Prox-1 promotes invasion of kaposiform hemangioendotheliomas

A Xenograft Model of Kaposiform Hemangioendothelioma in Nude Mice Recapitulates Kasabach-Merritt Phenomenon

BACKGROUND

Kasabach-Merritt phenomenon (KMP) is characterized by profound thrombocytopenia and consumptive coagulopathy associated with vascular tumors, such as Kaposiform hemangioendothelioma (KHE). The pathogenesis of KMP remains unclear and its treatment is challenging. In this study, we tried to establish an animal model of KMP, which may facilitate the research on the etiology and new treatment.

METHODS

A fresh sample of KHE from a one-month-old female infant with KMP was scissored into pieces and transplanted subcutaneously into the back of the nude mice. Blood routine examination was performed before the transplantation and 2, 4, 8, 12, and 16 weeks after the transplantation. Transplanted tumors were harvested 2, 4, 8, 12, and 16 weeks after the transplantation. H-E staining, immunohistochemistry staining of cluster of differentiation 31 (CD31) and alpha-smooth muscle actin (α-SMA), and ultrastructural observation were performed on the plugs.

RESULTS

Blood test showed a significant decrease in the number of platelets 2 weeks after transplantation. The number of platelets showed an overall trend of recovery from 2 weeks despite a slight decrease at 12 weeks after transplantation. There was no significant difference in the platelet count at 16 weeks after transplantation compared with the original state. H-E staining showed abundant irregular blood sinuses in the transplanted tumors with plenty of blood cells 2 weeks after the transplantation. 4, 8, and 12 weeks after transplantation, the density of blood sinuses decreased progressively. 16 weeks after transplantation, the plugs involuted into fibrous tissue. Immunohistochemistry staining showed the positive expression of CD31 in the endothelial cells and α-SMA in the perivascular cells. Ultrastructural observation also showed the features of KHE and progressive evolution of the tumors.

CONCLUSIONS

We successfully established an experimental model of KMP by the xenograft of KHE in nude mice, which manifested profound thrombocytopenia and typical pathological structure.

Sirolimus for kaposiform hemangioendothelioma: Potential mechanisms of action and resistance

Kaposiform hemangioendotheliomas (KHEs) are vascular tumors that are considered borderline or locally aggressive and may lead to lethal outcomes. Traditional therapies, such as surgery and embolization, may be insufficient or technically impossible for patients with KHE. Sirolimus (or rapamycin), a specific inhibitor of mechanistic target of rapamycin, has recently been demonstrated to be very useful in the treatment of KHEs. Here, we highlight recent substantial progress regarding the effects of sirolimus on KHEs and discuss the potential mechanisms of action of sirolimus in treating this disease. The prevention of platelet activation and inflammation, along with antiangiogenic effects, the inhibition of lymphangiogenesis, the attenuation of fibrosis, or a combination of all these effects, may be responsible for the therapeutic effects of sirolimus. In addition, the mechanism of sirolimus resistance in some KHE patients is discussed. Finally, we review the somatic mutations that have recently been identified in KEH lesions, and discuss the potential of novel therapeutic targets based on these further understandings of the cellular and molecular pathogenesis of KHE.

Fucoidan suppresses proliferation and epithelial-mesenchymal transition process via Wnt/β-catenin signalling in hemangioma

Hemangioma is a common benign tumour that usually occurs on the skin of the head and neck, particularly among infants. The current clinical treatment against hemangioma is surgery excision, however, application of drug is a safer and more economical therapy for children suffering from hemangioma. As a natural sulfated polysaccharide rich in brown algae, fucoidan is widely recognized for anti-tumour bioactivity and dosage safety in humans. This study aims to demonstrate the anti-tumour effect and underlying mechanism of fucoidan against hemangioma in vivo and in vitro. We investigated the effects of fucoidan by culturing hemangioma cells in vitro and treating BALB/c mice bearing with hemangioma. At first, we measured the cell proliferation and migration ability through in vitro experiments. Then, we tested the expression of epithelial-mesenchymal transition (EMT) and Wnt/β-catenin pathway-related biomarkers by western blot and qPCR. Furthermore, we applied β-catenin-specific inhibitor, XAV939, to determine whether fucoidan suppressed EMT via the Wnt/β-catenin pathway in hemangioma cells. In vivo experiments, we applied oral gavage of fucoidan to treat EOMA-bearing mice, along with evaluating the safety and efficacy of fucoidan. We found that fucoidan remarkably inhibits the proliferation and EMT ability of hemangioma cells, which is dependent on the Wnt/β-catenin pathway. These results suggest that fucoidan exhibits tumour inhibitory effect on aggressive hemangioma via regulating the Wnt/β-catenin signalling pathway both in vitro and in vivo, providing a new potent drug candidate for treating hemangioma.

Prox1 Suppresses Proliferation and Drug Resistance of Retinoblastoma Cells via Targeting Notch1

OBJECTIVE

Retinoblastoma (RB) is a prevalent type of eye cancer in youngsters. Prospero homeobox 1 (Prox1) is a homeobox transcriptional repressor and downstream target of the proneural gene that is relevant in lymphatic, hepatocyte, pancreatic, heart, lens, retinal, and cancer cells. The goal of this study was to investigate the role of Prox1 in RB cell proliferation and drug resistance, as well as to explore the underlying Notch1 mechanism.

METHODS

Human RB cell lines (SO-RB50 and Y79) and a primary human retinal microvascular endothelial cell line (ACBRI-181) were used in this study. The expression of Prox1 and Notch1 mRNA and protein in RB cells was detected using quantitative real time-polymerase chain reaction (RT-qPCR) and Western blotting. Cell proliferation was assessed after Prox1 overexpression using the Cell Counting Kit-8 and the MTS assay. Drug-resistant cell lines (SO-RB50/vincristine) were generated and treated with Prox1 to investigate the role of Prox1 in drug resistance. We employed pcDNA-Notch1 to overexpress Notch1 to confirm the role of Notch1 in the protective function of Prox1. Finally, a xenograft model was constructed to assess the effect of Prox1 on RB in vivo.

RESULTS

Prox1 was significantly downregulated in RB cells. Overexpression of Prox1 effectively decreased RB cell growth while increasing the sensitivity of drug-resistant cells to vincristine. Notch1 was involved in Prox1's regulatory effects. Notch1 was identified as a target gene of Prox1, which was found to be upregulated in RB cells and repressed by increased Prox1 expression. When pcDNA-Notch1 was transfected, the effect of Prox1 overexpression on RB was removed. Furthermore, by downregulating Notch1, Prox1 overexpression slowed tumor development and increased vincristine sensitivity in vivo.

