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Advances in Brief |
Departments of Surgery and Medicine, McGill University Health Center, Royal Victoria Hospital, Montreal, Quebec, H3A 1A4 Canada [A-M. K., L. F., P. B.], and ISIS Pharmaceuticals, Carlsbad Research Center, Carlsbad, California 92008 [E. W., B. M.]
| ABSTRACT |
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| Introduction |
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(6)
. These cells express type 1 (TNFR60) and type 2 (TNFR80) TNF receptors, but the former is thought to be the major form involved in soluble TNF
-induced cellular responses (7
, 8)
. Signaling through this receptor appears to involve activation of the p42 ERK, p38 MAPK, and p54 JNK pathways (8
, 9)
as well as NF
B activation (10)
and may depend on cooperative signaling between these pathways. Recent studies have implicated the Ras and Raf kinases that act upstream of the MAPK pathway in transcriptional activation of E-selectin, an activity that may be secondary to a TNF
-induced increase in ceramide production (8
, 9)
.
Previously, we have shown that highly metastatic cells entering the liver can rapidly induce a cytokine cascade involving activation of TNF
production, and this leads to up-regulation of hepatic sinusoidal endothelial E-selectin expression and subsequently of ICAM-1 and VCAM-1 (11)
. Using an E-selectin-specific monoclonal antibody, we have also shown that E-selectin is involved in metastases formation in this organ (12)
. Here, we asked whether a blockade of tumor-induced endothelial E-selectin expression could inhibit liver metastases formation. Previously, it was shown that suppression of C-raf kinase in microvascular endothelial cells using an ASO approach was effective in preventing cytokine-mediated up-regulation of cell adhesion molecules, including E-selectin, and the efficacy of this approach in vivo was demonstrated in a rat heart allograft survival model (13
, 14)
. To block E-selectin expression in vivo, we, therefore, used rodent-specific C-raf kinase ASO. We show here that the ASO blocked adhesion of human colorectal carcinoma CX-1 cells to murine hepatic endothelial cells and inhibited experimental liver metastasis.
| Materials and Methods |
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Cell Lines.
Human colorectal carcinoma lines CX-1 (highly metastatic) and MIP-101 (poorly metastatic) were developed from two colon carcinoma biopsies (15)
and were a kind gift from Dr. Peter Thomas (Boston University School of Medicine, Boston, MA). The cells were maintained in RPMI medium containing 10% fetal bovine serum, 100 µg/ml penicillin, 100 µg/ml streptomycin, and 300 µg/ml of glutamine. Routine testing confirmed that the cells were free of Mycoplasma and viral contaminants during the study period.
Reagents.
Rat and mouse C-raf antisense (C-raf ASO; ISIS 15770-10) and a combinatorial mixture of oligonucleotide sequences made of the same chemistry as ISIS 15770 (ISIS 29848-5, control oligo; Ref. 14
) were provided by ISIS Pharmaceuticals (Carlsbad, CA). They were prepared in saline at the desired concentration, before use in the in vitro and in vivo experiments. Recombinant human TNF
was from R&D Systems (Minneapolis, MN). Induction of murine hepatic endothelial cell E-selectin expression by this cytokine was documented previously (11)
. Na51Cr came from Perkins Elmer Life Sciences (Boston, MA).
MTT Assay.
Cell proliferation was measured by the MTT assay as was described previously (16)
. Cells were seeded in 24-well plates at a density of 5 x 104 cells/well and cultured overnight in RPMI containing 10% serum before the addition of the oligonucleotides and incubation for up to 3 days.
Tumor-Endothelial Cell Adhesion Assay.
Liver sinusoidal endothelial cells (LSEC) were obtained from normal C57Bl/6 mice by liver perfusion as we described previously (12)
. Adhesion assays were performed using Na51Cr-labeled tumor and TNF
-treated endothelial cells (12)
. To test the effect of C-raf ASOs on tumor-endothelial cell adhesion, the endothelial cells were cultured for 5 days, and the culture medium was removed and replaced with Opti-Mem medium containing 3 µl of LipofectAMINE (both from Life Technologies, Inc., Burlington, Ont.) with or without different concentrations of the oligonucleotides and incubated for 5 h at 37°C. The medium was aspirated and was replaced with RPMI (10% FCS), and the cells were incubated for 48 h before the adhesion assay.
RNA Extraction, Northern Blot Analysis, and RT-PCR.
