Intratumoral Cancer Cell Intravasation Can Occur Independent of Invasion into the Adjacent Stroma

Tumor-Targeted Perfluorinated Micelles as Efficient Theranostic Agents Combining Positron Emission Tomography and Radiosensitization

We report the synthesis of biocompatible perfluorinated micelles designed to improve radiotherapeutic efficacy in a radioresistant tumor environment. In vitro and in vivo behaviors of perfluorinated micelles were assessed at both cellular and tissular levels. The micellar platform offers key advantages as theranostic tool: (i) small size, allowing deep tissue penetration; (ii) oxygen transport to hypoxic tissues; (iii) negligible toxicity in the absence of ionizing radiation; (iv) internalization into cancer cells; (v) potent radiosensitizing effect; and (vi) excellent tumor-targeting properties, as monitored by positron emission tomography. We have demonstrated strong in vitro radiosensitizing effects of the micelle and in vivo tumor targeting, making this nanometric carrier a promising tool for the potentiation of focused radiotherapy.

ctDNA as a novel and promising approach for cancer diagnosis: a focus on hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most prevalent forms of cancer worldwide. Therefore, it is essential to diagnose and treat HCC patients promptly. As a novel discovery, circulating tumor DNA (ctDNA) can be used to analyze the tumor type and the cancer location. Additionally, ctDNA assists the cancer stage determination, which enables medical professionals to provide patients with the most appropriate treatment. This review will discuss the HCC-related mutated genes diagnosed by ctDNA. In addition, we will introduce the different and the most appropriate ctDNA diagnosis approaches based on the facilities.

Immunotherapy in Prostate Cancer: State of Art and New Therapeutic Perspectives

Prostate cancer (PC) is the most common type of tumor in men. In the early stage of the disease, it is sensitive to androgen deprivation therapy. In patients with metastatic castration-sensitive prostate cancer (mHSPC), chemotherapy and second-generation androgen receptor therapy have led to increased survival. However, despite advances in the management of mHSPC, castration resistance is unavoidable and many patients develop metastatic castration-resistant disease (mCRPC). In the past few decades, immunotherapy has dramatically changed the oncology landscape and has increased the survival rate of many types of cancer. However, immunotherapy in prostate cancer has not yet given the revolutionary results it has in other types of tumors. Research into new treatments is very important for patients with mCRPC because of its poor prognosis. In this review, we focus on the reasons for the apparent intrinsic resistance of prostate cancer to immunotherapy, the possibilities for overcoming this resistance, and the clinical evidence and new therapeutic perspectives regarding immunotherapy in prostate cancer with a look toward the future.

Fundamentals of Bowel Cancer for Biomedical Engineers

Bowel cancer is a multifactorial disease arising from a combination of genetic predisposition and environmental factors. Detection of bowel cancer and its precursor lesions is predominantly performed by either visual inspection of the colonic mucosa during endoscopy or cross-sectional imaging. Most cases are diagnosed when the cancer is already at an advanced stage. These modalities are less reliable for detecting lesions at the earliest stages, when they are typically small or flat. Removal of lesions at the earliest possible stage reduces the risk of cancer death, which is largely due to a reduced risk of subsequent metastasis. In this review, we summarised the origin of bowel cancer and the mechanism of its metastasis. In particular, we reviewed a broad spectrum of literatures covering the biomechanics of bowel cancer and its measurement techniques that are pertinent to the successful development of a bowel cancer diagnostic device. We also reviewed existing bowel cancer diagnostic techniques that are available for clinical use. Finally, we outlined current clinical needs and highlighted the potential roles of medical robotics on early bowel cancer diagnosis.

Metastasis from the tumor interior and necrotic core formation are regulated by breast cancer-derived angiopoietin-like 7

Necrosis in the tumor interior is a common feature of aggressive cancers that is associated with poor clinical prognosis and the development of metastasis. How the necrotic core promotes metastasis remains unclear. Here, we report that emergence of necrosis inside the tumor is correlated temporally with increased tumor dissemination in a rat breast cancer model and in human breast cancer patients. By performing spatially focused transcriptional profiling, we identified angiopoietin-like 7 (Angptl7) as a tumor-specific factor localized to the perinecrotic zone. Functional studies showed that Angptl7 loss normalizes central necrosis, perinecrotic dilated vessels, metastasis, and reduces circulating tumor cell counts to nearly zero. Mechanistically, Angptl7 promotes vascular permeability and supports vascular remodeling in the perinecrotic zone. Taken together, these findings show that breast tumors actively produce factors controlling central necrosis formation and metastatic dissemination from the tumor core.

A Lamb1Dendra2 mouse model identifies basement-membrane-producing origins and dynamics in PyMT breast tumors

The basement membrane (BM) around tumor lobes forms a barrier to prevent cancer cells from invading the surrounding tissue. Although myoepithelial cells are key producers of the healthy mammary epithelium BM, they are nearly absent in mammary tumors. To study the origin and dynamics of the BM, we developed and imaged a laminin beta1-Dendra2 mouse model. We show that the turnover of laminin beta1 is faster in the BMs that surround the tumor lobes than in the BMs that surround the healthy epithelium. Moreover, we find that epithelial cancer cells and tumor-infiltrating endothelial cells synthesize laminin beta1 and that this production is temporarily and locally heterogeneous, leading to local discontinuity of the BM laminin beta1. Collectively, our data draw a new paradigm for tumor BM turnover in which the disassembly happens at a constant rate, and a local misbalance of compensating production leads to reduction or even complete disappearance of the BM.

Molecular aspects of brain metastases in breast cancer

Brain metastases (BM) are a common and devastating manifestation of breast cancer (BC). BM are particularly frequent in the HER2-positive and triple-negative breast cancer phenotypes and usually occur following the metastatic spread to extracranial sites. Several genes mediating BM and biomarkers predicting their risk in BC have been reported in the past decade. These findings have advanced the understanding of BM pathobiology and paved the way for developing new therapeutic strategies but they still warrant a thorough clinical validation. Hence, a better understanding of the mechanistic aspects of BM and delineating the interactions of tumor cells with the brain microenvironment are of utmost importance. This review discusses the molecular basis of the metastatic cascade: the epithelial-mesenchymal transition, cancer, and tumor microenvironment interaction and intravasation, priming of the metastatic niche in the brain, and survival in the new site. We also outline the postulated mechanisms of BC cells' brain tropism. Finally, we discuss advances in the field of biomarkers (both tissue-based and liquid-based) that predict BM from BC.

Intravital imaging of Wnt/β-catenin and ATF2-dependent signalling pathways during tumour cell invasion and metastasis

Wnt signalling has been implicated as a driver of tumour cell metastasis, but less is known about which branches of Wnt signalling are involved and when they act in the metastatic cascade. Here, using a unique intravital imaging platform and fluorescent reporters, we visualised β-catenin/TCF-dependent and ATF2-dependent signalling activities during human cancer cell invasion, intravasation and metastatic lesion formation in the chick embryo host. We found that cancer cells readily shifted between states of low and high canonical Wnt activity. Cancer cells that displayed low Wnt canonical activity showed higher invasion and intravasation potential in primary tumours and in metastatic lesions. In contrast, cancer cells showing low ATF2-dependent activity were significantly less invasive both at the front of primary tumours and in metastatic lesions. Simultaneous visualisation of both these reporters using a double-reporter cell line confirmed their complementary activities in primary tumours and metastatic lesions. These findings might inform the development of therapies that target different branches of Wnt signalling at specific stages of metastasis.

