The spontaneous release of a high-molecular-weight aggregate containing immunoglobulin G from the surface of Ehrlich ascites tumor cells

The spontaneous release of tumor cell antigens from the cell surface into the circulation has been proposed as a mechanism whereby tumors may escape the immune response of the host. In this study we have found that Ehrlich ascites tumor cells after removal from the host (mouse) spontaneously release significant amounts of cell surface components during incubation for 1 h in cold isotonic buffer. Immunodiffusion studies revealed that immunoglobulin G (IgG) and a complement component (C3) are included in this spontaneously released material. These surface-bound humoral immune components are apparently released in the form of a high-molecular-weight aggregate (cell coat particle) as shown by ultracentrifugation and ultrafiltration experiments. Precipitation of IgG from the cell coat particle preparation with antibodies directed against mouse IgG followed by detergent gel electrophoresis of the immune precipitate revealed five major bands in addition to the heavy and light chains of IgG. These results suggest that host IgG is tightly bound to several other components at the cell surface, perhaps in the form of immune complexes. IgG is localized on the tumor cell surface in a highly heterogeneous pattern with the appearance of patches and caps in some cells as shown by immuno-fluorescence analysis. The possibility that humoral immune components bind to the tumor cell surface and result in the shedding of high-molecular-weight aggregates of cell surface antigens into extracellular fluids is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38207/1/400090311_ftp.pd

An Efficient Targeted Drug Delivery through Apotransferrin Loaded Nanoparticles

BACKGROUND: Cancerous state is a highly stimulated environment of metabolically active cells. The cells under these conditions over express selective receptors for assimilation of factors essential for growth and transformation. Such receptors would serve as potential targets for the specific ligand mediated transport of pharmaceutically active molecules. The present study demonstrates the specificity and efficacy of protein nanoparticle of apotransferrin for targeted delivery of doxorubicin. METHODOLOGY/PRINCIPAL FINDINGS: Apotransferrin nanoparticles were developed by sol-oil chemistry. A comparative analysis of efficiency of drug delivery in conjugated and non-conjugated forms of doxorubicin to apotransferrin nanoparticle is presented. The spherical shaped apotransferrin nanoparticles (nano) have diameters of 25-50 etam, which increase to 60-80 etam upon direct loading of drug (direct-nano), and showed further increase in dimension (75-95 etam) in conjugated nanoparticles (conj-nano). The competitive experiments with the transferrin receptor specific antibody showed the entry of both conj-nano and direct-nano into the cells through transferrin receptor mediated endocytosis. Results of various studies conducted clearly establish the superiority of the direct-nano over conj-nano viz. (a) localization studies showed complete release of drug very early, even as early as 30 min after treatment, with the drug localizing in the target organelle (nucleus) (b) pharmacokinetic studies showed enhanced drug concentrations, in circulation with sustainable half-life (c) the studies also demonstrated efficient drug delivery, and an enhanced inhibition of proliferation in cancer cells. Tissue distribution analysis showed intravenous administration of direct nano lead to higher drug localization in liver, and blood as compared to relatively lesser localization in heart, kidney and spleen. Experiments using rat cancer model confirmed the efficacy of the formulation in regression of hepatocellular carcinoma with negligible toxicity to kidney and liver. CONCLUSIONS: The present study thus demonstrates that the direct-nano is highly efficacious in delivery of drug in a target specific manner with lower toxicity to heart, liver and kidney

The Tumor Microenvironment: The Making of a Paradigm

What has been will be again, what has been done will be done again; there is nothing new under the su

Combined use of AFM and X-ray diffraction to analyze crystals of an engineered, domain-deleted antibody.

A genetically engineered humanized C(H)2-domain-deleted monoclonal antibody lacking any interchain-hinge disulfide bonds has been crystallized in the presence of detergent in a form suitable for X-ray diffraction analysis. The crystals were grown from 4 M formate along with Triton X-100 and had P2(1)2(1)2 space-group symmetry, with unit-cell parameters a = 83, b = 224, c = 167 A. The crystals diffract to beyond 2.8 A resolution. A disordered crystal form of larger size and more attractive habit was also grown from 4 M formate, but in the presence of the Anapoe series of detergents. Preliminary X-ray data, in conjunction with atomic force microscopy images, are consistent with asymmetric units consisting of two intact antibodies forming a circular dimeric ring. The crystallizing unit, which must contain a twofold axis, is a toroidal assembly of four antibodies (two dimeric rings). Competition between dimers and tetramers to enter the lattice, along with a unique kind of planar defect of packing, may be responsible for the unusually high defect density and the disorder of the X-ray diffraction pattern exhibited by the second crystal form. An approach to crystallizing proteins showing phase separation, particularly intact antibodies, that uses a preliminary detergent test set is described