Metastasis Of Colon Carcinoma Cells Research Articles

Indoleamine 2, 3-Dioxygenase 1 and CD8 Expression Profiling Revealed an Immunological Subtype of Colon Cancer With a Poor Prognosis.

BackgroundThe Immunoscore method, based on the distribution of the quantification of cytotoxic and memory T cells, provides an indicator of tumor recurrence for colon cancer. However, recent evidence has suggested that immune checkpoint expression represents a surrogate measure of tumor-infiltrating T cell exhaustion, and therefore may serve as a more accurate prognostic biomarker for colon cancer. Indoleamine 2, 3-dioxygenase 1 (IDO1), a potent immunosuppressive molecule, has been strongly associated with T-cell infiltration, but it lacks universal prognostic significance among all of the cancer subtypes. Our aim was to elucidate the prognostic significance of the combination of IDO1 and CD8A expression in colon cancer.MethodsGene expression and clinical survival data were analyzed using The Cancer Genome Atlas (TCGA) data set and validated using NCBI Gene Expression Omnibus (NCBI-GEO) cohort. Hierarchical clustering, functional enrichment analyses, and immune infiltration analysis were applied to evaluate the distinctive immune statuses in colon cancer risk subgroups stratified by IDO1 and CD8A expression. Moreover, Multivariate Cox regression analysis and Receiver Operating Characteristic (ROC) analyses were conducted to determine the prognostic value of IDO1/CD8A stratification. The IDO1/CD8A classifier may be suitable for use in the prediction of cancer development. It was validated via an in vivo murine model.ResultsThe stratification analysis demonstrated that the colon cancer subtype with the CD8AhighIDO1high* tumor resulted in the worst survival despite high levels of CD8 infiltrates. Its poor prognosis was associated with high levels of immune response, checkpoint genes, and Th1/IFN-γ gene signatures, regardless of CMS classification. Moreover, the IDO1/CD8A stratification was identified as an independent prognostic factor of overall survival (OS) and a useful predictive biomarker in colon cancer. In vivo data revealed the CD8AhighIDO1high group showed strong correlations with late-stage metastasis of colon carcinoma cells and upregulation of immune checkpoints.ConclusionsThe findings indicate that the proposed IDO1/CD8A stratification has exact and independent prognostic implications beyond CD8 T cell alone and CMS classification. As a result, it may represent a promising tool for risk stratification in colon cancer and improve the development of immunotherapies for patients with colon cancer in the future.

ARHGAP10 Inhibits the Proliferation and Metastasis of CRC Cells via Blocking the Activity of RhoA/AKT Signaling Pathway.

IntroductionARHGAP10 belongs to the ARHGAP family, which is downregulated in certain human tumors. However, the detailed function of ARHGAP10 remains unclear in human colon carcinoma (CRC). In the current study, we aimed to explore the role of ARHGAP10 in the growth and metastasis of CRC cells.MethodsARHGAP10 was induced silencing and overexpression using RNA interference (RNAi) and lentiviral-vector in CRC cells. Quantitative real-time PCR (qRT-PCR) and Western blot were used to quantify the mRNA and protein contents of ARHGAP10. Cell proliferation was determined by using Cell counting kit-8 (CCK-8). Transwell assay was utilized to examine the role of ARHGAP10 in the migration and invasion of CRC cells.ResultsOur results indicated that ARHGAP10 was downregulated in human CRC tissues and low expression of ARHGAP10 was associated with poor prognosis of patients with CRC. Moreover, ARHGAP10 overexpression significantly inhibited the proliferation and metastasis of CRC cells. Moreover, a PI3K/AKT inhibitor LY294002 was utilized to examine the connection between ARHGAP10 and AKT. Our findings demonstrated that the AKT inhibitor LY294002 could rescue the function of ARHGAP10 in CRC cells.DiscussionIt was the first time to elucidate that AKT involved in the ARHGAP10 signaling pathway and ARHGAP10 negatively mediated the phosphorylation of AKT (p-AKT) and RhoA activity in CRC cells. Interestingly, the Rho/MRTF/SRF inhibitor CCG-1423 significantly inhibited the phosphorylation of AKT in ARHGAP10 siRNA transfected CRC cells. Much importantly, overexpression of ARHGAP10 deeply suppressed the metastasis of CRC cells in the lung in vivo. Taken together, our findings not only enhanced the understanding of the anti-cancer effect of ARHGAP10 in CRC cells but also indicated its underlying pathway in CRC.