Orchestration of Collective Migration and Metastasis by Tumor Cell Clusters

Metastatic dissemination has lethal consequences for cancer patients. Accruing evidence supports the hypothesis that tumor cells can migrate and metastasize as clusters of cells while maintaining contacts with one another. Collective metastasis enables tumor cells to colonize secondary sites more efficiently, resist cell death, and evade the immune system. On the other hand, tumor cell clusters face unique challenges for dissemination particularly during systemic dissemination. Here, we review recent progress toward understanding how tumor cell clusters overcome these disadvantages as well as mechanisms they utilize to gain advantages throughout the metastatic process. We consider useful models for studying collective metastasis and reflect on how the study of collective metastasis suggests new opportunities for eradicating and preventing metastatic disease.

Intravital imaging to study cancer progression and metastasis

Navigation through the bulk tumour, entry into the blood vasculature, survival in the circulation, exit at distant sites and resumption of proliferation are all steps necessary for tumour cells to successfully metastasize. The ability of tumour cells to complete these steps is highly dependent on the timing and sequence of the interactions that these cells have with the tumour microenvironment (TME), including stromal cells, the extracellular matrix and soluble factors. The TME thus plays a major role in determining the overall metastatic phenotype of tumours. The complexity and cause-and-effect dynamics of the TME cannot currently be recapitulated in vitro or inferred from studies of fixed tissue, and are best studied in vivo, in real time and at single-cell resolution. Intravital imaging (IVI) offers these capabilities, and recent years have been a time of immense growth and innovation in the field. Here we review some of the recent advances in IVI of mammalian models of cancer and describe how IVI is being used to understand cancer progression and metastasis, and to develop novel treatments and therapies. We describe new techniques that allow access to a range of tissue and cancer types, novel fluorescent reporters and biosensors that allow fate mapping and the probing of functional and phenotypic states, and the clinical applications that have arisen from applying these techniques, reporters and biosensors to study cancer. We finish by presenting some of the challenges that remain in the field, how to address them and future perspectives.

Bridging the In Vitro to In Vivo gap: Using the Chick Embryo Model to Accelerate Nanoparticle Validation and Qualification for In Vivo studies

We postulate that nanoparticles (NPs) for use in therapeutic applications have largely not realized their clinical potential due to an overall inability to use in vitro results to predict NP performance in vivo. The avian embryo and associated chorioallantoic membrane (CAM) has emerged as an in vivo preclinical model that bridges the gap between in vitro and in vivo, enabling rapid screening of NP behavior under physiologically relevant conditions and providing a rapid, accessible, economical, and more ethical means of qualifying nanoparticles for in vivo use. The CAM is highly vascularized and mimics the diverging/converging vasculature of the liver, spleen, and lungs that serve as nanoparticle traps. Intravital imaging of fluorescently labeled NPs injected into the CAM vasculature enables immediate assessment and quantification of nano-bio interactions at the individual NP scale in any tissue of interest that is perfused with a microvasculature. In this review, we highlight how utilization of the avian embryo and its CAM as a preclinical model can be used to understand NP stability in blood and tissues, extravasation, biocompatibility, and NP distribution over time, thereby serving to identify a subset of NPs with the requisite stability and performance to introduce into rodent models and enabling the development of structure-property relationships and NP optimization without the sacrifice of large populations of mice or other rodents. We then review how the chicken embryo and CAM model systems have been used to accelerate the development of NP delivery and imaging agents by allowing direct visualization of targeted (active) and nontargeted (passive) NP binding, internalization, and cargo delivery to individual cells (of relevance for the treatment of leukemia and metastatic cancer) and cellular ensembles (e.g., cancer xenografts of interest for treatment or imaging of cancer tumors). We conclude by showcasing emerging techniques for the utilization of the CAM in future nano-bio studies.

Tumor Necrosis Factor-α (TNFα) Stimulate Triple-Negative Breast Cancer Stem Cells to Promote Intratumoral Invasion and Neovasculogenesis in the Liver of a Xenograft Model

TNBC represents the most aggressive breast cancer subtype. Although cancer stem cells (CSCs) are a minor fraction of all cancer cells, they are highly cancerous when compared to their non-stem counterparts, playing a major role in tumor recurrence and metastasis. Angiogenic stimuli and the tumor environment response are vital factors in cancer metastasis. However, the causes and effects of tumor angiogenesis are still poorly understood. In this study, we demonstrate TNFα effects on primary triple-negative breast cancer stem cells (BCSCs). TNFα stimulation increased the mesenchymality of BCSCs in an intermediate epithelial-to-mesenchymal transition (EMT) state, enhanced proliferation, self-renewal, and invasive capacity. TNFα-treatment elicited BCSC signaling on endothelial networks in vitro and increased the network forming capacity of the endothelial cells. Our findings further demonstrate that TNFα stimulation in BCSCs has the ability to instigate distinct cellular communication within the tumor microenvironment, inducing intra-tumoral stromal invasion. Further, TNFα-treatment in BCSCs induced a pre-metastatic niche through breast-liver organ crosstalk by inducing vascular cell adhesion molecule-1 (VCAM-1) enriched neovasculogenesis in the liver of tumor-bearing mice. Overall, TNFα is an important angiogenic target to be considered in breast cancer progression to attenuate any angiogenic response in the tumor environment that could lead to secondary organ metastasis.

A Novel Detection Method of Breast Cancer through a Simple Panel of Biomarkers

Circulating tumor cells (CTCs) have been identified as responsible for the spread of tumors to other organs of the body. In this sense, the development of sensitive and specific assays for their detection is important to reduce the number of deaths due to metastases. Here, we assessed whether the detection of CTCs in peripheral blood can serve in the construction of a panel of diagnosis and monitoring treatments of breast cancer (BC), focusing on the expression of markers of epithelial-mesenchymal transition. Through analyzing the blood from women without breast alterations (control), women with benign alterations, women with breast cancer without chemotherapy, and women with breast cancer with chemotherapy, we identified the best markers by transcriptional levels and determined three profiles of CTCs (mesenchymal, intermediate, and epithelial) by flow cytometry which, combined, can be used for diagnosis and therapy monitoring with sensitivity and specificity between 80% and 100%. Therefore, we have developed a method for detecting breast cancer based on the analysis of CTC profiles by epithelial-mesenchymal transition markers which, combined, can be used for the diagnosis and monitoring of therapy.

