of L-plastin in H. pylori-associated gastric cancer and found that, mechanistically, H. pylori infection induced gastric cancer cells to express L-plastin via cagA-activated ERK signaling pathway to mediate SP1 binding to L-plastin promoter. Moreover, this increased L-plastin promoted gastric cancer cell proliferation and migration in vitro and facilitated the growth and metastasis of gastric cancer in vivo. Finally, we detected the expression pattern of L-plastin in gastric cancer tissues, and found that L-plastin was increased in gastric cancer tissues and that this increase of L-plastin positively correlated with cagA + H. pylori infection status. Overall, our results elucidate a novel mechanism of L-plastin expression induced by H. pylori, and a new function of L-plastin-facilitated growth and metastasis of gastric cancer, and thereby implicating L-plastin as a potential therapeutic target against gastric cancer. IMPLICATIONS: Our results elucidate a novel mechanism of L-plastin expression induced by H. pylori in gastric cancer, and a new function of L-plastin-facilitated gastric cancer growth and metastasis, implicating L-plastin as a potential therapeutic target against gastric cancer.

Withaferin A mitigates metastatic traits in human oral squamous cell carcinoma caused by aberrant claudin-1 expression

Abnormal expression of claudin-1 (CLDN1) has important roles in carcinogenesis and metastasis in various cancers. The role of CLDN1 in human oral squamous cell carcinoma (OSCC) remains unknown. Here, we report the functional role of CLDN1 in metastasis of human OSCC, as a potential target regulated by withaferin A. From gene expression profiling with microarray technology, we found that the majority of notable differentially expressed genes were classified into migration/invasion category. Withaferin A impaired the motility of human OSCC cells in vitro and suppressed metastatic nodule formation in an in vivo metastasis model, both associated with reduced CLDN1. CLDN1 overexpression enhanced metastatic nodule formation in vivo, resulting in severe metastatic lesions in lung tissue. Moreover, CLDN1 expression was positively correlated to lymphatic metastasis in OSCC patients. The impaired motility of human OSCC cells upon withaferin A treatment was restored by CLDN1 overexpression. Furthermore, upregulation of let-7a induced by withaferin A was inversely correlated to CLDN1 expression. Overall, these give us an insight into the function of CLDN1 for prognosis and treatment of human OSCC, substantiating further investigation into the use of withaferin A as good anti-metastatic drug candidate.

lncRNA SNHG4 promotes cell proliferation, migration, invasion and the epithelial-mesenchymal transition process via sponging miR-204-5p in gastric cancer

Long non-coding (lnc)RNAs and microRNAs (miRNAs/miRs) have physiological and pathological functions in various diseases, including gastric cancer (GC). The current study explored the association between lncRNA small nucleolar RNA host gene 4 (SNHG4) and miR-148a-3p, and their functions in GC cells. SNHG4 expression and overall survival data were analyzed using bioinformatics, and the interaction of SNHG4 and miR-148a-3p was predicted using starBase and confirmed via a dual-luciferase reporter assay. Cell viability, colony formation ability and apoptosis rate were detected using Cell Counting Kit-8, colony formation and flow cytometry assays, respectively. Cell migration and invasion were determined via wound-healing and Transwell assays. mRNA and protein expression levels were determined via reverse transcription-quantitative PCR and western blotting. The results demonstrated that in GC tissues and cell lines, SNHG4 was highly expressed, while miR-204-5p expression was decreased, and that the expression levels of SNHG4 and miR-204-5p were negatively correlated. The downregulated expression of SNHG4 decreased the effects of miR-204-5p inhibitor on promoting cell proliferation, migration, invasion and epithelial-mesenchymal transition, but enhanced the inhibitory effect of miR-204-5p on GC cell apoptosis. The findings of the current study revealed the potential mechanism of the SNHG4-miR-204-5p pathway in GC, which may be conducive to the development of novel drugs against GC growth.

CD36 upregulates DEK transcription and promotes cell migration and invasion via GSK-3β/β-catenin-mediated epithelial-to-mesenchymal transition in gastric cancer

Evidence indicates that the lipid scavenger receptor CD36 has pro-metastatic functions in several cancers. Although CD36 expression correlates with an unfavorable prognosis in gastric cancer (GC), its specific contribution to disease onset, progression, and/or metastasis remains unclear. Using bioinformatics analyses, we ascertained that CD36 expression was increased in metastatic GC specimens in The Cancer Genome Atlas and Gene Expression Omnibus databases and correlated with poor prognosis. In addition, higher CD36 expression was associated with lymph node metastasis (p < 0.05) and poor prognosis (p = 0.030) in 79 Chinese GC patients. Basal CD36 expression levels correlated positively with migration, invasion, and expression of epithelial-to-mesenchymal transition (EMT) markers in GC cell lines, a relationship confirmed by knockdown and overexpression experiments. Importantly, analysis of gene expression changes in CD36-knockdown GC cells led us to identify the chromatin-associated protein DEK as a c-Myc target that mediates activation of the GSK-3β/β-catenin signaling pathway to trigger EMT. These findings further our understanding of the mechanisms governing metastatic dissemination of GC cells and suggest the therapeutic potential of strategies targeting CD36.