CONCLUSION

These data show that Prox1 decreased RB cell proliferation and drug resistance by targeting Notch1, implying that Prox1 could be a potential therapeutic target for RB.

Tissue nanotransfection causes tumor regression by its effect on nanovesicle cargo that alters microenvironmental macrophage state

Extracellular vesicles (EVs) are nanovesicles released by all eukaryotic cells. This work reports the first nanoscale fluorescent visualization of tumor-originating vesicles bearing an angiogenic microRNA (miR)-126 cargo. In a validated experimental model of lethal murine vascular neoplasm, tumor-originating EV delivered its miR-126 cargo to tumor-associated macrophages (TAMs). Such delivery resulted in an angiogenic (LYVE+) change of state in TAM that supported tumor formation. Study of the trafficking of tumor-originating fluorescently tagged EV revealed colocalization with TAM demonstrating uptake by these cells. Ex vivo treatment of macrophages with tumor-derived EVs led to gain of tumorigenicity in these isolated cells. Single-cell RNA sequencing of macrophages revealed that EV-borne miR-126 characterized the angiogenic change of state. Unique gene expression signatures of specific macrophage clusters responsive to miR-126-enriched tumor-derived EVs were revealed. Topical tissue nanotransfection (TNT) delivery of an oligonucleotide comprising an anti-miR against miR-126 resulted in significant knockdown of miR-126 in the tumor tissue. miR-126 knockdown resulted in complete involution of the tumor and improved survival rate of tumor-affected mice. This work identifies a novel tumorigenic mechanism that relies on tumorigenic state change of TAM caused by tumor-originating EV-borne angiomiR. This disease process can be effectively targeted by topical TNT of superficial tumors.

SHH and Notch regulate SOX9+ progenitors to govern arcuate POMC neurogenesis

Pro-opiomelanocortin (POMC)-expressing neurons in the hypothalamic arcuate nucleus (ARC) play key roles in feeding and energy homoeostasis, hence their development is of great research interest. As the process of neurogenesis is accompanied by changes in adhesion, polarity, and migration that resemble aspects of epithelial-to-mesenchymal transitions (EMTs), we have characterised the expression and regulation within the prospective ARC of transcription factors with context-dependent abilities to regulate aspects of EMT. Informed by pseudotime meta-analysis of recent scRNA-seq data, we use immunohistochemistry and multiplex in situ hybridisation to show that SOX2, SRY-Box transcription factor 9 (SOX9), PROX1, Islet1 (ISL1), and SOX11 are sequentially expressed over the course of POMC neurogenesis in the embryonic chick. Through pharmacological studies ex vivo, we demonstrate that while inhibiting either sonic hedgehog (SHH) or Notch signalling reduces the number of SOX9+ neural progenitor cells, these treatments lead, respectively, to lesser and greater numbers of differentiating ISL1+/POMC+ neurons. These results are consistent with a model in which SHH promotes the formation of SOX9+ progenitors, and Notch acts to limit their differentiation. Both pathways are also required to maintain normal levels of proliferation and to suppress apoptosis. Together our findings demonstrate that hypothalamic neurogenesis is accompanied by dynamic expression of transcription factors (TFs) that mediate EMTs, and that SHH and Notch signalling converge to regulate hypothalamic cellular homoeostasis.

Rapamycin induces autophagy and apoptosis in Kaposiform hemangioendothelioma primary cells in vitro

BACKGROUND

Rapamycin has been recommended to treat Kaposiform hemangioendothelioma (KHE) with Kasabach-Merritt phenomenon (KMP), but the underlying mechanism of the clinical effect has not been established. Therefore, we determined rapamycin cytotoxicity on KHE cells in vitro and the underlying mechanism.

METHODS

KHE primary cells were derived from a tumor specimen and treated with rapamycin. Immunofluorescence was applied to identify the cells. Cell viability was measured using the Cell Counting Kit-8 (CCK-8) assay. Cell cycle and apoptosis were assessed using flow cytometry (FCM). Western blots (WB) were performed to determine phosphorylation of mammalian target of rapamycin (mTOR), p70 S6 kinase (S6K1), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), as well light chain 3 (LC3) expression.

RESULTS

Rapamycin inhibited the growth of KHE primary cells in a dose- and time-dependent manner. Cell cycle progression was arrested in the G0/G1 phase and apoptosis was induced. WB results showed that LC3-II/I expression was significantly elevated in KHE primary cells treated with rapamycin, while the level of p-mTOR, p-S6K1, and p-4E-BP1 expression was reduced. LC3 fluorescent spots were increased in the rapamycin treatment group.

CONCLUSIONS

Rapamycin inhibited KHE primary cell proliferation, induced apoptosis and autophagy, and blocked the mTOR signaling pathway.

β-catenin plus PROX1 immunostaining stratifies disease progression and patient survival in neoadjuvant-treated pancreatic cancer

BACKGROUND

Wnt/β-catenin signaling is a highly conserved signaling pathway that regulates the transcription factor PROX1. The role of β-catenin and PROX1 in pancreatic cancer is ambiguous, as some studies have associated their expression with tumor regression and some with tumor progression.

OBJECTIVE

We have investigated their expression in surgically treated pancreatic cancer patients receiving neoadjuvant therapy (NAT), and patients treated upfront with surgery (US). We furthermore compared the expression of β-catenin and PROX1 between patients who had a good or poor response to NAT.

METHODS

We evaluated β-catenin and PROX1 expression through immunohistochemistry in 88 neoadjuvant and 144 upfront surgery patients by scoring the intensity of the immunopositivity as 0-3, corresponding to negative, weak, moderate, or strong. We developed a six-tier grading scheme for the neoadjuvant responses by analyzing the remaining tumor cells in surgical specimen histological sections.

RESULTS

Strong β-catenin immunopositivity associated with improved survival in the patients with good NAT-response (≤10% residual tumor cells) (Hazard ratio [HR] 0.26 95%, confidence interval [CI] 0.07-0.88 p = 0.030). Additionally, the combined moderate β-catenin and PROX1 expression associated with improved survival (HR 0.20 95% CI 0.05-0-76 p = 0.018) among the good responders. Among the patients with a poor NAT-response (> 10% residual tumor cells), both strong β-catenin immunopositivity and strong combined β-catenin and PROX1 associated with shorter survival (HR 2.03 95% CI 1.16-3.55 p = 0.013, and HR 3.1 95% CI 1.08-8.94 p = 0.03, respectively). PROX1 alone was not associated with survival.

