Events In Cancer Metastasis Research Articles

LOXL1 and LOXL4 are novel target genes of the Zn2+-bound form of ZEB1 and play a crucial role in the acceleration of invasive events in triple-negative breast cancer cells.

EMT has been proposed to be a crucial early event in cancer metastasis. EMT is rigidly regulated by the action of several EMT-core transcription factors, particularly ZEB1. We previously revealed an unusual role of ZEB1 in the S100A8/A9-mediated metastasis in breast cancer cells that expressed ZEB1 at a significant level and showed that the ZEB1 was activated on the MCAM-downstream pathway upon S100A8/A9 binding. ZEB1 is well known to require Zn2+ for its activation based on the presence of several Zn-finger motifs in the transcription factor. However, how Zn2+-binding works on the pleiotropic role of ZEB1 through cancer progression has not been fully elucidated. We established the engineered cells, MDA-MB-231 MutZEB1 (MDA-MutZEB1), that stably express MutZEB1 (ΔZn). The cells were then evaluated in vitro for their invasion activities. Finally, an RNA-Seq analysis was performed to compare the gene alteration profiles of the established cells comprehensively. MDA-MutZEB1 showed a significant loss of the EMT, ultimately stalling the invasion. Inclusive analysis of the transcription changes after the expression of MutZEB1 (ΔZn) in MDA-MB-231 cells revealed the significant downregulation of LOX family genes, which are known to play a critical role in cancer metastasis. We found that LOXL1 and LOXL4 remarkably enhanced cancer invasiveness among the LOX family genes with altered expression. These findings indicate that ZEB1 potentiates Zn2+-mediated transcription of plural EMT-relevant factors, including LOXL1 and LOXL4, whose upregulation plays a critical role in the invasive dissemination of breast cancer cells.

ARID1A regulates E-cadherin expression in colorectal cancer cells: a promising candidate therapeutic target.

Metastasis is a major cause of death in Colorectal cancer (CRC) patients, and the Epithelial-mesenchymal transition (EMT) has been known to be a crucial event in cancer metastasis. Downregulated expression of AT-rich interaction domain-containing protein 1A (ARID1A), a bona fide tumor suppressor gene, plays an important role in promoting EMT and CRC metastasis, but the underlying molecular mechanisms remain poorly understood. Here, we evaluated the impact of ARID1A knockdown and overexpression on the expression of EMT‑related genes, E-cadherin and β-catenin, in human CRC cells. The expression levels of ARID1A, E-cadherin and β-catenin in CRC cell lines were detected via real-time quantitative PCR (qPCR) and western blot. ARID1A overexpression and shRNA-mediated knockdown were performed to indicate the effect of ARID1A expression on E-cadherin and β-catenin expression in CRC cell lines. The effect of ARID1A knockdown on the migration ability of HCT116 cells was assessed using wound-healing assay. We found that the mRNA and protein expression of adhesive protein E-cadherin was remarkably downregulated in response to shRNA-mediated ARID1A knockdown in HCT116 and HT29 cells. Conversely, overexpression of ARID1A in SW48 cells significantly increased E-cadherin expression. In addition, ARID1A silencing promoted the migration of HCT116 cells. ARID1A knockdown and overexpression did not alter the level of β-catenin expression. Our study demonstrates that E-cadherin levels were closely correlated with ARID1A expression. Thus, ARID1A downregulation may promote CRC metastasis through decreasing EMT‑related protein E-cadherin and promoting epithelial cell movement. ARID1A could represent a promising candidate therapeutic target for CRC.

KAT6A Acetylation of SMAD3 Regulates Myeloid-Derived Suppressor Cell Recruitment, Metastasis, and Immunotherapy in Triple-Negative Breast Cancer.