The overall process of metastasis: From initiation to a new tumor

Metastasis-a process that involves the migration of cells from the primary site to distant organs-is the leading cause of cancer-associated death. Improved technology and in-depth research on tumors have furthered our understanding of the various mechanisms involved in tumor metastasis. Metastasis is initiated by cancer cells of a specific phenotype, which migrate with the assistance of extracellular components and metastatic traits conferred via epigenetic regulation while modifying their behavior in response to the complex and dynamic human internal environment. In this review, we have summarized the general steps involved in tumor metastasis and their characteristics, incorporating recent studies and topical issues, including epithelial-mesenchymal transition, cancer stem cells, neutrophil extracellular traps, pre-metastatic niche, extracellular vesicles, and dormancy. Several feasible treatment directions have also been summarized. In addition, the correlation between cancer metastasis and lifestyle factors, such as obesity and circadian rhythm, has been illustrated.

Hemangiosis carcinomatosa as an independent risk factor for long-term survival in Non-Small Cell Lung Cancer patients

OBJECTIVES

Recent studies have shown that blood vessel invasion (V1) influences the long-term survival of patients with Non-Small Cell Lung Cancer (NSCLC). The aim of the present study was to emphasize V1 as an independent risk factor. We evaluated the effects of V1 on the survival of NSCLC patients with UICC stages I, II, and III after surgery.

METHODS

This retrospective study includes 747 consecutive patients with NSCLC who underwent anatomic resection and radical lymphadenectomy at our institution between January 2012 and December 2020. V1- were compared to V0-patients (no blood vessel invasion). All patients received adjuvant therapy according to European guidelines when indicated. After excluding patients with detection of lymphangiosis carcinomatosa, tumor-cells at the resection margin, distant metastases and those, that received neoadjuvant therapy, 1-, 3- and 5- year survival rates were assessed by Kaplan-Meier method. To proof V1 as an independent risk factor, a propensity score matched (PSM) analysis was performed regarding age, gender, UICC-stage, lymph-node involvement, and comorbidities.

RESULTS

A total of 461 patients (V0: 440; V1: 21) were included in this analysis. Baseline characteristics did not show any significant difference. Mean age in V0-group was 65.7 ± 10.5 years and 64.1 ± 8.6 years in V1-group (p-value = 0.5). In the V0-group 54.8% were male, whereas in the V1-group this number was 66.7% (p-value = 0.37). Mean survival in V1-group was significantly shorter compared to V0-group (V1: 45.8 ± 9.3 months; V0: 81.1 ± 1.1 months; p-value<0.001). This was confirmed after applying a propensity score matched analysis (V0: 99.9 ± 4.9 months; V1: 45.8 ± 9.3 months; p-value<0.001) - V1 is a prognostic marker independent of UICC stage. The 1-, 3- and 5-year survival rates were significantly shorter for V1-patients (1-year: V0: 100%; V1: 70.6%; p-value = 0.012) (3-year: V0: 95.2%; V1: 46.2%; p-value = 0.002) (5-year: V0: 90.5%; V1: 36.4%; p-value = 0.003).

CONCLUSION

As we have shown with our investigations, V1 has a major impact on long-term survival in NSCLC patients and furthermore, acts as an independent risk factor. Due to our small but specified sample size, our statement should be confirmed by a multicenter study. In the meantime, we suggest making the implementation of the V0/V1 specification mandatory in the tumor classification.

Immunotherapy in Advanced Prostate Cancer-Light at the End of the Tunnel?

Immunotherapeutic treatment approaches are now an integral part of the treatment of many solid tumors. However, attempts to integrate immunotherapy into the treatment of prostate cancer have been disappointing so far. This is due to a highly immunosuppressive, "cold" tumor microenvironment, which is characterized, for example, by the absence of cytotoxic T cells, an increased number of myeloid-derived suppressor cells or regulatory T cells, a decreased number of tumor antigens, or a defect in antigen presentation. The consequence is a reduced efficacy of many established immunotherapeutic treatments such as checkpoint inhibitors. However, a growing understanding of the underlying mechanisms of tumor-immune system interactions raises hopes that immunotherapeutic strategies can be optimized in the future. The aim of this review is to provide an overview of the current status and future directions of immunotherapy development in prostate cancer. Background information on immune response and tumor microenvironment will help to better understand current therapeutic strategies under preclinical and clinical development.

Multiomics Analysis of Spatially Distinct Stromal Cells Reveals Tumor-Induced O-Glycosylation of the CDK4-pRB Axis in Fibroblasts at the Invasive Tumor Edge

The invasive leading edge represents a potential gateway for tumor metastasis. The role of fibroblasts from the tumor edge in promoting cancer invasion and metastasis has not been comprehensively elucidated. We hypothesize that cross-talk between tumor and stromal cells within the tumor microenvironment results in activation of key biological pathways depending on their position in the tumor (edge vs. core). Here we highlight phenotypic differences between tumor-adjacent-fibroblasts (TAF) from the invasive edge and tumor core fibroblasts from the tumor core, established from human lung adenocarcinomas. A multiomics approach that includes genomics, proteomics, and O-glycoproteomics was used to characterize cross-talk between TAFs and cancer cells. These analyses showed that O-glycosylation, an essential posttranslational modification resulting from sugar metabolism, alters key biological pathways including the cyclin-dependent kinase 4 (CDK4) and phosphorylated retinoblastoma protein axis in the stroma and indirectly modulates proinvasive features of cancer cells. In summary, the O-glycoproteome represents a new consideration for important biological processes involved in tumor-stroma cross-talk and a potential avenue to improve the anticancer efficacy of CDK4 inhibitors.

SIGNIFICANCE

A multiomics analysis of spatially distinct fibroblasts establishes the importance of the stromal O-glycoproteome in tumor-stroma interactions at the leading edge and provides potential strategies to improve cancer treatment. See related commentary by De Wever, p. 537.

Intravital deep-tumor single-beam 3-photon, 4-photon, and harmonic microscopy

Three-photon excitation has recently been demonstrated as an effective method to perform intravital microscopy in deep, previously inaccessible regions of the mouse brain. The applicability of 3-photon excitation for deep imaging of other, more heterogeneous tissue types has been much less explored. In this work, we analyze the benefit of high-pulse-energy 1 MHz pulse-repetition-rate infrared excitation near 1300 and 1700 nm for in-depth imaging of tumorous and bone tissue. We show that this excitation regime provides a more than 2-fold increased imaging depth in tumor and bone tissue compared to the illumination conditions commonly used in 2-photon excitation, due to improved excitation confinement and reduced scattering. We also show that simultaneous 3- and 4-photon processes can be effectively induced with a single laser line, enabling the combined detection of blue to far-red fluorescence together with second and third harmonic generation without chromatic aberration, at excitation intensities compatible with live tissue imaging. Finally, we analyze photoperturbation thresholds in this excitation regime and derive setpoints for safe cell imaging. Together, these results indicate that infrared high-pulse-energy low-repetition-rate excitation opens novel perspectives for intravital deep-tissue microscopy of multiple parameters in strongly scattering tissues and organs.

