The effect of zymosan-induced generalized inflammation on tumor-growth in a rat renal-cell carcinoma model

We investigated the inhibition of tumour growth by induction of a generalized inflammatory response. 45 Lewis rats were randomly divided in three groups. A rat renal cell carcinoma was transplanted subcutaneously on day one in group I and group II. When the tumour became measurable on day 16, a generalized inflammation was induced by intraperitoneal injection with a suspension of zymosan and paraffin in group I and in group III, consisting of non-tumour bearing animals. Group II was inoculated with paraffin only. Seven and 14 days following intraperitoneal injection two rats out both group I and group II were sacrificed in order to obtain tumour biopsies at different stages of a generalized inflammatory response. Spontaneous mortality occurred twice in group III, consisting of non-tumour bearing animals. On day 37 all surviving rats were killed. Microscopical examination was carried out on all tumours and on lungs, liver, spleen and kidneys. A generalized inflammation response was confirmed in group I and III through biologic and microscopic parameters. After a zymosan induced generalized inflammation response in the rat, tumour growth rate was significantly lower compared with paraffin treated animals.