Aberrant SMAD3 activation has been implicated as a driving event in cancer metastasis, yet the underlying mechanisms are still elusive. Here, SMAD3 is identified as a nonhistone substrate of lysine acetyltransferase 6A (KAT6A). The acetylation of SMAD3 at K20 and K117 by KAT6A promotes SMAD3 association with oncogenic chromatin modifier tripartite motif‐containing 24 (TRIM24) and disrupts SMAD3 interaction with tumor suppressor TRIM33. This event in turn promotes KAT6A‐acetylated H3K23‐mediated recruitment of TRIM24–SMAD3 complex to chromatin and thereby increases SMAD3 activation and immune response‐related cytokine expression, leading to enhanced breast cancer stem‐like cell stemness, myeloid‐derived suppressor cell (MDSC) recruitment, and triple‐negative breast cancer (TNBC) metastasis. Inhibiting KAT6A in combination with anti‐PD‐L1 therapy in treating TNBC xenograft‐bearing animals markedly attenuates metastasis and provides a significant survival benefit. Thus, the work presents a KAT6A acetylation‐dependent regulatory mechanism governing SMAD3 oncogenic function and provides insight into how targeting an epigenetic factor with immunotherapies enhances the antimetastasis efficacy.

EB2 promotes hepatocellular carcinoma proliferation and metastasis via MAPK/ERK pathway by modulating microtubule dynamics.

Metastasis is the main cause of poor postoperative survival of hepatocellular carcinoma (HCC) patients. Cytoskeleton rearrangement is a key event in cancer metastasis. However, the significance of microtubule (MT), one of the core components of cytoskeleton, in this process is only beginning to be revealed. Here, we find that the MT dynamics regulator end-binding protein 2 (EB2) is highly expressed in HCC and predicts poor prognosis of HCC patients. Functional studies show that EB2 overexpression promotes HCC proliferation, invasion and metastasis in vitro and in vivo, while EB2 knockdown has opposite results. Mechanistically, EB2 mediates MTs destabilization, increases Src (Src proto-oncogene non-receptor tyrosine kinase) activity, and thus facilitates extracellular signal-regulated kinase (ERK) signaling activation, which could in turn promote EB2 expression in HCC, eventually resulting in enhanced HCC proliferation, invasion and metastasis. Furthermore, U0126, a specific ERK inhibitor, could effectively inhibit EB2-mediated HCC proliferation and metastasis in vitro and in vivo. In conclusion, EB2 coordinates MT cytoskeleton and intracellular signal transduction, forming an EB2-MT-ERK positive feedback loop, to facilitate HCC proliferation, invasion and metastasis. EB2 could serve as a promising prognostic biomarker and potential therapeutic target for HCC; HCC patients with high EB2 expression may benefit from treatment with ERK inhibitors.

Val16A SOD2 Polymorphism Promotes Epithelial–Mesenchymal Transition Antagonized by Muscadine Grape Skin Extract in Prostate Cancer Cells

Epithelial–mesenchymal transition (EMT), a key event in cancer metastasis, allows polarized epithelial cells to assume mesenchymal morphologies, enhancing invasiveness and migration, and can be induced by reactive oxygen species (ROS). Val16A (Ala) SOD2 polymorphism has been associated with increased prostate cancer (PCa) risk. We hypothesized that SOD2 Ala single nucleotide polymorphism (SNP) may promote EMT. We analyzed SOD2 expression and genotype in various prostate cell lines. Stable overexpression of Ala-SOD2 or Val-SOD2 allele was performed in Lymph Node Carcinoma of the Prostate (LNCaP) cells followed by analysis of intracellular ROS and EMT marker protein expression. Treatments were performed with muscadine grape skin extract (MSKE) antioxidant, with or without addition of H2O2 to provide further oxidative stress. Furthermore, MTS cell proliferation, cell migration, and apoptosis assays were completed. The results showed that SOD2 expression did not correlate with tumor aggressiveness nor SOD2 genotype. We demonstrated that the Ala-SOD2 allele was associated with marked induction of EMT indicated by higher Snail and vimentin, lower E-cadherin, and increased cell migration, when compared to Val-SOD2 allele or Neo control cells. Ala-SOD2 SNP cells exhibited increased levels of total ROS and superoxide and were more sensitive to co-treatment with H2O2 and MSKE, which led to reduced cell growth and increased apoptosis. Additionally, MSKE inhibited Ala-SOD2 SNP-mediated EMT. Our data indicates that treatment with a combination of H2O2-generative drugs, such as certain chemotherapeutics and antioxidants such as MSKE that targets superoxide, hold promising therapeutic potential to halt PCa progression in the future.

