Immune cell-mediated antitumor activities of GD2-targeted liposomal c-myb antisense oligonucleotides containing CpG motifs.
BACKGROUND
Expression of the c-myb proto-oncogene in neuroblastoma, the most common extracranial solid tumor of infancy, is linked with cell proliferation and differentiation. Neuroblastoma can be selectively targeted via monoclonal antibodies against the disialoganglioside (GD2) tumor-associated antigen. Liposomes coated with anti-GD2 antibodies (targeted liposomes) and entrapping a c-myb antisense oligonucleotide have antitumor activity. Because antisense oligonucleotides containing CpG motifs can stimulate immune responses, we evaluated the effect of CpG-containing c-myb antisense oligonucleotides encapsulated within targeted liposomes.


METHODS
Antisense (myb-as) and scrambled (myb-scr) control oligonucleotides with CpG motifs were encapsulated within GD2-targeted and non-targeted liposomes. Two murine (nude and SCID-bg) xenograft models of neuroblastoma were established. Mice (groups of 10) were injected intravenously with various oligonucleotide and liposome formulations, and life span, long-term survival, immune cell activation, and cytokine release were measured over time.


RESULTS
Tumor-bearing mice injected with targeted liposome-CpG-myb-as or targeted liposome-CpG-myb-scr lived longer than mice in any other group, although long-term survival (i.e., more than 120 days) was obtained only in mice injected with targeted liposome-CpG-myb-as. Splenocytes isolated from mice injected with targeted liposome-CpG-myb-as contained activated macrophages, B cells, and natural killer (NK) cells, but only activated NK cells were associated with antitumor cytotoxic activity. In vivo immune cell activation was accompanied by the time-dependent increases in plasma levels of the cytokines interleukin 12 (IL-12; maximum level reached by 2 hours) and interferon gamma (IFN-gamma; maximum level reached by 18 hours) and was dependent on the oligonucleotide CpG motif. Ablation of macrophages or NK cells resulted in a loss of in vivo antitumor activity.


CONCLUSIONS
Immune cell activation, involving the time-dependent activation of macrophages and NK cells, contributes to the antitumor activity of targeted liposome-CpG-myb-as against neuroblastoma and could improve the effectiveness of antitumor targeted liposomes.
Laboratory of Oncology, Gaslini Children's Hospital, Genoa, Italy.
Chiara
C
Brignole
Fabio
F
Pastorino
Danilo
D
Marimpietri
Gabriella
G
Pagnan
Angela
A
Pistorio
Theresa M
TM
Allen
Vito
V
Pistoia
Mirco
M
Ponzoni
D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics / Q000276:immunology; D016207:Cytokines / Q000378:metabolism; D005732:Gangliosides / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D020570:Genes, myb; D006801:Humans; D007275:Injections, Intravenous; D007694:Killer Cells, Natural / Q000276:immunology; D008081:Liposomes; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008819:Mice, Nude; D016513:Mice, SCID; D009447:Neuroblastoma / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000378:metabolism / Q000494:pharmacology*; D000090063:Proto-Oncogene Mas; D020598:Proto-Oncogene Proteins c-myb / Q000378:metabolism / Q000494:pharmacology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D014183:Transplantation, Heterologous
D000970:Antineoplastic Agents; D016207:Cytokines; D005732:Gangliosides; D008081:Liposomes; C000715470:MAS1 protein, human; D016376:Oligonucleotides, Antisense; D000090063:Proto-Oncogene Mas; D020598:Proto-Oncogene Proteins c-myb; C019403:ganglioside, GD2