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Eyles J.,A+ Network | Puaux A.-L.,A+ Network | Wang X.,A+ Network | Toh B.,A+ Network | And 12 more authors.
Journal of Clinical Investigation | Year: 2010

Although metastasis is the leading cause of cancer-related death, it is not clear why some patients with localized cancer develop metastatic disease after complete resection of their primary tumor. Such relapses have been attributed to tumor cells that disseminate early and remain dormant for prolonged periods of time; however, little is known about the control of these disseminated tumor cells. Here, we have used a spontaneous mouse model of melanoma to investigate tumor cell dissemination and immune control of metastatic outgrowth. Tumor cells were found to disseminate throughout the body early in development of the primary tumor, even before it became clinically detectable. The disseminated tumor cells remained dormant for varying periods of time depending on the tissue, resulting in staggered metastatic outgrowth. Dormancy in the lung was associated with reduced proliferation of the disseminated tumor cells relative to the primary tumor. This was mediated, at least in part, by cytostatic CD8+ T cells, since depletion of these cells resulted in faster outgrowth of visceral metastases. Our findings predict that immune responses favoring dormancy of disseminated tumor cells, which we propose to be the seed of subsequent macroscopic metastases, are essential for prolonging the survival of early stage cancer patients and suggest that therapeutic strategies designed to reinforce such immune responses may produce marked benefits in these patients.

Mehta A.,Research and Development Unit | Chung Y.Y.,Research and Development Unit | Ng A.,Research and Development Unit | Iskandar F.,SingHealth Experimental Medicine Center | And 6 more authors.
Cardiovascular Research | Year: 2011

Aims Generation of human induced pluripotent stem cell (hiPSC) lines by reprogramming of fibroblast cells with virus-free methods offers unique opportunities for translational cardiovascular medicine. The aim of the study was to reprogramme fibroblast cells to hiPSCs and to study cardiomyogenic properties and ion channel characteristics of the virus-free hiPSC-derived cardiomyocytes. Methods and resultsThe hiPSCs generated by episomal vectors generated teratomas in severe combined immunodeficient mice, readily formed embryoid bodies, and differentiated into cardiomyocytes with comparable efficiency to human embryonic stem cells. Temporal gene expression of these hiPSCs indicated that differentiation of cardiomyocytes was initiated by increasing expression of cardio/mesodermal markers followed by cardiac-specific transcription factors, structural, and ion channel genes. Furthermore, the cardiomyocytes showed characteristic cross-striations of sarcomeric proteins and expressed calcium-handling and ion channel proteins, confirming their cardiac ontogeny. Microelectrode array recordings established the electrotonic development of a functional syncytium that responded predictably to pharmacologically active drugs. The cardiomyocytes showed a chronotropic doseresponse (0.110 M) to isoprenaline and Bay K 8644. Furthermore, carbamycholine (5 M) suppressed the response to isoprenaline, while verapamil (2.5 M) blocked Bay K 8644-induced inotropic activity. Moreover, verapamil (1 M) reduced the corrected field potential duration by 45, tetrodotoxin (10 M) shortened the minimal field potential by 40, and E-4031 (50 nM) prolonged field repolarization. ConclusionVirus-free hiPSCs differentiate efficiently into cardiomyocytes with cardiac-specific molecular, structural, and functional properties that recapitulate the developmental ontogeny of cardiogenesis. These results, coupled with the potential to generate patient-specific hiPSC lines, hold great promise for the development of an in vitro platform for drug pharmacogenomics, disease modelling, and regenerative medicine. © 2011 The Author.