Forced Expression of CXCL10 Prevents Liver Metastasis of Colon Carcinoma Cells by the Recruitment of Natural Killer Cells

CXC chemokine ligand 10 (CXCL10) is a CXC chemokine family protein that transmits signals by binding to its specific receptor, CXCR3. CXCL10 is also known as an interferon-γ-inducible chemokine involved in various biological phenomena, including chemotaxis of natural killer (NK) cells and cytotoxic T lymphocytes, that suppress tumor growth and inhibition of angiogenesis. In this study, we examined the effects of forced expression of CXCL10 in a murine colon carcinoma cell line (CT26) on growth and metastasis in syngeneic mice. We first established CT26 cells that were stably expressing murine CXCL10 (CT26/CXCL10) and compared their growth with their parental CT26 cells in vitro and in vivo. The in vitro growth of the CT26/CXCL10 and CT26 cells was comparable, whereas the in vivo growth of the CT26/CXCL10 cells in the skin was strongly suppressed. Liver metastasis of the CT26/CXCL10 cells was also significantly suppressed after intra-splenic implantation. Removal of NK cells by the administration of anti-asialo GM1 antibody canceled the suppression of subcutaneous growth and liver metastasis of CT26/CXCL10 cells. Immunofluorescence clearly showed that abundant NKp46-positive NK cells were recruited into the liver metastatic lesions of the CT26/CXCL10 cells, consistent with specific NK cell migration towards the culture supernatant from the CT26/CXCL10 cells in the chemotaxis assay using transwells. These findings indicate that CXCL10 prevents in vivo growth and metastasis of colon carcinoma cells by recruiting NK cells, suggesting that forced expression of CXCL10 in the colon tumors by gene delivery should lead to a favorable clinical outcome.

Antimetastatic Activity of Gallic Acid‐conjugated Chitosan against Pulmonary Metastasis of Colon Carcinoma Cells

We synthesized gallic acid (GA)‐conjugated chitosan (abbreviated as chitogallate) to study its antitumor activity against CT26 mouse colorectal carcinoma cells. GA was conjugated with chitosan by aid of water‐soluble carbodiimide. Chitogallate nanoparticles were prepared by dialysis method, and these nanoparticles have spherical shapes with sizes ranged about 70–250 nm. Chitogallate nanoparticles have superior antioxidants activities as well as GA itself. At cytotoxicity study, GA showed dose‐dependent cytotoxicities against CCD986sk cells and CT26 cells while chitogallate nanoparticles were not significantly affected to the viability of cells. In Matrigel invasion assay, chitogallate nanoparticles have superior anti‐invasive capacity against cancer cells as well as GA itself, i.e., invasiveness of CT26 cells was decreased according to GA contents in chitogallate nanoparticles. Furthermore, gelatin zymography also showed that chitogallate nanoparticles having higher substitution degree of GA decreased matrix metalloproteinase‐2 activity. Chitogallate nanoparticles efficiently inhibited pulmonary metastasis of CT26 cells in animal pulmonary metastasis model. We prepared chitogallate nanoparticles for application as an anti‐invasive agent. Chitogallate nanoparticles were less toxic than GA itself and have superior anti‐invasive/antimetastatic activity. We suggest that chitogallate nanoparticles are promising candidate for inhibition of tumor invasion/metastasis.

Overexpression of gelsolin reduces the proliferation and invasion of colon carcinoma cells.

