Interaction of Munc18c and syntaxin4 facilitates invadopodium formation and extracellular matrix invasion of tumor cells

Invadopodia in cancer metastasis: dynamics, regulation, and targeted therapies

Pseudopodia and invadopodia are dynamic, actin-rich membrane structures extending from the cell surface. While pseudopodia are found in various cell types, invadopodia are exclusive to tumor cells and play a key role in cancer progression. These specialized structures enable tumor cells to degrade the extracellular matrix, breach tissue barriers, and invade surrounding tissues and blood vessels, thus facilitating metastasis. Extensive research has elucidated the distinct structure of invadopodia, the signaling pathways driving their formation, and their interaction with the tumor microenvironment. Integrin- and Src kinase-mediated signaling pathways regulate invadopodia dynamics. This review explores the mechanisms underlying invadopodia stabilization and highlights recent insights into their regulation by the tumor microenvironment. Particular emphasis is placed on the role of cell surface signaling in modulating invadopodia activity and the intracellular targeting of matrix metalloproteinases (MMPs) in enhancing invasive potential. A deeper understanding of invadopodia-driven cancer cell migration and metastasis provides valuable implications for therapeutic development. These findings support the potential for receptor-mediated and molecularly targeted therapies to inhibit tumor metastasis, improve clinical outcomes, and enhance the efficacy of existing cancer treatments.

SNARE proteins: Core engines of membrane fusion in cancer

Vesicles are loaded with a variety of cargoes, including membrane proteins, secreted proteins, signaling molecules, and various enzymes, etc. Not surprisingly, vesicle transport is essential for proper cellular life activities including growth, division, movement and cellular communication. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate membrane fusion of vesicles with their target compartments that is fundamental for cargo delivery. Recent studies have shown that multiple SNARE family members are aberrantly expressed in human cancers and actively contribute to malignant proliferation, invasion, metastasis, immune evasion and treatment resistance. Here, the localization and function of SNARE proteins in eukaryotic cells are firstly mapped. Then we summarize the expression and regulation of SNAREs in cancer, and describe their contribution to cancer progression and mechanisms, and finally we propose engineering botulinum toxin as a strategy to target SNAREs for cancer treatment.

Endocytic activation and exosomal secretion of matriptase stimulate the second wave of EGF signaling to promote skin and breast cancer invasion

The dysfunction of matriptase, a membrane-anchored protease, is highly related to the progression of skin and breast cancers. Epidermal growth factor (EGF)-induced matriptase activation and cancer invasion are known but with obscure mechanisms. Here, we demonstrate a vesicular-trafficking-mediated interplay between matriptase and EGF signaling in cancer promotion. We found that EGF induces matriptase to undergo endocytosis together with the EGF receptor, followed by acid-induced activation in endosomes. Activated matriptase is then secreted extracellularly on exosomes to catalyze hepatocyte growth factor precursor (pro-HGF) cleavage, resulting in autocrine HGF/c-Met signaling. Matriptase-induced HGF/c-Met signaling represents the second signal wave of EGF, which promotes cancer cell scattering, migration, and invasion. These findings demonstrate a role of vesicular trafficking in efficient activation and secretion of membrane matriptase and a reciprocal regulation of matriptase and EGF signaling in cancer promotion, providing insights into the physiological functions of vesicular trafficking and the molecular pathological mechanisms of skin and breast cancers.