Corrigendum] Ski prevents TGF‑β‑induced EMT and cell invasion by repressing SMAD‑dependent signaling in non‑small cell lung cancer.

Following the publication of the above paper, an interested reader drew to our attention apparent anomalies associated with Figs.2, 3 and 4; essentially, these three figures contained panels exhibiting overlapping data, such that data purportedly relating to different experiments were apparently drawn from the same original sources. [Specifically, the Ski, +TGF‑β1 data panel in Fig.2B, the Mock, +TGF‑β1 data panel in Fig.3A, and the +TGF‑β1, +SIS3 data panel in Fig.4B in the original figures were chosen incorrectly.] Upon investigating this matter with the authors, the authors have realized that they made errors in the compilation of the affected figures. The errors were made inadvertently, and the authors have been able to identify the correct data for each of the figures concerned. The corrected versions of these figures are shown opposite and on the next page. Note that these errors did not affect the overall conclusions reported in the study. The authors are grateful to the Editor of Oncology Reports for allowing them the opportunity to publish this Corrigendum; furthermore, the authors apologize for any inconvenience caused to the readership of the Journal. [the original article was published in Oncology Reports 34: 87-94, 2015; DOI: 10.3892/or.2015.3961].

Cell stemness, epithelial-to-mesenchymal transition, and immunoevasion: Intertwined aspects in cancer metastasis.

Recent advances in tumor immunology, fostered by dramatic outcomes with cancer immunotherapy, have opened new scenarios in cancer metastasis. The cancer stemness/mesenchymal phenotype and an excess of immune suppressive signals are emerging as Intertwined aspects of human tumors. This review examines recent studies that explored the mechanistic links between cancer cell stemness and immunoevasion, and the evidence points to these key events in cancer metastasis as two sides of the same coin. This review also covers the mechanisms involved in tumor expression of programmed cell death ligand 1 (PD-L1), a major factor exploited by human neoplasias to suppress immune control. We highlight the convergence of mesenchymal traits and PD-L1 expression and examine the functions of this immune inhibitory molecule, which confers cancer cell resistance and aggressiveness.

Epigenetic drivers of tumourigenesis and cancer metastasis.

Since the completion of the first human genome sequence and the advent of next generation sequencing technologies, remarkable progress has been made in understanding the genetic basis of cancer. These studies have mainly defined genetic changes as either causal, providing a selective advantage to the cancer cell (a driver mutation) or consequential with no selective advantage (not directly causal, a passenger mutation). A vast unresolved question is how a primary cancer cell becomes metastatic and what are the molecular events that underpin this process. However, extensive sequencing efforts indicate that mutation may not be a causal factor for primary to metastatic transition. On the other hand, epigenetic changes are dynamic in nature and therefore potentially play an important role in determining metastatic phenotypes and this area of research is just starting to be appreciated. Unlike genetic studies, current limitations in studying epigenetic events in cancer metastasis include a lack of conceptual understanding and an analytical framework for identifying putative driver and passenger epigenetic changes. In this review, we discuss the key concepts involved in understanding the role of epigenetic alterations in the metastatic cascade. We particularly focus on driver epigenetic events, and we describe analytical approaches and biological frameworks for distinguishing between "epi-driver" and "epi-passenger" events in metastasis. Finally, we suggest potential directions for future research in this important area of cancer research.

Single-cell sequencing deciphers a convergent evolution of copy number alterations from primary to circulating tumor cells.