Propensity for Early Metastatic Spread in Breast Cancer: Role of Tumor Vascularization Features and Tumor Immune Infiltrate

Breast cancer is a complex and highly heterogeneous disease consisting of various subtypes. It is classified into human epidermal growth receptor 2 (HER-2)-enriched, luminal A, luminal B and basal-like/triple negative (TNBC) breast cancer, based on histological and molecular features. At present, clinical decision-making in breast cancer is focused only on the assessment of tumor cells; nevertheless, it has been recognized that the tumor microenvironment (TME) plays a critical biologic role in breast cancer. This is constituted by a large group of immune and non-immune cells, but also by non-cellular components, such as several cytokines. TME is deeply involved in angiogenesis, immune-evasion strategies, and propensity for early metastatic spread, impacting on prognosis and prediction of response to specific treatments. In this review, we focused our attention on the early morphological changes of tumor microenvironment (tumor vasculature features, presence of immune and non-immune cells infiltrating the stroma, levels of cytokines) during breast cancer development. At the same time, we correlate these characteristics with early metastatic propensity (defined as synchronous metastasis or early recurrence) with particular attention to breast cancer subtypes.

Heterogeneity of Circulating Tumor Cell Neoplastic Subpopulations Outlined by Single-Cell Transcriptomics

Simple Summary

Over 12% of women in the United States will be diagnosed with breast cancer in their lifetime. The overall 5-year survival rate for breast cancer is 90%, but the 5-year survival rate for women diagnosed with metastatic breast cancer is 28.1%. This study aims to characterize the cancerous cells that have left the primary tumor site and entered the blood, known as circulating tumor cells (CTCs). These cells could adhere to a site distant from the tumor and initiate metastasis. CTCs in breast cancer patients’ blood samples were enumerated and imaged. Cells from the blood were collected, RNA extracted, and the gene expression patterns of CTCs and other cell populations in the blood were investigated at the population and single cell level. This is a crucial step in characterizing CTCs as seeds of metastasis in breast cancer and for developing methods of detection to intercept metastasis before it localizes to distant regions of the body.

Abstract

Fatal metastasis occurs when circulating tumor cells (CTCs) disperse through the blood to initiate a new tumor at specific sites distant from the primary tumor. CTCs have been classically defined as nucleated cells positive for epithelial cell adhesion molecule and select cytokeratins (EpCAM/CK/DAPI), while negative for the common lymphocyte marker CD45. The enumeration of CTCs allows an estimation of the overall metastatic burden in breast cancer patients, but challenges regarding CTC heterogeneity and metastatic propensities persist, and their decryption could improve therapies. CTCs from metastatic breast cancer (mBC) patients were captured using the RareCyte^TM Cytefinder II platform. The Lin− and Lin+ (CD45+) cell populations isolated from the blood of three of these mBC patients were analyzed by single-cell transcriptomic methods, which identified a variety of immune cell populations and a cluster of cells with a distinct gene expression signature, which includes both cells expressing EpCAM/CK (“classic” CTCs) and cells possessing an array of genes not previously associated with CTCs. This study put forward notions that the identification of these genes and their interactions will promote novel areas of analysis by dissecting properties underlying CTC survival, proliferation, and interaction with circulatory immune cells. It improves upon capabilities to measure and interfere with CTCs for impactful therapeutic interventions.

Stationed or Relocating: The Seesawing EMT/MET Determinants from Embryonic Development to Cancer Metastasis

Epithelial and mesenchymal transition mechanisms continue to occur during the cell cycle and throughout human development from the embryo stage to death. In embryo development, epithelial-mesenchymal transition (EMT) can be divided into three essential steps. First, endoderm, mesoderm, and neural crest cells form, then the cells are subdivided, and finally, cardiac valve formation occurs. After the embryonic period, the human body will be subjected to ongoing mechanical stress or injury. The formation of a wound requires EMT to recruit fibroblasts to generate granulation tissues, repair the wound and re-create an intact skin barrier. However, once cells transform into a malignant tumor, the tumor cells acquire the characteristic of immortality. Local cell growth with no growth inhibition creates a solid tumor. If the tumor cannot obtain enough nutrition in situ, the tumor cells will undergo EMT and invade the basal membrane of nearby blood vessels. The tumor cells are transported through the bloodstream to secondary sites and then begin to form colonies and undergo reverse EMT, the so-called "mesenchymal-epithelial transition (MET)." This dynamic change involves cell morphology, environmental conditions, and external stimuli. Therefore, in this manuscript, the similarities and differences between EMT and MET will be dissected from embryonic development to the stage of cancer metastasis.

Extracellular ATP and adenosine in tumor microenvironment: Roles in epithelial-mesenchymal transition, cell migration, and invasion

Under nonpathological conditions, the extracellular nucleotide concentration remains constant and low (nM range) because of a close balance between ATP release and ATP consumption. This balance is completely altered in cancer disease. Adenine and uridine nucleotides are found in the extracellular space of tumors in high millimolar (mM) concentrations acting as extracellular signaling molecules. In general, although uridine nucleotides may be involved in different tumor cell responses, purinergic signaling in cancer is preferentially focused on adenine nucleotides and nucleosides. Extracellular ATP can bind to specific receptors (P receptors) triggering different responses, or it can be hydrolyzed by ectoenzymes bound to cell membranes to render the final product adenosine. The latter pathway plays an important role in the increase of adenosine in tumor microenvironment. In this study, we will focus on extracellular ATP and adenosine, their effects acting as ligands of specific receptors, activating ectoenzymes, and promoting epithelial-mesenchymal transition, migration, and invasion in cancer cells. Finding the roles that these nucleotides play in tumor microenvironment may be important to design new intervention strategies in cancer therapies.

Dextran-Curcumin Nanosystems Inhibit Cell Growth and Migration Regulating the Epithelial to Mesenchymal Transition in Prostate Cancer Cells

Functional nanocarriers which are able to simultaneously vectorize drugs to the site of interest and exert their own cytotoxic activity represent a significant breakthrough in the search for effective anticancer strategies with fewer side effects than conventional chemotherapeutics. Here, we propose previously developed, self-assembling dextran-curcumin nanoparticles for the treatment of prostate cancer in combination therapy with Doxorubicin (DOXO). Biological effectiveness was investigated by evaluating the cell viability in either cancer and normal cells, reactive oxygen species (ROS) production, apoptotic effect, interference with the cell cycle, and the ability to inhibit cell migration and reverse the epithelial to mesenchymal transition (EMT). The results proved a significant enhancement of curcumin efficiency upon immobilization in nanoparticles: IC50 reduced by a half, induction of apoptotic effect, and improved ROS production (from 67 to 134%) at low concentrations. Nanoparticles guaranteed a pH-dependent DOXO release, with a more efficient release in acidic environments. Finally, a synergistic effect between nanoparticles and Doxorubicin was demonstrated, with the free curcumin showing additive activity. Although in vivo studies are required to support the findings of this study, these preliminary in vitro data can be considered a proof of principle for the design of an effective therapy for prostate cancer treatment.

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.

Blood Vessel Invasion Predicts Postoperative Survival Outcomes and Systemic Recurrence Regardless of Location or Blood Vessel Type in Patients with Lung Adenocarcinoma

BACKGROUND

Presence of blood vessel invasion (BVI) is one of the prognostic indicators for lung cancer patients with surgical resection. However, prognostic roles of the location and the type of the involved blood vessel have not been fully evaluated yet.

PATIENTS AND METHODS

We retrieved the data of 217 cases of surgically resected lung adenocarcinoma from Asan Medical Center. Clinicopathologic features, including BVI, were reassessed. The location (tumor center and/or periphery) and involved blood vessel types (large and/or small vessels; arteries and/or veins) of BVI were separately examined on standard hematoxylin-eosin slides and confirmed by van Gieson elastic staining.

