Adoptive transfer of tumour-specific T lymphocytes loaded with
ricin into tumour-bearing mice exerts a transient
therapeutic effect against locally induced tumours [Cerundolo et al. (1987) Br J
Cancer 55: 413]. As transferred cells preferentially locate in the lung, we studied the
therapeutic effect of
ricin-loaded, lymphokine-activated killer (LAK) cells on lung
metastases induced by M4 or B16-F1 (F1) tumour cell injection. In vitro studies demonstrated that
ricin-treated LAK cells were about 100-fold more efficient than untreated LAK cells in inhibiting growth of the
ricin-sensitive M4 tumour cell line. This effect was most likely due to the released
ricin, as treated and untreated LAK cells inhibited the relatively toxin-resistant F1 cell line to the same extent.
Ricin treatment did not alter the tissue distribution of intravenously (i.v.) injected LAK cells, which selectively localized in the lung early after inoculation, whether or not
metastases were present. Adoptive transfer experiments showed that
ricin-treated LAK cells were significantly more efficient than untreated LAK cells in inhibiting M4- but not F1-induced lung
metastases. These results indicate that LAK cells are able to deliver a therapeutic concentration of
antineoplastic compounds directly to the lung.