Inhibitory effects of immunopotentiators on the enhancement of lung metastases induced by operative stress in rats.

To investigate the mechanism of tumor growth enhancement induced by operative stress, laparothoracotomy was performed on day 2 after tumor cell inoculation in rats associated with administration of various kinds of immunopotentiators. OK-432 (streptococcal preparation), PS-K (extract from mycelium of Coriolous versicolor), lentinan (extract from Lentinus edodus), levamisole and Corynebacterium parvum were administered intravenously or intraperitoneally in the fractionated form prior to or after inoculation. In general, administration of each immunopotentiator showed an inhibitory effect on the increase of lung metastases induced by laparothoracotomy. In particular, administration of lentinan prior to inoculation and that of levamisole after inoculation caused significant inhibition in the number of metastatic nodules on the lungs. The significance of the inhibitory effects is discussed.