The role played by the microenvironment in site-specific metastasis

The chemistry and efficacy benefits of polysaccharides from Atractylodes macrocephala Koidz

Atractylodes macrocephala Koidz (AM), traditional Chinese medicine (TCM) with many medicinal values, has a long usage history in China and other oriental countries. The phytochemical investigation revealed the presence of volatile oils, polysaccharides, lactones, flavonoids, and others. The polysaccharides from AM are important medicinal components, mainly composed of glucose (Glc), galactose (Gal), rhamnose (Rha), arabinose (Ara), mannose (Man), galacturonic acid (GalA) and xylose (Xyl). It also showed valuable bioactivities, such as immunomodulatory, antitumour, gastroprotective and intestinal health-promoting, hepatoprotective, hypoglycaemic as well as other activities. At the same time, based on its special structure and pharmacological activity, it can also be used as immune adjuvant, natural plant supplement and vaccine adjuvant. The aim of this review is to summarize and critically analyze up-to-data on the chemical compositions, biological activities and applications of polysaccharide from AM based on scientific literatures in recent years.

Differential immune landscapes in appendicular versus axial skeleton

Roughly 400,000 people in the U.S. are living with bone metastases, the vast majority occurring in the spine. Metastases to the spine result in fractures, pain, paralysis, and significant health care costs. This predilection for cancer to metastasize to the bone is seen across most cancer histologies, with the greatest incidence seen in prostate, breast, and lung cancer. The molecular process involved in this predilection for axial versus appendicular skeleton is not fully understood, although it is likely that a combination of tumor and local micro-environmental factors plays a role. Immune cells are an important constituent of the bone marrow microenvironment and many of these cells have been shown to play a significant role in tumor growth and progression in soft tissue and bone disease. With this in mind, we sought to examine the differences in immune landscape between axial and appendicular bones in the normal noncancerous setting in order to obtain an understanding of these landscapes. To accomplish this, we utilized mass cytometry by time-of-flight (CyTOF) to examine differences in the immune cell landscapes between the long bone and vertebral body bone marrow from patient clinical samples and C57BL/6J mice. We demonstrate significant differences between immune populations in both murine and human marrow with a predominance of myeloid progenitor cells in the spine. Additionally, cytokine analysis revealed differences in concentrations favoring a more myeloid enriched population of cells in the vertebral body bone marrow. These differences could have clinical implications with respect to the distribution and permissive growth of bone metastases.

[Research Status of Tumor-associated Fibroblasts Regulating Immune Cells]

Cancer-associated fibroblasts (CAFs) and tumor-infiltrating immune cells are the most essential components of the tumor microenvironment (TME). They communicate with each other in tumor microenvironment and play a critical role in tumorigenesis and development. CAFs are very heterogeneous and different subtypes of CAFs display different functions. At the same time, it can contribute to the regulation of the function of tumor-infiltrating immune cells and eventually result in the carcinogenesis, tumor progression, invasion, metastasis and other biological behaviors of tumors by producting various growth factors and cytokines etc. Based on the current research results at home and abroad, this paper reviews the recent research progress on the regulation of CAFs on infiltrating immune cells in tumor microenvironment.
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Cancer biology deciphered by single-cell transcriptomic sequencing

Tumors are complex ecosystems in which heterogeneous cancer cells interact with their microenvironment composed of diverse immune, endothelial, and stromal cells. Cancer biology had been studied using bulk genomic and gene expression profiling, which however mask the cellular diversity and average the variability among individual molecular programs. Recent advances in single-cell transcriptomic sequencing have enabled a detailed dissection of tumor ecosystems and promoted our understanding of tumorigenesis at single-cell resolution. In the present review, we discuss the main topics of recent cancer studies that have implemented single-cell RNA sequencing (scRNA-seq). To study cancer cells, scRNA-seq has provided novel insights into the cancer stem-cell model, treatment resistance, and cancer metastasis. To study the tumor microenvironment, scRNA-seq has portrayed the diverse cell types and complex cellular states of both immune and non-immune cells interacting with cancer cells, with the promise to discover novel targets for future immunotherapy.

Single-cell RNA sequencing in human lung cancer: Applications, challenges, and pathway towards personalized therapy

Lung cancer is one of the most prevalent human cancers, and single-cell RNA sequencing (scRNA-seq) has been widely used to study human lung cancer at the cellular, genetic, and molecular level. Even though there are published reviews, which summarized the applications of scRNA-seq in human cancers like breast cancer, there is lack of a comprehensive review, which could effectively highlight the broad use of scRNA-seq in studying lung cancer. This review, therefore, was aimed to summarize the various applications of scRNA-seq in human lung cancer research based on the findings from different published in vitro, in vivo, and clinical studies. The review would first briefly outline the concept and principle of scRNA-seq, followed by the discussion on the applications of scRNA-seq in studying human lung cancer. Finally, the challenges faced when using scRNA-seq to study human lung cancer would be discussed, and the potential applications and challenges of scRNA-seq to facilitate the development of personalized cancer therapy in the future would be explored.

Cancer drug resistance induced by EMT: novel therapeutic strategies

Over the last decade, important clinical benefits have been achieved in cancer patients by using drug-targeting strategies. Nevertheless, drug resistance is still a major problem in most cancer therapies. Epithelial-mesenchymal plasticity (EMP) and tumour microenvironment have been described as limiting factors for effective treatment in many cancer types. Moreover, epithelial-to-mesenchymal transition (EMT) has also been associated with therapy resistance in many different preclinical models, although limited evidence has been obtained from clinical studies and clinical samples. In this review, we particularly deepen into the mechanisms of which intermediate epithelial/mesenchymal (E/M) states and its interconnection to microenvironment influence therapy resistance. We also describe how the use of bioinformatics and pharmacogenomics will help to figure out the biological impact of the EMT on drug resistance and to develop novel pharmacological approaches in the future.

