Comprehensive investigation of T and B cell receptor repertoires in an MC38 tumor model following murine anti­PD­1 administration.

The MC38 (derived from carcinogen­induced colon adenocarcinoma) tumor model is sensitive to anti­programmed cell death­1 (anti-PD­1) treatment. However, there is no comprehensive description of the T and B cell receptor (TCR, BCR) repertoires of the MC38 tumor model following anti­PD­1 treatment, an improved understanding of which is highly important in the development of anti­PD­1 immunotherapy. The present study analyzed the TCR and BCR repertoires of three types of tissue, including tumor, spleen and tumor draining lymph node (DLN) from 20 MC38 syngeneic mice receiving murine anti­PD­1 (mDX400) treatment or mouse immunoglobulin G1 (mIgG1) control treatment. To obtain enough tissues for high­throughput sequencing, samples were collected on day 8 after the start of initial treatment. The usage frequencies of seven TCR ß chain (TRB) V genes and one TRBJ gene were significantly different between mDX400­ and mIgG1­group tumors. TCR repertoire diversity was significantly lower in mDX400­group tumors compared with mIgG1­group tumors, with the top 10 most frequent TCR clonotypes notably expanded in mDX400­group tumors. In addition, the proportion of high­frequency TCR clonotypes from mDX400­group tumors that were also present both in the DLN and spleen was significantly higher than that in mIgG1­group tumors. Among the highly expanded TCR clonotypes, one TCR clonotype was consistently expanded in >50% of the mDX400­group tumors compared with mIgG1­group tumors. Similarly, one BCR clonal family was highly expanded in >50% of mDX400­group tumor samples. The consistently expanded TCR and BCR clones were co­expanded in 29% of mDX400­group tumors. Moreover, mutation rates of immunoglobulin heavy chain sequences in the spleen within complementarity determining region 2 and framework region 3 were significantly higher in the mDX400 group than in the mIgG1 group. The findings of this study may contribute to an improved understanding of the molecular mechanisms of anti­PD­1 treatment.

Differentiation and dynamic analysis of primitive vessels from embryonic stem cells.

Embryonic stem (ES) cells, which are derived from developing mouse blastocysts, have the ability to differentiate into various cell types in vitro. When placed in basal medium with added serum, mouse ES cells undergo a programmed differentiation favoring formation of cell types that are found in the embryonic yolk sac, including vascular endothelial cells. These in vitro differentiated endothelial cells form primitive blood vessels, analogous to the first vessels that form in the embryo and the yolk sac. This differentiation model is ideal for both genetic and pharmacological manipulation of early vascular development. We have made mouse ES cell lines that express endothelial-specific GFP or H2B-GFP and used these lines to study the processes of mammalian vessel development by real-time imaging. Here we describe protocols for making transgenic ES cells and imaging the processes of blood vessel development. We also provide methods for ES cell maintenance and differentiation, and methods for analysis of vascular marker expression.

The VEGF receptor Flt-1 spatially modulates Flk-1 signaling and blood vessel branching.

Blood vessel formation requires the integrated regulation of endothelial cell proliferation and branching morphogenesis, but how this coordinated regulation is achieved is not well understood. Flt-1 (vascular endothelial growth factor [VEGF] receptor 1) is a high affinity VEGF-A receptor whose loss leads to vessel overgrowth and dysmorphogenesis. We examined the ability of Flt-1 isoform transgenes to rescue the vascular development of embryonic stem cell-derived flt-1-/- mutant vessels. Endothelial proliferation was equivalently rescued by both soluble (sFlt-1) and membrane-tethered (mFlt-1) isoforms, but only sFlt-1 rescued vessel branching. Flk-1 Tyr-1173 phosphorylation was increased in flt-1-/- mutant vessels and partially rescued by the Flt-1 isoform transgenes. sFlt-1-rescued vessels exhibited more heterogeneous levels of pFlk than did mFlt-1-rescued vessels, and reporter gene expression from the flt-1 locus was also heterogeneous in developing vessels. Our data support a model whereby sFlt-1 protein is more efficient than mFlt-1 at amplifying initial expression differences, and these amplified differences set up local discontinuities in VEGF-A ligand availability that are important for proper vessel branching.

Neutralizing VEGF decreases tortuosity and alters endothelial cell division orientation in arterioles and veins in a rat model of ROP: relevance to plus disease.