The enhanced motility of cancer cells via the remodeling of the actin cytoskeleton is crucial in the process of cancer cell invasion and metastasis. It was previously demonstrated that gelsolin (GSN) may be involved as a tumor or a metastasis suppressor, depending on the cell lines and model systems used. In the present study, the effect of GSN on the growth and invasion of human colon carcinoma (CC) cells was investigated using reverse transcription quantitative polymerase chain reaction and western blotting. It was observed that upregulation of the expression of GSN in human CC cells significantly reduced the invasiveness of these cells. The expression levels of GSN were observed to be reduced in CC cells, and the reduced expression level of GSN was often associated with a poorer metastasis-free survival rate in patients with CC (P=0.04). In addition, the overexpression of GSN inhibited the invasion of CC cells in vitro. Furthermore, GSN was observed to inhibit signal transducer and activator of transcription (STAT) 3 signaling in CC cells. Together, these results suggested that GSN is critical in regulating cytoskeletal events and inhibits the invasive and/or metastatic potential of CC cells. The results obtained in the present study may improve understanding of the functional and mechanistic links between GSN as a possible tumor suppressor and the STAT3 signaling pathway, with respect to the aggressive nature of CC. In addition, the present study demonstrated the importance of GSN in regulating the invasion and metastasis of CC cells at the molecular level, suggesting that GSN may be a potential predictor of prognosis and treatment success in CC.

ICAM-1 suppresses tumor metastasis by inhibiting macrophage M2 polarization through blockade of efferocytosis.

Efficient clearance of apoptotic cells (efferocytosis) can profoundly influence tumor-specific immunity. Tumor-associated macrophages are M2-polarized macrophages that promote key processes in tumor progression. Efferocytosis stimulates M2 macrophage polarization and contributes to cancer metastasis, but the signaling mechanism underlying this process is unclear. Intercellular cell adhesion molecule-1 (ICAM-1) is a transmembrane glycoprotein member of the immunoglobulin superfamily, which has been implicated in mediating cell–cell interaction and outside-in cell signaling during the immune response. We report that ICAM-1 expression is inversely associated with macrophage infiltration and the metastasis index in human colon tumors by combining Oncomine database analysis and immunohistochemistry for ICAM-1. Using a colon cancer liver metastasis model in ICAM-1-deficient (ICAM-1−/−) mice and their wild-type littermates, we found that loss of ICAM-1 accelerated liver metastasis of colon carcinoma cells. Moreover, ICAM-1 deficiency increased M2 macrophage polarization during tumor progression. We further demonstrated that ICAM-1 deficiency in macrophages led to promotion of efferocytosis of apoptotic tumor cells through activation of the phosphatidylinositol 3 kinase/Akt signaling pathway. More importantly, coculture of ICAM-1−/− macrophages with apoptotic cancer cells resulted in an increase of M2-like macrophages, which was blocked by an efferocytosis inhibitor. Our findings demonstrate a novel role for ICAM-1 in suppressing M2 macrophage polarization via downregulation of efferocytosis in the tumor microenvironment, thereby inhibiting metastatic tumor progression.

Tumor cell-activated CARD9 signaling contributes to metastasis-associated macrophage polarization.

Macrophages are critical immune effector cells of the tumor microenvironment that promote seeding, extravasation and persistent growth of tumor cells in primary tumors and metastatic sites. Tumor progression and metastasis are affected by dynamic changes in the specific phenotypes of macrophage subpopulations; however, the mechanisms by which tumor cells modulate macrophage polarization remain incompletely understood. Caspase recruitment domain-containing protein 9 (CARD9) is a central adaptor protein of innate immune responses to extracellular pathogens. We report that increased CARD9 expression is primarily localized in infiltrated macrophages and significantly associated with advanced histopathologic stage and the presence of metastasis. Using CARD9-deficient (CARD9−/−) mice, we show that bone marrow-derived CARD9 promotes liver metastasis of colon carcinoma cells. Mechanistic studies reveal that CARD9 contributes to tumor metastasis by promoting metastasis-associated macrophage polarization through activation of the nuclear factor-kappa B signaling pathway. We further demonstrate that tumor cell-secreted vascular endothelial growth factor facilitates spleen tyrosine kinase activation in macrophages, which is necessary for formation of the CARD9–B-cell lymphoma/leukemia 10–mucosa-associated lymphoid tissue lymphoma translocation protein 1 complex. Taken together, our results indicating that CARD9 is a regulator of metastasis-associated macrophages will lead to new insights into evolution of the microenvironments supporting tumor metastasis, thereby providing targets for anticancer therapies.