NEIL3 may act as a potential prognostic biomarker for lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) is the leading cause of cancer-related death. This study aimed to develop and validate reliable prognostic biomarkers and signature.

METHODS

Differentially expressed genes were identified based on three Gene Expression Omnibus (GEO) datasets. Based on 1052 samples' data from our cohort, GEO and The Cancer Genome Atlas, we explored the relationship of clinicopathological features and NEIL3 expression to determine clinical effect of NEIL3 in LUAD. Western blotting (22 pairs of tumor and normal tissues), Real-time quantitative PCR (19 pairs of tumor and normal tissues), and immunohistochemical analyses (406-tumor tissues subjected to microarray) were conducted. TIMER and ImmuCellAI analyzed relationship between NEIL3 expression and the abundance of tumor-infiltrating immune cells in LUAD. The co-expressed-gene prognostic signature was established based on the Cox regression analysis.

RESULTS

This study identified 502 common differentially expressed genes and confirmed that NEIL3 was significantly overexpressed in LUAD samples (P < 0.001). Increased NEIL3 expression was related to advanced stage, larger tumor size and poor overall survival (p < 0.001) in three LUAD cohorts. The proportions of natural T regulatory cells and induced T regulatory cells increased in the high NEIL3 group, whereas those of B cells, Th17 cells and dendritic cells decreased. Gene set enrichment analysis indicated that NEIL3 may activate cell cycle progression and P53 signaling pathway, leading to poor outcomes. We identified nine prognosis-associated hub genes among 370 genes co-expressed with NEIL3. A 10-gene prognostic signature including NEIL3 and nine key co-expressed genes was constructed. Higher risk-score was correlated with more advanced stage, larger tumor size and worse outcome (p < 0.05). Finally, the signature was verified in test cohort (GSE50081) with superior diagnostic accuracy.

CONCLUSIONS

This study suggested that NEIL3 has the potential to be an immune-related therapeutic target and an independent predictor of LUAD prognosis. We also developed a prognostic signature for LUAD with a precise diagnostic accuracy.

Melanoma brain metastases: Biological basis and novel therapeutic strategies

The development of brain metastases is the deadliest complication of advanced melanoma and has long been associated with a dismal prognosis. The recent years have seen incredible progress in the development of therapies for melanoma brain metastases (MBM), with both targeted therapies (the BRAF-MEK inhibitor combination) and immune checkpoint inhibitors (the anti-CTLA-4, anti-PD-1 combination) showing impressive levels of activity. Despite this, durations of response for these therapies remain lower at intracranial sites of metastasis compared to extracranial metastases and it has been suggested that there are unique features of the brain microenvironment that contribute to therapeutic escape. In this review, we outline the latest research into the biology and pathophysiology of melanoma brain metastasis development and progression. We then discuss the current status of clinical trial that are open to patients with MBM and end by describing the ongoing challenges for the field.

Rapid Target Binding and Cargo Release of Activatable Liposomes Bearing HER2 and FAP Single-Chain Antibody Fragments Reveal Potentials for Image-Guided Delivery to Tumors

Liposomes represent suitable tools for the diagnosis and treatment of a variety of diseases, including cancers. To study the role of the human epidermal growth factor receptor 2 (HER2) as target in cancer imaging and image-guided deliveries, liposomes were encapsulated with an intrinsically quenched concentration of a near-infrared fluorescent dye in their aqueous interior. This resulted in quenched liposomes (termed LipQ), that were fluorescent exclusively upon degradation, dye release, and activation. The liposomes carried an always-on green fluorescent phospholipid in the lipid layer to enable tracking of intact liposomes. Additionally, they were functionalized with single-chain antibody fragments directed to fibroblast activation protein (FAP), a marker of stromal fibroblasts of most epithelial cancers, and to HER2, whose overexpression in 20–30% of all breast cancers and many other cancer types is associated with a poor treatment outcome and relapse. We show that both monospecific (HER2-IL) and bispecific (Bi-FAP/HER2-IL) formulations are quenched and undergo HER2-dependent rapid uptake and cargo release in cultured target cells and tumor models in mice. Thereby, tumor fluorescence was retained in whole-body NIRF imaging for 32–48 h post-injection. Opposed to cell culture studies, Bi-FAP/HER2-IL-based live confocal microscopy of a high HER2-expressing tumor revealed nuclear delivery of the encapsulated dye. Thus, the liposomes have potentials for image-guided nuclear delivery of therapeutics, and also for intraoperative delineation of tumors, metastasis, and tumor margins.

Site-specific metastasis: A cooperation between cancer cells and the metastatic microenvironment

The conclusion derived from the information provided in this review is that disseminating tumor cells (DTC) collaborate with the microenvironment of a future metastatic organ site in the establishment of organ‐specific metastasis. We review the basic principles of site‐specific metastasis and the contribution of the cross talk between DTC and the microenvironment of metastatic sites (metastatic microenvironment [MME]) to the establishment of the organ‐specific premetastatic niche; the targeted migration of DTC to the endothelium of the future organ‐specific metastasis; the transmigration of DTC to this site and the seeding and colonization of DTC in their future MME. We also discuss the role played by DTC‐MME interactions on tumor dormancy and on the differential response of tumor cells residing in different MMEs to antitumor therapy. Finally, we summarize some studies dealing with the effects of the MME on a unique site‐specific metastasis—brain metastasis.

