Development of a cancer metastasis-on-chip assay for high throughput drug screening

Metastasis is the cause of most triple-negative breast cancer deaths, yet anti-metastatic therapeutics remain limited. To develop new therapeutics to prevent metastasis, pathophysiologically relevant assays that recapitulate tumor microenvironment is essential for disease modeling and drug discovery. Here, we have developed a microfluidic metastasis-on-chip assay of the early stages of cancer metastasis integrated with the triple-negative breast cancer cell line (MDA-MB-231), stromal fibroblasts and a perfused microvessel. High-content imaging with automated quantification methods was optimized to assess the tumor cell invasion and intravasation within the model. Cell invasion and intravasation were enhanced when fibroblasts co-cultured with a breast cancer cell line (MDA-MB-231). However, the non-invasive breast cancer cell line, MCF7, remained non-invasive in our model, even in the presence of fibroblasts. High-content screening of a targeted anti-cancer therapy drug library was conducted to evaluate the drug response sensitivity of the optimized model. Through this screening, we identified 30 compounds that reduced the tumor intravasation by 60% compared to controls. Multi-parametric phenotypic analysis was applied by combining the data from the metastasis-on-chip, cell proliferation and 2D cell migration screens, revealing that the drug library was clustered into eight distinct groups with similar drug responses. Notably, MEK inhibitors were enriched in cluster cell invasion and intravasation. In contrast, drugs with molecular targets: ABL, KIT, PDGF, SRC, and VEGFR were enriched in the drug clusters showing a strong effect on tumor cell intravasation with less impact on cell invasion or cell proliferation, of which, Imatinib, a multi-kinase inhibitor targeting BCR-ABL/PDGFR/KIT. Further experimental analysis showed that Imatinib enhanced endothelial barrier stability as measured by trans-endothelial electrical resistance and significantly reduced the trans-endothelial invasion activity of tumor cells. Our findings demonstrate the potential of our metastasis-on-chip assay as a powerful tool for studying cancer metastasis biology, drug discovery aims, and assessing drug responses, offering prospects for personalized anti-metastatic therapies for triple-negative breast cancer patients.

Alone you go faster, together you go farther

The metastatic process is an extraordinarily complex step-by-step procedure, characterized by many analogies with migratory patterns of humans or animals across our planet. The ongoing interrogation of circulating tumor cells (CTCs), caught in the act of spreading from one location to another, is revealing distinct behaviors including biological, physical, and mechanical features that impact on their likelihood to form metastasis. In this viewpoint, I will discuss some of these findings and provide a perspective on the metastatic journey, open questions and opportunities to exploit some of the most recent discoveries for the development of antimetastasis medicines.

Influence of Macrophages on Vascular Invasion of Inflammatory Breast Cancer Emboli Measured Using an In Vitro Microfluidic Multi-Cellular Platform

Inflammatory breast cancer (IBC) is an aggressive disease with a poor prognosis and a lack of effective treatments. It is widely established that understanding the interactions between tumor-associated macrophages (TAMs) and the tumor microenvironment is essential for identifying distinct targeting markers that help with prognosis and subsequent development of effective treatments. In this study, we present a 3D in vitro microfluidic IBC platform consisting of THP1 M0, M1, or M2 macrophages, IBC cells, and endothelial cells. The platform comprises a collagen matrix that includes an endothelialized vessel, creating a physiologically relevant environment for cellular interactions. Through the utilization of this platform, it was discovered that the inclusion of tumor-associated macrophages (TAMs) led to an increase in the formation of new blood vessel sprouts and enhanced permeability of the endothelium, regardless of the macrophage phenotype. Interestingly, the platforms containing THP-1 M1 or M2 macrophages exhibited significantly greater porosity in the collagen extracellular matrix (ECM) compared to the platforms containing THP-1 M0 and the MDA-IBC3 cells alone. Cytokine analysis revealed that IL-8 and MMP9 showed selective increases when macrophages were cultured in the platforms. Notably, intravasation of tumor cells into the vessels was observed exclusively in the platform containing MDA-IBC3 and M0 macrophages.

Biomimetic on-chip assay reveals the anti-metastatic potential of a novel thienopyrimidine compound in triple-negative breast cancer cell lines

Introduction: This study presents a microfluidic tumor microenvironment (TME) model for evaluating the anti-metastatic efficacy of a novel thienopyrimidines analog with anti-cancer properties utilizing an existing commercial platform. The microfluidic device consists of a tissue compartment flanked by vascular channels, allowing for the co-culture of multiple cell types and providing a wide range of culturing conditions in one device. Methods: Human metastatic, drug-resistant triple-negative breast cancer (TNBC) cells (SUM159PTX) and primary human umbilical vein endothelial cells (HUVEC) were used to model the TME. A dynamic perfusion scheme was employed to facilitate EC physiological function and lumen formation. Results: The measured permeability of the EC barrier was comparable to observed microvessels permeability in vivo. The TNBC cells formed a 3D tumor, and co-culture with HUVEC negatively impacted EC barrier integrity. The microfluidic TME was then used to model the intravenous route of drug delivery. Paclitaxel (PTX) and a novel non-apoptotic agent TPH104c were introduced via the vascular channels and successfully reached the TNBC tumor, resulting in both time and concentration-dependent tumor growth inhibition. PTX treatment significantly reduced EC barrier integrity, highlighting the adverse effects of PTX on vascular ECs. TPH104c preserved EC barrier integrity and prevented TNBC intravasation. Discussion: In conclusion, this study demonstrates the potential of microfluidics for studying complex biological processes in a controlled environment and evaluating the efficacy and toxicity of chemotherapeutic agents in more physiologically relevant conditions. This model can be a valuable tool for screening potential anticancer drugs and developing personalized cancer treatment strategies.

Risk Factors of Contrast Agent Intravasation With Sulfur Hexafluoride Microbubble During Hysterosalpingo-Contrast Sonography

OBJECTIVES

To analyze the risk factors of sulfur hexafluoride microbubble contrast agent intravasation during hysterosalpingo-contrast sonography (HyCoSy), and to explore a simple prediction model by the obvious clinical history.

METHODS

This was a retrospective study included 299 infertility women who had undergone HyCoSy examination from July 1, 2018 to June 31, 2019. The factors were recorded, including age, endometrial thickness, balloon length, infertility type, history of intrauterine surgery, history of pelvic surgery, and tubal patency. The method of multivariate logistic regression analysis was adopted to analyze the risk factors affecting the contrast agent intravasation, and the receiver operating characteristic curves were plotted to test their efficacy.