RESULTS

BVI was identified in 35% of cases (76/217), with the tumor center (intratumoral) as the location in more than half of the cases (42/76, 55.3%). The presence of BVI was significantly associated with higher pathologic stage, increased size of invasive components, frequent pleural invasion, lymphatic permeation, and spread through alveolar spaces. BVI was significantly associated with poor overall survival (OS) and recurrence-free survival (RFS) both in univariate and multivariate survival analyses [for OS, hazard ratio (HR) 1.92, 95% confidence interval (CI) 1.06-3.48, P = 0.031; for RFS, HR 2.65, 95% CI 1.64-4.28; P < 0.001]. BVI subgroups, according to location and type of the involved blood vessels, invariably displayed significantly poor RFS; however, the results for OS varied.

CONCLUSION

Regardless of their location or blood vessel type, presence of BVI is a useful predictor for postoperative survival outcomes, which should be carefully evaluated on pathologic examination.

Human colorectal cancer-on-chip model to study the microenvironmental influence on early metastatic spread

Colorectal cancer (CRC) progression is a complex process that is not well understood. We describe an in vitro organ-on-chip model that emulates in vivo tissue structure and the tumor microenvironment (TME) to better understand intravasation, an early step in metastasis. The CRC-on-chip incorporates fluid flow and peristalsis-like cyclic stretching and consists of endothelial and epithelial compartments, separated by a porous membrane. On-chip imaging and effluent analyses are used to interrogate CRC progression and the resulting cellular heterogeneity. Mass spectrometry-based metabolite profiles are indicative of a CRC disease state. Tumor cells intravasate from the epithelial channel to the endothelial channel, revealing differences in invasion between aggressive and non-aggressive tumor cells. Tuning the TME by peristalsis-like mechanical forces, the epithelial:endothelial interface, and the addition of fibroblasts influences the invasive capabilities of tumor cells. The CRC-on-chip is a tunable human-relevant model system and a valuable tool to study early invasive events in cancer.

Tumor grafted - chick chorioallantoic membrane as an alternative model for biological cancer research and conventional/nanomaterial-based theranostics evaluation

Introduction: Advancements in cancer management and treatment are associated with strong preclinical research data, in which reliable cancer models are demanded. Indeed, inconsistent preclinical findings and stringent regulations following the 3Rs principle of reduction, refinement, and replacement of conventional animal models currently pose challenges in the development and translation of efficient technologies. The chick embryo chorioallantoic membrane (CAM) is a system for the evaluation of treatment effects on the vasculature, therefore suitable for studies on angiogenesis. Apart from vascular effects, the model is now increasingly employed as a preclinical cancer model following tumor-grafting procedures.Areas covered: The broad application of CAM tumor model is highlighted along with the methods for analyzing the neoplasm and vascular system. The presented and cited investigations focus on cancer biology and treatment, encompassing both conventional and emerging nanomaterial-based modalities.Expert opinion: The CAM tumor model finds increased significance given the influences of angiogenesis and the tumor microenvironment in cancer behavior, then providing a qualified miniature system for oncological research. Ultimately, the establishment and increased employment of such a model may resolve some of the limitations present in the standard preclinical tumor models, thereby redefining the preclinical research workflow.

The CAM assay in the study of the metastatic process

Among the in vivo experimental models, the chick embryo chorioallantoic membrane (CAM) has been routinely used to implant several malignant cell lines or tumor tissues to study their angiogenic and metastatic capability. Since the chick embryo is naturally immunodeficient, the CAM can support the engraftment of tumor cells, and their growth therein can faithfully recapitulate most of the characteristics of the carcinogenic process including: growth, invasion, angiogenesis and colonization of distant tissues. This review article is focused on the discussion of the more recent literature data concerning the use of the CAM to investigate the metastatic process.

The Roles of Stroma-Derived Chemokine in Different Stages of Cancer Metastases

The intricate interplay between malignant cells and host cellular and non-cellular components play crucial role in different stages of tumor development, progression, and metastases. Tumor and stromal cells communicate to each other through receptors such as integrins and secretion of signaling molecules like growth factors, cytokines, chemokines and inflammatory mediators. Chemokines mediated signaling pathways have emerged as major mechanisms underlying multifaceted roles played by host cells during tumor progression. In response to tumor stimuli, host cells-derived chemokines further activates signaling cascades that support the ability of tumor cells to invade surrounding basement membrane and extra-cellular matrix. The host-derived chemokines act on endothelial cells to increase their permeability and facilitate tumor cells intravasation and extravasation. The tumor cells-host neutrophils interaction within the vasculature initiates chemokines driven recruitment of inflammatory cells that protects circulatory tumor cells from immune attack. Chemokines secreted by tumor cells and stromal immune and non-immune cells within the tumor microenvironment enter the circulation and are responsible for formation of a "pre-metastatic niche" like a "soil" in distant organs whereby circulating tumor cells "seed' and colonize, leading to formation of metastatic foci. Given the importance of host derived chemokines in cancer progression and metastases several drugs like Mogamulizumab, Plerixafor, Repertaxin among others are part of ongoing clinical trial which target chemokines and their receptors against cancer pathogenesis. In this review, we focus on recent advances in understanding the complexity of chemokines network in tumor microenvironment, with an emphasis on chemokines secreted from host cells. We especially summarize the role of host-derived chemokines in different stages of metastases, including invasion, dissemination, migration into the vasculature, and seeding into the pre-metastatic niche. We finally provide a brief description of prospective drugs that target chemokines in different clinical trials against cancer.

Neutrophil Elastase Facilitates Tumor Cell Intravasation and Early Metastatic Events

Functional roles of neutrophil elastase (NE) have not been examined in distinct steps of the metastatic cascade. NE, delivered to primary tumors as a purified enzyme or within intact neutrophils or neutrophil granule content, enhanced human tumor cell intravasation and subsequent dissemination via NE-mediated formation of dilated intratumoral vasculature. These effects depended on picomole range of NE activity, sensitive to its natural inhibitor, α1PI. In Elane-negative mice, the lack of NE decreased lung retention of human tumor cells in experimental metastasis. Furthermore, NE was essential for spontaneous metastasis of murine carcinoma cells in a syngeneic orthotopic model of oral cancer. NE also induced tumor cell survival and migration via Src/PI3K-dependent activation of Akt signaling, vital for tumor cell dissemination in vivo. Together, our findings implicate NE, a potent host enzyme specific for first-responding innate immune cells, as directly involved in early metastatic events and a potential target for therapeutic intervention.

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NE enhances human carcinoma cell intravasation and spontaneous metastasis

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NE mediates formation of dilated intratumoral vasculature supporting cell intravasation

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NE-KO mice exhibit decreased lung retention and spontaneous metastasis of tumor cells

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NE induces tumor cell survival and migration via activation of Src/PI3K/Akt pathway

Premetastasis

Sterile inflammation within primary tumor tissues can spread to distant organs that are devoid of tumor cells. This happens in a manner dependent on tumor-led secretome, before the actual metastasis occurs. The premetastatic microenvironment is established in this way and is at least partly regulated by hijacking the host innate immune system. The biological manifestation of premetastasis include increased vascular permeability, cell mobilization via the blood stream, degradation of the extracellular matrix, immunosuppression, and host antineoplastic activities.