PURPOSE: To study the effects of vascular endothelial growth factor (VEGF) on endothelial nitric oxide synthetase (eNOS) and retinal vascular tortuosity and cleavage planes in a rat model of retinopathy of prematurity (ROP). METHODS: Within 4 hours of birth, pups and mothers were cycled between 50% and 10% oxygen daily. At postnatal day (p)12, pups received either intravitreous anti-rat neutralizing antibody to VEGF or control nonimmune rat IgG in one eye and returned to oxygen cycling until p14 when they were placed in room air (RA) for 4 days (50/10 oxygen-induced retinopathy [50/10 OIR]). Tortuosity indices and endothelial cleavage plane angles relative to the long axes of the major retinal vessels during anaphase were calculated from phosphohistone- and Alexa-isolectin-stained retinal flatmounts. Some retinas were processed for eNOS protein or phosphorylated/total eNOS. RESULTS: Retinas from 50/10 OIR had increased tortuosity over time with peaks at p12 and p14 (P < 0.001 vs. RA) before the development of intravitreous neovascularization, which peaked at p18. Compared with RA, eNOS/actin in 50/10 OIR retinas was increased at p12 (P = 0.0003) and p14 (P = 0.047). Inhibition of VEGF with a neutralizing antibody decreased tortuosity and caused endothelial mitosis cleavage planes to orient in favor of vessel elongation but did not affect eNOS protein or activation. CONCLUSIONS: In the 50/10 OIR model, a model with relevance to ROP, arteriolar tortuosity, and venous dilation are increased through VEGF, which influences the orientation of endothelial cell cleavage in major arterioles and veins, independent of eNOS.

Orientation of endothelial cell division is regulated by VEGF signaling during blood vessel formation.

New blood vessel formation requires the coordination of endothelial cell division and the morphogenetic movements of vessel expansion, but it is not known how this integration occurs. Here, we show that endothelial cells regulate division orientation during the earliest stages of blood vessel formation, in response to morphogenetic cues. In embryonic stem (ES) cell-derived vessels that do not experience flow, the plane of endothelial cytokinesis was oriented perpendicular to the vessel long axis. We also demonstrated regulated cleavage orientation in vivo, in flow-exposed forming retinal vessels. Daughter nuclei moved away from the cleavage plane after division, suggesting that regulation of endothelial division orientation effectively extends vessel length in these developing vascular beds. A gain-of-function mutation in VEGF signaling increased randomization of endothelial division orientation, and this effect was rescued by a transgene, indicating that regulation of division orientation is a novel mechanism whereby VEGF signaling affects vessel morphogenesis. Thus, our findings show that endothelial cell division and morphogenesis are integrated in developing vessels by flow-independent mechanisms that involve VEGF signaling, and this cross talk is likely to be critical to proper vessel morphogenesis.

The TRK1 potassium transporter is the critical effector for killing of Candida albicans by the cationic protein, Histatin 5.

The principal feature of killing of Candida albicans and other pathogenic fungi by the catonic protein Histatin 5 (Hst 5) is loss of cytoplasmic small molecules and ions, including ATP and K(+), which can be blocked by the anion channel inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. We constructed C. albicans strains expressing one, two, or three copies of the TRK1 gene in order to investigate possible roles of Trk1p (the organism's principal K(+) transporter) in the actions of Hst 5. All measured parameters (Hst 5 killing, Hst 5-stimulated ATP efflux, normal Trk1p-mediated K(+) ((86)Rb(+)) influx, and Trk1p-mediated chloride conductance) were similarly reduced (5-7-fold) by removal of a single copy of the TRK1 gene from this diploid organism and were fully restored by complementation of the missing allele. A TRK1 overexpression strain of C. albicans, constructed by integrating an additional TRK1 gene into wild-type cells, demonstrated cytoplasmic sequestration of Trk1 protein, along with somewhat diminished toxicity of Hst 5. These results could be produced either by depletion of intracellular free Hst 5 due to sequestered binding, or to cooperativity in Hst 5-protein interactions at the plasma membrane. Furthermore, Trk1p-mediated chloride conductance was blocked by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid in all of the tested strains, strongly suggesting that the TRK1 protein provides the essential pathway for ATP loss and is the critical effector for Hst 5 toxicity in C. albicans.

Epitope tagging of the yeast K(+) carrier Trk2p demonstrates folding that is consistent with a channel-like structure.