CONCLUSIONS

Strong β-catenin immunopositivity and combined strong or moderate β-catenin and PROX1 immunopositivity associated with improved survival among the good NAT-responders and worse survival among the poor NAT-responders.

Overexpression Prox1 in HemECs resembles Kaposiform hemangioendothelioma and cytotoxicity of sirolimus in vitro

BACKGROUND

Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor that occurs in children. Prox1 is a specific lymphatic marker for KHE. We intended to establish a Prox1 transgenic cell line resembling KHE and investigate the mechanism of sirolimus in treating KHE.

METHODS

Prox1 was stably expressed in infantile hemangioma cell HemECs. RT-qPCR and Western blot were conducted to measure the expression of target genes. CCK-8, EdU assay, and cell cycle analysis were conducted to detect cell proliferation. Wound healing and transwell assay were used to evaluate cell migration and invasion.

RESULTS

Both mRNA and protein levels of Prox1, LYVE-1, Podoplanin were upregulated in Prox1⁺ HemECs. An acceleration of cell growth and a rise in migration and invasion were observed with Prox1 overexpression. Sirolimus inhibited cell proliferation, promoted apoptosis and led to G1 phase arrest in Prox1⁺ HemECs. The expression of p-mTOR, p-4EBP1, and p-P70S6K decreased and the ratio of LC-3 II/LC-3 I elevated after treatment of sirolimus.

CONCLUSIONS

Stable overexpression of Prox1 in HemECs induced a lymphatic endothelial reprogramming, and enhanced aggressive biological effects, partly resembled the invasion of KHE, and could serve as a novel model for KHE. Sirolimus may block mTOR-mediated pathways and induced autophagy in KHE.

The Impact of Transcription Factor Prospero Homeobox 1 on the Regulation of Thyroid Cancer Malignancy

Transcription factor Prospero homeobox 1 (PROX1) is continuously expressed in the lymphatic endothelial cells, playing an essential role in their differentiation. Many reports have shown that PROX1 is implicated in cancer development and acts as an oncoprotein or suppressor in a tissue-dependent manner. Additionally, the PROX1 expression in many types of tumors has prognostic significance and is associated with patient outcomes. In our previous experimental studies, we showed that PROX1 is present in the thyroid cancer (THC) cells of different origins and has a high impact on follicular thyroid cancer (FTC) phenotypes, regulating migration, invasion, focal adhesion, cytoskeleton reorganization, and angiogenesis. Herein, we discuss the PROX1 transcript and protein structures, the expression pattern of PROX1 in THC specimens, and its epigenetic regulation. Next, we emphasize the biological processes and genes regulated by PROX1 in CGTH-W-1 cells, derived from squamous cell carcinoma of the thyroid gland. Finally, we discuss the interaction of PROX1 with other lymphatic factors. In our review, we aimed to highlight the importance of vascular molecules in cancer development and provide an update on the functionality of PROX1 in THC biology regulation.

Kaposiform hemangioendothelioma: current knowledge and future perspectives

Kaposiform hemangioendothelioma (KHE) is a rare vascular neoplasm with high morbidity and mortality. The initiating mechanism during the pathogenesis of KHE has yet to be discovered. The main pathological features of KHE are abnormal angiogenesis and lymphangiogenesis. KHEs are clinically heterogeneous and may develop into a life-threatening thrombocytopenia and consumptive coagulopathy, known as the Kasabach-Merritt phenomenon (KMP). The heterogeneity and the highly frequent occurrence of disease-related comorbidities make the management of KHE challenging. Currently, there are no medications approved by the FDA for the treatment of KHE. Multiple treatment regimens have been used with varying success, and new clinical trials are in progress. In severe patients, multiple agents with variable adjuvant therapies are given in sequence or in combination. Recent studies have demonstrated a satisfactory efficacy of sirolimus, an inhibitor of mammalian target of rapamycin, in the treatment of KHE. Novel targeted treatments based on a better understanding of the pathogenesis of KHE are needed to maximize patient outcomes and quality of life. This review summarizes the epidemiology, etiology, pathophysiology, clinical features, diagnosis and treatments of KHE. Recent new concepts and future perspectives for KHE will also be discussed.

PRC1 preserves epidermal tissue integrity independently of PRC2

Cohen et al. show that, despite extensive genomic cobinding, PRC1 is essential for epidermal integrity, whereas PRC2 is dispensable.

Polycomb-repressive complex 1 (PRC1) and PRC2 are critical chromatin regulators of gene expression and tissue development. Here, we show that despite extensive genomic cobinding, PRC1 is essential for epidermal integrity, whereas PRC2 is dispensable. Loss of PRC1 resulted in blistering skin, reminiscent of human skin fragility syndromes. Conversely, PRC1 does not restrict epidermal stratification during skin morphogenesis, whereas PRC2 does. Molecular dissection demonstrated that PRC1 functions with PRC2 to silence/dampen expression of adhesion genes. In contrast, PRC1 promotes expression of critical epidermal adhesion genes independently of PRC2-mediated H3K27me3. Together, we demonstrate a functional link between epigenetic regulation and skin diseases.

The role of prospero homeobox 1 (PROX1) expression in follicular thyroid carcinoma cells

The prospero homeobox 1 (Prox1) transcription factor is a key player during embryogenesis and lymphangiogenesis. Altered Prox1 expression has been found in a variety of human cancers, including papillary thyroid carcinoma (PTC). Interestingly, Prox1 may exert tumor suppressive or tumor promoting effect, depending on the tissue context. In this study, we have analyzed Prox1 expression in normal and malignant human thyroid carcinoma cell lines. Moreover, we determined the effect of Prox1 silencing and overexpression on the cellular processes associated with the metastatic potential of tumor cells: proliferation, migration, invasion, apoptosis and anchorage-independent growth, in the follicular thyroid carcinoma (FTC) FTC-133 cell line. We found that Prox1 expression was significantly higher in FTC-derived cells than in PTC-derived cells and normal thyroid, and it was associated with the PI3K/Akt signaling pathway. In the FTC-133 cells, it was associated with cell invasive potential, motility and wound closure capacities, but not with proliferation or apoptosis. Modifying Prox1 expression also induced substantial changes in the cytoskeleton structure and cell morphology. In conclusion, we have shown that Prox1 plays an important role in the development of FTC and that its suppression prevents, whereas its overexpression promotes, the malignant behavior of thyroid follicular cancer cells.

