The constituents of mycobacteria are an effective immune adjuvant, as observed with complete Freund's adjuvant. In this study, we demonstrated that the cell wall skeleton of Mycobacterium bovis bacillus CalmetteGuérin (BCG-CWS), a purified noninfectious material consisting of peptidoglycan, arabinogalactan, and mycolic acids, induces maturation of human dendritic cells (DC). Surface expression of CD40, CD80, CD83, and CD86 was increased by BCG-CWS on human immature DC, and the effect was similar to those of interleukin-1␤ (IL-1␤), tumor necrosis factor alpha (TNF-␣), heat-killed BCG, and viable BCG. BCG-CWS induced the secretion of TNF-␣, IL-6, and IL-12 p40. CD83 expression was increased by a soluble factor secreted from BCG-CWS-treated DC and was completely inhibited by monoclonal antibodies against TNF-␣. BCG-CWS-treated DC stimulated extensive allogeneic mixed lymphocyte reactions. The level of TNF-␣ secreted through BCG-CWS was partially suppressed in murine macrophages with no Toll-like receptor 2 (TLR 2) or TLR4 and was completely lost in TLR2 and TLR4 double-deficient macrophages. These results suggest that the BCG-CWS induces TNF-␣ secretion from DC via TLR2 and TLR4 and that the secreted TNF-␣ induces the maturation of DC per se.

We examined the inhibitory effect of two saponin preparations from Red ginseng, 20(R)- and 20(S)-ginsenoside-Rg3, in comparison with that of ginsenoside-Rb2, on lung metastasis produced by two highly metastatic tumor cells, B16-BL6 melanoma and colon 26-M3.1 carcinoma, in syngeneic mice. In an in vitro analysis, both saponin preparations showed a significant inhibition of adhesion to fibronectin (FN) and laminin (LM) by B16-BL6 melanoma. Similarly, they significantly inhibited the invasion of B16-BL6 cells into the reconstituted basement membrane (Matrigel)/FN in a dose-dependent manner. In an experimental metastasis model using B16-BL6 melanoma, consecutive intravenous (i.v.) administrations of 100 micrograms/mouse of 20(R)- or 20(S)-ginsenoside-Rg3 1, 2, 3 and 4 d after tumor inoculation led to a significant decrease in lung metastasis. The inhibitory effect of i.v. administration of both ginseng saponins on the tumor metastasis of B16-BL6 melanoma was also recognized in a low dose of 10 micrograms/mouse. The oral administration (p.o.) of both saponins (100-1000 micrograms/mouse) induced a significant decrease in lung metastasis of B16-BL6 melanoma. Moreover, both ginseng saponins were effective in inhibiting of lung metastasis produced by colon 26-M3.1 carcinoma. When 20(R)- or 20(S)-ginsenoside-Rg3 was orally administered consecutively after tumor inoculation in a spontaneous metastasis model using B16-BL6 melanoma, both of them significantly inhibited lung metastasis. In the experiment involving neovasculization by tumor cells in vivo, both mice groups given each saponin preparation after tumor inoculation exhibited a significant decrease in the number of blood vessels oriented toward the tumor mass, with no repression of tumor size. These findings suggest that both ginseng saponins, 20(R)- and 20(S)-ginsenoside-Rg3, possess an ability to inhibit the lung metastasis of tumor cells, and the mechanism of their antimetastatic effect is related to inhibition of the adhesion and invasion of tumor cells, and also to anti-angiogenesis activity.

