Oral administration of poly-gamma-glutamate induces TLR4- and dendritic cell-dependent antitumor effect.
Previously, we reported that the oral administration of high molecular mass poly-gamma-glutamate (gamma-PGA) induced antitumor immunity but the mechanism underlying this antitumor activity was not understood. In the present study, we found that application of high molecular mass gamma-PGA induced secretion of tumor necrosis factor (TNF)-alpha from the bone-marrow-derived macrophages of wild type (C57BL/6 and C3H/HeN) and Toll-like receptor 2 knockout (TLR2(-/-)) mice, but not those of myeloid differentiation factor 88 knockout (MyD88(-/-)) and TLR4-defective mice (C3H/HeJ). Production of interferon (IFN)-gamma-inducible protein 10 (IP-10) in response to treatment with gamma-PGA was almost abolished in C3H/HeJ mice. In contrast to LPS, gamma-PGA induced productions of TNF-alpha and IP-10 could not be blocked by polymyxin B. Furthermore, gamma-PGA-induced interleukin-12 production was also impaired in immature dendritic cells (iDCs) from MyD88(-/-) and C3H/HeJ mice. Downregulation of MyD88 and TLR4 expression using small interfering RNA (siRNA) significantly inhibited gamma-PGA-induced TNF-alpha secretion from the RAW264.7 cells. Gamma-PGA-mediated intracellular signaling was markedly inhibited in C3H/HeJ cells. The antitumor effect of gamma-PGA was completely abrogated in C3H/HeJ mice compared with control mice (C3H/HeN) but significant antitumor effect was generated by the intratumoral administration of C3H/HeN mice-derived iDCs followed by 2,000 kDa gamma-PGA in C3H/HeJ. These findings strongly suggest that the antitumor activity of gamma-PGA is mediated by TLR4.
Lee
Tae-Young
TY
Mucosal Immunology Laboratory, BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea.
Kim
Yang-Hyun
YH
Yoon
Sun-Woo
SW
Choi
Jai-Chul
JC
Yang
Jai-Myung
JM
Kim
Chul-Joong
CJ
Schiller
John T
JT
Sung
Moon-Hee
MH
Poo
Haryoung
H
D000284:Administration, Oral; D000818:Animals; D002460:Cell Line; D054357:Chemokine CXCL10 / Q000096:biosynthesis; D003713:Dendritic Cells / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D008262:Macrophage Activation / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D053594:Myeloid Differentiation Factor 88 / Q000502:physiology; D011099:Polyglutamic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000502:physiology*
D054357:Chemokine CXCL10; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C030315:poly-gamma-methylglutamate; D011099:Polyglutamic Acid