Expression of DIAPH1 is up‐regulated in colorectal cancer and its down‐regulation strongly reduces the metastatic capacity of colon carcinoma cells

In most cases, metastatic colorectal cancer is not curable, thus new approaches are necessary to identify novel targets for colorectal cancer therapy. Actin-binding-proteins (ABPs) directly regulate motility of metastasising tumor cells, and for cortactin an association with colon cancer metastasis has been already shown. However, as its depletion only incompletely inhibits metastasis, additional, more suitable cellular targets have to be identified. Here we analyzed expression of the ABPs, DIAPH1, VASP, N-WASP, and fascin in comparison with cortactin and found that, besides cortactin, DIAPH1 was expressed with the highest frequency (63%) in colorectal cancer. As well as cortactin, DIAPH1 was not detectable in normal colon tissue and expression of both proteins was positively correlated with metastasis of colorectal cancer. To analyse the mechanistic role of DIAPH1 for metastasis of colon carcinoma cells in comparison with cortactin, expression of the proteins was stably down-regulated in the human colon carcinoma cell lines HT-29, HROC-24 and HCT-116. Analysis of metastasis of colon carcinoma cells in SCID mice revealed that depletion of DIAPH1 reduced metastasis 60-fold and depletion of cortactin 16-fold as compared with control cells. Most likely the stronger effect of DIAPH1 depletion on colon cancer metastasis is due to the fact that in vitro knock down of DIAPH1 impaired all steps of metastasis; adhesion, invasion and migration while down-regulation of cortactin only reduced adhesion and invasion. This very strong reducing effect of DIAPH1 depletion on colon carcinoma cell metastasis makes the protein a promising therapeutic target for individualized colorectal cancer therapy.

MiR-21 and miR-31 Converge on TIAM1 to Regulate Migration and Invasion of Colon Carcinoma Cells

TGF-β promotes cell migration and invasion, an attribute that is linked to the pro-metastasis function of this cytokine in late stage cancers. The LIM 1863 colon carcinoma organoid undergoes epithelial-mesenchymal transition (EMT) in response to TGF-β. This process is markedly accelerated by TNF-α, and we found that the levels of miR-21 and miR-31 were prominently elevated under the synergistic actions of TGF-β/TNF-α. Consistent with this, overexpression of either miR-21 or miR-31 significantly enhanced the effect of TGF-β alone on LIM 1863 morphological changes. More importantly, transwell assays demonstrated the positive effects of both miR-21 and miR-31 in TGF-β regulation of LIM 1863 motility and invasiveness. Elevated levels of miR-21 and miR-31 also enhanced motility and invasiveness of other colon carcinoma cell lines. We present compelling evidence that TIAM1, a guanidine exchange factor of the Rac GTPase, is a direct target of both miR-21 and miR-31. Indeed in LIM 1863 cells, suppression of TIAM1 is required for miR-21/miR-31 to enhance cell migration and invasion. Therefore, we have uncovered miR-21 and miR-31 as downstream effectors of TGF-β in facilitating invasion and metastasis of colon carcinoma cells.

Inhibitory effects of tanshinone II-A on invasion and metastasis of human colon carcinoma cells

To investigate the effects and possible mechanisms of tanshinone II-A, an alcohol extract of the root of Salvia miltiorrhiza Bunge, on tumor invasion and metastasis of human colon carcinoma (CRC) cells. The effects of tanshinone II-A on invasion and metastasis of CRC cell lines HT29 and SW480 were evaluated by in vitro and in vivo assays. Western blotting was used to investigate possible molecular mechanisms of tanshinone II-A anti-cancer actions. Tanshinone II-A inhibited migration and invasion of CRC cells in a dose-dependent manner. The inhibitory effect also depended on time, with the most significant effects observed at 72 h. Tanshinone II-A also significantly inhibited in vivo metastasis of colon carcinoma SW480 cells. It inhibited in vitro and in vivo invasion and metastasis of CRC cells by reducing levels of urokinase plasminogen activator (uPA) and matrix metalloproteinases (MMP)-2 and MMP-9, and by increasing levels of tissue inhibitor of matrix metalloproteinase protein (TIMP)-1 and TIMP-2. Tanshinone II-A was also shown to suppress the nuclear factor-kappaB (NF-kappaB) signal. Tanshinone II-A inhibited in vitro and in vivo invasion and metastasis of CRC cells. The effect resulted from changes in the levels of uPA, MMP-2, MMP-9, TIMP-1 and TIMP-2, and apparent inhibition of the NF-kappaB signal transduction pathway.

