Immunohistochemical studies on local antitumor effects of streptococcal immunopotentiator, OK-432, in human solid malignant tumors.

Immunocytochemical techniques were used to clarify the local inhibitory effects of a streptococcal immunopotentiator, OK-432, against solid malignant tumor growth. Natural killer (NK) cells and fibronectin were chosen as immunostaining markers to demonstrate the antitumor effects. Immunocytochemical staining was performed by the avidin-biotin-peroxidase complex method. These investigations demonstrated that (1) local administration of OK-432 seems to promote a marked induction of NK cells and fibroblasts around or entering into the cancerous lesions and (2) the cancer cell-killing effect of NK cells and the fibronectin-enriched stromal reaction augmented by the injection of OK-432 suggest at least the possibility of protection against neoplastic growth with invasion and the spread of distant or nodal metastases of solid carcinomas.