Copy number alteration (CNA) is a major contributor to genome instability, a hallmark of cancer. Here, we studied genomic alterations in single primary tumor cells and circulating tumor cells (CTCs) from the same patient. Single-nucleotide variants (SNVs) in single cells from both samples occurred sporadically, whereas CNAs among primary tumor cells emerged accumulatively rather than abruptly, converging toward the CNA in CTCs. Focal CNAs affecting the MYC gene and the PTEN gene were observed only in a minor portion of primary tumor cells but were present in all CTCs, suggesting a strong selection toward metastasis. Single-cell structural variant (SV) analyses revealed a two-step mechanism, a complex rearrangement followed by gene amplification, for the simultaneous formation of anomalous CNAs in multiple chromosome regions. Integrative CNA analyses of 97 CTCs from 23 patients confirmed the convergence of CNAs and revealed single, concurrent, and mutually exclusive CNAs that could be the driving events in cancer metastasis.

GDF15 promotes EMT and metastasis in colorectal cancer.

Metastasis is the major cause of cancer deaths, and the epithelial-mesenchymal transition (EMT) has been considered to be a fundamental event in cancer metastasis. However, the role of growth differentiation factor 15 (GDF15) in colorectal cancer (CRC) metastasis and EMT remains poorly understood. Here, we showed that GDF15 promoted CRC cell metastasis both in vitro and in vivo. In addition, the EMT process was enhanced by GDF15 through binding to TGF-β receptor to activate Smad2 and Smad3 pathways. Clinical data showed GDF15 level in tumor tissues, and the serum was significantly increased, in which high GDF15 level correlated with a reduced overall survival in CRC. Thus, GDF15 may promote colorectal cancer metastasis through activating EMT. Promisingly, GDF15 could be considered as a novel prognostic marker for CRC in the clinic.

Single-cell Migration Chip for Chemotaxis-based Microfluidic Selection of Heterogeneous Cell Populations.

Tumor cell migration toward and intravasation into capillaries is an early and key event in cancer metastasis, yet not all cancer cells are imbued with the same capability to do so. This heterogeneity within a tumor is a fundamental property of cancer. Tools to help us understand what molecular characteristics allow a certain subpopulation of cells to spread from the primary tumor are thus critical for overcoming metastasis. Conventional in vitro migration platforms treat populations in aggregate, which leads to a masking of intrinsic differences among cells. Some migration assays reported recently have single-cell resolution, but these platforms do not provide for selective retrieval of the distinct migrating and non-migrating cell populations for further analysis. Thus, to study the intrinsic differences in cells responsible for chemotactic heterogeneity, we developed a single-cell migration platform so that individual cells’ migration behavior can be studied and the heterogeneous population sorted based upon chemotactic phenotype. Furthermore, after migration, the highly chemotactic and non-chemotactic cells were retrieved and proved viable for later molecular analysis of their differences. Moreover, we modified the migration channel to resemble lymphatic capillaries to better understand how certain cancer cells are able to move through geometrically confining spaces.

Ski prevents TGF-β-induced EMT and cell invasion by repressing SMAD-dependent signaling in non-small cell lung cancer.

