zap-conjugates

Bak SP, Walters JJ, Takeya M, Conejo-Garcia JR, Berwin BL (2007) Scavenger receptor-A-targeted leukocyte depletion inhibits peritoneal ovarian tumor progression. Cancer Res 67:4783-4789. doi: 10.1158/0008-5472.CAN-06-4410

Summary: Vascular leukocytes (VLC) are immunosuppressive cells that facilitate tumor progression in ovarian cancer. One potential tumor therapy is to eliminate these cells. The authors determined that scavenger receptor-A is specifically expressed on VLCs. Mice were injected with tumor cells, as well as an anti-scavenger receptor-A antibody combined with Rat-ZAP (Cat. #IT-26). This was followed by additional treatment with the antibody-Rat-ZAP complex. Treatment with the immunotoxin eliminated VLCs, inhibited peritoneal tumor burden, and reduced ascites accumulation.

Related Products: Rat-ZAP (Cat. #IT-26)

Elson-Schwab L, Garner OB, Schuksz M, Esko JD, Tor Y (2007) Guanidinylated-Neomycin delivers large, bioactive cargo into cells through a heparan sulfate dependent pathway. J Biol Chem 282(18):13585-13591. doi: 10.1074/jbc.M700463200

Summary: The uptake of high molecular weight drugs into cells is a stumbling block for some potential therapeutics. Using a neomycin derivative in which guanidinium groups have replaced the ammonium groups, the authors show heparan sulfate-dependent uptake of large molecules. The guanidine-neomycin was biotinylated, and incubated with streptavidin-ZAP (Cat #IT-27). This complex was effective in killing CHO cells in vitro, but was no more effective than streptavidin-ZAP alone on cells lacking heparan sulfate expression, demonstrating specificity.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Hess PR, Barnes C, Woolard MD, Johnson MD, Cullen JM, Collins EJ, Frelinger JA (2007) Selective deletion of antigen-specific CD8+ T cells by MHC class I tetramers coupled to the type I ribosome-inactivating protein saporin. Blood 109:3300-3307. doi: 10.1182/blood-2006-06-028001

Objective: To discover if pathogenic T cells could be selectively deleted.

Summary: A single injection of the SAP-coupled tetramer eliminated more than 75% of cognate, but not control, T cells. This work demonstrates the therapeutic potential of cytotoxic tetramers to selectively eradicate pathogenic clonotypes while leaving overall T-cell immunity intact.

Usage: Streptavidin-SAP-coupled biotinylated tetramers were administered at low (22.2 pM) or high (66.6 pM) dose. Following the addition of Saporin Goat Polyclonal, affinity-purified FITC-labeled, T cells were subsequently incubated at either 37°C or 4°C, which permitted or prohibited endocytosis, respectively.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Read the featured article in Targeting Trends.

Yip WL, Weyergang A, Berg K, Tonnesen HH, Selbo PK (2007) Targeted delivery and enhanced cytotoxicity of cetuximab-saporin by photochemical internalization in EGFR-positive cancer cells. Mol Pharm 4(2):241-251. doi: 10.1021/mp060105u

Summary: Photochemical internalization (PCI) releases macromolecules from endocytic vesicles using photosensitizer activation by light. This technique allows the release of endocytosed molecules before degradation occurs in the lysosome. The authors demonstrate the proof-of-concept for this technique by combining biotinylated cetuximab (a chimeric monoclonal antibody to the EGFr) with streptavidin-ZAP (Cat. #IT-27). The conjugate was applied to three different human cancer cell lines, demonstrating enhanced specificity and toxicity against cells expressing the EGFr.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Fransson J, Borrebaeck CA (2006) The nuclear DNA repair protein Ku70/80 is a tumor-associated antigen displaying rapid receptor mediated endocytosis. Int J Cancer 119(10):2492-2496. doi: 10.1002/ijc.22212

Summary: The protein Ku70/80 is expressed in the nucleus of all cells. Tumor cell lines, however, have been shown to express Ku70/80 on the cell surface. In this study, the authors show that Ku70/80 is internalized into pancreatic carcinoma cells upon binding of the antibody INCA-X. INCA-X was combined with Mab-ZAP (Cat. #IT-04) and applied to several pancreatic carcinoma cell lines in vitro. Cell death in some of the treated lines demonstrates the potential of Ku70/80 as a therapeutic target.