RNA extraction from liver specimens, RT-PCR, and the cytokine and E-selectin primers were described in detail elsewhere (11)
. To determine the effect of oligonucleotide treatment on tumor-induced E-selectin expression, nude or C57Bl/6 mice received injections i.v. of 25 mg/kg oligonucleotides 24 and 4 h before the intrasplenic/portal injection of 2 x 106 CX-1 cells. The livers were removed 4 h after tumor injections, and the RNA was extracted and analyzed using the murine-specific primers; the conditions were described in detail previously (11)
. Real time RT-PCR was also performed on the extracted RNA as described previously (17)
. Briefly, a primer/probe set for mouse E-selectin (forward primer: 5'-GGCAAATTCAACGGCACAGT-3'; reverse primer: 5'-GGGTCTCGCTCCTGGAAGAT-3'; probe: 5'-Fam-AAGGCCGAGAATGGGAAGCTTGTCATC-Tamra-3') was used on an ABI Prism 7700 (Applied Biosystems) and the resulting data analyzed by the ABI Sequence Detector v1.7a software. Mouse E-selectin was normalized to mouse GAPDH run concurrently on the Prism7700. For analysis of E-selectin induction in vitro, cultured endothelial cells were incubated for 4 h with 200 nM oligonucleotides in Opti-Mem, washed, and maintained in RPMI supplemented with 10% serum for 48 h. Two h before RNA extraction, 50 ng/ml TNF
were added for E-selectin induction (12)
. In all of these analyses, RT-PCR products were obtained and analyzed during the exponential portion of the amplification curve as was determined in preliminary studies (11)
.
Liver Metastasis Assay.
Experimental liver metastases were generated by intrasplenic/portal injection of tumor cells, as we described previously (16)
. The mice were inoculated with 2 x 106 CX-1 cells and splenectomized 1 min later. They were killed 46 weeks later, and liver metastases were enumerated immediately, without prior fixation. The oligonucleotide treatment consisted of two injections of 25 and 6 mg/kg antisense (or control) oligonucleotides 24 h and 4 h, respectively, before tumor cells injection, one injection of 6 mg/kg oligonucleotides 4 h later, and weekly injections of 25 mg/kg oligonucleotides from day 3 onward until the end of the experiment. An additional control group was given injections with vehicle (saline) only. All of the ASO and saline injections were administered i.v. (tail vein).
| Results |
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activated Hepatic Sinusoidal Endothelial Cells Is Blocked by Pretreatment with Murine C-raf ASOs.
-activated murine hepatic sinusoidal endothelial cells in an E-selectin-dependent manner (11)
. Because C-raf was implicated in the regulation of TNF
-dependent E-selectin induction, we investigated whether pretreatment of the endothelial cells with C-raf ASO can inhibit TNF
-dependent E-selectin expression and CX-1 adhesion. Hepatic endothelial cells were treated with different concentrations of C-raf ASO for 4 h, cultured for an additional 48 h, and then stimulated with 50 ng/ml TNF
for 5 additional hr to induce E-selectin. In these cells, C-raf and E-selectin expression as determined by RT-PCR after the 5-h incubation with TNF
were reduced by up to 4.6-fold (Fig. 1A)
-induced E-selectin expression was reduced in an ASO dose-dependent manner and abolished at a concentration of 100 nM (Fig. 1C)
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(Fig. 2A)
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| Discussion |
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In addition to the Ras/Raf/MAPK pathway, other signaling mechanisms involving the p38 MAPK and NF
B were implicated in E-selectin induction by TNF
(10)
. Previous results have shown that, whereas ERK and JNK activation by TNF
was blocked in cells treated with C-raf ASOs, p38 MAPK activity was unaffected (13)
. The results imply, therefore, that in hepatic endothelial cells, the inhibition of Raf signaling was sufficient to inhibit E-selectin induction. It should also be noted in this context that the Ras/Raf/MAPK pathway was also implicated in the regulation of outside-in signaling by ligand-activated E-selectin (19)
. A reduction in C-raf expression in hepatic endothelial cells in vivo may, therefore, have the dual effect of reducing E-selectin expression levels on one hand, and inhibiting the transmission of the E-selectin signal required for tumor cell transmigration and metastasis, on the other (20)
. The inhibition of other TNF
-dependent mechanisms such as the production of proangiogenic factors may also contribute to reduced metastases formation in the treated mice (21)
. Consistent with our findings is a recent report that Cimetidine, a histamine type 2 receptor (H2R) antagonist, known to improve the survival of colorectal cancer patients, blocks colorectal carcinoma HT-29 cell adhesion to human umbilical vascular endothelial cell and liver metastasis in nude mice by preventing E-selectin induction (22
, 23)
.
We recently identified the Kupffer cells as the main source of hepatic TNF
in response to inoculation of murine carcinoma H-59 cells.5
Other studies have shown that Kupffer cells can be activated to release cytokines by colon carcinoma cell-derived carcinoembryonic antigen, and this may be the mechanism of activation by the CX-1 cells (24
, 25)
. Although the C-raf/MAPK pathway was previously implicated in TNF
production by lipopolysaccharide-activated monocytes and macrophages (26)
, we found that C-raf ASO treatment reduced hepatic TNF
mRNA levels by only 25% relative to controls and did not alter IL-1ß levels (data not shown). This suggests that, in the present model, the main impact of the treatment was the inhibition of E-selectin expression, whereas the reduction in TNF
levels may have played an additional, more minor role.
