The occurrence of
tumor-associated
glycosphingolipids (GSLs) has been documented in a variety of
cancer tissues (Hakomori, 1984, 1985, 1989). In the case of
small-cell lung cancer (SCLC), the monosialoganglioside IV2Fuc-II3NeuAc-Gg4Cer (Fuc-GM1; short notations of
gangliosides are according to Svennerholm, 1963), first described from bovine liver (Wiegandt, 1973), was found to be a unique
tumor-associated GSL (Nilsson et al., 1984). It is present in up to 90% of all SCLC cases as compared with 25% frequency in non-SCLC, and no occurrence in normal lung (Brezicka et al., 1989, 1992). Thus, Fuc-GM1 may represent a suitable target
antigen for
immunotherapy of SCLC, and successful experiments have been performed showing
tumor-cell killing by
monoclonal antibodies (MAbs) against Fuc-GM1, both in vitro and, in a mouse model, in vivo (Brezicka et al., 1991). However, an effective
tumor vaccination in humans would require this
antigen to be expressed by the primary
tumor and also by all
metastases. The co-expression of Fuc-GM1 has already been reported in primary
tumors and in most but not all
metastases of SCLC (Hanquing et al., 1986; Nilsson et al., 1986; Brezicka et al., 1989). In view of the significance this
ganglioside may have for possible immunotherapeutical approaches to SCLC and of the difficulty in obtaining a sufficient number of samples for analysis, a re-assessment of Fuc-GM1 expression was made in SCLC primary
tumors and their
metastases, as well as in established SCLC cell lines. In addition, the possible presence of such
gangliosides, that might help to explain the selective
tetanus-toxin binding of SCLC cells (Critchley et al., 1986; Heymanns et al., 1989) was investigated. Finally, the typical occurrence of
sulfatide in all SCLC tissues and cell lines could be established.