Long non-coding RNA FENDRR inhibits migration and invasion of cutaneous malignant melanoma cells

The present study aimed to investigate the effects of lncRNA FENDRR on the migration and invasion of malignant melanoma (MM) cells. The expression levels of FENDRR in MM tissues and MM cell lines were detected using qRT-PCR, followed by construction of FENDRR-knocked down and overexpressed stable cells. Then the effects of FENDRR on cell proliferation, migration and invasion were detected using MTT assay and Transwell assay. The protein expression levels of matrix metallopeptidase 2 (MMP2), MMP9, and related factors in JNK/c-Jun pathway were detected using Western blot. FENDRR was down-regulated in MM tissues and cell lines. Besides, its expression levels in different MM cells were diverse. Knockdown of FENDRR facilitated MM cells proliferation, migration and invasion in A375 cells, while overexpressing FENDRR had reverse results. In addition, MMPs and JNK/c-Jun pathway involved in the FENDRR-mediated regulation of MM cell proliferation, migration and invasion. Our results demonstrated that FENDRR mediated the metastasis phenotype of MM cells by inhibiting the expressions of MMP2 and MMP9 and antagonizing the JNK/c-Jun pathway.

Bone metastases in thyroid cancer

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Osseous metastases (OMs) occur in only 4% of all thyroid cancer patients but are associated with greatly increased morbidity and mortality.

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OMs are about twice as frequent in follicular, hurthle cell, and medullary thyroid cancers as compared to papillary thyroid cancers.

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OMs are often lytic, triggered via activation of osteoclasts by tumor cells in a “vicious cycle”.

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OMs are often initially asymptomatic, but associated with eventual skeletal related events in >75%.

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Early identification of OMs, preemptive treatment with antiresorptive agents, and aggressive treatment of focal lesions before crisis are key.

Whereas preemptive screening for the presence of lymph node and lung metastases is standard-of-care in thyroid cancer patients, bone metastases are less well studied and are often neglected in thyroid cancer patient surveillance. Bone metastases in thyroid cancer are, however, independently associated with poor/worse prognosis with a median overall survival from detection of only 4 years despite an otherwise excellent prognosis for the vast majority of thyroid cancer patients. In this review we summarize the state of current knowledge as pertinent to bony metastatic disease in thyroid cancer, including clinical implications, impacts on patient function and quality of life, pathogenesis, and therapeutic opportunities, proposing approaches to patient care accordingly. In particular, bone metastasis pathogenesis appears to reflect cooperatively between cancer and the bone microenvironment creating a “vicious cycle” of bone destruction rather than due exclusively to tumor invasion into bone. Additionally, bone metastases are more frequent in follicular and medullary thyroid cancers, requiring closer bone surveillance in patients with these histologies. Emerging data also suggest that treatments such as multikinase inhibitors (MKIs) can be less effective in controlling bone, as opposed to other (e.g. lung), metastases in thyroid cancers, making special attention to bone critical even in the setting of active MKI therapy. Although locoregional therapies including surgery, radiotherapy and ablation play important roles in palliation, antiresorptive agents including bisphosphonates and denosumab appear individually to delay and/or lessen skeletal morbidity and complications, with dosing frequency of every 3 months appearing optimal; their early application should therefore be strongly considered.

CNN3 acts as a potential oncogene in cervical cancer by affecting RPLP1 mRNA expression

The prognosis of advanced stage cervical cancer is poorer due to cancer invasion and metastasis. Exploring new factors and signalling pathways associated with invasiveness and metastasis would help to identify new therapeutic targets for advanced cervical cancer. We searched the cancer microarray database, Oncomine, and found elevated calponin 3 (CNN3) mRNA expression in cervical cancer tissues. QRT-PCR verified the increased CNN3 expression in cervical cancer compared to para-cancer tissues. Proliferation, migration and invasion assays showed that overexpressed CNN3 promoted the viability and motility of cervical cancer cells, the opposite was observed in CNN3-knockdown cells. In addition, xenografted tumours, established from SiHa cells with CNN3 knockdown, displayed decreased growth and metastasis in vivo. Furthermore, RNA-sequencing showed that ribosomal protein lateral stalk subunit P1 (RPLP1) was a potential downstream gene. Gene function experiments revealed that RPLP1 had the same biological effects as CNN3 did. Rescue experiments demonstrated that the phenotypes inhibited by CNN3 silencing were partly or completely reversed by RPLP1 overexpression. In conclusion, we verified that CNN3 acts as an oncogene to promote the viability and motility of cervical cancer cells in vitro and accelerate the growth and metastasis of xenografted tumours in vivo, by affecting RPLP1 expression.