In a previous study, we have shown that tumor cell-induced E-selectin expression was followed 68 h later by the appearance of ICAM-1 and VCAM-1, but not by platelet/endothelial cell adhesion molecule (PECAM) mRNA transcripts (11) . Treatment with C-raf ASO was shown elsewhere to have only a minor effect on ICAM-1 expression (13) . However, we cannot rule out the possibility that, in our model, VCAM-1 expression was also affected, possibly because of a combined effect of the ASO treatment and the inhibition of E-selectin mediated adhesion (5) . This may also have contributed to the reduction in metastasis.
In addition to up-regulation of vascular endothelial cell adhesion receptors, the host inflammatory response can facilitate the process of metastasis by other mechanisms including the induction of proangiogenic factors and the release or activation of extracellular matrix-degrading enzymes (21
, 27)
. The present study suggests that effective inhibition of TNF
-induced responses during the very early stages of metastasis can block disease progression. Taken together with other reports, they provide a rationale for developing reagents that target the host inflammatory response for antimetastatic therapy.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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1 Supported by a Canadian Institute for Health Research grant (to P. B.). ![]()
2 Present address: IRCM, 110 Pine Avenue West, Montreal, Quebec, Canada H2W 1R7. ![]()
3 To whom requests for reprints should be addressed, at Division of Surgical Research, McGill University Health Center, Royal Victoria Hospital, Room H6.25, 687 Pine Avenue West, Montreal, Quebec, Canada H3A 1A1. Phone: (514) 842-1231, extension 6692; Fax: (514) 843-1411; E-mail: pnina.brodt{at}muhc.mcgill.ca ![]()
4 The abbreviations used are: IL, interleukin; ASO, antisense oligonucleotide; TNF, tumor necrosis factor; MAPK, mitogen-activated protein kinase; ERK, extracellular signal-regulated protein kinase; JNK, c-Jun NH2-terminal protein kinase; NF
B, nuclear factor
B; ICAM, intercellular adhesion molecule; VCAM, vascular cell adhesion molecule; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; RT-PCR, reverse transcription-PCR; GAPDH, glyceraldehyde-3-phosphate dehydrogenase. ![]()
5 Abdel-Majid Khatib, Maria Kontogiannea, Lucia Fallavollita, Sarkis Meterissian. Bruce Jamison, Danuta Radzioch, and Pnina Brodt. Increased production of inflammatory cytokines by Kupffer cells in response to metastatic tumor cells, manuscript in preparation. ![]()
Received 6/ 7/02. Accepted 8/14/02.
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P. Auguste, L. Fallavollita, N. Wang, J. Burnier, A. Bikfalvi, and P. Brodt The Host Inflammatory Response Promotes Liver Metastasis by Increasing Tumor Cell Arrest and Extravasation Am. J. Pathol., May 1, 2007; 170(5): 1781 - 1792. [Abstract] [Full Text] [PDF] |
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N. Wang, T. Thuraisingam, L. Fallavollita, A. Ding, D. Radzioch, and P. Brodt The Secretory Leukocyte Protease Inhibitor Is a Type 1 Insulin-Like Growth Factor Receptor-Regulated Protein that Protects against Liver Metastasis by Attenuating the Host Proinflammatory Response. Cancer Res., March 15, 2006; 66(6): 3062 - 3070. [Abstract] [Full Text] [PDF] |
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A.-M. Khatib, P. Auguste, L. Fallavollita, N. Wang, A. Samani, M. Kontogiannea, S. Meterissian, and P. Brodt Characterization of the Host Proinflammatory Response to Tumor Cells during the Initial Stages of Liver Metastasis Am. J. Pathol., September 1, 2005; 167(3): 749 - 759. [Abstract] [Full Text] [PDF] |
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J. B. Kruskal, P. Thomas, R. A. Kane, and S. N. Goldberg Hepatic Perfusion Changes in Mice Livers with Developing Colorectal Cancer Metastases Radiology, May 1, 2004; 231(2): 482 - 490. [Abstract] [Full Text] [PDF] |
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W. Choi, S. Y. Eum, Y. W. Lee, B. Hennig, L. W. Robertson, and M. Toborek PCB 104-Induced Proinflammatory Reactions in Human Vascular Endothelial Cells: Relationship to Cancer Metastasis and Atherogenesis Toxicol. Sci., September 1, 2003; 75(1): 47 - 56. [Abstract] [Full Text] [PDF] |
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