The updated landscape of tumor microenvironment and drug repurposing

Accumulating evidence shows that cellular and acellular components in tumor microenvironment (TME) can reprogram tumor initiation, growth, invasion, metastasis, and response to therapies. Cancer research and treatment have switched from a cancer-centric model to a TME-centric one, considering the increasing significance of TME in cancer biology. Nonetheless, the clinical efficacy of therapeutic strategies targeting TME, especially the specific cells or pathways of TME, remains unsatisfactory. Classifying the chemopathological characteristics of TME and crosstalk among one another can greatly benefit further studies exploring effective treating methods. Herein, we present an updated image of TME with emphasis on hypoxic niche, immune microenvironment, metabolism microenvironment, acidic niche, innervated niche, and mechanical microenvironment. We then summarize conventional drugs including aspirin, celecoxib, β-adrenergic antagonist, metformin, and statin in new antitumor application. These drugs are considered as viable candidates for combination therapy due to their antitumor activity and extensive use in clinical practice. We also provide our outlook on directions and potential applications of TME theory. This review depicts a comprehensive and vivid landscape of TME from biology to treatment.

Eco-oncology: Applying ecological principles to understand and manage cancer

Cancer is a disease of single cells that expresses itself at the population level. The striking similarities between initiation and growth of tumors and dynamics of biological populations, and between metastasis and ecological invasion and community dynamics suggest that oncology can benefit from an ecological perspective to improve our understanding of cancer biology. Tumors can be viewed as complex, adaptive, and evolving systems as they are spatially and temporally heterogeneous, continually interacting with each other and with the microenvironment and evolving to increase the fitness of the cancer cells. We argue that an eco-evolutionary perspective is essential to understand cancer biology better. Furthermore, we suggest that ecologically informed therapeutic approaches that combine standard of care treatments with strategies aimed at decreasing the evolutionary potential and fitness of neoplastic cells, such as disrupting cell-to-cell communication and cooperation, and preventing successful colonization of distant organs by migrating cancer cells, may be effective in managing cancer as a chronic condition.

Inter-Tumor Heterogeneity-Melanomas Respond Differently to GM-CSF-Mediated Activation

Granulocyte-monocyte colony stimulating factor (GM-CSF) is used as an adjuvant in various clinical and preclinical studies with contradictory results. These were attributed to opposing effects of GM-CSF on the immune or myeloid systems of the treated patients or to lack of optimal dosing regimens. The results of the present study point to inter-tumor heterogeneity as a possible mechanism accounting for the contrasting responses to GM-CSF incorporating therapies. Employing xenograft models of human melanomas in nude mice developed in our lab, we detected differential functional responses of melanomas from different patients to GM-CSF both in vitro as well as in vivo. Whereas cells of one melanoma acquired pro metastatic features following exposure to GM-CSF, cells from another melanoma either did not respond or became less malignant. We propose that inter-melanoma heterogeneity as manifested by differential responses of melanoma cells (and perhaps also of other tumor) to GM-CSF may be developed into a predictive marker providing a tool to segregate melanoma patients who will benefit from GM-CSF therapy from those who will not.

Targeting the Tumor Microenvironment with Fluorescence-Activatable Bispecific Endoglin/Fibroblast Activation Protein Targeting Liposomes

Liposomes are biocompatible nanocarriers with promising features for targeted delivery of contrast agents and drugs into the tumor microenvironment, for imaging and therapy purposes. Liposome-based simultaneous targeting of tumor associated fibroblast and the vasculature is promising, but the heterogeneity of tumors entails a thorough validation of suitable markers for targeted delivery. Thus, we elucidated the potential of bispecific liposomes targeting the fibroblast activation protein (FAP) on tumor stromal fibroblasts, together with endoglin which is overexpressed on tumor neovascular cells and some neoplastic cells. Fluorescence-quenched liposomes were prepared by hydrating a lipid film with a high concentration of the self-quenching near-infrared fluorescent dye, DY-676-COOH, to enable fluorescence detection exclusively upon liposomal degradation and subsequent activation. A non-quenched green fluorescent phospholipid was embedded in the liposomal surface to fluorescence-track intact liposomes. FAP- and murine endoglin-specific single chain antibody fragments were coupled to the liposomal surface, and the liposomal potentials validated in tumor cells and mice models. The bispecific liposomes revealed strong fluorescence quenching, activatability, and selectivity for target cells and delivered the encapsulated dye selectively into tumor vessels and tumor associated fibroblasts in xenografted mice models and enabled their fluorescence imaging. Furthermore, detection of swollen lymph nodes during intra-operative simulations was possible. Thus, the bispecific liposomes have potentials for targeted delivery into the tumor microenvironment and for image-guided surgery.

Liquid Biopsy Based on Circulating Cancer-Associated Cells: Bridging the Gap from an Emerging Concept to a Mainstream Tool in Precision Medicine

The concept of liquid biopsy and the isolation and analysis of circulating biomarkers from blood samples is proposed as a surrogate to solid biopsies and can have the potential to revolutionize the management of patients with cancer. The relevance of circulating tumor cells (CTCs) and the importance of the information they carry is acknowledged by the medical community. But what are the barriers to clinical adoption? This review draws a panorama of the biological implications of CTCs, their physical and biochemical properties, and the current technological bottlenecks for their analysis in relation with the medical needs. Keys and considerations to bridge the technological and clinical gaps that still need to be overcome to be able to introduce CTCs in clinical routine are finally synthesized.

Dural Cells Release Factors Which Promote Cancer Cell Malignancy and Induce Immunosuppressive Markers in Bone Marrow Myeloid Cells

BACKGROUND

Thirty per cent of cancer patients develop spine metastases with a substantial number leading to spinal cord compression and neurological deficits. Many demonstrate a propensity toward metastasis to the posterior third of the vertebral body. The dura, the outer layer of the meninges, lies in intimate contact with the posterior border of the vertebral body and has been shown to influence adjacent bone. The effects of the dura on bone marrow and cancer cells have not been examined. Understanding the biology of spinal metastasis will provide insights into mechanisms of cancer growth and allow for new treatment strategies.