USP37 is a SNAI1 deubiquitinase

SNAI1, an epithelial-mesenchymal transition (EMT)-inducing transcription factor, promotes tumor metastasis and resistance to apoptosis and chemotherapy. SNAI1 protein levels are tightly regulated by proteolytic ubiquitination. Here, we identified USP37 as a SNAI1 deubiquitinase that removes the polyubiquitination chain from SNAI1 and prevents its proteasomal degradation. USP37 directly binds, deubiquitinates, and stabilizes SNAI1. Overexpression of wild-type USP37, but not its catalytically inactive mutant C350S, promotes cancer cell migration. Importantly, depletion of USP37 downregulates endogenous SNAI1 protein and suppresses cell migration, which can be reversed by re-expression of SNAI1. Taken together, our findings suggest that USP37 is a SNAI1 deubiquitinase and a potential therapeutic target to inhibit tumor metastasis.

Towards dual inhibitors of the MET kinase and WNT signaling pathway; design, synthesis and biological evaluation

Both the kinase MET and the WNT signaling pathway are attractive targets in cancer therapy, and synergistic effects have previously been observed in animal models upon simultaneous inhibition. A strategy towards a designed multiple ligand of MET and WNT signaling is pursued based on the two hetero biaryl systems present in both the MET inhibitor tepotinib and WNT signaling inhibitor TC-E 5001. Initial screening was conducted to find the most suitable ring systems for further optimization, whereas a second screen explored modifications towards pyridazinones and triazolo pyridazines. Up to 54% reduction of WNT signaling activity at 10 μM concentration was achieved, however, only low affinities towards MET were observed. Overall, the thiophene substituted pyridazinone 40 was the best dual MET and WNT signaling inhibitor, with a 17% and 19% reduction of activity, respectively. Although further optimizations are needed to achieve more potent dual inhibitors, the strategy presented herein can be valuable towards the development of a dual inhibitor of MET and WNT signaling.

Disruption of Core 1-mediated O-glycosylation oppositely regulates CD44 expression in human colon cancer cells and tumor-derived exosomes

Aberrant O-glycosylation truncates O-glycans and is known to be closely associated with colorectal cancer (CRC), a major gastrointestinal tumor. CD44 is one of the highly post-transcriptionally modified O-glycoproteins participating in a series of physiological and pathobiological processes. In this research, we aimed to investigate whether CD44 expression in cells and exosomes can be influenced by disruption of Core 1-mediated O-glycosylation. Exosomes derived from LS174T and LSC human colon cancer cell lines were isolated from cell culture supernatant and pulled down using tetraspanin-specific antibody CD63 immunoaffinity magnetic beads. Identifications have been performed via transmission electron microscopy (TEM) and flow cytometry. CD63 immunoaffinity-purified exosomes are examined for CD44 expression by flow cytometric analyses. The percentages of CD44 in exosomes derived from abnormally O-glycosylated cells are significantly higher compared with those derived from normal ones, however, which is surprisingly contrary to the cellular expression levels of CD44. The secretion of truncated glycoproteins to the extracellular environment via microvesicles may be most likely its underlying mechanism. CD44 in exosomes might be a potential biomarker of aberrant O-glycosylation. This is the first study indicating that aberrant O-glycosylation can affect expression or delivery of O-glycoproteins via exosomes, which provides us some new sights in therapeutic strategies for human colon cancer.

Targeting metastatic breast cancer with peptide epitopes derived from autocatalytic loop of Prss14/ST14 membrane serine protease and with monoclonal antibodies

Background

In order to develop a new immunotherapeutic agent targeting metastatic breast cancers, we chose to utilize autocatalytic feature of the membrane serine protease Prss14/ST14, a specific prognosis marker for ER negative breast cancer as a target molecule.

Methods

The study was conducted using three mouse breast cancer models, 4 T1 and E0771 mouse breast cancer cells into their syngeneic hosts, and an MMTV-PyMT transgenic mouse strain was used. Prss14/ST14 knockdown cells were used to test function in tumor growth and metastasis, peptides derived from the autocatalytic loop for activation were tested as preventive metastasis vaccine, and monoclonal and humanized antibodies to the same epitope were tested as new therapeutic candidates. ELISA, immunoprecipitation, Immunofluorescent staining, and flow cytometry were used to examine antigen binding. The functions of antibodies were tested in vitro for cell migration and in vivo for tumor growth and metastasis.

Results

Prss14/ST14 is critically involved in the metastasis of breast cancer and poor survival rather than primary tumor growth in two mouse models. The epitopes derived from the specific autocatalytic loop region of Prss14/ST14, based on structural modeling acted as efficient preventive metastasis vaccines in mice. A new specific monoclonal antibody mAb3F3 generated against the engineered loop structure could reduce cell migration, eliminate metastasis in PyMT mice, and can detect the Prss14/ST14 protein expressed in various human cancer cells. Humanized antibody huAb3F3 maintained the specificity and reduced the migration of human breast cancer cells in vitro.

Conclusion

Our study demonstrates that Prss14/ST14 is an important target for modulating metastasis. Our newly developed hybridoma mAbs and humanized antibody can be further developed as new promising candidates for the use in diagnosis and in immunotherapy of human metastatic breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1373-y) contains supplementary material, which is available to authorized users.

