title: Virulizin, a novel immunotherapy agent, activates NK cells through induction of IL-12 expression in macrophages.
abstract: Virulizin, a novel biological response modifier, has demonstrated significant antitumor efficacy in a variety of human tumor xenograft models including melanoma, pancreatic cancer, breast cancer, ovarian cancer and prostate cancer. The significant role of macrophages and NK (Natural killer) cells was implicated in the antitumor mechanism of Virulizin where expansion as well as increased activity of macrophages and NK cells were observed in mice treated with Virulizin. Depletion of macrophages compromised Virulizin-induced NK1.1+ cell infiltration into xenografted tumors and was accompanied by reduced antitumor efficacy. In the present study, involvement of macrophages in NK cell activation was investigated further. We found that depletion of NK cells in CD-1 nude mice by anti-ASGM1 antibody significantly compromised the antitumor activity of Virulizin. Cytotoxicity of NK cells isolated from Virulizin-treated mice was enhanced against NK-sensitive YAC-1 cells and C8161 human melanoma cells, but not against NK-insensitive P815 cells. An increased level of IL-12beta was observed in the serum of mice treated with Virulizin. IL-12 mRNA and protein levels were also increased in peritoneal macrophages isolated from Virulizin-treated mice. Moreover, Virulizin-induced cytotoxic activity of NK cells isolated from the spleen was abolished when an IL-12 neutralizing antibody was co-administered. In addition, depletion of macrophages in mice significantly impaired Virulizin-induced NK cell cytotoxicty. Taken together, the results suggest that Virulizin induces macrophage IL-12 production, which in turn stimulates NK cell-mediated antitumor activity.
authors.affiliation: Research and Development Department, Lorus Therapeutics Inc., 2 Meridian Road, Toronto, ON, Canada M9W4Z7.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Ming Y
authors.initials: MY
authors.lastname: Cao
authors.forename: Yoon
authors.initials: Y
authors.lastname: Lee
authors.forename: Vivian
authors.initials: V
authors.lastname: Lee
authors.forename: Ningping
authors.initials: N
authors.lastname: Feng
authors.forename: Tania
authors.initials: T
authors.lastname: Benatar
authors.forename: Hongnan
authors.initials: H
authors.lastname: Jin
authors.forename: Ming
authors.initials: M
authors.lastname: Wang
authors.forename: Sandy
authors.initials: S
authors.lastname: Der
authors.forename: Jim A
authors.initials: JA
authors.lastname: Wright
authors.forename: Aiping H
authors.initials: AH
authors.lastname: Young
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D001646:Bile; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic; D005260:Female; D006801:Humans; D018664:Interleukin-12 / Q000235:genetics*; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects*; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology; D051379:Mice; D009368:Neoplasm Transplantation; D012333:RNA, Messenger / Q000032:analysis; D014020:Tissue Extracts; D014183:Transplantation, Heterologous
chemical_list: D000276:Adjuvants, Immunologic; D012333:RNA, Messenger; D014020:Tissue Extracts; C087098:virulizin; D018664:Interleukin-12