RESULTS

Secondary infertility, a history of intrauterine surgery, thin endometrial thickness, and tubal obstruction were all risk factors of the occurrence of intravasation (P < .05). And the area under the receiver operating characteristic curves of the multifactor-combined prediction model of the intravasation was significantly larger than that of single-factor.

CONCLUSIONS

Sonographers and gynecologists should be familiar with the risk factors of intravasation and select the appropriate timing of HyCoSy toward reducing the occurrence of intravasation and other complications after thoroughly explaining and communicating with the patients.

Visualization of the Dynamics of Invasion and Intravasation of the Bacterium That Causes Lyme Disease in a Tissue Engineered Dermal Microvessel Model

Lyme disease is a tick-borne disease prevalent in North America, Europe, and Asia. Despite the accumulated knowledge from epidemiological, in vitro, and in animal studies, the understanding of dissemination of vector-borne pathogens, such as Borrelia burgdorferi (Bb), remains incomplete with several important knowledge gaps, especially related to invasion and intravasation into circulation. To elucidate the mechanistic details of these processes a tissue-engineered human dermal microvessel model is developed. Fluorescently labeled Bb are injected into the extracellular matrix (ECM) to mimic tick inoculation. High resolution, confocal imaging is performed to visualize the sub-acute phase of infection. From analysis of migration paths no evidence to support adhesin-mediated interactions between Bb and ECM components is found, suggesting that collagen fibers serve as inert obstacles to migration. Intravasation occurs at cell-cell junctions and is relatively fast, consistent with Bb swimming in ECM. In addition, it is found that Bb alone can induce endothelium activation, resulting in increased immune cell adhesion but no changes in global or local permeability. Together these results provide new insight into the minimum requirements for Bb dissemination and highlight how tissue-engineered models are complementary to animal models in visualizing dynamic processes associated with vector-borne pathogens.

Conversation before crossing: dissecting metastatic tumor-vascular interactions in microphysiological systems

Tumor metastasis via the circulation requires crossing the vascular barrier twice: first, during intravasation when tumor cells disseminate from the primary site through proximal vasculature, and second, during extravasation, when tumor cells exit the circulation to form distant metastatic seeds. During these key metastatic events, chemomechanical signaling between tumor cells and endothelial cells elicits reciprocal changes in cell morphology and behavior that are necessary to breach the vessel wall. Existing experimental systems have provided a limited understanding of the diverse mechanisms underlying tumor-endothelial interactions during intravasation and extravasation. Recent advances in microphysiological systems have revolutionized the ability to generate miniaturized human tissues with tailored three-dimensional architectures, physiological cell interfaces, and precise chemical and physical microenvironments. By doing so, microphysiological systems enable experimental access to complex morphogenic processes associated with human tumor progression with unprecedented resolution and biological control. Here, we discuss recent examples in which microphysiological systems have been leveraged to reveal new mechanistic insight into cellular and molecular control systems operating at the tumor-endothelial interface during intravasation and extravasation.

Operator's Influence on Contrast Agent Intravasation During Hysterosalpingo-Contrast Sonography: Explanation Based on a Physics Model

Objective

To analyze the risk factors of the operators on contrast agent intravasation during hysterosalpingo-contrast sonography (HyCoSy).

Methods

We retrospectively collected 399 infertile women who underwent HyCoSy by the same sonographer. These patients were divided into two groups according to the way how the assistants connected the syringe to the uterus radiography catheter to inject the contrast agent. We analyzed whether the use of different contrast bolus injection methods had any influence on the incidence of intravasation during HyCoSy.

Results

There was no significant difference between the two groups with different cross-sectional areas of the syringe outflow tract in the risk variables for intravasation, but the intravasation rates of the two groups were different, 26.4% in group A and 17.1% in group B, P <0.05. The primary manifestation was that when both fallopian tubes were unobstructed, the intravasation rate of group B with smaller cross-sectional area of the outflow tract of the syringe was lower, and the difference was statistically significant. The inferences drawn from our physics model were also in line with the clinical results.

Conclusion

The influence of different operators on the contrast agent intravasation rate of HyCoSy cannot be ignored. The assistants of HyCoSy examination should inject the contrast agent slowly and steady, and a needle can be used as a flow restrictor to control the flow into the uterine cavity per unit time, slow down the rising speed of intrauterine pressure, and avoid the accumulation of contrast agent in the uterine cavity, so as to reduce the intravasation caused by operator factors.

Blood-Lymphatic Integrated System with Heterogeneous Melanoma Spheroids via In-Bath Three-Dimensional Bioprinting for Modelling of Combinational Targeted Therapy

Although metastatic melanoma can be managed with chemotherapy, its heterogeneity and resistance to therapy remain poorly understood. In addition to the spread of melanoma in the bloodstream, melanoma-stroma interaction and the lymphatic system play active roles in said heterogeneity and resistance, leading to its progression and metastasis. Reproducing the complexities of the melanoma microenvironment in vitro will help understanding its progression and enhance the translatability of potential cancer therapeutics. A blood-lymphatic integrated system with heterogeneous melanoma spheroids (BLISH) using the in-bath bioprinting process is developed. The process uniformly prints size-controllable metastatic melanoma spheroids along with biomimetic blood and lymphatic vessels (LVs). The system reproduces hallmark events of metastatic melanoma, such as tumor stroma interaction, melanoma invasion, and intravasation. The application of the system to investigate the anticancer effect of combinational targeted therapy suggests that it can be used to study the pathophysiology of melanoma and improve the accuracy of drug response monitoring in skin cancer.

Development of a Nomogram for Predicting Intravasation Before Transvaginal 4-Dimensional Hysterosalpingo-Contrast Sonography

Background

Intravasation during transvaginal 4-dimensional hysterosalpingo-contrast sonography (TVS 4D-HyCoSy) may lead to false-negative results in tubal patency evaluation. Although the influencing factors associated with intravasation have been investigated, some factors are only identified during 4D-HyCoSy, thus currently no studies on preventing intravasation. However, several preprocedural features can be collected in advance, which may be valuable in predicting intravasation.

Objective

The purpose of this study is to establish a nomogram incorporating the preprocedural features to predict the risk of intravasation before TVS 4D-HyCoSy.

Methods

The data of 276 infertile women with patent fallopian tubes were analyzed retrospectively. They were assigned to the study group (n = 62) and the control group (n = 214) according to the development of intravasation. The preprocedural characteristics were collected to investigate the predictors independently associated with intravasation, which were then served as the construction of a nomogram. The performance of the nomogram was verified internally.

Results

History of uterine curettage (OR = 2.341, P = 0.009), endometrial thickness (OR = 0.587, P < 0.001), and examination schedule (OR = 0.790, P = 0.024) were found to be the independent influencing factors associated with intravasation. The established nomogram incorporating these preprocedural features was useful for predicting the risk of intravasation prior to 4D-HyCoSy. It yielded net benefits when the predicted probability was less than 50%.