Preparation and Evaluation of Liposomes Co-Loaded with Doxorubicin, Phospholipase D Inhibitor 5-Fluoro-2-Indolyl Deschlorohalopemide (FIPI) and D-Alpha Tocopheryl Acid Succinate (α-TOS) for Anti-Metastasis

Tumor metastasis has become a key obstacle to cancer treatment, which causes high mortality. Nowadays, it involves multiple complex pathways, and conventional treatments are not effective due to fewer targets. The aims of the present study were to construct a novel liposome delivery system co-loading a specific PLD inhibitor 5-fluoro-2-indolyldes-chlorohalopemide (FIPI) in combination with antitumor drug doxorubicin (DOX) and functional excipient D-alpha tocopheryl acid succinate (α-TOS) for anti-metastasis. In this study, the liposomes containing three components (DFT-Lip) with different physicochemical properties were successfully prepared by film dispersion method combined with pH-gradient method. Physicochemical parameters such as particles size, potential, encapsulation efficiency, stability, and release profiles were investigated. In vitro and in vivo anti-metastasis effectiveness against highly metastatic breast cancer MDA-MB-231 cell line was evaluated. The liposomes showed uniform particle size (approximately 119 nm), high drug encapsulation efficiency (> 90%), slow release characteristics and stability. In vitro anti-tumor cell metastasis study demonstrated DFT-Lip could greatly inhibit motility, migration and invasion of MDA-MB-231 cells compared to other liposomes, predicting a synergistic anti-tumor metastasis effect between FIPI with α-TOS in liposomes. In vivo anti-metastasis study showed that DFT-Lip prevented the initiation and the progression of metastasis of high metastatic breast cancer. These results suggested that the liposomes containing DOX, FIPI, and α-TOS might be a promising strategy for metastatic tumor therapy in clinics.

MicroRNAs and metastasis: small RNAs play big roles

MicroRNAs (miRNAs) are small non-coding RNAs regulating post-transcriptional gene expression. They play important roles in many biological processes under physiological or pathological conditions, including development, metabolism, tumorigenesis, metastasis, and immune response. Over the past 15 years, significant insights have been gained into the roles of miRNAs in cancer. Depending on the cancer type, miRNAs can act as oncogenes, tumor suppressors, or metastasis regulators. In this review, we focus on the role of miRNAs as components of molecular networks regulating metastasis. These miRNAs, termed metastamiRs, promote or inhibit metastasis through various mechanisms, including regulation of migration, invasion, colonization, cancer stem cell properties, epithelial-mesenchymal transition, and microenvironment. Some of these metastamiRs represent attractive therapeutic targets for cancer treatment.

Regulation of radiosensitivity by 4-methylumbelliferone via the suppression of interleukin-1 in fibrosarcoma cells

Tumor recurrence and distant metastasis following radiotherapy, which can lead to poor prognosis, are caused by residual cancer cells that acquire radioresistance. Chemotherapy or a combination of targeted inhibitors can potentially enhance radiation sensitivity and prevent metastasis. It was previously reported that co-administration of the hyaluronan synthesis inhibitor 4-methylumbelliferone (4-MU) enhanced the lethality of X-ray irradiation in HT1080 human fibrosarcoma cells and decreased their invasiveness to a greater extent than either treatment alone. To clarify the molecular basis of these effects, the present study conducted mRNA expression profiling by cDNA microarray to identify the signaling pathways that are altered under this combination treatment. The activation state of the signaling pathways was classified by z-scores in the Ingenuity Pathway Analysis. The results revealed that the pro-inflammatory cytokines interleukin (IL)-6 and IL-8 were activated by 2 Gy X-ray irradiation, an effect that was abolished by co-administration of 4-MU. Similar trends were observed for the upstream signaling component IL-1. These results indicate that the radiosensitivity of fibrosarcoma cells is improved by suppressing inflammation through the administration of 4-MU.

Novel oncogene COPS3 interacts with Beclin1 and Raf-1 to regulate metastasis of osteosarcoma through autophagy

Background

Expression of COP9 signalosome subunit 3 (COPS3), an oncogene overexpressed in osteosarcoma, has been demonstrated to be significantly correlated with tumor metastasis. However, the underlying mechanism by which COPS3 promotes metastasis of osteosarcoma and its role in autophagy remain unknown.

Methods

The expression of COPS3 was detected in primary osteosarcoma tissues and matching lung metastasis tissues by immunohistochemistry (IHC). The effect of COPS3 on the metastasis of osteosarcoma cells was investigated by transwell, wound healing assays and animal studies. Indicated proteins was analyzed by western blotting when COPS3 was knockdown or overexpressed. The COPS3 Interacting protein was determined by immunoprecipitation assay. The relationship between COPS3 and autophagy was detected by western blotting and immunofluorescence.

Results

We found that knockdown of COPS3 significantly reduced the lung metastasis of osteosarcoma cells in a mouse model, coinciding with downregulation of mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinase (ERK) signaling. The silencing of COPS3 also inhibited the epithelial–mesenchymal transition (EMT) through the 90 kDa ribosomal S6 kinases (RSK), a family of signal transduction proteins downstream of MEK/ERK. Reciprocal immunoprecipitation assays revealed that COPS3 directly interacts with Raf-1, an upstream regulator of MEK/ERK. Surprisingly, Beclin1, an important autophagic protein, appeared in the COPS3-immunoprecipitates, along with the autophagic markers LC3-I and LC3-II. Loss of COPS3 completely inhibited H₂O₂-induced autophagic flux and reduced Beclin1 expression. Additionally, autophagy inhibitor or silencing of Beclin1 both decreased cell metastasis.