Related Products: Mab-ZAP (Cat. #IT-04)

Collins BE, Blixt O, Han S, Duong B, Li H, Nathan JK, Bovin N, Paulson JC (2006) High-affinity ligand probes of CD22 overcome the threshold set by cis ligands to allow for binding, endocytosis, and killing of B cells. J Immunol 177(5):2994-3003. doi: 10.4049/jimmunol.177.5.2994

Objective: To demonstrate the dynamic equilibrium that exists between CD22 (Siglec-2) and its cis and trans ligands, using a high-affinity multivalent sialoside probe that competes with cis ligands and binds to CD22 on native human and murine B cells.

Summary: The CD22 (Siglec-2) preferred ligand: sequence Siaa2-6Gal that is abundantly expressed on N-linked glycans of B cell glycoproteins. Conjugation of the sialoside probes to the toxin saporin resulted in toxin uptake and toxin-mediated killing of B lymphoma cell lines, suggesting an alternative approach for targeting CD22 for treatment of B cell lymphomas.

Usage: Cytotoxicity assay: BJAB lymphoma cell killing required both the targeting probe and the Streptavidin-ZAP, as no killing was observed in the absence of either.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Adam PJ, Terrett JA, Steers G, Stockwin L, Loader JA, Fletcher GC, Lu LS, Leach BI, Mason S, Stamps AC, Boyd RS, Pezzella F, Gatter KC, Harris AL (2006) CD70 (TNFSF7) is expressed at high prevalence in renal cell carcinomas and is rapidly internalised on antibody binding. Br J Cancer 95(3):298-306. doi: 10.1038/sj.bjc.6603222

Summary: Renal cell carcinoma (RCC) is usually resistant to chemotherapy. Using a proteomics approach, the authors found a potential target for immunotherapy in RCC. An antibody against CD70, a type II transmembrane receptor, was combined with Hum-ZAP (Cat. #IT-22). The complex was then added to an RCC-derived cell-line in vitro. The aCD70/Hum-ZAP complex demonstrated significant killing at several different concentrations. This work suggests that CD70 is a potential target antigen for RCC therapy.

Related Products: Hum-ZAP (Cat. #IT-22)

Nguyen DH, Ball ED, Varki A (2006) Myeloid precursors and acute myeloid leukemia cells express multiple CD33-related Siglecs. Exp Hematol 34(6):728-735. doi: 10.1016/j.exphem.2006.03.003

Summary: Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of cell surface receptors which bind to sialic acid. They are found mainly on leukocytes, and also on acute myeloid leukemia (AML) cells. The authors tested several anti-Siglec antibodies against U937 histiocytic lymphoma cells and THP-1 acute monocytic leukemia cells in vitro. When these antibodies were combined with Mab-ZAP (Cat. #IT-04), a second immunotoxin, the target cells were eliminated. The data suggest that Siglecs may be a viable target for AML therapy.

Related Products: Mab-ZAP (Cat. #IT-04)

Kohls M (2006) Evaluate Potential Targeting Molecules. Nature Methods

Summary: Targeted toxins — targeting agents conjugated to saporin — are widely used to eliminate specific cell populations both in vitro and in vivo. For these molecules to be effective, it is vital that the targeting component of the conjugate specifically binds the cells of interest. A secondary conjugate, Streptavidin-ZAP, has been created by attaching the toxin saporin to streptavidin. The user can combine primary biotinylated material with Streptavidin-ZAP to quickly and economically screen potential targeting molecules for internalization and specificity. Once the appropriate targeting molecule is identified, a direct conjugation with saporin can be performed.

Related Products: Streptavidin-ZAP (Cat. #IT-27)

Read the article.

Weyergang A, Selbo PK, Berg K (2006) Photochemically stimulated drug delivery increases the cytotoxicity and specificity of EGF-saporin. J Control Release 111(1-2):165-173. doi: 10.1016/j.jconrel.2005.12.002

Summary: In this study the authors investigated the use of photosensitizers located in endocytic vesicles that can be induced to release macromolecules upon activation by light. This process is called photochemical internalization, or PCI. Biotinylated EGF was combined with streptavidin-ZAP (Cat. #IT-27), and the compound was applied to various cell lines. The data shows that PCI increases the toxicity of EGF-saporin significantly in EGF receptor-expressing cell lines.

Related Products: Streptavidin-ZAP (Cat. #IT-27)