Conclusion

The nomogram incorporating the preprocedural characteristics achieved a net benefit for clinical decision-making when the estimated risk was less than 50%. It is recommended to change the examination schedule for patients with an estimated risk greater than 50% and perform 4D-HyCoSy when the risk is less than 50%.

Combination of Resminostat with Ruxolitinib Exerts Antitumor Effects in the Chick Embryo Chorioallantoic Membrane Model for Cutaneous T Cell Lymphoma

Simple Summary

The combination of Resminostat (HDACi) and Ruxolitinib (JAKi) exerted cytotoxic effects and inhibited proliferation of CTCL cell lines (MyLa, SeAx) in vitro. The aim of the present study was to validate their antitumor effects in vivo using the chick embryo chorioallantoic membrane (CAM) model, which allows quick and efficient monitoring of tumor growth, migration, invasion, and metastatic potential. The drug combination exhibited a significant inhibition of primary tumor size, and inhibited intravasation and extravasation of tumor cells to the liver and lung. It also exerted an inhibitory effect in the migration and invasion of tumor cells and significantly reduced key signaling pathway activation. Our data demonstrate that the CAM assay could be employed as a preclinical in vivo model in CTCL for pharmacological testing, and that the combination of Resminostat and Ruxolitinib exerts significant antitumor effects in CTCL progression that need to be further evaluated in a clinical setting.

Abstract

The combination of Resminostat (HDACi) and Ruxolitinib (JAKi) exerted cytotoxic effects and inhibited proliferation of CTCL cell lines (MyLa, SeAx) in previously published work. A xenograft tumor formation was produced by implanting the MyLa or SeAx cells on top of the chick embryo chorioallantoic membrane (CAM). The CAM assay protocol was developed to monitor the metastatic properties of CTCL cells and the effects of Resminostat and/or Ruxolitinib in vivo. In the spontaneous CAM assays, Resminostat and Ruxolitinib treatment inhibited the cell proliferation (p < 0.001) of MyLa and SeAx, and induced cell apoptosis (p < 0.005, p < 0.001, respectively). Although monotherapies reduced the size of primary tumors in the metastasis CAM assay, the drug combination exhibited a significant inhibition of primary tumor size (p < 0.0001). Furthermore, the combined treatment inhibited the intravasation of MyLa (p < 0.005) and SeAx cells (p < 0.0001) in the organs, as well as their extravasation to the liver (p < 0.0001) and lung (p < 0.0001). The drug combination also exerted a stronger inhibitory effect in migration (p < 0.0001) rather in invasion (p < 0.005) of both MyLa and SeAx cells. It further reduced p-p38, p-ERK, p-AKT, and p-STAT in MyLa cells, while it decreased p-ERK and p-STAT in SeAx cells in CAM tumors. Our data demonstrated that the CAM assay could be employed as a preclinical in vivo model in CTCL for pharmacological testing. In agreement with previous in vitro data, the combination of Resminostat and Ruxolitinib was shown to exert antitumor effects in CTCL in vivo.

Directed movement toward, translocation along, penetration into and exit from vascular networks by breast cancer cells in 3D

We developed a computer-assisted platform using laser scanning confocal microscopy to 3D reconstruct in real-time interactions between metastatic breast cancer cells and human umbilical vein endothelial cells (HUVECs). We demonstrate that MB-231 cancer cells migrate toward HUVEC networks, facilitated by filopodia, migrate along the network surfaces, penetrate into and migrate within the HUVEC networks, exit and continue migrating along network surfaces. The system is highly amenable to 3D reconstruction and computational analyses, and assessments of the effects of potential anti-metastasis monoclonal antibodies and other drugs. We demonstrate that an anti-RHAMM antibody blocks filopodium formation and all of the behaviors that we found take place between MB-231 cells and HUVEC networks.

The gate to metastasis: key players in cancer cell intravasation

Metastasis is a leading cause of cancer‐related death and consists of a sequence of events including tumor expansion, intravasation of cancer cells into the circulation, survival in the bloodstream, extravasation at distant sites, and subsequent organ colonization. Particularly, intravasation is a process whereby cancer cells transverse the endothelium and leave the primary tumor site, pioneering the metastatic cascade. The identification of those mechanisms that trigger the entry of cancer cells into the bloodstream may reveal fundamentally novel ways to block metastasis at its start. Multiple factors have been implicated in cancer progression, yet, signals that unequivocally provoke the detachment of cancer cells from the primary tumor are still under investigation. Here, we discuss the role of intrinsic properties of cancer cells, tumor microenvironment, and mechanical cues in the intravasation process, outlining studies that suggest the involvement of various factors and highlighting current understanding and open questions in the field.

Breast Cancer Cell Re-Dissemination from Lung Metastases-A Mechanism for Enhancing Metastatic Burden

Although metastatic disease is the primary cause of mortality in cancer patients, the mechanisms leading to overwhelming metastatic burden are still incompletely understood. Metastases are the endpoint of a series of multi-step events involving cancer cell intravasation, dissemination to distant organs, and outgrowth to metastatic colonies. Here we show, for the first-time, that breast cancer cells do not solely disseminate to distant organs from primary tumors and metastatic nodules in the lymph nodes, but also do so from lung metastases. Thus, our findings indicate that metastatic dissemination could continue even after the removal of the primary tumor. Provided that the re-disseminated cancer cells initiate growth upon arrival to distant sites, cancer cell re-dissemination from metastatic foci could be one of the crucial mechanisms leading to overt metastases and patient demise. Therefore, the development of new therapeutic strategies to block cancer cell re-dissemination would be crucial to improving survival of patients with metastatic disease.

Biomimetic Microfluidic Platforms for the Assessment of Breast Cancer Metastasis

Of around half a million women dying of breast cancer each year, more than 90% die due to metastasis. Models necessary to understand the metastatic process, particularly breast cancer cell extravasation and colonization, are currently limited and urgently needed to develop therapeutic interventions necessary to prevent breast cancer metastasis. Microfluidic approaches aim to reconstitute functional units of organs that cannot be modeled easily in traditional cell culture or animal studies by reproducing vascular networks and parenchyma on a chip in a three-dimensional, physiologically relevant in vitro system. In recent years, microfluidics models utilizing innovative biomaterials and micro-engineering technologies have shown great potential in our effort of mechanistic understanding of the breast cancer metastasis cascade by providing 3D constructs that can mimic in vivo cellular microenvironment and the ability to visualize and monitor cellular interactions in real-time. In this review, we will provide readers with a detailed discussion on the application of the most up-to-date, state-of-the-art microfluidics-based breast cancer models, with a special focus on their application in the engineering approaches to recapitulate the metastasis process, including invasion, intravasation, extravasation, breast cancer metastasis organotropism, and metastasis niche formation.