STX4 as a potential biomarker for predicting prognosis and guiding clinical treatment decisions in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) represents a frequent subtype of kidney cancer, with the prognosis remaining poor for individuals with metastatic disease. Given its resistance to both radiation and chemotherapy, targeted therapies and immunotherapies have emerged as critical for effective ccRCC treatment. Within this context, the SNARE protein STX4, which is associated with malignant cancer cell migration, provides a promising focus. The underlying mechanism, however, requires further illumination. Furthermore, the influence of STX4 on the ccRCC tumor microenvironment remains to be determined. In our research, we utilized multiple databases and immunohistochemical staining to confirm differential STX4 expression and its prognostic implications. We evaluated the potential tumor-promoting function of STX4 in ccRCC cell lines through molecular studies. Additionally, we conducted functional enrichment analysis to delve deeper into the underlying mechanisms and performed immune infiltration and drug sensitivity analyses to assess the potential of STX4 as a prognostic biomarker and therapeutic target. Our study reveals that STX4 contributes to cancer progression by enhancing AKT expression and stimulating the activation of VEGF signaling pathways. Additionally, STX4 further fosters CD8+ T-cell infiltration and diminishes the percentage of CAFs and M2-TAMs. Our findings suggest that patients presenting higher STX4 levels may exhibit enhanced responsiveness to immunotherapy and higher sensitivity to the medications axitinib and everolimus. Finally, we propose STX4 expression assessment as a novel approach to predict patient response to respective immunotherapies and targeted treatments, hence potentially improving patient outcomes.

Small extracellular vesicles promote invadopodia activity in glioblastoma cells in a therapy-dependent manner

PURPOSE

The therapeutic efficacy of radiotherapy/temozolomide treatment for glioblastoma (GBM) is limited by the augmented invasiveness mediated by invadopodia activity of surviving GBM cells. As yet, however the underlying mechanisms remain poorly understood. Due to their ability to transport oncogenic material between cells, small extracellular vesicles (sEVs) have emerged as key mediators of tumour progression. We hypothesize that the sustained growth and invasion of cancer cells depends on bidirectional sEV-mediated cell-cell communication.

METHODS

Invadopodia assays and zymography gels were used to examine the invadopodia activity capacity of GBM cells. Differential ultracentrifugation was utilized to isolate sEVs from conditioned medium and proteomic analyses were conducted on both GBM cell lines and their sEVs to determine the cargo present within the sEVs. In addition, the impact of radiotherapy and temozolomide treatment of GBM cells was studied.

RESULTS

We found that GBM cells form active invadopodia and secrete sEVs containing the matrix metalloproteinase MMP-2. Subsequent proteomic studies revealed the presence of an invadopodia-related protein sEV cargo and that sEVs from highly invadopodia active GBM cells (LN229) increase invadopodia activity in sEV recipient GBM cells. We also found that GBM cells displayed increases in invadopodia activity and sEV secretion post radiation/temozolomide treatment. Together, these data reveal a relationship between invadopodia and sEV composition/secretion/uptake in promoting the invasiveness of GBM cells.

CONCLUSIONS

Our data indicate that sEVs secreted by GBM cells can facilitate tumour invasion by promoting invadopodia activity in recipient cells, which may be enhanced by treatment with radio-chemotherapy. The transfer of pro-invasive cargos may yield important insights into the functional capacity of sEVs in invadopodia.

Syntaxin 7 contributes to breast cancer cell invasion by promoting invadopodia formation

Invasion in various cancer cells requires coordinated delivery of signaling proteins, adhesion proteins, actin-remodeling proteins and proteases to matrix-degrading structures called invadopodia. Vesicular trafficking involving SNAREs plays a crucial role in the delivery of cargo to the target membrane. Screening of 13 SNAREs from the endocytic and recycling route using a gene silencing approach coupled with functional assays identified syntaxin 7 (STX7) as an important player in MDA-MB-231 cell invasion. Total internal reflection fluorescence microscopy (TIRF-M) studies revealed that STX7 resides near invadopodia and co-traffics with MT1-MMP (also known as MMP14), indicating a possible role for this SNARE in protease trafficking. STX7 depletion reduced the number of invadopodia and their associated degradative activity. Immunoprecipitation studies revealed that STX7 forms distinct SNARE complexes with VAMP2, VAMP3, VAMP7, STX4 and SNAP23. Depletion of VAMP2, VAMP3 or STX4 abrogated invadopodia formation, phenocopying what was seen upon lack of STX7. Whereas depletion of STX4 reduced MT1-MMP level at the cell surfaces, STX7 silencing significantly reduced the invadopodia-associated MT1-MMP pool and increased the non-invadosomal pool. This study highlights STX7 as a major contributor towards the invadopodia formation during cancer cell invasion. This article has an associated First Person interview with the first author of the paper.