OBJECTIVE

To examine the extent to which dura influences bone marrow/tumor cell metastatic characteristics.

METHODS

Dura conditioned media (DCM) from primary dura was examined for the ability to stimulate tumor cell proliferation/invasion and to alter bone marrow cell populations. RNA sequencing of dural fibroblasts was performed to examine expression of cytokines and growth factors.

RESULTS

DCM induced a significant increase in invasion and proliferation of multiple tumor cell lines, and of patient-derived primary spinal metastatic cells. DCM also increased the proliferation of bone marrow myeloid cells, inducing expression of immunosuppressive markers. RNA sequencing of dural fibroblasts demonstrated abundant expression of cytokines and growth factors involved in cancer/immune pathways.

CONCLUSION

Factors released by primary dural cells induce proliferation of tumor cells and alter bone marrow to create a fertile environment for tumor growth. The dura therefore may play an important role in the increased incidence of metastases to adjacent bone.

Tumor-Stroma-Inflammation Networks Promote Pro-metastatic Chemokines and Aggressiveness Characteristics in Triple-Negative Breast Cancer

The tumor microenvironment (TME) plays key roles in promoting disease progression in the aggressive triple-negative subtype of breast cancer (TNBC; Basal/Basal-like). Here, we took an integrative approach and determined the impact of tumor-stroma-inflammation networks on pro-metastatic phenotypes in TNBC. With the TCGA dataset we found that the pro-inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin 1β (IL-1β), as well as their target pro-metastatic chemokines CXCL8 (IL-8), CCL2 (MCP-1), and CCL5 (RANTES) were expressed at significantly higher levels in basal patients than luminal-A patients. Then, we found that TNFα- or IL-1β-stimulated co-cultures of TNBC cells (MDA-MB-231, MDA-MB-468, BT-549) with mesenchymal stem cells (MSCs) expressed significantly higher levels of CXCL8 compared to non-stimulated co-cultures or each cell type alone, with or without cytokine stimulation. CXCL8 was also up-regulated in TNBC co-cultures with breast cancer-associated fibroblasts (CAFs) derived from patients. CCL2 and CCL5 also reached the highest expression levels in TNFα/IL-1β-stimulated TNBC:MSC/CAF co-cultures. The elevations in CXCL8 and CCL2 expression partly depended on direct physical contacts between the tumor cells and the MSCs/CAFs, whereas CCL5 up-regulation was entirely dependent on cell-to-cell contacts. Supernatants of TNFα-stimulated TNBC:MSC "Contact" co-cultures induced robust endothelial cell migration and sprouting. TNBC cells co-cultured with MSCs and TNFα gained migration-related morphology and potent migratory properties; they also became more invasive when co-cultured with MSCs/CAFs in the presence of TNFα. Using siRNA to CXCL8, we found that CXCL8 was significantly involved in mediating the pro-metastatic activities gained by TNFα-stimulated TNBC:MSC "Contact" co-cultures: angiogenesis, migration-related morphology of the tumor cells, as well as cancer cell migration and invasion. Importantly, TNFα stimulation of TNBC:MSC "Contact" co-cultures in vitro has increased the aggressiveness of the tumor cells in vivo, leading to higher incidence of mice with lung metastases than non-stimulated TNBC:MSC co-cultures. Similar tumor-stromal-inflammation networks established in-culture with luminal-A cells demonstrated less effective or differently-active pro-metastatic functions than those of TNBC cells. Overall, our studies identify novel tumor-stroma-inflammation networks that may promote TNBC aggressiveness by increasing the pro-malignancy potential of the TME and of the tumor cells themselves, and reveal key roles for CXCL8 in mediating these metastasis-promoting activities.

Regeneration Enhances Metastasis: A Novel Role for Neurovascular Signaling in Promoting Melanoma Brain Metastasis

Neural repair after stroke involves initiation of a cellular proliferative program in the form of angiogenesis, neurogenesis, and molecular growth signals in the surrounding tissue elements. This cellular environment constitutes a niche in which regeneration of new blood vessels and new neurons leads to partial tissue repair after stroke. Cancer metastasis has similar proliferative cellular events in the brain and other organs. Do cancer and CNS tissue repair share similar cellular processes? In this study, we identify a novel role of the regenerative neurovascular niche induced by stroke in promoting brain melanoma metastasis through enhancing cellular interactions with surrounding niche components. Repair-mediated neurovascular signaling induces metastatic cells to express genes crucial to metastasis. Mimicking stroke-like conditions in vitro displays an enhancement of metastatic migration potential and allows for the determination of cell-specific signals produced by the regenerative neurovascular niche. Comparative analysis of both in vitro and in vivo expression profiles reveals a major contribution of endothelial cells in mediating melanoma metastasis. These results point to a previously undiscovered role of the regenerative neurovascular niche in shaping the tumor microenvironment and brain metastatic landscape.

The role of CCR5 in directing the mobilization and biological function of CD11b+Gr1+Ly6Clow polymorphonuclear myeloid cells in cancer

Bone marrow (BM) cells of the hematopoietic system, also known as BM-derived leukocytes (BMD), are mobilized from the BM to the blood and then colonize tumor sites. These cells then become key players in either promoting or regulating the development and progression of tumors. Among the cells that suppress anti-tumor immunity are regulatory T cells (Tregs), tumor-associated macrophages (TAMS) and myeloid-derived suppressor cells (MDSC). MDSC comprise CD11b+Gr1+Ly6Clow polymorphonuclear myeloid cells (PMN-MDSC), and CD11b+Gr1+Ly6Chigh monocytic myeloid cells (Mo-MDSC). Several studies including ours have identified the CCR2-CCL2 axis as the key driver of the mobilization of monocytic cells from the BM to the blood and later their colonization at the tumor site. The current review focuses on the mechanisms by which PMN-MDSC are mobilized from the BM to the blood and later to the tumor site, and their clinical implications.