Prominent Role of Histone Modifications in the Regulation of Tumor Metastasis

Tumor aggressiveness and progression is highly dependent on the process of metastasis, regulated by the coordinated interplay of genetic and epigenetic mechanisms. Metastasis involves several steps of epithelial to mesenchymal transition (EMT), anoikis resistance, intra- and extravasation, and new tissue colonization. EMT is considered as the most critical process allowing cancer cells to switch their epithelial characteristics and acquire mesenchymal properties. Emerging evidence demonstrates that epigenetics mechanisms, DNA methylation, histone modifications, and non-coding RNAs participate in the widespread changes of gene expression that characterize the metastatic phenotype. At the chromatin level, active and repressive histone post-translational modifications (PTM) in association with pleiotropic transcription factors regulate pivotal genes involved in the initiation of the EMT process as well as in intravasation and anoikis resistance, playing a central role in the progression of tumors. Herein, we discuss the main epigenetic mechanisms associated with the different steps of metastatic process, focusing in particular on the prominent role of histone modifications and the modifying enzymes that mediate transcriptional regulation of genes associated with tumor progression. We further discuss the development of novel treatment strategies targeting the reversibility of histone modifications and highlight their importance in the future of cancer therapy.

Fluoroscopically guided lumbar spine interlaminar and transforaminal epidural injections: inadvertent intravascular injection

BACKGROUND

Inadvertent intravascular injection is a rare but catastrophic complication of lumbar epidural injections.

PURPOSE

To determine risk factors for inadvertent intravascular injection in fluoroscopically guided lumbar spine epidural injections.

MATERIAL AND METHODS

A total of 212 patients who presented for lumbar interlaminar or transforaminal injection were prospectively enrolled. Patient demographics, history of surgery, injection side, site and approach, and volume of contrast injected were recorded.

RESULTS

There were 89 (42%) interlaminar and 123 (58%) transforaminal injections. For 36 (17%) patients, there had been surgery at the injected or adjacent lumbar level. There were 25 (12%) inadvertent intravascular injections, with an incidence of 2/93 (2%) for interlaminar and 23/119 (19%) for transforaminal injections. The patients with inadvertent intravascular injection were older (P = 0.017) and had prior surgery at or adjacent to the level of injection (P < 0.0001). Transforaminal approach had a higher intravasation rate than interlaminar injections, both when comparing the entire cohort (P = 0.0001) and only patients without prior surgery (P = 0.01). In multivariable logistic regression analysis, transforaminal injections (odds ratio [OR] 9.77, 95% confidence interval [CI] 2.14-44.6, P = 0.003) and prior surgery at or adjacent to the level of injection (OR 5.71, 95% CI 2.15-15.15, P < 0.001) were independently associated with increased risk of inadvertent intravascular injections.

CONCLUSION

Inadvertent intravascular injection occurred in 12% of our lumbar injection cohort and is more common with transforaminal injections, in older patients, and with prior lumbar surgery at or adjacent to the level of injection.

A Tissue-Engineered 3D Microvessel Model Reveals the Dynamics of Mosaic Vessel Formation in Breast Cancer

In solid tumors, vascular structure and function varies from the core to the periphery. This structural heterogeneity has been proposed to influence the mechanisms by which tumor cells enter the circulation. Blood vessels exhibit regional defects in endothelial coverage, which can result in cancer cells directly exposed to flow and potentially promoting intravasation. Consistent with prior reports, we observed in human breast tumors and in a mouse model of breast cancer that approximately 6% of vessels consisted of both endothelial cells and tumor cells, so-called mosaic vessels. Due, in part, to the challenges associated with observing tumor-vessel interactions deep within tumors in real-time, the mechanisms by which mosaic vessels form remain incompletely understood. We developed a tissue-engineered model containing a physiologically realistic microvessel in coculture with mammary tumor organoids. This approach allows real-time and quantitative assessment of tumor-vessel interactions under conditions that recapitulate many in vivo features. Imaging revealed that tumor organoids integrate into the endothelial cell lining, resulting in mosaic vessels with gaps in the basement membrane. While mosaic vessel formation was the most frequently observed interaction, tumor organoids also actively constricted and displaced vessels. Furthermore, intravasation of cancer cell clusters was observed following the formation of a mosaic vessel. Taken together, our data reveal that cancer cells can rapidly reshape, destroy, or integrate into existing blood vessels, thereby affecting oxygenation, perfusion, and systemic dissemination. Our novel assay also enables future studies to identify targetable mechanisms of vascular recruitment and intravasation. SIGNIFICANCE: A tissue-engineered microdevice that recapitulates the tumor-vascular microenvironment enables real-time imaging of the cellular mechanisms of mosaic vessel formation and vascular defect generation.

Green urine sign after laparoscopic chromopertubation as an effect of severe contrast intravasation: a report of three cases

Tubal diseases are responsible for 25% to 35% of female infertility. Laparoscopic chromopertubation is the gold standard for assessing tubal patency when female infertility is suspected. Intravasation is a complication of intrauterine procedures involving the passage of fluid filling the uterine cavity into the bloodstream through endometrial vessels (from the myometrial veins to the uterine venous plexuses). This complication has been described during hysterosalpingography and sonohysterosalpingography. We herein present a report of three cases in which severe intravasation occurred during laparoscopic chromopertubation using methylene blue as a contrast agent. The intravasation manifested as green urine (i.e., the "green urine sign"). The presence of methylene blue in the urine and blood was confirmed by laboratory tests. All three patients had risk factors for intravasation as described in the literature (unilateral or bilateral tubal obstruction, endometriosis, and previous intrauterine procedures for Mullerian duct anomalies and Asherman's syndrome). The green urine sign appeared a few hours after laparoscopic chromopertubation and spontaneously resolved after 24 hours. Cystoscopy was performed to rule out bladder injury. All three patients required only clinical observation.

Lipiodol hysterosalpingogram: A modified HSG technique to minimize risks associated with lipiodol use

Assessment of tubal patency and therapeutic tubal flushing using Lipiodol, an oil-soluble contrast media (OSCM), has been shown to enhance fertility, resulting in increased interest in the use of Lipiodol. A modified hysterosalpingogram (HSG) technique, including a supplementary ultrasound with the contrast in situ, is recommended when using Lipiodol, taking into account both safety issues and technical challenges specific to Lipiodol.