Syntaxin4-Munc18c Interaction Promotes Breast Tumor Invasion and Metastasis by Regulating MT1-MMP Trafficking

Invasion of neighboring extracellular matrix (ECM) by malignant tumor cells is a hallmark of metastatic progression. This invasion can be mediated by subcellular structures known as invadopodia, the function of which depends upon soluble N-ethylmaleimide-sensitive factor-activating protein receptor (SNARE)-mediated vesicular transport of cellular cargo. Recently, it has been shown the SNARE Syntaxin4 (Stx4) mediates trafficking of membrane type 1-matrix metalloproteinase (MT1-MMP) to invadopodia, and that Stx4 is regulated by Munc18c in this context. Here, it is observed that expression of a construct derived from the N-terminus of Stx4, which interferes with Stx4-Munc18c interaction, leads to perturbed trafficking of MT1-MMP, and reduced invadopodium-based invasion in vitro, in models of triple-negative breast cancer (TNBC). Expression of Stx4 N-terminus also led to increased survival and markedly reduced metastatic burden in multiple TNBC models in vivo. The findings are the first demonstration that disrupting Stx4-Munc18c interaction can dramatically alter metastatic progression in vivo, and suggest that this interaction warrants further investigation as a potential therapeutic target.

IMPLICATIONS

Disrupting the interaction of Syntaxin4 and Munc18c may be a useful approach to perturb trafficking of MT1-MMP and reduce metastatic potential of breast cancers.

There and back again: Intracellular trafficking, release and recycling of matrix metalloproteinases

Matrix metalloproteinases are a family of zinc-dependent endopeptidases that are involved in a large variety of proteolytic processes in physiological and pathological scenarios, including immune cell surveillance, tissue homeostasis, or tumor cell metastasis. This is based on their ability to cleave a plethora of substrates that include components of the extracellular matrix, but also cell surface-associated and intracellular proteins. Accordingly, a tight regulatory web has evolved that closely regulates spatiotemporal activity of specific MMPs. An often underappreciated mechanism of MMP regulation involves their trafficking to and from specific subcellular sites that require MMP activity only for a certain period. In this review, we focus on the current knowledge of MMP intracellular trafficking, their secretion or surface exposure, as well as their recycling back from the cell surface. We discuss molecular mechanisms that enable these steps, in particular microtubule-dependent motility of vesicles that is driven by molecular motors and directed by vesicle regulatory proteins. Finally, we also point out open questions in the field of MMP motility that may become important in the future.

Neutrophils as an emerging therapeutic target and tool for cancer therapy

Activation of neutrophils is necessary for the protection of the host against microbial infection. This property can be used as mode of therapy for cancer treatment. Neutrophils have conflicting dual functions in cancer as either a tumor promoter or inhibitor. Neutrophil-based drug delivery has achieved increased attention in pre-clinical models. This review addresses in detail the different neutrophil constituents, the conflicting function of neutrophils and activation of the neutrophil as an important target of therapy for cancer treatment, and use of neutrophils or neutrophil membrane-derived vesicles as vehicles for drug delivery and targeting.

Up-regulation expression and prognostic significance of Syntaxin4 in kidney renal clear cell carcinoma

BACKGROUND

Syntaxin4 (STX4) gene encodes the protein STX4, a member of soluble N-ethylmaleimide-sensitive factor attachment protein receptors protein, playing a vital role in cell invadopodium formation and invasion, which is associated with the malignant progression of various human cancers. However, the expression and prognostic significance of STX4 in kidney renal clear cell carcinoma (KIRC) remain to be investigated.

METHODS

In this study, we collected the mRNA expression of STX4 in 535 KIRC patients from The Cancer Genome Atlasthrough the University of California Santa Cruz Xena database platform. Then we explored the expression of STX4 in KIRC, and the relationship with clinicopathological characteristics and prognostic value. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes function enrichment analyses were used to explore the potential mechanism of STX4 in KIRC. qRT-PCR analysis was performed toverify the above results with real world tissue specimens.