Marked Therapeutic Effects of Hybrid Liposomes on the Hepatic Metastasis of Colon Carcinoma

Hybrid liposomes (HLs) composed of vesicular and micellar surfactants have inhibitory effects on the growth of tumor cells in vitro and in vivo. Successful clinical chemotherapy with drug-free HLs to patient with lymphoma has been reported after approval by the Committe of Bioethics. However, the therapeutic effects of HLs on the metastasis of colon carcinoma cells have not yet been elucidated. In this study, the therapeutic effects of HLs composed of L-alpha-dimyristoylphosphatidylcholine (DMPC) and polyoxyethylene (23) dodecyl ether [C(12)(EO)(23)] on the metastasis of colon carcinoma (Colon26) cells were examined in vivo. Marked high therapeutic effects were obtained in the hepatic metastasis mice model after the treatment with HLs. Furthermore, optical microscopic analysis indicated that HLs could induce the apoptosis of colon carcinoma cells in vivo. No toxicity was observed in the hepatic metastasis mice model after intravenously injecting HLs. Therapeutic effects along with the induction of apoptosis by HLs without any drugs on hepatic metastasis were revealed on the basis of optical microscopic analysis for the first time in vivo.

Differential effector mechanisms induced by vaccination with MUC1 DNA in the rejection of colon carcinoma growth at orthotopic sites and metastases

The effects of MUC1 DNA vaccination on the orthotopic growth and liver metastasis of colon carcinoma cells were investigated in mice. Vaccination with MUC1 DNA resulted in immune responses that were effective in suppressing mouse colon carcinoma cells transfected with MUC1 cDNA. CD4+ T cells but not CD8+ T cells mediated this antitumor response as shown by the in vivo depletion of lymphocyte subpopulations with the use of anti-CD4 or anti-CD8 antibody. The effects of neutralizing antibodies in vivo revealed that the predominant effector molecule in preventing orthotopic tumor growth was FasL, whereas the effector molecule effective in preventing liver metastasis was tumor necrosis factor-alpha. Colon carcinoma cells isolated from tumors growing in the ceca, spleens, and livers were shown to be equally sensitive to FasL and tumor necrosis factor-alpha. The results strongly suggest that elimination of tumor cells initiated by DNA vaccination in the present protocol is mediated by antigen-specific CD4+ T cells and the effector mechanisms in the cecum and in the liver are distinct due to a unique organ microenvironment.

625. Inhibition of Hepatic Metastasis of Colon Carcinoma Cells by RNA Interference-Mediated Suppression of HIF-1α in Tumor Cells and Hepatocytes

625. Inhibition of Hepatic Metastasis of Colon Carcinoma Cells by RNA Interference-Mediated Suppression of HIF-1α in Tumor Cells and Hepatocytes

Mouse Colon Carcinoma Cells Established for High Incidence of Experimental Hepatic Metastasis Exhibit Accelerated and Anchorage-Independent Growth

Highly metastatic variants of mouse colon 38 colon carcinoma cells were established by repeated selection in vivo for liver metastasis and designated as SL4 cells. The SL4 cells formed colonies in the liver of 100% of syngenic mice when injected intrasplenically, while the incidence of liver metastasis was 27% of mice injected with parental cells. The weight of livers, which is an indicator of experimental hepatic metastasis formation, was significantly higher after intrasplenic injection and subsequent splenoctomy with SL4 cells than colon 38 cells. The incidence of hepatic metastasis after intracecal injection of SL4 cells was significantly higher than that of colon 38 cells. The SL4 cells were tested in vitro for their properties. Differences were not detected in the motility and invasive behavior between colon 38 cells and SL4 cells. SL4 cells showed a higher proliferation rate than colon 38 cells under adherent conditions. SL4 cells maintained a capacity to proliferate under non-adherent conditions whereas parental cells did not. SL4 cells should be a useful tool to study the mechanism of hepatic metastasis of colon carcinoma cells and to develop methods to prevent hepatic metastasis.