Conclusions

Taken together, these data reveal a novel function of COPS3 in the regulation of autophagy and highlight the relationship between autophagy and metastasis in osteosarcoma cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0791-6) contains supplementary material, which is available to authorized users.

Molecular alterations of cancer cell and tumour microenvironment in metastatic gastric cancer

The term metastasis is widely used to describe the endpoint of the process by which tumour cells spread from the primary location to an anatomically distant site. Achieving successful dissemination is dependent not only on the molecular alterations of the cancer cells themselves, but also on the microenvironment through which they encounter. Here, we reviewed the molecular alterations of metastatic gastric cancer (GC) as it reflects a large proportion of GC patients currently seen in clinic. We hope that further exploration and understanding of the multistep metastatic cascade will yield novel therapeutic targets that will lead to better patient outcomes.

A review of microfluidic approaches for investigating cancer extravasation during metastasis

Metastases, or migration of cancers, are common and severe cancer complications. Although the 5-year survival rates of primary tumors have greatly improved, those of metastasis remain below 30%, highlighting the importance of investigating specific mechanisms and therapeutic approaches for metastasis. Microfluidic devices have emerged as a powerful platform for drug target identification and drug response screening and allow incorporation of complex interactions in the metastatic microenvironment as well as manipulation of individual factors. In this work, we review microfluidic devices that have been developed to study cancer cell migration and extravasation in response to mechanical (section ‘Microfluidic investigation of mechanical factors in cancer cell migration’), biochemical (section ‘Microfluidic investigation of biochemical signals in cancer cell invasion’), and cellular (section ‘Microfluidic metastasis-on-a-chip models for investigation of cancer extravasation’) signals. We highlight the device characteristics, discuss the discoveries enabled by these devices, and offer perspectives on future directions for microfluidic investigations of cancer metastasis, with the ultimate aim of identifying the essential factors for a ‘metastasis-on-a-chip’ platform to pursue more efficacious treatment approaches for cancer metastasis.

CD44/CD44v6 a Reliable Companion in Cancer-Initiating Cell Maintenance and Tumor Progression

Metastasis is the leading cause of cancer death, tumor progression proceeding through emigration from the primary tumor, gaining access to the circulation, leaving the circulation, settling in distant organs and growing in the foreign environment. The capacity of a tumor to metastasize relies on a small subpopulation of cells in the primary tumor, so called cancer-initiating cells (CIC). CIC are characterized by sets of markers, mostly membrane anchored adhesion molecules, CD44v6 being the most frequently recovered marker. Knockdown and knockout models accompanied by loss of tumor progression despite unaltered primary tumor growth unraveled that these markers are indispensable for CIC. The unexpected contribution of marker molecules to CIC-related activities prompted research on underlying molecular mechanisms. This review outlines the contribution of CD44, particularly CD44v6 to CIC activities. A first focus is given to the impact of CD44/CD44v6 to inherent CIC features, including the crosstalk with the niche, apoptosis-resistance, and epithelial mesenchymal transition. Following the steps of the metastatic cascade, we report on supporting activities of CD44/CD44v6 in migration and invasion. These CD44/CD44v6 activities rely on the association with membrane-integrated and cytosolic signaling molecules and proteases and transcriptional regulation. They are not restricted to, but most pronounced in CIC and are tightly regulated by feedback loops. Finally, we discuss on the engagement of CD44/CD44v6 in exosome biogenesis, loading and delivery. exosomes being the main acteurs in the long-distance crosstalk of CIC with the host. In brief, by supporting the communication with the niche and promoting apoptosis resistance CD44/CD44v6 plays an important role in CIC maintenance. The multifaceted interplay between CD44/CD44v6, signal transducing molecules and proteases facilitates the metastasizing tumor cell journey through the body. By its engagement in exosome biogenesis CD44/CD44v6 contributes to disseminated tumor cell settlement and growth in distant organs. Thus, CD44/CD44v6 likely is the most central CIC biomarker.

Translational Significance for Tumor Metastasis of Tumor-Associated Macrophages and Epithelial-Mesenchymal Transition

The tumor microenvironment determines development and progression of many cancers. Epithelial–mesenchymal transition (EMT) is fundamental to tumor progression and metastasis not only by increasing invasiveness but also by increasing resistance to cell death, senescence, and various cancer therapies; determining inflammation and immune surveillance; and conferring stem cell properties. It does this by enabling polarized epithelial cells to transform into cells with a mesenchymal, and therefore motile, phenotype. Tumor-associated macrophages (TAMs) are key cells of the tumor microenvironment that orchestrate the connection between inflammation and cancer. Activation of EMT often requires crosstalk between cancer cells and components of the local tumor microenvironment, including TAMs. In this review, clinical and experimental evidence is presented for control of TAMs in promoting cancer cell invasion and migration and their interaction with the EMT process in the metastatic cascade. The translational significance of these findings is that the signaling pathways that interconnect TAMs and EMT-modified cancer cells may represent promising therapeutic targets for the treatment of tumor metastasis.