RESULTS

The results indicated that STX4 was up-expressed in KIRC, and were associated with higher histological grade, advanced stage, and poorer prognosis. Moreover, elevated STX4 expression is an independent risk factor for KIRC. qRT-PCR analysis showed that STX4 was significantly elevated in 10 paired of KIRC samples compared to normal samples. Functional enrichment analysis indicated that endo/exocytosis, autophagy, mTOR signaling pathway, and NOD-like receptor signaling pathway were enriched.

CONCLUSIONS

In summary, STX4 is constantly up-expressed in KIRC tissues, associated with a poor prognosis. We suggest that it can be an effective biomarker for the prognosis of KIRC and may be a novel therapeutic target in KIRC.

Targeting SNARE-Mediated Vesicle Transport to Block Invadopodium-Based Cancer Cell Invasion

During metastasis, cancer cells can invade extracellular matrix (ECM) through a process mediated by matrix-degrading protrusions of the plasma membrane, termed invadopodia. Formation of invadopodia correlates with cells’ invasive and metastatic potential, and thus presents a potential target for therapeutic approaches to target metastatic progression. Invadopodia formation is dependent on the recruitment of proteins involved in intracellular signaling, actin cytoskeleton remodeling, and proteolytic matrix modification. The latter includes matrix degrading enzymes such as MT1-MMP, MMP2, and MMP9. These essential invadopodium-associated enzymes are required for localized matrix degradation, and their localization at invadopodia is central to invadopodium-based cancer cell invasion. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) facilitate intracellular vesicle traffic, including that involved in the transport of invadopodium-associated proteins, and in so doing promote modification of ECM and modulation of signaling pathways involved in the movement of cancer cells. Specific SNARE complexes have been found to support invadopodia formation, and these complexes are, in turn, regulated by associated proteins that interact specifically with SNAREs. Targeting SNARE regulatory proteins thus provides a possible approach to disrupt SNARE-dependent delivery of invadopodial proteins, including MT1-MMP, to sites of ECM modification. Here, we review recent studies of SNARE regulators that hold potential as targets for the development of anti-metastatic therapies for patients burdened with invadopodia-forming cancer types.

Regulation of MT1-MMP Activity through Its Association with ERMs

Membrane-bound proteases play a key role in biology by degrading matrix proteins or shedding adhesion receptors. MT1-MMP metalloproteinase is critical during cancer invasion, angiogenesis, and development. MT1-MMP activity is strictly regulated by internalization, recycling, autoprocessing but also through its incorporation into tetraspanin-enriched microdomains (TEMs), into invadopodia, or by its secretion on extracellular vesicles (EVs). We identified a juxtamembrane positively charged cluster responsible for the interaction of MT1-MMP with ERM (ezrin/radixin/moesin) cytoskeletal connectors in breast carcinoma cells. Linkage to ERMs regulates MT1-MMP subcellular distribution and internalization, but not its incorporation into extracellular vesicles. MT1-MMP association to ERMs and insertion into TEMs are independent phenomena, so that mutation of the ERM-binding motif in the cytoplasmic region of MT1-MMP does not preclude its association with the tetraspanin CD151, but impairs the accumulation and coalescence of CD151/MT1-MMP complexes at actin-rich structures. Conversely, gene deletion of CD151 does not impact on MT1-MMP colocalization with ERM molecules. At the plasma membrane MT1-MMP autoprocessing is severely dependent on ERM association and seems to be the dominant regulator of the enzyme collagenolytic activity. This newly characterized MT1-MMP/ERM association can thus be of relevance for tumor cell invasion.

Annexin A8 can serve as potential prognostic biomarker and therapeutic target for ovarian cancer: based on the comprehensive analysis of Annexins

BACKGROUND

Annexins are involved in vesicle trafficking, cell proliferation and apoptosis, but their functional mechanisms in ovarian cancer remain unclear. In this study, we analyzed Annexins in ovarian cancer using different databases and selected Annexin A8 (ANXA8), which showed the greatest prognostic value, for subsequent validation in immunohistochemical (IHC) assays.

