The influence of zymosan and indomethacin on liver and kidney tumor growth. An experimental study in rats.

: Zymosan, a non-specific macrophage-stimulating agent, modifies favourably tumour growth in the liver but has minor effect on renal tumours. The mechanism accounting for variation is still to be clarified. The effect of zymosan on liver cancer may be mediated by the macrophage-monocyte system. Kupffer cells are in vitro cytotoxic against colon cancer cell lines. The kidney is sparse in macrophage elements. The prostaglandin synthesis inhibitor, indomethacin, inhibits tumor growth. In Wistar-FU rats inoculated in the liver and the kidney with an adenocarcinoma cell suspension, pretreatment with zymosan (3 mg x 100 g[-1]) significantly reduced both tumour take and liver volume. This effect was attenuated by concomitant administration of indomethacin (0.2 mg x 100 g[-1]). After 2 weeks there was still reduced liver tumour volume. No significant effects on tumour take or growth were observed when the cells were inoculated into the kidney. There was no significant effect of zymosan on an hepatoma in Lister-Hooded rats. Pretreatment with indomethacin had no effect on tumor take or initial growth.