The optimum marker for the detection of lymphatic vessels

Podoplanin, lymphatic vessel endothelial hyaluronic acid receptor-1, prospero-related homeobox-1 and vascular endothelial growth factor receptor 3 have been demonstrated to have crucial roles in the development of the lymphatic system and lymphangiogenesis process by combining with their corresponding receptors. Thus, the four markers have been widely used in labelling lymphatic vessels for the detection of lymphangiogenesis and lymphatic vessel invasion. Numerous authors have aimed to identify the roles of these four markers in the lymphatic system and the mechanisms have been partly clarified at the molecular level. The aim of the present review was to comprehensively clarify the characteristics and latent action modes of the four markers in order to determine which is the best one for the detection of lymphangiogenesis and lymphatic vessel invasion.

Integrin β3/Akt signaling contributes to platelet-induced hemangioendothelioma growth

Hemangioendothelioma (HE) is a type of angiomatous lesions that features endothelial cell proliferation. Understanding the mechanisms orchestrating HE angiogenesis can provide therapeutic insights. It has been shown that platelets can support normal and malignant endothelial cells during angiogenesis. Using the mouse endothelial-derived EOMA cell line as a model of HE, we explored the regulatory effect of platelets. We found that platelets stimulated EOMA proliferation but did not mitigate apoptosis. Furthermore, direct platelet-EOMA cell contact was required and the proliferation was mediated via integrin β3/Akt signaling in EOMA cells. SiRNA knockdown of integrin β3 and inhibition of Akt activity significantly abolished platelet-induced EOMA cell proliferation in vitro and tumor development in vivo. These results provide a new mechanism by which platelets support HE progression and suggest integrin β3 as a potential target to treat HE.

Phytochemical Inhibition of Multidrug Resistance Protein-1 as a Therapeutic Strategy for Hemangioendothelioma

AIMS

Hemangiomas are endothelial cell tumors and the most common soft tissue tumors in infants. They frequently cause deformity and can cause death. Current pharmacologic therapies have high-risk side-effect profiles, which limit the number of children who receive treatment. The objectives of this work were to identify the mechanisms through which standardized berry extracts can inhibit endothelial cell tumor growth and test these findings in vivo.

RESULTS

EOMA cells are a validated model that generates endothelial cell tumors when injected subcutaneously into syngeneic (129P/3) mice. EOMA cells treated with a blend of powdered natural berry extracts (NBE) significantly inhibited activity of multidrug resistance protein-1 (MRP-1) compared to vehicle controls. This resulted in nuclear accumulation of oxidized glutathione (GSSG) and apoptotic EOMA cell death. When NBE-treated EOMA cells were injected into mice, they generated smaller tumors and had a higher incidence of apoptotic cell death compared to vehicle-treated EOMA cells as demonstrated by immunocytochemistry. Kaplan-Meier survival curves for tumor-bearing mice showed that NBE treatment significantly prolonged survival compared to vehicle-treated controls.

INNOVATION

These are the first reported results to show that berry extracts can inhibit MRP-1 function that causes apoptotic tumor cell death by accumulation of GSSG in the nucleus of EOMA cells where NADPH oxidase is hyperactive and causes pathological angiogenesis.

CONCLUSIONS

These findings indicate that berry extract inhibition of MRP-1 merits consideration and further investigation as a therapeutic intervention and may have application for other cancers with elevated MRP-1 activity. Antioxid. Redox Signal. 26, 1009-1019.

MicroRNA-181a inhibits tumor proliferation, invasiveness, and metastasis and is downregulated in gastric cancer

MicroRNAs (miRNAs) play crucial roles in the development and progression of human cancers, including gastric cancer. The discovery of miRNAs may provide a new and powerful tool for studying the mechanism, diagnosis, and treatment of gastric cancer. Here we show that miR-181a levels were significantly downregulated in gastric cancer tissues compared with the adjacent normal regions in 80 paired samples. Moreover, the lower levels of miR-181a were associated with the pM or pTNM stage in clinical gastric cancer patients. In addition, the ectopic expression of miR-181a in the gastric cancer cell line HGC-27 inhibited cell proliferation, cell migration, and invasion by directly interacting with the mRNA encoding the oncogenic factor Prox1. Taken together, our results indicate that miR-181a might act as a tumor suppressor in gastric cancer, which may provide a novel diagnostic and therapeutic option for human gastric cancer in the near future.

PROX1 Promotes Secretory Granule Formation in Medullary Thyroid Cancer Cells

Mechanisms of endocrine secretory granule (SG) formation in thyroid C cells and medullary thyroid cancer (MTC) cells have not been fully elucidated. Here we directly demonstrated that PROX1, a developmental homeobox gene, is transcriptionally involved in SG formation in MTC, which is derived from C cells. Analyses using gene expression databases on web sites revealed that, among thyroid cancer cells, MTC cells specifically and highly express PROX1 as well as several SG-forming molecule genes. Immunohistochemical analyses showed that in vivo MTC and C cells expressed PROX1, although follicular thyroid cancer and papillary thyroid cancer cells, normal follicular cells did not. Knockdown of PROX1 in an MTC cells reduced SGs detected by electron microscopy, and decreased expression of SG-related genes (chromogranin A, chromogranin B, secretogranin II, secretogranin III, synaptophysin, and carboxypeptidase E). Conversely, the introduction of a PROX1 transgene into a papillary thyroid cancer and anaplastic thyroid cancer cells induced the expression of SG-related genes. Reporter assays using the promoter sequence of chromogranin A showed that PROX1 activates the chromogranin A gene in addition to the known regulatory mechanisms, which are mediated via the cAMP response element binding protein and the repressor element 1-silencing transcription factor. Furthermore, chromatin immunoprecipitation-PCR assays demonstrated that PROX1 binds to the transcriptional regulatory element of the chromogranin A gene. In conclusion, PROX1 is an important regulator of endocrine SG formation in MTC cells.