Epithelial-mesenchymal transition (EMT) is a key event in cancer metastasis, which confers cancer cells with increased motility and invasiveness, and EMT is characterized by loss of epithelial marker E-cadherin and gain of mesenchymal marker N-cadherin. Transforming growth factor-β (TGF-β) signaling is a crucial inducer of EMT in various types of cancer. Ski is an important negative regulator of TGF-β signaling, which interacts with SMADs to repress TGF-β signaling activity. Although there is accumulating evidence that Ski functions as a promoter or suppressor in human types of cancer, the molecular mechanisms by which Ski affects TGF-β-induced EMT and invasion in non-small cell lung cancer (NSCLC) are not largely elucidated. In the present study, we investigated the mechanistic role of Ski in NSCLC metastasis. Ski was significantly reduced in metastatic NSCLC cells or tissues when compared with non-metastatic NSCLC cells or tissues. Moreover, following TGF-β stimulation Ski-silenced A549 cells had more significant features of EMT and a higher invasive activity when compared with A549 cells overexpressing Ski. Mechanistically, Ski-silenced and overexpressed A549 cells showed an increase and a reduction in the SMAD3 phosphorylation level, respectively. This was supported by plasminogen activator inhibitor-1 (PAI-1) promoter activity obtained in Ski-silenced and overexpressed A549 cells. However, after treatment of SIS3 (inhibitor of SMAD3 phosphorylation) followed by TGF-β1 stimulation, we did not observe any effect of Ski on TGF-β-induced EMT, and invasion in Ski-silenced and overexpressed A549 cells. In conclusion, our findings suggest that Ski represses TGF-β-induced EMT and invasion by inhibiting SMAD-dependent signaling in NSCLC.

Effects of dried longan seed (Euphoria longana Lam.) extract on VEGF secretion and expression in colon cancer cells and angiogenesis in human umbilical vein endothelial cells

Angiogenesis is a critical event in cancer metastasis, via delivery of needed oxygen and nutrients to tumor cells. Anti-angiogenesis is one strategy for controlling cancer progression. We herein report anti-angiogenesis activity of dried longan seeds using colon adenocarcinoma cells (SW480 cells) and human umbilical vein endothelial cells (HUVECs). Sephadex LH-20 column chromatography was used for separate three dried longan seed fractions. We firstly evaluated vascular endothelial cell growth factor (VEGF) secretion, expression and colony formation of SW480 cells, using enzyme-linked immunosorbent assay (ELISA), Western blot analysis and soft agar assays. Meanwhile cell proliferation, gelatinase activity and tube formation of HUVECs were determined via proliferation assay, gelatin zymography and in vitro tube formation assay, respectively. The results suggest that dried longan seed fractions could be potential angiogenic inhibitors not only interruption of VEGF secretion and expression in SW480 cells but also abrogation of cell proliferation, the activity of gelatinase and tube formation of HUVECs.

Differences in the expression of epithelial–mesenchymal transition related molecules between primary tumors and pulmonary metastatic tumors in colorectal cancer

Epithelial-mesenchymal transition (EMT) is a key event in cancer metastasis. This study immunohistochemically examined the expression of EMT-related molecules in both primary colorectal cancer and pulmonary metastases, and analyzed the expression pattern. Ten patients with colorectal cancer that underwent surgical resections for both the primary tumor and metastatic pulmonary tumors were included. The expression status of EMT-related molecules was examined using immunohistochemical staining. Nine of the 10 cases maintained the expression of both E-cadherin and β-catenin in the primary site. The expression of E-cadherin and β-catenin in the pulmonary metastatic site was preserved in 10 and 12 out of 15 metastatic lesions, respectively. The EMT-related transcription factor, Twist, was positively expressed in all 10 cases, Smad interacting protein 1 (Sip1) in 9, Snail in 4 and Slug in 3 of the primary sites. On the other hand, staining for Twist, Sip1 and Snail at the metastatic pulmonary site, was negative in all 10 cases. The expression of EMT-related transcription factors in metastatic pulmonary tumors from colorectal cancer decreased in comparison to the primary tumors. These findings suggested that the expression status of EMT-related transcription factors might play an important role in the implantation of metastatic foci.