Cancer- and behavior-related genes are targeted by selection in the Tasmanian devil (Sarcophilus harrisii)

Devil Facial Tumor Disease (DFTD) is an aggressive cancer notorious for its rare etiology and its impact on Tasmanian devil populations. Two regions underlying an evolutionary response to this cancer were recently identified using genomic time-series pre- and post-DTFD arrival. Here, we support that DFTD shaped the genome of the Tasmanian devil in an even more extensive way than previously reported. We detected 97 signatures of selection, including 148 protein coding genes having a human orthologue, linked to DFTD. Most candidate genes are associated with cancer progression, and an important subset of candidate genes has additional influence on social behavior. This confirms the influence of cancer on the ecology and evolution of the Tasmanian devil. Our work also demonstrates the possibility to detect highly polygenic footprints of short-term selection in very small populations.

An insight into metastasis: Random or evolving paradigms?

Mechanical or fostered molecular events define metastatic cascade. Three distinct sets of molecular events characterize metastasis, viz invasion of extracellular matrix; angiogenesis, vascular dissemination and anoikis resistance; tumor homing and relocation of tumor cells to selective organ. Invasion of extracellular matrix requires epithelial to mesenchymal transition through disrupted lamellopodia formation and contraction of actin cytoskeleton; aberration of Focal adhesion complex formation involving integrins and the extracellular matrix; degradation of extracellular matrix by matrix metalloproteases; faulty immune surveillance in tumor microenvironment and an upregulated proton efflux pump NHE1 in tumors. Vascular dissemination and anoikis resistance depend upon upregulation of integrins, phosphorylation of CDCP1, attenuated apoptotic pathways and upregulation of angiogenesis. Tumor homing depends on recruitment of mesenchymal stem cells, expression on chemokines and growth factors, upregulated stem cell renewal pathways. Despite of many potential challenges in curbing metastasis, future targeted therapies involving immunotherapy, stem cell engineered and oncolytic virus based therapy, pharmacological activation of circadian clock are held promising. To sum up, metastasis is a complex cascade of events and warrants detailed molecular understanding for development of therapeutic strategies.

A history of exploring cancer in context

The concept that progression of cancer is regulated by interactions of cancer cells with their microenvironment was postulated by Stephen Paget over a century ago. Contemporary tumour microenvironment (TME) research focuses on the identification of tumour-interacting microenvironmental constituents, such as resident or infiltrating non-tumour cells, soluble factors and extracellular matrix components, and the large variety of mechanisms by which these constituents regulate and shape the malignant phenotype of tumour cells. In this Timeline article, we review the developmental phases of the TME paradigm since its initial description. While illuminating controversies, we discuss the importance of interactions between various microenvironmental components and tumour cells and provide an overview and assessment of therapeutic opportunities and modalities by which the TME can be targeted.

Curcumin exerts its antitumor effects in a context dependent fashion

Proteome profiling profoundly contributes to the understanding of cell response mechanisms to drug actions. Such knowledge may become a key to improve personalized medicine. In the present study, the effects of the natural remedy curcumin on breast cancer model systems were investigated. MCF-7, ZR-75-1 and TGF-β1 pretreated fibroblasts, mimicking cancer-associated fibroblasts (CAFs), were treated independently as well as in tumor cell/CAF co-cultures. Remarkably, co-culturing with CAF-like cells (CLCs) induced different proteome alterations in MCF-7 and ZR-75-1 cells, respectively. Curcumin significantly induced HMOX1 in single cell type models and co-cultures. However, other curcumin effects differed. In the MCF-7/CLC co-culture, curcumin significantly down-regulated RC3H1, a repressor of inflammatory signaling. In the ZR-75-1/CLC co-culture, curcumin significantly down-regulated PEG10, an anti-apoptotic protein, and induced RRAGA, a pro-apoptotic protein involved in TNF-alpha signaling. Furthermore, curcumin induced AKR1C2, an important enzyme for progesterone metabolism. None of these specific curcumin effects were observed in single cell type cultures. All high-resolution mass spectrometry data are available via ProteomeXchange with the identifier PXD008719. The present data demonstrate that curcumin induces proteome alterations, potentially accounting for its known antitumor effects, in a strongly context-dependent fashion.

BIOLOGICAL SIGNIFICANCE

Better means to understand and potentially predict individual variations of drug effects are urgently required. The present proteome profiling study of curcumin effects demonstrates the massive impact of the cell microenvironment on cell responses to drug action. Co-culture models apparently provide more biologically relevant information regarding curcumin effects than single cell type cultures.

Cystatin C takes part in melanoma-microglia cross-talk: possible implications for brain metastasis

The development of melanoma brain metastasis is largely dependent on mutual interactions between the melanoma cells and cells in the brain microenvironment. Here, we report that the extracellular cysteine protease inhibitor cystatin C (CysC) is involved in these interactions. Microglia-derived factors upregulated CysC secretion by melanoma. Similarly, melanoma-derived factors upregulated CysC secretion by microglia. Whereas CysC enhanced melanoma cell migration through a layer of brain endothelial cells, it inhibited the migration of microglia cells toward melanoma cells. CysC was also found to promote the formation of melanoma three-dimensional structures in matrigel. IHC analysis revealed increased expression levels of CysC in the brain of immune-deficient mice bearing xenografted human melanoma brain metastasis compared to the brain of control mice. Based on these in vitro and in vivo experiments we hypothesize that CysC promotes melanoma brain metastasis. Increased expression levels of CysC were detected in the regenerating brain of mice after stroke. Post-stroke brain with melanoma brain metastasis showed an even stronger expression of CysC. The in vitro induction of stroke-like conditions in brain microenvironmental cells increased the levels of CysC in the secretome of microglia cells, but not in the secretome of brain endothelial cells. The similarities between melanoma brain metastasis and stroke with respect to CysC expression by and secretion from microglia cells suggest that CysC may be involved in shared pathways between brain metastasis and post-stroke regeneration. This manifests the tendency of tumor cells to highjack physiological molecular pathways in their progression.

