[Experimental studies of effects of the streptococcal anticancer preparation (Picibanil) for bladder carcinomas of ACI/N rats (author's transl)]

Cytokine-mediated antitumor effect of OK-432 on urinary bladder tumor cells in vitro

Fatal complications from the intravesical instillation of bacillus Calmette-Guérin (BCG) for the treatment of superficial urinary bladder tumors have been reported. OK-432, an immunomodulating agent like BCG, may be an effective and safe agent for the treatment of urinary bladder tumors. We investigated the cytokine-mediated antitumor effect of OK-432 on established human bladder cancer cell lines (T24 and KK-47) in vitro. Peripheral blood mononuclear cells (PBMCs) from a healthy volunteer were cultured with OK-432 for various periods, and the culture supernatants were used as conditioned media. Cytokines in the culture supernatants were quantified. The antitumor effect of OK-432 was evaluated by colony-forming assays, using the conditioned media as the culture media. The colony survival of T24 and KK-47 cells was significantly inhibited by conditioned media from 24-h cultures of PBMCs incubated with OK-432 at concentrations of 0.05 and 0.1 Klinische Einheit (KE)/ml. Conditioned media from PBMCs cultivated with OK-432 for 7 days at 0.01 and 0.05 KE/ml also significantly inhibited the colony survival of both cell lines. Higher concentrations of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) were detected in conditioned media cultivated with OK-432 for 24 h than in media from PBMCs alone. However, higher concentrations of interferon gamma (IFN gamma) were detected in conditioned media cultivated with OK-432 for 7 days. Approximately 90% of the inhibition of KK-47 cells by the 24-h conditioned media was neutralized by an anti-TNF monoclonal antibody. The inhibition of T24 cells was neutralized approximately 50% by the same antibody. The inhibition of T24 and KK-47 cells by 7-day conditioned media was completely neutralized by an anti-IFN gamma monoclonal antibody. The cultivation of PBMCs with OK-432 inhibited the production of granulocyte-colony-stimulating factor (G-CSF) by PBMCs. The inhibition may play a role in the mechanism of the antitumor effect of OK-432. Urinary bladder tumor cell lines have different sensitivities to cytokines. The cytokines induced by OK-432 vary with the concentration of OK-432 and the culture period. It is suggested that in intravesical instillation of OK-432 for treatment of urinary bladder tumor, the optimal dose and interval of instillation should be considered.

OK432 inhibits experimental hepatic metastasis of colon adenocarcinoma ACL-15 in F344 rats

The effect of OK432 on hepatic metastasis, induced by inoculating 1 x 10(6) ACL-15 cells from a rat colon adenocarcinoma cell line into the ileocolic vein of male F344 rats, was investigated in this study. Metastases were detected 14 days after inoculation in the control rats, however, pretreatment 3 days prior to the tumor cell inoculation with an anti-asialoGM1 antibody, which eliminates natural killer (NK) cell activity in vitro, increased the number of hepatic metastases, shortened the survival time, and decreased the NK activity of the nonparenchymal liver cells (NPC). In contrast, pretreatment with OK432 2 days prior to tumor inoculation significantly decreased the number of hepatic metastases, prolonged the survival time, and augmented the NK activity of the NPC, although treatment with OK432 3 or 7 days after inoculation did not decrease the number of hepatic metastases. Moreover, NPC from the OK432-pretreated rats had a marked antitumor effect against ACL-15 cells in the Winn's neutralization test. The results of this study indicate that pretreatment with OK432 before tumor cell inoculation inhibits hepatic metastasis in this experimental model, possibly by augmentating liver-associated NK activity.

Induction of endogenous cytokines in ascites of patients with ovarian cancer by OK-432, a streptococcal preparation

To clarify the action mechanism of OK-432, OK-432 was intraperitoneally (i.p.) administered to 4 ovarian cancer patients with malignant ascites. In 2 of the 4 patients, 4 types of cytokines (tumor necrosis factor, interleukin 1 beta, interleukin 2, and interferon gamma) were induced in ascites after intraperitoneal injection of OK-432 (i.p. OK-432). In one of these patients, the ascitic supernatant after i.p. OK-432 significantly inhibited colony formation of autologous ascitic tumor cells; the amount of ascites decreased markedly, and the ascitic cytology became negative. In the other 2 patients, only interferon gamma was induced in ascites after i.p. OK-432. In these 2, ascitic supernatant did not inhibit colony formation of autologous ascitic tumor cells. These results indicated that i.p. OK-432 can induce various endogenous cytokines in malignant ascites and that these induced cytokines may contribute to the antitumor effect of i.p. OK-432.

Activated macrophages are responsible for the tumor-inhibitory effect in mice receiving intravenous injection of OK-432

Mouse spleen cells, either pretreated in vitro with 100 U/ml of OK-432-induced IFN gamma for 18 h or obtained from mice 24 or 48 h after i.v. injection of OK-432(100 micrograms/mouse), were examined for their anti-tumor effect by Winn's neutralization assay against Meth-A tumor cells in BALB/c mice. Spleen cells treated in vitro or obtained in vivo 24 h after i.v. injection clearly neutralized the growth of admixed Meth-A cells. Two booster injections of 200 U of IFN gamma near the tumor site accelerated this neutralizating effect. In order to determine the effector subpopulation, inhibitory spleen cells were treated with either anti-Thy-1 monoclonal antibody plus complement, anti-asialo GM1 serum plus complement or with adherence on plastic plates followed by Sephadex G-10 column treatment. The effector cell activity in Winn assay was lost only after the removal of macrophages through plastic plate adherence and Sephadex G-10 column treatment, but not after anti-Thy-1 or anti-asialo GM1 treatment, with either in vitro- or in vivo-treated spleen-cell populations. The growth of Meth-A cells was inhibited not only by these activated macrophages in Winn's assay, but also by adoptive transfer of OK-432-induced cytotoxic macrophages intralesionally 4 days after the implantation of 1 X 10(6) Meth-A cells. Our evidence suggests that the systemic action of OK-432 can be explained by the effect of induced IFNgamma, through the activation of macrophages.

Immunological evaluation of a streptococcal preparation (OK-432) in treatment of bladder carcinoma

When 21 patients with bladder cancer (transitional cell carcinoma) were given local and systemic injections of a streptococcal preparation, OK-432, tumor regression was observed in 3 cases (14.3%). The marked infiltration of lymphocytes observed on histological examination of regressed tumors suggested that a host-mediated action was involved in the antitumor effect of OK-432.