Abstract 2406: The effect of anoxia/reoxygenation on epithelial-mesenchymal transition in human colon cancer cell lines

Abstract Background and Aim: Epithelial-mesenchymal transition (EMT) is considered as crucial events in cancer metastasis. Anoxia/reoxygenation (A/R) is known to occur in cancer tissues, due to the process of angiogenesis and the change of the pressure in tissue growth. In this study, we investigated whether A/R induces EMT in the human colon cancer cells. Materials and Methods: Colon cancer cells, HT29 cells, were exposed to anoxia (2 h) followed by reoxygenation (4-22 h). To evaluate EMT, morphological changes were assessed by light microscopy, immunofluorescence and Western blot analyses. Moreover, RT-PCR for the EMT-related transcription factors (Snail and ZEB1) was performed and the activation of nuclear factor kappa B (NF-κB) was analyzed in the nuclear extracts using an ELISA method. To determine whether NF-kB was involved in A/R-induced EMT, HT-29 cells were treated with proteasome inhibitors. Results: Colon cancer cells exposed to A/R showed phenotypic changes consistent with EMT: spindle-shape and intercellular separation. The expression of E-cadherin on the cell surface and the total amount of E-cadherin protein were reduced after A/R. The EMT-related transcriptional factors such as Snail and ZEB1 were induced after exposure to A/R. Furthermore, exposure to A/R caused an activation of NF-κB and pretreatment with proteasome inhibitors significantly attenuated the effects of exposure to A/R. Conclusions: These results indicate that A/R induces EMT in human colon cancer cells through partially NF-κB dependent transcriptional pathway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2406. doi:1538-7445.AM2012-2406

Scanning electron microscopy with an ionic liquid reveals the loss of mitotic protrusions of cells during the epithelial–mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a key event in cancer metastasis and is characterized by increase in cell motility, increase in expression of mesenchymal cell markers, loss of proteins from cell-to-cell junction complexes, and changes in cell morphology. Here, the morphological effects of a representative EMT inducer, transforming growth factor (TGF)-β1, were investigated in human lung adenocarcinoma (A549) cells and pancreatic carcinoma (Panc-1) cells. TGF-β1 caused morphological changes characteristic of EMT, and immunostaining showed loss of E-cadherin from cell-to-cell junction complexes in addition to the upregulation of the mesenchymal marker vimentin. During scanning electron microscopy (SEM) with an ionic liquid, we observed EMT-specific morphological changes, including the formation of various cell protrusions. Interestingly, filopodia in mitotic cells were clearly observed by SEM, and the number of these filopodia in TFG-β1-treated mitotic cells was reduced significantly. We conclude that this reduction in such mitotic protrusions is a novel effect of TGF-β1 and may contribute to EMT.

PRSS14/Epithin is induced in macrophages by the IFN-γ/JAK/STAT pathway and mediates transendothelial migration

PRSS14/Epithin (also known as matriptase and ST14), a member of the type II transmembrane serine proteases, is primarily found in a subpopulation of normal epithelial cells and in epithelial cancers. Its known functions include maintaining the epithelial barrier, thymic development, and cancer progression. In this study, we show that several macrophage cell lines and activated bone marrow-derived macrophages also express PRSS14/Epithin. Surface expression, as well as cytoplasmic expression, was detectable upon activation by IFN-γ, but not TNF-α or TGF-β. Induction of the protein appeared to be restricted to macrophages. IFN-γ showed a biphasic regulation in RAW264.7 cells, and upregulated expression was sustained for several days. This induction by IFN-γ was partially through the increase of PRSS14/Epithin mRNA production, which is downstream of the JAK pathway, shown by the inhibition by tyrphostin AG490. Using chromatin immunoprecipitation, we verified that two sites among six putative STAT1 binding sites in the PRSS14/Epithin promoter were occupied by STAT1 upon activation. Treatment with IFN-γ enhanced the serum-triggered transendothelial migration of RAW264.7 cells, but not that of PRSS14/Epithin knock-down RAW264.7 cells, although they express multiple markers such as ICAM1, CD80, and CD40 at normal levels. These data strongly suggest that PRSS14/Epithin plays an important role in the transendothelial migration of activated macrophages in the inflammatory microenvironment, and the mode of action is similar to the events in cancer metastasis.

