title: Antitumor effect of Nocardia rubra cell wall skeleton on syngeneically transplanted P388 tumors.
abstract: The antitumor activity of the immunomodulator, Nocardia rubra cell wall skeleton (N-CWS), was investigated using syngeneically transplanted P388 leukemia cells in a solid form. The s.c. growth of P388 tumors in DBA/2 mice was significantly suppressed by systemically administered N-CWS, and the effect was dose dependent. The antitumor effect of N-CWS was partially but significantly abrogated in splenectomized mice but not in T-cell or natural killer cell-deficient mice. Although spleen cells from mice treated with 1600 micrograms N-CWS contained no cytolytic activity, they exerted a significant cytostatic effect on P388 cell growth both in vitro and in vivo. Splenic cytostatic activity did not reside in T- or natural killer cells, but in plastic adherent cell population, macrophages. The response to N-CWS immunotherapy appeared to be associated with the number of macrophages infiltrating into the tumor lesions, and this was confirmed by histological analysis showing that P388 tumors from N-CWS-treated mice were intensively and dominantly infiltrated by macrophages. Furthermore, these were shown to be strongly tumor necrosis factor-positive by immunohistochemical analysis. These findings indicate that macrophages are the main effector cells playing a critical role in the suppression of P388 tumor growth in DBA/2 mice, and that tumor necrosis factor produced by these cells may be involved in the macrophage-mediated cytostatic effect induced by N-CWS. The fact that N-CWS suppressed the growth of weakly immunogenic P388 cells in syngeneic DBA/2 mice even when it was systemically injected would support the clinical potential of this agent.
authors.affiliation: Exploratory Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Ibaraki, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Izumi
authors.forename: T
authors.initials: T
authors.lastname: Ogawa
authors.forename: M
authors.initials: M
authors.lastname: Miyauchi
authors.forename: K
authors.initials: K
authors.lastname: Fujie
authors.forename: M
authors.initials: M
authors.lastname: Okuhara
authors.forename: M
authors.initials: M
authors.lastname: Kohsaka
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D002455:Cell Division / Q000502:physiology; D002473:Cell Wall / Q000276:immunology; D004305:Dose-Response Relationship, Drug; D005260:Female; D007111:Immunity, Cellular; D016219:Immunotherapy, Adoptive; D007694:Killer Cells, Natural / Q000502:physiology; D007941:Leukemia P388 / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008811:Mice, Inbred DBA; D009368:Neoplasm Transplantation; D009615:Nocardia / Q000276:immunology* / Q000648:ultrastructure; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013156:Splenectomy; D013601:T-Lymphocytes / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D000276:Adjuvants, Immunologic; D014409:Tumor Necrosis Factor-alpha