Comparing volumetric and biochemical assessment of intravasation caused by hysteroscopic surgery

BACKGROUND

During hysteroscopic surgery intravasation of irrigation fluid occurs, leading to potentially dangerous intravascular fluid overload. Currently, intravasation is usually measured volumetrically as fluid deficit. Intravasation could also be calculated using the decrease in hemoglobin or increase in chloride ion concentration, both phenomena known to result from intravasation. We compared the values of intravasation measured volumetrically as fluid deficit versus calculated from the biochemical change in hemoglobin and chloride. We expected that these values would show strong correlation and agreement.

METHODS

In a retrospective data analysis of 51 patients who underwent hysteroscopic resection of myomas or endometrium a pre and post procedure concentration of haemoglobin and chloride was available. The fluid deficit was plotted against the two versions of calculated intravasation. Furthermore, we put the data into Bland-Altman plots to scrutinize their relationship.

RESULTS

The volumetric assessed fluid deficit and both versions of biochemically assessed intravasation, either using the change in hemoglobin or chloride ion concentration, turned out to be three totally different entities with weak correlation. Bland-Altman plots show too wide limits of agreement, and a striking difference between the two methods of calculated intravasation.

CONCLUSION

Our study shows significant differences and poor agreement between volumetric and biochemically assessed intravasation. Based on this study, routinely assessing intravasation by biochemical methods does not have additional benefit compared to the volumetric fluid deficit. It remains unclear which method resembles true intravasation.

Novel therapeutic targets for cancer metastasis

Introduction: Metastatic cancers are extremely difficult to treat, and account for the vast majority of cancer-related deaths. The dissemination of tumor cells to distant sites is highly dynamic, asynchronous, and involves both tumor and host intrinsic factors. Effective therapeutic targets to block metastasis will need to disrupt key pathways that are required for multiple stages of metastasis.Areas covered: This review discusses the heterogeneity of cancers and metastasis, with an emphasis on motility as a key driver trait of metastasis. Recent metastatic cancer studies that identified either host or cancer cell intrinsic factors important for metastasis, using single gene-deficient animal models or 3D intravital imaging of avian embryo models, are also discussed. Potential metastatic blocking targets are listed as they relate to metastatic cancer therapy.Expert opinion: The development of metastatic disease is a complex interplay of genetic and epigenetic factors from the host and cancer cells acting in a patient-specific manner. Inhibiting key driver traits of metastasis should yield survival benefit at any stage of the disease, and we look forward to the next generation of personalized medicines for cancer therapy that target cancer cell motility for increased therapeutic efficacy.

Complications after hysterosalpingography with oil- or water-based contrast: results of a nationwide survey

STUDY QUESTION

What is the incidence of complications after hysterosalpingography (HSG) using oil-based contrast versus water-based contrast?

SUMMARY ANSWER

Among 5165 women undergoing HSG, the most frequently reported complication after HSG with oil- and water-based contrast was intravasation of contrast medium (4.8% versus 1.3%, respectively), which was without further consequences, and pulmonary embolization or death did not occur.

WHAT IS KNOWN ALREADY

An HSG with oil-based contrast increases pregnancy rates in women with unexplained infertility. However, there have been some concerns regarding complications, including the risks of intravasation of the contrast medium, oil embolism and infection. Here, we present the incidence of complications after HSG with different types of contrast media used in the Netherlands in the year 2017.

STUDY DESIGN SIZE DURATION

In January 2018, an electronic survey was sent to all 73 clinics in the Netherlands that perform HSG. The survey consisted of 12 questions addressing the number of HSGs performed in 2017, the amount and type of contrast medium used, the occurrence of post-procedural complications and what their clinical consequences were. Non-responding clinics were sent multiple reminders.

PARTICIPANTS/MATERIALS SETTING METHODS

We calculated the incidence of the complications and reported on their clinical consequences. Furthermore, we examined the average amount of contrast used as well as the administration of prophylactic antibiotics.

MAIN RESULTS AND THE ROLE OF CHANCE

The response rate was 96% (67/70) (during the study, one site closed and was not included while two clinics no longer performed HSGs). In the 67 clinics, 3289 HSGs with oil-based contrast and 1876 HSGs with water-based contrast were performed in 2017. The median amount of contrast used was 8.0 ml (interquartile range (IQR) 7.0-10.0) for oil-based contrast and 10.0 ml for water-based contrast (IQR 10.0-10.0). Antibiotic prophylaxis was administered in 61% (41/67) of the clinics. Intravasation occurred in 4.8% of the HSGs performed with oil-based contrast and in 1.3% of the HSGs with water-based contrast (relative risk (RR), 3.6; CI, 2.4-5.4). Pulmonary embolism or death was not reported. Pelvic inflammatory disease (PID) occurred in 0.3% of the HSGs performed with oil-based contrast versus 0.4% with water-based contrast. PID occurred in 0.3% of the HSGs in clinics using antibiotic prophylaxis and 0.2% in clinics not using antibiotic prophylaxis. Allergic reactions were reported in one HSG performed with oil-based contrast (0.03%) compared with two HSGs performed with water-based contrast (0.1%). Anaphylactic reactions did not occur. The overall complication rate was 5.1% in the clinics that used oil-based contrast versus 1.8% in the clinics that used water-based contrast (RR, 2.8; CI, 1.9-4.0; P-value, <0.0001).

LIMITATIONS REASONS FOR CAUTION

Half of the clinics did not routinely register complications, and the incidence of the complications in their clinic was based on the recall of the clinician. Estimated complication rates in the clinics with and without systematic registration did not significantly differ. The survey asked about the frequency of intravasation but no classification system is being used in daily practice, which may create differences in reporting. There was no standard screening of post-HSG thyroid function for the mother and the foetus.

WIDER IMPLICATIONS OF THE FINDINGS

In this nationwide cohort study, the complication rates after HSG were low. Intravasation occurred more frequently with the use of oil-based contrast compared with water-based contrast but did not lead to any problems or symptoms in any of the women. We therefore conclude that safety concerns should not be a reason to deny the use of oil-based contrast in women with unexplained infertility. The data also support that fluoroscopy appears to be an essential safety measure during HSG.

STUDY FUNDING/COMPETING INTERESTS

This work was partly funded by Guerbet, France. I.R. reports receiving travel fee for presenting at the Congress of the American Society for Reproductive Medicine 2019 from Guerbet. V.M. reports receiving travel and speaker's fee as well as research grants from Guerbet. K.D. reports receiving travel and speaker's fee from Guerbet. B.W.M. is supported by an National Health and Medical Research Council (NHMRC) Practitioner Fellowship (GNT1082548). B.W.M. reports consultancy for ObsEva, Merck KGaA and Guerbet and travel and research grants from Merck KGaA and Guerbet. The other authors do not report conflicts of interest.

