Refinement of an indirect immunotoxin assay of monoclonal antibodies recognising the human small cell lung cancer cluster 2 antigen.
Monoclonal antibodies (Mabs) from the Second International Workshop on Small Cell Lung Cancer (SCLC) Antigens that recognise the cluster 2 SCLC-associated antigen mediated potent and selective cytotoxic effects in an indirect assay of immunotoxin cytotoxicity. In this assay, the NCI-H69 cell line was treated with each Mab at 4 degrees C, washed to remove unbound Mab, and then incubated at 37 degrees C in the presence of a fixed concentration, 1 x 10(-8) M, of the screening agent, sheep anti-mouse IgG-ricin A chain. The use of a fixed high concentration of screening agent led to a 300-fold overestimate of the potency of a cluster 2-directed immunotoxin, MOC-31-ricin A chain. In contrast, when the concentration of the screening agent was identical to the Mab concentration, a precise match to immunotoxin potency was obtained. MOC-31-ricin A chain selectivity inhibited the incorporation of [3H]leucine by the NCI-H69, SW2 and GLC-8 SCLC cell lines by 50% at a concentration between 3 x 10(-11) M and 3 x 10(-10) M, and by the NCI-H125 lung adenocarcinoma cell line at 7 x 10(-11) M, but exerted no selective toxic effects upon human lung and non-lung tumour cell lines lacking surface expression of the cluster 2 antigen.
Section of Immunology, Institute of Cancer Research, Sutton, Surrey, UK.
E J
EJ
Derbyshire
L
L
de Leij
E J
EJ
Wawrzynczak
D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D000951:Antigens, Neoplasm / Q000276:immunology*; D018288:Carcinoma, Small Cell / Q000188:drug therapy* / Q000276:immunology*; D006801:Humans; D000922:Immunotoxins / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000276:immunology*; D011237:Predictive Value of Tests; D012276:Ricin / Q000633:toxicity*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000922:Immunotoxins; D012276:Ricin