We have investigated the effect of monoclonal antibodies (MAbs) specific for aminopeptidase N/CD13 on the invasion of human metastatic tumor cells into reconstituted basement membrane (Matrigel). The invasion of human metastatic tumor cells (SN12M renal-cell carcinoma, HT1080 fibrosarcoma and A375M melanoma) into Matrigel-coated filters was inhibited by an anti-CD13 MAb, WM15, in a concentration-dependent manner. However, this MAb did not have any effect on tumor-cell adhesion and migration to the extracellular matrices, which may be involved in tumor-cell invasion. MAb WM15 inhibited the degradation of type-IV collagen by tumor cells in a concentration-dependent manner. We also found that WM15 inhibited hydrolysing activities towards substrates of aminopeptidases in 3 different tumor cells. Since our previous study indicated that bestatin, an aminopeptidase inhibitor, was able to inhibit tumor-cell invasion, as well as aminopeptidase activities of murine and human metastatic tumor cells, cell-surface amino-peptidase N/CD13 may be partly involved in the activation mechanism for type-IV collagenolysis to achieve tumor-cell invasion, and anti-CD13 MAb WM15 may inhibit tumor-cell invasion through a mechanism involving its inhibitory action on the aminopeptidase N in tumor cells.

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The Mycobacterium bovis bacillus Calmette-Guérin (BCG) cell wall skeleton (CWS) consists of mycolic acids, arabinogalactan, and peptidoglycan (PGN) and activates Toll-like receptor 2 (TLR2) and TLR4. Here we investigated the ability of the essential portion of highly purified BCG CWS to support the TLR agonist function by using the following criteria: myeloid dendritic cell (DC) maturation, i.e., tumor necrosis factor alpha (TNF-␣) production and CD83/CD86 up-regulation. The purified PGN region was sufficient to activate TLR2 and TLR4 in mouse DCs and macrophages; in TLR2 and TLR4 double-knockout cells the BCG PGN-mediated TNF-␣ production ability was completely impaired. Likewise, stimulation with BCG CWS of HEK293 cells expressing either human TLR2 or TLR4, MD-2, and CD14 resulted in NF-B activation as determined by a reporter assay. Notably, specific blockers of extracellular human TLR2 (an original cocktail of monoclonal antibodies TLR2.45 and TH2.1) and TLR4 (E5531) inhibited BCG CWS-mediated NF-B activation by 80%. Using this human TLR blocking system, we tested whether human myeloid DC maturation was TLR2 and TLR4 dependent. BCG PGN-mediated DC maturation was blocked by 70% by suppression of both TLR2 and TLR4 and by 30 to 40% by suppression of either of these TLRs. Similar but less profound suppression of BCG CWS-mediated DC maturation was observed. Hence, the presence of BCG PGN is a minimal requirement for activation of both TLR2 and TLR4 in human DCs, unlike the presence of PGNs of gram-positive bacteria, which activate only TLR2. Unexpectedly, however, BCG PGN, unlike BCG CWS, barely activated NF-B in HEK293 cells coexpressing TLR2 plus TLR1, TLR2 plus TLR4, TLR2 plus TLR6, or TLR2 plus TLR10, suggesting that PGN receptors other than TLR2 and TLR4 present on human DCs but not on HEK293 cells are involved in TLR signaling for DC activation.Phagocytosis of Mycobacterium tuberculosis by antigen-presenting cells is usually accompanied by activation of the transcription factor NF-B, secretion of inflammatory and initial cytokines, release of the reactive nitrites, including NO, and secretion of several chemokines (9, 16). These responses involve the outputs of the signaling of pattern recognition receptors for microbes (16, 34). More than 10 members of the mammalian Toll-like receptor (TLR) family in the innate immune system have been identified as representatives of such receptors that primarily respond to microbial constituents to elicit the immune response in macrophages and dendritic cells (DCs) (25,34). M. tuberculosis-mediated adjuvant activity may be expressed through TLRs on DCs.Two of the human TLRs, TLR2 and TLR4, are involved in M. tuberculosis-mediated intracellular signaling in vitro (22,41). Means et al. (22) demonstrated that viable M. tuberculosis bacilli contain distinct ligands that activate cells via TLR2 and TLR4, while heat-killed M. tuberculosis fails to activate cells via TLR4. Several purified mycobacterial ligands have now been identified as TLR2 agonists. Underhill et al. (43) ...