COX-2 inhibition potentiates antiangiogenic cancer therapy and prevents metastasis in preclinical models.

Antiangiogenic agents that block vascular endothelial growth factor (VEGF) signaling are important components of current cancer treatment modalities but are limited by alternative ill-defined angiogenesis mechanisms that allow persistent tumor vascularization in the face of continued VEGF pathway blockade. We identified prostaglandin E2 (PGE2) as a soluble tumor-derived angiogenic factor associated with VEGF-independent angiogenesis. PGE2 production in preclinical breast and colon cancer models was tightly controlled by cyclooxygenase-2 (COX-2) expression, and COX-2 inhibition augmented VEGF pathway blockade to suppress angiogenesis and tumor growth, prevent metastasis, and increase overall survival. These results demonstrate the importance of the COX-2/PGE2 pathway in mediating resistance to VEGF pathway blockade and could aid in the rapid development of more efficacious anticancer therapies.

GPR124, an orphan G protein-coupled receptor, is required for CNS-specific vascularization and establishment of the blood-brain barrier.

Every organ in the body requires blood vessels for efficient delivery of oxygen and nutrients, but independent vascular beds are highly specialized to meet the individual needs of specific organs. The vasculature of the brain is tightly sealed, with blood-brain barrier (BBB) properties developing coincident with neural vascularization. G protein-coupled receptor 124 (GPR124) (tumor endothelial marker 5, TEM5), an orphan member of the adhesion family of G protein-coupled receptors, was previously identified on the basis of its overexpression in tumor vasculature. Here, we show that global deletion or endothelial-specific deletion of GPR124 in mice results in embryonic lethality associated with abnormal angiogenesis of the forebrain and spinal cord. Expression of GPR124 was found to be required for invasion and migration of blood vessels into neuroepithelium, establishment of BBB properties, and expansion of the cerebral cortex. Thus, GPR124 is an important regulator of neurovasculature development and a potential drug target for cerebrovascular diseases.

The cell surface structure of tumor endothelial marker 8 (TEM8) is regulated by the actin cytoskeleton.

Tumor endothelial marker 8 (TEM8) is an integrin-like cell surface protein upregulated on tumor blood vessels and a potential vascular target for cancer therapy. Here, we found that the ability of an anti-TEM8 antibody, clone SB5, to recognize the extracellular domain of TEM8 on the cell surface depends on other host-cell factors. By taking advantage of SB5's ability to distinguish different forms of cell surface TEM8, we identified alpha-smooth muscle actin and transgelin, an actin binding protein, as intracellular factors able to alter TEM8 cell surface structure. Overexpression of either of these proteins in cells converted TEM8 from an SB5-exposed to an SB5-masked form and protected cells from SB5-saporin immunotoxins. Because the predominant form of TEM8 on the cell surface is not recognized by SB5, we also developed a new monoclonal antibody, called AF334, which is able to recognize both the SB5-exposed and the SB5-masked forms of TEM8. AF334-saporin selectively killed TEM8-positive cells independent of TEM8 cell surface structure. These studies reveal that TEM8 exists in different forms at the cell surface, a structure dependent on interactions with components of the actin cytoskeleton, and should aid in the rational design of the most effective diagnostic and therapeutic anti-TEM8 monoclonal antibodies.

Genes that distinguish physiological and pathological angiogenesis.

To unravel the normal vasculature transcriptome and determine how it is altered by neighboring malignant cells, we compared gene expression patterns of endothelial cells derived from the blood vessels of eight normal resting tissues, five tumors, and regenerating liver. Organ-specific endothelial genes were readily identified, including 27 from brain. We also identified 25 transcripts overexpressed in tumor versus normal endothelium, including 13 that were not found in the angiogenic endothelium of regenerating liver. Most of the shared angiogenesis genes have expected roles in cell-cycle control, but those specific for tumor endothelium were primarily cell surface molecules of uncertain function. These studies reveal striking differences between physiological and pathological angiogenesis potentially important for the development of tumor-specific, vascular-targeted therapies.

Optoinjection for efficient targeted delivery of a broad range of compounds and macromolecules into diverse cell types.