METHODS

The mRNA expression levels, genetic variations, prognostic values and gene-gene interaction network of Annexins in ovarian cancer were analyzed using the Oncomine, Gene Expression Profiling Interactive Analysis (GEPIA), cBioPortal, Kaplan-Meier plotter and GeneMANIA database. ANXA8 was selected for analyzing the biological functions and pathways of its co-expressed genes, and its correlation with immune system responses via the Database for Annotation, Visualization, and Integrated Discovery (DAVID) and the TISIDB database, respectively. We validated the expression of ANXA8 in ovarian cancer via IHC assays and analyzed its correlation with clinicopathological parameters and prognosis.

RESULTS

ANXA2/3/8/11 mRNA expression levels were significantly upregulated in ovarian cancer, and ANXA5/6/7 mRNA expression levels were significantly downregulated. Prognostic analysis suggested that significant correlations occurred between ANXA2/4/8/9 mRNA upregulation and poor overall survival, and between ANXA8/9/11 mRNA upregulation and poor progression-free survival in patients with ovarian serous tumors. Taken together, results suggested that ANXA8 was most closely associated with ovarian cancer tumorigenesis and progression. Further analyses indicated that ANXA8 may be involved in cell migration, cell adhesion, and vasculature development, as well as in the regulation of PI3K-Akt, focal adhesion, and proteoglycans. Additionally, ANXA8 expression was significantly correlated with lymphocytes and immunomodulators. The IHC results showed that ANXA8 expression was higher in the malignant tumor group than in the borderline and benign tumor groups and normal ovary group, and high ANXA8 expression was an independent risk factor for survival and prognosis of ovarian cancer patients (P = 0.013).

CONCLUSIONS

Members of the Annexin family display varying degrees of abnormal expressions in ovarian cancer. ANXA8 was significantly highly expressed in ovarian cancer, and high ANXA8 expression was significantly correlated with poor prognosis. Therefore, ANXA8 is a high candidate as a novel biomarker and therapeutic target for ovarian cancer.

Invasion by activated macrophages requires delivery of nascent membrane-type-1 matrix metalloproteinase through late endosomes/lysosomes to the cell surface

Macrophage migration into injured or infected tissue is a key aspect in the pathophysiology of many diseases where inflammation is a driving factor. Membrane-type-1 matrix metalloproteinase (MT1-MMP) cleaves extracellular matrix components to facilitate invasion. Here we show that, unlike the constitutive MT1-MMP surface recycling seen in cancer cells, unactivated macrophages express low levels of MT1-MMP. Upon lipopolysaccharide (LPS) activation, MT1-MMP synthesis dramatically increases 10-fold at the surface by 15 hours. MT1-MMP is trafficked from the Golgi complex to the surface via late endosomes/lysosomes in a pathway regulated by the late endosome/lysosome R-SNAREs VAMP7 and VAMP8. These form two separate complexes with the surface Q-SNARE complex Stx4/SNAP23 to regulate MT1-MMP delivery to the plasma membrane. Loss of either one of these SNAREs leads to a reduction in surface MT1-MMP, gelatinase activity and reduced invasion. Thus, inhibiting MT1-MMP transport through this pathway could reduce macrophage migration and the resulting inflammation.

Comparative Analysis of the Transcriptome and Proteome during Mouse Placental Development

The condition of the placenta is a determinant of the short- and long-term health of the mother and the fetus. However, critical processes occurring in early placental development, such as trophoblast invasion and establishment of placental metabolism, remain poorly understood. To gain a better understanding of the genes involved in regulating these processes, we utilized a multiomics approach, incorporating transcriptome, proteome, and phosphoproteome data generated from mouse placental tissue collected at two critical developmental time points. We found that incorporating information from both the transcriptome and proteome identifies genes associated with time point-specific biological processes, unlike using the proteome alone. We further inferred genes upregulated on the basis of the proteome data but not the transcriptome data at each time point, leading us to identify 27 genes that we predict to have a role in trophoblast migration or placental metabolism. Finally, using the phosphoproteome data set, we discovered novel phosphosites that may play crucial roles in the regulation of placental transcription factors. By generating the largest proteome and phosphoproteome data sets in the developing placenta, and integrating transcriptome analysis, we uncovered novel aspects of placental gene regulation.

