Intracerebral CpG immunotherapy with carbon nanotubes abrogates growth of subcutaneous melanomas in mice.
OBJECTIVE
Recently, we showed that intratumoral delivery of low-dose, immunostimulatory CpG oligodeoxynucleotides conjugated with carbon nanotubes (CNT-CpG) was more effective than free CpG and not only eradicated intracranial (i.c.) gliomas but also induced antitumor immunity that protected mice from subsequent i.c. or systemic tumor rechallenge. Here, we examined whether the same "intracerebral immunotherapy" strategy could be applied to the treatment of metastatic brain tumors.


METHODS
Mice with both i.c. and s.c. melanomas were injected intratumorally with CNT-CpG into either location. Antitumor responses were assessed by flow cytometry, bioluminescent imaging, and animal survival.


RESULTS
When given s.c., CNT-CpG response was mostly local, and it only modestly inhibited the growth of i.c. melanomas. However, i.c. CNT-CpG abrogated the growth of not only brain but also s.c. tumors. Furthermore, compared with s.c. injections, i.c. CNT-CpG elicited a stronger inflammatory response that resulted in more potent antitumor cytotoxicity and improved in vivo trafficking of effector cells into both i.c. and s.c. tumors. To investigate factors that accounted for these observations, CNT-CpG biodistribution and cellular inflammatory responses were examined in both tumor locations. Intracranial melanomas retained the CNT-CpG particles longer and were infiltrated by Toll-like receptor (TLR-9)-positive microglia. In contrast, myeloid-derived suppressive cells were more abundant in s.c. tumors. Although depletion of these cells before s.c. CNT-CpG therapy enhanced its cytotoxic responses, antitumor responses to brain melanomas were unchanged.


CONCLUSIONS
These findings suggest that intracerebral CNT-CpG immunotherapy is more effective than systemic therapy in generating antitumor responses that target both brain and systemic melanomas.
Department of Neurosurgery, Provincial Hospital Affiliated to Shandong University, Jinan, PR China.
Haitao
H
Fan
Ian
I
Zhang
Xuebo
X
Chen
Leying
L
Zhang
Huaqing
H
Wang
Anna
A
Da Fonseca
Edwin R
ER
Manuel
Don J
DJ
Diamond
Andrew
A
Raubitschek
Behnam
B
Badie
D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D001932:Brain Neoplasms / Q000188:drug therapy; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D006801:Humans; D007167:Immunotherapy; D008545:Melanoma / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D037742:Nanotubes, Carbon; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage / Q000276:immunology; D014018:Tissue Distribution
D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D037742:Nanotubes, Carbon; D009838:Oligodeoxyribonucleotides