Development of Cell-Specific Targeting Systems for Drugs and Genes

Cell-specific targeting systems for drugs and genes have been developed by using glycosylated macromolecule as a vehicle that can be selectively recognized by carbohydrate receptors. Pharmacokinetic analyses of the tissue distribution of glycosylated proteins came to the conclusion that the surface density of the sugar moiety on the protein derivative largely determines the binding affinity for the receptors and plasma lectin. Many glycosylated delivery systems have been developed and their usefulness investigated in various settings. Galactosylated polymers, when properly designed, were found to be effective in delivering prostaglandin E1 and other low-molecular-weight drugs selectively to hepatocytes. In addition, glycosylated superoxide dismutase and catalase were successfully developed with minimal loss of enzymatic activity. A simultaneous targeting of these two enzymes to liver nonparenchymal cells significantly prevented hepatic ischemia/reperfusion injury. On the other hand, galactosylated catalase, a derivative selectively delivered to hepatocytes, effectively inhibited hepatic metastasis of colon carcinoma cells in mice. Finally, hepatocyte-targeted in vivo gene transfer was achieved by synthesizing a multi-functional carrier molecule, which condenses plasmid DNA, delivering DNA to hepatocytes through recognition by asialoglycoprotein receptors, and releasing DNA from endosomes/lysosomes into cytoplasm.

Inhibition of experimental hepatic metastasis by targeted delivery of catalase in mice.

Bovine liver catalase derivatives possessing diverse tissue distribution properties were synthesized, and their effects on hepatic metastasis of colon carcinoma cells were examined in mice. An intraportal injection of 1 x 10(5) colon 26 cells resulted in the formation of more than 50 metastatic colonies on the surface of the liver at 14 days after injection. An intravenous injection of catalase (CAT; 35000 units/kg of body weight) significantly (P < 0.001) reduced the number of the colonies in the liver. Galactosylated (Gal-), mannosylated (Man-) and succinylated (Suc-) CAT were also tested in the same system. Of these derivatives, Gal-CAT showed the greatest inhibitory effect on hepatic metastasis, and the number of colonies was significantly (P < 0.001) smaller than following treatment with catalase. High activities of matrix metalloproteinases (MMPs), especially MMP-9, were detected in the liver of mice bearing metastatic tumor tissues, which was significantly (P < 0.05) reduced by Gal-CAT. These results, combined with our previous finding that Gal-CAT can be efficiently delivered to hepatocytes, indicate that the targeted delivery of catalase to the liver by galactosylation is a promising approach to suppress hepatic metastasis. Decreased MMP activity by catalase delivery seems to be involved in its anti-metastatic effect.

Inhibition of experimental pulmonary metastasis by controlling biodistribution of catalase in mice.

In a previous study, we showed that targeted delivery of bovine liver catalase to hepatocytes by direct galactosylation augmented the inhibitory effect of the enzyme on experimental hepatic metastasis of colon carcinoma cells (unpublished data). Here, we examined the ability of catalase to inhibit tumor metastasis to the lung by controlling its biodistribution. Four types of catalase derivative, Gal-CAT, Man-CAT, Suc-CAT and PEG-CAT, were synthesized. Experimental pulmonary metastasis was induced in mice by i.v. injection of 1 x 10(5) colon 26 tumor cells. An i.v. injection of catalase (35,000 units/kg) partially, but significantly, decreased the number of colonies in the lung 2 weeks after tumor injection, from 93 +/- 29 (saline injection) to 63 +/- 23 (p < 0.01). Suc-CAT, Man-CAT and Gal-CAT showed effects similar to those of catalase on the number of colonies. However, PEG-CAT greatly inhibited pulmonary metastasis to 22 +/- 11 (p < 0.001). Furthermore, s.c. injection of catalase also greatly inhibited metastasis (11 +/- 6, p < 0.001). Neither inactivated catalase nor BSA showed any effects on the number of metastatic colonies, indicating that the enzymatic activity of catalase to detoxify H(2)O(2) is the critical factor inhibiting metastasis. (111)In-PEG-CAT showed a sustained concentration in plasma, whereas s.c.-injected (111)In-catalase was slowly absorbed from the injection site. These results suggest that retention of catalase activity in the circulation is a promising approach to inhibit pulmonary metastasis.