Two-Photon Intravital Multicolor Imaging Combined with Inducible Gene Expression to Distinguish Metastatic Behavior of Breast Cancer Cells In Vivo

PurposeThe aim of this study is to use multicolor intravital imaging together with an inducible cell model to compare metastatic behavior of control and genetically modified breast cancer cell populations within the intact primary tumor of a mouse.ProcedureGFP-MTLn3-ErbB1 cells were generated with doxycycline-regulated conditional transgene expression using lentiviral TREAutoR3-cyan fluorescent protein (CFP). CFP expression together with tumor cell motility is monitored in vitro and in vivo.ResultsEffective and tight control of doxycycline-induced CFP expression was observed both in vitro and in vivo. Intravital multiphoton microscopy on intact orthotopic tumors allowed a clear discrimination between GFP-only and (GFP + CFP) cell populations, which enables direct comparison of the motility behavior of two different cell populations in the same microenvironment in vivo.ConclusionsThis system is robust and versatile for conditional gene expression and can be used to study the role of individual candidate metastasis genes in vitro and in vivo. This technology will allow investigations of cellular events in cancer metastasis and in particular intravasation within a primary tumor.Electronic supplementary materialThe online version of this article (doi:10.1007/s11307-010-0307-z) contains supplementary material, which is available to authorized users.

Cellular Magnetic Resonance Imaging: In Vivo Imaging of Melanoma Cells in Lymph Nodes of Mice

Metastasis is responsible for most deaths due to malignant melanoma. The clinical significance of micrometastases in the lymph is a hotly debated topic, but an improved understanding of the lymphatic spread of cancer remains important for improving cancer survival. Cellular magnetic resonance imaging (MRI) is a newly emerging field of imaging research that is expected to have a large impact on cancer research. In this study, we demonstrate the cellular MRI technology required to reliably image the lymphatic system in mice and to detect iron-labeled metastatic melanoma cells within the mouse lymph nodes. Melanoma cells were implanted directly into the inguinal lymph nodes in mice, and micro-MRI was performed using a customized 1.5-T clinical MRI system. We show cell detection of as few as 100 iron-labeled cells within the lymph node, with injections of larger cell numbers producing increasingly obvious regions of signal void. In addition, we show that cellular MRI allows monitoring of the fate of these cells over time as they develop into intranodal tumors. This technology will allow noninvasive investigations of cellular events in cancer metastasis within an entire animal and will facilitate progress in understanding the mechanisms of metastasis within the lymphatic system.

Involvement of E-cadherin, β-catenin, Cdc42 and CXCR4 in the progression and prognosis of cutaneous melanoma

A key event in cancer metastasis is the migration of tumour cells from their original location to a secondary site. The development of melanoma may be viewed as a consequence of the disruption of homeostatic mechanisms in the skin of the original site. To investigate whether dysregulation of cell motility (Cdc42 expression), escaping the control of cell-cell and cell-matrix interactions (E-cadherin, beta-catenin expression), enhances melanoma progression, and whether chemokine receptors (CXCR4) mediate cell migration and activation during invasion and metastasis development. The immunohistochemical expression of Cdc42, E-cadherin, beta-catenin and CXCR4 was investigated in 30 patients with surgically treated nodular melanoma, 18 alive and disease free and 12 with a fatal outcome due to metastatic disease. E-cadherin expression was significantly reduced (P < 0.05) and cytoplasmic beta-catenin was increased in the patients who had died compared with disease-free individuals, while membrane expression of beta-catenin was similar in the two groups. Patients with fatal outcome had increased Cdc42 (P < 0.01) and CXCR4 (P < 0.05). In this group a positive correlation was found between melanocytic Cdc42 expression and Breslow thickness (r = 0.598, P < 0.05) and between CXCR4 expression and Breslow thickness (r = 0.583, P < 0.05). Findings suggest that primary cutaneous melanoma with a high Breslow thickness is characterized by tumour cells with high motility and invasion ability, in line with the hypothesis that low E-cadherin levels and overexpression of Cdc42 and CXCR4 could be prognostic markers of poor outcome.