TGF-β1-induced CK17 enhances cancer stem cell-like properties rather than EMT in promoting cervical cancer metastasis via the ERK1/2-MZF1 signaling pathway

Tumor metastasis remains a major obstacle for improving overall cancer survival in cervical cancer (CC), which may be due to the existence of tumor microenvironment-related cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT). The mechanism underlying these processes needs to be further elucidated. Here, we report that TGF-β1, one of the key microenvironmental stimuli, can enhance CSC characteristics, facilitate the EMT, and induce CK17. Silencing CK17 expression attenuated CSC-like properties without affecting the EMT markers induced by TGF-β1, whereas forced overexpression of CK17 promoted lymphatic metastasis in vivo even without EMT inducement. Inhibitors of ERK1/2 signaling drastically decreased the induction of CK17 mediated by TGF-β1. By combined computational and experimental approaches, we identified and validated that MZF1 was a key transcription factor binding to the promoter of CK17. Taken together, these results demonstrate that CK17 induced by the TGF-β1-ERK1/2-MZF1 signaling pathway facilitates metastasis by promoting the acquisition of CSC properties rather than by inducing the EMT process in CC, suggesting that this CK17-related signaling pathway might be a suitable target for the development of therapy for CC metastasis.

Systematic network-based discovery of a Fam20C inhibitor (FL-1607) with apoptosis modulation in triple-negative breast cancer

Family with sequence similarity 20, member C (Fam20C) is a physiological Golgi casein kinase that phosphorylates multiple secreted proteins. Recently, it has been reported that Fam20C can be identified as a novel kinase target for therapeutic development. Thus, inhibition of Fam20C will be a potential therapeutic strategy to prevent tumor cell progression and metastasis. In our study, based upon the systems-biology network, molecular modeling and molecular dynamics (MD) simulations, we discovered a novel Fam20C inhibitor (FL-1607) with potent anti-proliferative effects on triple-negative breast cancer (TNBC) cells. Subsequently, we found that this Fam20C inhibitor could induce apoptosis and inhibit cell migration in MDA-MB-468 cells. Together, these findings would provide a new clue to the exploration of more novel Fam20C inhibitors for future TNBC therapy.

Pterostilbene prevents AKT-ERK axis-mediated polymerization of surface fibronectin on suspended lung cancer cells independently of apoptosis and suppresses metastasis

Background

Polymeric fibronectin (polyFN) assembled on suspended breast cancer cells is required for metastasis. Conceivably, drugs that target such polyFN may fight against cancer metastasis. While stilbene analogs trigger pro-apoptotic effect on attached cancer cells, whether they prevent polyFN assembly and metastasis of suspended cancer cells via an apoptosis-independent manner remains unexplored.

Methods

We depleted suspended Lewis lung carcinoma (LLC) cells of polyFN by silencing the endogenous FN expression or pterostilbene (PS) to examine whether metastasis of lung cancer cells could thus be suppressed. We investigated whether PS regulates AKT-ERK signaling axis to suppress polyFN assembly in suspended LLC cells independently of apoptosis. We tested the therapeutic effects of orally administered PS against cancer metastasis.

Results

Both FN-silencing and PS among the three stilbenoids indeed significantly reduced polyFN assembly and lung metastasis of suspended LLC cells in an apoptosis-independent manner. Mechanistically, PS-induced AKT phosphorylation (pAKT) and suppressed ERK phosphorylation (pERK) in suspended LLC cells, whereas pretreatment with a PI3K inhibitor, LY294002, effectively reduced pAKT, rescued pERK, and consequently reversed the PS-suppressed polyFN assembly on LLC cells; these pretreatment effects were then overturned by the ERK inhibitor U0126. Indeed, PS-suppressed lung metastasis was counteracted by LY294002, which was further overruled with U0126. Finally, we found that PS, when orally administered in experimental metastasis assays, both significantly prevented lung colonization and metastasis of LLC cells and reduced the already established tumor growth in the mouse lungs.

Conclusions

PS suppressed AKT/ERK-regulated polyFN assembly on suspended LLC cells and pulmonary metastasis. PS possesses potency in both preventing and treating lung metastasis of lung cancer cells in apoptosis-independent and apoptosis-dependent manners, respectively.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-017-0441-z) contains supplementary material, which is available to authorized users.

Naturally occurring compounds acting as potent anti-metastatic agents and their suppressing effects on Hedgehog and WNT/β-catenin signalling pathways

Despite numerous remarkable achievements in the field of anti-cancer therapy, tumour relapse and metastasis still remain major obstacles in improvement of overall cancer survival, which may be at least partially owing to epithelial-mesenchymal transition (EMT). Multiple signalling pathways have been identified in EMT; however, it appears that the role of the Hedgehog and WNT/β-catenin pathways are more prominent than others. These are well-known preserved intracellular regulatory pathways of different cellular functions including proliferation, survival, adhesion and differentiation. Over the last few decades, several naturally occurring compounds have been identified to significantly obstruct several intermediates in Hedgehog and WNT/β-catenin signalling, eventually resulting in suppression of signal transduction. This article highlights the current state of knowledge associated with Hedgehog and WNT/β-catenin, their involvement in metastasis through EMT processes and introduction of the most potent naturally occurring agents with capability of suppressing them, eventually overcoming tumour relapse, invasion and metastasis.