CCR4 is a determinant of melanoma brain metastasis

We previously identified the chemokine receptor CCR4 as part of the molecular signature of melanoma brain metastasis. The aim of this study was to determine the functional significance of CCR4 in melanoma brain metastasis. We show that CCR4 is more highly expressed by brain metastasizing melanoma cells than by local cutaneous cells from the same melanoma. Moreover, we found that the expression of CCR4 is significantly higher in paired clinical specimens of melanoma metastases than in samples of primary tumors from the same patients. Notably, the expression of the CCR4 ligands, Ccl22 and Ccl17 is upregulated at the earliest stages of brain metastasis, and precedes the infiltration of melanoma cells to the brain. In-vitro, CCL17 induced migration and transendothelial migration of melanoma cells. Functionally, human melanoma cells over-expressing CCR4 were more tumorigenic and produced a higher load of spontaneous brain micrometastasis than control cells. Blocking CCR4 with a small molecule CCR4 antagonist in-vivo, reduced the tumorigenicity and micrometastasis formation of melanoma cells. Taken together, these findings implicate CCR4 as a driver of melanoma brain metastasis.

Organ-specific isogenic metastatic breast cancer cell lines exhibit distinct Raman spectral signatures and metabolomes

Molecular characterization of organ-specific metastatic lesions, which distinguish them from the primary tumor, will provide a better understanding of tissue specific adaptations that regulate metastatic progression. Using an orthotopic xenograft model, we have isolated isogenic metastatic human breast cancer cell lines directly from organ explants that are phenotypically distinct from the primary tumor cell line. Label-free Raman spectroscopy was used and informative spectral bands were ascertained as differentiators of organ-specific metastases as opposed to the presence of a single universal marker. Decision algorithms derived from the Raman spectra unambiguously identified these isogenic cell lines as unique biological entities – a finding reinforced through metabolomic analyses that indicated tissue of origin metabolite distinctions between the cell lines. Notably, complementarity of the metabolomics and Raman datasets was found. Our findings provide evidence that metastatic spread generates tissue-specific adaptations at the molecular level within cancer cells, which can be differentiated with Raman spectroscopy.

Combinatorial Discovery of Defined Substrates That Promote a Stem Cell State in Malignant Melanoma

The tumor microenvironment is implicated in orchestrating cancer cell transformation and metastasis. However, specific cell-ligand interactions between cancer cells and the extracellular matrix are difficult to decipher due to a dynamic and multivariate presentation of many signaling molecules. Here we report a versatile peptide microarray platform that is capable of screening for cancer cell phenotypic changes in response to ligand-receptor interactions. Using a screen of 78 peptide combinations derived from proteins present in the melanoma microenvironment, we identify a proteoglycan binding and bone morphogenic protein 7 (BMP7) derived sequence that selectively promotes the expression of several putative melanoma initiating cell markers. We characterize signaling associated with each of these peptides in the activation of melanoma pro-tumorigenic signaling and reveal a role for proteoglycan mediated adhesion and signaling through Smad 2/3. A defined substratum that controls the state of malignant melanoma may prove useful in spatially normalizing a heterogeneous population of tumor cells for discovery of therapeutics that target a specific state and for identifying new drug targets and reagents for intervention.

PHOX2B is a suppressor of neuroblastoma metastasis

Paired like homeobox 2B (PHOX2B) is a minimal residual disease (MRD) marker of neuroblastoma. The presence of MRD, also referred to as micro-metastases, is a powerful marker of poor prognosis in neuroblastoma.

Lung metastasis is considered a terminal event in neuroblastoma. Lung micro-metastatic neuroblastoma (MicroNB) cells show high expression levels of PHOX2B and possess a less malignant and metastatic phenotype than lung macro metastatic neuroblastoma (MacroNB) cells, which hardly express PHOX2B.

In vitro assays showed that PHOX2B knockdown in MicroNB cells did not affect cell viability; however it decreased the migratory capacity of the MicroNB-shPHOX2B cells. An orthotopic inoculation of MicroNB-shPHOX2B cells into the adrenal gland of nude mice resulted in significantly larger primary tumors and a heavier micro-metastatic load in the lungs and bone-marrow, than when control cells were inoculated.

PHOX2B expression was found to be regulated by methylation. The PHOX2B promoter in MacroNB cells is significantly more methylated than in MicroNB cells. Demethylation assays using 5-azacytidine demonstrated that methylation can indeed inhibit PHOX2B transcription in MacroNB cells.

These pre-clinical data strongly suggest that PHOX2B functions as a suppressor of neuroblastoma progression.

The Beta Subunit of Hemoglobin (HBB2/HBB) Suppresses Neuroblastoma Growth and Metastasis

Soluble pulmonary factors have been reported to be capable of inhibiting the viability of cancer cells that metastasize to the lung, but the molecular identity was obscure. Here we report the isolation and characterization of the beta subunit of hemoglobin as a lung-derived antimetastatic factor. Peptide mapping in the beta subunit of human hemoglobin (HBB) defined a short C-terminal region (termed Metox) as responsible for activity. In tissue culture, both HBB and murine HBB2 mediated growth arrest and apoptosis of lung-metastasizing neuroblastoma cells, along with a variety of other human cancer cell lines. Metox acted similarly and its administration in human tumor xenograft models limited the development of adrenal neuroblastoma tumors as well as spontaneous lung and bone marrow metastases. Expression studies in mice indicated that HBB2 is produced by alveolar epithelial and endothelial cells and is upregulated in mice bearing undetectable metastasis. Our work suggested a novel function for HBB as a theranostic molecule: an innate antimetastasis factor with potential utility as an anticancer drug and a biomarker signaling the presence of clinically undetectable metastasis. Cancer Res; 77(1); 14-26. ©2016 AACR.