Aberrant Activation of Notch Signaling Inhibits PROX1 Activity to Enhance the Malignant Behavior of Thyroid Cancer Cells

Papillary thyroid cancer (PTC) is one of the most common endocrine malignancies associated with significant morbidity and mortality. Although multiple studies have contributed to a better understanding of the genetic alterations underlying this frequently arising disease, the downstream molecular effectors that impact PTC pathogenesis remain to be further defined. Here, we report that the regulator of cell fate specification, PROX1, becomes inactivated in PTC through mRNA downregulation and cytoplasmic mislocalization. Expression studies in clinical specimens revealed that aberrantly activated NOTCH signaling promoted PROX1 downregulation and that cytoplasmic mislocalization significantly altered PROX1 protein stability. Importantly, restoration of PROX1 activity in thyroid carcinoma cells revealed that PROX1 not only enhanced Wnt/β-catenin signaling but also regulated several genes known to be associated with PTC, including thyroid cancer protein (TC)-1, SERPINA1, and FABP4. Furthermore, PROX1 reexpression suppressed the malignant phenotypes of thyroid carcinoma cells, such as proliferation, motility, adhesion, invasion, anchorage-independent growth, and polyploidy. Moreover, animal xenograft studies demonstrated that restoration of PROX1 severely impeded tumor formation and suppressed the invasiveness and the nuclear/cytoplasmic ratio of PTC cells. Taken together, our findings demonstrate that NOTCH-induced PROX1 inactivation significantly promotes the malignant behavior of thyroid carcinoma and suggest that PROX1 reactivation may represent a potential therapeutic strategy to attenuate disease progression.

Long non-coding RNA growth arrest-specific transcript 5 in tumor biology

The recognition of the biological relevance of long non-coding RNA (lncRNA) molecules has only recently been recognized as one of the most significant advances in contemporary molecular biology. A growing body of evidence indicates that lncRNAs act not only as the intermediary between DNA and protein but also as significant protagonists of cellular functions. The dysregulation of lncRNAs has increasingly been linked to numerous human diseases, particularly cancers. Recent studies have demonstrated that the lncRNA growth arrest-specific transcript 5 (GAS5) was pervasively downexpressed in most human cancers compared with non-cancerous adjacent tissues including gastric, breast, lung and prostate cancer. In addition, patients with decreased GAS5 expression have a significantly poorer prognosis than those with higher expression. Furthermore, GAS5 is involved in the control of cell apoptosis, proliferation, metastasis, angiogenesis, DNA repair and tumor cell metabolism. This review provides an overview of the current knowledge concerning the role of GAS5 in tumor expression and biology function.

PROX1 gene is differentially expressed in oral cancer and reduces cellular proliferation

Homeobox genes are a family of transcription factors that play a pivotal role in embryogenesis. Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor gene or oncogene in various types of cancer, including oral squamous cell carcinoma (OSCC). We have previously identified PROX1 as a downregulated gene in OSCC. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of OSCC cells. PROX1 mRNA and protein expression levels were first investigated in 40 samples of OSCC and in nontumor margins. Methylation and amplification analysis was also performed to assess the epigenetic and genetic mechanisms involved in controlling PROX1 expression. OSCC cell line SCC9 was also transfected to stably express the PROX1 gene. Next, SCC9-PROX1-overexpressing cells and controls were subjected to proliferation, differentiation, apoptosis, migration, and invasion assays in vitro. OSCC samples showed reduced PROX1 expression levels compared with nontumor margins. PROX1 amplification was associated with better overall survival. PROX1 overexpression reduces cell proliferation and downregulates cyclin D1. PROX1-overexpressing cells also exhibited reduced CK18 and CK19 expression and transcriptionally altered the expression of WISP3, GATA3, NOTCH1, and E2F1. Our results suggest that PROX1 functions as a tumor suppressor gene in oral carcinogenesis.

Impact of an altered PROX1 expression on clinicopathology, prognosis and progression in renal cell carcinoma

The transcription factor PROX1 (prospero homeobox 1) has a critical role in the development of various organs, and has been implicated in both oncogenic and tumor-suppressive functions in human cancers. However, the role of PROX1 in the development of renal cell carcinomas (RCCs) has not yet been studied. Here, we reported that PROX1 expression was decreased in human RCC tissues compared with adjacent normal tissues. In RCC tissues, however, poorly differentiated RCC expressed higher PROX1 levels compared with well-differentiated RCC. In addition, the PROX1 immunostaining levels were positively correlated with tumor nuclear grade and lymph node metastasis. Further, high PROX1 expression indicated poor survival for patients. These findings imply that in the different developmental stages of RCC, PROX1 may exert distinct functions according to the specific microenvironment of tumor. Moreover, in vitro experiments revealed that PROX1 overexpression enhanced the proliferation and migration of RCC cells; conversely, PROX1 depletion by siRNA attenuated the proliferation and migration of RCC cells. Collectively, these observations suggest that PROX1 plays an important role in RCC development and progression, and PROX1 may be a novel target for prevention and treatment of RCC.

Prox1 and FOXC2 act as regulators of lymphangiogenesis and angiogenesis in oral squamous cell carcinoma

Prospero homeobox 1 (Prox1) and forkhead box (FOX) C2 regulate angiogenesis and/or lymphangiogenesis. However, the detailed role and function of Prox1 and FOXC2 in cancer remains controversial. In the present study, we examined the expression of Prox1 and FOXC2 proteins in specimens from 163 cases with oral squamous cell carcinoma (OSCC). Furthermore, the role of Prox1 and FOXC2 in cancer cell growth and invasion was evaluated in cultured OSCC cells. Prox1 expression was significantly associated with local progression of the tumor (P = 0.0023), clinical stage (P<0.0001), lymphovessel density (LVD) (P<0.0001), nodal metastasis (P<0.0001), and worse prognosis (P<0.0001). Immunoreactivity of FOXC2 was strongly correlated with microvessel density (MVD) (P<0.0001) and poor prognosis (P = 0.0076). In vitro analysis demonstrated that Prox1 regulates cell growth, proliferation, invasion, and lymphangiogenesis by activating vascular endothelial growth factor (VEGF)-C expression. Furthermore, FOXC2 enhanced the expression level of Prox1 and promoted angiogenesis by enhancement of VEGF-A expression. Our results suggested that Prox1 and FOXC2 play key roles in OSCC progression and that further studies focusing on these proteins may yield useful insights for diagnosis and therapy of OSCC.

Transcription factor PROX1: its role in development and cancer

The homeobox gene PROX1 is critical for organ development during embryogenesis. The Drosophila homologue, known as prospero has been shown to act as a tumor suppressor by controlling asymmetric cell division of neuroblasts. Likewise, alterations in PROX1 expression and function are associated with a number of human cancers including hematological malignancies, carcinomas of the pancreas, liver and the biliary system, sporadic breast cancer, Kaposiform hemangioendothelioma, colon cancer, and brain tumors. PROX1 is involved in cancer development and progression and has been ascribed both tumor suppressive and oncogenic properties in a variety of different cancer types. However, the exact mechanisms through which PROX1 regulates proliferation, migration, and invasion of cancer cells are by large unknown. This review provides an update on the role of PROX1 in organ development and on its emerging functions in cancer, with special emphasis on the central nervous system and glial brain tumors.

