Recombinant human granulocyte colony-stimulating factor augments cytotoxicity of OK-432-induced polymorphonuclear leukocytes

Polymorphonuclear neutrophils and cancer: intense and sustained neutrophilia as a treatment against solid tumors

Polymorphonuclear neutrophils (PMN) are the most abundant circulating immune cells and represent the first line of immune defense against infection. This review of the biomedical literature of the last 40 years shows that they also have a powerful antitumoral effect under certain circumstances. Typically, the microenvironment surrounding a solid tumor possesses many of the characteristics of chronic inflammation, a condition considered very favorable for tumor growth and spread. However, there are many circumstances that shift the chronic inflammatory state toward an acute inflammatory response around a tumor. This shift seems to convert PMN into very efficient anticancer effector cells. Clinical reports of unexpected antitumoral effects linked to the prolonged use of granulocyte colony-stimulating factor, which stimulates an intense and sustained neutrophilia, suggest that an easy way to fight solid tumors would be to encourage the development of intense peritumoral PMN infiltrates. Specifically designed clinical trials are urgently needed to evaluate the safety and efficacy of such drug-induced neutrophilia in patients with solid tumors. This antitumoral role of neutrophils may provide new avenues for the clinical treatment of cancer.

PSK and OK-432-induced immunomodulation of inducible nitric oxide (NO) synthase gene expression in mouse peritoneal polymorphonuclear leukocytes and NO-mediated cytotoxicity

We investigated whether PSK (a polysaccharide from the mycelia of Coriolus versicolor) or OK-432 (a streptococcal preparation) can up-regulate inducible nitric oxide synthase (iNOS) gene expression and nitric oxide (NO) production in mouse peritoneal polymorphonuclear leukocytes (PMNs). Six hrs after intraperitoneal injection of mice with PSK (2,500 microg/mouse) or OK-432 (100 microg/mouse), mouse peritoneal PMNs were restimulated with PSK (500 microg/ml) or OK-432 (10 microg/ml) plus 100 U/ml of mouse interferon-gamma (IFN-gamma) in vitro. Northern blot analysis showed strong synergism between both PSK and OK-432 and IFN-gamma for the induction of iNOS gene expression. NO production by PMNs was increased up to 20 microM (2 microM/10(6) PMNs/24 hrs) as measured by the Griess reagent method when PMNs were restimulated with PSK or OK-432 plus IFN-gamma for 24 hrs, although tumor cell killing was not detected. NO concentrations of more than 80 microM were required for P815 tumor cell killing. These results suggest that PMNs produce NO after stimulation with PSK or OK-432 in combination with IFN-gamma and may regulate the immune system in vivo, although the NO production induced by these agents is insufficient for tumor cell killing in vitro.

Treatment of neoplastic meningeal xenografts by intraventricular administration of an antiganglioside monoclonal antibody, 3F8

Leptomeningeal (LM) neoplastic metastases are painful, debilitating and inevitably lethal. Intrathecal (IT) anti-tumor antibodies may have therapeutic potential. We evaluated 3F8, an anti-G(D2) murine IgG(3) monoclonal antibody (MAb) in the treatment of human melanoma (SKMEL-1) and neuroblastoma (NMB7) xenografts in athymic rats. Both tumors were lysed efficiently in vitro by 3F8 in the presence of rat neutrophils or rat complement. Antibody-dependent cellular cytotoxicity (ADCC) was not augmented by recombinant human GM-CSF (rhGM-CSF), rhG-CSF, recombinant rat MIP-2 (rrMIP-2) or lipopolysaccharide (LPS). In vivo, continuous intraventricular administration of 3F8 and LPS prevented tumor engraftment, retarded tumor growth and eradicated 3-day-old established xenografts whereas 3F8 alone, LPS alone or F(ab)'(2) plus LPS had no or only marginal effects. Tumor establishment in brain was completely prevented in 36% of animals implanted with SKMEL-1 and 65% of animals implanted with NMB7. Twenty percent of established xenografts around the brain were eradicated but all animals had persistent tumor in the lumbosacral meninges despite treatment. Continuous intraventricular infusion of LPS produced a variable polymorphonuclear (PMN) pleocytosis that was dose-dependent. Continuous intraventricular infusion of 3F8 produced immunohistochemically detectable attachment to 86% of persistent brain deposits of tumor but <1% of spinal lumbosacral deposits. We conclude that regional therapy with anti-G(D2) MAb could target neutrophils to inhibit LM tumor growth. However, optimal activation and mobilization of neutrophils into the cerebrospinal fluid (CSF) and improved penetration of MAb to tumor sites remain critical variables.

Combination chemo-immunotherapy of murine solid tumor with OK-432, G-CSF, IL-2, and chemotherapeutics

An experimental tumor model was previously established in which BALB/c mice could survive the otherwise fatal intraperitoneal (i.p.) inoculation of BAMC-1 fibrosarcoma cells if the mice were treated with five sequential i.p. injections of OK-432 (a potent BRM) starting 2 days after tumor inoculation. In the present study, although a single i.p. injection of OK-432 alone on day 2 was not enough to cure the tumor-bearing mice, a combination therapy, an injection of OK-432 (5 mg/kg) on day 2 followed by injection of G-CSF (50 micrograms/kg) on day 3, could eradicate the tumor cells in more than 80% of the mice. In contrast to this ascites tumor model, solid tumors induced by intradermal transplantation of BAMC-1 tumor cells were resistant to the combined treatments with OK-432 and G-CSF, dying within 60 days. However, when these mice received a combined chemoimmunotherapy with cisplatin, OK-432, G-CSF and IL-2, starting on day 4, the tumors had regressed, and were completely eradicated. When the same treatment was started as late as day 8, no significant therapeutic effect was observed. Even at this advanced stage, however, it was found that a similar chemo-immunotherapy protocol using CAP-D (cyclophosphamide, epirubicin and DWA2114R) in lieu of cisplatin was extremely effective, achieving the eradication of tumors in more than 70% of the mice. These results indicated that the combination therapy with OK-432, G-CSF, IL-2, and chemotherapeutics could achieve a potent anti-tumor effect against the solid tumor, even at the advanced stage. Subsequent experiments using athymic nude mice transplanted with the tumor cells revealed that the same combination therapy showed weak tumor-regressing effects without achieving a complete cure. These results suggest that T-cells are key effectors in this type of chemo-immunotherapy of malignant tumors.