CXCR4 is involved in CD133-induced EMT in non-small cell lung cancer

Metastasis is the major cause of death in patients with non-small cell lung cancer (NSCLC), and epithelial-mesenchymal transition (EMT) has been observed to be one of the key regulators of metastasis in certain cancers as it confers an invasive phenotype. CD133 is a widely used cancer stem cell (CSC) marker, and CD133-positive cancer cells are thought to be tumor-initiating cells with CSC characteristics, while CXCR4, a stromal-derived-factor-1 specific chemokine receptor, is highly expressed in NSCLC tissues and participates in cancer progression by regulating cell anti-apoptosis. We previously demonstrated that CXCR4 promotes NSCLC chemoresistance by upregulating CYP1B1, however, the relationship of CD133, CXCR4 and EMT processes in NSCLC metastasis are unclear. In this study, we detected a CD133 and CXCR4 high expression in tissue specimens from 64 NSCLC patients by immunohistochemistry, of which CD133 and CXCR4 were found to be positively associated with metastatic NSCLC patients. CD133 was found to promote NSCLC tumorigenesis and mediated the expression of CXCR4. Furthermore, CD133/CXCR4 co-expression was found to be an independent prognostic factor as shown by univariate and multivariate Cox regression analysis, and was observed to regulate the expression of EMT-related molecules and transcriptional factors in NSCLC. In addition, our results showed that E-cadherin and Vimentin were simultaneously downregulated and upregulated, in CD133+CXCR4+ A549 cells, respectively. While E-cadherin was upregulated and Vimentin was downregulated in metastatic NSCLC patients. Vimentin expression was also observed to have a positive correlation with CD133/CXCR4 co-expression in NSCLC patients and survival analysis results suggested that Vimentin high expression might be significantly associated with poor survival rates of the patients. Thus, these results suggest that the CD133/CXCR4/EMT axis may be a prognostic marker and may provide novel targets for combinational therapies in the treatment of NSCLC.

Sialylated β1, 6 branched N-glycans modulate the adhesion, invasion and metastasis of hepatocarcinoma cells

The mouse hepatocarcinoma cell lines Hca-F and Hca-P have been derived from hepatocarcinoma in mice and metastasize only to the lymph node. Hca-F cells displayed greater lymphatic metastasis ability than Hca-P cells. When the two cell lines were compared for cell surface sialylated β1,6 branched N-glycans by flow cytometry using L-PHA and SNA, Hca-F cells were found to express significantly higher levels. To explore the effect of increased sialylated β1,6 branched N-glycans on hepatocarcinoma progression, we inhibit their expression in Hca-F cells by using swainsonine treatment and RNA interference. We found that swainsonine treatment or GnT-V-shRNA transfection significantly inhibited the formation of β1,6 branched N-glycans, and partially inhibited the expression of α2,6 sialic acids. Knockdown of sialylated β1,6 branched N-glycans significantly attenuated the invasive and metastatic capability both in vitro and in vivo. Blockade of α2,6 sialic acid expression on Hca-F cell surface by the treatment with neuraminidase caused reduction in cellular adherence to lymph node. In addition, knockdown of sialylated β1,6 branched N-glycans could decrease the expression of Notch1, NICD1, NICD2 and HES1 in Hca-F cells. Collectively, these findings suggest that increased sialylated β1,6 branched N-glycans may contribute to hepatocarcinoma progression by altering the adhesive, invasive and metastatic ability to lymph node via Notch signaling pathway.

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

Epigenetic Therapeutics: A New Weapon in the War Against Cancer

The past 15 years have seen an explosion of discoveries related to the cellular regulation of phenotypes through epigenetic mechanisms. This regulation provides a software that packages DNA, without changing the primary base sequence, to establish heritable patterns of gene expression. In cancer, many aspects of the epigenome, controlled by DNA methylation, chromatin, and nucleosome positioning, are altered as one means by which tumor cells maintain abnormal states of self-renewal at the expense of normal maturation. Epigenetic and genetic abnormalities thus collaborate in cancer initiation and progression, as exemplified by frequent mutations in genes encoding proteins that control the epigenome. There is growing emphasis on using epigenetic therapies to reprogram neoplastic cells toward a normal state. Many agents targeting epigenetic regulation are under development and entering clinical trials. This review highlights the promise that epigenetic therapy, often in combination with other therapies, will become a potent tool for cancer management over the next decade.

