Suppressive Effect of Recombinant TNF-gelatin Conjugate on Murine Tumour Growth In-vivo

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Abstract
A recombinant human tumour necrosis factor α (TNF) was conjugated to gelatin by means of carbodiimide to improve the in-vivo stability of TNF. About 55% of TNF activity was retained after gelatin conjugation as judged by the cytotoxicity assay using L-M cells in-vitro. Intraperitoneal injection of the TNF-gelatin conjugate significantly suppressed the in-vivo growth of murine Meth A fibrosarcoma cells (SS2 cells) in mouse peritoneum, in comparison with that of free TNF at the same dosage (P < 0·05). After intraperitoneal injection, TNF activity of the conjugate was detected in both the serum and the peritoneal cavity of mice for a longer period than was free TNF, irrespective of the presence of SS2 cells. Chromatographic studies of the conjugate demonstrated that the increase in the apparent molecular weight of TNF was consistent with gelatin conjugation. It is likely that this leads to a prolonged retention of TNF activity in-vivo. In addition, the TNF-gelatin conjugate suppressed the in-vitro growth of SS2 cells to the same extent as free TNF. Thus, it is possible that the longer retention period of the conjugate brought about an increase in the chance of contact between TNF and SS2 cells, resulting in the enhanced suppressive effect of TNF on in-vivo tumour cell growth. Gelatin conjugation is an effective method for increasing the in-vivo antitumour activity of TNF.