PARANEOPLASTIC ANTI-HU SERUM - STUDIES ON HUMAN TUMOR-CELL LINES

Patients with low titers of anti-Hu, the paraneoplastic encephalomyeli tis/sensory neuronopathy (PEM/PSN) antibody, have a better tumor progn osis that those who do not harbor these antibodies. Accordingly, we ex amined the effects of serum from patients with anti-Hu antibodies on h uman tumor cell lines, in order to determine: (1) if the serum was tox ic (growth inhibition or cytolysis) to tumor cells with or without com plement, and (2) if anti-Hu antibodies contributed to tumor toxicity. The serum of 14 patients with anti-Hu associated PEM/PSN, 22 patients with small-cell lung cancer (SCLC) without anti-Hu antibodies, and 20 normal individuals were studied. Three cell lines (NT-2, BE(2)-C, and SH.SY5Y) that express Hu proteins, and one cell line (SAOS-2) that doe s not, were studied, We examined the effects of whole serum, IgG-deple ted serum, and purified Ige in the presence or absence of complement. A higher percentage of anti-Hu sera were toxic (71%) compared with ser a from anti-Hu negative SCLC patients (23%) (p < 0.0001). No correlati on existed between the titer of anti-Hu antibodies and toxicity. The t oxic effects were observed in all tumor cell lines including the cell line that does not express Hu antigens. Toxicity persisted in serum de pleted of IgG. Purified Mti-Hu IgG in the presence and absence of comp lement, was not toxic. Our findings indicate that anti-Hu serum is tox ic for human tumor cell lines, but this toxicity does not appear to be mediated by anti-Hu antibodies. (C) 1997 Elsevier Science B.V.