Hematogenous Dissemination of Breast Cancer Cells From Lymph Nodes Is Mediated by Tumor MicroEnvironment of Metastasis Doorways

In primary breast tumors, cancer cells hematogenously disseminate through doorways in the vasculature composed of three-cell complexes (known as Tumor MicroEnvironment of Metastasis) comprising a perivascular macrophage, a tumor cell overexpressing the actin-regulatory protein Mammalian Enabled (Mena), and an endothelial cell, all in direct physical contact. It has been previously shown that once tumor cells establish lymph node metastases in patients, TMEM doorways form in the metastatic tumor cell nests. However, it has not been established if such lymph node-TMEM doorways actively transit tumor cells into the peripheral circulation and on to tertiary sites. To address this question in this short report, we used a mouse model of lymph node metastasis to demonstrate that TMEM doorways: (1) exist in tumor-positive lymph nodes of mice, (2) are restricted to the blood vascular endothelium, (3) serve as a mechanism for further dissemination to peripheral sites such as to the lungs, and (4) their activity can be abrogated by a pharmaceutical intervention. Our data suggest that cancer cell dissemination via TMEM doorways is a common mechanism of breast cancer cell dissemination to distant sites and thus the pharmacological targeting of TMEM may be necessary, even after resection of the primary tumor, to suppress cancer cell dissemination.

Circulating tumor cell enumeration for improved screening and disease detection of patients with colorectal cancer

Background

The immunochemical fecal occult blood test (iFOBT) for colorectal cancer (CRC) screening and the serum carcinoembryonic antigen (CEA) assay for disease detection of CRC is associated with a high false-positive rate and a low detection sensitivity, respectively. There is an unmet need to define additional modalities to complement these assays. Different subsets of circulating tumor cells (CTCs) are present in the peripheral blood of cancer patients. Whether or not CTCs testing supplements these clinical assays and is valuable for patients with CRC was investigated.

Methods

CTCs were enriched from pre-operative patients with CRC (n = 109) and the non-cancerous controls (n = 65). CTCs expressing either epithelial cell adhesion molecule (EpCAM) or podoplanin (PDPN, the marker associated with poor cancer prognosis) were defined by immunofluorescence staining and were analyzed alone or in combination with iFOBT or serum CEA.

Results

Patients with early or advanced stage of CRC can be clearly identified and differentiated from the non-cancerous controls (p < 0.001) by EpCAM⁺-CTC or PDPN⁺-CTC count. The sensitivity and specificity of EpCAM⁺-CTCs was 85.3% and 78.5%, respectively, when the cutoff value was 23 EpCAM⁺-CTCs/mL of blood; and the sensitivity and specificity of PDPN⁺-CTCs was 78.0% and 75.4%, respectively, when the cutoff value was 7 PDPN⁺-CTCs/mL of blood. Combined analysis of iFOBT with the EpCAM⁺-CTC and PDPN⁺-CTC count reduced the false-positive rate of iFOBT from 56.3% to 18.8% and 23.4%, respectively. Combined analysis of serum CEA with the EpCAM⁺-CTC and PDPN⁺-CTC count increased the disease detection rate from 30.3% to 89.9% and 86.2%, respectively.

Conclusion

CTC testing could supplement iFOBT to improve CRC screening and supplement serum CEA assay for better disease detection of patients with CRC.

The role of the tumor microenvironment in tumor cell intravasation and dissemination

Metastasis, a process that requires tumor cell dissemination followed by tumor growth, is the primary cause of death in cancer patients. An essential step of tumor cell dissemination is intravasation, a process by which tumor cells cross the blood vessel endothelium and disseminate to distant sites. Studying this process is of utmost importance given that intravasation in the primary tumor, as well as the secondary and tertiary metastases, is the key step in the systemic spread of tumor cells, and that this process continues even after removal of the primary tumor. High-resolution intravital imaging of the tumor microenvironment of breast carcinoma has revealed that tumor cell intravasation exclusively occurs at doorways, termed "Tumor MicroEnvironment of Metastasis" (TMEM), composed of three different cell types: a Tie2^high/VEGF^high perivascular macrophage, a Mena overexpressing tumor cell, and an endothelial cell, all in direct contact. In this review article, we discuss the interactions between these cell types, the subsequent signaling events which lead to tumor cell intravasation, and the role of invadopodia in supporting tumor cell invasion and dissemination. We end our review by discussing how the knowledge acquired from the use of intravital imaging is now leading to new clinical trials targeting tumor cell dissemination and preventing metastatic progression.

In Vivo Detection of CTC and CTC Plakoglobin Status Helps Predict Prognosis in Patients with Metastatic Breast Cancer

This study aims to detect the prognostic value of circulating tumour cell (CTC) in patients with metastatic breast cancer. In this study, 38 patients with metastatic breast cancer were enrolled. The in vivo CellCollector® method was used to detect the number of CTC in patients. Single CTC and CTC clusters were counted, and the expression of plakoglobin was also analysed. At baseline, 73.7% (28/38) of the patients were positive for ≥ 1 CTC (range, 1-14 cells). No CTC-like events were observed in the control group. Among the CTC-positive patients, 21.4% (6/28) of patients had CTC clusters, and 42.9% (12/28) of patients had plakoglobin-positive CTC. After chemotherapy, 48.6% (17/35) of the patients were positive for ≥ 1 CTC (range, 1-3 cells), of which 3 patients had CTC clusters, and 35.3% (6/17) had plakoglobin-positive CTC. Additionally, we found that the number of CTC clusters in plakoglobin-positive patients was much greater than that in plakoglobin-negative patients, and the number of CTC was associated with the number of sites of metastases. We also found that patients with ≥ 3 CTC at baseline had shorter progression-free survival (PFS) and overall survival (OS), and pre-chemotherapy CTC detection was associated with PFS (P = 0.0001) and OS (P = 0.0091). CTC plakoglobin expression was associated with PFS (P = 0.02) but not OS (P = 0.22). CTC collected by the in vivo CellCollector method in Chinese patients with metastatic breast cancer have prognostic significance. CTC plakoglobin expression may be associated with CTC clusters, and more in-depth studies are needed.

Pro-tumorigenic functions of macrophages at the primary, invasive and metastatic tumor site

The tumor microenvironment (TME) not only facilitates cancer progression from the early formation to distant metastasis, but also it differs itself from time to time alongside the tumor evolution. Tumor-associated macrophages (TAMs), whether as pre-existing tissue-resident macrophages or recruited monocytes, are an inseparable part of this microenvironment. As their parents are broadly classified into a dichotomic, simplistic M1 and M2 subtypes, TAMs also exert paradoxical and diverse phenotypes as they are settled in different regions of TME and receive different microenvironmental signals. Briefly, M1 macrophages induce an inflammatory precancerous niche and flame the early oncogenic mutations, whereas their M2 counterparts are reprogrammed to release various growth factors and providing an immunosuppressive state in TME as long as abetting hypoxic cancer cells to set up a new vasculature. Further, they mediate stromal micro-invasion and co-migrate with invasive cancer cells to invade the vascular wall and neural sheath, while another subtype of TAMs prepares suitable niches much earlier than metastatic cells arrive at the target tissues. Accordingly, at the neoplastic transformation, during the benign-to-malignant transition and through the metastatic cascade, macrophages are involved in shaping the primary, micro-invasive and pre-metastatic TMEs. Whether their behavioral plasticity is derived from distinct genotypes or is fueled by microenvironmental cues, it could define these cells as remarkably interesting therapeutic targets.