TRIAL REGISTRATION NUMBER

N19.056.

The Extracellular Matrix Modulates the Metastatic Journey

The extracellular matrix is perturbed in tumors. The tumor matrix promotes the growth, survival, and invasion of the cancer and modifies fibroblast and immune cell behavior to drive metastasis and impair treatment. Here, we discuss how the tumor matrix regulates metastasis by fostering tumor cell invasion into the stroma and migration toward the vasculature. We describe the role of the tumor matrix in cancer cell intravasation and vascular dissemination. We examine the impact of the matrix on disseminated tumor cell extravasation and on tumor dormancy and metastatic outgrowth. Finally, we discuss the clinical outcome of therapeutics that normalize tumor-matrix interactions.

Mechanisms behind prometastatic changes induced by neoadjuvant chemotherapy in the breast cancer microenvironment

Chemotherapy, along with surgery and radiotherapy, is a key treatment option for malignant tumors. Neoadjuvant chemotherapy (NACT) reduces the tumor size and enables total tumor resection. In addition, NACT is believed to be more effective in destroying micrometastases than the same chemotherapy performed after surgery. To date, various NACT regimens have been tested and implemented, which provide a favorable outcome in primary tumors and reduce the risk of progression. However, there is increasing evidence of the NACT ability to increase the risk of cancer progression. This review discusses potential mechanisms by which NACT promotes distant metastasis of breast cancer through changes in the microenvironment of tumor cells. We describe prometastatic NACT-mediated changes in angiogenesis, immuno-inflammatory reactions in the stroma, intravasation, and amount of circulating tumor cells. The role of NACT-related cellular stress in cancer metastasis is also discussed.

Defining the Hallmarks of Metastasis

Metastasis is the primary cause of cancer morbidity and mortality. The process involves a complex interplay between intrinsic tumor cell properties as well as interactions between cancer cells and multiple microenvironments. The outcome is the development of a nearby or distant discontiguous secondary mass. To successfully disseminate, metastatic cells acquire properties in addition to those necessary to become neoplastic. Heterogeneity in mechanisms involved, routes of dissemination, redundancy of molecular pathways that can be utilized, and the ability to piggyback on the actions of surrounding stromal cells makes defining the hallmarks of metastasis extraordinarily challenging. Nonetheless, this review identifies four distinguishing features that are required: motility and invasion, ability to modulate the secondary site or local microenvironments, plasticity, and ability to colonize secondary tissues. By defining these first principles of metastasis, we provide the means for focusing efforts on the aspects of metastasis that will improve patient outcomes.

Intravital imaging tumor screen used to identify novel metastasis-blocking therapeutic targets

Cancer cell motility is a key driver of metastasis. Although the intravasation of cancer cells into the blood stream is highly dependent on their motility and metastatic dissemination is the primary cause of cancer related deaths, current therapeutic strategies do not target the genes and proteins that are essential for cell motility. A primary reason for this is because the identification of cell motility-related genes that are relevant in vivo requires the visualization of metastatic lesions forming in an appropriate in vivo model. The cancer research community has lacked an in vivo and intravital metastatic cancer model that could be imaged as motility developed, in real-time. To address this, we developed a novel quantitative in vivo screening platform based on intravital imaging in shell-less ex ovo chick embryos. We applied this imaging approach to screen a human genome-wide short hairpin RNA library (shRNA) versus the highly motile head and neck cancer cells (HEp3 cell line) introduced into the chorioallantoic membrane (CAM) of chick embryos and identified multiple novel in vivo cancer cell motility-associated genes. When the expression of several of the identified genes was inhibited in the HEp3 tumors, we observed a nearly total block of spontaneous cancer metastasis.

Microfluidic Tumor-Vascular Model to Study Breast Cancer Cell Invasion and Intravasation

Cancer is a major leading cause of disease-related death in the world. The severe impact of cancer can be attributed to poor understanding of the mechanisms involved in earliest steps of the metastatic cascade, specifically invasion into the surrounding stroma and intravasation into the blood capillaries. However, conducting integrated biological studies of invasion and intravasation have been challenging, within in vivo models and traditional in vitro assay, due to difficulties in establishing a precise tumor microenvironment. To that end, in this work, a novel 3D microfluidic platform comprised of concentric three-layer cell-laden hydrogels for simultaneous investigation of breast cancer cell invasion and intravasation as well as vasculature maturation influenced by tumor-vascular crosstalk is developed. It was demonstrated that the presence of spontaneously formed vasculature enhance MDA-MB-231 invasion into the 3D stroma. Following invasion, cancer cells are visualized intravasating into the outer vasculature. Additionally, invading cancer cells significantly reduce vessel diameter while increasing permeability, consistent with previous in vivo studies. Major signaling cytokines involved in tumor-vascular crosstalk that govern cancer cell invasion and intravasation are further identified. Taken together, this platform will enable unique insights of critical biological events within the metastatic cascade, with significant potential for developing efficient cancer therapeutics.

Chemical Composition of Scrophularia lucida and the Effects on Tumor Invasiveness in Vitro

A detannified methanolic extract of Scrophularia lucida L. attenuated the formation of cancer cell-induced circular chemorepellent induced defects (CCIDs) in the lymph endothelial cell barrier, which resemble entry ports for the intravasating tumor into the vasculature as a prerequisite for lymph node metastasis. Therefore, the composition of this extract was studied in an activity-guided approach. Since no data on the secondary metabolites of this plant were available, first phytochemical data were collected in the course of the fractionation of the extract. The study resulted in the identification of 14 substances, among them very rare iridoids, such as scrovalentinoside or koelzioside, and several flavonoids (e.g., nepitrin and homoplantaginin). One of the latter group, 2″-O-acetyl-homoplantaginin, is a new natural compound. In the most active fraction, the flavonoid hispidulin was identified as major component and the assay of the pure compound confirmed a contribution of hispidulin to the CCID-inhibitory effects of S. lucida. The activity of the two major iridoids in this assay was less compared to hispidulin.