Neutrophil Degranulation, Plasticity, and Cancer Metastasis

Neutrophils are the first responders to inflammation and infection. Recently, an elevated neutrophil-to-lymphocyte ratio has generally become a prognostic indicator of poor overall survival in cancer. Accordingly, heterogeneous ill-defined neutrophil-like populations have been increasingly recognized as important players in cancer development. In addition, neutrophil granule proteins released upon cell activation have been associated with tumor progression; this differential granule mobilization may allow neutrophils - and possibly associated cancer cells - to leave the bloodstream and enter inflamed/infected tissues. This review discusses and proposes how granule mobilization may facilitate neutrophil-mediated transport of cancer cells into different tissues as well as leading to different cellular phenotypes that underlie remarkable neutrophil plasticity. This concept might inform novel neutrophil-centered approaches to putative cancer therapies.

SNAP23 suppresses cervical cancer progression via modulating the cell cycle

OBJECTIVE

Cervical cancer (CC) is one of the most common gynecologic tumors in women worldwide, with poor prognosis and low survival rate. In this study, we identified SNAP23 as a potential tumor suppressor gene in CC.

METHODS

The expression of SNAP23 in tissues and cell lines were measured by qRT-PCR, western blot and IHC. Knockdown of SNAP23 by siRNA and ectopic expression of SNAP23 by overexpression plasmid were performed to observe the biological function of SNAP23 in CC. Xenograft nude mice models were established to measure its function in vivo.

RESULTS

SNAP23 was downregulated in CC tissues and had a negative correlation with advanced clinical characteristics. Ectopic expression of SNAP23 suppressed malignant phonotype of CC while knockdown of SNAP23 promoted the progression of CC in vitro. The flow cytometry analysis revealed that SNAP23 exerted its tumor suppressor activity via inducing G2/M cell cycle arrest. Moreover, xenograft tumor models showed that SNAP23 suppresses tumor growth in vivo.

CONCLUSIONS

Our results revealed that SNAP23 suppressed progression of CC and induced cell cycle G2/M arrest via upregulating p21^cip1 and downregulating CyclinB1.

Nitric Oxide Generated by Tumor-Associated Macrophages Is Responsible for Cancer Resistance to Cisplatin and Correlated With Syntaxin 4 and Acid Sphingomyelinase Inhibition

Tumor microenvironment is fundamental for cancer progression and chemoresistance. Among stromal cells tumor-associated macrophages (TAMs) represent the largest population of infiltrating inflammatory cells in malignant tumors, promoting their growth, invasion, and immune evasion. M2-polarized TAMs are endowed with the nitric oxide (NO)-generating enzyme inducible nitric oxide synthase (iNOS). NO has divergent effects on tumors, since it can either stimulate tumor cells growth or promote their death depending on the source of it; likewise the role of iNOS in cancer differs depending on the cell type. The role of NO generated by TAMs has not been investigated. Using different tumor models in vitro and in vivo we found that NO generated by iNOS of M2-polarized TAMs is able to protect tumor cells from apoptosis induced by the chemotherapeutic agent cisplatin (CDDP). Here, we demonstrate that the protective effect of NO depends on the inhibition of acid sphingomyelinase (A-SMase), which is activated by CDDP in a pathway involving the death receptor CD95. Mechanistic insights indicate that NO actions occur via generation of cyclic GMP and activation of protein kinase G (PKG), inducing phosphorylation of syntaxin 4 (synt4), a SNARE protein responsible for A-SMase trafficking and activation. Noteworthy, phosphorylation of synt4 at serine 78 by PKG is responsible for the proteasome-dependent degradation of synt4, which limits the CDDP-induced exposure of A-SMase to the plasma membrane of tumor cells. This inhibits the cytotoxic mechanism of CDDP reducing A-SMase-triggered apoptosis. This is the first demonstration that endogenous NO system is a key mechanism through which TAMs protect tumor cells from chemotherapeutic drug-induced apoptosis. The identification of the pathway responsible for A-SMase activity downregulation in tumors leading to chemoresistance warrants further investigations as a means to identify new anti-cancer molecules capable of specifically inhibiting synt4 degradation.