“…Secretion of IL-2 (Fearon et al, 1990;Russell et al, 1991;Ley et al, 1991), (Tepper et al, 1989;Golumbek et al, 1991), y-interferon ('y-IFN) (Watanabe et al, 1989;Esumi et al, 1991), tumour necrosis factor-a (TNF-a) (Asher et al, 1991;Blankenstein et al, 1991), granulocyte colony stimulating factor (Colombo et al, 1991), or interleukin 7 (Hock et al, 1991;McBride et al, 1992) (Miller, 1992). As gene delivery to all cells within a tumour will probably not be feasible, cytokine secretion by some cells within a tumour would have to lead to the rejection of adjacent, unmodified cells for direct cytokine gene delivery to be effective.…”