Expression of PROX-1 in oral Kaposi's sarcoma spindle cells

BACKGROUND

The histogenesis of neoplastic spindle cells of Kaposi's sarcoma is still uncertain, but some studies consider it a lymphatic vessel differentiation. Prox-1 is a nuclear transcription factor that plays a major role during embryonic lymphangiogenesis, and it has been considered a specific and sensitive lymphatic endothelial cell marker. The aim of this study was to determine the expression of Prox-1 in oral Kaposi's sarcoma comparing the results with oral benign vascular tumors including capillary hemangiomas and pyogenic granulomas.

METHODS

Expression of Prox-1 and HHV-8 was evaluated by immunohistochemistry in 30 oral Kaposi's sarcoma, 5 oral capillary hemangiomas, and 10 oral pyogenic granulomas. The labeling index was expressed as the percentage of positive cells for each case studied. Statistical comparison was performed using the Wilcoxon-Mann-Whitney rank sum test.

RESULTS

Twenty-eight (93.3%) and 30 oral Kaposi's sarcoma cases were positive for Prox-1 and HHV-8, respectively, while all oral benign vascular tumors were negative for these markers. The number of Prox-1 and HHV-8 oral Kaposi's sarcoma-positive cells increased significantly from patch/plaque to nodular histological stages.

CONCLUSION

The expression of Prox-1 in the neoplastic spindle cells supports the view of a lymphatic differentiation in oral Kaposi's sarcoma. Prox-1 may also be involved in the pathogenesis of oral Kaposi's sarcoma as the number of positive spindle cells increased progressively from patch to nodular stages and could be eventually useful as an additional diagnostic tool for differential diagnosis between oral Kaposi's sarcoma and benign oral vascular lesions.

Hemangioendothelioma

Hemangioendothelioma is the term used to name those vascular neoplasms that show a borderline biological behavior, intermediate between entirely benign hemangiomas and highly malignant angiosarcomas. Although originally spindle cell hemangioendothelioma was proposed as a specific clinicopathologic variant of hemangioendothelioma, currently, it is considered as an entirely benign lesion, and thus, the name spindle cell hemangioma seems to be the most accurate for this lesion. Authentic hemangioendotheliomas involving the skin and soft tissues include papillary intralymphatic angioendothelioma (also known as Dabska tumor), retiform hemangioendothelioma, kaposiform hemangioendothelioma, epithelioid hemangioendothelioma, pseudomyogenic hemangioendothelioma (also known as epithelioid sarcoma-like hemangioendothelioma), and composite hemangioendothelioma. Each of these neoplasms exhibit characteristic histopathologic features. The most characteristic finding of papillary intralymphatic hemangioendothelioma consists of papillary tufts, with a central hyaline core lined by hobnail-like endothelial cells protruding into the lumina. Retiform hemangioendothelioma is an infiltrative neoplasm composed of elongated arborizing vessels, arranged in an anastomosing pattern that resembles that of the rete testis, and lined by a single layer of hobnail-like endothelial cells that protrude within the narrow lumina. Kaposiform hemangioendothelioma is composed of several solid poorly circumscribed nodules, and each nodule is composed of a mixture of small capillaries and solid lobules of endothelial cells arranged in a glomeruloid pattern. A frequent finding consists of the presence of areas of lymphangiomatosis adjacent to the solid nodules. Epithelioid hemangioendothelioma is composed of cords, strands, and solid aggregates of round, oval, and polygonal cells, with abundant pale eosinophilic cytoplasm, vesicular nuclei, and inconspicuous nucleoli, embedded in a fibromyxoid or sclerotic stroma. Many neoplastic cells exhibit prominent cytoplasmic vacuolization as an expression of primitive vascular differentiation. Pseudomyogenic hemangioendothelioma is a poorly circumscribed, fascicular lesion with infiltrative borders composed of round or oval neoplastic cells, with vesicular nuclei and inconspicuous nucleoli, and ample homogeneous eosinophilic cytoplasm, giving them a rhabdomyoblastic appearance. Finally, composite hemangioendothelioma is the term used to name locally aggressive vascular neoplasms of low-grade malignancy showing varying combinations of benign, low-grade malignant, and high-grade malignant vascular components. From the immunohistochemical point of view, proliferating cells of all hemangioendotheliomas express a lymphatic endothelial cell immunophenotype. Most hemangioendotheliomas are low-grade vascular neoplasms, with a tendency to recur locally and a low metastatic potential, mostly to regional lymph nodes. Epithelioid hemangioendothelioma, especially large lesions and those located in deep soft tissues, seems to have a more aggressive biological behavior.

The homeobox transcription factor Prox1 inhibits proliferation of hepatocellular carcinoma cells by inducing p53-dependent senescence-like phenotype

The homeobox transcription factor Prox1 is highly expressed in adult hepatocytes and is involved in the regulation of bile acid synthesis and gluconeogenesis in the liver by interacting with other transcriptional activators or repressors. Recent studies showed that Prox1 could inhibit proliferation of hepatocellular carcinoma (HCC) cells and reduced Prox1 expression was associated with poor prognosis of HCC patients. However, the underlying mechanism by which Prox1 attenuates HCC growth is still unclear. In this study, we demonstrated that Prox1 induced senescence-like phenotype of HCC cells to reduce cell proliferation. Our results indicated that the tumor suppressor p53 is a key mediator of Prox1-induced growth suppression because Prox1 only induced senescence-like phenotype in HCC cells harboring wild type p53. In addition, knockdown of p53 by shRNA reversed the effect of Prox1. However, chromatin immunoprecipitation assay did not demonstrate the direct binding of Prox1 to proximal promoter of human p53 gene suggesting Prox1 might not directly activate p53 transcription. We found that Prox1 suppressed Twist expression in HCC cells and subsequently relieved its inhibition on p53 gene transcription. The involvement of Twist in the regulation of p53 by Prox1 was supported by the following evidence: (1) Prox1 inhibited Twist expression and promoter activity; (2) knockdown of Twist in SK-HEP-1 cells upregulated p53 expression and (3) ectopic expression of Twist counteracted Prox1-induced p53 transcription and senescence-like phenotype. We also indentified an E-box located at p53 promoter which is required for Twist to inhibit p53 expression. Finally, our animal experiment confirmed that Prox1 suppressed HCC growth in vivo. Collectively, we conclude that Prox1 suppresses proliferation of HCC cells via inhibiting Twist to trigger p53-dependent senescence-like phenotype.

