Phosphatidylserine is a marker of tumor vasculature and a potential target for cancer imaging and therapy
ABSTRACT (1) To determine whether exposure of phosphatidylserine (PS) occurs on vascular endothelium in solid tumors in mice. (2) To determine whether PS exposure can be induced on viable endothelial cells in tissue culture by conditions present in the tumor microenvironment.
Externalized PS in vivo was detected by injecting mice with a monoclonal anti-PS antibody and examining frozen sections of tumors and normal tissues for anti-PS antibody bound to vascular endothelium. Apoptotic cells were identified by anti-active caspase-3 antibody or by TUNEL assay. PS exposure on cultured endothelial cells was determined by 125I-annexin V binding.
Anti-PS antibody bound specifically to vascular endothelium in six tumor models. The percentage of PS-positive vessels ranged from 4% to 40% in different tumor types. Vascular endothelium in normal organs was unstained. Very few tumor vessels expressed apoptotic markers. Hypoxia/reoxygenation, acidity, inflammatory cytokines, thrombin, or hydrogen peroxide induced PS exposure on cultured endothelial cells without causing loss of viability.
Vascular endothelial cells in tumors, but not in normal tissues, externalize PS. PS exposure might be induced by tumor-associated oxidative stress and activating cytokines. PS is an abundant and accessible marker of tumor vasculature and could be used for tumor imaging and therapy.
- SourceAvailable from: Shadi Abu-Baker
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- "We reported previously that SapC preferentially interacts with unsaturated, negatively charged phospholipids (such as dioleoylphosphatidylserine, DOPS), at acidic pH  . It has been reported that phosphatidylserine (PS) is relatively abundant on the surface of tumor tissues  ; it could provide a tumor-specific target for SapC. In the design of our new therapeutic agent (SapC-DOPS nanovesicles), we took advantage of two unique properties of tumor cells compared to normal cells. "
ABSTRACT: Squamous cell carcinoma (SCC) and melanoma are malignant human cancers of the skin with an annual mortality that exceeds 10,000 cases every year in the USA alone. In this study, the lysosomal protein saposin C (SapC) and the phos-pholipid dioloylphosphatidylserine (DOPS) were assembled into cancer-selective nanovesicles (SapC-DOPS) and suc-cessfully tested using several in vitro and in vivo skin cancer models. Using MTT assay that measures the percentage of cell death, SapC-DOPS cytotoxic effect on three skin tumor cell lines (squamous cell carcinoma, SK-MEL-28, and MeWo) was compared to two normal nontumorigenic skin cells lines, normal immortalized keratinocyte (NIK) and human fibroblast cell (HFC). We observed that the nanovesicles selectively killed the skin cancer cells by inducing apoptotic cell death whereas untransformed skin cancer cells remained unaffected. Using subcutaneous skin tumor xenografts, animals treated with SapC-DOPS by subcutaneous injection showed a 79.4% by volume tumor reduced compared to the control after 4 days of treatment. We observed that the nanovesicles killed skin cancer cells by induc-ing apoptotic cell death compared to the control as revealed by TUNEL staining of xenograft tumor sections.Journal of Cancer Therapy 08/2012; 3(4). DOI:10.4236/jct.2012.34041
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- "Thus, in addition to imaging apoptotic tumor cells, PS-binding probes also image the exposed PS on the tumor vasculature. We have developed a series of monoclonal antibodies that recognize PS with higher specificity than does annexin V    . The antibodies recognize PS complexed with the PS-binding protein, β 2 -glycoprotein 1 (β 2 GP1) . "
ABSTRACT: Phosphatidylserine (PS) is normally intracellular but becomes exposed on the luminal surface of vascular endothelial cells in tumors. It also becomes exposed on tumors cells responding to therapy. In the present study, we optically imaged exposed PS in vivo using PGN635, a novel monoclonal antibody that binds PS. The F(ab')(2) fragment of PGN635 was labeled with the near-infrared (NIR) dye, IRDye800CW. In vivo dynamic NIR imaging was performed after injection of 800CW-PGN635 into mice bearing radiation-treated or untreated U87 glioma xenografts growing subcutaneously or orthotopically. NIR optical imaging revealed a clear tumor contrast in nonirradiated subcutaneous U87 gliomas after injection of 800CW-PGN635. The tumor contrast was visible as early as 4 hours later and was maximal 24 hours later (tumor-to-normal tissue ratio [TNR] = 2.8 ± 0.7). Irradiation enhanced the tumor contrast at 24 hours (TNR = 4.0 ± 0.3). Similar results were observed for orthotopic gliomas. Localization of 800CW-PGN635 to tumors was antigen specific because 800CW-Aurexis, a control probe of irrelevant specificity, did not localize to the tumors, and preadministration of unlabeled PGN635 blocked the uptake of 800CW-PGN635. Fluorescence microscopy confirmed that 800CW-PGN635 was binding to PS-positive vascular endothelial cells in nonirradiated gliomas. Irradiation of the gliomas increased PS exposure on both tumor vascular endothelial cells and tumor cells and gave rise to an increase in tumor contrast with 800CW-PGN635 that was predictive of the reduction in tumor growth. 800CW-PGN635 may be a useful new imaging probe for detection of exposed PS in tumors responding to therapy.Translational oncology 12/2011; 4(6):355-64. DOI:10.1593/tlo.11178 · 3.40 Impact Factor
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- "This is particularly problematic in tissue sections because tissue preparation (cutting and treatment with detergents) generates a high rate of false positives. Furthermore, PS externalization may not always be associated with cell death; it has been shown in living endothelial cells of tumor vasculature (Ran and Thorpe, 2002). PS externalization has been shown to be reversible in granulocytes and monocytes (Yang et al, 2002) and in cardiomyocytes subjected to brief episodes of ischemia (Kenis et al, 2010). "
ABSTRACT: One of the hallmarks of stroke pathophysiology is the widespread death of many different types of brain cells. As our understanding of the complex disease that is stroke has grown, it is now generally accepted that various different mechanisms can result in cell damage and eventual death. A plethora of techniques is available to identify various pathological features of cell death in stroke; each has its own drawbacks and pitfalls, and most are unable to distinguish between different types of cell death, which partially explains the widespread misuse of many terms. The purpose of this review is to summarize the standard histopathological and immunohistochemical techniques used to identify various pathological features of stroke. We then discuss how these methods should be properly interpreted on the basis of what they are showing, as well as advantages and disadvantages that require consideration. As there is much interest in the visualization of stroke using noninvasive imaging strategies, we also specifically discuss how these techniques can be interpreted within the context of cell death.Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 11/2011; 32(2):213-31. DOI:10.1038/jcbfm.2011.150 · 5.34 Impact Factor