Prevention of colon carcinogenesis and carcinoma metastasis by orally administered bovine lactoferrin in animals.

Bovine lactoferrin (bLF), a milk protein known to have bacteriostatic properties was examined for its preventive effects on colon and other organ carcinogenesis and experimental metastasis. (Experiment 1) The influence on colon carcinogenesis was investigated in male rats treated with azoxymethane (AOM), then received 2 or 0.2% bLF for 36 weeks. Significant reduction in the incidence (27% and 46% of the control, respectively) and number of adenocarcinomas of the large intestine was observed. (Experiment 2) In BALB/c mice bearing subcutaneous (s.c.) implants of colon carcinoma 26 (Co 26Lu). bLF demonstrated significant inhibition of spontaneous lung metastasis (approximately 43% of the control). Number of cytotoxic asialoGM1+ and CD8+ cells in white blood cells increased (171% and 122% of control, respectively) after treatment. Results of those experiments indicate that bLF remarkably prevents colon carcinogenesis and lung metastasis of colon carcinoma cells, possibly due to increasing cytotoxic cells in the peripheral blood.

Importance of hepatic first-pass removal in metastasis of colon carcinoma cells

Background/Aims: It might be thought that colon carcinoma tends to metastasize to the liver because tumor cells leaving the primary colon tumor pass initially through the liver. Therefore we elucidated the kinetics of tumor cells in the body in order to understand the effect of the location of the liver on hepatic metastasis, that is to examine the hepatic first-pass effect of tumor cells. Methods: Based on a physiological kinetic model, we examined quantitatively the hepatic metastasis and hepatic distribution of KM12-HX cells administered by different routes. Results: Both the number and incidence of colonies of hepatic metastasis were much greater after intrasplenic injection than after intravenous injection. The distribution of radioactivity to the liver after intrasplenic injection of [ 3H] thymidine-labeled cells was also much higher than that after intravenous injection. The number of colonies of hepatic metastasis correlated well with the area under the curve of the distributed amount of the tumor cells in the liver, regardless of the injection route; the correlation line was identical for each injection route. Conclusions: These results suggest that the hepatic first-pass effect is an important factor for the hepatic metastasis and that the cumulative number of tumor cells distributed in the liver is a determining factor for the degree of metastasis. Mathematical analysis based on a physiological model also suggests that hepatic metastasis depends on hepatic first-pass trapping of tumor cells.

Characterization of an animal model of metastatic colon carcinoma.

Although numerous animal tumor models have been used to study colon carcinoma, few display metastatic properties. We have characterized an animal tumor model that has 3 properties essential for the study of metastasis of colon carcinoma cells: epithelial cell origin; a reproducible pattern of metastatic behavior and the ability to be propagated both in vitro and in vivo to facilitate identification of biochemical correlates of metastasis. The KI2/TR cell line was derived from a transplantable colon carcinoma induced by dimethylhydrazine in the BD‐IX rat strain. Transmission electron microscopy of KI2/TR cells demonstrated junctional complexes, desmosomes and surface microvilli characteristic of gastrointestinal epithelial cells. The epithelial cell origin of KI2/TR was confirmed by demonstrating the presence of keratin, a marker of epithelial cells, but not vimentin, a constituent of mesenchymal cells. Secretion of CEA and Ca19‐9 antigens by KI2/TR cells in vitro was below the sensitivity of the assays (1 ng/ml and 6 U/ml respectively). KI2/TR cells produced tumors following s.c. injection into syngeneic BD‐IX rats, allogeneic RNU/rnuDF rats and xenogeneic CRL:nu/nuBR mice. Macroscopic lung metastases were observed in animals from all 3 groups. Distal lymph node metastases were more frequent in BD‐IX rats than in nude rats or mice. The histological appearances of all tumors and metastases were similar, showing a moderate to poorly differentiated glandular carcinoma. Intrasplenic injections of KI2/TR cells in nude mice resulted in liver colonization. Preferential growth of tumor cells at sites of trauma was also observed. The results show that the KI2/TR system can be used as a model to study metastasis of colon carcinoma cells and may find utility in the testing of chemotherapeutic agents against metastatic lesions.