Heterogeneity of Stemlike Circulating Tumor Cells in Invasive Breast Cancer

The presence of stem and epithelial–mesenchymal-transition (EMT) features in circulating tumor cells (CTCs) determines their invasiveness, adaptability to the microenvironment, and resistance to proapoptotic signals and chemotherapy. It also allows them to fulfil the role of metastatic “seeds”. We evaluated the heterogeneity of stem CTCs by their CD44, ALDH1, and CD133 expression depending on N-cadherin expression in breast-cancer patients. A total of 38 female patients were selected for this study. CTC phenotypes were determined by flow cytometry before any type of treatment. Multiplex immunofluorescence was used for the evaluation of tumor-cell heterogeneity in primary lesions. In patients who had CD44-CD24- CTCs, a subset of cells with the expression of other stem-cell markers (CD133 and ALDH1) were detected. Expression of CD133 and/or ALDH1 may be associated with expression of N-cadherin: all populations of N-cadherin+ CTCs demonstrate stem features; in the absence of N-cadherin expression, true nonstem (CD44-CD24-CD133-ALDH1-) cells are found. The heterogeneity of stem marker expression in CTCs was observed regardless of N-cadherin expression. In our study, stromal cell-derived factor-1 (SDF-1) receptor expression in CTCs did not depend on stemlike traits, but was instead associated with N-cadherin expression. Subpopulations of tumor cells, detected both in tumors and blood, were identified. Breast cancer was characterized by pronounced interpersonal and intrapersonal heterogeneity of CTCs by the presence and combination of various stem features and N-cadherin expression. To complete the characterization of stemlike features of CTCs, we suggest the simultaneous use of the three stem markers.

Adapt and conquer: Metabolic flexibility in cancer growth, invasion and evasion

BACKGROUND

It has been known for close to a century that, on average, tumors have a metabolism that is different from those found in healthy tissues. Typically, tumors show a biosynthetic metabolism that distinguishes itself by engaging in large scale aerobic glycolysis, heightened flux through the pentose phosphate pathway, and increased glutaminolysis among other means. However, it is becoming equally clear that non tumorous tissues at times can engage in similar metabolism, while tumors show a high degree of metabolic flexibility reacting to cues, and stresses in their local environment.

SCOPE OF THE REVIEW

In this review, we want to scrutinize historic and recent research on metabolism, comparing and contrasting oncogenic and physiological metabolic states. This will allow us to better define states of bona fide tumor metabolism. We will further contextualize the stress response and the metabolic evolutionary trajectory seen in tumors, and how these contribute to tumor progression. Lastly, we will analyze the implications of these characteristics with respect to therapy response.

MAJOR CONCLUSIONS

In our review, we argue that there is not one single oncogenic state, but rather a diverse set of oncogenic states. These are grounded on a physiological proliferative/wound healing program but distinguish themselves due to their large scale of proliferation, mutations, and transcriptional changes in key metabolic pathways, and the adaptations to widespread stress signals within tumors. We find evidence for the necessity of metabolic flexibility and stress responses in tumor progression and how these responses in turn shape oncogenic progression. Lastly, we find evidence for the notion that the metabolic adaptability of tumors frequently frustrates therapeutic interventions.

microRNAs Orchestrate Pathophysiology of Breast Cancer Brain Metastasis: Advances in Therapy

Brain metastasis (BM) predominantly occurs in triple-negative (TN) and epidermal growth factor 2 (HER2)-positive breast cancer (BC) patients, and currently, there is an unmet need for the treatment of these patients. BM is a complex process that is regulated by the formation of a metastatic niche. A better understanding of the brain metastatic processes and the crosstalk between cancer cells and brain microenvironment is essential for designing a novel therapeutic approach. In this context, the aberrant expression of miRNA has been shown to be associated with BM. These non-coding RNAs/miRNAs regulate metastasis through modulating the formation of a metastatic niche and metabolic reprogramming via regulation of their target genes. However, the role of miRNA in breast cancer brain metastasis (BCBM) is poorly explored. Thus, identification and understanding of miRNAs in the pathobiology of BCBM may identify a novel candidate miRNA for the early diagnosis and prevention of this devastating process. In this review, we focus on understanding the role of candidate miRNAs in the regulation of BC brain metastatic processes as well as designing novel miRNA-based therapeutic strategies for BCBM.

Disease progression model of 4T1 metastatic breast cancer

Cancer metastasis is the main cause of death in various types of cancer. However, in the field of pharmacometrics, cancer disease progression models focus on the growth of primary tumors with tumor volume or weight as target values, while the metastasis process is less mentioned. We propose a series of mathematical models to quantitatively describe and predict the disease progression of 4T1 breast cancer in the aspect of primary breast tumor, lung metastasis and white blood cell. The 4T1 cells were injected into breast fat pad of female BALB/c mice to establish an animal model of breast cancer metastasis. The number and volume of lung metastases at different times were measured. Based on the above data, a disease progression model of breast cancer lung metastasis was established and parameter values were estimated. The white blood cell growth and the primary tumor growth of 4T1 mouse are also modeled. The established models can describe the lung metastasis of 4T1 breast cancer in three aspects: (1) the increase in metastasis number; (2) the growth of metastasis volume; (3) metastasis number-size distribution at different time points. Compared with the prior metastasis models based on von Forester equation, our models distinguished the growth rate of primary tumor and metastasis and got parameter values for 4T1 mouse model. And the current models optimized the metastasis number-size distribution model by utilizing logistic function instead of the prior power function. This study provides a comprehensive description of lung metastasis progression for 4T1 breast cancer model, as well as an alternative disease progression model structure for further pharmacodynamics modeling.

Impaired Metabolic Pathways Related to Colorectal Cancer Progression and Therapeutic Implications

BACKGROUND

Risk of colorectal cancer (CRC) is defined by genetic predisposition and environmental factors that often co-occur and interact, resulting in diversiform biological reactions. The present study attempted to investigate transcriptome alteration and adaptation associated with CRC progression.

METHODS

The study consisted of patients who presented at Memorial Sloan-Kettering Cancer Center, Guangzhou, China with a colonic neoplasm in 1992-2004. Microarray GSE41258 of the study was acquired from Gene Expression Omnibus and 253 included microarrays were categorized by groups of normal colon, early primary tumor, lymph node metastases primary tumor, advanced primary tumor and distant metastases. Short Time-series Expression Miner (STEM) was applied to discover tumor grade-dependent gene expression patterns. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to explore functional enrichment of differential expression genes (DEGs).