Melanoma Brain Metastasis: Mechanisms, Models, and Medicine

The development of brain metastases in patients with advanced stage melanoma is common, but the molecular mechanisms responsible for their development are poorly understood. Melanoma brain metastases cause significant morbidity and mortality and confer a poor prognosis; traditional therapies including whole brain radiation, stereotactic radiotherapy, or chemotherapy yield only modest increases in overall survival (OS) for these patients. While recently approved therapies have significantly improved OS in melanoma patients, only a small number of studies have investigated their efficacy in patients with brain metastases. Preliminary data suggest that some responses have been observed in intracranial lesions, which has sparked new clinical trials designed to evaluate the efficacy in melanoma patients with brain metastases. Simultaneously, recent advances in our understanding of the mechanisms of melanoma cell dissemination to the brain have revealed novel and potentially therapeutic targets. In this review, we provide an overview of newly discovered mechanisms of melanoma spread to the brain, discuss preclinical models that are being used to further our understanding of this deadly disease and provide an update of the current clinical trials for melanoma patients with brain metastases.

Tumor-associated fibroblasts predominantly come from local and not circulating precursors

Fibroblasts are common cell types in cancer stroma and lay down collagen required for survival and growth of cancer cells. Although some cancer therapy strategies target tumor fibroblasts, their origin remains controversial. Multiple publications suggest circulating mesenchymal precursors as a source of tumor-associated fibroblasts. However, we show by three independent approaches that tumor fibroblasts derive primarily from local, sessile precursors. First, transplantable tumors developing in a mouse expressing green fluorescent reporter protein (EGFP) under control of the type I collagen (Col-I) promoter (COL-EGFP) had green stroma, whereas we could not find COL-EGFP(+) cells in tumors developing in the parabiotic partner lacking the fluorescent reporter. Lack of incorporation of COL-EGFP(+) cells from the circulation into tumors was confirmed in parabiotic pairs of COL-EGFP mice and transgenic mice developing autochthonous intestinal adenomas. Second, transplantable tumors developing in chimeric mice reconstituted with bone marrow cells from COL-EGFP mice very rarely showed stromal fibroblasts expressing EGFP. Finally, cancer cells injected under full-thickness COL-EGFP skin grafts transplanted in nonreporter mice developed into tumors containing green stromal cells. Using multicolor in vivo confocal microscopy, we found that Col-I-expressing fibroblasts constituted approximately one-third of the stromal mass and formed a continuous sheet wrapping the tumor vessels. In summary, tumors form their fibroblastic stroma predominantly from precursors present in the local tumor microenvironment, whereas the contribution of bone marrow-derived circulating precursors is rare.

Low-fidelity alternative DNA repair carcinogenesis theory may interpret many cancer features and anticancer strategies

We have proposed that the low-fidelity compensatory backup alternative DNA repair pathways drive multistep carcinogenesis. Here, we apply it to interpret the clinical features of cancer, such as mutator phenotype, tissue specificity, age specificity, diverse types of cancers originated from the same type of tissue, cancer susceptibility of patients with DNA repair-defective syndromes, development of cancer only for a selected number of individuals among those that share the same genetic defect, invasion and metastasis. Clinically, the theory predicts that to improve the efficacy of molecular targeted or synthetic lethal therapy, it may be crucial to inhibit the low-fidelity compensatory alternative DNA repair either directly or by blocking the signal transducers of the sustained microenvironmental stress.

Hexokinase 2 is a determinant of neuroblastoma metastasis

Background:

Intersecting a genome-wide expression profile of metastatic and nonmetastatic human neuroblastoma xenograft variants with expression profiles of tumours from stage 1 and 4 neuroblastoma patients, we previously characterised hexokinase 2 (HK2) as a gene whose expression was upregulated in both metastatic neuroblastoma variants and tumours from stage 4 neuroblastoma patients.

Methods:

Local and metastatic neuroblastoma cell variants as well as metastatic neuroblastoma cells genetically manipulated to downregulate the expression of HK2 were utilised for in vitro and in vivo examinations of the involvement of HK2 in neuroblastoma.

Results:

Hexokinase 2 expression and its activity levels were increased in neuroblastoma metastatic variants as compared with the local variants. The upregulation of HK2 confers upon the metastatic cells high resistance to the antiproliferative effect of the HK2 inhibitor 3-BrPa and to the chemotherapy agent Deferoxamine. The inhibition of HK2 transcript lowered the proliferation and motility of sh-HK2 cells as compared with sh-control cells. Mice that were inoculated with sh-HK2 cells had a lower incidence of local tumours, smaller tumour volumes and a diminished load of lung metastasis compared with mice inoculated with sh-control cells.

Conclusions:

Hexokinase 2 plays a significant role in shaping the malignant phenotype of neuroblastoma and influences the progression of this disease.

