OK-432 inhibited B16 melanoma growth and induced a TH₁ dominant state in tumor bearing mouse

Objective: To investigate the antitumor mechanisms of the streptococcal preparation OK-432. Methods: Using C57BL/6 mouse bearing B16 melanoma, we observed the antitumor activity of OK-432 and investigated the effect of OK-432 on multi-cytokine (IL-2, IL-4, IL-6, IL-10, IL-12, IFN-γ) production of mouse splenocyte both in vitro and in vivo. Results: As compared with control, OK-432 significantly inhibited B16 melanoma growth and lengthened mice survival time (P<0.05). In vitro OK-432 could stimulate splenocyte from tumor bearing mice to secrete IL-6, IL-12, IFN-γ and IL-10 remarkably (P<0.01). In vivo OK-432 led to the increased production of IL-2, IL-12 and IFN-γ but decreased production of IL-10 (P<0.05). When the splenocytes harvested from OK-432 treated mice were stimulated with OK-432 again in vitro, the production of IFN-γ increased and IL-10 decreased significantly (P<0.05). Conclusion: OK-432 could ' boost multiple cytokines production, especially IL-12 which skewed T cells in a Th₁ dominant state and enhanced the host antitumor activities.