Prospero homeobox 1 promotes epithelial-mesenchymal transition in colon cancer cells by inhibiting E-cadherin via miR-9

PURPOSE

Prospero homeobox 1 (PROX1) has been shown to function as a tumor suppressor in various types of cancer. However, it promotes colon cancer progression. The aim of this study is to clarify the underlying mechanism by which PROX1 regulates tumorigenicity of colon cancer.

EXPERIMENTAL DESIGN

Association of PROX1 and clinicopathological features was studied by immunohistochemical staining. Pri-miR-9-2 and miR-9 were detected by quantitative real-time PCR. Assays of cell invasion, adhesion, and matrix metalloproteinase activity were used to study PROX1-mediated epithelial-mesenchymal transition (EMT).

RESULTS

PROX1 was overexpressed in 43% (59/136) of colon cancer tissues and its expression was correlated with E-cadherin downregulation (P = 0.00005), advanced tumor staging (P = 0.005), and lymph node metastasis (P = 0.000009). Enforced expression of PROX1 in DLD-1 cells caused downregulation of E-cadherin and integrins and attenuated cell adhesion. These cells showed increase of matrix metalloproteinase activity and invasive ability. Conversely, knockdown of PROX1 in SW620 cells restored E-cadherin protein expression and reduced invasiveness. Unexpectedly, repression of E-cadherin by PROX1 was not mediated by transcriptional inhibition. We found that PROX1 bound to miR-9-2 promoter and triggered its expression to suppress E-cadherin 3'UTR reporter activity and protein expression. Anti-miR-9 restored E-cadherin in SW620 cells, whereas precursor miR-9 inhibited E-cadherin in PROX1-knockdown cells. The miR-9 level was higher in tumor tissues with high PROX1/low E-cadherin than that of tumor tissues with low PROX1/high E-cadherin.

CONCLUSIONS

Our results provide mechanistic insights by which PROX1 promotes EMT and colon cancer progression. Targeting of PROX1-mediated oncogenic activity may be helpful for the treatment of colon cancer.

PROX1 overexpression inhibits protein kinase C beta II transcription through promoter DNA methylation

Prospero-related homeobox 1 (PROX1) is important for embryonic organ formation and differentiation, and changes in PROX1 activity were recently associated with cancer. To address the PROX1 roles in tumorigenesis, we established cells stably overexpressing PROX1 using the human cervical cancer cell line, HeLa. Overexpression of PROX1 reduced cell proliferation and the rate of tumor formation as compared with controls. Comparison of gene expression profiles between PROX1-overexpressing and mock-transfected cells revealed that the expression of protein kinase C βII (PRKCB2) is down-regulated in PROX1-overexpressing cells. A PRKCB inhibitor suppressed cell growth of control cells more than PROX1-expressing cells. Analysis of the 5'-promoter of PRKCB revealed that a region between -110 bp and the first exon contains two Sp1 binding sites and is important for transcriptional regulation of PRKCB. The inhibition of Sp1 transcription factor resulted in down-regulation of PRKCB2 protein levels. Treatment with a demethylating agent, 5-aza-2'-deoxycytidine, restored PRKCB2 mRNA expression in PROX1-expressing cells, suggesting that the 5'-promoter of PRKCB is methylated in these cells. Actually, it was found that a CpG island in this region, in particular a CpG site overlapping with the distal Sp1 site, was hypermethylated and direct Sp1 binding to this region was inhibited in PROX1-overexpressing cells. Thus, the suppressive effect of PROX1 on cell growth and tumor formation might be partially mediated by PRKCB2 via altered methylation of its promoter.

Prox1 transcription factor as a marker for vascular tumors-evaluation of 314 vascular endothelial and 1086 nonvascular tumors

Prox1, a transcription factor important in the regulation and maintenance of the lymphatic endothelial phenotype, is consistently expressed in lymphangiomas and Kaposi sarcoma and has also been reported in Kaposiform hemangioendothelioma. However, information on its distribution in vascular tumors, such as angiosarcoma, is limited. In this study, we examined selected normal tissues and 314 vascular endothelial and 1086 nonvascular tumors to get an insight into the biology of these tumors and on potential diagnostic use of Prox1 as an immunohistochemical marker. In adult tissues, Prox1 was essentially restricted to lymphatic endothelia, with expression in subsets of pancreatic and gastrointestinal epithelia. However, it was also detected in embryonic liver and heart. Prox1 was consistently expressed in lymphangiomas, venous hemangiomas, Kaposi sarcoma, in endothelia of spindle cell hemangioma, Kaposiform hemangioendothelioma, and retiform hemangioendothelioma, and in half of epithelioid hemangioendotheliomas. It was present in most cutaneous angiosarcomas from different sites but was less commonly expressed in deep soft tissue and visceral angiosarcomas. In contrast, Prox1 was generally absent in capillary and cavernous hemangiomas. In positive hemangiomas and angiosarcomas it was coexpressed with podoplanin, another marker of the lymphatic endothelial phenotype. There was an inverse correlation with CD34 expression. The expression in mesenchymal nonendothelial neoplasm was limited. Prox1 was detected in 5 of 27 synovial sarcomas, specifically in the epithelia of biphasic tumors. Four of 16 Ewing sarcomas and 5 of 15 paragangliomas were also positive. All melanomas and undifferentiated sarcomas were negative. Among epithelial neoplasms, Prox1 was detected in 18 of 38 colonic carcinomas and 10 of 15 cholangiocarcinomas and in a minority of pulmonary, prostatic, and endometrial adenocarcinomas. The common Prox1 expression in angiosarcoma and its rare presence in nonvascular mesenchymal tumors make this marker suitable for the diagnosis of angiosarcoma and Kaposi sarcoma. However, the presence of Prox1 in some malignant epithelial tumors necessitates caution in applying Prox1 as a marker for vascular tumors. Common Prox1 expression in angiosarcoma may reflect the lymphatic endothelial phenotype in these tumors. Its patterns of expression in hemangiomas and angiosarcoma may be diagnostically useful and offer a new parameter in the biological classification of vascular tumors.

Tumor lymphangiogenesis as a potential therapeutic target

Metastasis the spread of cancer cells to distant organs, is the main cause of death for cancer patients. Metastasis is often mediated by lymphatic vessels that invade the primary tumor, and an early sign of metastasis is the presence of cancer cells in the regional lymph node (the first lymph node colonized by metastasizing cancer cells from a primary tumor). Understanding the interplay between tumorigenesis and lymphangiogenesis (the formation of lymphatic vessels associated with tumor growth) will provide us with new insights into mechanisms that modulate metastatic spread. In the long term, these insights will help to define new molecular targets that could be used to block lymphatic vessel-mediated metastasis and increase patient survival. Here, we review the molecular mechanisms of embryonic lymphangiogenesis and those that are recapitulated in tumor lymphangiogenesis, with a view to identifying potential targets for therapies designed to suppress tumor lymphangiogenesis and hence metastasis.