Potential of activatable FAP-targeting immunoliposomes in intraoperative imaging of spontaneous metastases

Despite intensive research and medical advances met, metastatic disease remains the most common cause of death in cancer patients. This results from late diagnosis, poor therapeutic response and undetected micrometastases and tumor margins during surgery. One approach to overcome these challenges involves fluorescence imaging, which exploits the properties of fluorescent probes for diagnostic detection of molecular structures at the onset of transformation and for intraoperative detection of metastases and tumor margins in real time. Considering these benefits, many contrast agents suitable for fluorescence imaging have been reported. However, most reports only demonstrate the detection of primary tumors and not the detection of metastases or their application in models of image-guided surgery. In this work, we demonstrate the influence of fibroblast activation protein (FAP) on the metastatic potential of fibrosarcoma cells and elucidate the efficacy of activatable FAP-targeting immunoliposomes (FAP-IL) for image-guided detection of the spontaneous metastases in mice models. Furthermore, we characterized the biodistribution and cellular localization of the liposomal fluorescent components in mice organs and traced their excretion over time in urine and feces. Taken together, activatable FAP-IL enhances intraoperative imaging of metastases. Their high accumulation in metastases, subsequent localization in the bile canaliculi and liver kupffer cells and suitable excretion in feces substantiates their potency as contrast agents for intraoperative imaging.

Epigenomic landscape of melanoma progression to brain metastasis: unexplored therapeutic alternatives

Melanoma brain metastasis is a complication with rising incidence. Despite the high rate of somatic mutations driving the initial stages of melanocyte transformation, the brain colonization requires a phenotypic reprogramming that is, in part, influenced by epigenomic modifications. This special report summarizes recent findings in the epigenomic landscape of melanoma progression to brain metastasis, with particular emphasis on the clinical utility of DNA methylation, chromatin modifications and ncRNA expression as theragnostic markers, as well as the significance of the metastatic microenvironment on melanoma brain metastasis epigenome.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

Vemurafenib resistance selects for highly malignant brain and lung-metastasizing melanoma cells

V600E being the most common mutation in BRAF, leads to constitutive activation of the MAPK signaling pathway. The majority of V600E BRAF positive melanoma patients treated with the BRAF inhibitor vemurafenib showed initial good clinical responses but relapsed due to acquired resistance to the drug. The aim of the present study was to identify possible biomarkers associated with the emergence of drug resistant melanoma cells. To this end we analyzed the differential gene expression of vemurafenib-sensitive and vemurafenib resistant brain and lung metastasizing melanoma cells. The major finding of this study is that the in vitro induction of vemurafenib resistance in melanoma cells is associated with an increased malignancy phenotype of these cells. Resistant cells expressed higher levels of genes coding for cancer stem cell markers (JARID1B, CD271 and Fibronectin) as well as genes involved in drug resistance (ABCG2), cell invasion and promotion of metastasis (MMP-1 and MMP-2). We also showed that drug-resistant melanoma cells adhere better to and transmigrate more efficiently through lung endothelial cells than drug-sensitive cells. The former cells also alter their microenvironment in a different manner from that of drug-sensitive cells. Biomarkers and molecular mechanisms associated with drug resistance may serve as targets for therapy of drug-resistant cancer.

Endothelial-mesenchymal transition in normal human esophageal endothelial cells cocultured with esophageal adenocarcinoma cells: role of IL-1β and TGF-β2

Endothelial-mesenchymal transition (EndoMT) has been recognized as a key determinant of tumor microenvironment in cancer progression and metastasis. Endothelial cells undergoing EndoMT lose their endothelial markers, acquire the mesenchymal phenotype, and become more invasive with increased migratory abilities. Early stages of esophageal adenocarcinoma (EAC) are characterized by strong microvasculature whose impact in tumor progression remains undefined. Our aim was to determine the role of EndoMT in EAC by investigating the impact of tumor cells on normal primary human esophageal microvascular endothelial cells (HEMEC). HEMEC were either cocultured with OE33 adenocarcinoma cells or treated with IL-1β and transforming growth factor-β2 (TGF-β2) for indicated periods and analyzed for EndoMT-associated changes by real-time PCR, Western blotting, immunofluorescence staining, and functional assays. Additionally, human EAC tissues were investigated for detection of EndoMT-like cells. Our results demonstrate an increased expression of mesenchymal markers [fibroblast-specific protein 1 (FSP1), collagen1α2, vimentin, α-smooth muscle actin (α-SMA), and Snail], decreased expression of endothelial markers [CD31, von Willebrand factor VIII (vWF), and VE-cadherin], and elevated migration ability in HEMEC following coculture with OE33 cells. The EndoMT-related changes were inhibited by IL-1β and TGF-β2 gene silencing in OE33 cells. Recombinant IL-1β and TGF-β2 induced EndoMT in HEMEC. Although the level of VEGF expression was elevated in EndoMT cells, the angiogenic property of these cells was diminished. In vivo, by immunostaining EndoMT-like cells were detected at the invasive front of EAC. Our findings underscore a significant role for EndoMT in EAC and provide new insights into the mechanisms and significance of EndoMT in the context of tumor progression.

Biological resonance for cancer metastasis, a new hypothesis based on comparisons between primary cancers and metastases

Many hypotheses have been proposed to try to explain cancer metastasis. However, they seem to be contradictory and have some limitations. Comparisons of primary tumors and matched metastases provide new insight into metastasis. The results show high concordances and minor differences at multiple scales from organic level to molecular level. The concordances reflect the commonality between primary cancer and metastasis, and also mean that metastatic cancer cells derived from primary cancer are quite conservative in distant sites. The differences reflect variation that cancer cells must acquire new traits to adapt to foreign milieu during the course of evolving into a new tumor in second organs. These comparisons also provided new information on understanding mechanism of vascular metastasis, organ-specific metastasis, and tumor dormancy. The collective results suggest a new hypothesis, biological resonance (bio-resonance) model. The hypothesis has two aspects. One is that primary cancer and matched metastasis have a common progenitor. The other is that both ancestors of primary cancer cells and metastatic cancer cells are under similar microenvironments and receive similar or same signals. When their interactions reach a status similar to primary cancer, metastasis will occur. Compared with previous hypotheses, the bio-resonance hypothesis seems to be more applicable for cancer metastasis to explain how, when and where metastasis occurs. Thus, it has important implications for individual prediction, prevention and treatment of cancer metastasis.