RESULTS

Overall, 2870 significant DEGs were screened out on all groups. Six significant grade-dependent gene expression patterns were statistically significant. DEGs in all significant patterns were mainly assembled in GO terms of metastases and deterioration of tumor, epithelial proteins and cytokines, and protein binding and bridging. DEGs in profile 0 down-regulated with higher tumor grade, prominently enriched in KEGG pathways of metabolism.

CONCLUSION

Besides many well-known colorectal cancer-related pathways, DEGs of profiles especially those down-regulated with CRC progression, clustered in various metabolic pathways including starch and sucrose metabolism, fatty acid metabolism, nitrogen metabolism, as well as xenobiotics biotransformation that link to tumorigenesis, demonstrating the impairment of physiological metabolic pathways in the context of tumor progression. These results gave a high potential for therapeutic strategies.

Intravasation as a Key Step in Cancer Metastasis

Intravasation is a key step in cancer metastasis during which tumor cells penetrate the vessel wall and enter circulation, thereby becoming circulating tumor cells and potential metastatic seeds. Understanding the molecular mechanisms of intravasation is critically important for the development of therapeutic strategies to prevent metastasis. In this article, we review current data on the mechanisms of cancer cell intravasation into the blood and lymphatic vessels. The entry of mature thymocytes into the circulation and of dendritic cells into the regional lymph nodes is considered as example of intravasation under physiologically normal conditions. Intravasation in a pathophysiological state is illustrated by the reverse transendothelial migration of leukocytes into the bloodstream from the sites of inflammation mediated by the sphingosine 1-phosphate interaction with its receptors. Intravasation involves both invasion-dependent and independent mechanisms. In particular, mesenchymal and amoeboid cell invasion, as well as neoangiogenesis and vascular remodeling, are discussed to play a significant role in the entry of tumor cells to the circulation. Special attention is given to the contribution of macrophages to the intravasation via the CSF1/EGF (colony stimulating factor 1/epidermal growth factor) paracrine signaling pathway and the TMEM (tumor microenvironment of metastasis)-mediated mechanisms. Other mechanisms including intravasation of tumor cell clusters surrounded by the vessel wall elements, cooperative intravasation (entry of non-invasive tumor cells to the circulation following invasive tumor cells), and intravasation associated with the vasculogenic mimicry (formation of vascular channels by tumor cells) are also discussed. Novel intravasation-specific mechanisms that have not yet been described in the literature are suggested. The importance of targeted therapeutic strategies to prevent cancer intravasation is emphasized.

Combretastatin analogues in cancer biology: A prospective view

The stilbenoid combretastatin and its derivatives are potent inhibitors of angiogenesis and cell proliferation and induce apoptosis. They disrupt cytoskeletal dynamics and modulate cell morphology, motility, and invasion. Hence they have been viewed as potential as anticancer agents. The impediments of poor solubility and bioavailability and the spontaneous geometric isomerisation of combretastatin into an inactive form have led to intensive efforts towards evolving novel analogues to provide more efficacious biological outcome. Importantly, isomerically stable and biologically active cis-restricted analogues have been synthesised and tested. However, very few analogues have been tested in preclinical models to assess their effects on processes relevant to cancer development and progression. Hence the accent here is on the signalling systems operated by the new derivatives and their biological effects with reference to cancer progression. Combretastatins modulate an extensive network of signalling emphasising their varied versatility. Harnessing these systems and accentuating or counteracting aberrant signalling could open potential avenues of approach to the designing of novel derivatives with enhanced performance. The import of mammalian target of rapamycin pathway, which co-ordinates growth factor receptor signalling, epithelial-mesenchymal transition activation and angiogenic signalling, is emphasised. It may be viewed as a prime target for allosteric inhibition in combination with combretastatin analogues to ascertain their potential in cancer control.

Angiotropism, pericytic mimicry and extravascular migratory metastasis: an embryogenesis-derived program of tumor spread

Intravascular dissemination of tumor cells is the accepted mechanism of cancer metastasis. However, the phenomenon of angiotropism, pericyte mimicry (PM), and extravascular migratory metastasis (EVMM) has questioned the concept that tumor cells metastasize exclusively via circulation within vascular channels. This new paradigm of cancer spread and metastasis suggests that metastatic cells employ embryonic mechanisms for attachment to the abluminal surfaces of blood vessels (angiotropism) and spread via continuous migration, competing with and replacing pericytes, i.e., pericyte mimicry (PM). This is an entirely extravascular phenomenon (i.e., extravascular migratory metastasis or EVMM) without entry (intravasation) into vascular channels. PM and EVMM have mainly been studied in melanoma but also occur in other cancer types. PM and EVMM appear to be a reversion to an embryogenesis-derived program. There are many analogies between embryogenesis and cancer progression, including the important role of laminins, epithelial-mesenchymal transition, and the re-activation of embryonic signals by cancer cells. Furthermore, there is no circulation of blood during the first trimester of embryogenesis, despite the fact that there is extensive migration of cells to distant sites and formation of organs and tissues during this period. Embryonic migration therefore is a continuous extravascular migration as are PM and EVMM, supporting the concept that these embryonic migratory events appear to recur abnormally during the metastatic process. Finally, the perivascular location of tumor cells intrinsically links PM to vascular co-option. Taken together, these two new paradigms may greatly influence the development of new effective therapeutics for metastasis. In particular, targeting embryonic factors linked to migration that are detected during cancer metastasis may be particularly relevant to PM/EVMM.

Cancer cells in the tumor core exhibit spatially coordinated migration patterns

In the early stages of metastasis, cancer cells exit the primary tumor and enter the vasculature. Although most studies have focused on the tumor invasive front, cancer cells from the tumor core can also potentially metastasize. To address cell motility in the tumor core, we imaged tumor explants from spontaneously forming tumors in mice in real time using long-term two-photon microscopy. Cancer cells in the tumor core are remarkably dynamic and exhibit correlated migration patterns, giving rise to local 'currents' and large-scale tissue dynamics. Although cells exhibit stop-and-start migration with intermittent pauses, pausing does not appear to be required during division. Use of pharmacological inhibitors indicates that migration patterns in tumors are actively driven by the actin cytoskeleton. Under these conditions, we also observed a relationship between migration speed and correlation length, suggesting that cells in tumors are near a jamming transition. Our study provides new insight into the dynamics of cancer cells in the tumor core, opening new avenues of research in understanding the migratory properties of cancer cells and later metastasis.This article has an associated First Person interview with the first author of the paper.

The Different Routes to Metastasis via Hypoxia-Regulated Programs

Hypoxia is linked to metastasis; however, how it affects metastatic progression is not clear due to limited consensus in the literature. We posit that this lack of consensus is due to hypoxia being studied using different approaches, such as in vitro, primary tumor, or metastasis assays in an isolated manner. Here, we review the pros and cons of in vitro hypoxia assays, highlight in vivo studies that inform on physiological hypoxia, and review the evidence that primary tumor hypoxia might influence the fate of disseminated tumor cells (DTCs) in secondary organs. Our analysis suggests that consensus can be reached by using in vivo methods of study, which also allow better modeling of how hypoxia affects DTC fate and metastasis.