Current views on the function of the lymphatic vasculature in health and disease

The lymphatic vascular system is essential for lipid absorption, fluid homeostasis, and immune surveillance. Until recently, lymphatic vessel dysfunction had been associated with symptomatic pathologic conditions such as lymphedema. Work in the last few years had led to a better understanding of the functional roles of this vascular system in health and disease. Furthermore, recent work has also unraveled additional functional roles of the lymphatic vasculature in fat metabolism, obesity, inflammation, and the regulation of salt storage in hypertension. In this review, we summarize the functional roles of the lymphatic vasculature in health and disease.

Kaposin-B enhances the PROX1 mRNA stability during lymphatic reprogramming of vascular endothelial cells by Kaposi's sarcoma herpes virus

Kaposi's sarcoma (KS) is the most common cancer among HIV-positive patients. Histogenetic origin of KS has long been elusive due to a mixed expression of both blood and lymphatic endothelial markers in KS tumor cells. However, we and others discovered that Kaposi's sarcoma herpes virus (KSHV) induces lymphatic reprogramming of blood vascular endothelial cells by upregulating PROX1, which functions as the master regulator for lymphatic endothelial differentiation. Here, we demonstrate that the KSHV latent gene kaposin-B enhances the PROX1 mRNA stability and plays an important role in KSHV-mediated PROX1 upregulation. We found that PROX1 mRNA contains a canonical AU-rich element (ARE) in its 3′-untranslated region that promotes PROX1 mRNA turnover and that kaposin-B stimulates cytoplasmic accumulation of the ARE-binding protein HuR through activation of the p38/MK2 pathway. Moreover, HuR binds to and stabilizes PROX1 mRNA through its ARE and is necessary for KSHV-mediated PROX1 mRNA stabilization. Together, our study demonstrates that kaposin-B plays a key role in PROX1 upregulation during lymphatic reprogramming of blood vascular endothelial cells by KSHV.

Kaposi's sarcoma (KS) is the most common cancer in HIV-positive patients and KS-associated herpes virus (KSHV) was identified as its causing agent. We and others have discovered that when the virus infects endothelial cells of blood vessels, KSHV reprograms the cell type resembling endothelial cells in lymphatic vessels. Although endothelial cells of the blood vascular system and of the lymphatic system share functional similarities, the cell type-reprogramming does not occur under a normal physiological condition. Therefore, cell-fate reprogramming by the cancer-causing virus KSHV provides an important insight into the molecular mechanism for viral pathogenesis. Our current study investigates the molecular mechanism underlying the KSHV-mediated cell fate reprogramming. We identified that a KSHV latent gene kaposin-B plays an important role in KSHV-mediated regulation of PROX1 to promote PROX1 mRNA stability. This study will provide a better understanding on the tumorigenesis and pathogenesis of KS with a potential implication toward new KS therapy.

Multistage genomewide association study identifies a locus at 1q41 associated with rate of HIV-1 disease progression to clinical AIDS

BACKGROUND

A mean of 9-10 years of human immunodeficiency virus type 1 (HIV-1) infection elapse before clinical AIDS develops in untreated persons, but this rate of disease progression varies substantially among individuals. To investigate host genetic determinants of the rate of progression to clinical AIDS, we performed a multistage genomewide association study.

METHODS

The discovery stage comprised 156 individuals from the Multicenter AIDS Cohort Study, enriched with rapid and long-term nonprogressors to increase statistical power. This was followed by replication tests of putatively associated genotypes in an independent population of 590 HIV-1-infected seroconverters.

RESULTS

Significant associations with delayed AIDS progression were observed in a haplotype located at 1q41, 36 kb upstream of PROX1 on chromosome 1 (relative hazard ratio, 0.69; Fisher's combined P = 6.23 X 10(-7)). This association was replicated further in an analysis stratified by transmission mode, with the effect consistent in sexual or mucosal and parenteral transmission (relative hazard ratios, 0.72 and 0.63, respectively; combined P = 1.63 X 10(-6)).

CONCLUSIONS

This study identified and replicated a locus upstream of PROX1 that is associated with delayed progression to clinical AIDS. PROX1 is a negative regulator of interferon-gamma expression in T cells and also mitigates the advancement of vascular neoplasms, such as Kaposi sarcoma, a common AIDS-defining malignancy. This study adds to the cumulative polygenic host component that effectively regulates the progression to clinical AIDS among HIV-1-infected individuals, raising prospects for potential new avenues for therapy and improvements in AIDS prognosis.

TScratch: a novel and simple software tool for automated analysis of monolayer wound healing assays

Cell migration plays a major role in development, physiology, and disease, and is frequently evaluated in vitro by the monolayer wound healing assay. The assay analysis, however, is a time-consuming task that is often performed manually. In order to accelerate this analysis, we have developed TScratch, a new, freely available image analysis technique and associated software tool that uses the fast discrete curvelet transform to automate the measurement of the area occupied by cells in the images. This tool helps to significantly reduce the time needed for analysis and enables objective and reproducible quantification of assays. The software also offers a graphical user interface which allows easy inspection of analysis results and, if desired, manual modification of analysis parameters. The automated analysis was validated by comparing its results with manual-analysis results for a range of different cell lines. The comparisons demonstrate a close agreement for the vast majority of images that were examined and indicate that the present computational tool can reproduce statistically significant results in experiments with well-known cell migration inhibitors and enhancers.

The lymphatic system in health and disease

The lymphatic vascular system has an important role in the regulation of tissue pressure, immune surveillance and the absorption of dietary fat in the intestine. There is growing evidence that the lymphatic system also contributes to a number of diseases, such as lymphedema, cancer metastasis and different inflammatory disorders. The discovery of various molecular markers allowing the distinction of blood and lymphatic vessels, together with the availability of a increasing number of in vitro and in vivo models to study various aspects of lymphatic biology, has enabled tremendous progress in research into the development and function of the lymphatic system. This review discusses recent advances in our understanding of the embryonic development of the lymphatic vasculature, the molecular mechanisms mediating lymphangiogenesis in the adult, the role of lymphangiogenesis in chronic inflammation and lymphatic cancer metastasis, and the emerging importance of the lymphatic vasculature as a therapeutic target.