Foulds W.S.,Singapore Eye Research Institute | Foulds W.S.,National University Hospital Singapore | Foulds W.S.,University of Glasgow | Kek W.K.,Singapore Eye Research Institute | And 6 more authors.
Investigative Ophthalmology and Visual Science | Year: 2010

To investigate the feasibility of creating an animal model of selective retinal capillary closure to mimic the capillary closure that occurs in diabetic retinopathy. METHODS. Fluorescent microspheres of 10- or 15-μm diameter were delivered to one eye of anesthetized pigs via a customized cannula advanced through the carotid arterial system to the origin of the external ophthalmic artery that supplies blood to the eye in this species. After preliminary trials in 10 pigs, embolization was performed in one eye of 34 animals that were allowed to survive for 7, 14, or 28 days. Embolized eyes were assessed by fluorescein angiography, electroretinography (ERG), and, after enucleation, light (LM) and electron (EM) microscopy.RESULTS. The microspheres were detectable in the retina immediately after embolization, were restricted to the nerve fiber layer of the retina, and remained thereafter within the retina for periods up to 28 days. They effectively occluded embolized capillaries and some precapillary arterioles. No systemic or cerebral adverse effects were noted, thus allowing survival and subsequent follow-up. Embolization caused a reduction in the b-wave amplitude and the oscillatory potentials of the rod- cone bright-flash ERG but did not affect the amplitude of the a-wave. Embolization induced extracellular and intracellular edema confined to the inner and mid retina, and as a result the retinas of embolized eyes were thicker than those of fellow, nonembolized eyes. The outer retina and RPE were unaffected. CONCLUSIONS. This survival model of retinal embolization with microspheres should be useful in the study of the retinal effects of the capillary closure that may occur in diabetic eyes. © Association for Research in Vision and Ophthalmology.

Jia J.,National University of Singapore | Wang J.,National University of Singapore | Teh M.,National University of Singapore | Sun W.,National University of Singapore | And 6 more authors.
Proteomics | Year: 2010

Hepatocellular carcinoma (HCC) is one of the deadliest cancers with few treatment options. It is a hypervascular tumor in which angiogenesis plays a critical role in its progression. Tumor capillary endothelial cells (TECs) in HCC are known to originate from liver sinusoid endothelial cells, which then go through a capillarization process to become morphologically as well as functionally different TECs. In this work, we investigated proteins differentially expressed between freshly isolated TECs and sinusoid endothelial cells from well-formed rat HCC using 2-D DIGE coupled with MALDI-TOF/TOF MS. Thirty-eight unique proteins were identified to be differentially expressed more than twofold between the two endothelial cell types. Amongst the differentially expressed proteins, two novel endothelial markers, EH domain-containing protein 3 and galectin-3, were confirmed by Western blot and immunohistochemistry in both rat and human HCC samples. We showed that EH domain-containing protein 3 is significantly down-regulated in TECs, but galectin-3 is up-regulated. We propose possible roles of these two proteins in tumor vessel development in HCC. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

Lei C.,National University of Singapore | Cui Y.,National University of Singapore | Zheng L.,SingHealth Experimental Medicine Center | Kah-Hoe Chow P.,National University of Singapore | And 2 more authors.
Biomaterials | Year: 2013

Malignant brain tumors are characterized by three major physiological processes: proliferation, angiogenesis, and invasion. Traditional cytotoxic chemotherapies (e.g. Paclitaxel) control the tumor by blocking growth and proliferation mechanisms, but leave angiogenesis and invasion unchecked. We identified Matrix metalloproteinase-2 (MMP-2), an essential proteinase regulating brain tumor invasion and angiogenesis, as one of the therapeutic target. A designer RNAi plasmid was developed, and complexed with the gene carrier polyethylenimine (PEI), in an effort to specifically suppress MMP-2 expression in tumor cells. The gene and a cytotoxic drug Paclitaxel were then dual-encapsulated in PLGA based submicron implants to achieve a sustained release of both agents. Potent inhibition effects on MMP-2 mRNA and protein expression, invitro cell angiogenesis and invasion were demonstrated both on the PEI/DNA nanoparticles alone, and on the PEI/DNA nanoparticles embedded in microfibers. Most importantly, through invivo test on intracranial xenograft tumor model in BALB/c nude mice, it was proved that the gene/drug dual delivery microfibers are able to impose significant tumor regression compared with single drug delivery microfibers and commercial drug treatment, showing evidence for synergistic therapeutic efficacy. © 2013 Elsevier Ltd.

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