Efficient delivery of compounds and macromolecules into living cells is essential in many fields including basic research, applied drug discovery, and clinical gene therapy. Unfortunately, current delivery methods, such as cationic lipids and electroporation, are limited by the types of macromolecules and cells that can be employed, poor efficiency, and/or cell toxicity. To address these issues, novel methods were developed based on laser-mediated delivery of macromolecules into cells through optoinjection. An automated high-throughput instrument, the laser-enabled analysis and processing (LEAP) system, was utilized to elucidate and optimize several parameters that influence optoinjection efficiency and toxicity. Techniques employing direct cell irradiation (i.e., targeted to specific cell coordinates) and grid-based irradiation (i.e., without locating individual cells) were both successfully developed. With both techniques, it was determined that multiple, sequential low radiant exposures produced more favorable results than a single high radiant exposure. Various substances were efficiently optoinjected--including ions, small molecules, dextrans, siRNAs (small interfering RNAs), plasmids, proteins, and semiconductor nanocrystals--into numerous cell types. Notably, cells refractory to traditional delivery methods were efficiently optoinjected with lower toxicity. We establish the broad utility of optoinjection, and furthermore, are the first to demonstrate its implementation in an automated, high-throughput manner.

Automated in situ measurement of cell-specific antibody secretion and laser-mediated purification for rapid cloning of highly-secreting producers.

Cloning of highly-secreting recombinant cells is critical for biopharmaceutical manufacturing, but faces numerous challenges including the fact that secreted protein does not remain associated with the producing cell. A fundamentally new approach was developed combining in situ capture and measurement of individual cell protein secretion followed by laser-mediated elimination of all non- and poorly-secreting cells, leaving only the highest-secreting cell in a well. Recombinant cells producing humanized antibody were cultured serum-free on a capture matrix, followed by staining with fluorescently-labeled anti-human antibody fragment. A novel, automated, high-throughput instrument (called LEAP) was used to image and locate every cell, quantify the cell-associated and secreted antibody (surrounding each cell), eliminate all undesired cells from a well via targeted laser irradiation, and then track clone outgrowth and stability. Temporarily sparing an island of helper cells around the clone of interest improved cloning efficiency (particularly when using serum-free medium), and helper cells were easily eliminated with the laser after several days. The in situ nature of this process allowed several serial sub-cloning steps to be performed within days of one another, resulting in rapid generation of clonal populations with significantly increased and more stable, homogeneous antibody secretion. Cell lines with specific antibody secretion rates of > 50 pg/cell per day (in static batch culture) were routinely obtained as a result of this cloning approach, often times representing up to 20% of the clones screened.

High-throughput laser-mediated in situ cell purification with high purity and yield.

BACKGROUND: Technologies for purification of living cells have significantly advanced basic and applied research in many settings. Nevertheless, certain challenges remain, including the robust and efficient purification (e.g., high purity, yield, and sterility) of adherent and/or fragile cells and small cell samples, efficient cell cloning, and safe purification of biohazardous cells. In addition, existing purification methods are generally open loop and exhibit an inverse relation between cell purity and yield. METHODS: An automated closed-loop (i.e., employing feedback control) cell purification technology was developed by building upon medical laser applications and laser-based semiconductor manufacturing equipment. Laser-enabled analysis and processing has combined high-throughput in situ cell imaging with laser-mediated cell manipulation via large field-of-view optics and galvanometer steering. Laser parameters were determined for cell purification using three mechanisms (photothermal, photochemical, and photomechanical), followed by demonstration of system performance and utility. RESULTS: Photothermal purification required approximately 10(8) W/cm(2) at 523 nm in the presence of Allura Red, resulting in immediate protein coagulation and cell necrosis. Photochemical purification required approximately 10(9) W/cm(2) at 355 nm, resulting in apoptosis induction over 4 to 24 h. Photomechanical purification required more than 10(10) W/cm(2) independent of wavelength, resulting in immediate cell lysis. Each approach resulted in high efficiency purification (>99%) after a single operation, as demonstrated with eight cell types. An automated closed-loop process to re-image and irradiate remaining targets in situ was implemented, resulting in improved purification (99.5-100%) without decreasing cell yield or affecting sterility in this closed system. Efficient purification was demonstrated with B- and T-cell mixtures over a wide range of contaminating cell percentages (0.1-99%) and cell densities (10(4)-10(6)/cm(2)). Efficient cloning of 293T cells based on fluorescence with green fluorescent protein after plasmid transfection was also demonstrated. CONCLUSIONS: In situ laser-mediated purification was achieved with nonadherent and adherent cells on the automated laser-enabled analysis and processing platform. Closed-loop processing routinely enabled greater than 99.5% purity with a greater than 90% cell yield in sample sizes ranging from 10(1) to 10(8) cells. Throughput ranged from approximately 10(3) to 10(5) total cells/s for contaminating percentages ranging from 99% to 0.1%, respectively.