TRK family proteins, which mediate the concentrative uptake of potassium by plant cells, fungi, and bacteria, resemble primitive potassium channels in sequence and have recently been proposed actually to fold like potassium channels in a 4-MPM motif (Durell, S. R., and Guy, H. R. (1999) Biophys. J. 77, 789 - 807), instead of like conventional substrate porters in the 12-TM motif (Gaber, R. F., Styles, C. A., and Fink, G. R. (1988) Mol. Cell. Biol. 8, 2848-2859). The known fungal members of this family possess a very long hydrophilic loop, positioned intracellularly in the K(+)-channel model and extracellularly in the substrate porter model. This and two shorter hydrophilic segments have been tested as topological markers for the true folding pattern of TRK proteins using Saccharomyces cerevisiae Trk2p. Hemagglutinin epitope tags were inserted into all three segments, and the enhanced green fluorescent protein (EGFP) was fused to the C terminus of Trk2p. The gene constructs were expressed from a high copy plasmid, and sidedness of the tags was determined by native fluorescence (EGFP), indirect immunofluorescence, and immunoelectron microscopy. Both the long-loop tag and the C-terminal EGFP fusion allowed abundant protein to reach the plasma membrane and support normal yeast growth. In all determinations, the long-loop tag was localized to the inner surface of the yeast cell plasma membrane, thus strongly supporting the channel-like folding model. Additional observations showed (i). membrane-associated Trk2p to lie in proteolipid rafts; (ii). significant tagged protein, expressed from the plasmid, to be sequestered in cytoplasmic vesicular-tubular clusters; and (iii). suppression of such clusters by yeast growth in 5-10% glycerol. This chaperone-like effect may assist other membrane proteins (overexpressed or heterologously expressed) to function within the yeast plasma membrane.

Extracellular domain of kinase domain region mediated by adeno-associated virus inhibits growth and angiogenesis of bladder cancer in Balb-c mice.

OBJECTIVE: To verify whether the extracellular domain of kinase domain region (KDR) has anti-angiogenesis activity in vivo. METHODS: cDNA was cloned into adeno-associated virus (AAV) vector pSNAV and transfected to baby hamster kidney (BHK) cells. Recombinant AAV was obtained from the cell culture supernatant after adding helper virus. Recombinant AAV-infected human bladder cancer EJ cell line (EJ cells) were injected subcutaneously into Balb-c nude mice. Tumor specimens were removed from the mice, paraffin-embedded and sliced, then stained by immunohistochemistry. Microvessel density (MVD) was determined under a microscope. RESULTS: The tumor volume developed by EJ cells transfected with the extracellular domain of KDR was significantly smaller (1.70 +/- 0.18 cm(3)) compared with that in the control (5.62 +/- 0.67 cm(3)) (P < 0.05), although tumor developed to be detectable on almost the same time (14.7 +/- 2.4 days vs 14.1 +/- 3.2 days). Further, MVD in the experimental group was lower than that in the control (41.3 +/- 4.8 vs 6.2 +/- 2.1, P < 0.05). CONCLUSION: The extracellular domain of KDR could be expressed in nude mouse bladder cancer tissue and inhibit tumor angiogenesis.

Expression, Purification and Biological Activity Analysis of Human Vascular Endothelial Growth Factor (VEGF(165)) in Pichia pastoris.

The human VEGF(165) cDNA was amplified by PCR, and was inserted, after confirming by DNA sequence analysis, into the Pichia pastoris expression vector pPIC9K containing AOX1 promoter and lead sequence of alpha factor gene to form a recombinant expression plasmids pPIC9K/hVEGF(165). This recombinant plasmid was transformed into KM71. Transformants were screened, cultured inflasks and induced by the addition of 1% methanol. After 4 days of methanol induction, the expressed hVEGF(165) came up to 60% of total proteins in medium supernatant as shown by SDS-PAGE. Western blot assay proved that the expressed hVEGF(165) had good antigenicity and high specificity. The recombinant protein was further purified by using Heparin-Sepharose CL6B affinity chromatography, and was proved that it had good biological activity to stimulate HUVEC proliferation and to promote collateral blood vessel formation in an acquired limb artery occlusion animal model.

Ligand Binding Domains of human Vascular Endothelial Growth Factor Receptor.

Four cDNA clones, encoding truncated Flt-1 mutants consisting of loop 2, 1-2, 2-3 and 1-3, were amplified by PCR from human placenta cDNA library and the corresponding gene fragments were named Flt-1(2) Flt-1(1-2) Flt-1(2-3) and Flt-1(1-3). In order to detect which part of the extracellular domain was involved in ligand binding, the interaction between Flt-1 mutants and hVEGF(165) was studied with yeast two-hybrid system. The data presented here suggest that both Flt-1(2-3) and Flt-1(1-3) were able to bind hVEGF(165). Two recombinant expression plasmids, pPIC9K/Flt-1(1-3) and pPIC9K/Flt-1(2-3), were constructed and transformed into Pichia pastoris strain GS115, respectively. After 4 days of methanol induction, the amount of the expressed Flt-1s reached 60% of total proteins in supernatant by SDS-PAGE. Recombinant proteins were purified with CM-Sepharose Fast Flow and Sephacryl S-100 chromatography. Biological activities analysis proved that 1-3 loop had slightly better biological activity than 2-3 loop in VEGF(165) binding and in inhibition of HUVEC proliferation stimulated by hVEGF(165).