Apigenin and Luteolin Attenuate the Breaching of MDA-MB231 Breast Cancer Spheroids Through the Lymph Endothelial Barrier in Vitro

Flavonoids, present in fruits, vegetables and traditional medicinal plants, show anticancer effects in experimental systems and are reportedly non-toxic. This is a favorable property for long term strategies for the attenuation of lymph node metastasis, which may effectively improve the prognostic states in breast cancer. Hence, we studied two flavonoids, apigenin and luteolin exhibiting strong bio-activity in various test systems in cancer research and are readily available on the market. This study has further advanced the mechanistic understanding of breast cancer intravasation through the lymphatic barrier. Apigenin and luteolin were tested in a three-dimensional (3-D) assay consisting of MDA-MB231 breast cancer spheroids and immortalized lymph endothelial cell (LEC) monolayers. The 3-D model faithfully resembles the intravasation of breast cancer emboli through the lymphatic vasculature. Western blot analysis, intracellular Ca²⁺ determination, EROD assay and siRNA transfection revealed insights into mechanisms of intravasation as well as the anti-intravasative outcome of flavonoid action. Both flavonoids suppressed pro-intravasative trigger factors in MDA-MB231 breast cancer cells, specifically MMP1 expression and CYP1A1 activity. A pro-intravasative contribution of FAK expression in LECs was established as FAK supported the retraction of the LEC monolayer upon contact with cancer cells thereby enabling them to cross the endothelial barrier. As mechanistic basis, MMP1 caused the phosphorylation (activation) of FAK at Tyr397 in LECs. Apigenin and luteolin prevented MMP1-induced FAK activation, but not constitutive FAK phosphorylation. Luteolin, unlike apigenin, inhibited MMP1-induced Ca²⁺ release. Free intracellular Ca²⁺ is a central signal amplifier triggering LEC retraction through activation of the mobility protein MLC2, thereby enhancing intravasation. FAK activity and Ca²⁺ levels did not correlate. This implicates that the pro-intravasative contribution of FAK and of Ca²⁺ release in LECs was independent of each other and explains the better anti-intravasative effects of luteolin in vitro. In specific formulations, flavonoid concentrations causing significant anti-intravasative effects, can certainly be achieved in vivo. As the therapeutic strategy has to be based on permanent flavonoid treatment both the beneficial and adverse effects have to be investigated in future studies.

Locally Triggered Release of the Chemokine CCL21 Promotes Dendritic Cell Transmigration across Lymphatic Endothelia

Trafficking cells frequently transmigrate through epithelial and endothelial monolayers. How monolayers cooperate with the penetrating cells to support their transit is poorly understood. We studied dendritic cell (DC) entry into lymphatic capillaries as a model system for transendothelial migration. We find that the chemokine CCL21, which is the decisive guidance cue for intravasation, mainly localizes in the trans-Golgi network and intracellular vesicles of lymphatic endothelial cells. Upon DC transmigration, these Golgi deposits disperse and CCL21 becomes extracellularly enriched at the sites of endothelial cell-cell junctions. When we reconstitute the transmigration process in vitro, we find that secretion of CCL21-positive vesicles is triggered by a DC contact-induced calcium signal, and selective calcium chelation in lymphatic endothelium attenuates transmigration. Altogether, our data demonstrate a chemokine-mediated feedback between DCs and lymphatic endothelium, which facilitates transendothelial migration.

•

DC entry into lymphatic capillary induces CCL21 secretion to endothelial junctions

•

Chemokine CCL21 secretion is triggered by calcium fluxes

•

Direct contact by DC induces calcium signaling in LECs

•

Dynamic rather than pre-patterned chemokine CCL21 cues promote DC transmigration

Dissemination from a Solid Tumor: Examining the Multiple Parallel Pathways

Metastasis can be generalized as a linear sequence of events whereby halting one or more steps in the cascade may reduce tumor cell dissemination and ultimately improve patient outcomes. However, metastasis is a complex process with multiple parallel mechanisms of dissemination. Clinical strategies focus on removing the primary tumor and/or treating distant metastases through chemo- or immunotherapies. Successful strategies for blocking metastasis will need to address the parallel mechanisms of dissemination and identify common bottlenecks. Here, we review the current understanding of common dissemination pathways for tumors. Understanding the complexities of metastasis will guide the design of new therapies that halt dissemination.

Circulating tumor cell interactions with macrophages: implications for biology and treatment

Cancer and metastasis are closely associated with inflammation. Macrophages are important effector cells in enhancing tumor proliferation, invasion and providing protection against the immune system. Despite advanced knowledge of tumor-macrophage interactions, the role of macrophages in emergence and invasion of circulating tumor cells (CTCs) is not known. A series of six CTC cell lines have been derived from blood of patients with extensive disease small cell lung cancer (ED-SCLC) in our lab, most likely representing a homogenous cell population of the actual metastasis-initiating cells (MIC) of CTCs. SCLC has an unfavorable prognosis due to rapid dissemination and early chemoresistant relapses. SCLC CTCs recruit macrophages and elicit secretion of various cytokines and the six CTC lines express chitinase-3-like-1 (CHI3L1), vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP9) in abundance. CHI3L1 is cytokine/growth factor expressed in inflammation and cancer and found to be correlated to metastasis and a dismal prognosis. In conclusion, SCLC CTCs have acquired the essential means for aggressiveness and invasion in a tumor microenvironment specifically shaped by macrophages and inflammation.

Endothelial Notch1 Activity Facilitates Metastasis

Endothelial cells (ECs) provide angiocrine factors orchestrating tumor progression. Here, we show that activated Notch1 receptors (N1ICD) are frequently observed in ECs of human carcinomas and melanoma, and in ECs of the pre-metastatic niche in mice. EC N1ICD expression in melanoma correlated with shorter progression-free survival. Sustained N1ICD activity induced EC senescence, expression of chemokines and the adhesion molecule VCAM1. This promoted neutrophil infiltration, tumor cell (TC) adhesion to the endothelium, intravasation, lung colonization, and postsurgical metastasis. Thus, sustained vascular Notch signaling facilitates metastasis by generating a senescent, pro-inflammatory endothelium. Consequently, treatment with Notch1 or VCAM1-blocking antibodies prevented Notch-driven metastasis, and genetic ablation of EC Notch signaling inhibited peritoneal neutrophil infiltration in an ovarian carcinoma mouse model.

Oriented collagen fibers direct tumor cell intravasation

In this work, we constructed a Collagen I-Matrigel composite extracellular matrix (ECM). The composite ECM was used to determine the influence of the local collagen fiber orientation on the collective intravasation ability of tumor cells. We found that the local fiber alignment enhanced cell-ECM interactions. Specifically, metastatic MDA-MB-231 breast cancer cells followed the local fiber alignment direction during the intravasation into rigid Matrigel (∼10 mg/mL protein concentration).

