Antitumor effect of OK-432-derived DNA: one of the active constituents of OK-432, a streptococcal immunotherapeutic agent.
OK-432 is a Streptococcus-derived immunotherapeutic agent for malignancies. Our group has tried to identify the effective components of OK-432 and has succeeded in isolating a lipoteichoic acid-related preparation designated as OK-PSA, which is a strong inducer of T helper 1 (T(H)1) cells, and elicits an anticancer effect via Toll-like receptor (TLR) 4. Conversely, bacterial DNA with unmethylated CpG motifs can stimulate a T(H)1-type host response via TLR9. The unmethylated CpG DNA contained in OK-432 may play a role in its anticancer effect. In the current study, we investigated the effect of OK-432-derived DNA (OK-DNA) in augmenting the anticancer immune response. Analysis of OK-DNA with the restriction enzymes Hpa II and MspI revealed that OK-DNA contained unmethylated CpG motifs. OK-DNA induced TH1-type cytokines such as interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-12, and IL-18 and augmented killer cell activities in vitro on human peripheral blood mononuclear cells, whereas the methylated OK-DNA did not. Cytokines were also produced by OK-DNA-stimulated splenocytes derived from wild-type mice but not from TLR9-deficient mice. In the in vivo study, peritumoral administration of OK-DNA resulted in a significant inhibition of tumor growth in syngeneic tumor-bearing wild-type and TLR4-deficient mice but not in TLR9-deficient mice. The antitumor effect of OK-432 in TLR9-deficient mice was significantly but partially reduced compared with that in wild-type mice, whereas the effect of OK-432 was almost completely eliminated in TLR4-deficient mice. These findings suggest that unmethylated CpG DNA in OK-432 functions as an active component in OK-432-induced anticancer immunity via TLR9.
Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, Tokushima, Japan.
Tetsuya
T
Oshikawa
Masato
M
Okamoto
Tomoyuki
T
Tano
Akiko
A
Sasai
Shin
S
Kan
Yoichiro
Y
Moriya
Yoshiki
Y
Ryoma
Motoo
M
Saito
Shizuo
S
Akira
Mitsunobu
M
Sato
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D018899:CpG Islands; D003602:Cytotoxicity, Immunologic / Q000187:drug effects* / Q000276:immunology; D019175:DNA Methylation; D004269:DNA, Bacterial / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D007167:Immunotherapy; D051379:Mice; D009154:Mutation; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000276:immunology; D010844:Picibanil / Q000737:chemistry* / Q000494:pharmacology*; D013297:Streptococcus pyogenes; D018417:Th1 Cells / Q000187:drug effects / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D051217:Toll-Like Receptor 9 / Q000276:immunology
D000970:Antineoplastic Agents; D004269:DNA, Bacterial; C493487:Tlr4 protein, mouse; C495370:Tlr9 protein, mouse; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9; D010844:Picibanil