Trish K. Lankford

Evaluation of 225Ac for Vascular Targeted Radioimmunotherapy of Lung Tumors

Several alpha particle emitting radioisotopes have been studied for use in radioimmunotherapy. Ac-225 has the potential advantages of a relatively long half life of 10 days, and a yield of 4 alpha emissions in its decay chain with a total energy release of approximately 28 MeV. A new, 12 coordination site chelating ligand, HEHA, has been chemically modified for coupling to targeting proteins without loss of chelating ability. HEHA was coupled with MAb 201B which binds to thrombomodulin and accumulates efficiently in murine lung. Ac-225 was bound to the HEHA-MAb 201B conjugate and injected into BALB/c mice bearing lung tumor colonies of EMT-6 mammary carcinoma. Biodistribution data at 1 and 4 h postinjection indicated that, as expected, 225Ac was delivered to lung efficiently (> 300% ID/g). The 225Ac was slowly released from the lung with an initial t1/2 = 49 h, and the released 225Ac accumulated in the liver. Injection of free HEHA was only partially successful in scavenging free 225Ac. In addition to the slow release of 225Ac from the chelate, data indicated that decay daughters of 225Ac were also released from the lung. Immediately after organ harvest, the level of 213Bi, the third alpha-decay daughter, was found to be deficient in the lungs and to be in excess in the kidney, relative to equilibrium values. Injected doses of 225Ac MAb 201B of 1.0 microCi, delivering a minimum calculated absorbed dose of about 6 Gy to the lungs, was effective in killing lung tumors, but also proved acutely radiotoxic. Animals treated with 1.0 microCi or more of the 225Ac radioconjugate died of a wasting syndrome within days with a dose dependent relationship. We conclude that the potential for 225Ac as a radioimmunotherapeutic agent is compromised not only by the slow release of 225Ac from the HEHA chelator, but most importantly by the radiotoxicity associated with decay daughter radioisotopes released from the target organ.

Phage Display Selection of scFv to Murine Endothelial Cell Membranes

The diversity of endothelial cells is becoming more apparent and more important in defining vessel systems that supply blood to normal organs and to tumors. Reagents that identify expression of cell surface determinants on these cells are crucial for differentiating among different vessel types. As a first step in this process we have selected a panel of 25 scFvs from a phage display library that bind to the endothelial cell line LEII. The scFvs are of high affinity and bind to some tumor cells as well as to the target endothelial cell. The scFvs can be divided into 8 epitope groups by use of competition binding studies. DNA sequencing of the members of these groups generally support the classification. This work shows that phage display is a rapid and efficient method for identification of reagents for cell surface molecules.

A new monoclonal antibody to study mouse macrophage antigen during BHT-induced lung injury and repair.

A rat monoclonal antibody 133-13A to a mouse lung carcinoma cell line was found to react with macrophages in mouse lung [1]. This monoclonal antibody is different from previously described antibodies to macrophages. Immunogold electron-microscopy and immunoperoxidase light microscopy have been used to show that MoAb 133-13A binds specifically to macrophages in normal and in BHT treated mouse lungs. This MoAb recognizes a protein of approximately 100 kDa (P100) on cultured lung carcinoma cells and a 87 kDa protein on macrophages from lung or the peritoneal cavity which is different from other macrophage antigens. The surface glycoprotein has been purified from cultured cells using immunoaffinity chromatography. The purified protein was radioiodinated and MoAb 133-13A was used to develop a competition radioimmunoassay to quantitate P100. Spleen, intestines, lung, skin and uterus all have high levels of P100. P100 on peritoneal macrophages has been determined to be about 94,000 molecules/cell. Analyses of lung lavage and whole lung homogenates from mice treated with BHT, BHT plus 70% O2, and 70% O2 alone show that treated animals have elevated P100 content compared to corn oil treated mice.

A monoclonal antibody to a carbohydrate epitope expressed on glycolipid and on α3β1 integrin on human esophageal carcinoma

A mouse monoclonal antibody (MAb-9) produced by immunization with a human esophageal carcinoma cell line, TE-2 (derived from undifferentiated squamous cell carcinoma) reacted specifically with about 30% of esophageal carcinoma cell lines and tissue sections from clinical samples. MAb-9 showed minimal reactivity with normal esophageal tissue. 125I, fluorescent or gold particle labeled MAb-9 bound to TE-2 cell surfaces. 125I-radiolabeled MAb-9 was used to detect reactive material from cell extracts in Western blot. Treatment of TE-2 membrane proteins with neuraminidase, N-glycanase or O-glycanase reduced antigen detection. Treatment of cells with periodic acid destroyed antibody binding in ELISA. Lipid extracts from cell membranes, containing glycolipids, also reacted with MAb-9. MAb-9 was used to purify target antigen from detergent solubilized membrane proteins and the prominent bands from subsequent gel electrophoresis were trypsin digested and analyzed by mass spectrometry. Peptides from α3 and β1 integ...

Monoclonal Antibodies in Cancer Detection and Therapy

The advent of monoclonal antibodies has revolutionized thinking about cancer therapy management. In this article, the authors review some of the applications of monoclonal antibodies in cancer research and identify requirements for monoclonal antibody to be useful in cancer detection or therapy. Empirical tests of antibody circulation in vivo are necessary to establish specificity. 68 references, 3 figures.