MicroRNA and Metastasis

Noncoding RNAs are important regulatory molecules of cellular processes. MicroRNAs (miRNAs) are small noncoding RNAs that bind to complementary sequences in the 3' untranslated region of target mRNAs, leading to degradation of the target mRNAs and/or inhibition of their translation. Some miRNAs are essential for normal animal development; however, many other miRNAs are dispensable for development but play a critical role in pathological conditions, including tumorigenesis and metastasis. miRNA genes often reside at fragile chromosome sites and are deregulated in cancer. Some miRNAs function as oncogenes or tumor suppressors, collectively termed "oncomirs." Specific metastasis-regulating miRNAs, collectively termed "metastamirs," govern molecular processes and pathways in malignant progression in either a tumor cell-autonomous or a cell-nonautonomous manner. Recently, exosome-transferred miRNAs have emerged as mediators of the tumor-stroma cross talk. In this chapter, we focus on the functions, mechanisms of action, and therapeutic potential of miRNAs, particularly oncomirs and metastamirs.

LncRNA GAS5 is a critical regulator of metastasis phenotype of melanoma cells and inhibits tumor growth in vivo

The present study intended to demonstrate the effects of long noncoding RNA growth arrest-specific transcript 5 (GAS5) on the migration and invasion of melanoma cells. We first detected the expression of GAS5 among four kinds of melanoma cell lines, followed by constructing GAS5-knocked down and overexpressed stable cells. Next, we evaluated the effects of GAS5 on cell migration and invasion using wound healing and gelatin zymography assays. Finally, melanoma cells with different GAS5 expression were injected into nude mice, and the tumor volumes were recorded and tumor tissues were analyzed after sacrificing the mice. This study systematically examined the function of GAS5 in mediating melanoma metastasis and revealed that GAS5 plays an anticancer role in melanoma via regulating gelatinase A and B, both in vitro and in vivo.

Medulloblastoma stem cells: Promising targets in medulloblastoma therapy

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Despite great improvements in the therapeutic regimen, relapse and leptomeningeal dissemination still pose great challenges to the long‐term survival of MB patients. Developing more effective strategies has become extremely urgent. In recent years, a number of malignancies, including MB, have been found to contain a subpopulation of cancer cells known as cancer stem cells (CSCs), or tumor initiating/propagating cells. The CSCs are thought to be largely responsible for tumor initiation, maintenance, dissemination, and relapse; therefore, their pivotal roles have revealed them to be promising targets in MB therapy. Our growing understanding of the major medulloblastoma molecular subgroups and the derivation of some of these groups from specific stem or progenitor cells adds additional layers to the CSC knowledge base. Herein we review the current knowledge of MB stem cells, highlight the molecular mechanisms relating to MB relapse and leptomeningeal dissemination, and incorporate these with the need to develop more effective and accurate therapies for MB patients.

Targeting dormant micrometastases: rationale, evidence to date and clinical implications

In spite of decades of research, cancer survival has increased only modestly. This is because most research is based on models of primary tumors. Slow recognition has begun that disseminated, dormant cancer cells (micrometastatic cells) that are generally resistant to chemotherapy are the culprits in recurrence, and until these are targeted effectively we can expect only slow progress in increasing overall survival from cancer. This paper reviews efforts to understand the mechanisms by which cancer cells can become dormant, and thereby identify potential targets and drugs either on the market or in clinical trials that purport to prevent metastasis. This review targets the most recent literature because several excellent reviews have covered the literature from more than two years ago. The paper also describes recent work in the authors' laboratories to develop a screening-based approach that does not require understanding of mechanisms of action or the molecular target. Success of this approach shows that targeting micrometastatic cells is definitely feasible.

Identification of critical genes and gene interaction networks that mediate osteosarcoma metastasis to the lungs

Osteosarcoma (OS) is the most commonly diagnosed bone tumor in young adults under the age of 20. Metastasis is considered an important factor underlying cancer-associated morbidity and mortality, and, as a result, the survival rate of patients with metastatic OS is low. In spite of this, the mechanisms underlying metastasis in OS are currently not well understood. The present study compared gene expression levels between five non-metastatic and four metastatic OS tumor samples, using an Affymetrix microarray. A total of 282 genes were differentially expressed in the metastatic samples, as compared with the non-metastatic samples. Of these differentially expressed genes (DEGs), 212 were upregulated and 70 were downregulated. The following DEGs were associated with metastasis: Homeobox only protein; lysosomal-associated membrane protein-3; chemokine (C-C motif) ligand-18; carcinoembryonic antigen-related cell adhesion molecule-6; keratin-19; prostaglandin-endoperoxide synthase-2; clusterin; and nucleoside diphosphate kinase-1. Subsequently, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analyses were conducted, which identified 529 biological processes (P<0.01) and 10 KEGG pathways (P<0.05) that were significantly over-represented in the metastatic samples, as compared with the non-metastatic samples. Interaction networks for the DEGs were constructed using the corresponding GO terms and KEGG pathways, and these identified numerous genes that may contribute to OS metastasis. Among the enriched biological processes, four DEGs were consistently over-represented: Jun proto-oncogene, caveolin-1, nuclear factor-κB-inhibitor-α and integrin alpha-4; thus suggesting that they may have key roles in OS metastasis, and may be considered potential therapeutic targets in the treatment of patients with OS.