Tetanus toxin as a marker for small-cell lung cancer cell lines

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Abstract
Tetanus toxin labeling of human lung cancer cell lines was investigated using direct and indirect immunofluorescence and immunohistochemical staining. Cells of characterized permanent cell lines, eight small-cell lung cancer (SCLC) cell lines of classic subtype, six SCLC cell lines of variant subtype and seven non-small-cell lung cancer (NSCLC) cell lines, were incubated with a saturating concentration of tetanus toxin. For staining, fluorescein-isothiocyanate-(FITC)-conjugated anti-(tetanus toxin) antibodies were used or a mouse monoclonal anti-(fragment C) antibody with subsequent binding of FITC-conjugated anti-(mouse Ig) antibody or peroxidase-antiperoxidase complex. Only SCLC showed an intense fluorescence/immunoreactivity restricted to the cell membrane. Quantitative analysis of tetanus toxin labeling by flow cytometry revealed the percentage of positive cells to be between 35% and 95% in SCLC without obvious differences between the classic and variant subtypes of SCLC. In NSCLC the percentage of positive cells was lower than 10%. These results demonstrate that SCLC in contrast to NSCLC can be labeled with tetanus toxin, emphasizing the neuroendocrine properties of this tumor, and that tetanus toxin labeling may become a useful diagnostic marker for SCLC cells in cytology.