Tumor cell intravasation

The process of entering the bloodstream, intravasation, is a necessary step in the development of distant metastases. The focus of this review is on the pathways and molecules that have been identified as being important based on current in vitro and in vivo assays for intravasation. Properties of the vasculature which are important for intravasation include microvessel density and also diameter of the vasculature, with increased intravasation correlating with increased vessel diameter in some tumors. TGFB signaling can enhance intravasation at least in part through induction of EMT, and we discuss other TGFB target genes that are important for intravasation. In addition to TGFB signaling, a number of studies have demonstrated that activation of EGF receptor family members stimulates intravasation, with downstream signaling through PI3K, N-WASP, RhoA, and WASP to induce invadopodia. With respect to proteases, there is strong evidence for contributions by uPA/uPAR, while the roles of MMPs in intravasation may be more tumor specific. Other cells including macrophages, fibroblasts, neutrophils, and platelets can also play a role in enhancing tumor cell intravasation. The technology is now available to interrogate the expression patterns of circulating tumor cells, which will provide an important reality check for the model systems being used. With a better understanding of the mechanisms underlying intravasation, the goal is to provide new opportunities for improving prognosis as well as potentially developing new treatments.

Invadopodia in context

Invadopodia are dynamic protrusions in motile tumor cells whose function is to degrade extracellular matrix so that cells can enter into new environments. Invadopodia are specifically identified by microscopy as proteolytic invasive protrusions containing TKS5 and cortactin. The increasing complexity in models for the study of invadopodia, including engineered 3D environments, explants, or animal models in vivo, entails a higher level of microenvironment complexity as well as cancer cell heterogeneity. Such experimental setups are rich in information and offer the possibility of contextualizing invadopodia and other motility-related structures. That is, they hold the promise of revealing more realistic microenvironmental conditions under which the invadopodium assembles and functions or in which tumor cells switch to a different cellular phenotype (focal adhesion, lamellipodia, proliferation, and apoptosis). For such an effort, we need a systemic approach to microscopy, which will integrate information from multiple modalities. While the individual technologies needed to achieve this are mostly available, data integration and standardization is not a trivial process. In a systems microscopy approach, microscopy is used to extract information on cell phenotypes and the microenvironment while -omics technologies assess profiles of cancer cell and microenvironment genetic, transcription, translation, and protein makeups. Data are classified and linked via in silico modeling (including statistical and mathematical models and bioinformatics). Computational considerations create predictions to be validated experimentally by perturbing the system through use of genetic manipulations and molecular biology. With such a holistic approach, a deeper understanding of function of invadopodia in vivo will be reached, opening the potential for personalized diagnostics and therapies.

Epithelial-mesenchymal plasticity in carcinoma metastasis

Tumor metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. Metastasis occurs through a series of steps: local invasion, intravasation, transport, extravasation, and colonization. A developmental program termed epithelial-mesenchymal transition (EMT) has been shown to play a critical role in promoting metastasis in epithelium-derived carcinoma. Recent experimental and clinical studies have improved our knowledge of this dynamic program and implicated EMT and its reverse program, mesenchymal-epithelial transition (MET), in the metastatic process. Here, we review the functional requirement of EMT and/or MET during the individual steps of tumor metastasis and discuss the potential of targeting this program when treating metastatic diseases.

Understanding the Biology of Bone Sarcoma from Early Initiating Events through Late Events in Metastasis and Disease Progression

The two most common primary bone malignancies, osteosarcoma (OS), and Ewing sarcoma (ES), are both aggressive, highly metastatic cancers that most often strike teens, though both can be found in younger children and adults. Despite distinct origins and pathogenesis, both diseases share several mechanisms of progression and metastasis, including neovascularization, invasion, anoikis resistance, chemoresistance, and evasion of the immune response. Some of these processes are well-studies in more common carcinoma models, and the observation from adult diseases may be readily applied to pediatric bone sarcomas. Neovascularization, which includes angiogenesis and vasculogenesis, is a clear example of a process that is likely to be similar between carcinomas and sarcomas, since the responding cells are the same in each case. Chemoresistance mechanisms also may be similar between other cancers and the bone sarcomas. Since OS and ES are mesenchymal in origin, the process of epithelial-to-mesenchymal transition is largely absent in bone sarcomas, necessitating different approaches to study progression and metastasis in these diseases. One process that is less well-studied in bone sarcomas is dormancy, which allows micrometastatic disease to remain viable but not growing in distant sites – typically the lungs – for months or years before renewing growth to become overt metastatic disease. By understanding the basic biology of these processes, novel therapeutic strategies may be developed that could improve survival in children with OS or ES.

N-WASP-mediated invadopodium formation is involved in intravasation and lung metastasis of mammary tumors

Invadopodia are proteolytic membrane protrusions formed by highly invasive cancer cells, commonly observed on substrate(s) mimicking extracellular matrix. Although invadopodia are proposed to have roles in cancer invasion and metastasis, direct evidence has not been available. We previously reported that neural Wiskott-Aldrich syndrome protein (N-WASP), a member of WASP family proteins that regulate reorganization of the actin cytoskeleton, is an essential component of invadopodia. Here, we report that N-WASP-mediated invadopodium formation is essential in breast cancer invasion, intravasation and lung metastasis. We established stable cell lines based on MTLn3 rat mammary adenocarcinoma cells that either overexpressed a dominant-negative (DN) N-WASP construct or in which N-WASP expression was silenced by a pSuper N-WASP shRNA. Both the N-WASP shRNA and DN N-WASP cells showed a markedly decreased ability to form invadopodia and degrade extracellular matrix. In addition, formation of invadopodia in primary tumors and collagen I degradation were reduced in the areas of invasion (collagen-rich areas in the invasive edge of the tumor) and in the areas of intravasation (blood-vessel-rich areas). Our results suggest that tumor cells in vivo that have a decreased activity of N-WASP also have a reduced ability to form invadopodia, migrate, invade, intravasate and disseminate to lung compared with tumor cells with parental N-WASP levels.

Targeting tumor cell motility to prevent metastasis

Mortality and morbidity in patients with solid tumors invariably result from the disruption of normal biological function caused by disseminating tumor cells. Tumor cell migration is under intense investigation as the underlying cause of cancer metastasis. The need for tumor cell motility in the progression of metastasis has been established experimentally and is supported empirically by basic and clinical research implicating a large collection of migration-related genes. However, there are few clinical interventions designed to specifically target the motility of tumor cells and adjuvant therapy to specifically prevent cancer cell dissemination is severely limited. In an attempt to define motility targets suitable for treating metastasis, we have parsed the molecular determinants of tumor cell motility into five underlying principles including cell autonomous ability, soluble communication, cell-cell adhesion, cell-matrix adhesion, and integrating these determinants of migration on molecular scaffolds. The current challenge is to implement meaningful and sustainable inhibition of metastasis by developing clinically viable disruption of molecular targets that control these fundamental capabilities.